Abstract

The management of failed autologous chondrocyte implantation (ACI) and matrix-assisted autologous chondrocyte implantation (MACI) for the treatment of symptomatic osteochondral defects in the knee represents a major challenge. Patients are young, active and usually unsuitable for prosthetic replacement. This study reports the results in patients who underwent revision cartilage transplantation of their original ACI/MACI graft for clinical or graft-related failure. We assessed 22 patients (12 men and 10 women) with a mean age of 37.4 years (18 to 48) at a mean of 5.4 years (1.3 to 10.9). The mean period between primary and revision grafting was 46.1 months (7 to 89). The mean defect size was 446.6 mm² (150 to 875) and they were located on 11 medial and two lateral femoral condyles, eight patellae and one trochlea.

The mean modified Cincinnati knee score improved from 40.5 (16 to 77) pre-operatively to 64.9 (8 to 94) at their most recent review (p < 0.001). The visual analogue pain score improved from 6.1 (3 to 9) to 4.7 (0 to 10) (p = 0.042). A total of 14 patients (63%) reported an ‘excellent’ (n = 6) or ‘good’ (n = 8) clinical outcome, 5 ‘fair’ and one ‘poor’ outcome. Two patients underwent patellofemoral joint replacement. This study demonstrates that revision cartilage transplantation after primary ACI and MACI can yield acceptable functional results and continue to preserve the joint.

Cite this article: Bone Joint J 2014;96-B:54–8.

The Royal National Orthopaedic Hospital has completed an extensive trial of ACI versus MACI in the treatment of symptomatic osteochondral defects of the knee. A new technique has now been proposed which is quicker and easier to perform. This is the Gel-Type Autologous Chondrocyte Transplantation, CHONDRONTM. At Stanmore CHONDRON has been used for the past 17 months. Our aim was to assess the short term functional outcome of patients who have undergone CHONDRONTM using validated outcome scoring questionnaires. We retrospectively reviewed the notes of 43 patients that had undergone CHONDRONTM over one year ago and scored them using the Modified Cincinnati Score, the Visual Analogue Score and the Benltey Stanmore Functional Rating Score.

We analysed whether a high body mass index (BMI) had a deleterious effect on outcome following autologous chondrocyte implantation (ACI) or matrix-carried autologous chondrocyte implantation (MACI) for the treatment of full-thickness chondral defects of the knee from a subset of patients enrolled in the ACI vs MACI trial at The Royal National Orthopaedic Hospital.

The mean Modified Cincinnati scores (MCS) were significantly higher (p < 0.001) post-operatively in patients who had an ideal body weight (n = 53; 20 to 24.9 kg/m²) than in overweight (n = 63; 25 to 30 kg/m²) and obese patients (n = 22; > 30 kg/m²). At a follow-up of two years, obese patients demonstrated no sustained improvement in the MCS. Patients with an ideal weight experienced significant improvements as early as six months after surgery (p = 0.007). In total, 82% of patients (31 of 38) in the ideal group had a good or excellent result, compared with 49% (22 of 45) of the overweight and 5.5% (one of 18) in the obese group (p < 0.001). There was a significant negative relationship between BMI and the MCS 24 months after surgery (r = -0.4, p = 0.001).

This study demonstrates that obese patients have worse knee function before surgery and experience no sustained benefit from ACI or MACI at two years after surgery. There was a correlation between increasing BMI and a lower MCS according to a linear regression analysis. On the basis of our findings patient selection can be more appropriately targeted.

Chondral injuries of the knee are extremely common and present a unique therapeutic challenge due to the poor intrinsic healing of articular cartilage. These injuries can lead to significant functional impairment. There are several treatment modalities for articular osteochondral defects, one of which is autologous chondrocyte implantation. Our study evaluates the mid to long term functional outcomes in a cohort of 828 patients who have undergone an autologous chondrocyte implantation procedure (either ACI or MACI), identifying retrospectively factors that may influence their outcome.

The influence of factors including age, sex, presence of osteoarthritis and size and site of lesion have been assessed individually and with multivariate analysis. All patients were assessed using the Bentley Functional Score, Visual Analogue Score and the Cincinnati Functional Score. Assessment were performed pre-operatively and of their status in 2010.

The longest follow-up was 12 years (range 24 to 153 months) with a mean age of 34 years at time of procedure. The mean defect size was 409 mm² (range 64 to 2075 mm²). The distribution of lesions was 51% Medial Femoral Condyle, 12.5% Lateral Femoral Condyle, 18% Patella (single facet), 5% Patella (Multifacet) and 6% Trochlea. 4% had cartilage transplant to multiple sites.

High failure rates were noted in those with previous cartilage regenerative procedures or evidence of early osteoarthritis and those with transplantation to multiple sites.

Autologous chondrocyte implantation is an effective method of decreasing pain and increasing function, however patient selection plays clear role in the success of such procedure.

Chondral injuries of the knee are extremely common and present a unique therapeutic challenge due to the poor intrinsic healing of articular cartilage. These injuries can lead to significant functional impairment. There are several treatment modalities for articular osteochondral defects, one of which is autologous chondrocyte implantation. Our study evaluates the mid to long term functional outcomes in a cohort of 828 patients who have undergone an autologous chondrocyte implantation procedure (either ACI or MACI), identifying retrospectively factors that may influence their outcome.

The influence of factors including age, sex, presence of osteoarthritis and size and site of lesion have been assessed individually and with multivariate analysis. All patients were assessed using the Bentley Functional Score, Visual Analogue Score and the Cincinnati Functional Score. Assessment were performed pre-operatively and of their status in 2010. The majority of patients had several interim scores performed at varying intervals.

The longest follow-up was 12 years (range 24 to 153 months) with a mean age of 34 years at time of procedure. The mean defect size was 486 mm2 (range 64 to 2075 mm2). The distribution of lesions was 51% Medial Femoral Condyle, 12.5% Lateral Femoral Condyle, 18% Patella (single facet), 5% Patella (Multifacet) and 6% Trochlea. 4% had cartilage transplant to multiple sites. 30% failed following this procedure at a mean time of 72 months. 52% patients stated a marked improvement in their functional outcomes within the first two years. 49% stated an excellent result following their procedure.

High failure rate was noted in those with previous cartilage regenerative procedures, transplants occurring on the patella, particularly if involving multifacets. Multiple site cartilage transplantation was also associated with a high failure rate.

Autologous chondrocyte implantation is an effective method of decreasing pain and increasing function, however patient selection plays clear role in the success of such procedure.

The aim of this study was to determine whether the clinical outcome of autologous chondrocyte transplantation was dependent on the timing of a high tibial osteotomy in tibio-femoral mal-aligned knees. Between 2000 and 2005, forty-eight patients underwent autologous chondrocyte implantation with HTO performed at varying times relative to the second stage autologous chondrocyte implantation procedure. 24 patients had HTO performed simultaneously with their second stage cartilage transplantation, (the HTO Simultaneous Group). 5 patients had HTO prior to their cartilage procedure, (the HTO pre-ACI Group) and 19 had HTO performed between 1 to 4 years after their second stage cartilage implantation, (the HTO post-ACI Group). There were 29 men and 19 women with a mean age of 37 years (Range 28 to 50) at the time of their second stage procedure.

With average follow-up of 72 months we have demonstrated a significant functional benefit in performing the HTO either prior to or simultaneously with the ACI procedure in the mal-aligned knee. The failure rate in the Post-ACI group was 45% compared to the Pre-ACI and Simultaneous group, with failure rates of 20% and 25%, respectively.

An HTO performed prior to or simultaneously with an autologous chondrocyte implantation procedure in the mal-aligned knee, provides a significant protective effect by reducing the failure rate by approximately 50%.

Introduction

Autologous chondrocyte implantation (ACI) is contra-indicated in a joint rendered unstable by a ruptured anterior cruciate ligament (ACL). We present our experience of ACI repair with ACL reconstruction

Articular cartilage implantation (ACI) and associated procedures (MACI = Matrix-assisted cartilage implantation) are now established treatments for osteochondral defects in the knee. The quality of repair in terms of histological appearance is frequently not known, whilst the correlation of histology results with functional outcomes remains undefined. Histological data of the quality of the repair tissue is sparse and a precise classification proved difficult.

This was a single-centre, prospective study. Over 12 years (1998-2010) 406 patients that underwent articular cartilage implantation procedures at our institution (ACI = 170, MACI = 205) had biopsies taken at the 1-2 year interval, in order to assess whether these contained ‘hyaline-like’ cartilage, ‘mixed hyaline-like with fibrocartilage’, fibrocartilage or fibrous tissue alone.

Histological sections of the biopsies were prepared and stained with haematoxylin, eosin and proteoglycan stains and viewed under polarised light. All biopsies were studied by a single histopathologist in a specialist, dedicated musculoskeletal laboratory.

All patients were assessed by the Cincinnati, Bentley and Visual Analogue scores both pre-operatively and at the time of the review.

The findings revealed that 56 patients healed with ‘hyaline-like’ cartilage (14.9%), 103 with ‘mixed’ (27.5%), 179 with fibrocartilage (47.7%) and 37 with fibrous tissue (9.9%).

These findings showed that 42.4% of defects were filled with ‘hyaline-like’ or ‘mixed’ cartilage, with 70% of these achieving a ‘fair’ to ‘excellent’ functional outcome. This was also observed in the fibrocartilage group, where 72% achieved similar results. Predictably 89% of the patients that healed by fibrous tissue had a poor functional outcome.

This study shows that 71% of patients whose osteochondral defects healed by either ‘hyaline-like’, ‘mixed’ or fibrocartilage experienced an improvement in the function. In contrast, only 11% of the patients whose defects filled with fibrous tissue, showed some functional improvement. Additionally, this data indicates the advantage of biopsies in assessing the overall results of cartilage implantation procedures.

Patients with osteochondrodysplasia frequently require Total Hip Arthroplasty at a younger age, as a result of early degenerative disease of the hip joint. The outcome of Modular Total Hip Arthroplasty in this group of patients has been reported previously. In this retrospective study we evaluated the outcome of custom made (CADCAM) Total Hip Arthroplasty in patients with osteochondrodysplasia.

Between 1974 and 2009, twenty one CADCAM Total Hip Arthroplasty procedures were performed in fourteen patients in our institution. There were eight female and six male patients, with the mean age at time of surgery of 40.95 years (20 to 78). The patients were followed up clinically and with the Harris hip score for a mean of 7.12 years (0.5 to 17 years).

Four of the twenty-one hips (23.8%) required revision surgery at a mean of 11.54 years (6.5 to 17 years); one required it for aseptic loosening of the femoral component; one required complete revision of the acetabular component; one required exchange of acetabular liner; and one was for symptomatic non-union of a lesser trochanter avulsion.

This study shows encouraging clinical outcomes of custom made (CADCAM) Total Hip Arthroplasty in patients with osteochondrodysplasia,

Purpose

The rate of arthroplasty or osteotomy in patients who had undergone autologous chondrocyte implantation (ACI) for osteochondral defects in the knee was determined. Furthermore, we investigated whether any radiographic evidence of osteoarthritis (OA) prior to ACI was associated with poorer outcome following surgery.

Autologous chondrocyte implantation (ACI) and mosaicplasty are methods of treating symptomatic articular cartilage defects in the knee. This study represents the first long-term randomised comparison of the two techniques in 100 patients at a minimum follow-up of ten years. The mean age of the patients at the time of surgery was 31.3 years (16 to 49); the mean duration of symptoms pre-operatively was 7.2 years (9 months to 20 years). The lesions were large with the mean size for the ACI group being 440.9 mm² (100 to 1050) and the mosaicplasty group being 399.6 mm² (100 to 2000). Patients had a mean of 1.5 previous operations (0 to 4) to the articular cartilage defect. Patients were assessed using the modified Cincinnati knee score and the Stanmore-Bentley Functional Rating system. The number of patients whose repair had failed at ten years was ten of 58 (17%) in the ACI group and 23 of 42 (55%) in the mosaicplasty group (p < 0.001).

The functional outcome of those patients with a surviving graft was significantly better in patients who underwent ACI compared with mosaicplasty (p = 0.02).

Matrix-induced autologous chondrocyte implantation (MACI) is an established technique used to treat osteochondral lesions in the knee. For larger osteochondral lesions (> 5 cm²) deeper than approximately 8 mm we have combined the use of two MACI membranes with impaction grafting of the subchondral bone. We report our results of 14 patients who underwent the ‘bilayer collagen membrane’ technique (BCMT) with a mean follow-up of 5.2 years (2 to 8). There were 12 men and two women with a mean age of 23.6 years (16 to 40). The mean size of the defect was 7.2 cm² (5.2 to 12 cm²) and were located on the medial (ten) or lateral (four) femoral condyles. The mean modified Cincinnati knee score improved from 45.1 (22 to 70) pre-operatively to 82.8 (34 to 98) at the most recent review (p < 0.05). The visual analogue pain score improved from 7.3 (4 to 10) to 1.7 (0 to 6) (p < 0.05). Twelve patients were considered to have a good or excellent clinical outcome. One graft failed at six years.

The BCMT resulted in excellent functional results and durable repair of large and deep osteochondral lesions without a high incidence of graft-related complications.

Introduction

We report the initial 2 and 3 year follow-up results of this randomised controlled trial of autologous chondrocyte implantation (ACI) using porcine-derived collagen membrane as a cover (ACI-C) versus matrix-carried autologous chondrocyte implantation (MACI) for the treatment of osteochondral defects of the knee.

The results for autologous chondrocyte implantation (ACI) in the treatment of osteochondral defects in the knee are encouraging. At present, two techniques have been described to retain the chondrocyte suspension within the defect. The first involves using a periosteal flap harvested from the distal femur and the second involves using a type I/III collagen membrane. To the authors' knowledge there are no comparative studies of these two techniques in the current literature.

A total of 68 patients with a mean age of 30.52 years (range 15 to 52 years) with symptomatic articular cartilage defects were randomised to have either ACI with a periosteal cover (33 patients) or ACI with a type I/III collagen cover (35 patients). The mean defect size was 4.54 cm² (range 1 to 12 cm²). All patients were followed up at 24 months.

A functional assessment using the Modified Cincinnati score showed that 74% of patients had a good or excellent result following the ACI with collagen cover compared with 67% after the ACI with periosteum cover at 2 years (p>0.05). Arthroscopy at 1 year also demonstrated similar results for both techniques. However, 36.4% of the periosteum covered grafts required shaving for hypertrophy compared with 1 patient for the collagen covered technique.

This prospective, randomised study has shown no statistical difference between the clinical outcome of ACI with a periosteal cover versus ACI with a collagen cover at 2 years. A significant number of patients who had the ACI with periosteum technique required shaving of a hypertrophied graft within the first year of surgery. We conclude that there is no advantage in using periosteum as a cover for retaining the chondrocytes within an osteochondral defect; as a result we advocate the use of an alternative cover such as a porcine-derived, type I/III collagen membrane.

Aims

To investigate (1) The relationship between macroscopic grading and durability of cartilage repair following collagen-covered autologous chondrocyte implantation (ACI-C) in the knee; (2) The influence of histology on durability of cartilage repair; (3) The relationship between macroscopic appearance and histology of repair tissue.

Purpose

We report on minimum 2 year follow-up results of 71 patients randomised to autologous chondrocyte implantation (ACI) using porcine-derived collagen membrane as a cover (ACI-C) and matrix-induced autologous chondrocyte implantation (MACI) for the treatment of osteochondral defects of the knee.

None

Autologous chondrocyte implantation (ACII) has been shown to have favourable results in the treatment of symptomatic chondral and osteochondral lesions. However, there are few reports on the outcomes of this technique in adolescents.

The aim was to assess functional outcome and pain relief in adolescents undergoing autologous chondrocyte implantation (ACI).

Thirty-one adolescent patients undergoing ACI or Matrix-assisted chondrocyte implantation (MACI) were identified from a larger prospective study. Mean age was 16.3 years (range 14 – 18) with a mean follow-up of 66.3 months (12–126 months).

There were 22 males and nine females. All patients were symptomatic; 30 had isolated lesions and one had multiple lesions. Patients were assessed pre and postoperatively using the Visual Analogue Score (VAS), the Stanmore/Bentley Functional Rating Score and the Modified Cincinnati Rating System.

The mean VAS improved from 5.8 pre-operatively to 2 post-operatively. The Stanmore/Bentley Functional Rating Score improved from 2.9 to 0.9 whilst the Modified Cincinnati Rating System improved from 49.8 pre-operatively to 81.3 postoperatively with 87% of patients achieving excellent or good results. All postoperative scores exhibited statistically significant improvement from pre-operative scores.

The results show that, in this particular group of patients, this procedure produces reduction in pain and a statistically significant improvement in function postoperatively. We strongly recommend this procedure in the management of adolescents with symptomatic chondral defects.

High Tibial Osteotomy (HTO) is a recognised method of correction for knee joint malalignment and unicom-partmental osteoarthritis. Long-term results of this technique have been reported and are favourable. Good results have also been reported with Autologous Chondrocyte Implantation (ACI-C, MACI). Malalignment, if present, should be corrected when ACI is performed. Although results have been reported for either procedure separately, the outcomes of combined HTO-ACI remain unreported. The aim of this study was to evaluate functional outcome in patients undergoing combined HTO-ACI procedures.

Twenty three patients undergoing a combined ACI-HTO procedure were identified retrospectively from a larger trial of patients undergoing ACI for symptomatic chondral defects. The mean age of the patients was 36 (28 – 49). The mean follow-up was 54 months (12 – 108) and mean defect size was 689mm2 (range 350 – 1200). Nine patients had ACI-C and HTO, the remainder having MACI and HTO. Pre and post-operative assessment was carried out using the Visual Analogue Score (VAS), the Bentley Functional Rating Score and the Modified Cincinnati Rating System.

The Mean VAS score improved from 7.4 (4 – 10) pre-operatively to 2.9 (0 – 6) post-operatively at the latest follow-up (p< 0.0001). The Bentley Functional Rating Score improved from 2.9 (2 – 4) to 1.8 (0 – 4), which was statistically significant (p< 0.0001). The Modified Cincinnati Rating System improved from 35.2 (20 – 49) pre-operatively to 68.7 (46 – 85) post-operatively (p< 0.0001). Fourteen patients underwent biopsy of the graft site at a mean of 13.7 months: 21% of biopsies were hyaline-like cartilage, 36% were mixed hyaline/fibrocartilage, 29 % were fibrocartilage and 14% were fibrous tissue.

Combining high tibial osteotomy with autologous chondrocyte implantation is an effective method of decreasing pain and increasing function in the short term. Further evaluation of this procedure is required.

Introduction: Autologous Chondrocyte Implantation (ACI) is a treatment option for symptomatic, full-thickness chondral/osteochondral injuries. Goals of surgery and rehabilitation include replacement of damaged cartilage with hyaline/hyaline-like cartilage, leading eventually to improved level of function. Intermediate and long-term results are promising in terms of functional improvement.

Purpose: To explore the hypothesis that non-hyaline cartilage repair tissue is associated with worse functional outcome and to assess whether the quality of the repair tissue formed following ACI improves with time post-surgery.

Methods and Results: Two hundred and forty eight patients who underwent ACI at our institution were studied, having had post-implantation biopsies of the repair tissue. Mean timing of biopsy was 14.8 months (range 3–55). 59 biopsies showed hyaline tissue (24%), 67 mixed hyaline and fibrocartilage (27%), 113 biopsies were fibrocartilage only (46%) and 9 patients had a fibrous tissue biopsy result (9%). 126 patients (51%) had hyaline tissue in the regenerate and demonstrated a mean Modified Cincinnati Rating Score (MCRS) of 84 and a mean Lysholm Score of 88 at last follow-up (Group 1). 122 patients (49%) had no hyaline tissue in the regenerate and scored a mean MCRS of 71 and a mean Lysholm Score of 73 (Group 2). Both Groups 1 and 2 demonstrated a statistically significant improvement in functional outcome between pre and post-operative scores (p< 0.0001). There was significant difference in post-operative scores between Groups 1 and 2 suggesting that presence of hyaline tissue in the regenerate is associated with improved functional outcome (p< 0.05). Finally, our statistical analysis suggested that if time post-implantation doubles, then the likelihood of a favourable histological outcome increases significantly.

Conclusion: ACI forms a durable repair tissue that remodels and continues to improve in quality with time. Poor functional outcome may reflect the presence of a non-hyaline cartilage repair tissue.

Introduction: Autologous chondrocyte implantation (ACI) has been used to treat patella cartilage lesions but several studies have indicated poorer results compared to lesions on the femoral condyles. This paper investigates the effectiveness of two different methods of ACI; porcine-derived collagen membrane as a cover (ACI-C) and matrix-carried autologous chondrocyte implantation (MACI).

Methods: 124 patients (mean age 33.5) with symptomatic osteochondral lesions in the patella were selected to undergo either ACI (56 patients) or MACI (68 patients). 1 year following surgery patients underwent check arthroscopy to assess the graft. Functional assessment was performed pre-operatively, at 6 months and yearly by using the modified Cincinnati score (MCS).

Results: 37.5% of patients experienced good or excellent clinical results according to the MCS in the ACI group compared with 69.2% in the MACI group (p = 0.0011). The mean MCS improved from 43.7 pre-operatively to 49.8 2 years following surgery in the ACI group, whereas in the MACI group the improvement was from 44.6 to 60.6 (p=0.07). Arthroscopic assessment showed a good to excellent International Cartilage Repair Society score in 89.7% of ACI-C grafts and 69.6% of MACI grafts (p = 0.08). There was a higher re-operation rate (p = 0.044) in the ACI group (29%) compared with MACI (10%).

Conclusions: The results from this paper suggest that MACI is more successful in the treatment of patella cartilage lesions than ACI even though arthroscopic assessment showed the converse to be true. The higher complication and re-operation rate suggests that we should be treating such patients with MACI.

High tibial osteotomy (HTO) is a recognised method of correction for knee joint malalignment and unicompartmental osteoarthritis. The long term results of this technique have been reported and are favourable. Autologous chondrocyte implantation (ACI-C, MACI) has also been reported to have good results It is advised that malalignment, if present, should be corrected if ACI is to be performed. Although results have been reported for either procedure separately, the outcomes of combined HTO-ACI remain unreported.

To evaluate functional outcome in a group of patients undergoing combined HTO-ACI procedures.

Twenty three patients undergoing a combined ACI-HTO procedure were identified retrospectively from a larger trial of patients undergoing ACI for symptomatic chondral defects. The mean follow-up was 54 months (range 12 – 108) and the mean defect size was 689 mm2 (range 350 – 1200). Nine patients had ACI-C and HTO, the remainder having MACI and HTO. Pre and postoperative assessment was carried out using the Visual Analogue Score (VAS), the Bentley Functional Rating Score and the Modified Cincinnati Rating System.

The Mean VAS score improved from 7.4 pre-operatively to 2.9 post-operatively (p< 0.0001). The Bentley Functional Rating Score improved from 2.9 to 1.8 (p< 0.0001) whilst the Modified Cincinnati Rating System improved from 35.2 pre-operatively to 68.7 post-operatively (p< 0.0001). There was no significant difference between ACI-C and MACI. Two patients developed a non union at a mean of 13 months and a further two patients had a failure of the chondrocyte graft at a mean of 22.5 months.

Combining high tibial osteotomy with autologous chondrocyte implantation is an effective method of decreasing pain and increasing function at mean of 54 months follow-up. Further follow-up is required to assess the long term outcomes of these combined procedures.

Introduction: Autologous Chondrocyte Implantation (ACI) is a treatment option for full-thickness chondral, or osteochondral injuries that are painful and debilitating. Goals of surgery and rehabilitation include replacement of damaged cartilage with hyaline or hyaline-like cartilage, leading eventually to improved level of function. Intermediate and long-term results are promising in terms of functional and clinical improvement.

Purpose: To explore the hypothesis that the quality of the repair tissue, formed following Autologous Chondrocyte Implantation (ACI), improves with time post-surgery.

Methods and Results: Two hundred and forty eight patients who underwent autologous chondrocyte implantation in our institution were studied after having had post implantation biopsies of the repair tissue. Mean timing of biopsy was 14.8 months (range 3–55). 59 biopsies gave hyaline tissue (24%), 67 mixed hyaline and fibrocartilage (27%), 113 biopsies were fibrocartilage only (46%) and 9 patients had a fibrous tissue biopsy result (9%). Due to NHS restraints and waiting list targets biopsies were actually performed at various time points post implantation allowing us to statistically correlate histological findings with the maturity of the repair tissue.

Our statistical analysis suggests that if time post implantation doubles then the likelihood of a favourable histological outcome increases significantly.

Conclusion: Autologous chondrocyte implantation forms a durable repair tissue that remodels and continues to improve in quality with time. It is recommended that for future research/study purposes 24 months is used as an optimal time to look at histology, since our data show that outcome is still improving until this point.

Introduction: Initial results for the management of osteochondral defects with both ACI-C and MACI have been encouraging, showing significant clinical improvement. This single-centre study set out to determine any significant difference in outcomes between ACI-C and MACI.

Aim: Reporting three year follow up of clinical and arthroscopic assessment of prospective analysis of ACI-C and MACI used in the management of symptomatic, full-thickness chondral and osteochondral defects in the knee.

Method: Following assessment arthroscopy and harvesting of chondrocytes for culture, patients were randomised into the ACI-C or MACI arm and underwent their respective procedures one month later. In ACI-C a covered technique is employed using a porcine-derived type I/III collagen membrane sutured in place; MACI requires cultured autologous chondrocytes to be seeded in a bi-layered type I/III collagen membrane which is glued into position. An arthroscopy was performed at 12 and 24 months postprocedure to assess graft coverage and biopsies taken to determine extent of hyaline, mixed and fibro-cartilage proliferation.

Results: 102 patients underwent either ACI-C (44) or MACI (58) with an average age of 33.6 (14–52). Mean Cincinnati knee rating scores recorded prior to assessment arthroscopy for ACI-C: 45.2 (10 – 94) and MACI: 45.5 (10 – 90) showed improvement at follow up with 63% of patients in the ACI-C group scoring good or excellent at three years, and 60% in the MACI group. ICRS arthroscopy scores were good or excellent in 91.4% of ACI-C and 76.1% of MACI patients at 24 months. Biopsies of the transplants at 24 months revealed proliferation of hyaline and mixed cartilage (hyaline and fibro-cartilage) in 48.6% of the ACI-C and 30.5% of the MACI patients.

Conclusion: Results to date suggest significant clinical and arthroscopic improvement following ACI-C and MACI, with evidence of proliferation of hyaline cartilage at the transplant site. Limited differences are noted between the outcomes of the two techniques.

Purpose: We attempted to identify whether patients with early evidence of osteoarthritis (OA) on their pre-operative radiographs were associated with poorer outcomes after Autologous Chondrocyte Implantation (ACI).

Methods: We retrospectively reviewed radiographs of 94 consecutive patients who underwent ACI and had already had their knee function assessed according to the Modified Cincinatti Score 2 years following surgery. Changes were graded according to The Kellgren and Lawrence (K& L) and the Stanmore grading system. Two independent observers analysed the films to assess the reproducibility and accuracy of these grading systems for assessment of OA in the knee.

Results: Patients were divided into 2 groups; Group A were patients with excellent/good outcome (52 patients), those with fair/poor outcome were Group B (42 patients).13 patients in Group A and 21 patients in Group B had radiographic evidence of OA (p< 0.025). In 34 patients who had OA (mean age 33.6) the increase in Cincinatti score following surgery was minimal (33.5 to 37.5). In 60 patients where there was no evidence of OA (mean age 33.7) the score increased from 40 to 53.4. The inter-observer variation was greater using K& L (Kappa=0.31) compared with the Stanmore grading systems (Kappa=0.72).

Conclusions: Patients with early radiographic evidence of OA are unlikely to gain maximum benefit from ACI. Furthermore, we recommend the use of Stanmore grading system for the assessment of OA as it is more reproducible than the K& L grading system.

Orthopaedic surgeons vary in their attitude towards resurfacing of the patella in total knee arthroplasty. Few studies are available to assess outcome and patient preference. We evaluated post-operative anterior knee pain and knee preference in patients with bilateral knee replacements and unilateral patellar resurfacing.

We reviewed 30 patients who had undergone bilateral knee replacement with patellar resurfacing on only one side. Follow-up was from five to 12 years and the patients were assessed using the Knee Society rating, an anterior knee pain rating and a satisfaction score. Patients were also asked specifically if they had a preference for either knee. Assessment was performed without knowing which patella had been resurfaced.

Fourteen patients (47%) favoured the resurfaced knee, six (20%) the un-resurfaced knee and 10 (33%) had no particular preference. The overall prevalence of anterior knee pain was 50% in the un-resurfaced cases (six mild, six moderate, three severe) and 20% in the resurfaced knees (four mild, two moderate). No significant difference was found between knee scores. Three un-resurfaced patellae have been secondarily resurfaced.

This study shows a significant preference for the resurfaced side (p< 0.01), with a higher prevalence of anterior knee pain in non-resurfaced patellae (p< 0.05).

Smoking is known to have an adverse effect on wound healing and musculoskeletal conditions. This case-controlled study looked at whether smoking has a deleterious effect in the outcome of autologous chondrocyte implantation for the treatment of full thickness chondral defects of the knee.

The mean Modified Cincinatti Knee score was statistically significantly lower in smokers (n = 48) than in non-smokers (n = 66) both before and after surgery (p < 0.05). Smokers experienced significantly less improvement in the knee score two years after surgery (p < 0.05). Graft failures were only seen in smokers (p = 0.016). There was a strong negative correlation between the number of cigarettes smoked and the outcome following surgery (Pearson’s correlation coefficient −0.65, p = 0.004).

These results suggest that patients who smoke have worse pre-operative function and obtain less benefit from this procedure than non-smokers. The counselling of patients undergoing autologous chondrocyte implantation should include smoking, not only as a general cardiopulmonary risk but also because poorer results can be expected in smokers following this procedure.

Autologous chondrocyte implantation is an option in the treatment of full-thickness chondral or osteochondral injuries which are symptomatic. The goal of surgery and rehabilitation is the replacement of damaged cartilage with hyaline or hyaline-like cartilage, producing improved levels of function and preventing early osteoarthritis. The intermediate results have been promising in terms of functional and clinical improvement.

Our aim was to explore the hypothesis that the histological quality of the repair tissue formed after autologous chondrocyte implantation improved with increasing time after implantation.

In all, 248 patients who had undergone autologous chondrocyte implantation had biopsies taken of the repair tissue which then underwent histological grading. Statistical analysis suggested that with doubling of the time after implantation the likelihood of a favourable histological outcome was increased by more than fourfold (p < 0.001).

Chondral damage to the knee is common and, if left untreated, can proceed to degenerative osteoarthritis. In symptomatic patients established methods of management rely on the formation of fibrocartilage which has poor resistance to shear forces. The formation of hyaline or hyaline-like cartilage may be induced by implanting autologous, cultured chondrocytes into the chondral or osteochondral defect.

Autologous chondrocyte implantation may be used for full-thickness chondral or osteochondral injuries which are painful and debilitating with the aim of replacing damaged cartilage with hyaline or hyaline-like cartilage, leading to improved function. The intermediate and long-term functional and clinical results are promising.

We provide a review of autologous chondrocyte implantation and describe our experience with the technique at our institution with a mean follow-up of 32 months (1 to 9 years).

The procedure is shown to offer statistically significant improvement with advantages over other methods of management of chondral defects.

Introduction: Smoking is associated with impaired wound healing, delayed bony union following fractures and an adverse effect on the immune system. Furthermore, smoking is an important risk factor for the development pulmonary complications following major surgical procedures, as well as wound complications. We determined whether smoking had a deleterious effect on outcome after autologous chondrocyte implantation (ACI) in the treatment of ostechondral defects of the knee.

Methods: We identified 103 (54 females and 49 males) patients with a mean age of 34.2 (range 18 to 49) who had undergone ACI between January 2001 and August 2004 who also had their smoking status recorded. The patients were divided into 3 groups according to their smoking status. The Visual Analogue Score, Bentley Functional Rating Score and Modified Cincinatti Scores were used to assess function pre-operatively, 6 months and then yearly thereafter.

Results: Group 1 consisted of 31 smokers (mean pack years of 13.4), group 2 consisted of 63 non-smokers and group 3 contained 9 ex-smokers. In Group 1, the Modified Cincinatti Score pre-operatively, 6 months, 1 year and 2 years following surgery were 34.1, 42.6, 43.5 and 46.7 respectively. In group 2 the scores were 47.4, 59.6, 59.1, 65.3, and in group 3 the scores were 39.8, 50, 53.3, 51.8. At the 1 year check arthroscopy, the graft failure rate in group 1 was 12% and biopsies revealed mixed hyaline and fibrocartilage in only 25% (there were no patients with hyaline cartilage). There were no graft failures in group 2 and 43.8% of the biopsies performed were either hyaline (12.5%) or mixed hyaline and fibrocartilage (31.3%). The wound complication rate was 24% in group 1 and 8% in group 2.

Conclusions: The results of this study suggest that people who smoke have a worse functional outcome and a higher complication rate following chondrocyte implantation. This association has not been previously described and should be included in the pre-operative counselling of patients undergoing the procedure.

Introduction: Several studies have implicated excessive weight as a negative predictor of success of total knee arthroplasty. In addition, obese patients are known to have increased risk of wound complications after orthopaedic and general surgery. The purpose of this study was to compare the clinical and functional outcomes of autologous chondrocyte implantation for treatment of osteochondral defects of the knee performed in obese patients with those performed in non-obese patients.

Methods: We analysed the data on all our patients that have been followed up for a minimum of 2 years and had their height and weight recorded initially in our database. Functional assessment consisted of Bentley Functional Rating Score, Visual Analogue Score, and the Modified Cincinatti Scores (collected prospectively at 6 months, 1 year, 2 years and 3 years following surgery). Patients were placed into 3 groups according to their body mass index (BMI). Group A consisted of patients with BMI of 20 to 24.9, group B patients with BMI of 25 to 29.9 and Group C are patients with BMI of 30 to 39.9.

Results: There were 80 patients (41 males and 39 females) with a mean age of 35.4 (range 18 to 49). The mean BMI for the entire group was 26.6. The pre-operative, 6 month, 1 year, 2 year, and 3 year Modified Cincinatti Score in Group A (32 patients) was 54.4, 80.3, 82.7, 74.7 and 72.6. Similarly in Group B, the scores were 53, 41, 54, 56, 49.5 and in Group C the scores were 36.3, 36.3, 49.6, 36, and 35.7. The wound infection rate in Group A was 6.25%, in Group B was 17.6% and Group C was 14.3%.

Conclusions: Initial results from this study suggest that BMI is an important predictor of outcome after chondrocyte implantation. The group of patients that would gain most benefit from ACI are patients that are not overweight (defined by BMI in the range of 20 to 24.9). Further work is being carried out to support the hypothesis that surgeons should strongly consider not operating on patients unless the BMI is less than 25.

Introduction: ACI is used widely as a treatment for symptomatic chondral and osteochondral defects of the knee. Variations of the original periosteum-cover technique include the use of porcine-derived type I/type III collagen as a cover (ACI-C) and matrix-induced autologous chondrocyte implantation (MACI) using a collagen bilayer seeded with chondrocytes. We report the minimum 2 year follow-up results of 192 patients randomised to autologous chondrocyte implantation (ACI) using porcine-derived collagen membrane as a cover (ACI-C) and matrix-induced autlogous chondrocyte implantation (MACI) for the treatment of osteochondral decfects of the knee.

Methods: 192 patients (mean age 34.2) were randomised to have either ACI (86 patients) or MACI (106 patients). 1 year following surgery patients underwent check arthroscopy (with or without biopsy) to assess the graft. Functional assessment was performed yearly by using the modified Cincinatti knee score, the Bentley functional rating score and the visual analogue score.

Results: 24 patients were excluded from the study as they underwent additional procedures (e.g. high tibial osteotomy). In the ACI group the modified Cincinatti score increased from 42.5 pre-operatively to 56.7, 54.1, and 60.4 at 1 year, 2 years and 3 years respectively. In the MACI group the Cincinatti scores increased from 46.0 pre-operatively to 59.9, 58.9, and 58.4. Arthroscopic assessment showed a good to excellent International Cartilage Repair Society score in 90.7% of ACI-C grafts and 68.4% of MACI grafts. Hyaline-like cartilage or hyaline-like with fibrocartilage was found in biopsies of 51.9% of ACI-C grafts and 25.9% of MACI grafts.

Conclusions: ACI grafts are more likely to produce hyaline-like or mixed hyaline-like cartilage and fibro-cartilage with better ICRS grades than MACI grafts. However, this does not translate to better a clinical functional outcome. More importantly, ACI and MACI had similar results that were maintained at 3 years.

Aims: he purpose of this study was to determine whether autologous chondrocyte implantation (ACI) in patients with articular cartilage defects of the knee resulted in patients returning to pre-injury levels of work and physical activities.

Methods: 133 consecutive patients from January 2001 to December 2002 underwent ACI at our institution. A telephone and postal questionnaire was conducted to ascertain a detailed occupational and leisure activity profile in this cohort of patients. For each job held for at least 2 months, we asked whether an average working day had involved any of the ten specified physical activities. Similarly, for each sport that had been played more than 5 times a year, we asked the age the sporting activities had began and whether they were able to return to these sports after surgery. Occupation for each patient was given a 3 digit code according to the Standard Occupational Classification System 2000 and hence determined whether the work performed was manual or non-manual.

Results: 97 patients responded to the questionnaire. There were 53 females and 44 males and the mean age at the time of operation was 34.5 (range 14 to 49). Category 6 (Personal Services Occupations) was the most common occupation pre-operatively, whereas category 4 (Administrative and Secretarial Occupations) was the most common post-operatively. 7% of patients’ work involved kneeling or squatting and this figure rose to 12%, 4 years following surgery. 42% of patients had to make some form of modification to their work (usually less physical or more office based). 47% of patients were able to return to at least one of the sports they played pre-injury.

Conclusion: This is the first study to demonstrate that patients are able to return to work and resume sporting activity following autologous chondrocyte implantation.

Aims: To compare the clinical and functional outcomes of autologous chondrocyte implantation for treatment of osteochondral defects of the knee performed in overweight, obese and patients of ‘ideal weight’as defined by their BMI.

Methods: We analysed the data on all our patients that have been followed up for a minimum of 2 years and had their height and weight recorded initially in our database. Functional assessment consisted of the Modified Cincinatti Scores (collected prospectively at 6 months, 1 year, 2 years and 3 years following surgery). Patients were placed into 3 groups according to their body mass index (BMI). Group A consisted of patients with BMI of 20 to 24.9, group B patients with BMI of 25 to 29.9 and Group C are patients with BMI of 30 to 39.9.

Results: There were 80 patients (41 males and 39 females) with a mean age of 35.4 (range 18 to 49). The mean BMI for the entire group was 26.6. The pre-operative, 6 month, 1 year, 2 year, and 3 year Modified Cin-cinatti Score in Group A (32 patients) was 54.4, 80.3, 82.7, 74.7 and 72.6. Similarly in Group B, the scores were 53, 41, 54, 56, 49.5 and in Group C the scores were 36.3, 36.3, 49.6, 36, and 35.7. The wound infection rate in Group A was 6.25%, in Group B was17.6% and Group C was 14.3%.

Conclusions: Initial results from this study suggest that BMI is an important predictor of outcome after chon-drocyte implantation. The group of patients that would gain most benefit from ACI are patients that are not overweight (defined by BMI in the range of 20 to 24.9). Further work is being carried out to support the hypothesis that surgeons should strongly consider not operating on patients unless the BMI is less than 25.

Aims: To investigate

the influence of histology on durability of cartilage repair following collagen-covered autologous chon-drocyte implantation (ACI-C) in the knee.

Patients and methods: The modified Cincinnati scores (MCRS) of eighty-six patients were evaluated prospectively at one year and at the latest follow-up (mean follow-up = 4.7yrs. Range = 4 to 7 years). Biopsies of their cartilage repair site were stained with Haema-toxylin and Eosin and some with Safranin O and the neo-cartilage was graded as hyaline-like (n=32), mixed fibro-hyaline (n=19) and fibro-cartilagenous tissue (n=35). Macroscopic grading of the repair tissue using the international cartilage repair society grading system (ICRS) was available for fifty-six patients in this study cohort. Statistical analyses were performed to investigate the significance of histology and ICRS grading on MCRS at 1 year and at the latest follow-up.

Results: The MCRS of all three histology groups were comparable at one year evaluation (p=0.34). However, their clinical scores at the latest follow-up showed a significantly superior result for those with hyaline-like repair tissue when compared to those with mixed fibro-hyaline and fibro-cartilagenous repair (p=0.05).

There was no correlation between the ICRS grading and MCRS either at one year (p=0.12) or at the latest follow-up (p=0.16). Also, the ICRS grading of the repair tissue did not correlate with its histological type (p=0.12).

Conclusion: We conclude that any form of cartilage repair gives good clinical outcome at one year. At four years and beyond, hyaline-like repair tissue produces a more favourable clinical outcome. Macroscopic evaluation using the ICRS grading system does not reflect the clinical outcome or its durability or the histological type of repair tissue.

Purpose: We report on minimum 2 year follow-up results of 71 patients randomised to autologous chon-drocyte implantation (ACI) using porcine-derived collagen membrane as a cover (ACI-C) and matrix-induced autologous chondrocyte implantation (MACI) for the treatment of osteochondral defects of the knee.

Introduction: ACI is used widely as a treatment for symptomatic chondral and osteochondral defects of the knee. Variations of the original periosteum-cover technique include the use of porcine-derived type I/type III collagen as a cover (ACI-C) and matrix-induced autolo-gous chondrocyte implantation (MACI) using a collagen bilayer seeded with chondrocytes.

Results: 71 patients with a mean age of 33 years (15–48) were randomised to undergo either an ACI-C or a MACI. 37 had ACI-C and 34 MACI. The mean size of the defect was 5.0cm2. Mean duration of symptoms was 104.4 months (9–456). Mean follow-up was 33.5 months (24–45). Functional assessment using the modified Cincinnati knee score, the Bentley functional rating score and the visual analogue score was carried out. Assessment using the modified Cincinnati knee score showed a good to excellent result in 57.1% of patients followed up at 2 years, and 65.2% at 3 years in the ACI-C group; and 63.6% of patients at 2 years, and 64% at 3 years in the MACI group. Arthroscopic assessments showed a good to excellent International Cartilage Repair Society score in 81.8% of ACI-C grafts (22 patients) and 50% of MACI grafts (6 patients). Fisher’s exact test showed a p value of p=0.35 (not statistically significant). Hyaline-like cartilage or hyaline-like cartilage with fibrocartilage was found in biopsies of 56.3% of the ACI-C grafts (9 out of 16 patients) and 30% of the MACI grafts (3 out of 10 patients) after 2 years. Fisher’s exact test showed a p value of p=0.25 (not statistically significant).

Conclusion: At this stage of the trial we conclude that the clinical, arthroscopic and histological outcomes are comparable for both ACI-C and MACI.

Aim: The aim of this study was to correlate the histology of cartilage repair site with long term clinical function.

Materials and methods: We have analyzed the clinical results of a cohort of patients who had collagen-covered autologous chondrocyte implantations performed since 1998. Our hypothesis was that the hyaline cartilage repair does influence the clinical outcome.

The modified Cincinnati scores (MCRS) of eighty-six patients were evaluated prospectively at one year and at the latest follow-up following ACI-C (mean follow-up= 4.7 years. Range= 4 to 7 years). All these patients underwent biopsies of their cartilage repair site performed at variable periods between six months and five years following ACI-C (mean=22.2 months). The neo-cartilage was graded as hyaline (n=32), mixed fibrohyaline (n=19), fibrocartilagenous (n=35) and fibrous (n=0).

Results: The clinical results showed that at one year, the percentage of patients with excellent and good results was 84.4, 89.5 and 74.3 respectively for those with hyaline, mixed fibro-hyaline and fibro-cartilagenous histology respectively. Their mean MCRS were 70.8, 72.4 and 66.2 respectively. This difference was not statistically significant (p=0.34).

However, their clinical scores at the latest follow-up demonstrated a significantly superior result for those with hyaline repair tissue when compared to those with mixed fibro-hyaline and fibro-cartilagenous repair tissue (p=0.05). The percentage of patients with excellent and good results for those with hyaline, mixed fibro-hyaline and fibro-cartilagenous repair was 75, 42 and 68.6 respectively. Their mean MCRS were 70.6, 56.8 and 63.9 respectively.

Conclusion: This study demonstrates that any form of cartilage repair would give good clinical outcome at one year. At four years and beyond, it appears that patients with hyaline repair tissue tend to show a more favourable clinical outcome whereas those who demonstrated mixed fibrohyaline and fibrocartilagenous repair would show less favourable clinical results.

Current bone grafts include allograft and autografts, both of which have limitations. Tissue engineering biotechnology has shown considerable promise in improving grafts. A competent graft material should ideally have osteoconductive and osteoinductive properties and comprise of bone forming cells and osteoinductive growth factors. In this study, we have evaluated the in vitro formation of bone and have used human demineralised bone matrix [DBM] and human insoluble collagenous matric [ICM] as scaffolds for mesenchymal stem cells [MSCs] and osteogenic protein [OP-1]. The objective was to determine whether combined addition of OP-1 and MSCs resulted in a superior bone graft substitute by improving the inherent osteoinductive property.

DBM and ICM were prepared and combined with rhOP [1.4 mg/0.25 mg of bone] and MSCs [1 x 105/ ml]. Statistically significant differences in MSC proliferation were seen between materials with and without OP-1 [P< 0.05}, n=8] in DBM on day 1, and both DBM and ICM on day 7 and 14. Enhanced osteogenic differentiation was observed in the presence of OP-1 when compared to DBM alone and on DBM and ICM with OP-1. In conclusion MSCs and OP-1 can be seeded together on DBM and ICM and Von Kossa staining and X-ray analysis confirmed in vitro de novo bone formation, with DBM + MSCs + OP-1 being more successful in this regard.

Conclusion: To date, no other study, to the author’s knowledge, has used MSCs and OP-1 together on a graft material; this funding, therefore, has very important clinical implications.

Limitations of allografts and autografts for bone repair have increased the demand for a synthetic bone graft substitute for load-bearing and non-load bearing osseous defects. Tissue engineering of bone has thus been implicated to circumvent and eliminate the limitations of existing therapies, with living cell-scaffold constructs ultimately “integrating” with the patients own tissue. Bone engineering requires cells, growth inducing factors and a scaffold for delivery of cells to the anatomic site, creation of 3-D space for tissue formation and mechanical support. In this study, we investigated whether addition of osteogenic Protein-1 (OP-1) enhanced the osseoinductive properties of hydroxyapatite (HA) loaded with mesenchymal stem cells (MSCs). The study was conducted over a fourteen day period and the two groups HA/MSC and HA/MSC loaded with OP-1 were analysed qualitatively by SEM and quantitatively by assessment of proliferation (Alamar blue assay and total cellular DNA) and differentiation marker alkaline phosphatase activity (ALP). HA/MS/OP-1 showed a statistically significant (p< 0.05) increase in cell proliferation (286.52 ± 58.2) compared to the unloaded samples (175.62 ± 23.51). ALP activity (release) was also significantly enhanced (p < 0.05) in the loaded samples at day 14 (12.63 ± 1.58) compared to the control (2.73 ± 1.07).

Conclusion: the osseoinductive potential of HA was markedly improved by the incorporation of MSC’s and OP-1. This type of graft could provide improved mechanical stability at an earlier time point, and may influence future clinical application of HA for load bearing sites.

Implantation of autologous chondrocytes and matrix autologous chondrocytes are techniques of cartilage repair used in the young adult knee which require harvesting of healthy cartilage and which may cause iatrogenic damage to the joint. This study explores alternative sources of autologous cells.

Chondrocytes obtained from autologous bone-marrow-derived cells and those from the damaged cartilage within the lesion itself are shown to be viable alternatives to harvest-derived cells. A sufficient number and quality of cells were obtained by the new techniques and may be suitable for autologous chondrocyte and matrix autologous chondrocyte implantation.

Introduction: Autologous chondrocyte implantation (ACI) is a technique described for treating symptomatic osteochondral defects in the knee. It is contra-indicated, however, in a joint rendered unstable by a ruptured anterior cruciate ligament (ACL). We present our early experience of combined ACL and ACI repair.

Methods: Patients underwent arthroscopic examination and cartilage harvesting of the knee. Chondrocytes were then cultured in plasma and a second operation was undertaken approximately four weeks later to repair the ruptured ACL with hamstring graft and to implant the chondrocytes via formal arthrotomy. Patients then underwent a graduated rehabilitation program and were reviewed at 6 and 12 months. Functional measurements were made using the Bentley functional scale and the modified Cincinnati rating system, with pain measured on a visual analogue scale. All patients also underwent formal clinical examination at each review.

Results: 4 out of the 5 patients reported an improvement in pain as measured on visual analogue scale, with 1 patient reporting no difference. 4 patients had stable knees as determined by negative anterior draw, negative Lachman’s test and negative pivot shift test; one patient showed improvement, but remained pivot shift positive. Improvements in Bentley scores were noted in 3 patients. Cincinnati scores were markedly improved in 3 patients and slightly improved in the remaining 2 patients. The only operative complications were a traction neuropraxia to the saphenous nerve of one patient requiring no treatment and a manipulation under anaesthesia for poor mobilisation in another patient, which was successful in improving range of movement. A further patient required arthroscopic trimming of the cartilage graft which had overgrown; this was also successful.

Conclusion: Symptomatic cartilage defects and ACL deficiency may co-exist in many patients and represent a treatment challenge. Our early results suggest that a combined ACL and ACI repair is a viable option in this group of patients and should reduce the anaesthetic and operative risks of a two-stage repair. More patients and longer follow up will be required to fully assess this technique.

Introduction and aim: Several authors have suggested that hyaline repair tissue following autologous – chondrocyte implantation (ACI) gives better clinical results than either mixed hyaline and fibrocartilage or fibrocartilage alone. This data is based on the use of periosteum as a covering membrane in these previous studies. We have for some years been using a porcine collagen type 1/III membrane (ACI-C) instead of periosteum and have now the opportunity to analyze the clinical results when compared with the histology of the repaired defect. We have also analysed the influence on the result of age and sex of the patient, the etiology of the lesion, the duration of the knee symptoms, number of previous knee procedures, the site and size of defect and the preoperative functional scores.

Method: Until 2004, 234 patients underwent autologous chondrocyte implantation at our centre. The patients were assessed clinically by their modified Cincinnati scores prospectively from 1 to 4 years from surgery. Also at arthroscopy (1 to 3 years following ACI-C) they underwent biopsy of the implant where possible and the neo-cartilage was graded as hyaline (H), mixed fibrohyaline (F.H), fibrocartilagenous (F.C) and fibrous (F).

Results: The clinical results showed that older patients had poorer results (p< 0.001) and a high preoperative modified Cincinnati score predicted a good result (p< 0.001). Concerning the cause of the defect, the percentage of patients with excellent and good results were significantly low among those with previously failed ACIs and mosaicplaties (12.5%) compared with those following trauma, osteochondritis dessicans and chondromalacia patellae (67% to 77%). At 4 year follow-up, 75% of patients with hyaline neo-cartilage had excellent and good modified Cincinnati scores whereas those with mixed fibro-hyaline and fibro-cartilage had fewer excellent and good results (44.4% and 54.5% respectively). The other parameters such as gender, the site of defect, duration of knee symptoms and the number of previous procedures and the size of the defect did not significantly influence the outcome. In conclusion, patients most likely to benefit from autologous chondrocyte implantation using a collagen membrane (ACI – C) are younger patients with higher preoperative functional scores and those who develop hyaline neo-cartilage.

Study Purpose: The cause of intervertebral disc degeneration (IVDD) is multifactorial. One proposed mechanism is that IVDD originates in the nucleus pulposus (NP) and progresses radially to the annulus fibrosis (AF). Failure of current treatment modalities in preventing and treating IVDD and thereby low back pain have led to a growing interest in tissue-engineered solutions where a biological repair is induced. By preventing the abnormality at the NP it may be possible to halt further progression of IVDD. Injection of NP cells into an early degenerative IVD, where the AF is still intact, may retard the degenerative process and is presently under investigation. Using a three-dimensional scaffold that could be successfully introduced into the NP cavity through minimally invasive techniques would prevent the loss of chondrocytic phenotype of the cells and be an improvement over the existing technique by which cells are directly injected into the NP cavity.

Methods: (1) CaSO4 and CaCO3 alginates were injected into the NP cavity of a bovine tail. After 90 minutes the tail was dissected to reveal the gel. (2) NP cells released from pooled bovine NP tissue were dispersed into the CaSO4 and CaCO3 alginate gels (10x106 cells.mL-1) with and without Synvisc® and cultured for 21 days.

Results: (1) Injectable alginate suspensions formed solid viscoelastic gels, filling the exact shape of the NP cavity. (2) NP DNA and ECM synthesis was significantly greater in the CaCO3 alginate gel than in the CaSO4 alginate gel (p< 0.05). (3) Synvisc® significantly increased sulphated GAG (p< 0.01) and collagen (p< 0.05) production. These effects were supported histologically and immunohistologically where cells in the CaCO3 and Synvisc® gels stained more intensely for proteoglycan and collagen type II.

Conclusions: Both CaCO3 alginate gel and CaSO4 alginate gel are injectable and are capable of sustaining NP cells in-vitro. Cells remain viable, maintain their phenotype, proliferate and produce ECM during the culture period. The CaCO3 alginate gel provides a three-dimensional matrix more favourable to NP cellular activity than the CaSO4 alginate gel. Synvisc® behaves as a chondro-stimulant significantly enhancing NP cell metabolic activity. This study demonstrates a successful tissue-engineered approach for replacing the NP and, subject to further studies, may be used for retarding mild-to-moderate IVDD, alleviating lower back pain and restoring a functional NP through a minimally invasive technique.

Ninety knees were treated in the same centre between1995 and 1999 each had Low Contact Stress (LCS) knee prosthesis with patelloplasty; none of the patients had resurfacing of the patella. The average follow-up period was seven years (ranging from five to nine years). There were no exclusion criteria, almost all the patients included in this study were available for follow-up, the mean age was 75 years, and the majority of the patients were affected by osteoarthritis. All the operations were done by the same surgeon or under his supervision according to the protocol.

Evaluation was performed with using The Knee Society Clinical Rating System and new Patellar Scoring System. The final scoring was done by an independent Senior Physiotherapist. The Knee Society’s radiological evaluation system was used to assess the pre and post-operative alignment of the knee and the prosthesis. Image Tool (IT accessories UTHSCSA) software used to for measurements of patellar tracking and alignments on the digitalised radiographs.

Pre-operatively, the mean Knee Society score on a scale ranging from 0-200 points was 81.50 points (range 25 to 124 points); postoperatively this score improved to a mean of 150.76 points (range 46 to 195 points). Statistical analysis using paired-comparison t-tests showed the score differences were statistically significant at p-values < 0.0001.

None of the patients required resurfacing during the follow-up. There were no reported cases of significant anterior knee pain, dislocation, maltracking or fractured patella.

Purpose: To assess costs and health status outcomes following ACI and mosaicplasty used to treat chondral knee defects (1).

Methods: Patients received ACI or mosaicplasty at the Royal National Orthopaedic Hospital between 1997 and 2001, or, were on a waiting list for ACI. Resource use per patient was collected to two years post-operatively. A postal questionnaire collected sociodemographic characteristics, knee-related (Modified Cincinnati Knee Rating System) and general health status (EQ-5D).

Results: 53 ACI, 20 mosaicplasty and 22 patients waiting for ACI participated in this study. The average cost per patient was higher for ACI (£10,600: 95%CI £10,036-£11,214) than for mosaicplasty (£7,948: 95%CI £6,957-£9,243). Estimated average EQ-5D social tariff improvements for QALYs (quality adjusted life years) were 0.23 for ACI and 0.06 for mosaicplasty. Average costs per QALY were: £23,043 for ACI and £66,233 for mosaicplasty. The ICER (incremental cost effectiveness ratio) for providing ACI over mosaicplasty was £16,349. Post-operatively, ACI and mosaicplasty patients (combined) experienced better health status than patients waiting for ACI. ACI patients tended to have better health status outcomes than mosaicplasty patients, although this was not statistically significant.

Conclusions: Average costs were higher for ACI than for mosaicplasty. However, both the estimated cost per QALY and ICER fell beneath an implicit English funding threshold of £30,000 per QALY. To our knowledge this is the first study to compare the costs and utility of ACI with alternative ‘best’ treatments for people with chondral knee problems. Prospective studies are required to confirm these results.

Bovine and human articular chondrocytes were seeded in 2% alginate constructs and cultured for up to 19 days in a rotating-wall-vessel (RWV) and under static conditions. Culture within the RWV enhanced DNA levels for bovine chondrocyte-seeded constructs when compared with static conditions but did not produce enhancement for human cells. There was a significant enhancement of glycosaminoglycans and hydroxyproline synthesis for both bovine and human chondrocytes. In all cases, histological analysis revealed enhanced Safranin-O staining in the peripheral regions of the constructs compared with the central region. There was an overall increase in staining intensity after culture within the RWV compared with static conditions. Type-II collagen was produced by both bovine and human chondrocytes in the peripheral and central regions of the constructs and the staining intensity was enhanced by culture within the RWV. A capsule of flattened cells containing type-I collagen developed around the constructs maintained under static conditions when seeded with either bovine or human chondrocytes, but not when cultured within the RWV bioreactor.

Background: Autologous chondrocyte implantation (ACI) was introduced over 15 years ago as a treatment for full-thickness chondral defects in the knee. Current understanding of ACI graft morphology and maturation in humans is limited. The aims of this study were determine the incidence of hyaline-like repair following ACI, and to clarify the relationship between repair morphology and clinical outcome.

Methods: A retrospective review of 194 ACI graft biopsies from 180 patients, and their clinical outcome was conducted. 154 Biopsies were performed 1 year after implantation and 40 biopsies were performed at 2 years. Three techniques of ACI implantation were used; Collagen covered ACI (ACI-C), periosteum covered ACI (ACI-P) and Matrix-Induced ACI (MACI).

Results: At 1 year, hyaline repair tissue was found in 48 (53%) ACI-C grafts, 7 (44%) ACI-P grafts, and 12 (36%) MACI grafts. The frequency of hyaline tissue found in biopsies performed at 2 years (84%) was significantly higher than those performed at 1 year (48.6%), p=0.0001, suggesting that grafts continue to remodel after the first year post implantation.

Clinical outcomes during the first two postoperative years did not vary according to repair morphology type, though hyaline repair was associated with better clinical outcomes beyond 2 years; At 1 year, good to excellent clinical scores were observed in 29 (78.4%) patients with hyaline-like repair, 23 (76.7%) patients with fibrohyaline repair, and 54 (74.0%) patients with fibrocartilage repair. By years 3 and 4 post-implantation, clinical scores further improved in patients with hyaline-like repair yet declined in those with fibrocartilage and fibrohyaline. The difference was significant at 3 years though not at 4 due to the small number of cases.

Conclusions: Achieving hyaline-like repair is critical to the longevity of cartilage repair. The finding of hyaline-like cartilage or fibrohyaline cartilage in 31 of 37 biopsies (84%) performed after 2 years is therefore encouraging and supports further use of the ACI technique.

Background: Autologous Chondrocyte Implantation (ACI) is widely used as a treatment for symptomatic chondral and osteochondral defects of the knee. Variations of the original periosteum cover technique include the use of porcine-derived type I/III collagen as a cover (ACI-C), and the use of a collagen bilayer seeded with chondrocytes (MACI).

Aim: To determine whether differences in clinical, arthroscopic and histological outcomes at 1 year exist between ACI-C and MACI techniques.

Methods: We have performed a prospective randomised comparison of ACI-C versus MACI for the treatment of symptomatic chondral defects of the knee on 91 patients of whom 44 received ACI-C and 47 received MACI grafts.

Results: Both treatments resulted in improvements of clinical scores after 1 year. Mean modified Cincinnati knee scores increased by 17.5 in the ACI-C group and 19.6 in the MACI group (p> 0.05). Arthroscopic assessments performed after 1 year demonstrated good to excellent ICRS graft repair scores in 79% of ACI-C grafts and 67% of MACI grafts. Hyaline-like or hyaline-like cartilage with fibrocartilage was found in the biopsies of 43% of ACI-C grafts and 36% of MACI grafts after 1 year. The rate of graft hypertrophy was 9% in the ACI-C group and 6% in the MACI group. The frequency of re-operation was 9% in each group.

Conclusions: We conclude that clinical, arthroscopic and histological outcomes are comparable for both ACI-C and MACI techniques. While the MACI technique is technically attractive, further long-term studies are required before widespread adoption of this new technique.

We prospectively studied the clinical, arthroscopic and histological results of collagen-covered autologous chondrocyte implantation (ACI-C) in patients with symptomatic osteochondritis dissecans of the knee. The study included 37 patients who were evaluated at a mean follow-up of 4.08 years.

Clinical results showed a mean improvement in the modified Cincinnati score from 46.1 to 68.4. Excellent and good clinical results were seen in 82.1% of those with juvenile-onset osteochondritis dissecans but in only 44.4% of those with adult-onset disease.

Arthroscopy at one year revealed International Cartilage Repair Society grades of 1 or 2 in 21 of 24 patients (87.5%). Of 23 biopsies, 11 (47.8%) showed either a hyaline-like or a mixture of hyaline-like and fibrocartilage, 12 (52.2%) showed fibrocartilage.

The age at the time of ACI-C determined the clinical outcome for juvenile-onset disease (p = 0.05), whereas the size of the defect was the major determinant of outcome in adult-onset disease (p = 0.01).

We investigated the prognostic indicators for collagen-covered autologous chondrocyte implantation (ACI-C) performed for symptomatic osteochondral defects of the knee.

We analysed prospectively 199 patients for up to four years after surgery using the modified Cincinnati score. Arthroscopic assessment and biopsy of the neocartilage was also performed whenever possible. The favourable factors for ACI-C include younger patients with higher pre-operative modified Cincinnati scores, a less than two-year history of symptoms, a single defect, a defect on the trochlea or lateral femoral condyle and patients with fewer than two previous procedures on the index knee. Revision ACI-C in patients with previous ACI and mosaicplasties which had failed produced significantly inferior clinical results. Gender (p = 0.20) and the size of the defect (p = 0.97) did not significantly influence the outcome.

Introduction and Aims: ACI (autologous chondrocyte implantation) using a periosteum cover was developed by Peterson et al. Recently, the technique has been developed using a Type I/Type III collagen membrane (Chondro-Gide). A second technique MACI (matrix-induced autologous chondrocyte implantation) has evolved using a membrane with chondrocytes seeded onto its surface. Aim is to review the one and two-year results of the first 159 patients at a single regional centre.

Method: The two-stage procedure was performed with a standardised, progressive rehabilitation program. Patients were assessed clinically at three, six, nine, 12 and 24 months (pain score, Modified Cincinnati, Bentley), and arthroscopically at 12 and 24 months.

Results: 159 patients have been assessed at one year and 101 patients at two years. Of those patients reviewed at one year, 110 patients had the ACI repair with Chondro-Gide, 31 patients had the ACI repair with periosteum and 18 patients had the MACI repair. Sixty-nine percent had good or excellent results at one year and 60% at two years.

These figures represent the early results of this study performed at this unit.

Conclusion: We propose that the ACI technique is valuable for selected patients with Chondral and osteochondral defects of the knee even with large and multiple defects in the articular cartilage.

Introduction and Aims: Uni-compartmental knee arthroplasty (UKA) is appropriate for one in three osteoarthritic knees requiring replacement. An accelerated protocol enables patients undergoing UKA to be discharged within 24 hours of surgery. Before such an approach is universally accepted it must be safe, effective and economically viable. A study was performed to compare the new accelerated protocol with current standard care in a state healthcare system.

Method: A single blind RCT design was used. Patients eligible for UKA were screened for NSAID tolerance, social circumstances and geographical location before allocation to either an accelerated recovery group (Group A) or a standard non-accelerated group (Group S). The accelerated protocol included dedicated pain management and discharge support. Primary outcome was the Oxford Knee Assessment at six months post-operation, compared using independent t tests. Pain, range of movement and incidence of complications were also recorded by assessors blind to group allocation. Cost effectiveness was calculated in quality life adjusted years (QLAY) using the Euroqual instrument. The study power was sufficient to avoid type 2 errors. The study was supported by a NHS Regional R& D grant.

Results: Forty-one patients (21 group A, 20 group S) were included. Groups had comparable age and patient profiles. Average discharge time was 37 hours (1.5 days) for group A and 114 hours (4.3 days) for group S. Pain on hospital discharge was similar for both groups. No significant difference was found between groups for pain or range of movement at any time, although patients in group S regained pre-operative flexion faster than group A. One major complication occurred in each group; one infection (group S) and one manipulation for poor movement (group A). The cost per QLAY for the new protocol was 59% of the standard care.

Conclusion: The new protocol allows for safe accelerated discharge from hospital after UKA. The approach is cost-effective and should help to increase the throughput of patients who require knee replacement.

The purpose of this study was to examine the effects of hyaluronic acid supplementation on chondrocyte metabolism in vitro. The clinical benefits of intra-articular hyaluronic acid injections are thought to occur through improved joint lubrication. Recent findings have shown that exogenous hyaluronic acid is incorporated into articular cartilage where it may have a direct biological effect on chondrocytes through CD44 receptors.

Bovine articular chondrocytes were isolated and seeded into alginate constructs. These were cultured in medium containing hyaluronic acid at varying concentrations. Samples were assayed for biochemical and histological changes.

There was a dose-dependent response to the exposure of hyaluronic acid to bovine articular chondrocytes in vitro. Low concentrations of hyaluronic acid (0.1 mg/mL and 1 mg/mL) significantly increase DNA, sulphated glycosaminoglycan and hydroxyproline synthesis. Immunohistology confirmed the maintenance of cell phenotype with increased matrix deposition of chondroitin-6-sulphate and collagen type II. These findings confirm a stimulatory effect of hyaluronic acid on chondrocyte metabolism.

Autologous chondrocyte implantation (ACI) is used widely as a treatment for symptomatic chondral and osteochondral defects of the knee. Variations of the original periosteum-cover technique include the use of porcine-derived type I/type III collagen as a cover (ACI-C) and matrix-induced autologous chondrocyte implantation (MACI) using a collagen bilayer seeded with chondrocytes. We have performed a prospective, randomised comparison of ACI-C and MACI for the treatment of symptomatic chondral defects of the knee in 91 patients, of whom 44 received ACI-C and 47 MACI grafts.

Both treatments resulted in improvement of the clinical score after one year. The mean modified Cincinnati knee score increased by 17.6 in the ACI-C group and 19.6 in the MACI group (p = 0.32). Arthroscopic assessments performed after one year showed a good to excellent International Cartilage Repair Society score in 79.2% of ACI-C and 66.6% of MACI grafts. Hyaline-like cartilage or hyaline-like cartilage with fibrocartilage was found in the biopsies of 43.9% of the ACI-C and 36.4% of the MACI grafts after one year. The rate of hypertrophy of the graft was 9% (4 of 44) in the ACI-C group and 6% (3 of 47) in the MACI group. The frequency of re-operation was 9% in each group.

We conclude that the clinical, arthroscopic and histological outcomes are comparable for both ACI-C and MACI. While MACI is technically attractive, further long-term studies are required before the technique is widely adopted.

Autologous chondrocyte implantation (ACI) is a technique used for the treatment of symptomatic osteochondral defects of the knee. A variation of the original periosteum membrane technique is the matrix-induced autologous chondrocyte implantation (MACI) technique. The MACI membrane consists of a porcine type-I/III collagen bilayer seeded with chondrocytes. Osteochondral defects deeper than 8 to 10 mm usually require bone grafting either before or at the time of transplantation of cartilage. We have used a variation of Peterson’s ACI-periosteum sandwich technique using two MACI membranes with bone graft which avoids periosteal harvesting. The procedure is suture-free and requires less operating time and surgical exposure. We performed this MACI-sandwich technique on eight patients, five of whom were assessed at six months and one year post-operatively using the modified Cincinnati knee, the Stanmore functional rating and the visual analogue pain scores.

All patients improved within six months with further improvement at one year. The clinical outcome was good or excellent in four after six months and one year. No significant graft-associated complications were observed. Our early results of the MACI-sandwich technique are encouraging although larger medium-term studies are required before there is widespread adoption of the technique.

An increasing number of patients are treated by autologous chondrocyte implantation (ACI). This study tests the hypothesis that culture within a defined chondrogenic medium containing TGF-β enhances the reexpression of a chondrocytic phenotype and the subsequent production of cartilaginous extracellular matrix by human chondrocytes used in ACI. Chondrocytes surplus to clinical requirements for ACI from 24 patients were pelleted and cultured in either DMEM (Dulbecco’s modified eagles medium)/ITS+Premix/TGF-β1 or DMEM/10%FCS (fetal calf serum) and were subsequently analysed biochemically and morphologically.

Pellets cultured in DMEM/ITS+/TGF-β1 stained positively for type-II collagen, while those maintained in DMEM/10%FCS expressed type-I collagen. The pellets cultured in DMEM/ITS+/TGF-β1 were larger and contained significantly greater amounts of DNA and glycosaminoglycans. This study suggests that the use of a defined medium containing TGF-β is necessary to induce the re-expression of a differentiated chondrocytic phenotype and the subsequent stimulation of glycosaminoglycan and type-II collagen production by human monolayer expanded chondrocytes.

Aims: The objective of this study was to clinically assess the outcome of CADCAM femoral components in the revision hip replacement. Methods: Between 1991 and 2000, 125 revision total hip replacements using CAD-CAM femoral components were performed. Clinical assessment was performed using the Harris Hip score, by direct patient consultation, and telephone or postal questionnaire. Survivorship was defined as the requirement for revision. Results: The patients were reviewed at a mean of 5.2 yrs (1 to 10)

The mean Harris hip score increased from 44 points (range, 27 to 71 points) preoperatively to 71 points (range, 21 to 98 points) at the time of the most recent follow-up. 9 patients required subsequent revision; 4 for aseptic loosening, 1 for septic loosening and 4 for fracture of the femoral component. Conclusions: CAD-CAM technology provides a viable alternative to the challenge of revision hip surgery, with results comparable to other cementless techniques.

Autologous chondrocyte implantation (ACI) and mosaicplasty are both claimed to be successful for the repair of defects of the articular cartilage of the knee but there has been no comparative study of the two methods. A total of 100 patients with a mean age of 31.3 years (16 to 49) and with a symptomatic lesion of the articular cartilage in the knee which was suitable for cartilage repair was randomised to undergo either ACI or mosaicplasty; 58 patients had ACI and 42 mosaicplasty. Most lesions were post-traumatic and the mean size of the defect was 4.66 cm². The mean duration of symptoms was 7.2 years and the mean number of previous operations, excluding arthroscopy, was 1.5. The mean follow-up was 19 months (12 to 26).

Functional assessment using the modified Cincinatti and Stanmore scores and objective clinical assessment showed that 88% had excellent or good results after ACI compared with 69% after mosaicplasty. Arthroscopy at one year demonstrated excellent or good repairs in 82% after ACI and in 34% after mosaicplasty. All five patellar mosaicplasties failed.

Our prospective, randomised, clinical trial has shown significant superiority of ACI over mosaicplasty for the repair of articular defects in the knee. The results for ACI are comparable with those in other studies, but those for mosaicplasty suggest that its continued use is of dubious value.

Autologous Chondrocyte Implantation (ACI) is a technique for repair of isolated symptomatic articular cartilage defects in the young adult knee. The knee is arthroscopically assessed and a sample of cartilage is harvested from the margin of the joint, this is digested and the liberated chondrocytes expanded in culture. At subsequent arthrotomy, the articular cartilage lesion is debrided and the cells injected behind a sutured flap. A concern regarding ACI is the iatrogenic insult to non-injured healthy cartilage adjacent to that harvested for culture.

Damaged cartilage around the lesion is routinely debrided and discarded at the second stage operation. The purpose of this study was to determine whether this damaged debrided cartilage could yield an adequate number of equivalent chondrocytes for ACL.

Cells from 11 patients were analysed. The debrided “waste” from around the lesion was collected, enzymatically digested and the liberated chondrocytes cultured in monolayer.

The cells were recovered and placed in a 3D-pellet culture in a defined medium.

Chondrocytes obtained from the routine harvest of healthy cartilage were placed in a similar culture system. The two groups were compared using DNA and GAG assays, histological and immunohistochemical techniques.

Chondrocytes obtained from the debrided cartilage lesion were equivalent to those obtained from the harvested healthy cartilage. Sufficient cell numbers for implantation were achieved for all patients, however cells cultured from the debrided defect in patients who had a large degenerate lesion required significantly longer in culture to attain the required number of cells.

For many patients undergoing ACI, the potential iatrogenic insult to the joint cartilage of the harvesting procedure could be avoided by harvesting the damaged tissue from around the defect itself.

Mosaicplasty¹ and Autologous Chondrocyte Implantation² (ACI) are both modern cartilage repair techniques used to repair symptomatic articular cartilage defects in the knee, based on small osteochondral grafts and cultured chondrocytes respectively. The aim is the restoration of articular cartilage, but until now there is no data comparing the two methods.

100 consecutive patients aged 15–45 with a symptomatic articular cartilage lesion in the knee suitable for cartilage repair were randomised at arthroscopic assessment to undergo either mosaicplasty or ACI. 42 patients underwent mosaicplasty, 58 had ACI. Mean age at time of surgery was 31 years and the average defect size 4. 66 cm².

46% of the defects were post-traumatic, 19% had osteochondritis dissecans, 14% had chondromalacia patella and 16% had lesions of unknown aetiology. 53% had a medial femoral condyle lesion, 25% patella, 18% lateral femoral condyle, 3% trochlea and there was one defect of the lateral tibial plateau.

The mean duration of symptoms was 7. 2 years and the average number of previous operations (excluding arthroscopies) was 1. 5. Only 6 patients had no prior surgical interventions to the affected knee. The mean follow-up was 1. 7 years.

Patients were evaluated using Modified Cincinnati and Stanmore Functional rating systems, visual analogue scores and clinical assessment. Arthroscopy and biopsy was performed at one year and repair assessed with the International Cartilage Repair Society grading system.

Clinical results at one year showed 70% of mosaic-plasty patients and 87% of ACI patients had a good or excellent result. Arthroscopy at one year demonstrated more complete healing in ACI patients. Eleven (26%) of the mosaicplasty group subsequently failed clinically and arthroscopically, with peak failure at 2 years.

At one year follow-up, both techniques of articular cartilage repair can be useful in selected patients. ACI is preferred for lesions of the patella. Long-term follow-up is needed to assess the durability of articular cartilage repair using these methods, in particular mosaicplasty which showed signs of progressive failure over 2 years.

Autologous Chondrocyte Implantation’ (ACI) is a cartilage repair technique that involves implantation of cultured chondrocytes beneath a membrane of autologous periosteum. In this study a porcine biodegradable membrane was also used to assess its effectiveness. The aim is to restore articular cartilage to symptomatic defects, rather than initiating a fibrocartilagenous repair.

We undertook a prospective study of 125 consecutive patients who underwent ACI. Average age at the time of surgery was 30. 9 years (range 14 – 49), 55% of patients were male. The average size of the defect was 4. 35 cm².

44% of defects were attributable to known traumatic incidents, 2 1 % had osteochondritis dessicans, 18% chondromalacia patella, 12% had defects of unknown aetiology and 5% other.

The average duration of symptoms prior to this surgery was 7. 16 years. The mean number of previous operations (excluding arthroscopies) was 1. 6. Only 9 patients had no previous major surgery to the affected knee. 44% had defects of the medial femoral condyle, 31% patella, 20% lateral femoral condyle and 5% had a trochlea lesion. 26% of the defects were covered with periosteum and 74% with a porcine collagen membrane (chondrogide)

Minimum follow-up was six months, 70 patients had minimum follow-up of one year. Mean follow-up 18 months.

Patients were assessed using Modified Cincinnati and Stanmore Functional rating systems, visual analogue scores and clinical evaluation.

Arthroscopy and biopsy was performed at one year and the repair assessed using the International Cartilage Research Society grading system.

At one year follow-up overall 41 % patients had an excellent result, 48% good, 8% fair and 3% poor. For defects of the medial femoral condyle, 88% had a good or excellent result, 85% for the lateral femoral condyle and 80% for the patella.

61 patients were arthroscopically assessed at one year. 50/61 (82%) demonstrated ICRS grade 1 or 2 repair. Healing of the defect occurred with either a periosteum or chondrogide defect cover.

Results at one year suggest that ACI is a successful articular cartilage repair technique in selected patients. Long-term follow-up is required to assess the durability of the repair.

The clinical results of carbon matrix support prostheses for treatment of articular cartilage defects of the femoral condyle and patella were assessed in 97 patients (100 prostheses) between 1989–99. Patients were independently reviewed by subjective and objective criteria. Pre-operative and current visual analogue scores for pain (VAPS); Stanmore and modified Cincinnati functional rating scores were obtained. Forty-nine patients had lesions of the patella, forty-four patients of the medial femoral condyle and seven patients of the lateral femoral condyle.

Patella group – subjectively 49% reported they were improved, 8% unchanged and 43% worse. Stanmore score: 6 excellent and 17 good (47%), 5 fair and 21 were poor. The Cincinnati score increased from 26. 5 pre-operatively to 47. 5 currently (p< 0. 001). The mean VAPS decreased from 8. 1 to 5. 0 (p< 0. 001).

Medial femoral condyle group – subjectively 60% reported they were improved, 14% unchanged and 26% worse. Stanmore score: 8 excellent and 16 good (55%), 8 fair and 12 poor. The Cincinnati score increased from 22. 3 pre-operatively to 48. 5 currently (p< 0. 001). The mean VAPS decreased from 8. 6 to 5. 1 (p< 0. 001).

Lateral femoral condyle group – subjectively 42% reported they were improved, 29% unchanged and 29% worse.

Stanmore score: 2 excellent and 1 good (43%), 2 fair and 2 poor. The Cincinnati score increased from 35. 0 pre-operatively to 52. 0 currently (p< 0. 25). The mean VAPS decreased from 6. 5 to 4. 0 (p< 0. 25).

There were no statistical differences in outcome based upon gender, site, pre-operative functional rating score, diagnosis, or any correlation with age or length of follow up, or when comparing excellent/good with fair/ poor subgroups in patellae or femoral condyles in relation to these variables.

This study demonstrated that 49% improved in the patella group, 60% in the medial femoral condyle and 43% in the lateral femoral condyle groups. The use of these prostheses was effective on the medial femoral condyle for periods up to 10 years but the use in the patella and lateral femoral condyle was less successful.

The use of intra-articular hyaluronic acid injections for the treatment of early osteoarthritis is in widespread clinical use. Hyaluronate (HA) is a major component of connective tissue¹ and is available commercially for the intra-articular injective treatment of osteoarthritis of the knee and periarthritis of the shoulder. Although it is known to improve intra-articular lubrication it is also thought to promote articular cartilage structure and prevent catabolism of matrix proteoglycans in osteoarthritis. Clinical studies have shown beneficial effects lasting for many months after cessation of therapy unlike anti-inflammatory drugs that have relatively short term relieving effects^2,3 . Documentation of the true chondroprotective effects of hyaluronic acid (HA) at the cellular level is lacking and therefore this study aimed to identify the effects of HA on chondrocytes cultured in vitro.

Bovine articular chondrocytes were isolated by sequential digestion with pronase and collagenase and seeded in 2% alginate at 1x10⁷ cells/ml. The constructs were cultured for up to 14 days in standard culture medium (DMEM + 20% Fetal calf serum) containing varying concentrations of HA (Sigma), including doses equivalent to those found in vivo. The medium was replaced every 3 days and representative constructs were removed from culture, digested and assayed for DNA, glycosaminoglycans and Collagen. Further constructs were fixed in 4% paraformaldehyde for standard histology and immunolocalisation of collagen types I, II and chondroitin-6-sulphate.

Chondrocytes cultured in the HA system proliferated (increase in DNA) at a faster rate than the controls. There was a 2.2 fold increase in cell concentration at 14 days compared to a 1.2 fold increase in the controls. Total GAG levels at each time point were significantly greater for cells cultured in HA than in controls. Histologically, constructs were characterised by extensive cell cluster formation and intense Safranin-O staining. The newly synthesised matrix also stained positive for type II collagen. By contrast, control constructs exhibited minimal cluster formation, Safranin-O and type II collagen staining.

Cells maintained with HA exhibited a significantly greater rate of proliferation and matrix production. The presence of matrix rich in type II collagen indicates maintenance of chondrocytic phenotype. By contrast, cells cultured without HA did not show these features. These results support the use of intra-articular injections for the treatment of osteoarthritis. The benefits of HA injections may be due to cellular mechanisms as well as mechanical.

The use of intra-articular corticosteroid injections for their anti-inflammatory effects is widespread amongst clinicians. Despite their use in both rheumatoid arthritis and osteoarthritis, the effect of these agents on articular chondrocytes is not fully established. Previous reports suggest a detrimental effect on cartilage explants resulting from inhibition of matrix synthesis¹. However it has also been suggested that the beneficial effects in vivo may be due to prevention of inflamed synovium causing cartilage degradation². Our aim was to assess the effect of a commercially available preparation of methylprednisolone (MP), at clinical doses, on articular chondrocytes cultured in vitro.

Bovine articular chondrocytes were isolated by sequential digestion with pronase and collagenase and seeded in 2% alginate at 1x10⁷ cells/ml. The constructs were cultured for up to 15 days in standard culture medium (DMEM + 20% Fetal calf serum) containing varying concentrations of MP, including doses equivalent to those found in vivo. The medium was replaced every 3 days and representative constructs were removed from culture, digested and assayed for DNA and glycosaminoglycans. Further constructs were fixed in 4% paraformaldehyde for standard histology and immunolocalisation of collagen types I, II and chondroitin-6-sulphate.

Chondrocytes cultured in MP containing medium showed a significant abnormality in cell morphology compared to controls at the day 15 time point. Histologically there was evidence of cell necrosis, reduced amounts of extracellular matrix and loss of collagen type II staining. The effects were dose dependant, with significant damage occurring even at clinical doses. Biochemical analysis revealed a reduction in DNA content and an inhibition of glycosaminoglycan and collagen type II synthesis. In contrast, in the controls, there was cell proliferation with a cell doubling time of 14 days, collagen type II containing extracellular matrix synthesis occurred and the chondrocytes maintained their phenotype throughout the culture period.

Methylprednisolone has a significant detrimental effect on cultured articular chondrocytes in vitro. There was significant cell necrosis associated with inhibition of extracellular matrix synthesis. Based on these results, intra-articular corticosteroid injections should be used with extreme caution.

Nicotine is a constituent of tobacco smoke and is present in the body fluids of smokers^1,2. Numerous studies have confirmed that smoking is a strong risk factor for back pain³. The most widely accepted explanation for the association is that smoking leads to malnutrition of spinal discs due to carboxyhaemoglobin formation. However, other constituents of smoke, such as nicotine, may also be responsible for intervertebral disc (IVD) degeneration by leading to cell necrosis in both the nucleus pulposus and annulus fibrosis. Despite evidence suggesting the detrimental effect on a variety of tissues, the effect of nicotine on IVD cells has not previously been investigated. This study investigated the influence of nicotine on the metabolism and viability of IVD cells cultured in vitro.

Bovine nucleus pulposus (NP) intervertebral disc cells were isolated by sequential digestion of caudal spinal disc nuclei with pronase and collagenase and seeded in 2% alginate at 5x10⁶ cells/ml. The constructs were cultured for 21 days in standard culture medium (DMEM + 20% Fetal calf serum) containing free base nicotine (Sigma) at concentrations ranging from 25nM and 300nM, which reflected the normal physiological concentrations found in the serum of smokers. The medium was replaced every 3 days and representative constructs were removed from culture, digested and assayed for DNA, glycosaminoglycan (GAG) and hydroxyproline content at time points 3, 7, 14 and 21 days. Further constructs were processed for standard histology and immunolocalisation of collagen types I, II and chondroitin-6-sulphate.

The results were analysed statistically using an ANOVA test followed by a non-parametric Dunnit’s test. NP cells demonstrated a dose dependent response. At 25nM dose of nicotine there was a significant increase (p< 0.05) in DNA content, GAG and collagen synthesis in the constructs. At 100nM, 200nM and 300nM doses, there was a significant dose dependent decrease (p< 0.05) in all of these parameters compared to controls cultured under nicotine free conditions. In addition, adverse morphological changes were observed on histology, which included reduced cell proliferation, disrupted cell architecture, disintegration of cells and extracellular matrix. Immunohistochemistry showed the production of type I collagen rather than type II collagen as in the controls.

Nicotine has an overall detrimental effect on cultured nucleus pulposus disc cells in vitro. There was significant inhibition of cell proliferation and extracellular matrix synthesis. Nicotine in tobacco smoke may therefore play a role in the aetiology of disc degeneration that leads to back pain in smokers.

Deep infection is a devastating complication of total joint arthroplasty. In a significant proportion of cases it remains a diagnostic challenge. Haematological tests are not specific, particularly in chronic cases, and radiological investigations such as bone scan and radiographs are of only limited value. The most common infective organisms are staphylococcus and some streptococcus species. Acidity is a well established occurrence in infective processes and is caused by the direct production of acid by the organism or by enzymatic degradation of tissues ^1,2. In wound infections, peritonitis and some other conditions pH is used as an indicator of infection in clinical practice³. The aim was to assess whether fluid biochemistry (pH, pCO2, pO2, Lactate and Glucose) is altered in infected total knee replacements and whether it could be used as a diagnostic test.

Nineteen consecutive patients undergoing either revision total knee replacement (TKR) or arthroscopic synovial biopsy were included in the study. All had had their primary joint replacement within the previous 3 years. All had a painful total knee replacement and some had evidence of loosening of the prosthesis on radiological investigations. The following investigations were performed on each patient, White cell count (WCC), Erythrocyte Sedimentation Rate (ESR), C-Reactive Protein (CRP), interface synovial biopsy for histology and microbiology and a synovial fluid aspiration from the affected joint prior to application of a tourniquet. A blood gas analyser was used to measure pH, pCO2, pO2, Lactate and Glucose in all synovial fluid specimens.

Seven patients were diagnosed as having an infected TKR on clinical and laboratory investigations. The mean synovial fluid biochemistry results were pH = 7.09, pO2= 5.08kPa, pCO2=10.40kPa, Lactate = 5.33 mmol/l, Glucose = 2.30 mmol/l. In the non-infected group the results were pH = 7.23, pO2 = 7.72kPa, pCO2 = 8.41kPa, Lactate = 4.03 mmol/l, Glucose = 3.42 mmol/l. The differences in pH, pCO2/pO2 ratio, and glucose levels were statistically significant (t-Test p < 0.05) between the two groups. Lactate levels were not significantly different. There was no correlation between high WCC’s and synovial fluid biochemistry or laboratory results for infected cases. Using laboratory results as a gold standard and a synovial fluid pH of less than 7.20, the sensitivity was 85% and specificity 77% for diagnosing an infection. Using a combination of the synovial fluid biochemistry results these values were greater.

Synovial fluid biochemistry is significantly altered in infected total knee replacements. pH levels below 7.2, pCO2/pO2 ratio above 2.5 and Glucose levels below 2.5 mmol/l are strong indicators of an infected TKR. Synovial pH assessment may prove to be a quick, cheap and effective method of diagnosing an infected TKR and may also apply to other joints. Further studies using non-problematic TKR’s as controls are required.

Many methods have been described over the past 5 years for repair of articular cartilage defects. The best reported results have been from the use of autologous chondrocyte transplantation (ACT)(1) and mosaicplasty.(2) There have, however, been no prospective clinical trials of these two methods. In this trial 70 patients were prospectively randomized to receive either autologous chondrocyte transplantation (37) or mosaicplasty (33) in the knee. 37 patients were female and 33 male. The average age was 32 years (16 – 44). The indications for surgery were persistent pain and mechanical symptoms in the knee with an isolated defect of the articular cartilage. 38 (56%) were post-traumatic, 12 (16%) due to osteochondritis dissecans, 10 (14%) due to previous meniscectomy, and 10 (14%) due to chondromalacia patellae. The size of the defects ranged from 2cm2 to 12cm2 (mean 4.8cm2). There were 35 defects on the medial femoral condyle, 13 on the lateral femoral condyle, 17 on the patella and 5 on the trochlear. 31 patients were undergoing primary surgery and 39 secondary surgery. All were independently reviewed using the Visual Analogue Pain Score, the Cincinatti Pain Score and the Stanmore Score. Patients were arthroscoped at one year with MRI scan and biopsies where possible.

Results: The visual analogue pain score improved overall from a mean of 5.4 (range 3.4 – 7.4) pre-operatively to 3.9 (1.8 – 5.1) at one year review. Similarly the Cincinatti pain score improved from 6.5 pre-operatively to 10.2 post-operatively and the Cincinatti function score improved from 46 to 62 at one year before sport commenced. Overall 71% (49) patients were excellent or good on the clinical scoring scales, 15% (11) were fair, and 14% (10) were poor. The 10 poor results were no different from the main group with regard to age, sex, pain level or site or size of lesion. However, 5 were secondary procedures, 2 had multiple lesions, and 3 had had previous ruptured anterior cruciate ligaments. Arthroscopy and biopsy of 21 lesions so far after one year has shown mature articular cartilage in 2, and immature cartilage in 19. In all cases there was bonding of the repair tissue to the underlying bone. This study is already clarifying the role of ACT and mosaicplasty in the management of cartilage defects in the knee and also the necessity for the use of periosteal covering membrane.

The purpose of this study was to evaluate the influence of trochlear design in total knee replacement with and without patellar resurfacing.

Methods and Results: In 1992 a trial was set up, including all patients undergoing primary PFC (Johnson & Johnson) total knee replacement. Patients were randomised to either patellar resurfacing or retention. The patients were assessed using the American Knee Society rating, a clinical anterior knee pain score and BOA patient satisfaction score. Assessment was performed without knowing whether the patella had been resurfaced.

In July 1998 we began using the PFC Sigma. This incorporates a deeper trochlear groove with a 5° valgus angle.

We compared the results for the two types of prosthesis. In the PFC group there were 474 knees in 390 patients. Follow-up was from 2 to 9 years (mean 5.5 years). The overall prevalence of anterior knee pain) was 25.1% (58 knees) and 5.3% (13 knees) in the non-resurfaced group (n=231) versus the resurfaced group (n=243) respectively. Anterior knee pain became apparent in all cases within 18 months.

In the PFC sigma group there were 67 knees in 62 patients. Follow-up was from 18 months to 3 years (mean 2 years). The incidence of anterior knee pain was 0 in the resurfaced group (n=30) versus 37.8% (14 knees) in the non-resurfaced group (n=37). Knee scores were lower in the non-resurfaced groups for each prosthesis.

Conclusion: The prevalence of anterior knee pain was significantly higher in knees with non-resurfacing of the patella. The asymmetrical, deeper femoral groove improves anterior knee pain with the resurfaced patella but may contribute to it if not resurfaced. We recommend patellar resurfacing in all cases where technically possible.

The issue of preservation or sacrifice of the posterior cruciate ligament in total knee arthroplasty remains unresolved.

We report the results of 200 consecutive total knee arthroplasties performed at our hospital under the direction of the senior author. Pre-operatively, patients were randomly chosen to receive either a Kinemax (posterior cruciate retaining) or a Press-Fit-Condylar (posterior cruciate sacrificing) prosthesis. We implanted 97 Kinemax and 103 Press-Fit-Condylar prostheses which were prospectively followed-up by clinical and radiographic assessment. Review at mean follow-up of 2.7 years showed a satisfactory clinical result in both groups [Surace, et al., 1994].

We present the results of our further review, with maximum follow-up of over nine years (mean: 5.9 years). Revision of the implant has been performed in five knees (three Kinemax and two Press-Fit-Condylar). The polythene spacer had to be replaced in one patient with a Press-Fit-Condylar implant.

Patients were assessed with the Hospital for Special Surgery Knee Score and radiologically assessed with the Knee Society Roentgenographic Evaluation and Scoring System. Pre-operative demographics and disease states of the patients were similar, with an average Hospital for Special Surgery Knee Score of 63. At the latest assessment the average knee score was good (85). Remarkably, the mean knee score for the posterior cruciate sacrifice and the PCL groups remains similar (mean: 85). Radiographic evaluation demonstrated that the prosthetic components of both groups were in comparable alignment. The posterior cruciate ligament retained (Kinemax) patient group showed a mean 5.9 degrees of the valgus angle at the knee. The angle in the posterior cruciate ligament sacrifice (PFC implant) group was 6.2 degrees. Evaluation of the radiolucent depths below the femoral, tibial and any patella component showed a mean total depth of 1.5 mm (pcl retaining) and 1.7 mm (pcl sacrificing).

Our study presents a quantitative perspective of the results of total knee replacement with proven implant systems and performed in a general orthopaedic unit by both consultants and surgeons in training. The Kinemax (Howmedica) and Press-Fit-Condylar (DePuy Johnson and Johnson) implant systems have both previously demonstrated good results and continue to be available with little subsequent modification.

To our knowledge, there have been no other large prospectively randomised studies of posterior cruciate ligament preservation or sacrifice in total knee replacement.

We clinically and radiologically reviewed 79 uncemented PFC acetabular components inserted by our unit during a seven-year period, June 1991 to June 1998. Of these, 50 (63.3%) were primary and 29 (26.7%) were revision arthroplasties. The mean follow-up was five years (60 months), with a range of 12 to 95 months. Sixteen (20%) were excluded from the study, leaving 63 (26.7%) for review. Three (4.7%) cases were deemed to have failed (at 63, 69, 79 months), all of which were primary arthroplasties. One of them was found to be loose at revision and the other two cups had 2 mm of periacetabular radiolucency in only one zone, but had no definite evidence of loosening.

The remaining 60 (95.3%) cases showed no radiological evidence of migration of any cups, and no hip had a radiolucent line in all three zones of the acetabulum. Clinical review gave a mean Harris hip score of 96.5. Fifty (79.4%) reported no pain from the hip. One case (1.6%) had undergone recent revision of the stem, at which time the cup was found to be stable. Three (4.7%) reported slight, occasional pain. Another three (4.7%) described mild pain that did not compromise their average activities and was relieved by simple analgesia. Two cases (3.2%) complained of moderate pain that placed some limitations on their activities and required regular analgesia, and one elderly patient who had an ankylosed contralateral hip and ipsilateral sciatic nerve palsy described marked pain (1.6%), and these were considered poor outcomes. In all of these cases the cups were clinically and radiologically stable.

In conclusion, 81% of outcomes were excellent, painfree THRs. A further 4.75% had good and 4.75% fair results. 4.75% had poor outcomes and 4.75% of cases failed. We conclude that the PFC cup merits continued use and follow-up, and together with other uncemented cup designs, may produce benefits in the form of quality and longevity of results in total hip arthroplasty.

The purpose of this study was to evaluate the role of patellar resurfacing in total knee replacement surgery. We reviewed 48 patients who had undergone bilateral knee replacement with patellar resurfacing on only one side. Follow-up was from 18 months to 9.5 years and the patients were assessed using the Knee Society rating, a clinical anterior knee pain score and BOA patient satisfaction score. Patients were also asked specifically if they had a preference for either knee. Assessment was performed without knowing which patella had been resurfaced.

52.1% of patients favoured the resurfaced knee, 8% the unresurfaced knee and 39.9% had no particular preference. The overall prevalence of anterior knee pain was 8.3% in the resurfaced cases (3 mild, 1 moderate) and 27.1% in the unresurfaced knees (8 mild, 3 moderate, 2 severe). No significant difference was found between knee scores.

This study shows a significantly higher rate of anterior knee pain in unresurfaced patellae and preference for the resurfaced side.

We have treated 101 patients with scoliosis secondary to muscular dystrophy over a 13-year period; 64 had Duchenne’s muscular dystrophy, 33 spinal muscular atrophy and four congenital muscular dystrophy.

The patients underwent a modified Luque (87) or Harrington-Luque instrumentation (14) combined with a limited Moe fusion in all except 27 cases. A mean of 13 levels was instrumented. The mean preoperative sitting Cobb angle was 84° (10 to 150) and the mean postoperative angle 40° (52% correction). Most patients (96%) were able to discard their braces and there was a high level of patient satisfaction (89.6%).

Less correction was seen for severe curves, and there was a greater recurrence of postoperative pelvic tilt in those patients not instrumented to the sacrum. Although the incidence of minor or temporary complications was high, these occurred chiefly in the early high-risk patients with very severe curves and considerable pre-existing immobility.

The formation of restrictive adhesions around the musculotendinous unit after injury is one of the most vexing processes faced by the surgeon. In flexor tendons it has been shown that the synovial tissue is the source of aggressive fibroblasts which contribute to this process. Using a rabbit model, we have examined the effects of treating the synovial sheath with the antimetabolite 5-fluorouracil (5-FU) for five minutes. Inflammatory, proliferative and molecular markers were compared in the response of the treated and control tendons to injury. Compared with a control group we found that the proliferative and inflammatory responses were significantly reduced (p < 0.001) in the treated tendons. Not only was there a reduction in the cellular and cytokine response, but there also was a significant (p < 0.001) reduction in the level of activity of the known pro-scarring agent, transforming growth factor beta 1 (TGF-β1). These pilot studies indicate that the formation of restrictive adhesions may be modulated using a simple single-touch technique in the hope of producing a better return of function.

We reviewed the outcome of 146 Insall-Burstein II total knee replacements carried out in 121 patients over a period of nearly four years in a general orthopaedic unit. At a mean follow-up of ten years, 94 knees in 78 patients were available for review. Six patients (7 knees) were lost to follow-up and 37 (45 knees) had died.

The clinical outcome using the scoring system of the Hospital for Special Surgery (HSS) was excellent or good in 79% of patients, fair in 14% and poor in 7%. The mean preoperative HSS score was 31, improving to 79 at the latest review. Using the newer rating system of the Knee Society, the mean score at ten years was 87 and the mean functional score 56. The arc of flexion improved from a mean preoperative value of 88° to 100°. The 18 patients who had had a previous high tibial osteotomy were analysed separately and were found to have benefited equally from the operation. Nine prostheses were revised, giving a cumulative survival rate of 92.3% at ten years. Radiological evaluation of 104 radiographs showed radiolucent lines around ten tibial components, none of which required revision. Anterior knee pain was a significant problem.

Between 1989 and 1993 we implanted a matrix support prosthesis made of carbon fibre for the treatment of chronic painful articular defects of the patella in 27 patients. The mean period of follow-up was 33 months (11 to 54) with clinical and arthroscopic evaluation of the implant.

Overall, there were four excellent, three good, seven fair and 13 poor results. Nine patients subsequently had a patellectomy for persistent pain at a mean of 27 months after surgery (14 to 47). The mean visual analogue pain scores in those who retained their patella were 7.6 before operation and 5.5 at the time of the latest follow-up. Patient satisfaction for the entire group was 41%.

There appeared to be good incorporation of the prosthesis and a satisfactory ingrowth of fibrocartilage, but the poor results in 48% and low patient satisfaction discourage us from recommending the procedure for lesions of the articular cartilage of the patella. The consistent seeding of the joint with carbon-fibre debris and a histiocytic giant-cell reaction in the synovium are also a cause for concern.

We reviewed retrospectively the role of monitoring of somatosensory spinal evoked potentials (SSEP) in 99 patients with neuromuscular scoliosis who had had operative correction with Luque-Galveston rods and sublaminar wiring.

Our findings showed that SSEP monitoring was useful and that a 50% decrease in the amplitude of the trace optimised both sensitivity and specificity. The detection of true-positive results was higher than in cases of idiopathic scoliosis, but the method was less sensitive and specific and there were more false-negative results. In contrast with the findings in idiopathic scoliosis, recovery of the trace was associated with a 50% to 60% risk of neurological impairment.

Only one permanent injury occurred during the use of this technique, and any temporary impairment resolved within two months.

Aseptic loosening is seen in a significant proportion of cemented total hip replacements (THR). In a small subgroup of patients who suffer early loosening polyethylene debris is unlikely to be responsible. We recently reported one case of allergic contact dermatitis to N,N-dimethylparatoluidine (DMT), an accelerator used in bone cement. We have therefore investigated this using skin-patch tests to a variety of substances including metals, polyethylene and the separated individual components of Simplex cement.

We studied 70 patients, 15 with aseptic loosening less than two years after THR, 25 with satisfactory long-term cemented fixation, five with infected loosening of cemented THRs and 25 awaiting hip arthroplasty. We found seven positive reactions to DMT, all of them in patients with the rapid onset of aseptic loosening.

Allergy to DMT is recognised in the dental profession in respect of the ‘denture sore mouth’ syndrome, and could also be an occupational hazard since some industrial glues contain DMT. Our results suggest the need for awareness of possible previous dental or occupational exposure to the constituents of bone cement. We recommend the use of skin-patch testing in high-risk cases.

From 1982 to 1987, we randomised prospectively 413 patients requiring primary total hip replacements to receive either a Stanmore or Charnley prosthesis. They were reviewed by an independent observer in an attempt to correlate a number of factors including femoral head size with longevity. There were 213 Stanmore hips and 200 Charnley prostheses. At five to ten years (mean 6.5) 76 patients had died and 16 arthroplasties had required revision. Seven were radiologically loose in asymptomatic patients. There was only one case of deep infection.

We found no difference statistically in the clinical outcome or in the revision rate of 4% in the two types of prosthesis. The revision rate was greater for trainees than for senior operating surgeons, and there were recognisable technical errors in seven of the nine Stanmore, and four of the seven Charnley replacements which required revision. Retrospective radiological analysis of a random subset of 51 Charnley and 57 Stanmore femoral components showed no difference in femoral subsidence, but in 14 patients who had had bilateral replacements with one femoral component of each type, there was greater early subsidence of the Stanmore prosthesis.

Our results confirm that conventional cemented total hip replacements give acceptable results in a general teaching unit, and we found no evidence of any effect of the size of the femoral head on wear or loosening at five to ten years.

We report the theoretical basis of a method to measure axial migration of femoral components of total hip replacements (THR). The use of the top of the greater trochanter and a lateral point on the collar of the stem, allowing for variations of up to 10 degrees rotation of the femur in any direction between successive radiographs, gave a maximum error of 0.37 mm. At a more realistic 5 degrees rotational variation, the error was only 0.13 mm. These data were confirmed in an experimental study using digitisation of points and special software. We also showed that the centre of the femoral head, the stem tip, and the lesser trochanter provided less accurate landmarks. In a second study we digitised a series of radiographs of 51 Charnley and 57 Stanmore THRs; the mean migration rates were found to be identical. We then studied 46 successful stems with a minimum follow-up of eight years and 46 stems which had failed by aseptic loosening at different times. At two years, the successful stems had migrated by a mean of 1.45 +/- 0.68 mm, but the failed cases had a mean migration of 4.32 +/- 2.58 mm (p < 0.0001). Of the successful cases 76% had migrated less than 2 mm, while in the failed group 84% had migrated more than 2 mm. For any particular case migration of more than 2.6 mm at two years had only a 5% chance of continuing success and would therefore merit special follow-up. Only 24% of the eventually successful stems showed migration at the stem-cement interface, but this had happened in every failed stem. We conclude that it would be possible to evaluate a new cemented design of femoral stem over a two-year period by the use of our method and to compare its performance against the reported known standard of the Charnley and Stanmore designs.

We report a high rate of failure of the Ring polyethylene cementless cup caused largely by granulomatous osteolysis. We have reviewed 126 prostheses inserted from 1986 to 1992 at from 11 to 90 months after surgery. There was radiological evidence of osteolytic granulomas adjacent to the external surface of the cup in 32%, appearing on average at three years from operation. In a subgroup of 59 prostheses followed for at least four years the incidence of such changes was 54%. A total of 27 cups (22%) have required revision, 21 for granulomatous loosening at an average follow-up of five years. In the retrieved prostheses there was obvious polyethylene abrasion and histological examination confirmed the presence of polyethylene wear debris. We found no significant correlation of osteolysis with cup size, although smaller cups were predominant among those having revision.

We report a case in which the popliteal artery was divided during upper tibial osteotomy performed with the knee in 90 degrees of flexion. This position is believed to allow it to fall safely back from the tibia, but we could find no published confirmation. We used duplex ultrasonography in ten healthy volunteers to measure the distance from the popliteal artery to the posterior surface of the tibia at various degrees of flexion of the knee. Our results showed that in 12 of 20 knees the popliteal artery was closer to the tibia in 90 degrees of knee flexion than in full extension. Surgeons performing upper tibial osteotomy should be aware that flexing the knee does not protect the popliteal artery from injury.

We describe 83 knees (69 patients) which had had patellectomy for anterior knee pain (52), patellofemoral osteoarthritis (25) or comminuted fractures (6) between 1942 and 1978. The patients were questioned about their symptoms and the function of the operated knee 14 to 50 years after operation. In the group with anterior knee pain, 76% achieved good results and were satisfied with the operation. Only 54% of the osteoarthritis group had satisfactory relief of pain and most had progressive deterioration of function. Sixteen patients who had had unilateral patellectomy were assessed by dynamometry, ultrasound and radiography. The average quadriceps muscle power was 60% of that on the normal side although two patients had stronger muscles in their operated than in their unoperated legs.

The three-dimensional architecture of bovine articular cartilage collagen and its relationship to split lines has been studied with scanning electron microscopy. In the middle and superficial zones, collagen was organised in a layered or leaf-like manner. The orientation was vertical in the intermediate zone, curving to become horizontal and parallel to the articular surface in the superficial zone. Each leaf consisted of a fine network of collagen fibrils. Adjacent leaves merged or were closely linked by bridging fibrils and were arranged according to the split-line pattern. The surface layer (lamina splendens) was morphologically distinct. Although ordered, the overall collagen structure was different in each plane (anisotropic) a property described in previous morphological and biophysical studies. As all components of the articular cartilage matrix interact closely, the three-dimensional organisation of collagen is important when considering cartilage function and the processes of cartilage growth, injury and repair.

We measured joint position sense in the knee by a new method which tests the proprioceptive contribution of the joint capsule and ligaments. The leg was supported on a splint, and held in several positions of flexion. The subjects' perception of the position was recorded on a visual analogue model and compared with the actual angle of flexion. Eighty-one normal and 45 osteoarthritic knees were examined, as were 10 knees with semi-constrained and 11 with hinged joint replacements. All were assessed with and without an elastic bandage around the knee. There was a steady decline in joint position sense with age in subjects with normal knees. Those with osteoarthritic knees had impaired joint position sense at all ages (p less than 0.001). Knee replacement improved the joint position sense slightly (p less than 0.02); semi-constrained replacement had a greater effect than hinged replacement. The effect of an elastic bandage in subjects with poor position sense was dramatic, improving accuracy by 40% (p less than 0.001). It is proposed that reduced proprioception in elderly and osteoarthritic subjects may be responsible for initiation or advancement of degeneration of the knee.

We report the experimental use of three different biological implants to restore articular surface defects: glutaraldehyde-fixed bovine meniscal xenograft, glutaraldehyde-fixed bovine costal cartilage xenograft, and viable osteochondral allografts. The grafts were implanted in the knees of 19 goats who were allowed free-field activity and were studied for up to one year. The natural articular surfaces of meniscal fibrocartilage provided excellent articular surfaces at all times. Equally good articular surfaces were restored by host tissue growth covering costal cartilage grafts at six months, but by 12 months this surface had degenerated. The majority of the allografts survived and integrated with the host at six months, but many showed signs of failure at 12 months. Only three out of seven ungrafted defects healed completely at six months and the healed surfaces were degenerating at 12 months.

We reviewed 31 of 33 consecutive patients with intra-articular fractures of the knee at 6 to 22 years (average 14). Of these, 77% had excellent or good results; the others had various degrees of degenerative osteoarthritis. There was no significant difference between the results after surgical or conservative treatment. Secondary degeneration was not related to cause or type of fracture, but its incidence increased with the patient's age at the time of injury, though not with the length of follow-up. Early mobilisation appeared to be beneficial in preventing later degenerative changes.

A prospective study of 120 consecutive total hip replacements showed that deep suction drains produced maximal drainage volumes in the first 24 hours. Their continued presence resulted in minimal further drainage, did not reduce the likelihood of haematoma formation and led in some cases to the spread of skin organisms into the wound.

Computerised tomography of the lumbar spine was performed on 22 patients with clinical evidence of prolapse of an intervertebral disc and normal or equivocal radiculograms. Of 11 patients with positive scans who had an operation the presence of pathology was confirmed in 10. Although CT scanning is always helpful in diagnosing disc disorders, where facilities are scarce (as in Great Britain) it is best employed in patients with negative or non-contributory radiculography.

Experimentally produced fractures in long bones studied by light and electron microscopic histochemistry were found to heal by a process of enchondral calcification. There was intense proliferation in the cells of the cambium layer of the periosteum, with differentiation to chondroblasts and osteoblasts, suggesting that this layer was the primary tissue responsible for development of the callus. Cytoplasmic processes of the hypertrophic chondrocytes appeared to bud and produce matrix vesicles. Alkaline phosphatase activity was detected along the plasma membrane of the hypertrophic chondrocytes and around the matrix vesicles, before any signs of mineral deposition. Calcification took place by deposition of hydroxyapatite crystals in and around these matrix vesicles which frequently showed alkaline phosphatase activity. It is suggested that there is a close functional association between alkaline phosphatase activity and calcification in the process of fracture healing, which is another type of enchondral calcification mediated by matrix vesicles.

Minor degrees of malalignment of the patella and anatomical abnormalities including a flattened sulcus angle and an increased ratio between patellar tendon length and patellar length (PT:P) have been suggested as predisposing factors in the causation of chondromalacia patellae, as well as patellar instability. In order to confirm or refute this hypothesis a prospective study has been performed comparing the congruence and sulcus angles and the PT:P ratio in a group of 35 patients with chondromalacia confirmed by arthroscopy and a group of 33 patients with instability, with those of a group of 50 knees in normal volunteers. While there was a statistically significant correlation between an increased sulcus and congruence angle and a high-riding patella in patients with instability, no correlation could be identified in patients with idiopathic chondromalacia.

Allografts of intact cartilage, isolated chondrocytes and cultured chondrocytes taken from the epiphysial growth-plate and from the articular surface of immature rabbits were inserted into full thickness defects in the tibial articular surface of 160 mature rabbits. In the contralateral knees, which were used as controls, similar defects were made but no grafts were inserted. Grafts were followed up for periods of up to one year after transplantation. Both intact articular and intact growth-plate grafts produced significantly better repair than that seen in control ungrafted defects in normal joints (P less than 0.01 and P less than 0.05 respectively) and in arthritic joints (P less than 0.01). Cultured chondrocytes cut to a precise fit also produced significantly better repair than ungrafted defects in arthritic joints (P less than 0.05).

Full thickness samples of articular cartilage were removed from areas of chondromalacia on the medial and "odd" facets of the patellae of 21 adults and examined by histology, autoradiography and electron microscopy. Surface fibrillation, loss of superficial matrix staining and reduced 35SO4 labelling was seen, with little change in the deep zone. Ten cases showed "fibrous metaplasia" of the superficial cartilage with definite evidence of cell division and apparent smoothing of the surface. Scattered chondrocyte replication appeared to occur in the surrounding intact cartilage. The findings suggest that early lesions in chondromalacia patellae may heal either by cartilage or fibrous metaplasia and that this may account for the resolution of clinical symptoms.