To determine the risk of total knee replacement (TKR) for primary osteoarthritis (OA) associated with overweight/obesity in the Australian population.

This population-based study analyzed 191,723 cases of TKR collected by the Australian Orthopaedic Association National Joint Registry and population data from the Australian Bureau of Statistics. The time-trend change in incidence of TKR relating to BMI was assessed between 2015-2018. The influence of obesity on the incidence of TKR in different age and gender groups was determined. The population attributable fraction (PAF) was then calculated to estimate the effect of obesity reduction on TKR incidence.

The greatest increase in incidence of TKR was seen in patients from obese class III. The incidence rate ratio for having a TKR for obesity class III was 28.683 at those aged 18-54 years but was 2.029 at those aged >75 years. Females in obesity class III were 1.7 times more likely to undergo TKR compared to similarly classified males. The PAFs of TKR associated with overweight or obesity was 35%, estimating 12,156 cases of TKR attributable to obesity in 2018. The proportion of TKRs could be reduced by 20% if overweight and obese population move down one category.

Obesity has resulted in a significant increase in the incidence of TKR in the youngest population in Australia. The impact of obesity is greatest in the young and the female population. Effective strategies to reduce the national obese population could potentially reduce 35% of the TKR, with over 10,000 cases being avoided.

The 2020 London International Hamstring Consensus meeting was convened to improve our understanding and treatment of hamstring injuries.

The multidisciplinary consensus panel included 14 International specialists on the management of hamstring injuries. The Delphi consensus process consisted of two rounds of surveys which were completed by 19 surgeons from a total of 106 participants. Consensus on individual statements was regarded as over 70% agreement between panel members.

The consensus group agreed that the indications for operative intervention included the following: gapping at the zone of injury (86.9%); high functional demands of the patient (86.7%); symptomatic displaced bony avulsions (74.7%); and proximal free tendon injuries with functional compromise refractory to non-operative treatment (71.4%). Panel members agreed that surgical intervention had the capacity to restore anatomy and function, while reducing the risk of injury recurrence (86.7%). The consensus group did not support the use of corticosteroids or endoscopic surgery without further evidence.

These guidelines will help to further standardise the treatment of hamstring injuries and facilitate decision-making in the surgical treatment of these injuries.

Aims

Despite the increase in the surgical repair of proximal hamstring tears, there exists a lack of consensus in the optimal timing for surgery. There is also disagreement on how partial tears managed surgically compare with complete tears repaired surgically. This study aims to compare the mid-term functional outcomes in, and operating time required for, complete and partial proximal hamstring avulsions, that are repaired both acutely and chronically.

Osteoarthritis (OA) is traditionally believed to affect the osteochondral unit by wear-and-tear from the superficial zone to the deep zone of cartilage and extended to subchondral plate. Obesity is commonly considered as a risk of OA development and hence total knee replacement (TKR), but the mechanism remains unclear. We hypothesized that obesity accelerated OA development by deteriorating tidemarks and increasing bone remodelling. 616,495 cases of TKR for OA from Australia and British joint replacement registries were collected, and data indicated that patients with higher BMI had TKR at earlier age. Specifically, patients with BMI ≤25kg/m² showed 8 years younger than patients with BMI ≥40kg/m² (P<0.0001) when they received TKR. We next examined tibia plateaus of 88 knee OA patients by micro-CT and histomorphometry. Linear regression showed that less cartilage degradation was associated with increased BMI in the load-bear compartment (p<0.05), while 58.3% of patients with BMI≥40kg/m² demonstrated a clear anatomical separation close to tidemarks filled with fibrosis, erythrocytes and bone fragments (compared to BMI ≤25kg/m² group: 7.7%, p<0.01). In subchondral bone, elevated bone formation was associated with increased BMI, as higher thickness of osteoid (p<0.01), percent osteoid volume (p<0.01), percent osteoid surface (p<0.01) were found in obese patients. However, no alteration of bone resorption and microstructural parameters was found to be associated with BMI. We suspected that the abnormal loading in knee joint due to high BMI led to the direct deterioration of binding site of osteochondral unit, which might be the mechanism of the rapid progression in obesity-related OA.

Introduction

Training the next generation of surgeon's forms part of routine Consultant practice. Stress causes activation of the Autonomic Nervous System and this can be directly measured using heart rate (HR). Training time is limited with pressures from EWTD and management and efficiency targets. The aim of this study was to assess whether being an orthopaedic trainer is more stressful than performing the surgery.

Obesity is a global epidemic of 2.1 billion people and a well known cause of osteoarthritis. Joint replacement in the obese attracts more complications, poorer outcomes and higher revision rates. It is a reversible condition and the fundamental principles of dealing with reversible medical conditions prior to elective total joint replacement should apply to obesity. The dilemma for orthopaedic surgeons is when to offer surgery in the face of a reversible condition, which if treated may obviate joint replacement and reduce the risk and severity of obesity related disease in both the medical arena and the field of orthopaedics.

Objectives

The most concerning infection of allografts and operative procedures is methicillin resistant Staphylococcus aureus (MRSA) and no current iontophoresed antibiotics effectively combat this microbe. It was initially hypothesised that iontophoresis of vancomycin through bone would not be effective due to its large molecular size and lack of charge. The aim of this study was to determine whether this was a viable procedure and to find the optimum conditions for its use.

This article provides an overview of the role of genomics in sarcomas and describes how new methods of analysis and comparative screening have provided the potential to progress understanding and treatment of sarcoma. This article reviews genomic techniques, the evolution of the use of genomics in cancer, the current state of genomic analysis, and also provides an overview of the medical, social and economic implications of recent genomic advances.

Purpose of the study

To determine the outcome after the Semi-tendinosis tendon was used in reconstruction of the Medial Patella-femoral ligament using a fixed dynamic stabilising structure.

There is ongoing debate on the benefits of fixed versus mobile bearing Unicompartmental Knee Replacement (UKR). We report the results from a randomised controlled trial comparing fixed and mobile bearing of the same UKR prosthesis. Forty patients were randomized to receive identical femoral components and either a fixed or mobile bearing tibial component. At 6.5 years follow-up 37% of the mobile bearing design had been revised and 14% for the fixed bearing design. The main reasons for revision were pain and loosening. These results were compared with data from The Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) that show a cumulative percent revision of 24.2% for the mobile bearing Preservation UKR at 6.5 years. All locally explanted mobile bearings were examined microscopically, and 83% demonstrated significant backside wear. Constraint on the undersurface of the bearing coupled with a congruent upper surface may have contributed to the excessive revision rate. This is the first randomised controlled trial examining mobile and fixed variations of the same UKR prosthesis and shows this design of UKR with the mobile bearing has an unacceptably high revision rate and patients with this knee design should be closely monitored.

Richard Carey Smith is an orthopaedic oncology surgeon with fellowship training in the UK, USA, Australia and Canada, and has worked in Zambia, Zimbabwe and Papa New Guinea. David Wood is head of the University Department of Orthopaedics in Perth, Western Australia. He did his masters in Africa, and first experienced Papa New Guinea on his medical elective, starting a lifelong commitment to medical aid work there.

Aim

The aim of this study was to compare a single-incision minimally invasive (MI) posterior approach with a standard posterior approach in a double-blind prospective randomised controlled trial.

Introduction: Chondral injuries of the knee are commonly seen at arthroscopy, yet there is no consensus on the most appropriate treatment method. However, untreated cartilage injury predisposes to osteoarthritis contributing to pain and disability. For cell-based cartilage repair strategies, an ex vivo expansion phase is required to obtain sufficient cells for therapeutic intervention. Although recent reports demonstrated the central role of oxygen in the function and differentiation of chondrocytes, little is known of the effect of physiological low oxygen concentrations during the expansion of the cells and whether this alters their chondrogenic capacity.

Methods: Articular mouse chondrocytes were prepared from the distal femoral condyles of adult mice and chondrocytes were liberated by collagenase type II treatment. Cells were cultured in RPMI 1640 media in monolayer under normoxic or hypoxic conditions (5% O2). Chondrogenic potential was subsequently assessed by plating the cells under micromass conditions and glycosaminoglycan deposition was determined by alcian blue staining. Having determined that oxygen tension infiuences murine chondrocyte expansion and differentiation, similar studies were conducted using adult human chondrocytes taken from knee arthroplasty off-cuts, and Aggrecan (ACAN) gene expression was analyzed using real-time quantitative PCR.

Results: Cellular morphology of cells from mouse articular cartilage was improved in hypoxic culture, with a markedly more fibroblastic appearance seen after greater than 2 passages in normoxic conditions. Micromass cultures maintained in hypoxic conditions demonstrated stronger staining with alcian blue, indicating stronger expression of cartilage-associated glycosaminoglycans. Expansions of human chondrocytes under hypoxic conditions led to an ~ 2-fold increase in the expression of ACAN in comparison to cells in normoxic conditions. Differentiation of passage 2 chondrocytes under hypoxic conditions also improved the expression of ACAN when compared to culturing under normoxia. Ten day hypoxic cultures exhibited an ~ 5-fold increase in ACAN expression in comparison to normoxic cultures. Interestingly, ACAN expression normoxic-cultured cells could be increased by > 4-fold by transfer to hypoxic conditions.

Conclusions: In vivo, the chondrocytes are adapted to an avascular hypoxic environment. Accordingly, applying 5% O2 in the expansion phase in the course of cell-based cartilage repair strategies may more closely mimic the normal chondrocyte microenvironment and may result in a repair tissue with higher quality by increasing the content of glycosaminoglycans.

Introduction: Articular cartilage has limited capacity for regeneration. Tissue engineering strategies offer future hope for cartilage replacement and repair. In an attempt to mimic functional native cartilage for tissue repair, current research focuses on construct/implant designs that simulate an embryonic like microenvironment to promote cellular differentiation along a chondrogenic lineage. The aim of the present study was, for the first time, to illustrate the differences between human neonatal and adult chondrocytes along with bone marrow stromal cells (HBMSCs) to differentiate the factors that promote chondrogenesis and maintain functional homeostasis.

Material and Methods: Adult chondrocytes, neonatal chondrocytes and HBMSCs were cultured in monolayers for 1, 2 and 3 weeks in basal or chondrogenic media. Expression of transcription factor Sox9, Aggrecan (ACAN) and Collagen type II (COL2A)was compared via real time polymerase chain reaction (q-PCR). Alternatively, cells were seeded onto 3D PLGA scaffolds and cultured in vitro for 3 and 6 weeks in basal or chondrogenic media. Paraffin sections of the constructs were stained with Alcian blue/ Sirius red and expression of Collagen type II and Aggrecan was visualised via immunohistochemistry.

Results: For monolayer cultures of all three cell types, at week 1, expression of all three genes was down regulated in basal medium compared to levels in chondrogenic medium. By week 2, q-PCR revealed an increased expression of Col2A in chondroinduced neonatal chondrocytes compared to adult chondrocytes and HBMSCs. A steady increase in SOX9 expression was observed with time in all three cell types in chondrogenic medium. However, SOX9 expression in week 2 was higher for each cell type in basal medium compared with chondrogenic medium. ACAN expression by HBMSCs was greatly enhanced compared with that of neonatal and adult chondrocytes after 2 weeks in chondrogenic medium. By week 3, basal cultures of all cell types showed an overall lower level of gene expression compared with chondroinduced cells. 3D constructs revealed the formation of cartilage like tissue for all three cell types with the presence of a prominent superficial layer and middle zone in the chondroinduced constructs. A superficial layer was also observed in constructs cultured in basal media but there was no evidence of any other characteristic zones. A fibrous capsule had formed around the chondroinduced tissue by week 6. Thinnest capsules were observed for constructs seeded with neonatal cells, with thickest capsules in constructs seeded with HBMSCs. Immunohistochemistry revealed a greater presence of aggrecan and type II collagen in the chondroinduced constructs compared to those cultures in basal media.

Conclusion: This comparative study indicates a major difference between the microenvironment of human neonatal chondrocytes, adult chondrocytes and HBMSCs. The expression of high amounts of COL2A and ACAN (considered to be middle to late markers in chondrogenesis) in week 1 in neonatal chondrocytes indicates a difference in temporal gene expression during chondrogenesis or in maintaining cartilage homeostasis. The study provides potentially useful information to inform cell-based therapies for cartilage regeneration.

Introduction: Treatment of dual compartment osteoarthritis remains controversial, with conjecture over whether Uni-Compartmental (‘UKA’) or Total Knee Arthroplasty (‘TKA’) is more appropriate for patients with patello-femoral disease. The ‘Journey Deuce’ 2/3 Knee Arthroplasty (‘2/3 Knee’) (Smith & Nephew) is a bi-cruciate retaining prosthesis designed to treat this subgroup of patients with both antero-medial and patello-femoral disease.

We have conducted a prospective, observational clinical trial of 34 patients with dual compartment osteoarthritis of the knee treated with a 2/3 Knee.

Aims: To assess the safety and clinical efficacy outcomes of the 2/3 Knee.

Method: All patients pre-op leg alignment films, as well as MRI or arthroscopy to confirm the inclusion criteria of dual compartment osteoarthritis with a preserved lateral compartment and intact cruciate ligaments. All operations were performed by a single surgeon (DW) using computer assisted surgery (CAS) and a minimally invasive technique (MIS) at a local university affiliated private hospital (HPH).

Exclusion criteria included obesity, inflammatory arthritis and a fixed flexion deformity > 10 degrees.

Subjective outcome measures included Oxford Knee Scores (OKS) and EQ-5D Scores. RSA beads were implanted at surgery to detect loosening, micro-motion and prosthesis wear. Gait analysis was conducted at 1 year post op in a subgroup of patients.

Results: Follow up ranged from 6 months to 2 years. There have been no early failures requiring complete revision. The first 23 knees (18 patients) did not have primary resurfacing of the patella. Some of these patients suffered palpable and audible patello-femoral crepitus, with a subgroup (17%, 4 knees-3 patients) having associated anterior knee pain. This subgroup had revision procedures to resurface their patellae with resolution of their symptoms. All subsequent patients have had primary patella resurfacing with no incidence of Significant crepitus or anterior knee pain.

The patients have recorded Significant improvement in their Oxford Knee Scores at 6 months (mean reduction all patients: 17.3, resurfaced 20).

Early RSA results have not detected Significant migration to indicate early loosening. Gait analysis has shown that patients return to approximate normal rather than pre-operative gait.

Conclusions: Although longer follow up is required the 2/3 Knee appears a safe and effective treatment option for patients with dual-compartment osteoarthritis; with rehabilitation, function and gait tending towards that seen in UKA rather than TKA.

It is essential that patients undergo primary patella resurfacing to prevent crepitus and associated anterior knee pain.

A study comparing clinical outcomes of 2/3 Knee vs TKA is underway at our institution.

Articular cartilage has limited regenerative potential. Regeneration via autografts or cell therapy is clinically efficacious but the extent of regenerative success depends upon use of an appropriate cell source. The aim of this study was to compare the proliferative and chondrogenic potentials of three human cell types (human bone marrow stromal cells - HBMSCs, neonatal and adult chondrocytes) commonly used in cartilage tissue engineering.

HBMSCs, neonatal and adult chondrocytes (passage 2) were cultured in basal and chondrogenic media. At 2, 4 and 6 days, the cells were analysed for morphology and doubling time. Alkaline phosphatase specific activity (ALPSA) was quantified for each group at 2, 4 and 6 weeks. Chondrogenic potential of each cell type was assessed via a pellet culture model. Cryosections were stained with Alcian blue/Sirius Red.

HBMSCs showed either elongated or polymorphic phenotypes, with a doubling time of 40 h. Neonatal chondrocytes showed a uniform spindle shape and had the shortest doubling time (16 h). Adult chondrocytes, were also spindle shaped, though slightly larger than the neonatal cells, with a longer doubling time of 22 h. Expression of ALPSA in basal media was of the order HBMSCs > adult chondrocytes > , neonatal chondrocytes. In chondrogenic culture, this order changed to adult chondrocytes > HBMSCs > neonatal chondrocytes. In 3D pellet cultures, all three cell types stained positive for Alcian Blue and showed the presence of chondrocyte-like cells enclosed in lacunae.

This comparative study suggests that neonatal chondrocytes are the most proliferative with lowest ALP expression. However, in terms of clinical applications, HBMSCs may be better for cartilage regeneration given their lower ALP expression under chondrogenic conditions when compared with adult chondrocytes under the same conditions. The study has provided information to inform clinical cell therapy for cartilage regeneration.

Calcitonin has been recently shown to have a direct protective effect on articular cartilage against joint degenerative disease. It has been proposed that calcitonin might act through the calcitonin receptor (CTR) to activate the cyclic AMP pathway and protect type II collagen degradation. In this study, we examined the presence of the CTR in human articular cartilage and chondrocytes and investigated the potential pharmacological effects and transduction pathway of salmon calcitonin in human chondrocytes.

Five human articular cartilage samples were examined for the expression of the CTR by polymerase chain reaction (PCR), immunostaining and Western blotting. Cyclic AMP levels in human chondrocyte stimulated with salmon calcitonin were measured by ELISA. The effect of salmon calcitonin on the gene expression profiles, including aggrecan, type II collagen, matrix metalloproteinase (MMP)-1, MMP-3 and MMP-13, of human chondrocytes was also examined by Real-time PCR.

It was shown that CTR was not detectable in human cartilage and chondrocytes. The cAMP level in human chondrocytes in vitro was significantly increased by forskolin (100μM) by > 10 fold (P< 0.001), but was not induced by salmon calcitonin (10^-7M, 10^-8M, 10^-9M). Real-time PCR demonstrated that salmon calcitonin tended to reduce the gene expression of MMPs, yet without statistical significance. In contrast to previous reports, our data showed that human cartilage and chondrocytes do not express calcitonin receptors. There was no direct effect of salmon calcitonin on human chondrocytes.

The result suggests that the chondroprotective effect of calcitonin observed in vivo may be indirect via its effect on subchondral bone resorptive activity.

Introduction: There are no current estimates of the risk of transmission of HIV, HBV, HCV, or HTLV by musculoskeletal tissue transplantation. Such accurate data would be helpful to determine the effectiveness of current and proposed screening and processing procedures, and contribute to increased confidence in the use of musculoskeletal tissue products.

Methods: The prevalence rates of HIV, HBV, HCV, and HTLV were determined from 12.245 musculoskeletal tissue donors from three bone tissue banks across Australia from the period 1993 to 2004. The incidence rates among tissue donors were estimated by comparing the data with age-specific incidence rates of first-time blood donors. We estimated the probability of a tissue donor was within the window period when infection was undetected by serological screening procedures by the modified incidence-window period model. Further we calculated the projected probability of viremia with the addition of nucleic-acid amplification testing (NAT).

Results: The prevalence (per 100,000 persons) of confirmed positive tests among musculoskeletal tissue donors was 169.15 for HIV, 427.68 for HBV, 534.63 for HCV, and 121.66 for HTLV. This is greater than the prevalence among first-time blood donors during the same period (6.47 for HIV, 136.00 for HBV, 215.29 for HCV, and 3.46 for HTLV). The incidence rate among musculoskeletal donors were estimated to be 15.81, 0.68, 3.53, and 4.85 per 100,000 person-years, respectively. The estimated probability of viremia (per 100,000 persons) at the time of donation was 1.38 for HIV, 0.46 for HBV, 1.82 for HCV, and 0.85 for HTLV. These estimations would be even lower with the addition of NAT – 0.57, 0.23, and 0.20 respectively.

Conclusions: The prevalence and incidence of HIV, HBV, HCV, and HTLV among musculoskeletal tissue donors, although low are significantly higher than those of first-time blood donors. Current screening and processing measures are effective, though the probability of viremia can be reduced further by nucleic-acid amplification testing.

Patella instability can be a disabling condition predominately affecting younger patients, restricting activity and potentially leading to premature osteoarthritis. We describe and evaluate a new technique of stabilising the joint.

Between November 2000 and January 2002 we operated on 24 unstable knees (belonging to 23 patients). All patients had failed a course of conservative treatment and the average number of dislocations pre-operatively was 7. All patients had an extra-synovial lateral release and stabilisation by harvesting the semitendinosus tendon which was then tunnelled through a vertical hole in the patella, under the vastus medialis, wrapped around the adductor magnus and tied to itself at the lower border of the patella.

The patients were assessed clinically and radiologically at an average of 19 months, following the procedure.

There were 19 knees assessed: 13 female /6 male, 10 left /9 right, average age 22 years. 13 patients had retro-patella chondral damage none had meniscal or cruciate pathology. The visual analogue score increased from 4 pre-op to 7.5 after operation. The Kujala patello-femoral score was 74 post procedure. 53% of patients described their knee as excellent, 47% as good. Only one patient has re-dislocated to date (single event). There were no specific risk factors.

Conclusion: Stabilisation of an unstable patello-femoral joint with a semitendinosus loop is a highly successful procedure with good patient satisfaction. We are also happy to use this procedure in the skeletally immature as its use does not preclude a later realignment procedure, should it be indicated.

We treated 34 patients with recurrent dislocation of the hip with a constrained acetabular component. Roentgen stereophotogrammetric analysis was performed to assess migration of the prosthesis.

The mean clinical follow-up was 3.0 years (2.2 to 4.8) and the radiological follow-up was 2.7 years (2.0 to 4.8). At the latest review six patients had died and none was lost to follow-up. There were four acetabular revisions, three for aseptic loosening and one for deep infection. Another acetabular component was radiologically loose with progressive radiolucent lines in all Gruen zones and was awaiting revision. The overall rate of aseptic loosening was 11.8% (4 of 34). Roentgen stereophotogrammetric analysis in the non-revised components confirmed migration of up to 1.06 mm of translation and 2.32° of rotation at 24 months. There was one case of dislocation and dissociation of the component in the same patient. Of the 34 patients, 33 (97.1%) had no further episodes of dislocation.

The constrained acetabular component reported in our study was effective in all but one patient with instability of the hip, but the rate of aseptic loosening was higher than has been reported previously and requires further investigation.

Introduction Primary and revision total hip surgery in the face of poor neuromuscular function, cognitive impairment or recurrent dislocation are fraught with complications. A useful option for such cases is the constrained acetabular component, or “captive cup”. We present the largest series reported to date, and use radiostereometric analysis (RSA) to assess cup migration.

Method Between February 1999 and September 2003 133 patients (141 hips) were identified as high risk of dislocation and were treated with a constrained acetabular component. One hundred and twenty cases were revision arthroplasties and 21 were primary replacements. Patients were assessed pre-operatively (WOMAC, Harris Hip Scores and SF-36). Defects were reconstructed with allograft (massive, morsellised or strut) where required. Most components were inserted into uncemented metal cups. Radiostereometric beads were inserted. Post-operatively patients were followed up regularly and clinical scores repeated. Radiostereometric analysis (RSA) was performed at 6 months, and then annually to assess prosthesis migration.

Results Mean follow-up was 3.1 years (range 1 – 5.6 years). At last review 26 patients had died, and 7 were lost to follow-up. There were 8 revisions for cup loosening. There were 5 dislocations and 2 dissociations in 6 patients. There was a statistically significant improvement in WOMAC and Harris Hip scores. RSA confirmed cup migration was greater than for non-captive cups, but was nevertheless minimal. Interestingly there was no statistically significant difference at 6, 12 and 24 months suggesting most migration occurs early on.

Conclusion Our results suggest the “captive cup” is an effective and safe option for the treatment of primary and revision arthroplasty in those at high risk of dislocation.

Compartment syndrome is a rare complication of total knee arthroplasty that requires early recognition and prompt decompression in order to prevent long-term disability. We have found only one previous case report in the literature. We present a series of seven cases from four hospitals and five surgeons. Six of the cases resulted in the loss of at least one compartment, and one resulted in amputation. Four of the cases resulted in legal action.

We suggest that important risk factors contributing to the development of this condition include complex surgery, soft-tissue compromise, previous surgery, and possibly vascular disease. Delay in the diagnosis and hence delay in decompression was common in our series, and in five cases appeared to be related to the use of a postoperative epidural infusion for pain relief. The presence of associated neurological compromise may have also been a significant factor in the delay to diagnosis in two cases.

Introduction: Primary and revision total hip surgery in the face of poor neuromuscular function, cognitive impairment or recurrent dislocation are fraught with complications. A useful option for such cases is the constrained acetabular component, or “captive cup”. We present the largest series reported to date, and use radiostereometric analysis (RSA) to assess cup migration.

Method: Between February 1999 and September 2003 126 patients were identified as high risk of dislocation and were treated with a constrained acetabular component. One hundred and sixteen cases were revision arthroplasties and 10 were primary replacements. Patients were assessed pre-operatively (WOMAC, Harris Hip Scores and SF-36). Defects were reconstructed with allograft (massive, morsellised or strut) where required. All components were inserted into uncemented metal cups. Radiostereometric beads were inserted. Post-operatively patients were followed up regularly and clinical scores repeated. Radiostereometric analysis (RSA) was performed at 6 months, and then annually to assess prosthesis migration.

Results: Mean follow-up was 3.1 years (range 1 – 5.6 years). At last review 8 patients had died, and 2 were lost to follow-up. There were 7 revisions: 3 for infection, 2 for periprosthetic fractures, and 2 for aseptic loosening. There was one case of cup disassociation successfully treated with open reduction. There have been no further dislocations. There was a statistically significant improvement in WOMAC and Harris Hip scores. RSA confirmed cup migration was greater than for non-captive cups, but was nevertheless acceptable: 0.16mm medially, 0.47mm proximally, 0.16mm posteriorly. Interestingly there was no statistically significant difference at 6, 12 and 24 months suggesting most migration occurs early on.

Conclusion: Our results suggest the “captive cup” is an effective and safe option for the treatment of primary and revision arthroplasty in those at high risk of dislocation. RSA analysis confirms minimal prosthesis migration.

Introduction and aim: Early symptomatic osteoarthritis (OA) of the knee poses a difficult challenge to orthopaedic surgeons, particularly in the presence of malalignment. Most surgical options are palliative. Our aim was to assess combined high tibial osteotomy (HTO) and matrix-induced autologous chondrocyte implantation (MACI) as a curative option.

Methods Patients with localised medial compartment OA and varus malalignment were identified. Suitability for the above procedure was confirmed at arthroscopy and specimen taken for culture. HTO and MACI procedures were performed in one sitting by a single surgeon. Patients received three months rehabilitation and function was assessed preoperatively and at three-monthly intervals.

Results Twelve patients were identified: nine male; average age 46 years (27–58). Mean varus deformity was 6 degrees. Two patients also had evidence of osteochondritis dissecans, and two early patello-femoral OA. Eight patients had had previous surgery to the knee.

Eleven patients had a lateral closing wedge osteotomy; the medial opening wedge was performed in a case of leg shortening. Mean operation duration was 72 minutes (60–90). The graft was fixed with fibrin glue in all cases, and augmented with stitches or vicryl pins in five cases. Mean defect size was 6.2cm2 (2–12). There were three complications: one DVT, a haemarthrosis and a graft detachment.

Average follow-up was 16 months. MRI scans at three months show oedematous tissue at the defect sites, contrasting with the fluid filled defects seen preoperatively. Scans at one-year show hyaline-like cartilage infill with similar signal characteristics to native hyaline cartilage. Six minute walk test and knee injury and osteoarthritis outcome score indicate significantly improved functional capacity at six months and one year.

Conclusions Preliminary results suggest combined HTO and MACI is successful for young patients with early OA associated with malalignment.

Introduction: Iontophoresis is a method to introduce antibiotic molecules into allograft bone using an electrical potential; the antibiotics may then be released at therapeutic levels for extended periods of time. This is the first report of iontophoresed allograft implantation into patients.

Method: A method of loading tubular sections of cortical bone was used in theatre prior to implantation. Postoperative serum, drain and allograft antibiotic assays were performed. Patients were followed-up clinically and radiologically. All patients who received a bulk segmental allograft from June 1997 were entered into the trial.

Results: Since June 1997, 35 patients have received 37 allografts. Indications for allograft insertion were limb salvage for tumour (18), and poor bone stock associated with infection (11), periprosthetic fracture (6), aseptic loosening (1) and recurrent dislocation of total hip replacement (1). Mean follow-up is 3.3 years, and no patients have been lost to follow-up. One patient received two allografts in different sites and one had an allograft exchange. There has been one superficial wound infection and one deep infection. The latter patient was revised to another iontophoresed allograft and has had no recurrence at 34 months. One allograft has been revised to a vascularised fibular graft and allograft exchange following fracture of metal fixation. There was one case of persistent non-union in a knee arthrodesis which was treated after 21 months by removal of the intramedullary fixation and use of an Illizarov frame. The allograft was not revised. All other allografts are in situ with no complications related to the allograft. Eleven patients had pre-existing proven infections. None of these patients have been re-infected to date. Therapeutic gentamicin and flucloxacillin levels were detected in drain fluid samples post-operatively.

Conclusions: Iontophoresis is a safe and inexpensive technique that delivers high local dose of antibiotic, which may reduce infection in avascular allograft bone.

Introduction We believe minimally invasive surgery should be defined by the extent of soft tissue dissection rather than incision length. We describe a new technique that is truly soft-tissue sparing and report our early results.

The surgical approach The landmarks for the incision are identified and a 6–8cm oblique incision is made over the posterior aspect of the greater trochanter. Longer incisions are required in more difficult cases. Piriformis and the proximal insertion of gluteus maximus are preserved. After implant insertion, meticulous capsular repair is performed through drill holes into bone to reconstruct the posterior envelope. There are no restrictions to mobility. No specialised instruments are required.

Method The standard posterior approach (group 1) was compared with the PSMI approach (group 2) in a prospective cohort study of 200 consecutive patients over 60 years of age. In the standard approach the external rrotators were dettached. The capsule was repaired to bone, and the piriformis tendon reattached to the Gluteus Medius tendon. Routine restrictions to mobility were imposed. Patients were scored pre-operatively and followed up prospectively, by a blinded observer.

Results Demographics and functional scores were similar. Mean operation time was about 1 hour in both groups. Mean incision length was 21.5 cm (range 15 – 25) in group 1 and 8.4 cm (range 6 – 16) in group 2. Mean blood loss in group 1 was significantly higher than group 2 (P< 0.0001, 95%CI 191–547). Mean inpatient stay was 8.0 days in group 1, and 4.8 days in group 2 (P< 0.0001, 95%CI 3.4–6.0).

Minimum follow-up was 3 years in group 1 and 1.5 years in group 2. There were 3 dislocations in group 1, and none in group 2. There were 2 re-operations in both groups. The relative improvement in WOMAC scores was significantly greater in group 2 at 3 months and 1 year (P< 0.05).

Conclusion The PSMI approach to the hip is truly soft-tissue sparing. It is safe and relatively easy to perform. The stability and minimal morbidity allow early mobilisation. This is the first study to suggest the benefits of minimally invasive surgery may be prolonged. Cosmesis is a by-product rather than primary objective.

We carried out a blinded prospective randomised controlled trial comparing 2-octylcyanoacrylate (OCA), subcuticular suture (monocryl) and skin staples for skin closure following total hip and total knee arthroplasty. We included 102 hip replacements and 85 of the knee.

OCA was associated with less wound discharge in the first 24 hours for both the hip and the knee. However, with total knee replacement there was a trend for a more prolonged wound discharge with OCA. With total hip replacement there was no significant difference between the groups for either early or late complications. Closure of the wound with skin staples was significantly faster than with OCA or suture. There was no significant difference in the length of stay in hospital, Hollander wound evaluation score (cosmesis) or patient satisfaction between the groups at six weeks for either hips or knees.

We consider that skin staples are the skin closure of choice for both hip and knee replacements.

Allograft bone is widely used in orthopaedic surgery, but peri-operative infection of the graft remains a common and disastrous complication. The efficacy of systemic prophylactic antibiotics is unproven, and since the graft is avascular it is likely that levels of antibiotic in the graft are low.

Using an electrical potential to accelerate diffusion of antibiotics into allograft bone, high levels were achieved in specimens of both sheep and human allograft. In human bone these ranged from 187.1 mg/kg in endosteal (sd 15.7) to 124.6 (sd 46.2) in periosteal bone for gentamicin and 31.9 (sd 8.9) in endosteal and 2.9 (sd 1.1) in periosteal bone for flucloxacillin. The antibiotics remained active against bacteria in vitro after iontophoresis and continued to elute from the allograft for up to two weeks.

Structural allograft can be supplemented directly with antibiotics using iontophoresis. The technique is simple and inexpensive and offers a potential means of reducing the rate of peri-operative infection in allograft surgery. Iontophoresis into allograft bone may also be applicable to other therapeutic compounds.

Introduction and Aims: Fibrin-sealant has been recommended as a tissue glue for autologous chondrocyte implantation. It is known that the active compound of fibrin-sealant is thrombin, but its effect on chondrocytes is still unclear. The aims of this study are to examine if fibrin-sealant stimulates proliferation and survival of human chondrocytes.

Method: To determine if human chondrocytes express thrombin receptors, we have conducted immunoconfocal analyses and RT-PCR for the detection of PAR type I, II, III and IV. To examine if thrombin activates intracellular signalling of chondrocytes, we have examined the intracellular calcium signalling by thrombin. Proliferation of chondrocytes was also tested with various concentrations of thrombin. The migration of chondrocytes was monitored by co-culturing of the cells with fibrin-sealant for up to 15 days.

Results: Primary human chondrocytes express thrombin receptor PAR types I, II, II and IV as evidenced by immunohistochemistry and RT-PCR. Induction of intracellular calcium signals was evidenced in majority of chondrocytes at 100 seconds after addition of thrombin. To confirm if evaluation of calcium signal activation is by a specific PAR receptor, we have examined the effect of specific peptides, which mimic the receptor activation on calcium signalling. The result showed that expression of PAR I and II receptor in chondrocytes is responsible for the activation of intracellular calcium. When human chondrocytes were co-cultured with thrombin at a dose between 1u/mL to 10u/mL, there was no effect on cellular proliferation at 24 hours. However at 48 hours, thrombin stimulated proliferation and survival of chondrocytes in a dose-dependent manner. A maximum of threefolds induction was evidenced at a dose of 10u/mL (p< 0001). Co-culture of chondrocytes with fibrin-sealant showed that after 12 hours only a few cells had migrated from the membrane to the fibrin-sealant, but after 36 hours many cells had formed a layer on the surface of the fibrin-sealant. By 15 days of co-culture, it was evidenced that the majority of chondrocytes were migrating into the fibrin-sealant.

Conclusion: The results of this study show that human chondrocytes express thrombin receptor and fibrin-sealant is capable of inducing chondrocyte proliferation and migration.

Introduction and Aims: The aim of this study was to use biological, functional and radiographic evaluation to demonstrate that cultured autologous chondrocytes implanted using a type I/III collagen membrane leads to regeneration of hyaline-like articular cartilage in the knee.

Method: Approximately 70,000 knee arthroscopies are performed every year in Australia; 60% involve chondral surface defects. Three regenerative autologous cell therapy techniques have been used in Australia to treat full thickness chondral lesions:

periostial-covered autologous chondrocyte implantation (PACI);

The team at the University of Western Australia has concentrated on CACI and MACI techniques because of concerns over fibroblast formation and hypertrophy with PACI. Definitive evidence regarding the role of the membrane in enhancing chondrocyte-mediated cartilage regeneration is lacking.

Results: The series consists of a total of 71 patients who had failed previous surgical treatment prior to definitive collagen-covered ACI (32 implantations in 31 patients) or MACI (43 implantations in 40 patients). Biological, functional and radiographic evaluations were conducted pre-operatively, and post-operatively in order to determine the success of integration of implanted chondrocytes and categorise the level of restoration in knee joint function. Post-operative MRI scans at three months show oedematous tissue at the defect sites, contrasting with the fluid-filled defects seen pre-operatively. MRI scans at one, two and three years (collagen-covered) and one year (MACI) show normal cartilage signal. Apopototic test of chondrocytes before implantation showed that viability of chondrocytes was over 85% where apopototic rate of chondrocytes was less than 2%. Six-minute walk test and KOOS results indicate improved functional capacity following collagen covered and MACI.

Conclusion: Results from this clinical study indicate that the use of a type I/III collagen membrane in conjunction with ACI is a valid new approach for the treatment of chondral defects. Results from radiographic, functional and biological evaluations are encouraging. Ongoing follow-up will reveal the durability of reconstructions with CACI and MACI.

Introduction and Aims: The clinical studies of knee disorders utilise patients’ activity levels to measure issues that are really important to the patients. Knowing the large variations among patients in terms of the frequency and intensity of sports participation and frustrated by the lack of relevance and specificity of current questionnaires to the Australian public, the authors have devised their own.

Method: The new questionnaire was sent to all members of the Australian Knee Society in an attempt to formulate a consensus view that could then be sent for reliablility and validity testing. The score is represented by two numbers. The first one represents the activity performed and the second, the level at which it was played. These scores are multiplied to give a variable score ranging from one to 20.

Results: An 80% response rate was achieved. Of those that responded, 30.5% agreed completely with the questionnaire as it stood, 69.5% agreed with few modifications, and none disagreed.

Conclusion: A rating of activity level is critical for studies comparing two treatments to ensure that the patient groups are equivalent. We believe that the new Wood-ford activity level scale is fast, easy to use and will facilitate a more accurate comparision among patients with knee injuries in sports medicine. It is easily transferred between different countries and their common sports.

Introduction and Aims: A number of ‘minimally invasive’ approaches have been described which are essentially a standard approach through a smaller incision: the term ‘mini-incision’ is more appropriate. We describe a new technique that is truly soft-tissue sparing and report our early results.

Method: Following Malchau’s principles we performed cadaver studies to familiarise ourselves with the approach before conducting a pilot study. The approach involves a 6–8cm oblique incision over the posterior aspect of the greater trochanter. Care is taken to preserve piriformis and gluteus maximus. Meticulous capsular repair is performed through drill holes into bone at the end of the procedure to reconstruct the posterior envelope. There are no restrictions to mobility post-op.

Patients were scored pre-operatively and followed up prospectively. The only special instruments required are two large curved Hohmann retractors and an angled cup introducer.

Results: One hundred and one consecutive routine primary total hip replacements were performed via the ‘piriformis-sparing minimally invasive approach’ by a single surgeon. Marked on-table stability was noted in all hips prior to capsular repair.

Forty-two percent of patients were male. Mean age was 68.9 years (42–90) and BMI 26 (14–39). Average operation time was 64.1 minutes and anaesthetic time 92.5 minutes. Mean fall in haemoglobin in the first 24 hours was 2.3g/dl. Mean incision length was 7.4cm.

Follow-up was a minimum of one year (range 12–29 months). There was a highly statistically significant improvement in WOMAC and SF-36 scores at three and 12 months post-operatively (p< 0.0001). Early medical complications occurred in 12 patients, including two superficial infections, all of which resolved. There were no peri-prosthetic fractures and importantly, no dislocations. There were two re-operations: one revision for cup displacement and one washout for deep infection.

Conclusion: We believe that the marked stability that we achieve on-table is only possible by sparing piriformis and careful capsular repair. As with all new procedures however, there is a learning curve for both surgeon and assistant. Preliminary results from our pilot study may be interpreted with guarded optimism.

Introduction and Aims: Treatment of rotator cuff tendon tear presents a significant therapeutic challenge to surgeons. Porcine small intestinal submucosa (SIS) is a biomaterial approved by TGA and FDA for the repair of rotator cuff tendon tear. The aims of this study are to evaluate the safety and efficacy of SIS.

Method: SIS purchased from DePuy Johnson & Johnson was examined by histology and PCR technique. The material was also implanted into mice and rabbits for the evaluation of biological reaction and inflammatory response. Porcine immunoreceptor DAP12 gene was used to examine if the material contained porcine DNA.

Results: Fresh SIS membrane before implantation contains multiple layers of spindle-shaped cells mixed with a small population of round-shaped cells. Chloro-acetate esterase staining showed that the round-shaped cells are positive, indicating that they are mast cells. The tissue architecture of SIS mimics to tendon structure as evidenced by H& E staining. To further confirm if cells present in SIS material were porcine origin, nested PCR for the amplification of DAP12 gene was used. The result demonstrated that SIS membrane contain porcine DNA materials.

Conclusion: SIS contains porcine cells and nuclei acid, which contradicts with current views that SIS is a cell-free biomaterial. Although no foreign body reaction of SIS was observed, SIS implant may cause chronic inflammation. Further studies should be conducted to confirm the clinical efficacy of SIS implant.

Introduction and Aims: Iontophoresis is a method to introduce antibiotic molecules into allograft bone using an electrical potential. In-vitro testing has shown that these antibiotics should be released in their bioactive form at therapeutic levels for extended periods of time. This is the first report of iontophoresed allograft implantation into patients.

Method: A method of loading tubular sections of cortical bone was used in theatre prior to implantation. The bone was held vertically in an antibiotic bath with a cylindrical outer electrode and a wire electrode down the centre of the bone. An electrical potential of approximately 90V was applied to drive the antibiotics into the bone. Post-operative serum, drain and allograft antibiotic assays were performed. All patients were followed-up clinically and radiologically. Patients who required a bulk segmental allograft from June 1997 to present were entered into the trial and received iontophoresed bone.

Results: Since June 1997, 35 patients have received 37 iontophoresed allografts. Indications for allograft insertion were limb salvage for tumor (16), poor bone stock associated with infection (12), periprosthetic fracture (seven), aseptic loosening (one) and recurrent dislocation of total hip replacement (one). One patient had acute complications requiring amputation. No patients were lost to follow-up with a mean follow-up of 3.3 years. Two patients required an allograft exchange for fracture and infection. There were two late allograft infections at 10 and 18 months. One patient was revised to another iontophoresed allograft and has had no recurrence at two years. The other infection required above knee amputation. One allograft was revised with allograft exchange and vascularised fibular graft following fracture of metal fixation. There was one case of persistent non-union in a knee fusion, which was treated after 21 months by removal of the intermedullary fixation and allograft and use of an Ilizarov frame. All other allografts are in-situ with no complications related to the allograft. Twelve patients had pre-existing proven infections. None of these patients have been re-infected to date. Therapeutic gentamicin and flucloxacillin levels were detected in drain fluid samples post-operatively, averaging from 39.9 mg/L at two hours to 5.97mg/L at 48 hours for gentamicin and 16.83mg/L at two hours and 2.23 mg/L at 48 hours for flucloxacillin. This was significantly greater than the minimum inhibitory concentration (MIC) against Staphylococcus aureus for gentamicin (0.25mg/L) and flucloxacillin (0.30mg/L). At the same time, blood levels remained in a safe range.

Conclusion: Iontophoresis is a safe and inexpensive method that can be executed in the operating theatre. Iontophoresed bone delivers a high local dose of antibiotic, which may prevent early biofilm formation initiated during allograft handling and exposure to theatre air. With no early infections and no re-infections, further assessment of this technique continues with guarded optimism.

Introduction and Aims: Autologous chondrocyte implantation (ACI) is emerging as a leading technique for the treatment of articular cartilage defects. However, there exists some debate regarding which ACI technique is best able to regenerate hyaline cartilage. To this end, the development of a non-invasive technique enabling the examination of microstructure after ACI is essential.

Method: In this study, we have developed a novel 2D Laser Scanning Confocal Arthroscope (LSCA) in the assessment of articular cartilage and examined the microstructure of knee articular cartilage from rabbits and patients with total knee arthroplasty. The LSCA system consists of the LSA handheld probe, a Launch and Detection Unit (LDU) with a built in 488nm–514nm Krypton Argon Laser and Master Control unit (MCU). Human and rabbit knee articular cartilage stained with Fluoroscein (5g/L) and Acriflavine (0.5g/L) were used to examine the microstructure of cartilage by LSCA.

Results: By LSCA we have generated optical histology images of normal human and rabbit articular cartilage from the femoral condyle. Optical histology of normal articular cartilage tissue reveals typically smooth surface texture with relatively homogenous sub-surface distribution of viable chondrocyte cells. The general orientation of collagen fibres is occasionally visible in surface images. Optical histology of arthritic cartilage of humans showed clusters of round-shaped chondrocytes mixed with spindle-shaped cells. Surface cracking typically indicative of tissue damage is also evident by LSCA observation. Examination of rabbit knee six weeks after ACI showed high density of chondrocytes and homogeneous matrix on the site of the defect.

Conclusion: In short, we have shown the efficacy of LSCA in the non-destructive assessment of articular cartilage in vivo. Further study is required to evaluate the clinical significance of optical histology of LSCA.

Introduction and Aims: The Lateral Femoral Cutaneous Nerve is placed at risk of iatrogenic injury in the dual incision minimally invasive approach THA. A number of trials have indicated rates of injury up to 30%. This clinical and cadaver study examined the morphology of the nerve in 101 cadaver specimens and in 78 dual incision THA patients.

Method: One hundred and one lateral femoral cutaneous nerves of the thigh were dissected in fresh and formalin embalmed specimens. Dissection was limited to the anterior thigh and the branch pattern of the LFCN recorded. Dual incision patients were followed prospectively and examined with regard to LFCN paraesthesia.

Results: Despite the variability of the nerve, three basic morphologic patterns emerged. Approximately 55% had a major medial trunk and smaller lateral branch, 30% involved two distinct large branches and 15% had a trifurcation or other pattern.

In our clinical series, over 30% of patients experienced paraesthesia and some experienced a burning dysaesthesia in the distribution of the LFCN.

Conclusion: Iatrogenic injury to the LFCN is relatively common in the dual incision minimally invasive THA and patients must be informed of such a risk. Based on this study we have slightly modified our incision and approach.

Introduction and Aims: The use of ‘superglue’ (2-Octylcyanoacrylate) in wound closure is well established in other surgical specialties, but not described in orthopaedics. The aim was to compare superglue with staples and subcuticular suture in a prospective randomised trial.

Method: One hundred and fifty patients admitted for a primary total knee or hip replacement were randomised to receive either clips, continuous subcuticular suture (3.0 Monocryl) or ‘superglue’ for wound closure. All knee replacements were mobilised on the day of surgery with CPM and hip replacements on the first post-operative day. Patients’ wounds were assessed on day one and at six weeks by a blinded observer.

Results: There were 80 hips and 70 total knee replacements performed; 51 wounds were closed with clips, 50 with suture and 49 with superglue. Mean duration of skin closure was significantly shorter with staples, and superglue was significantly faster than suture. There was no significant difference in the complication rates between the groups, including infection, dehiscence or allergic reaction. There was significantly more ooze by day one from the wounds closed with clips than the other two groups. Significantly more of the wounds closed with glue had no strike-through on to the dressing, and were therefore deemed to be ‘sealed’. Patient satisfaction at six weeks was significantly higher with superglue and suture than staples. The suture and super-glue groups had higher median scores on the Hollander wound evaluation scale than staples, however the difference was not statistically significant. Surgeon satisfaction with technique was highest with superglue and staples (no significant difference between the groups), and significantly higher than with subcuticular suture.

Conclusion: Superglue is safe to use for skin closure in primary knee and hip arthroplasty. Although closure with staples is faster, superglue is associated with less wound ooze and better patient satisfaction. The cosmetic result with superglue is comparable to that of subcuticular sutures but has a better surgeon satisfaction score.

Introduction and Aims: It is probable that the success of total knee arthroplasty without patellar resurfacing is influenced by the design of the femoral trochlea. The aim of this study was to compare measures of clinical outcome including gait analysis between total knee arthroplasty with and without patellar resurfacing using a prosthesis compatible with the native patella.

Method: A prospective trial of 78 patients was performed, with 43 total knee arthroplasty randomised to receive patellar resurfacing and 48 to receive patellar retention. The mean duration of follow-up was 3.2 years (range 2.0–4.7 years). Patients were assessed pre- and post-surgery using the Knee Society Clinical Rating System, the Knee Pain Scale, and a Patellar Function Score. A subset of 34 patients also underwent pre- and post-surgery analysis of knee kinematics and kinetics during walking.

Results: At a minimum two-year follow-up, total knee arthroplasty with patellar resurfacing had significantly lower Knee Society knee scores (Mann Whitney U test; p = 0.036). Total knee arthroplasty with patellar resurfacing exhibited a greater degree of knee flexion contracture (Mann-Whitney U test; p = 0.020) and significantly less knee extension at heelstrike during walking in those subjects undergoing gait analysis (Independent t-test; p = 0.013). The presence of a knee flexion contracture was a significant predictor of post-surgery anterior knee pain (Exp β = 4.1, CI: 1.1 to 14.9, p = 0.033). Post-surgery Knee Society function scores and Patellar Function Scores were significantly better in those patients with total knee arthroplasty without patellar resurfacing (Mann-Whitney test; p = 0.031 and 0.017 respectively).

Conclusion: In this study using an anatomically designed femoral component with a domed patellar prosthesis, total knee arthroplasty with patellar resurfacing exhibited inferior clinical results as compared to total knee arthroplasty with patellar retention. Total knee arthroplasty with patellar resurfacing exhibited significant limitation of knee extension, which was significantly associated with the presence of post-surgery anterior knee pain (p = 0.033).

Introduction Rotator cuff degeneration is considered to be a major factor in the pathogenesis of rotator cuff tendon tear. Degenerative weakening of the rotator cuff can result in irreversible complete cuff-tear arthropathy syndrome. Recently a porcine small intestinal submucosa (SIS) has been approved by TGA as biological implant for the repair of rotator cuff tendon tear. The aims of this study are to evaluate the safety and efficacy of SIS.

Methods A commercial brand of SIS was examined by histology and PCR technique. The material was implanted into mice and rabbits for the evaluation of biological reaction and inflammatory response. Next, we have used SIS to replace the rotator cuff tendon in rabbit (N=10) and compared to control (N=10). Histological examination was conducted at four and eight weeks after implantation. To further confirm if cells present in SIS material were of porcine origin, nested PCR for the amplification of DAP12 gene was used.

Results Fresh SIS membrane before implantation contain multiple layers of spindle-shaped cells mixed with a small population of round-shaped cells. Chloroacetate esterase staining showed that the round-shaped cells are positive, indicating that they are mast cells. The tissue architecture of SIS mimics tendon structure as evidenced by H & E staining. The SIS membrane contained porcine DNA materials. Subcutaneous implant of SIS in mice (by six) for up to seven days showed no obvious inflammatory response or foreign body reaction. The result demonstrated that SIS has remained in the region and mixed with regenerative fibrous tissue after eight weeks. In some cases there was a massive recruitment of lymphocytes along the surface of membrane. However, no foreign body reactive giant cells were observed.

Conclusions The result of this study indicated that SIS contains porcine cells and nucleic acid, which contradicts current views that SIS is a cell free biomaterial. Although no foreign body reaction of SIS was observed, SIS implant may cause chronic inflammation. Further studies should be conducted to confirm the clinical efficacy of SIS implant for rotator cuff tendon tear.

Introduction An approximation of normal knee kinematics after knee replacement may improve knee function and implant fixation and reduce wear of the prosthesis. This study describes the knee joint kinematics after unicondylar knee arthroplasty (UKA) in general, and compares the Miller-Glante (MG, fixed bearing) and Oxford (mobile bearing) implants in particular.

Methods Twenty-two knees in 17 patients (11 males, six females, mean age of 69.7 yrars) were randomized into MG (11 knees) or Oxford (11 knees). No clinical complications or signs of loosening were observed. At the one year follow-up, RSA (Radiosterometry) x-rays were taken by using two x-ray tubes positioned at knee level and exposing the knee simultaneously from the side. Four pairs of weight bearing x-ray were obtained at zero degrees, 30°, 60°, 90° of knee flexion, with zero as reference position. Tibial rotation, rollback, translation of tibia-femur contact point, and the bearing movement were analyzed using UmRSA software.

Results With the MG implant, the tibia internally rotated 3.0°, 3.0°, and 4.2° respectively at 30°, 60°, and 90° of flexion, while with the Oxford implant, the tibia internally rotated 4.3°, 7.6°, and 9.5° respectively at 30°, 60°, and 90°. No significant difference was found between the two groups (P> 0.05, Repeated-measures ANOVA). The medial femoral condyle moved backward (1.8 and 1.5 mm respectively in MG and Oxford) from zero degrees to 30° of flexion. At 60°, it moved anteriorly in both knees, in MG to 0.9 mm anteriorly and in Oxford to 0.6 mm posteriorly to the reference position. At 90° the condyle moved 4.2 mm (MG) and 0.7 mm (Oxford) anteriorly to the reference position. No significant difference between the groups (P> 0.05). The femur-tibia contact point in MG moved anteriorly 2.8, 5.1, and 3.9 mm, respectively at 30°, 60°, and 90° of flexion, whereas the contact point in Oxford moved posteriorly 2.6, 1.8, 2.4 mm respectively at 30°, 60°, and 90°. A significant difference was found between the groups (P=0.003). The bearing in the Oxford implant moved backward of 2.2, 2.0, and 0.9 mm respectively at 30°, 60°, and 90° of knee flexion.

Conclusions The in-vivo weight bearing 3D knee kinematics after UKA with fixed or mobile bearing was described. In MG the medial femoral condyle moved forward with knee flexion, whereas in Oxford it moved backward together with the bearing, which is closer to normal knee kinematics.

Introduction Fibrin-sealant has been widely used clinically for the protection of haemorrhage, wounds and tissue fluid leakage. Recently fibrin-sealant has been recommended as a tissue glue for autologous chondrocyte implantation. It is known that the active compound of fibrin-sealant is thrombin but its effect on chondro-cyte is still unclear. The aims of this study are to examine if fibrin-sealant stimulates proliferation and survival of human chondrocytes.

Methods Primary human chondrocytes derived from articular cartilage were used for the detection of thrombin receptors RAR type I, II, III and IV by immunohistochemistry and RT-PCR. To examine the effect of thrombin on chondrocytes, the changes in free intra-cellular calcium were monitored after the addition of thrombin. Proliferation of chondrocytes were also tested with various concentrations of thrombin. The survival of chondrocytes was monitored by co-culturing of the cells with fibrin-sealant for up to 15 days. Primary human chondrocytes express thrombin receptor RAR types I, II, III and IV as evidenced by immunohistochemistry and RT-PCR. However, the level of expression appears to be varied between cells. This has been reflected by the measurement of intracellular calcium signal in chondrocytes.

Results Induction of intracellular calcium signals was evidenced in the majority of chondrocytes at 100 seconds after addition of thrombin. When human chondrocytes were co-cultured with thrombin at a dose between 1u/ml to 10u/ml, there was no effect on cellular proliferation at 24 hours. However, at 48 hours thrombin stimulated proliferation and survival of chondrocytes in a dose dependent manner. A maximum of three folds induction was evidenced at a dose of 10u/ml (p< 0001). Co-culture of chondrocytes with fibrin-sealant showed that after 12 hours only a few cells had migrated from the membrane to the fibrin-sealant, but after 36 hours many cells had formed a layer on the surface of fibrin-sealant. By 15 days of co-culture, it was evidenced that majority of chondrocytes were migrating into the fibrin-sealant. Immunohistology study showed that these cells express type II collagen, suggesting that they maintain the phenotype of chondrocytes.

Conclusions The results of this study show that human chondrocytes express thrombin receptor and fibrin-sealant is capable of inducing chondrocyte proliferation and maintain the survival of chondrocytes.

In relation to the conduct of this study, one or more of the authors is in receipt of a research grant from a non-commercial source.

Introduction Wear particle induced osteolysis is regarded as the main reason for aseptic loosening of hip replacements. Crosslinked polyethylene show extremely low wear in lab studies and is routinely used today, though with very little clinical testing. We report wear, migration and function for uncemented cups with a crosslinked poly.

Methods Twelve hips in 12 patients with mean age of 70 years were operated with uncemented cups (Reflection), cemented stems and metal heads. Five Mrad cross linked liners annealed below melt temperature were used in all hips (XLPE, Smith & Nephew). Tantalum markers were inserted in liners and acetabular bone for RSA measurements and migration and wear measured over two years. The result was compared to matched controls from a study of 80 cups with the same implant and non cross linked poly, operated by the same surgeon. X-rays, WOMAC and Sf-36 were performed pre-operatively and at two years.

Results The mean proximal head penetration at two months was 0.09 mm. This was thought to be mainly due to the creep of the polyethylene and was equal to “normal” poly. At the one year follow-up the mean proximal wear had increased with 0.02 mm and at two years 0.03 mm. This compares with the 0.33 mm recorded for the old poly (p=0.001, Mann Whitney U test.). The cups migrated 0.2 mm proximally and showed a normal migration profile, comparable to the cups with non cross-linked poly. The accuracy of measuring proximal wear, in this study, was found to be 0.07 mm (95% CI). No differences in radiolucent lines or clinical scores were found.

Conclusions The first two years proximal wear was 0.03 mm compared to the 0.33 mm found for non crosslinked poly. This is a reduction with 90% which certainly looks promising.

Introduction There are clear theoretical advantages to support the use of bioabsorbable interference screws in the reconstruction of the anterior cruciate ligament. The purpose of this study is to determine how long it takes for an ACL screw marketed as bioabsorbable to be absorbed in the tibia.

Methods Eight patients that underwent an ACL reconstruction utilising a femoral endobutton and tibial bio-absorbable screw (Arthrex Bio-interference) made of Poly-L-Lactide (PLA) were followed up radiographically with sequential MRI scans at one, two and four years post-operatively. The scans, (Axial T1 and T2 with minimal interslice gap) were assessed by two independent consultant radiologists.

Results There was no evidence radiologically of progression to absorption of the tibial screw on any scan. The MRI appearance remained unchanged from one to four years with the exception of the presence of a small cyst in the tunnel of one of the patients.

Conclusions Despite claims by manufacturers of rapid rates of bio-absorption of their products, this study questions the accuracy of such statements not tested in-vivo. Our study clearly shows the continued presence of such a bioabsorbable screw at four years post-operatively.

Successful reconstructive surgery with allografts is severely limited by a failure rate of 30 – 40%. Allograft failure is due to nonunion of the graft-host junction. The molecular mechanism by which this occurs is not yet fully elucidated. Using a sheep femoral allograft model, we have investigated the cellular and molecular mechanisms associated with nonunion of bone allografts. Five, from a total of twelve operations, resulted in the development of graft-host nonunion, reflecting a failure rate of 42%. Histological assessment revealed that allograft failure was due to the excessive accumulation of and resorption by, osteoclasts (Ocs) on the surface of the bone allograft. Three distinct layers, lying adjacent to the allograft bone surface, in the nonunion groups, were identified. The outer fibroblastic layer contained abundant fibroblasts and connective tissue. Underlying this layer were synovial-like cells and some multinuclear giant cells. The third layer, opposing the bone surface, consisted of Ocs and round mononuclear cells. Histomorphometric analysis showed that allograft unions, featured a large amount of newly formed bone on the surface, (OS/BS = 47.81%) with a small proportion of eroded surface (ES/BS = 20.59%). The number of osteoclasts associated with the allograft bone surface were few (Oc/B.Pm = 1.7190/mm) and activity (ES/BS = 46.68%) of Ocs with a reduced amount of new bone formation (OS = 6.35%). Both calcitonin receptor and H+ATPase mRNA, characteristically expressed by Ocs, were localised to the multinuclear giant cells, indicating that they were Ocs. Synovial-like cells in the histological layer above the Ocs, expressed gene transcript for the Osteoprotegrin Ligand (OPGL), a membrane bound factor that is critical for the induction of Oc activity and osteoclastogenesis. In conclusion, these findings suggest that failure of bone allografts is partially due to excessive resorption by host Ocs, accompanied by reduced bone formation. The production of OPGL by synovial-like cells, may be responsible for the recruitment and generation of Ocs.

Introduction: Transmission of infection is always a concern in allograft bone banking and the surgical applications of such bone.

Aim: To review the microbiological results of the femoral head donor program at Perth Bone and Tissue Bank from March 1992 until April 2001.

Methods: There were 4515 femoral head donations. All were cultured by means of a swab and bone chip at time of retrieval, prior to storage at −75 degrees C. Once six month repeat serological testing of donors had been obtained, the heads were processed under sterile conditions. All soft tissues were removed, the bone was milled and washed with 1.5 litres warm saline as pulsed lavage. A microbiological swab was taken prior to packaging the graft ready for irradiation and freezer storage until use.

Results: Five hundred and seventy-nine femoral heads had a positive swab or chip at retrieval, with 31 cases having the same organism on both tests. In 516 cases only one of these tests was positive, with skin organisms being the dominant finding. In 10 cases the swab at the end of processing was positive on culture. Eight of these cases were negative on retrieval testing, and in only one case was the same organism, a coagulase negative staphylococcus, present on the processing swab and retrieval testing.

Conclusions: This work suggested that microbiological culture of femoral head swabs and bone chips at time of retrieval has little effect on the culture at the end of processing. After storage at −75 degrees C, mechanical cleaning and washing, less than 1% of femoral heads were positive prior to irradiation.

A paper was presented two years ago reviewing evidence of absorption of the Bio Interference screw and tunnel widening at three, six and 12 months following anterior cruciate ligament reconstruction using double-stranded hamstrings. The femoral fixation was with an Endobutton with a double loop of Mercylene tape with a Bio Interference screw and an extra small staple for the distal fixation. This paper presents further magnet resonance imaging (MRI) studies at least two years after surgery on 10 of those patients to assess if there was any MRI evidence of absorption of the Bio Interference screw or tunnel widening (in particular ganglion formation) in the femoral or tibial tunnels.

The results showed that at least two years after surgery there was little evidence of Bio Interference screw absorption. There was no evidence of tunnel widening.

Articular cartilage defects of the knee occur commonly in sports injuries and trauma. Increasing evidence suggests that the only technique that enables the regeneration of articular hyaline cartilage in chondral defects is autologous chondrocyte implantation (ACI). Here we have reported our clinical experience of autologous chondrocyte implantation using biodegradable type I/III collagen membrane (CACI). A total of 26 patients (age range from 19 to 60 years, average 37 years) was conducted with CACI. Pre-operative magnetic resonance imaging (MRI) scans were performed on all patients. Post-operative MRI scans were planned for approximately three and 12 months after the surgery to determine the success of integration of implanted chondrocytes.

The results demonstrated that the initial post-operative MRI scans at three months showed the presence of oedematous tissue at the defect sites in 23 patients, contrasting with the fluid filled defects seen preoperatively and with and MRI signal differing from that of the surrounding normal hyaline articular cartilage. MRI scans in nine patients at 12 months after their operations showed maturation of cartilage graft in all patients. Apopototic testing of the chondrocytes using Annexin IV before implantation showed that the viability of the chondrocytes was over 85% where the apopototic rate of chondrocytes was less than 2%. One patient with an apopototic rate of over 10% has a delayed repair in cartilage defects as shown by MRI.

In conclusion, early phase clinical studies showed that autologous chondrocyte implantation remains promising for the treatment of chondral defects with restoration of hyaline cartilage. Longer clinical follow-up of the patients and better assessment of cellular phenotype of chondrocytes before implantation are required.

We report a prospective study of the influence of various factors on the six-month mortality of 531 patients with subcapital hip fractures. We performed univariate and multivariate analyses on the 403 patients treated surgically. The most significant predictors of the six-month mortality were dementia, postoperative chest infection, malignant neoplasia, old age and deep-wound infection, in that order. A simple test of mental ability was the most significant prognostic indicator and this test should be included in future studies of the management of hip fractures in the elderly.

The early results of revision osteoarticular allografts in weight-bearing joints are reported. Sixteen consecutive patients underwent surgery over a six-year period between 1982 and 1988. At the time of review eight patients (50%) had surviving second allografts with an average follow-up time of 48 months (range 12 to 87). Five patients were graded excellent according to the Mankin scale, one good and two fair. Eight patients (50%) required further surgery, but only two patients came to amputation.