Aims

To establish the survivorship, function, and metal ion levels in an unselected series of metal-on-metal hip resurfacing arthroplasties (HRAs) performed by a non-designer surgeon.

Objectives

The medially spherical GMK Sphere (Medacta International AG, Castel San Pietro, Switzerland) total knee arthroplasty (TKA) was previously shown to accommodate lateral rollback while pivoting around a stable medial compartment, aiming to replicate native knee kinematics in which some coronal laxity, especially laterally, is also present. We assess coronal plane kinematics of the GMK Sphere and explore the occurrence and pattern of articular separation during static and dynamic activities.

Aims

Short-stemmed femoral implants have been used for total hip arthroplasty (THA) in young and active patients to conserve bone, provide physiological loading, and reduce the incidence of thigh pain. Only short- to mid-term results have been presented and there have been concerns regarding component malalignment, incorrect sizing, and subsidence. This systematic review reports clinical and radiological outcomes, complications, revision rates, and implant survival in THA using short-stemmed femoral components.

Background

In the late 1980's Michael Freeman conceived the idea that knee replacement would most closely replicate the natural knee joint, if the medial Tibio-Femoral articulation was configured as a “ball-in-socket”. Over the last three decades, medial rotation and medial pivot designs have proved successful in clinical use. Freeman's final iteration of the medial ball-in-socket concept was the Medial Sphere knee. We report the three-year survivorship, clinical outcomes, patient reported outcome measures (PROMs) and radiographic analysis of this implant in a multi-centre, multi-surgeon, prospective observational study.

Objectives

Throughout the 20th Century, it has been postulated that the knee moves on the basis of a four-bar link mechanism composed of the cruciate ligaments, the femur and the tibia. As a consequence, the femur has been thought to roll back with flexion, and total knee arthroplasty (TKA) prostheses have been designed on this basis. Recent work, however, has proposed that at a position of between 0° and 120° the medial femoral condyle does not move anteroposteriorly whereas the lateral femoral condyle tends, but is not obliged, to roll back – a combination of movements which equates to tibial internal/ femoral external rotation with flexion. The aim of this paper was to assess if the articular geometry of the GMK Sphere TKA could recreate the natural knee movements in situ/in vivo.

Peri-prosthetic infection is amongst the most common causes of failure following total knee replacement (TKR). In the presence of established infection, thorough joint debridement and removal of all components is necessary following which new components may be implanted. This can be performed in one or two stages; two-stage revision with placement of an interim antibiotic-loaded spacer is regarded by many to be the standard procedure for eradication of peri-prosthetic joint infection.

We present our experience of a consecutive series of 50 single-stage revision TKRs for established deep infection performed between 1979 and 2010. There were 33 women and 17 men with a mean age at revision of 66.8 years (42 to 84) and a mean follow-up of 10.5 years (2 to 24). The mean time between the primary TKR and the revision procedure was 2.05 years (1 to 8).

Only one patient required a further revision for recurrent infection, representing a success rate of 98%. Nine patients required further revision for aseptic loosening, according to microbiological testing of biopsies taken at the subsequent surgery. Three other patients developed a further septic episode but none required another revision.

These results suggest that a single-stage revision can produce comparable results to a two-stage revision. Single-stage revision offers a reduction in costs as well as less morbidity and inconvenience for patients.

Cite this article: Bone Joint J 2014;96-B:759–64.

Introduction

There are conflicting reports in the literature regarding the migration of femoral stems in revision hip arthroplasty following the use of impaction allografting with or without cement. In some cemented series distal migration of the prosthesis within the cement mantle has been recorded, as well as migration of the whole cement/prosthesis construct into the graft.

An attempt to analyse whether impaction allografting without cement is more or less satisfactory than the technique with the addition of cement is compromised by conflicting reports of where the migration actually occurs. In some cemented series distal migration of the prosthesis within the cement mantle has been recorded as well as migration of the whole cement/prosthesis construct into the graft.

Two prospective consecutive series of revision hip arthroplasties by a single surgeon:- Group 1; Uncemented impaction grafting revision hip replacement in a series of 30 patients (33 hips). Group 2; Cemented impaction grafting revision hip replacement in a series of 30 patients (31 hips). Group demographics were similar. Each case used the same design of hip implant with the only difference in design being a proximal hydroxyapatite coating used on the uncemented implants.

Follow-up ranged from 2 to 17 years for the uncemented group and from 1 to 11 years for the cemented group. A validated hip scoring system was employed at regular follow up incorporating pain and functional assessment.

Migration rates for the uncemented group were 0 to 15 mm for 30 hips; however 3 hips were revised early due to excessive migration. 3 hips sustained early complications (1 fracture, 1 dislocation, 1 varus malposition of stem). Migration rates for the cemented group were 0 to 9 mm for 29 hips, however the remaining 3 hips were revised due to excessive migration (up to 33mm). Although similar results were obtained in terms of success and also pain and function scores, marginal improvement in results did occur with the cemented series overall. Statistical significance was not reached however. More sinkage occurred in the uncemented group overall, the majority occurring in the first 6 post-operative months. Part of the improvement with the cemented series results may be explained by the improved techniques achieved whilst performing the uncemented series.

These results from a single surgeon demonstrate that the method is highly technique dependent and relies on adequate graft impaction. With sufficient graft and an appropriate prosthetic design, cement is not essential to the early success of this method. However, the extent of the initial migration did not accurately predict a successful outcome for the procedure. The absence of cement removes any confusion as to the location of any migration.

We report the long-term results of revision total hip replacement using femoral impaction allografting with both uncemented and cemented Freeman femoral components. A standard design of component was used in both groups, with additional proximal hydroxyapatite coating in the uncemented group. A total of 33 hips in 30 patients received an uncemented component and 31 hips in 30 patients a cemented component. The mean follow-up was 9.8 years (2 to 17) in the uncemented group and 6.2 years (1 to 11) in the cemented group. Revision procedures (for all causes) were required in four patients (four hips) in the uncemented group and in five patients (five hips) in the cemented group. Harris hip scores improved significantly in both groups and were maintained independently of the extent of any migration of the femoral component within the graft or graft–cement mantle.

The proximally hydroxyapatite coated neck retaining Freeman hip stem (Finsbury Orthopaedics, Leather-head, United Kingdom.) was first implanted in 1989. The outcome of the first 100 stems, in 52 men (6 bilateral) and 40 women (2 bilateral) has been reported to ten years, we have extended the follow-up of this series to 17 years.

The mean age was 58.9 years (19 to 84). The diagnosis was osteoarthritis for 70 hips, rheumatoid arthritis for seven hips, post-traumatic arthritis for 14 hips and either avascular necrosis, septic arthritis or developmental hip disorder in nine hips.

The total hip replacements implanted during the period of study (January 1989 to March 1992) were all secured without cement for either component. The acetabular components comprised press-fitted screw-in Rotalok implants (Corin Medical, Cirencester, United Kingdom) or SLF components (Finsbury). All operations were performed using an anterolateral approach with retention of the femoral neck. Three patients have been lost to follow-up, but are included up to their last clinical follow-up.

There have been 40 re-operations for revision of the acetabular component due to aseptic loosening. However, in all but four of these cases the stem was not revised. In two of these the stem revisions were for damage to the trunion following fracture of the modular ceramic head producing fretting against the ceramic debris and acetabular component. In the other two, revision was due to surgeon preference and in both cases well fixed femoral components were extracted at the time of acetabular revision. Osteointegration of these two stems was evidenced by the adherent bone at the time of removal. There has been only one case of aseptic loosening occurring at 14 years. This was found to be rotationally loose at revision and in hindsight was undersized having migrated distally 7.6mm in the first year before stabilising. The survivorship for the stem at 17 years is 98.5% (95% CI; 94.6% to 100%) with 52 patients at risk, all of whom have satisfactory clinical and radiological outcomes. The Freeman uncemented neck retaining proximally hydroxyapatite coated stem has excellent survival results to 17 years.

The outcome at ten years of 100 Freeman hip stems (Finsbury Orthopaedics, Leatherhead, United Kingdom) retaining the neck with a proximal hydroxyapatite coating in a series of 52 men (six bilateral) and 40 women (two bilateral), has been described previously. None required revision for aseptic loosening. We have extended the follow-up to 20 years with a minimum of 17 years. The mean age of the patients at total hip replacement was 58.9 years (19 to 84).

Six patients were lost to follow-up, but were included up to their last clinical review. A total of 22 patients (22 hips) had died, all from causes unrelated to their surgery. There have been 43 re-operations for failure of the acetabular component. However, in 38 of these the stem was not revised since it remained stable and there was no associated osteolysis. Two of the revisions were for damage to the trunnion after fracture of a modular ceramic head, and in another two, removal of the femoral component was because of the preference of the surgeon. In all cases the femoral component was well fixed, but could be extracted at the time of acetabular revision. In one case both components were revised for deep infection. There has been one case of aseptic loosening of the stem which occurred at 14 years. This stem had migrated distally by 7.6 mm in ten years and 8.4 mm at the time of revision at which stage it was found to be rotationally loose. With hindsight this component had been undersized at implantation.

The survivorship for the stem at 17 years with aseptic loosening as the endpoint was 98.6% (95% confidence interval 95.9 to 100) when 62 hips were at risk. All remaining stems had a satisfactory clinical and radiological outcome. The Freeman proximally hydroxyapatite-coated femoral component is therefore a dependable implant and its continued use can be recommended.

We describe the survivorship of the Medial Rotation total knee replacement (TKR) at ten years in 228 cemented primary replacements implanted between October 1994 and October 2006, with their clinical and radiological outcome. This implant has a highly congruent medial compartment, with the femoral component represented by a portion of a sphere which articulates with a matched concave surface on the medial side of the tibial insert.

There were 78 men (17 bilateral TKRs) and 111 women (22 bilateral TKRs) with a mean age of 67.9 years (28 to 90). All the patients were assessed clinically and radiologically using the American Knee Society scoring systems. The mean follow-up was for six years (1 to 13) with only two patients lost to follow-up and 34 dying during the period of study, one of whom had required revision for infection.

There were 11 revisions performed in total, three for aseptic loosening, six for infection, one for a periprosthetic fracture and one for a painful but well-fixed replacement performed at another centre.

With revision for any cause as the endpoint, the survival at ten years was 94.5% (95% CI 85.1 to 100), and with aseptic loosening as the endpoint 98.4% (95% CI 93 to 100). The mean American Knee Society score improved from 47.6 (0 to 88) to 72.2 (26 to 100) and for function from 45.1 (0 to 100) to 93.1 (45 to 100). Radiological review failed to detect migration in any of the surviving knees.

The clinical and radiological results of the Medial Rotation TKR are satisfactory at ten years. The increased congruence of the medial compartment has not led to an increased rate of loosening and continued use can be supported.

In order to eliminate the “conflict” that can occur with physiological roll back of the femur on the tibia, most modern knee arthroplasty prostheses are designed to have little conformity between the femoral and tibial surfaces. However, a consequence of this design is paradoxical anterior sliding of the femur on tibia, which can result in clinically significant gait abnormalities. Recent studies show that during movement of the knee, the medial side remains very nearly stable like a ball-in-socket joint, whilst the lateral side moves front to back, rotating around the centre of the medial side. A total knee joint prosthesis designed with these same kinematics may therefore be advantageous. The objective of this study was to investigate the hypothesis that the increased constraint of a medial pivot knee promotes earlier loosening of the prosthesis.

METHODS: This was a retrospective radiographic cohort study. Using our unit’s knee arthroplasty database, all patients with a Freeman-Samuelson 1000 knee arthroplasty (medial pivot design) or a Freeman-Samuelson Modular knee arthroplasty with a minimum follow-up of 2 years were identified, and matched as closely as possible for age, length of follow-up and pre-operative diagnosis (Osteoarthritis, Rheumatoid arthritis or Post-traumatic arthritis). This was a single surgeon series using a standard surgical approach with a posterior cruciate sacrificing technique. Standardised anteroposterior and lateral radiographs taken postoperatively, at 6 months, 1 year and then at yearly intervals, were examined systematically and independently of the senior surgeon (GS). Component migration and radiolucent line scores were allocated as recommended by the Knee Society.

RESULTS: Group 1 (n=55),–Freeman Samuelson Modular design, mean age–70.3 years, mean length of follow-up–4.5 years. Group 2 (n=48),–Freeman Samuelson 1000 design (Medial pivot), mean age–70.4 years, mean length of follow-up–4.3 years. There were no failures in group 1. There was one failure requiring revision of the femoral component in group 2. Radiolucent lines were more prominent and frequent in the tibia, particularly under the medial and lateral plateau’s (KSS zone 1 and 6). There was no significant difference in the overall radiolucent line scores between the two groups (p=0.39, Mann Whitney U test). Similarly we found no difference between radiolucent line progression in the specific tibial zones (1–6 KSS system). Radiolucent lines in the femur were infrequent and insignificant.

CONCLUSION: We found no statistically significant difference between the two designs of knee prosthesis in terms of either total radiolucent line score or rate of radiolucent line progression. The increased constraint of the medial pivot knee prosthesis does not appear to result in an increased incidence of radiographic loosening.

Introduction: Aseptic loosening due to polyethylene wear is a mode of failure in knee arthroplasty. No study has evaluated the roughness of the articulating surface of retrieved femoral components & its role in creation of polyethylene wear. AIM The aim of our study was to investigate the in-vivo changes in the surface roughness of retrieved femoral components. Our hypothesis was that the surface finish of the femoral components, articulating with the polyethylene inserts deteriorated in accordance with the duration of implantation.

Materials and Methods: 22 femoral components, all Freeman-Samuelson prostheses, were retrieved from 18 male and 4 female patients at revision knee surgery. The mean age at revision was 68.4 years and the mean period of implantation was 55.64 months. 18 implants were retrieved for aseptic loosening and 4 for infection. Firstly, the surfaces of femoral components & polyethylene inserts were visually inspected for modes of damage in the articulating areas. The surface finish measurements were performed with a contact stylus profilometer with a 2-mm-radius stylus tip and a cut-off length of 0.8mm. The surface roughness was characterised by measuring Ra(mm), which is the arithmetic mean of the absolute values of the measured height deviations taken within the evaluation area and measured from the main line or surface. Both condyles were examined as separate areas articulating with the tibial components from 0° to 60° and 61° to 120° of knee flexion. Surface roughness (Ra) measurements from the sides of the patellar groove at the top of the femoral flange, which do not articulate either with the patella or tibia, were taken as control. The Ewald method of assessing the orientation of the components was applied to derive the coronal angle of the knee (CAK).

Results: The mean CAK was 7.2° ± 1°. Dull edged parallel scratching and burnishing were the main modes of damage identified on the surface in the articulating areas. Visual analysis of polyethylene inserts failed to identify embedded Polymethyl-methacrylate debris or any other damage, which matched the location of the altered surface finish of the femoral components. The mean Ra values recorded were: Control: Mean-0.0230 mm, SD- 0.00821. Medial Femoral condyle (0° – 60°) – 0.0225 mm, SD – 0.00797, P=0.832 Medial Femoral Condyle (61° – 120°) – 0.0244 mm, SD – 0.00532, P= 0.189 Lateral Femoral condyle (0° – 60°) – 0.0263 mm, SD – 0.00694, P= 0.078 Lateral Femoral Condyle (61° – 120°) – 0.0253 mm, SD – 0.00758, P= 0.286 No statistically significant difference was seen in the mean roughness (Ra) of the articulating areas when compared to that of the control (P< 0.05).

Conclusion: This study showed that the surface finish of these implants did not deteriorate during the period of implantation. On this basis we believe that a well-aligned and well-fixed femoral component, without any accumulated wear debris beneath it, does not require mandatory exchange if the revision is carried out for isolated failure of the tibial prosthesis even if the femoral component has fine scratching or burnishing on its surface.

The aim of this study was to assess whether a femoral component which retained the neck reduced the incidence of leg-length inequality following total hip arthroplasty. A retrospective review was undertaken of 130 consecutive primary total hip arthroplasties performed between April 1996 and April 2004 using such an implant. There were 102 suitable patients for the study. Standardised pre- and post-operative pelvic radiographs were measured by an independent investigator to the nearest millimetre.

The leg-length inequality was reduced from a mean pre-operative value of −0.71 cm to a mean of 0.11 cm post-operatively. Of the 102 patients 24 (23.5%) had an equal leg-length post-operatively, and 95 (93.1%) had a leg-length inequality between −1 cm and 1 cm.

Aim: The aim of our study was to investigate the in-vivo changes in the surface roughness of retrieved femoral components.

Our hypothesis was that the surface finish of the femoral components deteriorated in accordance with the duration of implantation

Materials and method: 22 femoral components (all Freeman-Samuelson prostheses) were retrieved from 18 male and 4 female patients at revision knee surgery. The mean age at revision was 68.4 years and the mean period of implantation was 55.64 months. 18 implants were retrieved for aseptic loosening and 4 for infection. The surfaces of femoral components & polyethylene inserts were inspected for modes of damage in the articulating areas. The surface finish measurements were performed with a stylus profilometer. The surface roughness was characterised by measuring Ra (micron-meter), which is the mean of the measured height deviations within the evaluation area. The articulating surface on both condyles was examined seperately. Ra measurements from the sides of the patellar groove at the top of the femoral flange, which do not articulate either with the patella or tibia, were taken as control. The Ewald method of assessing the orientation of the components was applied to derive the coronal angle of the knee (CAK)

Results: The mean CAK was 7.2° ± 1°. Parallel scratching and burnishing were the main modes of damage on the surface in the articulating areas. Inspection of polyethylene inserts failed to find embedded Polymethyl-methacrylate debris or any other damage, which matched the location of the altered surface finish of the femoral components.

The mean Ra values were:

Control: Mean-0.0230 mm, SD- 0.00821.

Medial Femoral condyle (0 – 60) = 0.0225 mm, SD – 0.00797

Medial Femoral Condyle (61 – 120) = 0.0244 mm, SD – 0.00532

Lateral Femoral condyle (0 – 60) = 0.0263 mm, SD – 0.00694

Lateral Femoral Condyle (61 – 120) = 0.0253 mm, SD – 0.00758

No statistically significant difference was seen in the mean-Ra of the femoral condyles compared to that of the control (P less than 0.05).

Conclusion: The surface finish of these implants did not deteriorate during the period of implantation. On this basis we believe that a well-aligned and well-fixed femoral component, without any accumulated wear debris beneath it, does not require mandatory exchange if the revision is carried out for isolated failure of the tibial prosthesis.

We investigated the changes in surface roughness of retrieved femoral components in 18 men and four women at revision knee surgery. The mean age at revision was 68.4 years and the mean period of implantation was for 55.6 months. Eighteen implants were retrieved for aseptic loosening and four for infection. The surface changes in the articulating areas were inspected visually and the roughness (Ra) analysed with a profilometer. Parallel scratching and burnishing were the two main forms of damage. The mean Ra measurements in the articulating areas showed no statistically significant difference when compared with those in a control area on either side of the patellar groove at the apex of the femoral flange. This suggests that it is not essential to revise a well-fixed and correctly aligned femoral component where the polished surface has become burnished or bears fine parallel scratches, if the revision is conducted solely for failure of the tibial component.

Aims: To demonstrate that tranexamic acid reduces the blood loss incurred as a result of lower limb arthroplasty. Methods: We prospectively studied 30 primary hip and knee arthroplasty patients. Entry criteria were primary joint replacement, exclusion criteria were: a history of bleeding disorders, previous thromboembolic disease or renal insufþciency. The senior author (GS) performed all the operations. Surgical technique and postoperative mobilisation was standardised for both hip and knee arthroplasty cohorts. Tranexamic acid was administered at the time of surgery. The patients had haemoglobin levels assessed preoperatively and a haemoglobin level three days post operatively to allow its stabilisation following surgery. Any blood transfused was noted. Blood was transfused on a case-by-case basis the indications were a haemoglobin less than 8 g/dl or symptoms of anaemia. The results were then compared with a matched population from the bone and joint research unit database. Results: The mean fall in haemoglobin in hip arthroplasty with tranexamic acid was 2.8 ± 0.33 g/dl (95% Conþdence Interval) and 3.85 ± 0.44 g/dl (95% Conþdence Interval) without tranexamic acid this was statistically signiþcant p< 0.05. The mean fall in haemoglobin in knee arthroplasty with tranexamic acid was 1.67± 0.36 g/dl (95% Conþdence Interval) and 2.84 ± 0.35 g/dl (95% Conþdence Interval) without tranexamic acid this was statistically signiþcant p< 0.05. Transfusion requirements were reduced. Conclusions: Tranexamic acid is an inexpensive and effective way of reducing blood loss following hip and knee arthroplasty.

Aims: To compare the in vivo wear rates of the polyethylene inserts of different thicknesses in Freeman-Samuelson (F/S) total knee arthroplasties. Methods: Radiographs of 17 patients with F/S modular prostheses and 6mm thick inserts, 19 patients with 8mm inserts, and 6 patients with F/S1000 (more conformed medial femoral condyle) with 8mm inserts were studied. The distance (polyethylene thickness) between femoral and tibial components was measured from A-P radiographs at 6 months, 3 years and 5 years with correction for magnification and antero-posterior tilting of the tibial tray. Wear rates were calculated. Comparisons were made between the medial and lateral sides of the inserts, between the different thicknesses and between the two types of prostheses. Results: The difference in the wear rate between the medial and lateral side in the 3 groups of polyethylene inserts was shown to be 0.229, 0.054, and −0.044 mm/yr (p> 0.2 in all 3 groups). Between the two thicknesses in the F/SM group, the 6mm group had a higher wear rate than the 8mm group (diff = 0.072 mm/yr, p< 0.05) over 5 years, with the majority of wear occurring in the first 3 years (Diff = 0.098mm/yr, p< 0.05). Between the two types of prostheses used, the wear rate over 5 years was shown to be 0.006mm/yr (p> 0.5). Conclusions: The study showed that the 6mm polyethylene components had a significantly higher rate of wear than the 8mm ones, but there was no significant difference shown between the medial and lateral sides of the inserts and two versions of the prosthesis.

We describe the survival at ten years of 100 femoral components of the Freeman hip prosthesis. It is proximally hydroxyapatite (HA)-coated and was fixed without cement. Radiological assessment identified radiolucent lines (RLLs) and lytic lesions and was used to measure migration.

The criterion of failure was revision or impending revision for aseptic femoral loosening. No femoral components were revised or are awaiting revision for aseptic loosening, giving 100% survival at ten years (95% confidence interval, 95.7 to 100), although 59 were at risk at ten years. Two components were revised for fracture of a ceramic head with damage to the trunnion. Although well fixed in each, for survival analysis we evaluated the hip as if the patient had died.

Twelve acetabular components were revised and at each operation the femoral component was found to be well fixed, was not disturbed and remained in the survival analysis. Three patients were lost to follow-up, and 12 died with well-functioning prostheses. Radiologically, all except one of the components appeared to be well fixed with no RLLs and no lytic lesions at the latest follow-up. The mean vertical migration was 0.4 mm at one year, 0.8 mm at two years and 1.4 mm at ten years. One component had migrated 7.6 mm at ten years (2.1 mm in year 1) and developed RLLs in Gruen zones I and II. The symptoms, however, were only minor and revision was not indicated.

Our study has shown that proximal HA coating gives effective fixation for a femoral component.

We have reviewed 29 patients (30 hips) who had undergone revision total hip arthroplasty using a Freeman metal-backed acetabular component and acetabular impaction allografting. The mean follow-up was for 15.3 years (12 to 17).

Five patients (5 hips) died with the prosthesis in situ and four (4 hips) were lost to follow-up. Twelve hips had failed and in the remaining nine there were minor symptoms. The mean time to failure requiring further surgery was nine years. Excluding patients who were lost to follow-up or had died, 72% of the hips were radiologically loose at the last review. The commonest pattern in those requiring revision was failure of the reinforcement ring in adduction with remodelling of the medial wall.

Of the nine patients who had not undergone revision, one with bilateral replacements had no current radiographs and only three of the remaining seven replacements had no radiological signs of loosening.

The short-term results for this technique have been reported to be satisfactory, but in the long term they are not. The factors associated with failure include the design of the prosthesis, which has been implicated in disappointing long-term results when used in primary arthroplasty, but not with the frequency of failure found in this series. It seems that the reliance on peripheral screw fixation over a bed of allograft without bridging the graft does not provide sufficient stability to allow incorporation of the graft.

We have compared the survival and radiological outcome at ten years after total hip replacement using two techniques for preparing the femoral canal. The same prosthesis was used throughout and all operations were performed by the same surgical team. In technique 1 the canal was over-reamed by 2 mm and in technique 2 it was reamed to the same size as the prosthesis. Technique 1 was performed on 92 patients and technique 2 on 97 patients.

The survival at ten years was 97.2% (90.6 to 99.2) for technique 1 and 98.8% (92.9 to 99.8) for technique 2. Vertical migration was greater in technique 1 (1.8 mm versus 1.0 mm at five years; p = 0.36). There were significantly more lytic lesions and radiolucent lines at five years (p = 0.0061) with technique 1. We conclude that technique 2 is not worse and may produce better long- term results than current teaching suggests.

Twenty-nine patients (30 hips) with uncemented acetabular impaction allografting contained behind a metal backed component screwed to the pelvis at revision hip arthroplasty were reviewed at 12 to17 years (average 15.3 years) follow up. Five patients had died with the prosthesis in situ, 4 patients were lost to follow up, 13 patients had failed requiring further revision (only one failed prior to 5 years) and 9 survivors were minimally asymptomatic. The mean time to failure warranting further surgery was 9 years.

Analysis of available serial radiographs (24 cases) demonstrated signs of loosening (migration, progressive radiolucent lines, screw breakage) in 54% of the latest radiographs of all cases. Removing those lost to follow up or deceased, 72% were radiologically loose (in the intact asymptomatic group 57% could be defined as loose). Additionally, in 70% of the cases the acetabular component tended to fail in a varus manner as the medial wall remodelled.

These results indicate as previously published, short term results for this technique are satisfactory but in the long term they are not. Factors associated with this include the pressfit nature of the polyethylene liner which has been implicated in disappointing long term results for this prosthesis in primary applications, but not of the level of failure encountered in the current series. This experience suggests that the reliance on screw fixation over a bed of allograft in the absence of cement supplementation does not provide sufficient stability for reliable bone graft incorporation.

The method reported above should be abandoned.

This report concerns an operative technique using inexpensive pre-polymerised cement discs as a means of addressing the bone loss from the posterior femoral condyles found during revision total knee replacement.

Bone lost from the posterior condyles in the loosened femoral component of a total knee replacement enlarges the flexion gap at revision. Downsizing the femoral component to fit the remaining bone requires a thicker tibial insert and a proximalised new femoral component to maintain balanced gaps in flexion and extension. Patella infera results from this proximalisation of the joint line and interferes with the extensor apparatus.

Some knee systems offer customised components with thickened posterior femoral condyles or provide the surgeon with the option of adding metal augments to the femoral component to manage the posterior femoral bone loss.

This technique has been applied to ten cases (follow- up ranging from 15 to 46 months) in which inexpensive pre-polymerised cement spacers were incorporated into the posterior femoral cement mass. This allowed the use of primary stemmed components with preservation of the original joint line position.

No case has resulted in loosening although two cases have required further revision due to recurrence of their original infection. At revision of these cases the cement discs remained firmly incorporated in the cement mass.

We conclude that this technique is reliable, inexpensive and could be applied to other prosthetic varieties.

We studied 185 total hip replacements and related the identification of radiolucent lines (RLLs) at two years to the later development of lytic lesions and loosening. Linear polyethylene wear was also measured.

RLLs appeared in 34 hips at a mean of 2.0 years after operation, and lytic lesions in ten hips at 5.7 years. Of 151 THRs without RLLs there was neither rapid migration nor loosening and only one developed a possible lytic lesion. Of 23 hips with non-progressive RLLs there was neither rapid migration nor loosening, but six developed a lytic lesion. By contrast, 11 THRs with progressive RLLs migrated rapidly and seven developed a lytic lesion. Six THRs with progressive RLLs failed. The wear rates were the same in all groups, although limited numbers were available for study.

If the surgeon achieves secure initial fixation as shown by slow or no migration and no RLLs during the first two years, it is likely that no lytic lesions will develop by five years or aseptic loosening by ten years. If an imperfect, but adequate, interface is achieved, as shown by slow migration and non-progressive RLLs lytic lesions adjacent to the RLLs may develop by five years, but aseptic loosening will be unlikely at ten. Insecure initial fixation, as shown by more rapid migration and progressive RLLs at two years, is likely to lead to the formation of lytic lesions at five years and loosening at ten. The outcome after THR is therefore determined at the initial operation and may be predicted at two years. The presence of lytic lesions reflects soft tissue at the interface as shown by the RLLs which accompany and promote loosening but, in our study, did not cause it.

We report a ten-year rate of survival of 96% for the cemented Freeman-Samuelson knee arthroplasty in patients from the Swedish Knee Registry and the Royal London Hospital with revision for aseptic loosening as the criterion for failure.

Our aim was to analyse the influence of the size, shape and number of particles on the pathogenesis of osteolysis. We obtained peri-implant tissues from 18 patients having revision surgery for aseptically loosened Freeman total knee replacements (10), Charnley total hip replacements (3) and Imperial College/London Hospital double-cup surface hip replacements (5). The size and shape of the polyethylene particles were characterised using SEM and their concentration was calculated. The results were analysed with reference to the presence of radiological osteolysis.

The concentration of polyethylene particles in 6 areas with osteolysis was significantly higher than that in 12 areas without osteolysis. There were no significant differences between the size and shape of the particles in these two groups.

We conclude that the most critical factor in the pathogenesis of osteolysis is the concentration of polyethylene particles accumulated in the tissue.

We reviewed a consecutive series of 527 uninfected hip replacements in patients resident in the UK which had been implanted from 1981 to 1993. All had the same basic design of femoral prosthesis, but four fixation techniques had been used: two press-fit, one HA-coated and one cemented. Review and radiography were planned prospectively. For assessment the components were retrospectively placed into two groups: those which had failed from two years onwards by aseptic femoral loosening and those in which the femoral component had survived without revision or recommendation for revision.

All available radiographs in both groups were measured to determine vertical migration and examined by two observers to agree the presence of radiolucent lines (RLLs), lytic lesions, resorption of the neck, proximal osteopenia and distal intramedullary and distal subperiosteal formation of new bone. We then related the presence or absence of these features and the rate of migration at two years to the outcome with regard to aseptic loosening and determined the predictive value of each of these variables.

Migration of ≥2 mm at two years, the presence of an RLL of 2 mm occupying one-third of any one zone, and subperiosteal formation of new bone at the tip of the stem were predictors of aseptic loosening after two years. There were too few lytic lesions to assess at two years, but at five years a lytic lesion ≥2 mm also predicted failure. We discuss the use of these variables as predictors of femoral aseptic loosening for groups of hips and for individual hips.

We conclude that if a group of about 50 total hip replacements, perhaps with a new design of femoral stem, were studied in this way at two years, a mean migration of < 0.4 mm and an incidence of < 10% of RLLs of 2 mm in any one zone would predict 95% survival at ten years.

For an individual prosthesis, migration of < 2 mm and the absence of an RLL of ≤2 mm at two years predict a 6% chance of revision over approximately ten years. If either 2 mm of migration or an RLL of 2 mm is present, the chances of revision rise to 27%, and if both radiological signs are present they are 50%. If at five years a lytic lesion has developed, whatever the situation at two years, there is approximately a 50% chance of failure in the following five years.

Our findings suggest that replacements using a limited number of any new design of femoral prosthesis should be screened radiologically at two years before they are generally introduced. We also suggest that radiographs of individual patients at two years and perhaps at five years should be studied to help to decide whether or not the patient should remain under close review or be discharged from specialist follow-up.

We compared the radiological appearances and survival of four methods of fixation of a femoral stem in 538 hips after follow-up for five or ten years. The fixation groups were: 1) press-fit shot-blasted smooth Ti-Al-V stem; 2) press-fit shot-blasted proximally ridged stem; 3) proximal hydroxyapatite (HA) coating; and 4) cementing.

Survival analysis at five to ten years showed better results in the HA-coated (100% at five to six years) and cemented stems (100% at 5 to 6 years) than in the two press-fit groups. There was a higher mean rate of migration in the smooth and ridged Ti-Al-V shot-blasted press-fit groups (0.8 mm/year and 0.6 mm/year, respectively) when compared with the HA-coated and cemented prostheses (both 0.3 mm/year). More radiolucent lines and osteolytic lesions were seen in the press-fit groups than in either the HA-coated or cemented implants, with a trend for a lower incidence of both in the HA compared with the cemented group. Proximal osteopenia increased in the press-fit and cemented prostheses with time, but did not do so in the HA group. There was a higher incidence of resorption of the femoral neck with time in the cemented group than in the other three.

We conclude that the HA and the cemented interfaces both provide secure fixation with a trend in favour of HA. The cemented prosthesis meets the suggested National Institutes of Health definition of ‘efficacious’ at ten years.

We report the radiological and clinical outcome of a press-fit (SLF) acetabular component at two to three years in two groups of patients having primary total hip replacement. In 69 the implant was coated with hydroxyapatite (HA) and in 40 it was uncoated. The stability of the cup was assessed by measurement of proximal migration and change in the angle of inclination.

The clinical results in the two groups did not differ significantly, and the mean proximal linear wear was similar in both. Fewer radiolucent lines (RLLs) were seen on the radiographs of cups coated with HA.

The mean proximal migration was studied by calculating regression lines for each patient using migration measurements: for the SLF+HA group the mean slope was 0.06 mm/year and for the SLF–HA group 0.20 mm/year (p = 0.22). The change in the angle of inclination during follow-up was also consistently smaller in HA–coated cups. Using regression methods the SLF+HA group had a mean slope of 0.08°/year and the SLF-HA group 0.44°/year (p = 0.023).

Partial HA coating appeared to have no effect on the clinical outcome or on the rate of wear of polyethylene, but there was a trend towards a reduced rate of proximal migration, and a significant reduction in rotational migration and the number of radiolucent lines. This suggests that HA coating enhances the stability of this acetabular component.