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.