Objectives

Porous metal surfaces have been a popular option for acetabular component fixation in total hip arthroplasty (THA). New THA component designs are introduced periodically with the expectation of better wear properties and survivorship. Since its approval for use in 2002 there have been few clinical outcome studies published on the Pinnacle acetabular cup system. We hypothesised that the hemispherical porous coated Pinnacle acetabular cup system with a range of cup options and bearing surfaces would give us predictably good fixation and survivorship at five years post implantation.

Purpose

The patella provides a mechanical advantage to the knee extensor mechanism. Patellectomy, performed for trauma or patellofemoral arthrosis, does not preclude the development of tibiofemoral arthrosis. Total knee arthroplasty is the mainstay of treatment for tibiofemoral arthrosis. The purpose of this study was to evaluate the outcomes of total knee arthoplasty in patients who previously underwent patellectomy.

Purpose: The purpose of this study was to investigate the mid to long term (minimum 10 years follow-up) survivorship of the AMK total knee arthroplasty (TKA), as well as determine the effect of implant fixation on outcome.

Method: Between 1988 and 2000, 1074 AMK primary total knee arthroplasties were preformed on 843 patients. All diagnosis included, the distribution was 90% osteoarthritis (971), 7% inflammatory arthritis (76) and 3% other diagnoses (27). Average time from surgery was 15 years (range 10–21 years). Average age at primary procedure was 68 years (range 22–99). Fifty-six percent were female (599) and 44% male (475). Preoperative alignment consisted of 56% varus (601) and 17% valgus (182). Ninety percent (968) had patella resurfacing performed, 62% (661) received cemented TKA fixation, on 32% hybrid fixation (cemented femoral component, cementless tibial tray) was performed and 6% (66) had cementless fixation. Two hundred thirty-seven cases were deceased before 20 years follow-up (22%).

Results: At 10 to 21 years follow-up, 129 revisions were performed (12%). The most common reasons for revision were polyethylene wear, particle induced osteolysis, instability and pain (43% of revisions). Implant fixation significantly influenced the rate of revision with cemented fixation having a 6.7% rate of revision (44/661), hybrid fixation a 14% revision rate (47/336) and cementless a 36.4% revision rate (24/66). Excluding infections (11 cases), overall Kaplan-Meier survivorship at five, 10 and 15 years was 96.4%, 91.9% and 85.8%, respectively. At 20 years the predicted Kaplan-Meier survivorship was estimated at 83.5% (no revisions beyond 17.5 years). Cemented fixation was associated with significantly better survivorship than hybrid and cementless fixation (p< 0.0001). At 5, 10 and 15 years cemented AMK TKA survivorship was 97.5%, 94.9% and 91.9% respectively (no revision performed beyond 13.5 years). For hybrid fixation the survival at 5, 10 and 15 years was 97.8%, 92.2% and 85.1% respectively. Cementless AMK THA had a Kaplan-Meier survivor-ship of 88.9%, 78.2% and 57.4% at 5, 10 and 15 years respectively.

Conclusion: Cemented fixation had superior outcomes compared to cementless and hybrid fixation with the most common reasons for revision being polyethylene wear and osteolysis. To our knowledge this the first medium to long term follow-up of the AMK TKA and it demonstrates that method of fixation had a major influence on revision rates and survivorship.

Purpose: The results of medial unicompartmental knee replacement have been reported as excellent over the intermediate term with both fixed and mobile bearing designs. However not all publications report equal success, with different outcomes also reported between mobile and fixed bearing designs. The purpose of this study was to compare the outcomes of mobile and fixed bearing medial unicompartmental arthroplasties.

Method: We evaluated the results of 230 consecutive medial unicompartmental knee arthroplasties (UKA) designs performed between 1989 and 2006 at a single academic centre (London Health Sciences Centre). Eighty mobile bearing UKA (63 patients, mean follow up3.2 years) and 160 fixed bearing UKA (117 patients, mean follow up 6.2 years) were reviewed. The mean age of the patients at the time of surgery was 66 years. Forty nine patients died at a mean of 12.7 years after the index arthroplasty. Patients were evaluated clinically using the Knee Society, WOMAC and SF12 outcome scores and radiographically using the Knee Society rating system.

Results: In the fixed bearing group 21 knees underwent revision at a mean of 6.9 years after the index procedure. In the mobile bearing group 7 knees underwent revision at a mean of 2.6 years. The mean Knee Society knee and function scores for the patients who had not had a revision improved in both groups, with the fixed bearing group mean function and Knee Society Scores improving from 53 and 48 points preoperatively to 80 and 93 points at the time of the most recent evaluation. In the mobile bearing group the mean function and Knee Society Scores improved from 55 and 44 points preoperatively to 85 and 91 points at the time of the most recent evaluation. The five year cumulative survival rates were 96% (SE +/− 0.18) and 89% (SE +/− 0.46) for the fixed and mobile bearing designs respectively, with ten year cumulative survival rates of 85% (SE +/− 0.35) in the fixed bearing group using an endpoint of revision to tricompartmental knee arthroplasty.

Conclusion: Both bearing designs of medial unicompartmental knee arthroplasty provided excellent pain relief and restoration of function in carefully selected patients and demonstrated durable implant survival over the midterm. In this study the fixed bearing designs demonstrated improved survivorship over the mobile bearing designs at 5 years. This may be related to the learning curve of the different bearing systems.

Many authors have recommended undercorrection of the deformity when carrying out unicompartmental knee arthroplasty (UKA). The isolated effect of alignment of the knee on the outcome of UKA has, however, received little attention.

We reviewed 185 UKAs at a minimum of five years after surgery. They had been carried out by a single surgeon using metal-backed tibial components in the management of arthritis of the medial compartment. We measured the tibiofemoral angle (TFA) before and at four months after operation and at the most recent assessment. The amount of correction of the TFA and any subsequent loss were recorded.

While adjusting for the effects of age, weight and gender of the patients and the type and thickness of the implants, the mean correction was significantly less for those with a Marmor rating of failure (6.8°) than for those rated excellent (9.2°). The mean correction was also significantly less for patients with a Marmor rating of failure (6.8°) than for those rated poor (11.1°). The mean correction for the UKAs which were revised (6.6°) was significantly less than for those not revised (9.1°). Additionally, revised UKAs had a significantly higher percentage (63%) of thinner tibial implants (< 8 mm) than the surviving UKAs (27%). These findings suggest that undercorrection of the TFA in UKA of the medial compartment should be avoided, particularly if a thin tibial polyethylene insert is used.