Introduction

Unicompartmental knee arthroplasty (UKA) is a successful procedure for medial compartment osteoarthritis (OA). Recent studies using the same implant report a revision rate of 2.9%. Other centers have reported revision rates as high as 10.3%. The purpose of this study was to retrospectively review the clinical results of Oxford Phase 3 UKA's performed in the setting of isolated medial compartment OA and to compare our results to the previous mid-term studies. Our secondary goal was to determine reasons for revision and evaluate selected independent predictors of failure.

Introduction and Aims: Problem: The timing of liner exchange for retroacetabular osteolysis in THA remains uncertain. Liner exchange should be done before the shell becomes loose.

Purpose: To determine the radiographic quantity of osteolysis that will predict impending loosening of the cementless shell.

Hypothesis: Osteolytic areas differ between loose and stable shells.

Method: Between 1992 and 2002, 71 cementless shells of the same design were revised at our institution; 46 were for aseptic retroacetabular osteolysis. Radiographs and a computer-assisted technique were used to quantify osteolytic areas and percent of shell circumference associated with lesions. Implant stability was confirmed intra-operatively.

Results: Of 26 stable and 20 loose shells, the average area of osteolysis on AP radiographs showed no significant difference (Stable 591mm2, Loose 630 mm2, p greater than 0.05); whereas, lateral radiographs demonstrated a significant difference (Stable 546 mm2, Loose 837 mm2, p 0.05). The percentage of shell circumference with associated osteolysis on AP and lateral films demonstrated a significant difference (AP: Stable 60, Loose 75, p 0.042; LATERAL: Stable 49, Loose 73, p 0.016). Diagnostic criteria of 50 percent shell circumference associated with osteolysis on AP films has sensitivity 1.0, specificity 0.27, while the same criteria on lateral films has sensitivity 0.84, specificity 0.54 for shell loosening.

Conclusion: Percent of shell circumference with surrounding osteolysis appears to be more predictive of cementless shell loosening than the area of osteolysis. When greater than 50 percent of the shell circumference has osteolysis on AP or lateral films, liner exchange is necessary.

Introduction and Aims: Cemented femoral revision total hip arthroplasty has been associated with early mechanical failure by aseptic loosening. This study was performed to determine the long-term survival of cemented femoral revision arthroplasty and to identify factors predictive of failure.

Method: One hundred and twenty-nine cemented femoral revision cases were reviewed to determine component survival. Ninety-seven hips with a minimum follow-up of five years were included for survival analysis and tests of significance. Harris hip scores were used to quantify clinical outcomes. Complete radiographic series were reviewed. Kaplan-Meier survival curves were calculated. Clinical and surgical factors were analysed to determine if they were predictive of failure.

Results: Individual Harris hip scores improved to a mean of 71 at the most recent follow-up from a mean pre-operative score of 52 (p< 0.001). Kaplan-Meier survival at 10 years was 91%, with revision for aseptic loosening of the femoral component as the endpoint and 71% with mechanical failure as the endpoint. Patients older than 60 years experienced greater long-term component survival and less pain than patients younger than sixty years (p< 0.05). Good quality post-operative cement mantles were associated with better long-term radiographic fixation (p< 0.001). Poor femoral bone quality was significantly associated with an increased rate of re-revision for aseptic loosening (p=0.021).

Conclusion: Revision femoral THA with cement remains an option in selected patients with acceptable 10-year survival and fair radiographic fixation. Patients demonstrated acceptable clinical outcomes at 10 years and few experienced significant pain. The best results may be achieved in older patients with adequate bone stock and modern cementing techniques.

Introduction and Aims: Problem: Patellar resurfacing in TKA remains controversial. Purpose: To evaluate the results of resurfacing/non-resurfacing of the patella in a randomised controlled clinical trial at a minimum of 10 years of follow-up.

Method: One hundred knees (90 patients) with osteoarthritis were enrolled in a prospective randomised controlled double-blinded trial using the same posterior cruciate retaining total knee replacement. Patients were randomised to resurfacing or non-resurfacing of the patella. Evaluations were performed pre-operatively and yearly to a minimum of 10 years (range 10.1–11.5 years) postoperatively. Disease-specific (Knee Society Clinical Rating System), functional (stair climbing, knee flexion/extension torques, patellar examination) outcomes were measured. Patient satisfaction, anterior knee pain, and patellofemoral questionnaires were completed. Intra-operative grading of the articular cartilage was performed.

Results: No patients were lost to follow-up; 46 knees remained alive. Nine revisions (9/90–10%) were performed – 7/48 (15%) in the non-resurfaced and 2/42 (5%) in the resurfaced group. Three knees in the non-resurfaced group were revised to a resurfaced patella for anterior knee pain. One resurfaced patella was complicated by AVN and fracture, requiring revision. No significant difference was found between the groups regarding revision rates, KSCR score, functional, satisfaction, anterior knee pain, patellofemoral, and radiographic outcomes. Intraoperative cartilage quality was not a predictor of outcome.

Conclusions: This study represents the longest follow-up to date of a randomised controlled clinical trial to examine patellar resurfacing in TKA. The results showed no significant difference between the groups for all outcome measures at a minimum of 10 years.

Introduction and Aims: Polyethylene wear in total hip arthroplasty (THA) is frequently associated with wellfixed cementless implants. Purpose: To evaluate the clinical and radiographic results of the isolated liner exchange (ILE) procedure in revision THA via the direct lateral surgical approach.

Method: A prospective study of 24 hips that underwent an ILE revision procedure via the direct lateral approach was conducted. Accessible osteolytic lesions were managed with curettage and bone grafting. Clinical data including Harris hip score, WOMAC Index, SF-12, and radiographic analysis were recorded. The area of osteolytic lesions was calculated using a new software program.

Results: This is the first study to our knowledge to report on the results of the ILE procedure performed via the direct lateral surgical exposure. Twenty-three patients underwent 24 revisions with an ILE. At mean follow-up of 40 months, all osteolytic lesions had regressed. Harris hip scores improved from 69 to 83. WOMAC indices improved from 37 to 24. No dislocations have occurred. Two patients have required revision. Isolated liner exchange for polyethylene wear is a promising technique that avoids the removal of well-fixed acetabular implants. The increased dislocation rate associated with this revision THA procedure may be reduced and osteolytic lesions may be successfully debrided and bone grafted through the direct lateral approach.

Conclusion: The ILE procedure, when performed via the direct lateral surgical approach, may reduce the dislocation rate commonly reported via the posterolateral exposure with this procedure. Retention of well-fixed implants and bone grafting preserves bone stock and adequately addresses osteolytic lesions at revision surgery through this exposure.