Resurfacing arthroplasty for patients with osteonecrosis.

The suitability of third-generation metal-on-metal hip resurfacing products for patients with a primary diagnosis of osteonecrosis has been debated. The preservation of femoral head bone stock for femoral prosthetic support is essential for the long-term stability of implants. A modern hip resurfacing system was implanted in 1148 hips as part of a United States multicenter investigational device exemption study. Of these, 116 hips had a preoperative diagnosis of osteonecrosis and were compared to 1023 hips with osteoarthritis. Survival rates were not significantly different (95.9% and 95.8% at 24 months for osteoarthritis and osteonecrosis respectively, p = 0.46). Resurfacing arthroplasty for patients with osteonecrosis appears to be a reasonable alternative, taking into consideration implant size, patient gender, and size of femoral deficiency. Further characterization is needed to identify those specific patients with osteonecrosis for whom resurfacing arthroplasty would be appropriate.

Results and lessons learned from a United States hip resurfacing investigational device exemption trial.

BACKGROUND: Improvements in metal-on-metal bearings have made hybrid hip surface replacement a potential alternative for the young active patient with end-stage hip disease. Possible advantages include greater hip joint stability, bone preservation, and decreased osteolysis. In this study, we compared the clinical and radiographic results of a new resurfacing device with those in a historical group of standard total hip arthroplasties. METHODS: In 2001, the Cormet 2000 Hip Resurfacing Investigational Device Exemption study was initiated at twelve centers. A total of 337 patients treated with unilateral hip surface replacement with the Cormet device were enrolled in that study. These patients were compared with 266 patients in a previous study who had undergone unilateral total hip arthroplasty with ceramic bearing surfaces. Clinical and radiographic results were compared at similar time intervals. A newly recommended performance standard, the composite clinical success score, was used to assess non-inferiority of the hip resurfacing compared with the total hip arthroplasty used in the historical comparison population. RESULTS: At the time of follow-up, at a minimum of two years, the Harris hip scores were comparable between the resurfacing and total hip arthroplasty groups. Statistical evaluation of the composite clinical success scores confirmed the non-inferiority hypothesis. Revision was required in twenty-four patients in the resurfacing group and five patients in the total hip arthroplasty group. The most common cause of revision following resurfacing was failure of the femoral component (fracture of the femoral neck or loosening of the femoral component). CONCLUSIONS: Careful review of this study population revealed several important criteria for successful introduction of this resurfacing device into the United States. These include careful patient selection based on clinical and radiographic parameters and attention to various surgical details of implantation. These findings can be used to focus the training process for surgeons who wish to add implantation of this device to their surgical armamentarium. Such efforts should help to ensure safe and effective introduction of this new technology.

Midterm results with the PFC Sigma total knee arthroplasty system.

We prospectively studied 207 consecutive patients (284 knees) undergoing total knee arthroplasty (June 1996 to December 1997) with a cemented tricompartmental Sigma PFC (DePuy Orthopaedics, Warsaw, Ind) total knee arthroplasty via a standard procedure (median follow-up, 87 months). Cruciate-retaining (272 knees, 96%) and cruciate-substituting (12, 4%) implants were used. There was one revision secondary to a ligament disruption after a fall. No implants were radiographically loose or at risk for loosening. Radiolucencies (none>2 mm or progressive) were shown on anteroposterior (7% of medial tibias) and lateral (17% of posterior femora) radiographs. Knee Society pain scores improved significantly (preoperative median, 20 points; postoperative median, 50 points [P<.001]). The PFC Sigma Knee system has excellent midterm durability.