Polyethylene hip resurfacing in patients with lower leg amputations.

Background: Patients with lower leg amputations tend to develop hip osteoarthritis more frequently and at a younger age than the general population. Some amputee patients choose hip resurfacing arthroplasty (HRA) because of its bone conservation compared to total hip arthroplasty. Because of their altered gait mechanics, HRA might provide these patients with stability and functional benefits compared to total hip arthroplasty. The hypothesis is that HRA is a useful and successful alternative to total hip replacement for lower extremity amputees requiring hip implant surgery. The aim of this study was to evaluate if HRA is a successful alternative to total hip replacement in this patient population with altered gait mechanics. Methods: This observational study reviewed the records of 39 amputee patients (45 hips) who underwent HRA using a polyethylene acetabular component. Trauma, tumor, vascular disease, infection, and congenital conditions were indications for amputation. Above knee and below knee amputations were included. Patients were evaluated using the Hip Disability and Osteoarthritis Outcome Score (HOOS), Harris Hip Score (HHS), Minimal Clinically Important Difference (MCID), and Patient Acceptable Symptomatic State (PASS). Follow-up included implant survivorship, complications, and radiographic evaluation for implant osseointegration, wear, position, and leg length. Results: Mean follow-up was 13 years (range, 3-40 years). Mean HOOS was 90, mean HHS was 92; 92% of patients achieved MCID (which required an improvement of 38 points in HOOS and 37 points in HHS), and 85% achieved PASS. There was one revision for femoral head avascular necrosis, one conventional polyethylene exchange for wear, and six temporary complications. Thirty-three (85%) patients had a leg length difference of >1 cm (range, 1-4.7 cm); the prosthetic limb was shorter in 25 (75%) and longer in 8 (25%). No patient was concerned with leg length difference and there were no differences in hip scores and implant survivorship based on limb length. Conclusions: HRA is a demanding procedure that can be successful for patients with lower limb amputations. An unexpected finding was that leg length differences are common in these patients. Unequal leg lengths did not adversely affect implant survivorship or patient-reported outcomes.