Hip resurfacing (HSR) is an orthopedic procedure designed to treat hip arthritis while conserving more of the patient’s natural bone structure compared to a total hip replacement (THR). Unlike THR, which removes the head and neck of the femur and replaces it with a stemmed component, HSR involves reshaping the femoral head and capping it with a smooth metal covering, similar to placing a crown on a tooth. This bone-sparing approach aims to maintain more natural hip biomechanics, particularly for younger, active individuals. The primary concern for patients considering this surgery remains the longevity and long-term performance of the implant.
Expected Lifespan and Survival Rates
Data collected by national registries provide the most reliable estimate for the expected lifespan of a hip resurfacing implant. Longevity is measured by the survival rate, which is the percentage of implants that have not been removed or replaced (revision surgery) after a certain number of years. For modern metal-on-metal resurfacing systems, the statistical survival rate is consistently high in the medium term.
Reports from sources like the Australian Orthopaedic Association National Joint Replacement Register (AOANJRR) indicate a 10-year survival rate of approximately 93.4% for the most commonly used resurfacing device, with other pooled analyses showing similar results (around 95.5%). While these figures reflect device survival, functional survival—the patient’s continued satisfaction and pain-free activity—is also important.
Longer-term data, while less abundant, suggests that durability extends well into the second decade for many patients. Data from the Finnish Arthroplasty Register indicates an overall 10-year survival rate of 86%. This longevity is excellent, particularly for a procedure often performed in younger, higher-demand individuals.
Patient and Procedural Factors Affecting Longevity
The lifespan of a hip resurfacing implant is heavily influenced by individual patient characteristics and technical surgical factors. Patient-specific elements, such as age and gender, are strong predictors of long-term success. Generally, younger, larger male patients with strong bone quality tend to have the most favorable outcomes.
Women, particularly those with smaller hip bones, experience a higher rate of revision due to factors like lower bone density and challenges in achieving optimal component positioning. The risk of failure is also higher in patients requiring smaller component sizes. Men aged less than 60 who receive a femoral component size of 48 millimeters or larger demonstrate the best survival rates.
Procedural factors, especially the precision of the surgical technique, also play a significant role in determining longevity. The accurate alignment and placement of the femoral and acetabular (socket) components are paramount for minimizing wear and tear. The modern metal-on-metal design allows for a large femoral head size, which contributes to greater hip stability and a lower risk of dislocation.
Causes of Implant Failure Requiring Revision
When a hip resurfacing implant fails, it is typically due to specific biological or mechanical issues that necessitate revision surgery to a total hip replacement. One common mechanical reason for failure is aseptic loosening, where the implant detaches from the surrounding bone without infection. This loosening is often related to the body’s reaction to microscopic wear particles, which causes bone loss around the implant.
A unique complication is a fracture of the femoral neck, the bone preserved during the HSR procedure. The risk of this fracture is low (estimated between 1% and 2%), but it immediately requires conversion to a total hip replacement. This risk is heightened in patients with poorer bone quality, such as older individuals or those with pre-existing conditions.
Another significant cause of revision, particularly for metal-on-metal devices, is an Adverse Reaction to Metal Debris (ARMD). ARMD involves the release of metallic ions and particles from the bearing surfaces, triggering a local inflammatory response in the surrounding soft tissues. This reaction can lead to the formation of fluid-filled masses (pseudotumors) and cause tissue damage and pain, requiring implant removal. Infection remains a potential, though less frequent, reason for revision, as with any joint replacement procedure.