Durom hip resurfacing at 15 years : predictive factors for failure.

Aims: A range of metal-on-metal hip resurfacing (MoM-HR) implants have shown good functional outcomes, but some have been associated with adverse reactions to metal debris (ARMD) and early failure, requiring regular follow-up and monitoring of the blood metal ion levels. The aim of this study was to report the minimum 15-year survival of the Durom hip resurfacing system (Zimmer Biomet, USA), the functional outcome, and factors which were predictive of failure.

Methods: A consecutive series of patients undergoing Durom MoM-HR at a single centre between January 2000 and December 2008 were included. Demographic variables, the size of the implant, radiological parameters, and the most recent blood metal ion levels were collected. The primary outcome measure was failure; secondary outcome measures included the Oxford Hip Score (OHS). Multivariable logistic regression was used to predict failure and identify the factors most strongly associated with failure.

Results: A total of 695 hips in 597 patients, 61.2% of whom were male, were included. The mean age of the patients was 51.5 years (SD 8.7). Survival at a mean follow-up of 15.2 years (SD 1.9) was 86.6% (602 of 695 hips). Implant survival was significantly increased in males (92.2% (95% CI 89.7 to 94.8) vs 77.8% (95% CI 72.8 to 82.7); p < 0.001) and with femoral components sized ≥ 50 mm (91.7% (95% CI 88.7 to 94.7) vs 82.3% (95% CI 78.4 to 86.2); p < 0.001). Failure was mostly due to aseptic loosening (42 hips; 6%) and ARMD (27 hips; 3.9%). The mean postoperative OHS was 31.9 (SD 13.5) for patients requiring revision and 41.8 (SD 9.2) for those not requiring revision (p < 0.001). Predictive factors of failure in the regression model included sex, the angle of inclination and migration of the acetabular component, the postoperative OHS and the blood chromium ion levels (Pseudo-R 0.279). Standardized regression coefficients were greatest for migration of the acetabular component (0.855) and OHS (-0.606).

Conclusion: This study presents the longest reported follow-up for the Durom MoM-HR, with excellent survival and functional outcomes at 15 years' follow-up in males and with ≥ 50 mm femoral components. Most failures were due to aseptic loosening. Migration of the acetabular component and symptomatology (OHS) were the factors which most strongly predicted failure.