Extra-long femoral heads as a surrogate marker for revision risk in primary total hip arthroplasty

The effect of femoral head length on implant survival in total hip arthroplasty (THA) has been little studied so far. Longer heads may increase taper corrosion and reflect intraoperative complexity. This study evaluated factors associated with the use of extra-long heads (≥ XL) and their impact on implant survival. We analyzed 562,001 primary THA from the German Arthroplasty Registry. Subgroup analyses were performed by hospital annual primary THA volume (≤ 250, 251–500, ≥ 501), surgical indication (primary osteoarthritis [OA] vs. femoral neck fracture [FNF]), and fixation method (cemented vs. cementless). Logistic regression identified factors associated with ≥ XL head use, and implant survival was compared between head lengths using Kaplan–Meier analysis in both subgroups and the overall cohort. The use of ≥ XL femoral heads decreased with increasing hospital volume (5.4% low, 4.5% medium, 3.0% high; p < 0.001). Rates were higher in FNF than OA across all volumes (8.1% vs. 4.7% in low-volume hospitals; 5.0% vs. 2.7% in high-volume hospitals). Cemented fixation was independently associated with higher odds of ≥ XL head use (OR 1.14, 95% CI 1.09–1.18, p < 0.001), with additional predictors including male sex (OR 2.13, 95% CI 2.06–2.19), BMI ≥ 40 (OR 1.94, 95% CI 1.77–2.12), higher Elixhauser comorbidity score (OR 1.09, 95% CI 1.04–1.15), and surgery for FNF (OR 1.92, 95% CI 1.83–2.02), while treatment at high-volume hospitals was associated with lower odds (OR 0.56, 95% CI 0.54–0.58). Kaplan–Meier analysis revealed higher cumulative revision rates with ≥ XL heads (7.2% vs. 4.5% at 9 years), consistent across all subgroups. The use of femoral heads ≥ XL was independently associated with lower hospital THA volume, femoral neck fracture, cemented fixation, male sex, higher BMI, and greater comorbidity burden. Their implantation was also linked to higher revision rates, suggesting that ≥ XL heads may serve as a surrogate marker for increased revision risk after primary THA.