Clinical outcomes of transposition osteotomy of the acetabulum in patients aged 50 years or older with hip dysplasia

Aims: To clarify whether transposition osteotomy of the acetabulum (TOA) in patients aged ≥ 50 years with hip dysplasia provides clinical, radiological, and patient-reported outcomes comparable with those in younger patients. Methods: Among 615 patients undergoing TOA between November 1998 and July 2019, 131 patients aged ≥ 50 years were propensity score-matched 1:1 to 131 patients aged < 50 years using sex, BMI, preoperative modified Harris Hip Score (mHHS), Tönnis grade, and lateral centre-edge angle. Matching was repeated with controls aged < 45 years. Clinical and radiological outcomes, joint survival, and patient-reported outcome measures (PROMs) were compared. Failure was defined as progression to Tönnis grade 3 osteoarthritis or conversion to total hip arthroplasty. Predictors of failure in patients aged ≥ 50 years were examined using Cox regression. Results: In patients aged ≥ 50 years, the median mHHS improved from 62 (IQR 54 to 75) to 92 (IQR 84 to 96) (p < 0.001), with scores comparable with those in patients aged < 50 years (p = 0.685). Failure occurred in seven (5.3%) and ten hips (7.6%), respectively (p = 0.607), with similar ten- and 20-year joint survival (98% (95% CI 94 to 100) and 79% (95% CI 55 to 91) vs 97% (95% CI 89 to 99) and 72% (95% CI 51 to 86); p = 0.655). PROMs did not differ significantly between groups. When compared with patients aged < 45 years, patients aged ≥ 50 years had a lower median Hip disability and Osteoarthritis Outcome Score sport/recreation score (75 (IQR 56 to 81) vs 81 (IQR 63 to 94); p = 0.044) and more complications (12 (9.2%) vs 2 (1.5%); p = 0.013). Preoperative Tönnis grade 2 independently predicted failure (hazard ratio 8.67 (95% CI 1.36 to 55.34); p = 0.022). Conclusion: TOA achieved long-term joint survival comparable with that in younger patients, supporting TOA as a joint-preserving option in this age group. However, the sport/recreation score was lower and complications more frequent than in patients aged < 45 years. Preoperative Tönnis grade 2 predicted failure, indicating that joint degeneration, rather than age alone, should guide patient selection.