International Orthopaedics - 2026-07-27 - Journal Article
Residual acetabular roof obliquity is associated with long-term joint preservation after transposition osteotomy of the acetabulum.
Miyata T, Kitamura K, Fujii M, Motomura G, Hamai S, Kawahara S, Yamaguchi R, Utsunomiya T, Yoshino S, Nakashima Y
Topics
Key Takeaway
Each 1-degree increase in residual post-operative acetabular roof obliquity after transposition osteotomy of the acetabulum was associated with a 10% increase in THA conversion risk (HR 1.10, 95% CI 1.03–1.18), with a data-derived 6.1-degree threshold separating 20-year survival of 92.4% vs 45.7%.
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Summary
This retrospective study evaluated whether residual acetabular roof obliquity after transposition osteotomy of the acetabulum (TOA) predicts THA conversion in 52 hips with Tönnis grade 0–1 OA at baseline. Univariable Cox regression demonstrated HR 1.10 per degree of residual obliquity (p=0.005), and Kaplan-Meier analysis showed overall joint survival of 98.1% at 10 years and 78.5% at 20 years. A data-derived 6.1-degree obliquity threshold showed moderate ROC discrimination (AUC 0.73) and separated 20-year survival dramatically, but was not externally validated.
Key Limitation
Only 11 THA conversion events preclude multivariable Cox regression, meaning confounders such as pre-operative lateral center-edge angle, femoral head coverage, and patient age at surgery are uncontrolled.
Original Abstract
PURPOSE
To evaluate whether residual post-operative acetabular roof obliquity is associated with long-term joint preservation after transposition osteotomy of the acetabulum for hip dysplasia.
METHODS
This retrospective study included 52 hips with pre-operative Tönnis grade 0 or 1 osteoarthritis and complete electronic radiographic datasets after transposition osteotomy of the acetabulum performed between 1996 and 2005. Conversion to total hip arthroplasty was the primary endpoint. Because only 11 conversions occurred, associations were evaluated using Kaplan-Meier analysis and univariable Cox regression. A 20-year receiver operating characteristic analysis and secondary analyses using a composite structural-failure endpoint and available patient-reported outcomes were exploratory.
RESULTS
Eleven hips underwent total hip arthroplasty. Overall joint survival was 98.1% at ten years and 78.5% at 20 years. Higher post-operative acetabular roof obliquity was associated with conversion in univariable Cox regression (hazard ratio 1.10 per degree, 95% confidence interval 1.03 to 1.18; p = 0.005). The 20-year receiver operating characteristic analysis included 38 hips and showed moderate discrimination (area under the curve 0.73, 95% confidence interval 0.48 to 0.94). The internally derived 6.1-degree threshold separated 20-year survival (92.4% versus 45.7%; log-rank p < 0.001), but was not externally validated.
CONCLUSION
In this selected transposition osteotomy cohort, residual post-operative acetabular roof obliquity showed an unadjusted association with long-term total hip arthroplasty conversion. The data-derived threshold should be regarded as exploratory and requires external validation.