Mid-term Outcomes and Factors Associated with Recovery after Total Hip Arthroplasty with Transverse Subtrochanteric Shortening Osteotomy for Crowe Type IV Developmental Dysplasia of the Hip

Background: This study assessed mid-term outcomes after total hip arthroplasty (THA) with transverse subtrochanteric shortening osteotomy for Crowe type IV developmental dysplasia of the hip (DDH), and factors associated with functional recovery. Methods: We retrospectively reviewed 46 patients (53 hips) treated between 2014 and 2023. Mean age was 50.3 years and mean follow-up was 6.2 years. Clinical outcomes included Harris Hip Score (HHS), pain score, leg-length discrepancy (LLD), walking independence, abductor lurch, complications and revision. Radiographic outcomes included femoral offset, acetabular offset, cup inclination, cup anteversion and cup size. Kaplan-Meier analysis estimated implant survival. Correlation and multivariable linear regression assessed predictors of postoperative HHS. Results: HHS improved from 30.9 to 89.9, pain score from 4.7 to 1.4, and median LLD from 52.0 mm to 5.4 mm. Independent ambulation increased from 78.3% to 97.8%, and abductor lurch decreased from 69.6% to 10.9%. Acetabular offset decreased, femoral offset was maintained, and mean cup inclination and anteversion were 44.8 degrees and 14.6 degrees. Six revisions occurred, with 87.0% implant survival at 5 and 10 years. Cup inclination correlated negatively with postoperative HHS (r = -0.418, P = 0.002) and remained inversely associated with HHS after patient-level cluster-robust adjustment (β = -0.359 per degree, cluster-robust SE = 0.094, 95% CI, -0.549 to -0.169; P = 0.0004). Cup size was also inversely associated with postoperative HHS in the primary clustered model (β = -0.641 per mm, cluster-robust SE = 0.290, 95% CI, -1.225 to -0.057; P = 0.032). Cup inclination moderately discriminated suboptimal recovery (HHS < 80; AUC = 0.758), whereas residual LLD did not (AUC = 0.524). Conclusion: THA with transverse subtrochanteric shortening osteotomy provided substantial functional improvement, pain relief, limb-length correction and acceptable mid-term implant survival in Crowe type IV DDH. After patient-level clustering was accounted for, greater cup inclination remained inversely associated with lower postoperative HHS in this retrospective cohort, suggesting that careful attention to cup inclination may be warranted in complex dysplastic hip reconstruction. These findings are exploratory and should be validated in larger patient-level datasets. Level of Evidence Level III, retrospective cohort study