Risk Factor Analysis of Delayed Union or Nonunion After Total Hip Arthroplasty Combined with Subtrochanteric Transverse Osteotomy in Patients Who have Crowe Type IV Developmental Dysplasia of the Hip.

BACKGROUND: Total hip arthroplasty (THA) combined with subtrochanteric transverse osteotomy (STO) is a standard surgical approach for the treatment of Crowe IV developmental dysplasia of the hip (DDH). However, delayed union or nonunion at the osteotomy site remains a major complication, impeding postoperative functional rehabilitation and compromising patient outcomes. Identifying the risk factors associated with this complication is crucial for refining surgical techniques.

METHODS: A retrospective study was conducted on 107 patients (130 hips) who had Crowe IV DDH and underwent cementless THA combined with STO at our institution from January 1, 2019 to June 30, 2024. Multiple radiographic parameters were measured, including osteotomy length, the distance from the base of the lesser trochanter to the osteotomy line, the distance from the osteotomy line to the distal tip of the femoral stem, medial-lateral canal fill ratio, anterio-posterior canal fill ratio, medial-lateral cortical apposition ratio, and anterio-posterior cortical apposition ratio. These parameters were compared between patients who have uneventful unions and those who have delayed union/nonunion. Subgroup analyses were performed to identify risk factors specific to different fixation methods.

RESULTS: Of the 130 hips, 104 were stabilized with autogenous bone plate wiring, while 26 relied solely on femoral stem press-fit fixation. Delayed union or nonunion occurred in 19.2% (26 hips) of cases, including 25 hips with delayed union and one hip with nonunion. The incidence of delayed union in the autogenous bone plate wiring group (13.8%) was significantly lower than that in the stem press-fit only group (36.1%, P = 0.004). The delayed/nonunion group exhibited significantly lower medial-lateral canal fill ratios and anterior-posterior cortical apposition ratios (P < 0.05). In the press-fit-only group, advanced age, inadequate canal filling, and poor cortical apposition were identified as risk factors. In contrast, only a low antero-posterior cortical apposition ratio was found to adversely affect healing in the bone plate wiring group (P = 0.003).

CONCLUSIONS: Autogenous bone plate wiring effectively improves the osteotomy union rate following THA combined with STO in patients who have Crowe IV DDH and can mitigate the adverse effects of advanced age and inadequate canal filling. Low medial-lateral canal fill ratio and poor antero-posterior cortical apposition are independent risk factors for osteotomy delayed union or nonunion.