Total Hip Arthroplasty Combined With Subtrochanteric Transverse Shortening Osteotomy: Factors Associated With Delayed Union at the Osteotomy Site

Background: Total hip arthroplasty (THA) with subtrochanteric shortening osteotomy for Crowe type IV hips poses the risk of nonunion at the osteotomy site. The aim of this study was to analyze the factors that affect the bone union rate at the osteotomy site. Methods: We retrospectively reviewed a consecutive series of 27 THAs with subtrochanteric transverse shortening osteotomy performed for Crowe type IV hips. The effects of patient-related and surgery-related factors on the risk of delayed union were analyzed using univariate and multivariate regression analyses. Results: The mean follow-up period was 10.0 (1.4 to 19.1) years. The implant survival rate was 87.8% (95% confidence interval: 60.2% to 97.2%) at 10 years. The length of femoral bone resection was the only factor associated with the risk of delayed union. Longer bone resection lengths were significantly correlated with the reduced risk of delayed union (odds ratio: 0.63 [0.030 to 0.90],P= 0.0013). Other variables, including the use of a cement stem (P= 0.34) and the presence of a gap >1 mm at the osteotomy site (P= 0.98), were not associated with the risk of delayed union. Discussion: THA with subtrochanteric transverse osteotomy provides satisfactory long-term results for Crowe type IV hips. For shorter required femoral resection lengths, the risk of delayed union was higher. A longer resection could permit fabrication of longer autologous longitudinal bone struts and likely contributes to enhanced stability at the osteotomy site.