Association between stem bypass and union failure of subtrochanteric shortening osteotomy in total hip arthroplasty for high hip dislocations

Abstract

PurposeClinical evidence of risk factors for union failure at osteotomy sites after total hip arthroplasty (THA) using subtrochanteric shortening osteotomy (SSO) in patients with high hip dislocations is limited because of the rarity of this dislocation type. The aim of this study was to identify the factors influencing bone union at osteotomy sites in patients with high hip dislocations undergoing this procedure. MethodsThis retrospective, case-control study included a total of 28 hips of 24 patients with high hip dislocations who had undergone THA using SSO at a single institution from 1993 to 2018. Fourteen hips were categorized into the union-failure group at 6 months after surgery and compared with a control group including the other 14 hips. We compared various demographic, clinical, and radiological characteristics between the two groups, including age, sex, body mass index, cement usage of stem, stem bypass characteristics, clinical evaluations, and implant survival. ResultsThe union-failure group had inferior results for clinical evaluations and implant survival. Multivariable analysis found that the stem bypass ratio was significantly shorter in the union-failure group than in the control group (48 vs 64%; odds ratio, 1.18; 95% confidence interval, 1.02 to 1.38; p ​= ​.028). ConclusionOur results demonstrated that shorter stem bypasses were related to union failure at osteotomy sites in patients with high hip dislocations who underwent THA using SSO. We recommend that the femoral stem be inserted more than 50% of the stem length below the osteotomy site, especially for cemented THA.