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Purpose: Clinical 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. Methods: This 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. Results: The 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). Conclusion: Our 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.

Background: Total hip arthroplasty (THA) is a challenging surgical procedure that can be used to treat severely dislocated hips. There are few reports regarding cemented THAs involving subtrochanteric shortening osteotomy (SSO), even though cemented THAs provide great advantages because the femur is generally hypoplastic with a narrow, deformed canal. Purposes: We evaluated the utility of cemented THA with SSO for Crowe group IV hips, and assessed the relationship between leg lengthening and nerve injury. Our goal was to describe surgical techniques for optimizing surgical outcomes while minimizing the risk of nerve injury. Methods: We retrospectively reviewed 34 cases of cemented THAs with transverse SSO for Crowe group IV. Prior to surgery, mean hip flexion was 93.1° (40°–130°). The mean follow-up period was 5.2 years (3–10 years). Results: Bone union took an average of 7.7 months (3–24 months). Mean leg lengthening was 40.5 mm (15–70 mm) and was greater in patients without hip flexion contracture. None of the patients experienced any nerve injuries associated with leg lengthening, and radiographic evidence of loosening was not observed at the final follow-up. Conclusions: SSO combined with cemented THA is an effective treatment for severely dislocated hips. Leg lengthening is not necessarily associated with nerve injuries, and the likelihood of this surgical complication may be related to the presence of hip flexion contracture. [ABSTRACT FROM AUTHOR]