Identification of risk factors for treatment failure of closed reduction and abduction bracing after first-time total hip arthroplasty dislocation

INTRODUCTION: After a first-time total hip arthroplasty (THA) dislocation, a closed reduction followed by partial immobilization in an abduction brace is the recommended therapy. Despite modern abduction braces the success rate of conservative therapy is limited and evidence is scarce. The aim of this study was to identify risk factors for failure of conservative treatment after THA dislocation. MATERIAL AND METHODS: Eighty-seven patients, with conservative treatment of a first-time dislocation of a primary or revision THA, were included in this retrospective cohort study. Success was defined as a stable THA for a minimum of 6 months. Re-dislocation, open reduction or revision was defined as failure. The following risk factors were analyzed: gender, age, body mass index (BMI), ASA (American Society of Anesthesiologists) score, time of dislocation, head size, cup orientation, leg length, center of rotation and offset. RESULTS: Sixty-seven percent of all patients experienced a re-dislocation, despite standardized conservative therapy. A BMI ≥ 25 kg/m(2), early THA dislocation, and low cup anteversion were associated with a statistically significantly higher risk for re-dislocation. None of the other risk-factors achieved statistical significance. A multifactorial risk-factor analysis was performed to assess whether a cup position outside of Lewinnek’s safe zone in combination with gender, BMI and time to dislocation showed statistical significance for re-dislocation. Both BMI ≥ 25 kg/m(2) and early dislocation showed a statistically higher failure rate. Cup position and gender were not significant. CONCLUSIONS: BMI ≥ 25 kg/m(2), early THA dislocation and low cup anteversion were identified as significant risk factors for failure of conservative treatment with an abduction brace for first-time THA dislocation.