Low dislocation rates with the use of patient specific "Safe zones" in total hip arthroplasty.

Overview

INTRODUCTION: The purpose of this study was to compare patient-specific acetabular cup target orientation using functional simulation to the Lewinnek Safe Zone (LSZ) and determine associated rates of postoperative dislocation. METHODS: A retrospective review of 1500 consecutive primary THAs was performed. Inclination, anteversion, pelvic tilt, pelvic incidence, lumbar flexion, and dislocation rates were recorded. RESULTS: 56% of dynamically planned cups were within LSZ (p < 0.05). 6/1500 (0.4%) of these cups dislocated at two year follow-up, and all were within LSZ. CONCLUSION: Optimal acetabular cup positioning using dynamic imaging differs significantly from historical target parameters but results in low rates of dislocation. LEVEL OF EVIDENCE: Level III: Retrospective.