Abstract
PURPOSE: Several studies have reported a risk of dislocation in obese patients after total hip arthroplasty. In this study, we evaluated the interaction between obesity and dislocation by kinematic analysis using a navigation system. METHODS: The intraoperative range of motion (ROM) and postoperative impingement-free ROM were measured in 38 patients, and we compared the impingement-free ROM in obese and non obese patients. RESULTS: The postoperatively simulated ROM was similar in the obese and non obese groups. The intraoperative ROM was smaller in the obese group. The difference values between the intraoperative ROM and postoperatively simulated ROM were larger in the obese group. These results indicate that obese patients have less ROM following primary total hip arthroplasty even when the implant positioning is performed correctly. CONCLUSIONS: Dislocations are multifactorial problems including soft tissue impingement. Therefore, the risk of dislocation caused by soft tissue impingement in obese patients may be increased.