Can computer-assisted surgery help restore leg length and offset during THA? A continuous series of 321 cases

Introduction: Total hip arthroplasty (THA) can bring about complications - particularly leg length differences - that are becoming increasingly litigious. Computer-assisted orthopedic surgery (CAOS) can help optimize the procedure, but its ability to effectively restore leg length is controversial. As a consequence, we carried out a study to determine: (1) its contribution to meeting leg length and offset objectives, (2) its reliability, by evaluating the correlation between radiological and navigation data, (3) its safety, by evaluating navigation-specific and non-specific complications. Hypothesis: CAOS will help to restore leg length within +/- 5 mm in more than 80% of cases. Material and methods: A series of 321 continuous cases of cementless THA implanted through the posterolateral approach using CAOS was analyzed retrospectively. With a minimum 1 year follow-up, we evaluated whether the leg length and offset goals were achieved, how well the navigation and radiology data were correlated and whether navigation-specific and non-specific complications occurred. Based on our hypothesis that 80% of patients would have less than 5 mm leg length difference and the null hypothesis (PA = PO) with an alpha of 0.05, 200 observations were required to achieve a power of 90%. Results: The leg length and offset objectives were achieved in 83.3% and 88% of cases, respectively. Twenty-two patients required a heel wedge to compensate for leg length differences. The correlation between the radiology and surgical navigation data was satisfactory - the Pearson coefficient was 0.79 for length and 0.74 for offset. Intraoperative and postoperative complications or adverse events were found in 14.6% of cases; these were specific to CAOS in 12.1% of cases and non-specific in 2.5% of cases. Conclusion: This study shows the relevance of CAOS for achieving preoperative leg length objectives, with good correlation between navigation and radiology data, and without major complications. (C) 2015 Elsevier Masson SAS. All rights reserved.