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

A Clavé, V Sauleau, D Cheval, T Williams, C Lefèvre, E Stindel
Orthopaedics & Traumatology, Surgery & Research: OTSR 2015, 101 (7): 791-5

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 = P0) 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.

LEVEL OF EVIDENCE: IV - retrospective study.

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