This study evaluated the accuracy of intraoperative leg length and femoral anteversion measurements obtained during total hip arthroplasty (THA) using the Mako robotic system with enhanced mode.

A total of 55 hips in four men and 51 women who underwent primary THA with the Mako system via an anterolateral approach were retrospectively evaluated. Intraoperative measurements of leg length and femoral anteversion displayed by the Mako enhanced mode were compared with postoperative CT-based measurements. Absolute errors and their distributions were calculated to assess the accuracy of intraoperative assessments.

The mean absolute error was 2.3 ± 1.8 mm for postoperative leg length discrepancy and 2.9 ± 2.2° for stem anteversion. Of the 55 hips, 46 (83.6%) showed leg length errors within 3 mm and 51 (92.7%) within 5 mm. For stem anteversion, 48 hips (87.3%) were within 3° and all 55 hips (100%) were within 5°. Mako enhanced mode could not be completed in 10.7% of cases because of femoral array loosening or screw penetration into the medullary canal.

Mako enhanced mode demonstrated clinically acceptable accuracy for intraoperative measurement of leg length and femoral anteversion, contributing to precise femoral stem implantation in robotic-assisted THA.