Robotic arm-assisted total hip arthroplasty via a minimally invasive anterolateral approach in the supine position improves the precision of cup placement in patients with developmental dysplasia of the hip

Background: This study evaluated the accuracy of the cup alignment angles and spatial cup positioning on computed tomography (CT) images in patients with osteoarthritis secondary to developmental dysplasia of the hip (DDH) who underwent total hip arthroplasty (THA) using a minimally invasive technique via an anterolateral approach in the supine position according to whether a robotic armassisted system or a CT-based navigation system was used. Methods: We reviewed 60 robotic arm-assisted (RA)-THA cases and 174 navigation-assisted (NA)-THA cases. After propensity score matching, there were 52 hips in each group. Postoperative cup alignment angles and position were assessed by superimposition of a three-dimensional cup template onto the actual implanted cup using postoperative CT images with pelvic coordinates matching the preoperative planning. Results: The mean absolute error of the inclination angle and the anteversion angle between the preoperative planning and the postoperative measurement was significantly smaller in the RA-THA group (inclination, 1.1 degrees +/- 0.9; anteversion, 1.3 degrees +/- 1.0) than in the NA-THA group (inclination, 2.2 degrees +/- 1.5; anteversion, 3.3 degrees +/- 2.5). For acetabular cup positioning, the mean discrepancy between the preoperative planning and the postoperative measurement was 1.3 +/- 1.3 mm on the transverse axis, 2.0 +/- 2.0 mm on the longitudinal axis, and 1.3 +/- 1.7 mm on the sagittal axis in the RA-THA group and 1.6 +/- 1.4 mm, 2.6 +/- 2.3 mm, and 1.8 +/- 1.3 mm, respectively, in the NA-THA group. High precision of cup positioning was observed in both groups with no statistically significant difference. Conclusion: Robotic arm-assisted THA using a minimally invasive technique via an anterolateral approach in the supine position allows accurate cup placement in patients with DDH. (c) 2023 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved.