Three-Dimensional Pelvic Kinematics During Direct Anterior Approach Total Hip Arthroplasty on an Orthopaedic Table.

Background: Intraoperative pelvic positioning plays an important role in component placement during total hip arthroplasty (THA), affecting range of motion, stability, and dislocation risk. The objective of this study was to evaluate three-dimensional pelvic kinematics during several key surgical steps of direct anterior approach (DAA) THA facilitated by a Hana table. Methods: DAA THA was performed on 10 hips from 5 cadaveric specimens. Pelvis and table movement were recorded throughout the procedure using motion capture arrays. Bony anatomy was registered to computed tomography-based segmentations to establish meaningful kinematic data. Pelvic flexion, lateral tilt (LT), and axial rotation (AR) were reported relative to the Hana table. Results: The pelvis was oriented anteriorly in the initial supine position, with minimal LT (median: 0.1°, range: -5.7° to 5.0°) and AR (median: -1.3°, range: -3.6° to 3.6°). Minimal pelvic flexion was observed across all surgical steps of the procedure, while higher magnitudes of LT and AR were exhibited. Lateral tilt and AR generally occurred toward the operative hip, except for AR away from the operative hip during acetabular reaming. Conclusions: These measurements suggest it may be necessary for surgeons to consider intraoperative pelvic tilt during cup positioning. This study offers a comprehensive set of pelvic kinematics throughout DAA THA, offering valuable insights for surgical decision-making and enhancing component positioning.