Errors in femoral anteversion, femoral offset, and vertical offset following robot-assisted total hip arthroplasty

The objectives were to determine errors in femoral anteversion (FA), femoral offset (FO), and vertical offset (VO) with robot-assisted total hip arthroplasty (THA) and how consistently these errors are within clinically desirable limits of +/- 5 degrees and +/- 5 mm. After preoperative planning, robot-assisted THAs were performed on twelve cadaveric specimens. The error between achieved and planned component placements was used to determine bias (mean error) and precision (SD of error). The percent of the population within clinically desirable limits was determined. Bias of 1.5 degrees and 2.7 mm occurred for FA and VO, respectively. Precision was 1.2 degrees for FA and better than 1.5 mm for FO and VO. The percent of population within clinically desirable limits was at least 95% for FA and at least 99% for FO. With limits of +/- 7 mm, at least 95% of the population was within these limits for VO. Robot-assisted THA may improve clinical outcomes.