A Prospective, Randomized Study of Surgical Positioning Software Shows Improved Cup Placement in Total Hip Arthroplasty

200 patients scheduled for direct anterior total hip arthroplasty were randomized to surgery with or without the use of computer assistance software (CAS group) for alignment of the acetabular cup. Target inclination angle was 40 degrees and target anteversion angle was 20 degrees. Radiographs obtained at 4 weeks postoperatively were used to measure alignment of the acetabular cup. For inclination, a significant difference in favour of the CAS group was observed in mean angle and mean error from 40 degrees, though the rate of outliers deviating >10deg from target alignment was 0% and 2% in the groups, respectively. For anteversion, no significant difference between groups was observed in mean angle or mean error from 20 degrees, and the rate of outliers deviation >10deg from target alignment was 1% in both group.