Intraoperative Measurement Of Acetabular Component Position Using Imageless Navigation During Revision Total Hip Arthroplasty

Background: Acetabular component malposition is a major cause of dislocation following total hip arthroplasty (THA). Intellijoint HIP is an imageless navigation tool that has been shown to provide accurate intraoperative measurement of cup position during primary THA without substantially increasing operative time. However, its accuracy in revision THA has not been evaluated. This study therefore aims to assess the accuracy of Intellijoint HIP in measuring cup inclination and anteversion in comparison with computed tomography (CT) during revision THA. Methods: Intellijoint HIP was used to measure the position of the preexisting cup in 53 consecutive patients undergoing revision THA between December 2018 and February 2020. Two authors blinded to the intraoperative navigation measurements also independently measured cup position using preoperative CT according to Murray's radiographic definitions. Pearson correlation coefficients with 95% confidence intervals (CIs), paired t tests and Bland-Altman plots were used to assess agreement between navigation- and CT-measured cup position. Statistical analysis was performed using GraphPad Prism, with p values less than 0.05 indicating statistical significance. Results: There was excellent agreement between navigation and CT measurements for both cup inclination (r = 0.89, 95% CI 0.81-0.93) and anteversion (r = 0.93, 95% CI 0.88-0.96), with the mean absolute difference being 5.2o (standard deviation [SD] 4.0o) for inclination and 4.8o (SD 5.4o) for anteversion. The navigation measurement was within 10o of the radiographic measurement in 47 of 53 (88.7%) cases for inclination and 46 of 53 (86.8%) cases for anteversion. Conclusion: Imageless navigation demonstrated excellent correlation and agreement with CT measurements for both inclination and anteversion over a wide range of acetabular component positions.