A novel imageless accelerometer-based navigation system improves acetabular cup placement accuracy during total hip arthroplasty in the lateral decubitus position

Introduction The accuracy of acetabular cup placement using conventional portable imageless navigation systems in total hip arthroplasty (THA) in the lateral decubitus position remains challenging. Several novel portable imageless navigation systems have been developed recently to improve cup placement accuracy in THA. This study compared the accuracy of acetabular cup placement using a conventional accelerometer-based portable navigation (c-APN) system and a novel accelerometer-based portable navigation (n-APN) system during THA in the lateral decubitus position. Materials and methods This retrospective cohort study compared 45 THAs using the c-APN and 45 THAs using the n-APN system. The primary outcomes were the absolute errors between the intraoperative and postoperative values of acetabular cup radiographic inclination and anteversion angles and the percentage of cases with absolute errors within 5 degrees. Intraoperative values were shown on navigation systems, and postoperative measurements were conducted using computed tomography images. Results The median absolute errors of the cup inclination angles were significantly smaller in the n-APN group than in the c-APN group (3.9 degrees [interquartile range 2.2 degrees-6.0 degrees] versus 2.2 degrees [interquartile range 1.0 degrees-3.3 degrees]; P = 0.002). Additionally, the median absolute errors of the cup anteversion angles were significantly smaller in the n-APN group than in the c-APN group (4.4 degrees [interquartile range 2.4 degrees-6.5 degrees] versus 1.9 degrees [interquartile range 0.8 degrees-2.7 degrees]; P < 0.001). Significant differences were observed in the percentage of cases with absolute errors within 5 degrees of inclination (c-APN group 67% versus n-APN group 84%; P = 0.049) and anteversion angles (c-APN group 62% versus n-APN group 91%; P = 0.001). Conclusions The n-APN system improved the accuracy of the cup placement compared to the c-APN system for THA in the lateral decubitus position.