Imageless navigation system (Naviswiss) provides accurate component position in total hip arthroplasty with lateral decubitus position for end-stage hip osteoarthritis: A prospective cohort study with CT-validation

Aims The Naviswiss system (Naviswiss AG, Brugg, Switzerland) is a handheld imageless navigation device used to improve the accuracy of implant positioning in total hip arthroplasty (THA). However, clinical data for leg length discrepancy and femoral offset is lacking, and the validity of the system has not been reported for patients undergoing THA in the lateral decubitus position. This study aimed to report the accuracy of the device in this patient population. Methods Patients underwent THA in the lateral decubitus position by a single surgeon. Component positioning measured by the device intraoperatively was compared to postoperative measurements on computed tomography (CT) scans. Agreement between the navigation system and postoperative measurements was reported with respect to acetabular cup inclination, acetabular cup version, femoral offset and leg length discrepancy. Results The mean difference between intraoperative and postoperative CT measurements was within 2° for angular measurements and 2mm for leg length. Absolute differences for the two indices were within 5° and 4mm. Mean bias was 1-2° overestimation for cup orientation and up to 2mm overestimation for leg length change, but 95% limits of agreement did not exceed absolute thresholds of 10° and 10mm, especially after correction for bias. Four cases (12%) were declared intraoperatively for issues with fixation on the greater trochanter. While inclusion of these cases generated acceptable accuracy overall, their omission improved between-case variability in accuracy and reduced the LOA for both offset and leg length. Conclusions The accuracy of the Naviswiss system falls within clinically acceptable recommendations for acetabular cup placement, femoral offset and length length. The system could be further improved with regression-based bias correction.