Accuracy of robotic arm-assisted versus computed tomography-based navigation for cup orientation and positioning in total hip arthroplasty using the direct anterior approach in supine position

Abstract

Background A robotic arm-assisted and a computed tomography (CT)-based navigation system have been reported to improve the accuracy of component positioning in total hip arthroplasty (THA). Although some previous studies have compared robotic arm-assisted THA (rTHA) with CT-based navigated THA (nTHA), most studies evaluated the outcomes in the lateral position. No study has compared rTHA to nTHA concerning accuracy of cup placement and acetabular fractures using the direct anterior approach (DAA) in supine position. This study aimed to compare the accuracy of cup placement and the presence of intraoperative acetabular fractures between rTHA and nTHA using DAA in supine position. Methods We retrospectively investigated 209 hips of 188 patients who underwent rTHA or nTHA using DAA in supine position (rTHA using the Mako system: 85 hips of 79 patients; nTHA: 124 hips of 109 patients). After propensity score matching for age and sex, each group consisted of 73 hips. Postoperative cup orientation and positions measured using a three-dimensional templating software were compared to preoperative planning with CT measurements. Additionally, we investigated the prevalence of occult acetabular fracture. Results The mean absolute error of cup orientation was significant smaller in the rTHA group than in nTHA (inclination: 1.4° ± 1.2° vs 2.7° ± 2.2°, respectively; p = 0.0001, anteversion: 1.5° ± 1.3° vs 2.2° ± 1.7°, respectively; p = 0.007). The cases within an absolute error of 5 degrees in both RI and RA were significantly higher in the rTHA (97.3%) than in nTHA group (82.2%) (p = 0.003). The absolute error of the cup position was not significantly different between the two groups. The prevalence of occult acetabular fracture did not differ significantly between the two groups (rTHA: n = 0 [0%] vs. nTHA: n = 1 [1.4%]). Conclusion Cup placement using DAA in the supine position in rTHA was more accurate with fewer outliers compared to nTHA. Therefore, rTHA performed via DAA in a supine position would be useful for accurate cup placement.