Robotic Arm–Assisted System Improved Accuracy of Cup Position and Orientation in Cementless Total Hip Arthroplasty for Dysplastic Hips: A Comparison Among Groups With Manual Placement, Computed Tomography–Based Navigation, and Robotic Surgery

Abstract

Accurate cup placement in total hip arthroplasty (THA) for patients with dysplasia is challenging due to the distinctive bone deformities. This study aimed to compare the accuracy of cup placement position and orientation across robotic arm–assisted systems (R-THA), computed tomography–based navigation (N-THA), and manual procedure (M-THA) in THA for osteoarthritis secondary to dysplasia. A total of 167 patients (197 hips), including 88 R-THAs, 45 N-THAs, and 46 M-THAs, were analyzed. Propensity score matching was performed to align the patient backgrounds. Horizontal and vertical centers of rotation were measured for cup position, whereas radiographic inclination and anteversion were measured for cup orientation. The proportion of cases with cup placement within 3 mm and 5° from the target was compared. R-THA had a significantly higher percentage of cup placement within 3 mm of the target compared to N-THA (78% vs 49%; P = .0041) and M-THA (78% vs 53%; P = .013). Similarly, R-THA was significantly more successful in placing the cup within 5° of the target compared to N-THA (84% vs 58%; P = .0049) and M-THA (91% vs 20%; P < .0001). Moreover, N-THA was significantly better at placing the cup within 5° of the target compared to M-THA (62% vs 14%; P < .0001), whereas there was no significant difference in the percentage of cup placement within 3 mm of the target (51% vs 51%; P = 1.0). Robotic arm–assisted system and computed tomography–based navigation improved accuracy in cup orientation compared to the manual procedure. Additionally, the robotic arm–assisted system further improved cup position accuracy.