Abstract
BACKGROUND: Surgeons increasingly recognize the importance of patient-specific considerations in determining ideal cup alignments. In addition, various surgical navigation systems have been reported to improve cup placement accuracy during total hip arthroplasty (THA). Recently, a novel computed tomography (CT)-based planning and mixed-reality (MR) guidance system was developed to enable patient-specific 3-dimensional planning of the ideal cup position and further improve intraoperative achievement of the planned orientation. METHODS: This is retrospective, observational study of 40 patients (40 hips) who underwent MR-guided THA. Patient-specific CT-based surgical planning with definition of target operative anteversion and inclination of the acetabular cup in relation to the anterior pelvic plane was performed. 3D holograms of the cup and cup impactor in the selected target position were created and exported. Intraoperatively, automatic holographic registration was performed using a smart tool-based linked-paired-point matching method. Patient-specific content was displayed on a head-mounted display, and the acetabular component was inserted by matching the spatial position of the cup impactor with the hologram of the cup impactor in the target position. Postoperatively, patients underwent biplane simultaneous imaging for measurement of achieved cup alignment using a validated measurement method. RESULTS: Mean planned operative anteversion and inclination angles were 28.4° ± 1.6° (95% confidence interval [CI], 27.9°-28.8°) and 39.9° ± 0.3° (95% CI, 39.8°-40.0°), respectively. The mean absolute target error between preoperative target operative anteversion and the achieved operative anteversion was 0.7° ± 1.1° (95% CI, 0.3°-1.0°; range, 0°-4°). The mean absolute target error between preoperative target operative inclination and the achieved operative inclination was 1.1° ± 1.2° (95% CI, 0.7°-1.4°; range, 0°-4°). CONCLUSION: Acetabular component positioning using a mixed reality guidance system during THA was highly accurate and well within the accuracy reported for other navigation systems. LEVEL OF EVIDENCE: Level III. See Instructions for Authors for a complete description of levels of evidence.