Abstract
Introduction
The longevity of total hip arthroplasty (THA) is dependent on acetabular component position. We measured the reliability and accuracy of a CT-based navigation system to achieve the intended acetabular component position and orientation using three dimensional imaging. The purpose of the current study was to determine if the CT-guided robotic navigation system could accurately achieve the desired acetabular component position (center of rotation (COR)) and orientation (inclination and anteversion). The postoperative orientation and location of the components was determined in 20 patients undergoing THA using CT images, the gold standard for acetabular component orientation.
Methods
Twenty primary unilateral THA patients were enrolled in this IRB-approved, prospective cohort study to assess the accuracy of the robotic navigation system. Pre- and post-operative CT exams were obtained and aligned 3D segmented models were used to measure the difference in center of rotation and orientation (anteversion and inclination). Patients with pre-existing implants, posttraumatic arthritis, contralateral hip arthroplasty, septic arthritis, or previous hip fracture were excluded. All patients underwent unilateral THA using robotic arm CT-guided navigation (RIO Makoplasty; MAKO Surgical Corp).
Results
Mean age was 59.25 years (±8.65 years), 55% of patients were female (11/20). Root mean square (RMS) errors between the intended intraoperative and actual postoperative COR position was measured in the medial/lateral (M/L), superior/inferior (S/I), and anterior/posterior (A/P) directions to quantify the accuracy of the CT-based robotic navigation system. The error in COR was variable (Fig. 4). The M/L distance error was 1.29 mm (SD: 1.18 mm; range: −2.61 – 1.13 mm). The S/I distance error was 1.81 mm (SD: 1.56 mm; range: −2.19 – 3.0 mm). The A/P distance error was 1.50 mm (SD: 1.50 mm; range: −3.53 – 2.23 mm). The mean difference between the intraoperative intended anteversion and postoperative actual anteversion was 2.2° ±1.6° with an RMS error of 2.73°. The mean difference in intraoperative intended inclination and postoperative actual inclination was 3.3° ± 1.7° with an RMS error of 3.71°. The robotic navigation system was more reliable in achieving the intended anteversion than intended inclination. The ICC for anteversion was 0.92 (95% CI 0.91–0.97), compared to ICC 0.74 (95% CI 0.49–0.89) for inclination.
Conclusion
Our results suggest that CT-based navigation for THA is accurate for achieving intended cup center of rotation and both reliable and accurate in reproducing the intended cup orientation. Future research will focus on the use of a CT-based robotic navigation system to assist surgeons in the execution of a kinematic-based plan to eliminate impingement to reduce THA instability while maximizing range of motion.
