Efficacy of Computed Tomography-Based Navigation for Cup Placement in Revision Total Hip Arthroplasty

BACKGROUND: Navigation systems are an effective tool to improve the installation accuracy of the cup in primary total hip arthroplasty. This study aimed to evaluate the efficacy of a computed tomography-based navigation system in achieving optimal installation accuracy of implants in revision total hip arthroplasty and to clarify the usefulness of the navigation system. METHODS: We conducted a retrospective study of 23 hips in 23 patients who underwent revision total hip arthroplasty using a computed tomography-based navigation system; the control group comprised 33 hips in 33 patients who underwent revision total hip arthroplasty without a navigation system. RESULTS: The average cup position with the navigation system was 40.0° ± 3.7° in radiographic abduction angle, 18.8° ± 4.8° in radiographic anteversion, and 41.2° ± 8.9° in combined anteversion; without the navigation system, the average cup position was 38.7° ± 6.1°, 19.0° ± 9.1°, and 33.6° ± 20.5°, respectively. The achievement rate of cup positioning within the Lewinnek safe zone was not significantly different between the navigation group (82.6%) and control group (63.6%). In contrast, the achievement rate of cup positioning within the Widmer combined anteversion guidelines was significantly greater in the navigation group (78.3%) than in the control group (48.0%, p = 0.029). Furthermore, outlier cases in the navigation group had a smaller variance of deviation from the optimal cup position than those in the control group did. CONCLUSIONS: The results show that the use of navigation for revision total hip arthroplasty improved cup positioning and reduced the range of outliers. Improvement of cup placement accuracy influenced the installation of the stem and also improved the achievement rate of combined anteversion. Thus, a computed tomography-based navigation system is very useful for surgeons when placing the cup within the target angle in revision total hip arthroplasty.