Does accelerometer-based portable navigation provide more accurate and precise cup orientation without prosthetic impingement than conventional total hip arthroplasty? A randomized controlled study.

Purpose: This prospective randomized controlled study examined whether accelerometer-based navigation resulted in more accurate or precise cup orientation than a conventional mechanical guide. We used a simulation to evaluate how cup orientation affected potential hip range of motion (RoM) and freedom from prosthetic impingement.

Methods: Sixty hips were randomly allocated 1:1 to accelerometer-based portable navigation or conventional guidance. Procedures were performed through a standard posterolateral approach and combined anteversion technique. Cup inclination, cup anteversion, and stem anteversion were measured using computed tomography (CT). Using CT-based simulation, we evaluated impingement-free potential RoM and the proportion of hips with potential RoM required for daily activities.

Results: Absolute cup inclination and anteversion error averaged 4.3° ± 3.2° and 4.4° ± 2.9° for the navigation cohort and 5.6° ± 3.7° and 5.7° ± 4.2° for the conventional cohort, with no significant differences. Navigation resulted in significantly less variation in anteversion error than the conventional guide (p = .0049). Flexion, internal rotation (IR) at 90° of flexion, extension, and external rotation (ER) averaged 123° ± 12°, 46° ± 13°, 50° ± 10°, and 73° ± 23°, respectively, in the navigation cohort and 127° ± 10°, 52° ± 14°, 45° ± 10°, and 63° ± 12°, respectively, in the conventional cohort (p = .15, .15, .03, and .03, respectively). Flexion > 110°, IR > 30° at 90° of flexion, extension > 30°, and ER > 30° were achieved by 93%, 90%, 100%, and 100% of hips, respectively, in the navigation cohort and 97%, 93%, 97%, and 100% of hips, respectively, in the conventional cohort, with no significant differences.

Conclusions: Cup anteversion with the navigation system was more precise, but not more accurate, than with the conventional guide. The navigation cohort exhibited greater potential extension and ER than the conventional cohort, but no significant difference in impingement within the potential RoM required for daily activities.

Trial Registration Number: 29036. Date of registration: November 14, 2017.