How Much Does a Computed Tomography-Based Mixed-Reality Navigation System Change Freehand Acetabular Component Position?

Background: This study evaluates how a computed tomography-based mixed-reality (MR) navigation system impacts acetabular component orientation compared to freehand positioning in total hip arthroplasty. Methods: A series of 79 patients who underwent total hip arthroplasty utilizing a computed tomography-based MR navigation system were reviewed. The surgeon initially placed the acetabular cup freehand, attempting to achieve the preoperative plan, and this initial intraoperative orientation was recorded. The cup was then adjusted to the planned position. The difference between freehand and planned tilt-adjusted operative anteversion (OA) and inclination (OI) determined the navigation tool's impact. Results: The mean preoperative planned OA was 30.1 +/- 2.0 (range: 25, 35) degrees, and the mean freehand intraoperative OA was 30.2 +/- 9.1 (range: 4, 57) degrees (P 1/4 .885), requiring a mean adjustment of 6.8 +/- 5.1 (range: 0,23) degrees. Freehand OA was corrected at least 5 degrees in 54.4% (43/79) of cases. The mean preoperative planned OI was 40.8 +/- 0.6 (range: 39, 42) degrees, and the mean freehand intraoperative OI was 37.8 +/- 6.6 (range: 18, 53) degrees (P < .001), requiring a mean adjustment of 5.7 +/- 4.5 (range: 0, 22) degrees to achieve. Freehand OI was corrected at least 5 degrees in 43.0% (34/79) of cases. Conclusions: Freehand acetabular component positioning in the lateral position is variable when attempting to execute patient-specific numerical cup orientation targets. Use of this navigation tool led the surgeon to correct more than 5 degrees in both OA and OIin roughly half of the hips. (c) 2025 The Authors. Published by Elsevier Inc. on behalf of The American Association of Hip and Knee Surgeons. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).