COMPARING ACETABULAR COMPONENT POSITION IN DIRECT ANTERIOR APPROACH TOTAL HIP ARTHROPLASTY USING FLUOROSCOPY VERSUS IMAGELESS NAVIGATION

Intraoperative fluoroscopy is commonly used in direct anterior approach (DAA) total hip arthroplasty (THA) to improve component positioning and minimize leg length discrepancy (LLD). However, imageless optical navigation systems have been shown to reduce the frequency of positional outliers in acetabular cup position in lateral and posterior approach THA. The aim of this study was to compare the accuracy and precision of fluoroscopy to that of an imageless optical navigation system in DAA THA. A retrospective cohort study was conducted on 640 primary DAA THAs performed with intraoperative fluoroscopy (n=300 patients) or imageless optical navigation (n=304 patients). Accuracy was compared between fluoroscopy and navigation by measuring acetabular cup inclination, anteversion, and LLD. The proportion of components placed within the Lewinnek safe zone was evaluated, as well as those placed within a more precise target range of ± 5° from the surgical target (40° ± 5° inclination, 20° ± 5° anteversion). There was a difference between fluoroscopy and navigation THA in mean acetabular inclination (40.4° SD: 4.7° vs. 42.0° SD: 3.74° respectively, p < 0 .001) and anteversion (17.9° SD: 4.7° vs. 20.3° SD: 3.6° respectively, p < 0 .001). There was no significant difference in the percentage of components positioned within the Lewinnek safe zone (90.3% vs 88.8% respectively, p=0.519). When using the more precise targets, navigation increased the proportion of acetabular components positioned correctly (fluoroscopy: 50.3% vs navigation: 65.6%, p < 0 .01). Mean LLD was higher with use of fluoroscopy compared to navigation (5.5 mm SD: 4.1 mm vs. 4.6 mm SD: 3.4 mm respectively, p < 0 .001). Both fluoroscopy and imageless optical navigation result in accurate component positioning for DAA THA. Navigation was more precise and associated with improved acetabular anteversion placement and restoration of LLD. Navigation is an accurate alternative to fluoroscopy while also reducing radiation exposure to the patient and operating team.