Fluoroscopically Guided Acetabular Component Positioning: Does it Reduce the Risk of Malpositioning in Obese Patients?

Abstract Background Obesity has been described as an independent risk factor for acetabular component malpositioning. The purpose of this study was to determine if the reported risk of acetabular component malpositioning in obese patients could be overcome by use of fluoroscopic navigation in total hip arthroplasty. Methods The first postoperative standing anteroposterior (AP) pelvis radiographs from 1599 consecutive patients who underwent fluoroscopic-guided total hip replacements via anterior approach between March 1, 2010 and March 1, 2016 were obtained. We retrospectively reviewed this prospectively collected data. Inclination and anteversion were measured as described by Barrack et al. Intraoperative target ranges for inclination and anteversion angles were 30˚–50˚ and 5˚–25˚, respectively, as based on recreation of each patient's unique functional pelvic tilt determined on a standing pre-operative AP pelvis radiograph. Patients were divided into three cohorts based on BMI, non-obese ( 40), looking for significant differences in acetabular components positioned outside of Lewinnek's safe zone between the cohorts. Univariate comparisons were evaluated using Pearson's chi-squared test. Differences in outcomes were considered significant at p≤0.05. Results Of the 1599 patients, 1065 were non-obese, 506 obese, and 28 morbidly obese. Overall, average inclination was 37.7˚ and anteversion 16.3˚. Regarding inclination, 95.0% of cups were positioned in the safe zone, 95.7% for anteversion, and 91.2% for both inclination and anteversion. Analysis of each group individually revealed an average inclination of 37.5˚ in the non-obese patients, 37.9˚ in the obese patients and 39.9˚ in the morbidly obese patients. For anteversion, each group's averages were 16.1˚, 16.5˚ and 16.0˚, respectively. There was no significant relationship between a patient's BMI and cup position for inclination (p = 0.867), anteversion (p = 0.673), or both inclination and anteversion (p = 0.624). Conclusion Fluoroscopy is a useful tool for achieving a targeted acetabular component orientation in DA THA. Contrary to prior reports without use of fluoroscopy, there was no trend towards decreased accuracy in positioning acetabular components in obese patients when performing fluoroscopic-guided DA THA.