Fluoroscopic Categorization of ALO in Three Sizes of BFX Acetabular Components

Introduction: Postoperative luxation is a common complication following total hip arthroplasty and can be associated with acetabular component malpositioning. Few studies have evaluated acetabular component positioning intraoperatively. The purpose of this study is to evaluate the categorization of the Angle of Lateral Opening (ALO) using three acetabular component sizes. Our null hypothesis is that the categorization of ALO based on the visible portion of the circular recess in the BFX acetabular component will be no better than random chance.

Materials and Methods: A plexiglass jig was utilized to position acetabular components of size 22, 28, and 34 mm at 35, 45, or 55 degrees of ALO (±0.5 degrees) and 10 degrees of truncated face retroversion. One reference image at each ALO for each size cup for a total of nine reference images was obtained. Ten images per component size at the specified ALOs (±0.5 degrees), totalling 30 images for a grand total of 90 study images, were generated using vertical beam fluoroscopy. A blinded observer categorized the 90 study images based on the reference images.

Results: Perfect categorization of the ALO by the blinded observer was achieved for 90/90 images. The weighted kappa coefficient with a 95% confidence interval was equal to 1. Perfect agreement was achieved between the actual measured ALO and the categorization of ALO by the blinded observer.

Discussion/Conclusion: This study demonstrates the perfect correlation between observed and known ALO; therefore, we reject our null hypothesis. This study demonstrates a potential method for intraoperative ALO categorization, but this method should be evaluated clinically.

Acknowledgment

The implants were provided by BioMedtrix/Movora, and two of the authors are consultants and course instructors for BioMedtrix/Movora.

Publication History

Article published online:
15 July 2025