Fluoroscopic Categorization of BFX Acetabular Component Positioning

Introduction: Few methods exist for intraoperative assessment of acetabular component angle of lateral opening (ALO). The purpose of this study is to evaluate a novel fluoroscopic method of ALO categorization based on identification of the visible portion of a pre-existing, circular recess within the shell of the acetabular component of the BFX cup, which projects as an ellipse at clinically relevant ALOs. Our null hypothesis is that categorization of ALO based on identification of the visible portion of the elliptical recess in the BFX acetabular component will be no better than random chance.

Materials and Methods: A custom plexiglass jig was fitted with a two-axis inclinometer and an acetabular cup attached to its tabletop. Fluoroscopic reference images were obtained with the cup at ALOs of 35, 45, and 55 degrees with 10 degrees of retroversion. Thirty study fluoroscopic images were sequentially obtained at ALOs of 35, 45, and 55 degrees (±0.5 degrees) with 10 degrees of retroversion, with 10 images at each ALO. The order of the study images was randomized, and a single, blinded observer categorized the 30 study images as representing a component ALO of 35, 45 or 55 degrees by comparison to the reference images.

Results: Analysis showed perfect (30/30) agreement with a weighted kappa coefficient of 1 (95% CI: 0.717–1).

Discussion/Conclusion: Perfect categorization of ALO was obtained in this study; therefore, we reject our null hypothesis. This method may prove to be a simple but effective method of estimating intraoperative ALO and its use should be evaluated in clinical cases.

Acknowledgement: The implant was provided by BioMedtrix LLC and two of the authors are consultants and course instructors for BioMedtrix LLC.

Publication History

Article published online:
26 October 2022