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.
