Comparison of a Novel Cup Position Assessment Device Using Fluoroscopy with CT Assessment and Direct Measurement of Acetabular Component Position in Total Hip Arthroplasty in Dogs

Introduction: No intraoperative method to assess acetabular cup position has been shown to be clinically feasible in veterinary medicine. This study aimed to compare the measurements of angle of lateral opening (ALO) and version of a BFX cup in cadaveric pelvises, using a cup position assessment device (CPAD) with fluoroscopic imaging, computed tomography (CT), and direct measurement. Our null hypothesis is that there will be no difference between the measures of ALO and version obtained with fluoroscopy with the CPAD, CT, and direct measurement.

Materials and Methods: Six canine cadavers were implanted with BFX cups. The CPAD was placed and images were obtained with fluoroscopy during implantation. Measurements were obtained from the radiopaque marker bars on the CPAD device; version, and ALO were calculated using trigonometry. Postimplantation ALO and version were then measured on the cadaveric pelvises by CT imaging and direct measure on a jig. The measurements were compared using a two-way ANOVA and a generalized linear model analysis.

Results: There were no significant differences between the measurement groups for ALO or version. Interclass correlation coefficients between the measurement methods resulted in a correlation of 0.948 and 0.951 for ALO and version, respectively.

Discussion/Conclusion: The results demonstrate that intraoperative imaging in cadaveric specimens with the CPAD is an accurate method to determine ALO and version. There was excellent correlation between groups suggesting it to be a reliable method for intraoperative assessment of ALO and version.

Acknowledgment: There are no proprietary interests to declare. Funded by the Tufts Orthopedic Research Laboratory and Arizona Canine Orthopedics & Sports Medicine.