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Open-face plane orientation of a BioMedtrix biologic fixation acetabular cup can be accurately determined from a
Owen T Fink1, Peter J Lotsikas1
1Skylos Sports Medicine, A BluePearl Hospital, Woodstock, MD.
Objective:
To develop and validate a method to calculate biologic fixation (BFX) acetabular cup open-face plane orientation based on measurements from a lateral radiograph.
Methods:
The formulas describing the open-face plane orientation were derived using geometric arguments and trigonometry. To assess the method, an in vitro plastic model of a pelvis was implanted with a BFX acetabular cup. A lateral radiograph of the implanted model was obtained and used to calculate the cup open-face plane orientation using the derived method. Direct measurement of the open-face plane orientation was performed, and the calculated values were compared to the directly measured values. The procedure was repeated with the cup in a different orientation for each trial.
Results:
52 trials were performed. The derived calculation method demonstrated high repeatability and reproducibility, with intra- and interobserver intraclass correlation coefficients > 0.94. The direct measurement method demonstrated high reproducibility, with interobserver intraclass correlation coefficients > 0.98. The mean absolute angular difference between the calculated and directly measured orientation vectors was 2.8 ± 1.3°, with 95% of trials within 4.7°.
Conclusions:
The open-face plane orientation determined by the derived method agreed closely with the directly measured orientation.
Clinical Relevance:
Knowledge of the BFX open-face plane orientation can inform decisions regarding cup revision, help identify complications associated with cup malpositioning, and allow the surgeon to improve their cup placement performance.
