EP2.3 Acetabular Sector Angles, a helpful tool to deliver a one stop clinic service

Résumé fourni par la source

Abstract The radiological diagnosis of dysplasia is evolving beyond angular measurement on plain pelvic X-rays. The Lateral Central edge angle and Acetabular index are good measures of lateral coverage and inclination but are not a sensitive to anterior and posterior under coverage. Thresholds for femoral head coverage using topographic measurements against clearly dysplastic and normal X-rays have been described. This is an accurate but complex method, that requires extra time and costs. The Anterior Acetabular sector angle AASA and Posterior Acetabular Sector angle PASA are alternative readily available measurements, but their thresholds have not been determined against topographic measurements. Methods: A Retrospective review of CT scans of patients in local hip preservation registry was performed. Scans with reports analysing femoral head cover using a commercially available software were identified (Clinical Graphics, Zimmer Biomet). The anterior and posterior sector angle were measured. Pearson Correlation Coefficient was used to determine if there is a correlation between AASA and anterior coverage, and between PASA and posterior coverage. ROC analysis was performed to determine threshold values for anterior under coverage using AASA and posterior under coverage using PASA. Results: 90 reports were reviewed. 33.0% of patients had anterior under-coverage. 14.6% of patients had Posterior under-coverage. The Mean AASA was 60.0° ±11.8° and mean PASA was 99.9° ± 12.9°There was a high positive correlation between AASA and anterior coverage r= 0.68 (p<0.001) and a moderate positive correlation between PASA and posterior coverage r= 0.45 (p<0.001). AASA threshold for anterior under-coverage was <55° (AUC 0.843). PASA threshold for posterior under-coverage was < 91.7° (AUC 0.832). Conclusion: The AASA and PASA correlate with anterior and posterior coverage respectively. These measurements can be done in clinic which helps in delivering a one stop clinic service with no lag needed for analysis or extra costs incurred. Threshold values can aid in diagnosis of anterior and posterior instability patterns especially in setting of a normal LCEA. It is important to stress that the diagnosis is not solely based on these measurements and that the clinical assessment is key.

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