الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Bony defects of the glenoid and the humeral head are common bony lesions in patients with recurrent anterior shoulder dislocation. The amount of bone loss is considered as a significant risk factor for the recurrence of the instability and increase of failure rate of labral repair. CT scan is still considered a gold standard imaging in assessment of bone lesions.
from June 2019 to October 2022, we conducted our study on 40 patients with recurrent anterior glenohumeral dislocation. All patients were subjected to CT scan with 3D reconstruction preoperatively. We used the concept of on-track and off-track which was introduced by Giacomo et al. to assess bone defects. Assessment of the glenoid defect was done using the 3D glenoid en face view after humeral head subtraction; a best-fit circle is placed along the posterior and inferior margins of the glenoid. The glenoid track (GT) is equal to 83% of total glenoid diameter (D) subtracted from it the diameter of the bone defect (d) as (GT= 0.83 D – d) in millimeters. We calculate the width of the Hill-Sachs interval on 3D reconstruction of the humeral head in posterior view, which is the width of the Hill-Sachs lesion plus the width of the bone bridge between medial border of the rotator cuff attachments and the lateral aspect of the Hill-Sachs lesion. If HSI > GT, the HS is off track. If HSI < GT, the HS is on track. Results were compared to intraoperative arthroscopic findings regarding engagement.
Our study showed that the on-track off-track method can be used to accurately assess the bipolar bone loss seen for predicting the presence of engaging lesions as there was no statistically significant difference (p= 0.18) between this method and arthroscopic findings with an overall accuracy of 87.5 % with a positive predictive value (PPV) of 91.7% and negative predictive value (NPV) of 81.3%.
This information can be used preoperatively to help guide the type of surgical procedure performed on a patient with anterior shoulder instability.