Novel anterior coracoglenoid line utilizing magnetic resonance imaging (MRI) corresponds with critical glenoid bone loss

Glenoid bone loss is estimated using a best-fit circle method and requires software tools that may not be available. Our hypothesis is that a vertical reference line drawn parallel to the long axis of the glenoid and passing through the inflection point of the coracoid and glenoid will represent a demarcation line of approximately 20% of the glenoid. Our aim is to establish a more efficient method to estimate a surgical threshold for glenoid insufficiency. Fifty patients with normal glenoid anatomy were randomly chosen from an orthopedic surgeon's database. Two orthopedic surgeons utilized T1-weighted sagittal MRIs and the coracoglenoid line technique to determine the percentage of bony glenoid anterior to vertical line. Two musculoskeletal radiologists measured the same 50 glenoids using the circle technique. Differences were determined using dependent t test. Reliability was compared using interclass correlation coefficient and Kappa. Validity was compared using Pearson correlation coefficient. Mean surface area of the glenoid anterior to the vertical line was on average 21.69% ± 3.12%. Surface area of the glenoid using the circle method was on average 20.86% ± 2.29%. Inter-rater reliability of the circle method was 0.553 (fair). Inter-rater reliability of the vertical line technique was 0.83 (excellent). There was a linear relationship between circle and vertical line measurements, r = 0.704 (moderate to high). The coracoglenoid line appears to represent a line of demarcation of approximately 21% of glenoid bone anterior to the coracoglenoid line. Our technique was found to be reliable, valid, and accurate.