Magnetic Resonance Imaging Does Not Accurately Estimate the Size of Glenoid Labrum Tears in Patients With Shoulder Instability.

Purpose: To compare magnetic resonance imaging (MRI)-based measurements of glenoid labral tears with intraoperative measurements. Methods: A retrospective review was performed of patients that underwent shoulder capsulorrhaphy between 2019 and 2024 at a single academic medical center. All patients with a single labrum tear, an MRI within 6 months of surgery, and historical tear measurements or measurable intraoperative photographs were included in the study. Glenoid labrum tear size was noted using the clockface convention described in "hours." When clockface measurements were not reported on MRI reads, measurements were made by a radiologist. When clockface measurements were not reported in operative notes, measurements were made by an orthopaedic surgeon using intraoperative photographs. A paired Results: Two hundred sixteen glenoid labral tears from 211 patients met inclusion criteria. Average age was 27.2 ± 11.8 years, 68.5% of patients were men, and 56.9% of glenoid labrum tears were right-sided. On average, MRI measurements exceeded intraoperative measurements (4.15 ± 2.90 hours vs 2.80 ± 1.59 hours) with an average difference of 1.36 ± 3.09 hours (95% confidence interval = 0.94-1.77, Conclusions: MRI overestimated glenoid labrum tear size compared with intraoperative measurements and differed substantially between the 2 modalities on a case-by-case basis, with men displaying a larger discrepancy in measurement difference than women. These findings indicate that MRI may be more appropriately used as a categorical tool for confirming the presence of glenoid labral tears, rather than as a precise measure of tear size. Level of Evidence: Level III, retrospective diagnostic case series.