Patients who suffer anterior shoulder dislocations are at higher risk of developing glenohumeral arthropathy, but little is known about the initial cartilage damage after a primary shoulder dislocation. T1 is a magnetic resonance imaging (MRI) technique that allows quantification of cartilage proteoglycan content and can detect physiologic changes in articular cartilage.

This study aimed to establish baseline T1 MRI values for glenoid and humeral head cartilage, determine whether T1 MRI can detect glenohumeral cartilage damage after traumatic primary shoulder dislocation, and assess for patterns in cartilage damage in anterior shoulder dislocation.

Cross-sectional study; Level of evidence, 3.

Nine male patients (mean age, 32.0 years; range, 20-59 years) who sustained first-time anterior shoulder dislocations underwent 3T T1 MRI. Five healthy controls (mean age, 27.4 years; range, 24-30 years) without prior dislocation or glenohumeral arthritis also underwent 3T T1 MRI. The T1 relaxation constant was determined for the entire glenoid and humeral head for patients with a dislocation and for healthy controls. The glenoid and humeral head were divided into 9 zones, and T1 values were determined for each zone in dislocated and control shoulders to identify patterns in cartilage damage in dislocated shoulders.

Average overall T1 values for humeral head cartilage in dislocated shoulders were significantly greater than in controls (41.7 ± 3.9 ms vs 38.4 ± 0.6 ms, respectively; P = .03). However, average overall T1 values for glenoid cartilage were not significantly different in dislocated shoulders compared with controls (44.0 ± 3.3 ms vs 44.6 ± 2.4 ms, respectively; P = .40), suggesting worse damage to humeral head cartilage. T1 values in the posterior-middle humeral head were higher in patients with a dislocation compared with controls (41.5 ± 3.8 ms vs 38.2 ± 2.2 ms, respectively; P = .021) and trended toward significance in the posterior-superior and middle-superior zones (35.2 ± 4.9 ms vs 31.3 ± 1.0 ms and 33.7 ± 5.0 ms vs 30.5 ± 1.3 ms, respectively; P = .056). These 3 humeral head zones are where Hill-Sachs lesions predominate. T1 values in the anterior-inferior glenoid zone trended toward significance in patients with a dislocation compared with controls (47.4 ± 5.0 ms vs 43.5 ± 3.5 ms, respectively; P = .073).

Humeral head cartilage sustained greater damage than glenoid cartilage in primary dislocation. T1 values were higher in glenohumeral zones associated with Bankart and Hill-Sachs lesions. Widespread initial cartilage damage may predispose patients to glenohumeral arthropathy.