A new screening method for multidirectional shoulder instability on magnetic resonance arthrography: labro-capsular distance.

ABSTRACT

OBJECTIVE: To compare the capsular dimension as measured on magnetic resonance arthrography (MRA) between patients with multidirectional instability (MDI) of the shoulder and control subjects without instability. Ultimately, we aimed to develop an easy and reliable new screening method to assess MDI of the shoulder using MRA. MATERIALS AND METHODS: MRA images of patients with MDI of the shoulder (n = 25) during a 6-year period (February 2010 to May 2015) were retrospectively reviewed. A control group (n = 26) without instability was also identified. The capsular area was measured using a new screening method we termed labro-capsular (LC) distance. MRA images of the two groups were randomly mixed, and two orthopedic surgeon reviewers recorded anterior, posterior, and inferior LC distance measurements on axial and coronal images using a mid-glenoid cut. RESULTS: The inferior LC distance increased significantly in the patient group versus control group (P < 0.001), but there were no statistically significant differences in the anterior (P = 0.1165) and posterior (P = 0.5229) LC distances. An inferior LC distance >16.88 mm is most suggestive of MDI of the shoulder because of its high sensitivity (76 %) and specificity (96 %). CONCLUSION: The inferior LC distance can be easily and quickly measured and used as an effective clinical screening method for atraumatic MDI of the shoulder.