Influence of the labrum on version and diameter of the glenoid: a morphometric study using magnetic resonance images

To use magnetic resonance imaging to determine the influence of the labrum on both the osseous version and effective diameter of the glenoid.This was a retrospective, cross-sectional study of patients with shoulder pain who\ua0underwent MRI between February 2014 and February 2015. The morphology of the glenoid labrum and glenoid was scanned with a 3-T magnetic resonance imaging scanner, and variables were measured by use of IntelliSpace PACS Enterprise. Patients were included if they were aged between 18 and 40\ua0years and the radiologist reported a normal glenohumeral joint or if they were young patients aged less than 30\ua0years with acute traumatic isolated partial- or full-thickness tears of the rotator cuff with a history of symptoms of less than 3\ua0months. A pilot study was conducted with 3 observers and 3 repeated measurements at intervals to determine the interobserver and intraobserver reliability. Data analysis included descriptive statistics of measured variables, as well as paired Student t tests to determine the relative difference between labral and osseous morphometric variables.Excellent inter-rater reliability (0.95-0.96) and intrarater reliability (0.93-0.98) were obtained in the pilot study of 20 patients. The study population was composed of 100 patients with a mean age of 37.3\ua0years (standard deviation [SD], 11.8\ua0years), having a gender distribution of 56 male and 44 female patients; there were 53 right and 47 left shoulders. The glenoid osseous version measured\ua0-5.7° (SD, 5.3°), and the labral version measured\ua0-10° (SD, 5.5°); the glenoid osseous diameter measured 28.0\ua0mm (SD, 3.3\ua0mm), and the labral diameter measured 31.9\ua0mm (SD, 3.2\ua0mm). The labrum significantly increased the version by 4.3° (P\ua0= .001) and significantly increased the diameter by 3.9\ua0mm\ua0(P\ua0= .001).The results of this study showed that the labrum increased the effective glenoid version by 75% (4.3° of retroversion) and the effective glenoid diameter by 14% (3.9\ua0mm).Level IV, prognostic case series