Glenoid rim morphology in young athletes with unstable painful shoulders: primarily painful vs. frankly unstable

BACKGROUND: To investigate the characteristics of glenoid rim morphology in young athletes (<40 yr) with unstable painful shoulder METHODS: This was a retrospective case series. The inclusion criteria were as follows: (1) shoulder pain during sports activity, (2) traumatic onset, (3) no complaint of shoulder instability, and (4) soft tissue or bony lesions confirmed on imaging examinations (computed tomography and magnetic resonance imaging). The above-mentioned painful cohort was then compared (in a 2:1 ratio) to a match-paired control group of patients with similar demographics but with frank anterior glenohumeral instability as defined by imaging and physical findings. The pain (not apprehension) was reproduced during the anterior apprehension test in supine position and relieved by relocation test in all patients. Glenoid rim morphology, bone union in shoulders with a fragment-type glenoid, glenoid defect size, bone fragment size, medial displacement of bone fragments (MDBF), and medial distance of erosion (MDE) were compared between painful shoulders and unstable shoulders. RESULTS: There were 79 painful shoulders and 165 unstable shoulders. The glenoid rim morphology was normal in 33 shoulders, erosion-type in 15 shoulders, and fragment-type in 31 shoulders among painful shoulders, whereas the respective shoulders were 19, 33, and 113 among unstable shoulders (P < .001). Bone union was complete in 15 shoulders, partial in 14 shoulders, and nonunion in 2 shoulders among painful shoulders, whereas the respective shoulders were 43, 31, and 39 among unstable shoulders (P = .001). The mean glenoid defect size was 6.0 ± 7.2% and 12.7 ± 7.4%, respectively (P < .001), and the mean bone fragment size was 5.8 ± 6.4% and 5.4 ± 4.6%, respectively, (P = .591). The mean MDBF was 1.4 ± 1.5 mm and 3.0 ± 2.2 mm, respectively (P < .001), and the mean MDE was 2.3 ± 1.2 mm and 5.2 ± 2.4 mm, respectively (P < .001). In shoulders with a smaller glenoid defect (<13.5%), the prevalence of shoulders with MDBF (<2 mm) and shoulders with MDE (<2 mm) was more frequent in painful shoulders. On the other hand, in shoulders with a larger glenoid defect (≥13.5%), erosion-type glenoid, nonunion in fragment-type glenoid and bone fragment smaller than 7.5% was not recognized in painful shoulders. Shoulders with MDBF (<2 mm) were significantly more frequent in painful shoulders (P = .009). CONCLUSIONS: In painful shoulders normal or erosion-type glenoid was predominant, and glenoid defect size was significantly smaller than unstable shoulders. On the other hand, a large bone fragment (≥7.5%) remained and united completely or partially in all shoulders with a larger glenoid defect (≥13.5%). Bone union was obtained within 2 mm from the articular surface in most of them.