Glenoid morphology is associated with the development of instability arthropathy

Instability arthropathy (IA) is a major long-term concern in patients with anterior shoulder instability. This study investigated the association of glenoid morphology with the development of IA.The study included 118 patients with unilateral anterior shoulder instability and available bilateral computed tomography scans. Instability-specific information was obtained from all patients. The glenoid morphology of the affected shoulder was compared with the nonaffected contralateral side resembling the constitutional preinjury glenoid shape. Both shoulders were evaluated independently by 3 observers to assess the grade of IA according to a Comprehensive Arthropathy Rating (CAR) system. Associations between IA and the glenoid morphology parameters were investigated.The average glenoid retroversion (P .001), glenoid depth (P .001), glenoid diameter (P .001), and the bony shoulder stability ratio (P .001) of the affected shoulder were significantly reduced compared with the contralateral side due to bony defects in 79.6% of the patients. The CAR of the affected side was significantly higher (P .001), with more osteophytes (P = .001) and more sclerosis and cysts (P .001). Differences in CAR (Δ-CAR) correlated positively with the age at the time of the computed tomography scan (P .001), age at the initial dislocation (P = .001), size of the glenoid defect (P = .005), and the contralateral glenoid depth (P = .011), glenoid diameter (P = .016), and bony shoulder stability (P = .029), and negatively with glenoid retroversion of the affected side (P = .027).Development of IA arthropathy is associated not only with the age of the patients but also with morphologic parameters of the glenoid, including glenoid defect size and the constitutional glenoid concavity shape.