The association of rotator cuff muscle morphology and glenoid morphology in primary glenohumeral osteoarthritis.

Background: This retrospective study investigated associations of rotator cuff muscle atrophy (MA) and fatty infiltration (FI) with glenoid morphology.

Methods: Patients with primary glenohumeral osteoarthritis who presented to Penn State Bone and Joint Institute's orthopaedic clinic from September 2002 to December 2019 as total shoulder arthroplasty (TSA) candidates were evaluated. MA was determined by the cross-sectional area of each rotator cuff muscle on pre-operative MR and CT scans. Fat-free muscle and FI areas were quantified using Hounsfield units (HU). Glenoid morphology was assessed using glenoid version and inclination and modified Walch classification.

Results: Sixty-one patients (61 shoulders) were evaluated. B3 glenoids had a greater percent FI of supraspinatus (40.8 ± 7.3) versus A2 glenoids (31.6 ± 12.9,  = 0.032); infraspinatus and teres minor muscles (49.7 ± 9.1) versus A1 (31.1 ± 13.1,  = 0.039), A2 (30.2 ± 13.3,  = 0.028), and B1 glenoids (31.6 ± 11.9,  = 0.038); and subscapularis (36.7 ± 11.1) versus A2 glenoids (25.5 ± 14.7,  = 0.032). B2 glenoids had a larger area ratio of infraspinatus and teres minor to subscapularis (0.96 ± 0.16) than A1 (0.82 ± 0.13,  = 0.026) and A2 glenoids (0.57 ± 0.25,  = 0.038).

Conclusion: B3 glenoids had a greater FI of all rotator cuff muscles. B2 glenoids had a larger relative size of infraspinatus and teres minor muscles than subscapularis.