Scapular morphology associated with rotator cuff tears: a three-dimensional shape analysis using homologous modeling

The mechanisms underlying rotator cuff tears are not well established. To elucidate the morphologic characteristics of the scapula associated with these tears, a comprehensive analysis of its global shape is essential. This study employed homologous modeling techniques to investigate scapular morphology related to rotator cuff tears.

Scapulae were modeled homologously from 28 male patients (male tear group) and 30 female patients (female tear group) who had undergone arthroscopic rotator cuff repair at Sapporo Medical University Hospital. Principal component scores for each tear group were derived from previously calculated eigenvectors in a principal component analysis. Receiver-operating characteristic curves and area under the curve values were computed separately for males and females to evaluate morphologic features indicative of rotator cuff tears.

Compared to controls, the male tear group presented scapulae that were vertically shorter and horizontally broader (principal component 1, area under the curve = 0.61), with an anterior inclination of the lateral scapular morphology, including the glenoid, acromion, and coracoid process, alongside an increased anteroposterior diameter of the supraspinous fossa (principal component 4, area under the curve = 0.60). Additionally, they displayed reduced scapular body curvature and a shortened anteroposterior diameter of the supraspinous fossa (principal component 8, area under the curve = 0.67). The female tear group revealed scapulae with an anteriorly displaced acromion, increased scapular body curvature, and an enlarged anteroposterior dimension of the supraspinous fossa (principal component 5, area under the curve = 0.69), or reduced scapular body curvature and a shortened anteroposterior diameter of the supraspinous fossa (principal component 8, area under the curve = 0.64).

A reduction in scapular body curvature is a critical morphologic characteristic associated with rotator cuff tears. Further research examining the relationship between these findings and the morphology of the humerus and thorax, as well as the periscapular musculature, may provide insights into the underlying mechanisms of rotator cuff tears.