Morphological Variation of Modern Japanese Scapula Described using 3D Homologous Modeling Method

Abstract

We analyzed morphological variations of the Japanese scapula using 3-dimensional (3D) homologous modeling based on surface data recorded using a 3D scanner. Principal component (PC) analysis was applied to polygon mesh datasets of homologous vertices (X, Y, and Z points), which detected 20 components with a cumulative proportion at 84%. The first five components can describe approximately 50% of scapula variations in the samples used. The interpretation of these components are summarized as follows: PC1, anterior inclination of the glenoid fossa and coracoid process increased as the curvature of the scapular body increased; PC2, area of the infraspinatus fossa relative to the supraspinatus fossa increased as the vertical length of the scapular body increased; PC3, width of the supraspinatus fossa decreased with the forward tilt of the acromion; PC4, width of the supraspinatus fossa increased as the acromion overhung outward; and PC5, forward tilt from the scapular spine to the acromion. This study extracted several variations of the scapula, demonstrating the importance of comprehensively analyzing the overall shape of the scapula. We hope to elucidate the relationship between the overall scapular shape and shoulder disease using 3D homologous modeling.