Transformation between different local coordinate systems of the scapula

The existence of multiple local coordinate systems (LCSs) for the scapula makes it difficult to compare the kinematics of the scapula across various studies and reports. This study aimed to build transformation matrices between different LCSs for the scapula and to provide the coordinates of previously measured muscles and ligaments around the scapula with respect to the International Society of Biomechanics (ISB) recommended LCS. The bony landmarks necessary for building various local coordinate systems were digitized on 13 CT scanned scapulae. The LCSs were built based on the digitized bony landmarks and then used for calculating the transformation equations. The approximate coordinates of 28 muscles and ligaments of the scapula were expressed with respect to the ISB-recommended LCS using the derived transformation equations. The results of this study may be used for the comparison of scapula kinematics data with respect to various LCSs and for building a scapula biomechanical model with respect to ISB-recommended LCS.