LAUSR

BACKGROUND This study aimed to determine fracture line morphology of the greater tuberosity (GT) fragment of Neer 3 or 4 part proximal humerus fracture (PHF) and analyze the location relationship between the locking plate and the GT fragment. METHODS 71 three-dimensional computed tomography scans of Neer 3 and 4 part PHF were retrospectively reviewed. Fracture fragments were reconstructed and virtually reduced in the Mimics software, and fracture lines of GT fragments were depicted on a humerus template in the 3-matic software and then were superimposed altogether. The common sites of the GT fracture were identified, and the location relationship between the locking plate and GT fragments was analyzed in a computer-simulated scenario. RESULTS The fracture line morphology of GT fragments was similar between Neer 3 and 4 part PHF. The overall morphology of GT fragments was in a fan shape, which could be summarized as anterior, superior, posterior, and middle lines. Of these, we identified 43 split and 19 avulsion type GT fragments based on the Mutch classification. The overall morphology of split type fragments was in a fan shape, and avulsion type fragments showed a quite distinguishable distribution pattern. A GT fragment could be classified as anterior-split, posterior-split, complete-split, anterior -avulsion, and posterior-avulsion type based on its morphology and location. The median percentage of fragment area covered by the plate was 32.3% in all of the fragments, and it was 69.4%, 23.0%, 37.2%, 21.8%, 0.0% in anterior-split, posterior-split, complete-split, anterior -avulsion, and posterior-avulsion type GT fragments. CONCLUSION The fracture line morphology of GT fragments of Neer 3 and 4 part PHF was in a fan shape. GT fragments could be classified based on their location and morphology. The extent of GT fragment coverage provided by the locking plate differed in various fragment types, and preoperative evaluation of fragment type might help design surgical plans. LEVEL OF EVIDENCE Anatomy Study; Imaging.