FRACTURES OF THE ACROMION AND THE LATERAL SCAPULAR SPINE

We studied 37 fractures lateral to the spinoglenoidal notch to evaluat e the validity of collectively handling these fractures as an acromion fracture and to ascertain the mechanism of injury. We divided them in to three groups according to the location of the fracture line. Fractu re of the anatomic acromion or the extremely lateral scapular spine (g roups I and II, 28 fractures) was frequently associated with fracture of the coracoid base, acromioclavicular joint injury, or both. The mec hanism of injury in most cases was presumed to be indirect force broug ht to bear on the shoulder from the lateral direction. Fracture descen ding to the spinoglenoidal notch (group III, nine fractures) was seldo m associated with other shoulder injuries, and surgery was rarely need ed. The mechanism was assumed to be direct force brought to bear on th e shoulder from the posterior direction. Therefore fractures of the an atomic acromion and the extremely lateral scapular spine may be manage d collectively. However, fracture descending to the spinoglenoidal not ch should be managed separately. We advocate that these fractures shou ld be classified into two types in terms of-clinical consideration: ty pe I fractures, comprising those of the anatomic acromion and the extr emely lateral scapular spine, and type II fractures, located in the mo re medial spine and descending to the spinoglenoidal notch.