FRACTURES. - A fracture may traverse the acromion, the coracoid process, or detach the glenoid articular portion of the scapula from the body of this bone by passing directly across the neck of the scapula.
A. Fracture of the acromion process.— A fracture of the acromion process may be caused by the fall of a heavy body on the superior surface of the acromion ; but this accident most usually occurs in consequence of falls in which the patient is thrown from a height on the point of the shoulder. The fracture of the acromion will be generally found to have taken place at a point behind, and within, the junction of the clavicle with this bony process ; its direction we always observe to be in the original line of the junction of the epiphysis with the rest of the bone. In this accident, if the distance be measured from the sternal end of the clavicle to the extre mity of the shoulder, it will be found lessened on the injured side. Considerable ecchymosis of the shoulder may be expected soon to suc ceed the injury, and the patient will be unable to elevate the arm. Sometimes the perios teum of the acromion is not torn, and then, although the fracture of the bone has been complete, there is no displacement of the fragments. lf, however, this fibrous invest ment of the acromion, above and below, be completely torn across, the acromion process will be found to be depressed, because it will be pulled down by the weight of the extremity and contraction of the deltoid muscle. The portion of the acromion thus detached is generally very moveable, following the clavicle whenever the arm is moved. This accident is best recognised by the surgeon first taking hold of the elbow of the affected side and elevating the whole arm perpendicularly. " Having thus restored the figure of the part, he places his hand upon the acromion, and rotates the arm, when a crepitus can be dis tinctly perceived at the point of the spine_of the scapula." # Fractures of the acromion unite by bone, sometiines with much deformity, arising from ossific depositions, which however do not, after a time, interfere much with the motions of the arm. This union has sometimes been known to take place in forty-eight days, and in other cases in a much shorter time. The union, however, isfrequently only ligamentous.
Sir A. Cooper speaks of a false joint being occasionally the result of a fracture. Mal gaigne, alluding to a case in which a false joint was the consequence of a fracture of the acromion, says that the fractured surfaces presented a polished appearance and were covered with an ivory deposit, the effects of friction. He adds, that the union was not simply a ligamentous connexion, but that an arthroclial false joint had been formed. In all the specimens of this fracture examined by Malgaigne, the superior border of the fracture was surmounted ihith small bony crests of new formation, of which the more consider able number grew from the scapular portion of the acromion, while those produced from the detached extremity of' this process were but few, no doubt in consequence of its lesser degree of vitality. This remark of Malgaigne coincides with the observations to be found in Sir Astley Cooper's Work, that the dis position to ossific union is very weak in the detached acromion. Malgaigne, however, re fers to a preparation in the Museum of Du puytren, in which the external fragment pos sessed a thickness almost double that of the portion of bone from which it had been de tached. This thickness the writer of the Catalogue of the Museum thought was caused by an overlapping of the fragments of the broken portions ofthe acromion ; but Malgaigne supposes it to have arisen from sixnple hyper trophy of the detached fragments.
B. Fracture of the coracoid process— is a rare accident, and when it does occur, it is generally the result of a severe injury, in which the fracture of the bone is the least of the evils attendant on the compound injury. Thus Boyert gives us the account of a fracture of the coracoid process produced by the blow of a carriage pole ; the patient died in a few days afterwards, in consequence of the severe contusion he suffered at the moment of the accident. The coracoid process, when frac tured at its basis, is pulled downwards and forwards by the lesser pectoral coraco-bra chialis and short portion of the biceps muscle. We are told I that if the contusion accom panying this accident be slight. we can seize the fragment between the finger and thumb, and prove at once the mobility of the frag ment and the existence of crepitus.