Actual injury to tissues is to some extent unavoidable. In arthrodial joints the capsule is nearly always lacerated, at least upon one side. In hinge joints both lateral ligaments are likely to be ruptured. It is probable, however, that about the maxillary joints the ligaments may stretch without tearing to any extent. Not only are ligaments torn, but bony prominences are frequently detached, while sometimes there is extensive tearing away of tissue.
In connection with these injuries to joints proper other complications may occur, such as fractures of prominences about joints and epiphyseal separations, or such injuries as compound fracture of the neck of the humerus with dislocation of its head. Furthermore, bloodvessels are occasionally lacerated and nerves are frequently injured. This latter lesion is liable to occur after shoulder dislocations, the head of the bone injuring the circumflex nerve, paralysis of the deltoid being the consequence. This is a feature of the injury, and yet the result has often been unjustly imputed to the physician in attendance. Even a momentary contusion of the nerve may be followed by lasting effects, for which the medical attendant should be held blameless. Other injuries, e. g., contusions or lacerations of nerves, may occur about any of the joints.
Dislocations of the spine subject the cord to a special class of injuries which will be dealt with later in this work. In very rare instances the head of the humerus has been forced within the thorax or the head of the femur within the pelvis, these, injuries being practically always fatal.
Compound dislocations rarely occur about the jaw or shoulder. They pertain usually to the joints below. In every case of such character the question will be promptly raised whether a more or less complete exsection of the joint will not be preferable to mere reduction with the ensuing probability of ankylosis. Such injuries will, under all circumstances, require aseptic measures.
So far as repair is concerned, dislocations by themselves are so rarely fatal that there have been but few opportunities for a study of tissue recovery under these circumstances. It is apparent that repair is complete, for after almost any simple dislocation there is restoration of function.
The obstacles to reduction are spasm of muscles pertaining to the injured limb, by which the dislocated bone end is firmly held in its abnormal position, and, in those joints provided with a capsule, the fact that the head of the bone is frequently forced out through a comparatively small opening, through which it is only with the greatest difficulty reduced. It is a part of the manipulation in most cases to enlarge this rent in the capsule, after which reduction is comparatively easy, although impossible until it is accomplished.
Dislocations which have long gone unreduced are called old, inveterate, or ancient. By common consent a period of six weeks has been fixed, beyond which the dislocation is spoken of as old or ancient; up to that time it is usually described as unreduced. In proportion to the length of this period the difficulties of reduction are materially enhanced. So soon as a dislocated joint has been put at rest, i. e., fixed by muscle spasm and by the timidity of the patient, the blood which has been poured out will begin to coagulate and conditions are soon favorable for organization of clot and formation of adhesions in abnormal position. In the course of a few weeks these adhesions become strong, and in the course of months they are frequently stronger than the bone itself, which has been disused and has undergone a certain amount of fatty atrophy. Thus it happens that even with well-directed effort the bone will yield before the adhesions, and thus, in spite of every precaution, fracture sometimes complicates the effort to reduce these ancient dislocations.
So generally is this fact now recognized that surgeons do not hesitate to make open incisions for the purpose of separating adhesions and reopening what remains of the capsule in the endeavor to replace the head of a bone. Nor do they hesitate sometimes to cut down upon the latter and exsect rather than run the risk of more extensive injury.
Efforts at reduction under these circumstances subject the patient not only to risk of failure, or of fracture of bone ends, but to rupture of vessels or laceration of nerve trunks. I recall seeing one case of enormous traumatic aneurysm of the axillary artery which was brought about by unsuccessful attempt in this direction.