DISLOCATIONS OF THE ELBOW stand second in order of frequency, and are most common in persons under twenty five. 'Among the great variety of forms of dislocations of both bones, the back ward are by far the most frequent.
The divisions and subdivisions are as follows:— Dislocations of Both Bones Back,ward. —The inward and outward subvarieties are of no practical importance.
elbow is swelled and partly flexed. The olecranon may be felt displaced backward from the epicondyles and the head of the radius may be recog nized behind the external epicondyle as a bony point which rotates with the fore arm. The trochlear surface may be prominent in the bend of the elbow; the tendon of the biceps behind. Passive flexion and extension are moderate. There is abnormal lateral mobility in full extension.
The cause is most commonly a fall upon the outstretched hand forcing the two bones backward. The coronoid proc ess of the ulna is either broken or lifted over the trochlear surface by hyperexten sion or by abduction, which increases the normal outward deviation of the fore arm and a twist which swings the process downward and then backward.
internal lateral liga ment is torn, and the external one either torn or stripped away with the perios teum from the external condyle. Hence, in old dislocations reduction is effectually prevented by the mass of callus that 'forms beneath this elevated periostemn behind the external condyle. The front of the capsule is torn, the epitrochlea (internal epicondyle) may be broken by muscular action, or the muscles attached to it may be ruptured. Fractures of the head of the radius and coronoid process are rare. The latter, however, does not interfere with the action of the brachi alis anticus, as that muscle is attached to the base of the process: a part not interested in the fracture.
flexion is to be condemned as unscientific and less likely to succeed than pressure on the dislo cated bones combined with traction of the forearm in moderate extension or hyperextension. -Usually the dislocation is easily reduced. Sometimes ananthet ics are necessary. After reduction the limb should be immobilized by bandages and a sling for about three weeks, after which mild massage and active motion will gradually remove the stiffness. Early passive motion will not hasten the resnit, and may even increase the ex cessive production of callus which, in children, sometimes goes on even after reduction and may cause serious limita tion to the motion of the joint.
Lateral dis locations in either direction are said to be frequently overlooked or mistaken for fractures. The cause of lateral disloca tions is usually a fall upon the hand by which the normal outward angle at the elbow is increased by tearing of the in ternal lateral ligament and a downward movement of the ulna, directly away from the trochlea. The head of the radius then glides either outward or in ward, as the case may be, the ulna fol lowing.
In incomplete inward dislocations the forearm is pronated and slightly flexed; its long axis parallel to and a little to the inner side of that of the arm. The olec ranon and external condyle are promi nent, and the head of the radius can be felt displaced downward. and inward, resting below the trochlea (the greater sigmoid cavity of the ulna em.braces the epitrochlea). Flexion and extension are but little interfered with. Reduction is made by traction and direct pressure. In unreduced. cases there is very little disability, and operative interference is probably inadvisable.
Incomplete Outward Dislocations. — The forearm is pronated and slightly flexed, and its long axis is to the outer side of and parallel to that of the arm or else in abduction. The ulna is displaced so that the central ridge of the greater sigmoid cavity has passed beyond the outer rim of the trochlea; the radius lies partly below or entirely beyond the ex ternal condyle. The internal condyle and olecranon are prominent.
ridge of the sigmoid cavity must be unlocked from the groove between the trochlea and capitellum. This is done by traction or hyperexten sion (or by abduction, if the head of the radius rests below the external condyle and can be used as a fulcrum). Then the bones are pushed easily into place. The broken epitrochlea may lodge in the groove of the trochlea and effectually prevent reduction. Even if the disloca tion be not reduced, the joint may be I quite useful.
Complete outward dislocation occurs in three forms. In the simplest form the bones of the forearm are displaced di rectly outward, the inner edf„_,e of the olecranon resting against the outer side of the external condyle. If, now, the forearm is flexed and strongly pronated, the second form (subepicondylar) is pro duced, in which the anterior surface of the ulna looks inward and its sigmoid cavity embraces the outer side of the external condyle, while the radius lies above it, with its head in front of the epicondylar ridge. In the third form (supra-epicondylar) the dislocated bones are moved still further upward and back ward, so that their articular surfaces lie external to and behind the supinator ridge. Reduction is usually easy, owing to the extensive laceration to ligaments; but, even if unreduced, the elbow re mains fairly strong and mobile.
Forward rare in jury is usually caused by direct trauma to the back of the flexed elbow. The olecranon was broken in about a, third of the cases. If this is the case, the ulna and radius are displaced forward and up ward in the anterior surface of the humerus; but, if the olecranon remains intact, it may rest on the trochlea, or, the triceps being torn away, it may pass to the front of the humerus. Reduction by traction appears to have been easily accomplished.