The forearm and humerus are still in contact, but the articulation is abnormal. Thus, in outward dislocation the ulna articulates with the trochlea and the head of the radius projects beyond the joint. As a rule, the forearm is at the same time displaced backward, producing the combination of lateral and posterior dislocation (luxatio posterior externa or postero-lateralis). While backward dislocation may occur without destroying the integrity of the lateral ligaments (although the internal ligament is, as a matter of fact, generally torn), lateral luxation is usually associated with great destruction of ligaments and fracture of the epicondyle. This variety is also described as an incomplete dislocation, in contradistinction to complete dislocation of the bones in which no portion of one articular surface remains in contact with any portion of the other. A lateral dislocation can only be produced by exaggerated movements of abduction or adduction. The capsule is greatly distended and sometimes presents a lateral tear. The symptoms of a complete lateral dislocation to the outside, for instance, are unmistakable and need no description. In incomplete outward dislocation (Plate 39) the prominence formed by the head of the radius is distinctly seen and felt. To the inner side, part of the trochlea can be seized between the fingers, and the separated internal epicondyle may be felt or appears as a marked prominence. By gently moving the parts under anesthesia a clear conception of the conditions is at once obtained. [Recently Eversmann 1 has reported two interesting observations of the outward lateral dislocation of the elbow-joint. In both cases the fragmented internal epicondyle had become displaced into the joint, and after the reduction of the dislocation, the interposition of this fragment produced symptoms and restricted function. Both 1 Deut. Zeitschr. f. Chir., 1901, Bd. LX, p. 528. were subjected to operation with good results. The Röntgen photographs of these two cases are quite clear. This possibility should always be borne in mind in this rare form of dislocation.-ED.] Incomplete inward luxation (luxatio postero-medialis) presents the external epicondyle in marked anterior displacement, or completely separated from the bone. The ulna projects beyond the inner line of the arm and its articular surface can be felt; the head of the radius articulates with the trochlea; and part of the capitellum humeri may be palpated. The prognosis depends on the complications. Treatment.-Reduction is effected under anesthesia with the least amount of injury to the patient by overextending the arm under direct lateral pressure with the other hand, followed by traction and flexion. If something is found interposed between the articulating surfaces, exaggerated lateral movements, overextension with abduction, etc., are sometimes successful. If efforts at reduction fail, early removal of the obstacle through an incision is indicated, preferably by means of a bilateral arthrotomy. Excellent results may be obtained by this procedure. (c) Forward Dislocation of the Forearm (Luxatio antibrachii anterior).-This is a very rare injury. It was formerly said that it never occurred without simultaneous fracture of the olecranon. It may be produced by a fall or blow on the olecranon while the arm is in extreme flexion. Symptoms. The prominence of the olecranon is missed from its normal position, and the outline of the lower end of the humerus can be felt on the posterior side of the bone. If the outer side of the olecranon is still in contact with the trochlea, the arm being almost in extension, an incomplete luxation exists. In complete dislocation the tip of the olecranon is found in front of the articulating surface of the lower end of the humerus, and the arm is bent at an acute angle. Reduction is effected by direct pressure, with moderate extension. (d) Divergent dislocation of the forearm (luxatio antibrachii divergens), the ulna being displaced backward and the radius forward, so that the humerus is driven like a wedge between the two bones of the forearm, is a very rare injury. The abnormal position of the various parts of the bone can be determined by direct palpation. In reducing the dislocation each bone is to be treated separately, the ulna by overextension and traction, and then the radius by direct pressure. (e) Isolated dislocation of the ulna is an injury that occurs very rarely by a fall on the hand in overextension and pronation of the forearm. The symptoms are the same as those of a posterior dislocation, except that there is no displacement of the head of the radius. The elbow is in varus position and the ulnar side of the forearm is shortened. Reduction is effected by means of overextension and traction. (f) Isolated dislocation of the radius is somewhat more common and occurs in various forms. Injury of the musculospiral or radial nerve has been observed as a complication. The head of the radius may be displaced backward, forward, or outward: Uncomplicated outward dislocation is a very rare form, the dislocation being more frequently associated with fracture in the upper third of the ulna (Plate 43). The head of the radius may be felt at the outer border of the external condyle, the radial side of the forearm is shortened; the elbow is, therefore, in valgus position. Reduction is effected by direct pressure; sometimes the elbow must be brought into varus position. Backward displacement is very rare. It is readily recognized by palpation of the head of the radius. The elbow is midway between pronation and supination. The patient cannot perform extension or supination. Reduction is effected by direct pressure, assisted by forcible traction on the forearm, which must be brought into varus position. It is Anterior dislocation is somewhat more common. produced by a blow against the head of the radius from behind, or by a fall on the hand in pronation. The head of the radius is found in front of and above the capitellum humeri and forms a prominence in the region of the supinator muscles. The forearm is slightly flexed and pronated; active supination is impossible; flexion beyond a right angle is impossible. The radial side of the forearm is shortened, unless the injury is complicated by a fracture in the upper third of the ulna (q. v.). Reduction is best effected by vigorous traction and simultaneous supination with the elbow in flexion. In all these cases of isolated dislocation of the radius, the annular ligament is torn, or the head of the bone escapes from beneath it. Not rarely, especially in anterior dislocation, reduction becomes difficult, if not impossible, on account of interposition of portions of the capsule. Arthrotomy is then indicated, and reduction is forcibly secured by removing the interposed tissues. The same procedure is indicated in old cases.. The longitudinal incision is made on the radial side of the joint; if the joint is entered from the front, there is danger of dividing the musculospiral nerve. In very severe cases arthrotomy may have to be abandoned in favor of resection. The after-treatment of all these dislocations must be carried out on general principles. (B) Intra-articular Injuries Various intra-articular injuries may be united under the designation dérangement interne. One example of this has already been referred to in separation of the capitellum humeri (page 185). Another injury deserves special mention, not because the etiology and symptom-complex are not perfectly well known, but because the anatomic details still form the subject of controversy. The accident occurs in little children and is produced by the nurse or attendant violently pulling the child's arm, either to prevent it from falling or to pick it up when it has slipped down from the lap, etc. Symptoms. The arm hangs at the side and the elbow is held immovable in pronation; there is no demonstrable deformity. Attempt at supination is very painful, but if it is carried out and traction is at the same time applied, followed by flexion, the pathologic condition disappears. The child can use its arm again, although it is better to have it carried in a sling for a few days. This symptomcomplex, which recurs again and again in a most typical form, is regarded by some surgeons as the result of an incomplete dislocation of the radius forward, by others as the result of a compression of the uninjured articular capsule at its posterior side, between the head of the radius and the humerus. 6. FOREARM An explanation of the frequency of fractures in the forearm is given by its function in the performance of work and in protecting the body against injuries. We distinguish between fractures of the forearm-that is, of both bones and isolated fractures of the ulna and radius alone. (A) Fracture of Both Bones of the Forearm (Fractura Antibrachii) This fracture is usually the result of direct violence, either a fall or a blow. In children infractions with bending of the forearm (greenstick fractures) are common. Symptoms. As a rule, the presence of a fracture is at once suggested by the angular deformity (ad axin); on careful examination abnormal mobility and crepitation are found. As the fractures preferably affect the middle third of the forearm, these phenomena can, as a rule, be demonstrated with ease and positiveness. Fractures of the forearm bones near their lower end will be discussed |