Surgical Anatomy. — The head of the radius may be likened to a short cylinder. The upper end articulates with the capitellum and is slightly concave. The sides of the cylinder are in contact with the orbicular ligament and lesser sigmoid cavity while the lower end of the cylinder is continued into the neck of the radius. The lower end is slightly less in diameter than the upper end, and the orbicular ligament thus secures a hold on the upper extremity of the bone which tends to prevent downward displacement. The interosseous membrane and the oblique ligament, together with the orbicular ligament, bind the radius to the ulna though they allow free motion in pronation and supination. The external lateral ligament of the elbow is not attached to the radius but divides and blends with the orbicular ligament, passes in front of and behind the radial head, and is attached to the ulna anterior and posterior to the lesser sigmoid cavity. The head of the radius articulates with the lower end of the humerus and with the ulna at the lesser sigmoid cavity.<Callout type="important" title="Important">The exact mechanism of dislocations of the radius is not clear, but it requires reduction.</Callout> Malgaigne's luxation (downward subluxation) has also been the subject of much discussion and there is little known concerning the mechanism of the injury. The consensus of opinion, however, is that there is a slight downward luxation of the radial head, and that there may be some infolding of the ligaments between the articular surfaces. This luxation is confined to children, usually under three or three and a half years of age, and is due to traction in the axis of the radius.<Callout type="warning" title="Warning">Children under 3-3.5 years are more susceptible to Malgaigne's subluxation.</Callout> There is no hard and fast line to be drawn between outward and backward luxations of the radial head, one form merges into the other. The relation between these two types is much the same as that already noted between backward and outward luxations of the elbow. Any form of isolated luxation of the radial head is rare as compared with luxations of the elbow.<Callout type="tip" title="Tip">Forward luxations are more common than backward or outward ones.</Callout> Symptoms. — In any type of luxation of the head of the radius there is pain in the region of the injury and loss of function immediately following the accident. The deformity will vary with the direction of the displacement.<Callout type="risk" title="Risk">Pain may be minimal, leading to delayed diagnosis.</Callout> In the backward or outward types the head is felt standing out in a position anywhere between posterior and external to its normal position, and may be identified by the characteristic cup-shaped extremity and by its rotation with the shaft during pronation and supination. The forearm is, as a rule, completely pronated and in a position just short of complete extension. Further examination shows that supination is checked by the altered mechanism of the joint, though strange to say this function seems to be regained in old unreduced luxations.<Callout type="important" title="Important">Backward or outward luxations are more common and easier to identify.</Callout> In forward luxations the elbow is partially flexed and the forearm may be either supinated or pronated, usually the latter. Pronation is, as a rule, complete, and passive supination blocked. Flexion beyond a right angle is never possible in recent cases; the head of the radius coming in contact with the anterior surface of the bone prevents flexion. Palpation of the forearm below the external condyle reveals the absence of the radial head from its normal position. The bend of the elbow is usually swollen and the displaced end of the bone may be palpated, though it is seldom as distinctly felt as is the case in backward and outward luxations. Old unreduced cases may show remarkable restoration of function as in the backward and outward types.<Callout type="beginner" title="Beginner">Forward luxations can mimic other conditions, requiring careful examination.</Callout> Diagnosis. — The diagnosis of luxations of the radial head depends on the restriction of motion, the characteristic attitude and palpation of the head of the bone in its displaced position while the upper end of the ulna remains normally placed. The diagnosis of Malgaigne's luxation is based largely on the history of the case and the disinclination on the part of the child to use the member. The history is typical. The condition is the result of the pernicious habit of lifting a child by the hand; mothers are prone to do this in helping children on and off of street cars, and in hurrying them along the street. Following injury to the arm in this way the child fails to use the member and objects to having it disturbed.<Callout type="gear" title="Gear">Splints and adhesive straps can be used for reduction and immobilization.</Callout> The X-ray is of value chiefly in determining associated lesions, such as fracture of the radial head or neck or of the external condyle of the humerus, or a break in the ulna.<Callout type="important" title="Important">X-rays are useful for identifying fractures but not essential for diagnosis.</Callout> Treatment. — Reduction in the backward and outward types is usually easy, though the head may tend to slip out again as soon as the arm is released. Retentive dressings should be in readiness before returning the head to its normal position. Extension and counterextension, accompanied by direct pressure on the head in the direction of the capitellum, will, as a rule, effect reduction. The degree of flexion in which there is least tendency for the head to slip out of position should be determined in each case and the joint immobilized in this position. A pad maintained in place by straps of adhesive and exerting direct pressure on the upper end of the bone may be of service in preventing recurrence of deformity. The head of the bone may be fractured against the capitellum as it is driven out of place, and when this complication exists it may increase the tendency to reluxation.<Callout type="risk" title="Risk">Fractures during reduction can complicate treatment.</Callout> In forward luxations similar principles are employed. Reduction is accomplished by extension, counterextension and direct backward pressure on the displaced head. When the head of the radius is felt to move backward the elbow is flexed and the manipulation is complete. To prevent recurrence of deformity the elbow should be immobilized in a position just short of acute flexion (see Fig. 210). When luxation of the radial head is complicated by fracture of the ulna, increased difficulty may be experienced in preventing reluxation. In addition to treating the dislocation we have the fragments of the ulna to maintain in apposition. Under these circumstances internal and external angular splints will be found more efficient than the position of acute flexion advised in the uncomplicated anterior dislocation. If the elbow is to be immobilized at a right angle the ordinary internal and external angular splints will be satisfactory. If, however, some other degree of flexion is desired plaster splints may be needed. If ordinary means are not efficient in preventing deformity in either the fracture or the luxation operation should be resorted to.<Callout type="important" title="Important">Immobilization techniques vary based on the specific injury.</Callout> The reduction of Malgaigne's luxation is usually accomplished without difficulty. It consists in forcing the head of the radius upward against the capitellum, and is accomplished in the following manner. The surgeon grasps the lower part of the arm to fix the humerus while the opposite hand secures the forearm at about its middle; the forearm is then rotated (supinated and pronated) while upward pressure in the axis of the radius forces the head of the bone up against the capitellum. Reduction is usually accompanied by a soft click, after which all the functions of the joint are found to be normal and painless. Aften this maneuver is complete the elbow is tested by carrying the forearm through flexion, extension, supination and pronation. If the function is not completely restored and painless the manipulation should be repeated. It may be necessary to alternate extension with upward pressure. It will only be a few hours following reduction until the child is using the arm freely and without discomfort. The condition is not a serious one even if allowed to go unreduced, but proper treatment will relieve the child and obviate much anxiety. The displacement will not return unless the same forces which first produced the subluxation are again inflicted on the parts, and accordingly all that is necessary to prevent recurrence is to see that those having to do with the child are thoroughly informed and cautioned concerning the manner in which the injury was produced.<Callout type="important" title="Important">Proper care instructions can prevent recurrence.</Callout> Operative Treatment. — The open method is indicated when other means fail to accomplish and maintain reduction for the correction of ancient luxations and occasionally in the treatment of complications. A longitudinal incision is made over the head of the radius, the bone exposed and reduction effected by direct manipulation. It may be possible to suture the torn orbicular ligament after the head has been replaced, though in some cases it may be difficult to recognize this structure. In any case it is proper to suture the structures surrounding the upper end of the bone in such a manner as to prevent redisplacement. When the radial head is much comminuted it is often better to remove the fragments, round up the end of the bone and suture the tissues about it. Rotation of the upper end of the bone, as evidenced by supination and pronation, is seldom lost following these operations if the axis of the radial shaft remains unchanged. Moreover these cases usually show a surprising stability of the joint when recovery is complete.<Callout type="important" title="Important">Comminuted fractures may require surgical intervention.</Callout> Complicating fracture of the upper end of the ulnar shaft is not an uncommon condition accompanying anterior luxation and may demand operation to maintain reduction in both fracture and dislocation. The dislocation is not particularly prone to recur but the fracture is sometimes difficult to hold in reduction because of the instability of the radio-humeral articulation. It is more often necessary to wire the fracture in the ulna than it is to operate on the luxation. If the ulna is approached through a posterior incision and the fragments secured by internal fixation it will often be possible to treat the luxation in the flexed position, and thus prevent displacement of the radial head.<Callout type="important" title="Important">Internal fixation can help maintain reduction.</Callout> If the upper end of the bone has been allowed to remain displaced the removal of longitudinal pressure commonly results in an over-growth of the bone with a corresponding increase in length. In operating on ancient luxations, therefore, it may be necessary to resect the head of the bone before the shaft can be brought back into alignment. Old anterior luxations come to operation more frequently than either the outward or posterior types because of the loss of acute flexion in forward dislocations. The excellent functional results following operation on old cases, even when the head is resected, are often surprising.<Callout type="important" title="Important">Resection may be necessary for chronic cases.</Callout> Malgaigne's subluxation never requires operation.<Callout type="warning" title="Warning">Malgaigne's luxation only affects children under 3-3.5 years and does not require surgery.</Callout> After-Treatment. — The elbow should be fixed in the position least favorable to recurrence for a period of at least twenty-five to thirty days. In anterior luxations there is usually less tendency to recurrence and accordingly the period of fixation need not be so long. Three to four weeks will, as a rule, be ample. When fracture complicates luxation union of the fragments is the chief consideration in the after-treatment and the retentive dressings should be removed only after one is satisfied that union is firm (usually four or five weeks). When fracture is present the case will require more careful supervision. The traumatic reaction is greater and the same precautions are to be observed as cited under fractures of the bones of the forearm. Malgaigne's luxation requires no after-treatment.<Callout type="important" title="Important">Fixation duration varies based on the specific injury.</Callout> Prognosis. — In the uncomplicated luxation of the head of the radius, where reduction has been effected, restoration of function should be complete. If complications exist the prognosis varies with the nature of the associated injury.
Key Takeaways
- Dislocations of the head of the radius can vary in direction and mechanism, but require reduction.
- Malgaigne's subluxation is a specific type affecting young children due to improper lifting techniques.
- Proper immobilization and splinting are crucial for preventing recurrence after reduction.
Practical Tips
- Always ensure proper alignment before attempting to reduce any dislocation, as misalignment can lead to further injury.
- For forward luxations, carefully examine the elbow for signs of other conditions that may mimic a luxation.
- Use X-rays to identify associated fractures but understand they are not necessary for initial diagnosis.
Warnings & Risks
- Be cautious when reducing dislocations as improper technique can lead to complications such as fractures or nerve damage.
- Avoid applying excessive force during reduction, which could cause further injury to the joint.
- Proper care instructions and patient education are essential to prevent recurrence of dislocations.
Modern Application
While the specific techniques for treating dislocations have evolved with modern medicine, understanding the anatomy and recognizing the signs of a radial head dislocation can be crucial in emergency situations. The principles of proper immobilization and reduction remain relevant, making this historical knowledge valuable for modern survival preparedness.
Frequently Asked Questions
Q: What is Malgaigne's subluxation?
Malgaigne's subluxation is a specific type of downward dislocation of the head of the radius that typically affects young children under three or three and a half years old, usually due to improper lifting by their caregivers.
Q: How can I prevent recurrence after reducing a radial head dislocation?
Proper immobilization using splints or casts is crucial. Ensure the elbow is fixed in the position least favorable to recurrence for at least 25-30 days, and follow up with X-rays if necessary to check for proper healing.
Q: What are some signs of a radial head dislocation?
Symptoms include pain, loss of function, and deformity in the elbow. The forearm may appear misshapen or displaced, especially in backward or outward types. In forward luxations, the elbow is partially flexed, and the forearm may be supinated or pronated.