Patient name: Smith, John

Emergency room

Laboratory


                  wbc     rbc

                5.1-10    3-4	

       

03/03/99 0600     6.2     1.5 L!   



  - Commments:

03/03/99 0600   This is test.

Radiology

A 9 year old male fell off a slide and landed on his outstretched left arm. He now presents to the ED with pain in his left forearm and elbow. There is no history of head trauma. He denies having a headache, and there is no nausea or vomiting. His past medical history is unremarkable.
Exam: Vital signs T37, P76, R20, BP110/73. He is alert and oriented but in obvious discomfort secondary to left arm pain. Pupils are equal and reactive. His left clavicle, shoulder and humerus are nontender. His left hand and wrist (including the anatomic snuffbox) are also nontender. He is tender over the proximal aspect of his left forearm. He is unable to flex, extend, supinate, or pronate at his left elbow. He is able to move all his fingers well. Distally, he is neurovascularly intact. Capillary refill time is 2 seconds. Radiographs of his left forearm and elbow were obtained.
View forearm radiographs.

View elbow radiographs.

There is an obvious mid-shaft ulnar fracture. Do you see anything else wrong with the radiographs? Look at the radiographs again. The radial head should point at the capitellum in all views. A line drawn down the long axis of the radius (radial head) should intersect the capitellum in all views. Review Case 12 (Radiographic Examination of the Elbow) for further discussion on the radiocapitellar line.
In this case, the line drawn down the long axis of the radius does not intersect the capitellum. This indicates that the radial head is dislocated. In this case, there is an anterior dislocation of the radius. There is a prominent anterior fat pad visible, which is probably within normal limits. No posterior fat pad sign is seen.
The patient was taken to the OR for closed reduction under general anesthesia.

Teaching points and Discussion.
1. In 1814, Monteggia first described the combination of proximal ulnar fracture with anterior dislocation of the radial head. The Monteggia fracture-dislocation now includes several different types of ulnar fractures with radial head dislocation. In children, the classic form of Monteggia's injury is uncommon. Monteggia fracture-dislocation comprises 2% of all elbow fractures in children.
2. Monteggia's injury can easily be overlooked. In general, isolated ulnar fractures are very rare. With any type of ulnar fracture, it is important to have radiographs of both the forearm as well as the elbow joint. Recognition of a Monteggia's injury is critical because if the radial head is not reduced, it could lead to permanent disability.
3. The most common mechanism of injury in children is hyperextension at the elbow joint. This results in fracture of the ulna with anterior angulation and an anterior dislocation of the radial head. Another mechanism is hyperpronation of the forearm with a fall on an outstretched hand. The annular ligament is either torn or is displaced over the radial head.
4. On examination, there may be tenderness, swelling, and deformity at the site of the ulnar fracture. This can sometimes distract the examiner from noticing injury at the elbow. The dislocation of the radial head may often be palpated. With any obvious forearm deformity, it is important to examine the elbow and wrist for injury also. The presence or absence of tenderness on palpation of the radial head should be noted.
5. Radiographs of the forearm, elbow, and wrist should be obtained. Always remember to include the joint above and below the site of injury. It is important to have a true lateral of the elbow along with the anteroposterior view. A line drawn through the long axis of the radius should pass through the center of the capitellum in all views. With radial head dislocation, this line does not intersect the center of the capitellum.
6. The ulnar fracture in Monteggia's injury is most often at the proximal to middle third of the ulna. Sometimes the fractureis not complete; there may be a greenstick fracture or even bowing of the ulna associated with the radial head dislocation. The radial head dislocation may be anterior, posterior, or lateral.
View another example: Lateral view.

AP view.

The lateral view shows a large anterior fat pad and a small posterior fat pad indicating a joint effusion. You may have to adjust the contrast and brightness controls on your monitor to appreciate this. There is a tiny cortical angle noted on the inferior margin of the radial head metaphysis where it crosses the ulna, indicating a subtle radial head fracture. The radius is NOT pointing directly at the capitellum. This indicates dislocation of the radial head. The AP view is more of an oblique view. It shows a fracture of the olecranon. The radial head metaphysis shows a sharper cortical angle, making the radial head fracture more obvious. This is a very subtle example of a Monteggia injury (ulna fracture with radial head dislocation). Although the radial head fracture is not necessarily part of the Monteggia injury, the same forces resulting in radial head dislocation probably caused the radial head fracture as well.
7. Do not splint or cast a Monteggia's injury and discharge from the ED. This requires an immediate orthopedic referral. The radial head dislocation must be reduced by an orthopedic surgeon as soon as possible. In most pediatric cases, a closed reduction under general anesthesia can be done. Sometimes open reduction of the radial head dislocation and internal fixation of the ulnar fracture are required. With early recognition and treatment, there is usually a good long-term result.
8. The posterior interosseous branch of the radial nerve is the most commonly injured nerve associated with Monteggia's injury. This nerve injury is usually self-limited and resolves. This nerve innervates the deep extensor muscles (extensor digitorum, the extensor digiti minimi, the extensor carpi unlaris, and the extensor indicis).
9. Complications of Monteggia's injury include recurrent dislocation of the radial head, persistent subluxation of the radial head, nerve injuries, and limitation of elbow range of motion.

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