Monteggia fracture dislocations

You are called to the emergency department to evaluate the right arm of a 26-year-old female who fell approximately 15 ft off of an apartment balcony. She appears to have a deformity about the proximal right forearm and is markedly swollen. She also has several rib and facial fractures but is alert and oriented and does not have any open wounds, and she has no neurovascular deficits on examination. The lateral radiograph on initial presentation is shown in Figure 6–23.

 

 

 

Figure 6–23

What treatment plan will provide this patient the best chance for a successful outcome?

1. Open reduction of the radial head dislocation with K-wire fixation of the proximal radioulnar joint and long arm immobilization with the forearm in supination

2. Closed reduction of the ulna fracture and radial head dislocation with long arm casting for 4 to 6 weeks

3. ORIF of the ulna fracture with closed reduction of the radial head dislocation and brief immobilization

4. ORIF of the ulna and closed reduction of the radial head dislocation with long arm casting for 4 to 6 weeks

Discussion

The correct answer is (C). The depicted injury is an ulna fracture with associated dislocation of the proximal radius, known as a Monteggia injury. Whereas in children the treatment is most often closed reduction with long arm cast immobilization, in adults these injuries are almost exclusively treated surgically. The mainstay of surgical treatment is anatomic reduction and fixation of the ulna, which usually leads to reduction of the proximal radius. “D” is an incorrect choice here because immobilizing the adult elbow for a prolonged period leads to increased loss of motion, and in this injury pattern, is unnecessary after ORIF of the ulna fracture. The Bado classification is used to classify Monteggia fractures. In Type I, the radius is dislocated anterior, in Type II, the dislocation is posterior, in Type III, the dislocation is lateral, and in Type IV, there is a fracture of both the radius and ulna shaft with proximal radius dislocation.

After anatomic reduction and fixation of the ulna fracture, the radial head remains unable to be reduced by closed means.

What is most likely to be interposed and preventing reduction?

1. The annular ligament

2. The lateral ulnar collateral ligament

3. An osteochondral fragment

4. Anterior joint capsule

5. The posterior interosseous nerve (PIN)

 

Discussion

The correct answer is (A). Anatomic reduction of the ulna must first be confirmed

as a malreduction, can prevent reduction of the radial head. If the ulna is anatomically reduced, and the radial head remains dislocated, the annular ligament can in some cases remain intact and prevent reduction of the radial head. In this situation, the annular ligament should be divided and subsequently repaired after reduction of the radiocapitellar joint. In more rare circumstances, the PIN can become interposed and prevent anatomic reduction as well, although this is less common than the annular ligament.

Which of the following structures do not play a significant role in the stability of the proximal radioulnar joint (PRUJ)?

1. The annular ligament

2. The radial fossa of the ulna

3. The LCL complex

4. The MCL complex

5. The interosseous membrane (IOM)

 

Discussion

The correct answer is (D). The PRUJ has relatively little bony contribution to its stability, with only approximately 18% of the radial head circumference articulating with the radial fossa of the ulna at a given time. The annular ligament and LCL complex contribute to the stability of the PRUJ, but the central band of the IOM provides the most significant longitudinal stability when sectioned in anatomic studies. The critical importance of the IOM in maintaining radioulnar alignment in the setting of a radial head fracture is exemplified in an Essex-Lopresti injury.

 

Objectives: Did you learn...?

 

 

The Bado classification for Monteggia fracture dislocations? Operative versus nonoperative management?

 

Anatomy of the proximal radioulnar joint?