Image Quiz

An Unusual Dislocation of the Elbow (continued)

Answer: Combined posterior and convergent dislocations of the elbow.


Fig. 2-A
Fig. 2-B		 Figs. 2-A and 2-B Radiographs made after the closed reduction. Fig. 2-A Lateral radiograph showing that the radial head was not congruent with the capitellum. Fig. 2-B Anteroposterior and oblique radiographs showing a translocation of the radial head and ulna.

For larger view, click on image

Closed reduction of the proximal radioulnar joint was attempted, with the patient under general anesthesia, but was unsuccessful. A lateral approach between the extensor digitorum communis and the extensor carpi radialis longus and brevis was used to expose the joint. The radial head was found to be dislocated from the ulnar notch and was transposed to the medial side of the ulna. Reduction of the radial head was performed by placing a Hohmann retractor underneath it and supinating the forearm. This allowed the radial head to be levered over the coronoid and to fall back to its normal position. Examination of the radial head showed a shallow osteochondral defect involving 30% of the articular surface. The elbow was then taken through a limited range of motion, from full extension to approximately 100° of flexion, and the radioulnar joint was found to be unstable at 45°. A midsubstance disruption of the annular ligament was evident with an intact insertion. Additionally, the lateral collateral ligament was intact but visibly lax. When the latter was imbricated to the underlying soft tissues, radioulnar stability was obtained throughout a 100° range of flexion. On intraoperative examination, the interosseous membrane was determined to be intact. The soft tissues and skin were closed, and a long posterior splint was applied. Postoperative radiographs confirmed congruent reduction of the olecranon and trochlea with the restoration of the radiocapitellar joint (Figs. 3-A and 3-B).


Fig. 3-A
Fig. 3-B		 Figs. 3-A and 3-B Radiographs of the elbow made four weeks after the open reduction. Fig. 3-A Lateral radiograph showing that the radial head is congruent with the capitellum. Fig. 3-B Anteroposterior radiograph.

For larger view, click on image

The patient was managed with immobilization in the long arm posterior splint for three weeks. She was then managed with a hinged elbow brace with an extension block at 90° and was allowed to begin range-of-motion exercises. The patient was reassessed at two-week intervals, at which time the amount of extension in the brace was increased by 15° to 20°. The use of the brace was discontinued eight weeks after the date of the initial injury.

At six months after the initial injury, the range of motion of the elbow was from 15° to 130°. Pronation and supination were 65° and 50°, respectively. The patient had minimal pain with range of motion and was not limited in the activities of daily living. At the last visit, twenty-five months after the initial injury, the patient had painless range of motion from 10° to 130°, full supination and pronation, and no evidence of instability.

Discussion

We are aware of the cases of only ten patients who had convergent elbow dislocations, and all were confined to the pediatric population. El-Ghawabi described three adults who had elbow injuries that involved a fracture of the radial neck with medial displacement of the radial head, but only one of those patients had a concomitant posterior elbow dislocation and none had translocation of the radius and ulna.

Translocation of the radius and ulna may be easily overlooked if the radiographs are not carefully evaluated. A correct initial diagnosis was made in only three of the ten previously reported cases, with the delay in diagnosis ranging from several hours to five weeks. In one patient, the translocation was not recognized, even after open reduction and internal fixation of a coronoid fracture. The situation is further confounded by the relatively normal appearance of the elbow. This stands in contrast to divergent dislocation, in which there is usually gross deformity about the elbow.

When convergent dislocation is concomitant with a posterior elbow dislocation, radiographic evidence of radial shortening will persist, especially on the lateral radiographs made after the ulnohumeral reduction. Transposition of the humeral articulating surfaces for the radius and ulna may also be evident. The clinical manifestation is an inability to supinate the forearm. This finding should alert the clinician that something other than a simple posterior elbow dislocation might be present, and additional radiographs or a fluoroscopic examination may be beneficial.

The mechanism of injury has been described as a fall onto the hyperpronated hand with the elbow in full extension, producing an axial force on the proximal aspect of the radius. This is accompanied by anterior dislocation of the radial head. Axial loading may also induce a posterior dislocation of the ulna. This mechanism seems consistent with the findings in our patient who sustained a concomitant ipsilateral distal radial fracture. Most authors have concurred that this type of fall is the mechanism of injury, with the exception of Isbister, who believed the etiology to be iatrogenic. However, in the case of our patient, as well as those in other reports, prereduction radiographs clearly showed the transposition of the proximal radioulnar joint prior to reduction.

Associated injuries seen with convergent elbow dislocations are similar to those seen with acute elbow dislocations and have included documented fractures of the radial head (three patients), radial neck (three patients), or coronoid process (two patients). Ulnar nerve palsy has occurred in three patients, and in one of them it was iatrogenic in nature. All three cases of ulnar nerve palsy eventually resolved. Our patient had none of the above injuries, although the distal radial fracture attests to the large amount of energy that is required for this type of injury to occur. Finally, osteochondral injury, which was seen in our patient, is not uncommon in elbow dislocations.

In this limited number of cases, closed reduction was successful in only four patients and all four reductions were performed by one surgeon; six other instances of radioulnar translocations required open reduction. Only MacSween reported a successful closed reduction with the elbow flexed to 100° and the forearm fully supinated. If closed reduction fails, an open approach is needed to leverage the radial head into anatomic position. Given that ligamentous disruption occurs with this injury, primary repair of the torn or attenuated ligaments and/or capsule is generally required to achieve adequate radioulnar stabilization.

Complications of convergent elbow dislocations in children have included osteonecrosis of the radial head, iatrogenic ulnar nerve palsy, and mild heterotopic ossification, in one patient each. Each of these complications, with the exception of the heterotopic ossification, occurred in patients who had a delay in diagnosis.

In conclusion, convergent dislocation of the elbow is a rare injury that has previously been reported only in the pediatric population. The present report is the first, as far as we know, to describe such an injury in an adult. The failure to diagnose the translocation of the radius and ulna has been associated with a decreased range of motion and other complications. In all patients with such an injury, delayed intervention can be avoided by careful scrutiny of the radiographs combined with a thoughtful clinical examination.

Reference

1. Lippe CN, Williams DP. Combined posterior and convergent elbow dislocations in an adult. A case report and review of the literature. J Bone Joint Surg Am. 2005;87:1597-1600.