Posterolateral Rotatory Elbow Subluxation with Intra-Articular Entrapment of the Radial Nerve: A Case Report

Liu, George Su MD; Jupiter, Jesse B. MD

Journal of Bone & Joint Surgery - American Volume:
Case Reports
Author Information

1 Massachusetts General Hospital, 15 Parkman Street, GRB 6 (G.S.L.) and WACC 527 (J.B.J.), Boston, Massachusetts 02114. E-mail address for J.B. Jupiter:

Article Outline

Posterolateral rotatory elbow subluxation with associated intra-articular entrapment of the radial nerve is extremely uncommon. To our knowledge, only one previous report has described a similar clinical entity1. We describe the case of a patient who presented to us, four weeks after injury, with severe limitation of elbow motion, pain, and motor and sensory radial nerve palsy. Definitive treatment required surgical exploration and removal of the radial nerve from the radiocapitellar joint, which facilitated reduction of the radial head. The patient was informed that data concerning the case would be submitted for publication.

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Case Report

A thirty-seven-year-old right-hand-dominant woman presented to our clinic with a four-week history of pain in the left elbow, loss of sensation over the dorsum of the thumb and index finger, and an inability to extend the wrist and fingers.

Four weeks previously, the patient had fallen onto the outstretched arm while walking outdoors. She felt immediate pain in the left elbow and went to a local emergency room, where she was found to have altered sensation in the radial-nerve distribution in the hand as well as an inability to extend the wrist and fingers. Standard radiographs of the elbow demonstrated posterolateral rotatory elbow subluxation (Figs. 1-A and 1-B), and a manipulative reduction was performed. The limb was placed in an above-the-elbow splint, and the patient was instructed to seek orthopaedic consultation.

The patient did not seek follow-up evaluation as instructed. Three weeks after the injury, the patient presented to our emergency room because the pain, numbness, and weakness had not resolved. Standard anteroposterior and lateral radiographs of the left elbow revealed an anterior fat-pad sign and widening of the radiocapitellar joint that was suggestive of posterolateral rotatory instability2,3 (Figs. 2-A and 2-B). Closed reduction was not possible. Examination in our clinic one week later revealed swelling of the left elbow, with tenderness over the radial head. The patient had loss of sensation in the distribution of the superficial radial nerve. Assessment of motor function with use of the British Medical Research Council system revealed grade-0 (of 5) strength in the wrist, thumb, and digital extensors4. The active and passive ranges of motion of the elbow were from 30° to 95° of flexion. The patient could actively pronate the forearm to 45° but was unable to actively supinate the forearm. The arc of passive forearm supination was 45°. There was no wrist tenderness.

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The patient's medical history included fibromyalgia and discoid lupus. She had a smoking history of fifteen pack-years and used alcohol on a social basis. The patient was scheduled for surgical exploration of the radial nerve and open reduction of the radial head. Preoperative electromyography revealed a complete radial nerve palsy at the level of the elbow.

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With the patient under general anesthesia and with use of a sterile pneumatic tourniquet, the elbow was approached through an extended lateral incision. The radial nerve was identified proximal to the elbow in the interval between the brachialis and the brachioradialis. The nerve was found to be displaced, and it followed a posterolateral, instead of an anterior, course. As the radial nerve was followed distally, it was found to wind posteriorly around the lateral musculature and the lateral humeral condyle. It then entered the radiocapitellar joint through the torn posterior and lateral capsule (Fig. 3). A few branches of the nerve to the wrist extensors were observed to be avulsed from their muscular innervations. An osteotomy of the lateral epicondyle was performed to facilitate the exposure and to permit easy relocation of the radiocapitellar joint and radial nerve.

Within the radiocapitellar joint, the radial nerve was found to be encased in granulation tissue. Under 3.5-power loupe magnification, the nerve was mobilized and was replaced in its anatomic position. The granulation tissue was removed from the radiocapitellar joint, facilitating reduction of the radial head. The osteotomy site was then repaired with use of 24-gauge stainless-steel wire, which was passed through drill-holes in the lateral aspect of the distal part of the humerus and was woven through the origin of the lateral musculature. Anteroposterior and lateral radiographs of the elbow confirmed reduction of the radiocapitellar joint. Full passive elbow flexion and extension and forearm rotation were achieved without subluxation or recurrent dislocation.

Postoperatively, the limb was immobilized for ten days in a posterior splint with the elbow in 90° of flexion and the forearm in pronation. The wrist was held in 30° of extension, and the metacarpophalangeal joints were supported in 60° of flexion. Active motion of the proximal interphalangeal joints was permitted. No prophylaxis was used to offset heterotopic ossification. Active and active-assisted range of motion of the elbow began at ten days, with the forearm kept in neutral rotation.

Within two weeks after surgery, the patient began to experience hypersensitivity in the distribution of the superficial radial nerve. By fourteen weeks postoperatively, some return of wrist and digital extensor motor function was observed.

By eighteen months after surgery, the patient had returned to her job as a filing clerk. Standard radiographs of the elbow demonstrated an anatomically aligned joint. By two years, the patient had regained full strength in the wrist, thumb, and digital extensors. Grip strength was 32 kg, compared with 30 kg for the contralateral hand. The range of motion of the left elbow, including flexion, extension, pronation, and supination, was full and equal to that of the contralateral upper extremity. The elbow was stable to varus and valgus stress in all positions. Sensation to light touch on the dorsum of the first web space was only slightly diminished compared with that in the contralateral hand, but the patient could distinguish between blunt and sharp stimuli.

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Intra-articular entrapment of neurovascular structures in association with dislocation of the elbow is uncommon. It has been described primarily in the pediatric literature, which has included reports of intra-articular entrapment of the median nerve, brachial artery, or radial artery in the humeroulnar joint5-13. In children, avulsion of the medial epicondyle can create an opening that permits posterior displacement of the median nerve or brachial artery14.

In our patient it appears that as the radial head was displaced posteriorly, the radial nerve was displaced laterally and posteriorly around the lateral epicondyle. Although the lateral musculature arising from the epicondyle was intact, the radial nerve was able to enter the radiocapitellar joint through the disrupted posterior capsule. Similar clinical and radiographic findings have been reported in cases of neurovascular entrapment in the humeroulnar joint7,8,12,13, and widening of the joint space has been seen radiographically in cases of intra-articular obstruction after reduction of a humeroulnar dislocation5,11.

It is of interest to note that despite the avulsion of branches of the radial nerve to the radial wrist extensor muscles, the patient had full return of active wrist extension. This finding suggests that not all of the branches from the radial nerve were avulsed and/or that branches to one extensor were preserved. While the most commonly observed pattern of innervation from the radial nerve at the elbow, from proximal to distal, is to the brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, and supinator15, anatomic studies have shown that branches to the extensor carpi radialis brevis can originate from the bifurcation of the posterior interosseous and superficial sensory nerves, with several variations in the distance from the point of origin to the point of insertion in the extensor carpi radialis brevis16,17.

We chose not to use adjuvant radiotherapy or anti-inflammatory agents to offset the potential for postoperative heterotopic ossification. It has been our custom to reserve these treatments for patients with concomitant closed head trauma or those in whom excision is performed because of established heterotopic ossification18.

Despite a four-week delay in treatment, our patient was able to regain full range of motion following operative reduction and early functional rehabilitation. Previous studies have supported early elbow motion following elbow dislocation if the elbow is clinically stable19-23. It is noteworthy that, in cases of isolated posterior radial head dislocation, instability after reduction is extremely uncommon24-30.

While intra-articular entrapment of the radial nerve in the radiocapitellar joint is rare, an awareness of this phenomenon is useful when relevant clinical and radiographic signs are present. As most nerve palsies associated with elbow dislocations are due to traction lesions, it is customary to follow these palsies expectantly for a defined period of time. Widening of the radiocapitellar space after manipulative reduction in the presence of a radial nerve palsy could well be due to nerve entrapment. Prompt surgical treatment can result in the return of nerve function and restoration of elbow stability and mobility.

The authors did not receive grants or outside funding in support of their research or preparation of this manuscript. They did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

Investigation performed at Massachusetts General Hospital, Boston, Massachusetts

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