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.
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.
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.
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.