RADIAL NERVE PALSY
The radial nerve may be injured at the elbow, in the upper arm
or in the axilla.
Clinical
features
Low
lesions are usually
due to fractures or dislocations at the elbow, or to a local wound. Iatrogenic
lesions of the posterior interosseous nerve where it winds through the
supinator muscle are sometimes seen after operations on the proximal end of the
radius.
The patient complains of clumsiness
and, on testing, cannot extend the metacarpophalangeal joints of the hand. In
the thumb there is also weakness of extension and retroposition. Wrist
extension is preserved because the branch to the extensor carpi radialis longus
arises proximal to the elbow. High lesions occur with fractures of the
humerus or after prolonged tourniquet pressure. There is an obvious wrist drop,
due to weakness of the radial extensors of the wrist, as well as inability to
extend the metacarpophalangeal joints or elevate the thumb. Sensory loss is
limited to a small patch on the dorsum around the anatomical snuffbox. Very
high lesions may be caused by trauma or operations around the shoulder.
More often, though, they are due to chronic compression in the axilla; this is seen
in drink and drug addicts who fall into a stupor with the arm dangling over the
back of a chair (‘Saturday night palsy’) or in thin elderly patients using crutches
(‘crutch palsy’). In addition to weakness of the wrist and hand, the triceps is
paralysed and the triceps reflex is absent.
Treatment
Open injuries should be explored and the nerve repaired
or grafted as soon as possible.
Closed injuries are usually first or second degree lesions,
and function eventually returns. In patients with fractures of the humerus it
is important to examine for a radial nerve injury on admission, before treatment
and again after manipulation or internal fixation. If the palsy is present on
admission, one can afford to wait for 12 weeks to see if it starts to recover.
If it does not, then EMG should be performed; if this shows denervation
potentials and no active potentials
then a neurapraxia is excluded and the
nerve should be explored. The results,
even with delayed surgery and quite long grafts, can be gratifying as the
radial nerve has a straightforward motor function. If it is certain that there
was no nerve injury on admission, and the signs appear only after manipulation or
internal fixation, then the chances of an iatropathic injury are high and the
nerve should be explored and – if necessary – repaired or grafted without delay.
While recovery is awaited, the small joints of the hand must be put through a
full range of passive movements. The wrist is splinted in extension. ‘Lively’ hand
splints are avoided as they tend to hold the metacarpophalangeal joints in
extension with the proximal interphalangeal joints flexed and this will lead to
fixed contractures. If recovery does not occur, the disability can be
largely overcome by tendon transfers:
pronator teres to the short radial extensor of the wrist, flexor carpi radialis
to the long finger extensors and Palmaris longus to the long thumb abductor.
Reference:
·
Apley’s System
of Orthopaedics and Fractures
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