Radial Nerve Injury

10.1055/b-0034-97735

John R. Barbour & Ida K. Fox

Right upper extremity: Loss of wrist, finger, and thumb extension (radial nerve palsy).
Injury likely at the midhumeral level, given the history of previous trauma at that site.

Critical points
- Open versus closed mechanism of nerve injury will dictate initial treatment.
  - In a closed injury pattern, watchful waiting is most appropriate.
  - An open injury points to nerve transection, and direct exploration is usually indicated.
- Time since injury will further determine available treatment options (at 1 to 2 years after injury, muscle cannot be reinnervated).
Associated pain and/or stiffness.
Medical comorbidities.

Evaluate for any scars suggestive of open injury or previous surgery.
Evaluate for stiffness, edema, hypersensitivity, and other signs of complex regional pain syndrome CRPS.
Evaluate radial nerve motor function proximally to distally (i.e., check ability to extend elbow, wrist, fingers at the metacarpophalangeal joint, and thumb to determine level of injury).
Evaluate the other upper extremity nerves and muscles that you might use as donor material for subsequent nerve or tendon transfers.
Complete sensory examination, including two-point discrimination.
Evaluate for Tinel sign: This may help in identifying the site and level of injury.

X-rays of the fracture helpful in confirming level of injury.
For a closed injury pattern, electrodiagnostic tests, including electromyography (EMG) at 3 months, may be helpful in ascertaining nerve recovery.
- Fibrillations: Indicate some motor injury.
- Motor unit potentials (MUPs): Indicate recovery.

Based on type of nerve injury

Classification of nerve injury (Table 45.1).

Classification of nerve injury
Seddon	Sunderland	Fibrillations	Motor unit potentials (MUPs)	Improvement without intervention
Neurapraxia	I	–		+
Axonotmesis	II	+	+	+
	III	+	+	+/−
	IV	+	−	−
Neurotmesis	V	+	−	−
	VI	+	Depends on injury	Depends on injury

In general, all patients with nerve dysfunction will benefit from physical therapy to assist with maintaining passive range of motion as well as manage any edema, pain, or other problems associated with the inciting injury.
A wrist cock-up splint is particularly useful for placing the hand in a position of function so that some use can be made while the patient awaits surgery and recovery.
Any associated pain syndromes must be aggressively managed; this may require medications, such as gabapentin (Neurontin; Pfizer, New York, NY).

Require nerve exploration because one must assume that there may be a nerve transection.
Open humeral fractures have radial nerve laceration in 60% of cases.
- Primary (≤ 24 hours), delayed primary (≤ 1 week), or secondary (> 1 week) repair is reasonable, depending on the mechanism of injury.
- If there is a significant crush component, delayed repair will allow the injured nerve to demarcate so that so that the appropriate length of damaged nerve may be trimmed away.
Repair directly or repair with interposed nerve graft is reasonable.
In the case of a relatively subacute presentation and/or proximal nerve injury, nerve transfer procedures are also a reasonable option.
Distal tendon transfers are reasonable, as well.