Nerve injuries of the hand

Nerve injuries are classified according to severity. From least to most severe they’re neuropraxia (focal demyelination), axonotmesis (axon cut), and neurotmesis (nerve cut). Tinel sign may be positive. Radial nerve palsy causes drop hand, while ulnar nerve palsy causes claw hand. Diagnosis involves neurological examination, EMG, and ENG.

Etiology

Nerve injuries of the hand may be primary or secondary:

Primary
- Trauma to nerve
- Trauma to nearby bone/joint
Secondary
- Infection
- Scar
- Callus
- Vascular complications

Classification

We can classify nerve injuries according to their severity. From least to most severe:

Neuropraxia
- Minor contusion/compression of nerve
- Focal demyelination
- Complete recovery expected in days or weeks
Axonotmesis
- Crush or stretch injury of nerve
- Axon is cut but endoneurium and perineurium intact
- Recovery expected in months or years
Neurotmesis
- Sharp, traction, or percussion injury of nerve
- Nerve is completely cut
- Recovery not expected without surgery

Clinical features

Typical symptoms of nerve injuries include decreased sensation and weakness or paralysis in the area and muscles supplied. Tinel sign may also be positive, which involves a tingling sensation when tapping on the nerve.

Radial nerve palsy causes a drop hand, where the hand cannot be dorsiflexed. Sensory symptoms on dorsal arm and forearm.

Ulnar nerve palsy causes a claw hand, where the 4th and 5th fingers are flexed but the others extended. Sensory symptoms on palmar 1/3 of the hand, including the 5th digit and half of the 4th digit, as well as the medial half of the dorsal hand.

Median nerve palsy causes sensory symptoms on the lateral 2/3 of the palm of the hand, including half of the 4th digit, and digits 1 – 3. Motor symptoms depend on the level of the lesion.

Diagnosis and evaluation

Examination of nerve injuries involves physical examination of sensation and muscle strength, as well as objective tests like electromyography and nerve conduction studies (electroneurography).

Management

See nerve repair.

Surgical nerve repair

After traumatic nerve injury, for example of the hand, surgical nerve repair is often indicated. However, immediate repair is not always appropriate; in many cases, delaying the repair a few weeks or months may be better. However, nerve repair should not be delayed more than six months, as beyond that time irreversible changes occur.

Surgical nerve repair is indicated for neurotmesis and visibly damaged nerves. If the transection is sharp, immediate nerve repair is performed. If the transection is blunt, nerve repair should be delayed. If the nerve ends cannot be brought together without tension, a nerve graft should be used (from sural nerve).

Indications

Conservative treatment is indicated for:

Nerve injuries with neurapraxia or axonotmesis

Delayed repair is indicated for:

Nerve injuries with neurotmesis
Open injuries with blunt transection

Immediate repair is indicated for:

Open injuries with sharp (clean) transection

Grafts

If the gap between the nerve ends is large so that they cannot be brought together without tension, a nerve autograft or allograft should be used. Graft may be from the sural or antebrachial cutaneous nerves. If the ends can be brought together without tension graft is not necessary. However, it’s important to avoid tension on the nerve.