Nerve and tendon lacerations (i.e. deep cuts) of the hand are a relatively common injury. Treating these injuries appropriately is important to maintain long-term sensation and motor functions of the injured hand.
There are 3 major nerves in the hand: the radial nerve, the ulnar nerve, and the median nerve.
The symptoms of a nerve laceration are highly variable, particularly in the hand.
Note that after nerve laceration, the distal portion (end towards the fingers) begins to degenerate, as part of a process called Wallerian degeneration. When this happens, the nerve ends may retract from each other, particularly in cases of a complete laceration. Eventually, scar tissue forms at both ends.
In motor nerves and the motor endplate, the attachment of the nerve to the muscle may also degenerate after a period of time.
All of these factors can work against the complete return of nerve function after repair.
The nature of a laceration is important for us to understand when making a treatment plan.
Treatment of nerve lacerations in the hand requires a detailed, complete assessment of nerve function and hand function.
These studies (and others if needed), as well as a very detailed hand examination, help to provide a complete picture of the functional loss caused by the hand nerve laceration.
When treating patients, we must also consider the level of their original injury. Lacerations that injure tiny small nerves and lacerations in mixed nerves (those with both sensory and motor nerve branches) are more difficult to treat.
Our assessment is ultimately coupled with the decision on how much functional loss can be well tolerated in order to create a plan to restore function.
Early treatment of lacerations will consist of:
Early treatment can be accomplished immediately after an injury or approximately 2 weeks later. Sometimes, prior to coming to us the wounds have been cleaned and the skin repaired by the emergency room. The results in such cases are approximately the same.
In surgery for early treatment, an operating microscope or loupe magnification is used to trim the nerve ends carefully and repair the nerve with several sutures that are smaller than a human hair. If a large segment of nerve has been damaged and needs to be resected or is missing, a nerve graft (section of matching nerve taken from another donor area) may be used to bridge the gap between the nerve ends.
A newer surgical technique involves using a neural tube (a small tube of collagen) that surrounds both ends of the nerve repair and allows the nerve to heal down the tube, bridging the gap.
Both surgical techniques can allow function to return when there has been a missing segment of nerve or damaged nerve. The results of the newer procedure, however, are not as good as a direct primary repair of the nerve ends.
For delayed repairs of a nerve laceration, the ends of both nerves must be found in the scar tissue of an already healed wound and freed up; then the ends of the nerve must be trimmed back to the viable section nerve.
Each nerve laceration case and patient requirements are individual and unique, requiring a different approach.
Nerve repair surgery is usually performed under general anesthesia to avoid any patient motion. The patient is often placed in a protective splint post-op to avoid any tension on the nerve repair.
The actual nerve repair site takes 4 to 6 weeks to heal and avoid tearing. Mobilization exercises of the hand are then begun to regain motion. Return to work and normal activities are usually allowed after the nerve repair site is healed and function and strength are within acceptable limits.
Approximately 2 weeks after nerve repair, the nerve starts the slow process of regeneration at about the rate of an inch a month. This process may take place more quickly in younger healthier patients. Regeneration is also faster in primary nerve repairs than with nerve grafts.
It may be months before the return of sensation is noted. Return of muscle function often takes longer. Ultimately, it is important to remember that despite our best efforts and advanced microsurgical technique, all nerve function does not return in every patient.