After a nerve is cut, there are a series of biological events which take place. Locally, the distal nerve segment (and a little of the proximal segment) undergoes Wallerian degeneration, leaving behind empty nerve sheaths. The proximal nerve end would then be primed to regenerate and attempt to reconnect with the other cut end. However this is not possible without surgery if the nerve has been completely severed.
Without restoring the neural continuity in time, for a motor nerve the motor endplates would degenerate and the muscle that it innervates would begin to decrease in volume (muscle wasting or atrophy). Centrally at the spinal cord, the neuronal cells undergo a process akin to programmed cell death (apoptopsis) and the cortical area in the brain (homunculus) that is normally occupied by the injured nerve would be lost due to the lack of neural signals. In short, a cut nerve not only has an effect locally at the wound but also has a negative impact on the brain, the spinal cord and the end-organ!
If a nerve is cut, repair it early.
There are some prerequisites to performing a primary nerve repair in order to achieve the optimum outcome:
- Skeletal stability
- Healthy tissue bed
- Healthy nerve ends
- No undue tension
- Adequate soft tissue coverage
A repair may be achieved using microsutures or fibrinogen glue or a combination of the two. There are two basic techniques of nerve repair:
- Epineurial repair – A relatively simpler technique and the alignment is less exact but there is less trauma to the nerve ends.
- Group fascicular repair – In theory this confers better alignment but it is at the expense of greater scarring and longer operating time.
The functional results of group fascicular repair have not been shown to be more superior to that of epineurial repair.
The functional outcomes of a nerve repair are influenced by a number of factors:
|1. Patient factor
|2. Injury factors
||- Level of injury (distal versus proximal)
- Type of nerve (pure sensory/motor versus mixed)
- Condition of nerve ends
|3. Surgical factors
||- Delay to repair
- Length of gap
- Surgeon’s skills
Despite the many advances made in microsurgical techniques and instrumentation, the functional outcome of a repaired nerve will never be exactly the same as before the injury. Injury prevention is definitely better than cure!