*2.7. Autografts*

It was originally hypothesized that the best material for inducing axons to regenerate across nerve gaps would be a length of the autologous peripheral nerve [41]. The most commonly used donor nerves are the cutaneous saphenous, medial antebrachial cutaneous, and sural nerves [42–45].

The following sections discuss the e fficacy of sensory nerve grafts and other techniques in promoting axon regeneration and neurological recovery.

## **3. Sensory Nerve Grafts: Limitations**

#### *3.1. Loss of Sensory Nerve Function*

The primary drawback to using lengths of nerve as a graft is that their use requires sacrificing the function of that nerve. This creates a permanent neurological deficit [15,46,47].

#### *3.2. Incorrect Schwann Cell Phenotype*

Both sensory and motor nerve grafts have been tested for their efficacy in promoting axon regeneration and restoration of function. Motor nerve grafts induce significantly greater axon regeneration than sensory nerve grafts. This is because sensory and motor nerve Schwann cells express distinctly different phenotypes, and each best supports the regeneration of their specific axon phenotype [16,48]. Although motor nerve grafts are more effective than sensory nerve grafts in promoting axon regeneration across a nerve gap, they are not used because it is considered unethical to sacrifice a motor nerve function, when the loss of a pure sensory nerve has minimal impact on the patient.
