Furthermore, functional outcomes repairing different nerves in comparable circumstances are not always the same. Numerous studies have been published describing better results after the repair of the radial nerve than the median or ulnar nerves; there also is a better prognosis repairing the tibial versus peroneal nerve [11, 14].

To put treatment results in proper perspective, it is important to document these aforementioned factors. This is especially important for interpreting and evaluating the results of a specific treatment and, thereby, optimizing treatment strategies.

The degree of sensory and motor recovery is the criterion most commonly used to evaluate the results of nerve repair. Sensory recovery is not a reliable sign of regeneration, however, mainly because of its late appearance and difficulties with its objective evaluation. However, it is important after the repair of particular nerves like the median, ulnar and tibial nerve, as these provide protective sensation. It is less important as an outcome following the repair of nerves like the radial, axillary, musculocutaneous, femoral and fibular nerve.

On the other hand, although motor recovery is also late, it is a reliable sign of successful regeneration. It takes between 2 and 3 years to achieve maximum motor recovery, versus 5–7 years for maximum sensory restoration.

In general terms, the follow-up of any patient submitted to a peripheral nerve reconstructive surgery should be every 2 or 3 months. Clinical evaluation – including progression of Tinel’s sign – and serial neurophysiological studies can help determine early recoveries. The regular endpoint of follow-up is around 3 years for motor results and around five for sensory recovery. At that time, it is presumed that the maximum recovery point will be reached. Of course it is not possible to generalize these time spans for every patient: depending on the time from trauma to surgery, the distance from the injury site to the target muscles/skin, the type of reconstruction and so on, the end of follow-up variates from patient to patient.

One important concept to keep in mind when analysing the results of nerve repair is that of ‘useful recovery’, which entails the functional impact of recovery. The definition of ‘useful’ is variable and depends on the nerve involved. For example, useful sensory recovery for the tibial nerve means recovery of superficial pain and some tactile sensation (≥S2). However, for the median or ulnar nerve, it is also imperative to recover some two-point discrimination.

Similarly, useful motor recovery (≥M3) after peroneal nerve repair involves plantar dorsiflexion to 90°, since this is enough for the patient to stop using a foot brace [19].

A variety of scales and questionnaires have been developed and published to objectify these results. They may be categorized according to the function they evaluate: motor, sensory, pain or global.