5.1. Macroscopical Analysis

Gross evaluation is the first fundamental step to macroscopically grade scar tissue; it aims to assess the enrolment of the surrounding tissues (including skin, muscles, and deep tissues) in the compression of the nerve and the collaboration with the newborn perineural scar tissue.

Different classifications have been proposed by different authors to evaluate the degree of scar formation. The most used and complete classification is the numeric grade scheme defined by Petersen [27]. This classification allows us to evaluate closure of skin and muscle fascia (Grade 1: skin or muscle fascia entirely closed; Grade 2: skin or muscle fascia partially open; Grade 3: skin or muscle fascia completely open) and to evaluate nerve adherence (Grade 1: no dissection or mild blunt dissection; Grade 2: some vigorous blunt dissection required; Grade 3: sharp dissection required). Another adopted grading scheme is the 4-point qualitative scale that evaluates the perineural adhesions and type of dissection required to achieve complete neurolysis, as follows: absent or thin adhesions—delicate blunt (score 0); mild adhesion—vigorous blunt (score 1); moderate adhesion—delicate sharp (score 2); severe adhesion—difficult sharp (score 3) [13,14,23,28].

Abe [17] proposed a classification of nerve adhesion based on Fontana’s band (an optical manifestation of axonal undulations characteristic of peripheral nerves). They classify nerve adhesion as Group I (nonadhesion group) when the bands appear and Group II if they are not visible. Additionally, Group II is divided into Group IIa when a thickening of the epineurium and perineurium is observed (but not endoneurial fibrosis) and Group IIb when endoneurial fibrosis is observed.

Finally, some authors have reported the presence or absence and qualitative observations of scar tissue around the nerve without grading it.