Length characteristics of C₇ spinal nerve, middle trunk, and its anterior division

BACKGROUND: Contralateral transfer of donor nerves in cases of brachial plexus injury requires a detailed anatomical understanding of the C₇ spinal nerve. AIM: This study aimed to identify distinctive length characteristics of the C₇ spinal nerve, middle trunk, and its anterior division before and after epineurium removal. MATERIAL AND METHODS: To identify significant differences, the lengths of the C₇ spinal nerve, middle trunk, and its anterior division were measured twice in the anterior projection, before and after epineurium removal, in 121 brachial plexus specimens from male and female cadavers aged 40 to 97 years. Minimum and maximum values, medians, and quartiles (Q1; Q3) were recorded in the database. Statistical significance of differences in absolute nerve lengths and in the proportion of brachial plexus specimens with measured changes after epineurium removal was determined using the Mann–Whitney U test and Pearson’s χ2 test. RESULTS: The median lengths before epineurium removal were as follows: C₇ spinal nerve, 25 (20; 30) mm; middle trunk, 22 (17; 28) mm; anterior division, 20 (15; 26.5) mm. After epineurium removal, the respective values were 28 (25; 32) mm, 20 (15; 27) mm, and 25.5 (20; 37) mm. The total length of the C₇ spinal nerve, middle trunk, and its anterior division ranged from 30 to 111 mm before epineurium removal (median: 71 [63; 78] mm), and from 30 to 146 mm after removal (median: 75 [66; 85] mm). After epineurium removal, the total length of the C₇ spinal nerve, middle trunk, and its anterior division remained unchanged in only 3.3% of cases, decreased by 1–35 mm in 15.7%, and increased by 1–72 mm in 81%. Lengths exceeding 100 mm were found in 1.6% of specimens before and in 11.6% after epineurium removal. CONCLUSION: In 81% of cases, removal of the epineurium resulted in an increased total length of the C₇ spinal nerve, middle trunk, and its anterior division, which may reduce the distance required for contralateral nerve transfer by up to 72 mm.