Anatomical variations in the relationship between the sciatic nerve and the piriformis muscle: clinical implications

OBJECTIVES: This study aims to contribute additional comparative anatomical and morphometric data to identify anatomical variations of the sciatic nerve (SN) and its relationship with the piriformis muscle (PM), clarify sex-related differences, and attempt to propose anatomical features relevant to understanding piriformis muscle syndrome. METHODS: Dissection of the deep gluteal region was performed on 80 specimens from 40 donors of both sexes. The frequency of SN anatomical variations in relation to the PM was recorded according to Beaton and Anson’s classification and analyzed by sex. Various morphometric measurements were also taken and compared according to sex and anatomical variations. RESULTS: Anatomical variations of the SN (types B, C, and D) were observed in 19.7% of specimens, with no significant sex-related difference in prevalence. The distances between the posterior superior iliac spine and the ischial tuberosity, the posterior superior iliac spine and the upper edge of the greater trochanter, the upper edge of the greater trochanter and the ischial tuberosity, the lateral edge of the SN and the upper edge of the greater trochanter, and the length of the lower limb were statistically greater in male specimens. Female specimens had a statistically greater width of the infra-piriform foramen. The distance between the SN and the greater sciatic notch was statistically larger in type A than in type B variants. CONCLUSION: Variations in the anatomical relationship between the SN and PM are not unusual and should be considered during medical procedures. Morphometric assessment may inform future research on piriformis muscle syndrome management.