Anatomical Variations of Sural Nerve and its Clinical Implications

Introduction and Background: Sural nerve can be used for diagnostic purposes like nerve conduction velocity study and for nerve biopsy for various neuromuscular disorders. It is also widely used for electrophysiological studies. Knowledge about the course of the sural nerve and variations in its course would be hugely helpful in carrying out the aforementioned studies. This knowledge will also be helpful while performing procedures like autologous peripheral nerve grafting and nerve biopsy. Aims and Objectives: The aim of this study is to study the variations of sural nerve formation, its course in the leg and its relations with Tendo-Calcaneus, short saphenous vein and lateral malleolus for its clinical application. Methodology: This was a descriptive study done in the Institute of Anatomy, Madras Medical College, Chennai, Tamilnadu, India. The study was conducted by following the guidelines of Cunningham’s manual. This study included 50 lower limb specimens from 25 cadavers fixed in 10% formalin. Both male and female cadavers were included in the study. The data was collected by dissection method by using dissection instruments and parameters (measurements) were obtained by using measuring tape and Vernier’s calliper. Results: The mean length of leg measured from flexor crease to heel in our study was 43.96 cm. The most common type of sural nerve formation is Type-A. In males, Type-A sural nerve formation was most commonly located at lower 1/3rd of leg with 63.7% specimens (n=7) on right side. In females, Type-A sural nerve formation was most commonly located at lower 1/3rd of leg with 71.4% specimens (n=5) on right side and 75% specimens (n=6) on left side. The symmetricity of sural nerve formation between right and left lower limbs was noted in 11 male cadavers (78.6%) and 6 female cadavers (n=54.5%). Sural nerve formation was asymmetric in 3 male (21.4%) and 5 female (45.5%) cadavers. Sural nerve pierced deep fascia most commonly at lower 1/3rd of leg as noted in 50% of specimens. The mean distance between the site of sural nerve piercing deep fascia and lower border of lateral malleolus was 18.07 cm. The mean length of sural nerve measured from its formation to lateral malleolus was 31.54 cm. the mean distance between sural nerve and posterior border of lateral malleolus at its midpoint was 0.95 cm. The mean distance between the site of sural nerve crossing lateral border of Tendocalcaneus and lower border of lateral malleolus was 4.82 cm. The mean distances noted at 5cm reference point was 0.17 cm lateral to Tendo-calcaneus. At 7cm and 10cm reference points, sural nerve was medial to lateral border of Tendo-calcaneus with mean distances -1.5cm and -3.92 cm respectively