Anatomy of the sural nerve in the posterolateral approach to the ankle: a cadaveric study

Y. Ghani, A.A. Najefi, Y. Aljabi, K. Vemulapalli

Background: Sural nerve injury may occur during the posterolateral approach to the ankle. The aim of this study was to map the sural nerve location in a posterolateral ankle approach in cadaveric specimens and allow surgeons to be aware of the anatomy and variations, thereby reducing the risk of sural nerve injuries.

Methods: A posterolateral approach was used in 28 cadaver legs with the incision made half-way between the medial border of the fibula and the lateral border of Achilles tendon, extending proximally from the tip of the lateral malleolus. The sural nerve was identified and the distance from the distal tip of the incision to where it crossed the incision proximally was measured.

Results: Out of the 28 specimens, there were 2 specimens in which the sural nerve did not cross the incision. Therefore, for the distance calculations we analysed the remaining 26 specimens. The mean distance was 3.4 ± 1.2cm. Twenty-two cases (76%) crossed between 2.7cm and 4.5cm. In 16 patients (55%), the distance from the lowest part of the incision to the nerve was 3.1-4cm. There were 3 cases between 0.1-1cm, and 1 between 6.1-7cm. Three cases were between 2.1-3.0cm, and 3 cases were between 4.1-5.0cm. Measurements between all three authors demonstrated excellent intra- and inter-observer reliability (intraclass correlation coefficient 0.80 and 0.78 respectively; Pearson correlation 0.80 and 0.88 respectively (p<0.001).

Conclusion: We have demonstrated that the sural nerve crossed the posterolateral incision between 2.7cm and 4.5cm proximal to the tip of the fibula in 76% of cases. However, there remains individual anatomical variation, and we would recommend that care should be taken to look for the nerve closer to the achilles tendon proximally and nearer the fibula distally. We hope that this information can help surgeons plan their approach and minimise iatrogenic injury to the sural nerve.