The sural nerve: sonographic anatomy, variability and relation to the small saphenous vein in the setting of endovenous thermal ablation

Background: Neurological complications are well documented in association with both surgical stripping or disconnection and thermal ablation of the small saphenous vein. The sural nerve (medial sural cutaneous nerve) is most vulnerable due to its close relationship to the small saphenous vein. Objective: This is a cross-sectional observational study of the sonographic anatomy of 115 Australian patients to determine the course of the sural nerve and its relationship to the small saphenous vein, and to identify its relevance in the thermal ablation of the small saphenous vein. Method: Sonographic mapping of the right sural nerve was performed with a Philips L12.5 and Sonosite 10.5 MHz ultrasound machine on 115 patients. The sural nerve was traced proximally from the level of the lateral malleolus to the popliteal fossa in order to measure its distance from the small saphenous vein at four reference points in the lower leg. Results: A total of 115 patients were studied (females 82, males 33). The sural nerve was identified in 100% of patients; 64 patients (55.7%) showed usual sural nerve anatomy, while 51 patients (44.3%) demonstrated a range of anatomical variations, including the sural nerve becoming epifascial at a higher point than usual. Conclusion: The sural nerve was identifiable on duplex ultrasound in 100% of cases. Classic anatomical relations and the perceived protection of the sural nerve conferred by the deep fascia of the upper calf are unreliable. Preoperative strategies can help to approach and protect the sural nerve in the endovenous ablation setting.