Ultrasound-guided medial approach to the sciatic nerve in dogs: a cadaveric study

OBJECTIVE: To describe a novel ultrasound-guided medial approach to the sciatic nerve in canine cadavers and to compare its feasibility and injectate distribution with the conventional lateral approach. STUDY DESIGN: Prospective, randomized, cadaveric study. ANIMALS: A total of seven adult canine cadavers (14 pelvic limbs). METHODS: mixture of 2% lidocaine and iobitridol was injected per site. Total procedural time (time to identify the nerve and needling time) and skin-to-nerve distance were recorded. Distribution of the injectate, nerve coverage, and contrast spread length were assessed via computed tomography (CT). Student's paired t-test, Wilcoxon matched pairs test and Fisher's exact test were used for statistical analysis (p < 0.05). RESULTS: Ultrasound-guided identification and injection around the sciatic nerve were successful in all cadavers for both approaches, with real-time ultrasonography demonstrating perineural spread of the injectate. The medial approach required significantly longer total procedural time (95.5 ± 43.6 seconds) than the lateral approach (64.1 ± 23.7 seconds) (p = 0.03). Skin-to-nerve distances were similar across groups. CT confirmed correct perineural distribution of the injectate in every case, showing comparable circumferential nerve coverage and contrast spread between approaches. CONCLUSIONS AND CLINICAL RELEVANCE: The ultrasound-guided medial approach to the sciatic nerve is feasible in canine cadavers and provides an injectate distribution around the paraneural sheath like that achieved with the lateral technique. While the medial approach took longer to perform initially, this may reflect a learning curve that may improve with practice. The findings suggest the medial approach could offer a viable alternative for sciatic nerve block in dogs, particularly when lateral access is contraindicated.