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ANATOMICAL STUDY ON RESTORATION OF THE SENSATION OF DISTAL BASED SURAL ISLAND FLAP

Objective To investigate the anatomic foundation of using main branch of posterior femoral nerve to restore the sensation function of distal basedsural island flap. Methods Thirty cases of adult human cadaver legs fixed by 4%formaldehyde were used. Anatomical investigation of the posterior femoral nerves of lower legs was conducted under surgical microscope to observe their distribution, branches and their relationship with small saphenous vein. Nerve brancheswith diameter more than 0.1 mm were dissected and accounted during observation.The length and diameter of the nerves were measured. Results The main branch of posterior femoral nerve ran downwards from popliteal fossa within superficial fascia along with small saphenous vein. 70% of the main branch of the posterior femoral nerves lay medially to small saphenous vein, and 30% laterally. They wereclassified into 3 types according to their distribution in lower legs: typeⅠ (33.3%) innervated the upper 1/4 region of lower leg (region Ⅰ), type Ⅱ (43.3%) had branches in upper 1/2 region (region Ⅰ and Ⅱ), and type Ⅲ (23.3%) distributed over the upper 3/4 region (region Ⅰ, Ⅱ and Ⅲ). In type Ⅱ, the diameter of the main branches of posterior femoral nerves in the middle of popliteal tossa was 10±04 mm and innervated the posterior upper-middle region (which was the ordirary donor region of distal based sural island flaps) of lower legs with 2.0±0.8 branches, whose diameter was 0.3±0.2 mm and length was 3.5±2.7 mm. The distance between the end of these branches and small saphenous vein was 0.8±0.6 mm. In type Ⅲ, their diameter was 1.2±0.3 mm and innervated the posterior upper-middle region of lower legs with 3.7±1.7 branches, whose diameter was 0.4±0.1 mm and length was 3.7±2.6 mm. The distancebetween the end of these branches and small saphenous vein was 0.8±0.4 mm. Conclusion 66.6% of human main branch of posteriorfemoral nerves (type Ⅱ and type Ⅲ) can be used to restore the sensation of distal based sural island flap through anastomosis with sensor nerve stump of footduring operation.