[Anatomical study on restoration of the sensation of distal based sural island flap]

To investigate the anatomic foundation of using main branch of posterior femoral nerve to restore the sensation function of distal based sural island flap.

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 branches with diameter more than 0.1 mm were dissected and accounted during observation. The length and diameter of the nerves were measured.

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 were classified into 3 types according to their distribution in lower legs: type I (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 ordinrary 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 distance between the end of these branches and small saphenous vein was 0.8 +/- 0.4 mm.

66.6% of human main branch of posterior femoral 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 foot during operation.