Anatomy of the motor nerve to the gracilis muscle and its implications in a one-stage microneurovascular gracilis transfer for facial reanimation.

BACKGROUND

The present study was conducted to investigate the anatomy of the motor nerve to the gracilis muscle (MNG) to provide the anatomical basis for harvesting a one-stage gracilis transfer with a long nerve for re-animation of the paralysed face.

METHODS

An anatomical study was performed on 24 lower-limb specimens (from the pelvis down to the knee) from 12 embalmed cadavers. The MNG was dissected from the surface of the muscle to the obturator foramen. Two anatomical regions were defined in the course of the nerve. The first region includes the part of the nerve that can easily be reached through a standard incision in the medial aspect of the thigh, that is, from the surface of the muscle to the posterior border of the adductor brevis muscle and the second region from there to the obturator foramen. Measurements of both anatomical regions and the maximum length of the nerve were taken with a calliper. The anatomical relations of the nerve were also noted and photo-documented.

RESULTS

The median maximum length of the MNG from the surface of gracilis to the posterior border of adductor brevis ('first anatomical region') was 7.7 cm (Range 6.3-10.5 cm); from there to the obturator foramen ('second anatomical region') the length was 3.7 cm (Range 2-6 cm), giving a median length of dissection of the nerve as 11.5 cm (Range 9.9-13.6 cm). Intraneural dissection of the MNG has to be performed proximally in the course of the nerve (the part corresponding to the second anatomical region), just where it runs inside the fascia over the obturator externus muscle.

CONCLUSIONS

Over 10-cm length of the MNG can be obtained when dissected along the course of the nerve up to the obturator foramen. To achieve the maximum length, intraneural dissection must normally be performed after the nerve passes the posterior border of the adductor brevis. An endoscopic approach or extended proximal incision is recommended to easily reach the proximal part of the nerve as far as the obturator foramen.