Anatomic and histomorphometric study of the nerve to the vastus lateralis in cadaver for its clinical application in facial reanimation.

Abstract

The innervated vastus lateralis flap (IVLF) is a barely used possibility for facial palsy reconstruction because of its thickness compared to the gracilis, latissimus dorsi, and pectoralis minor flaps. The aim of this study is to perform a precise description of the intramuscular distribution of the nerve motor branches and its relationship with the vascular pedicle in order to harvest a segmental muscle flap with the best contractile strength to restore facial reanimation. The study was performed on 16 adult cadaver thighs identifying the vastus lateralis muscle and the distribution and relationships of its neurovascular pedicle and branches. We evaluated where the nerve pierced the muscle and the course of the nerve within it. Transverse segments of the nerve were obtained from the proximal and distal ends of the nerve and stained using anti-ChAT (Choline acetyltransferase) antibodies which are specific of motor neurons. A nerve for the vastus lateralis from the posterior division of the femoral nerve divided into 2 branches in 56% of cases; the principal branch coursed along the vascular pedicle and pierced the muscle more proximally than the respective vessels, and a minor branch that pierced the muscle 25-60 mm proximally. There were 3 main intramuscular branches. The nerve length (mean 132.65 ± 22.89 mm) allowed to reach the contralateral side of the face in almost all cases (95%). The mean ChAT positive fibers was 351.0± 92.4/mm2 at the proximal end, and 270.3± 87.9/mm2 at the distal end (p= 0.49). The number of ChAT negative fibers was higher than ChAT positive in both proximal and distal ends of the nerve. We propose the IVLF as a one-step surgical flap for facial paralysis reanimation due to the constant neurovascular pattern and lengthy pedicle. The amount of motor fibers in several segments of the nerve is appropriate to produce a powerful contraction for dynamic reconstruction.