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OBJECTIVE: To investigate the feasibility of using free gracilis muscle transfer along with the brachialis muscle branch of the musculocutaneous nerve to restore finger and thumb flexion in lower trunk brachial plexus injury according to an anatomical study and a case report. METHODS: Thirty formalin-fixed upper extremities from 15 adult cadavers were used in this study. The distance from the point at which the brachialis muscle branch of the musculocutaneous nerve originates to the midpoint of the humeral condylar was measured, as well as the length, diameter, course and branch type of the brachialis muscle branch of the musculocutaneous nerve. An 18-year-old male who sustained an injury to the left brachial plexus underwent free gracilis transfer using the brachialis muscle branch of the musculocutaneous nerve as the donor nerve to restore finger and thumb flexion. Elbow flexion power and hand grip strength were recorded according to British Medical Research Council standards. Postoperative measures of the total active motion of the fingers were obtained monthly. RESULTS: The mean length and diameter of the brachialis muscle branch of the musculocutaneous nerve were 52.66±6.45 and 1.39±0.09 mm, respectively, and three branching types were observed. For the patient, the first gracilis contraction occurred during the 4th month. A noticeable improvement was observed in digit flexion one year later; the muscle power was M4, and the total active motion of the fingers was 209°. CONCLUSIONS: Repairing injury to the lower trunk of the brachial plexus by transferring the brachialis muscle branch of the musculocutaneous nerve to the anterior branch of the obturator nerve using a tension-free direct suture is technically feasible, and the clinical outcome was satisfactory in a single surgical patient.

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The radial nerve is a terminal branch of the brachial plexus that innervates the entire posterior compartment of the upper limb. Researches have shown that the branches can contribute to innervation of the muscles from the anterior compartment of the arm. This study sought to identify branches of radial nerve for brachialis and coracobrachialis muscles and its clinical value during surgery. Dissection was performed in 60 arms, from 30 corpses selected from the Human Anatomy Laboratories of Universidade Estadual de Ciências da Saúde de Alagoas (UNCISAL). In each arm, three segments of the same proportion were considered (proximal, middle and distal) in order to observe the number of radial nerve branches to brachialis and coracobrachialis muscles. Branches were identified in 4 of the 60 upper limb (6.66%) with the following distribution: nerve with 1 branch to the brachialis muscle in the distal third (1.66%); with 1 branch to the middle third of the coracobrachialis (1.66%) and 5 branches to the coracobrachialis muscle in the proximal third; 1 branch being found in an upper limb (1.66 %) and 4 branches in the other upper limb (1.66 %). The event was not bilaterally in the same body, and in four cases there was no branching, but only communication with other terminal nerves of the brachial plexus. In conclusion, although most authors do not describe the possibility of the occurrence of radial nerve branches to the muscles of the anterior compartment of the arm, this condition exists as an anatomical variation.

El nervio radial es un ramo terminal del plexo braquial que inerva el compartimiento posterior del miembro superior. Diversos estudios han mostrado que sus ramos pueden contribuir a la inervación de los músculos del compartimiento anterior del brazo. El presente estudio tuvo como objetivo identificar ramos del nervio radial dirigidos a los músculos braquial y coracobraquial y su importancia clínica durante las cirugías. Para ello, se disecaron 60 brazos de 30 cuerpos formolizados en los Laboratorios de Anatomía Humana de la Universidad Estadual de Ciencias de la Salud de Alagoas, Brasil (UNCISAL). En cada brazo, se consideraron tres partes de similares proporciones (proximal, medio y distal) para localizar los ramos dirigidos a los músculos mencionados. En 4 de los 60 brazos (6,66%) se identificaron ramos con la siguiente distribución: un ramo para el músculo braquial en el tercio distal (1,66%); un ramo para el tercio medio del músculo coracobraquial (1,66%) y cinco ramos para este mismo músculo en su tercio proximal; en otro miembro (1,66%)se encontró solo un ramo y en la otra muestra (1,66%) se encontraron cuatro ramos. Ninguno de los casos fue bilateral y en los cuatro casos no había ninguna ramificación. No hubo comunicación con el nervio musculocutáneo pero si con otros ramos del plexo braquial. Aunque la mayoría de los autores no describe la posibilidad de que el nervio radial inerve a los músculos anteriores del brazo, esta disposición existe como una variación anatómica.

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La doble inervación del músculo braquial está dada por el nervio musculocutáneo y por ramos provenientes del nervio radial según lo describen algunos textos anatómicos y numerosos trabajos científicos. Sin embargo, no existe consenso en la frecuencia con la que ésta se presenta. El objetivo de este estudio es verificar la presencia y determinar la frecuencia de la contribución del nervio radial en la inervación del músculo braquial. En el presente trabajo se utilizaron 30 miembros superiores previamente fijados con solución fijadora y conservadora. Se realizó disección de la región braquial para determinar la presencia de ramos del nervio radial inervando al músculo braquial, verificando la presencia de ramos que penetraban en el músculo y tomando muestras de estos ramos en el sitio donde perforaban al músculo para su estudio histológico. Fue posible observar la presencia de ramos del nervio radial que penetraban en el músculo braquial en un 90 porciento de los casos; en ellos el punto motor de estos ramos se ubicó siempre en el tercio distal del músculo. De acuerdo a los resultados obtenidos en el presente trabajo, la doble inervación del músculo braquial observada por autores clásicos y reportada en estudios en diversas poblaciones, está presente en alto porcentaje de la muestra. Estos hallazgos pueden servir de referencia para procedimientos quirúrgicos, estudios electromiográficos y sonográficos.

The dual innervation of the brachialis muscle by the musculocutaneos nerve and branches from the radial nerve has been described by some anatomical texts and several scientific papers; however, there is no consensus about the frequency with which this occurs. In this study we proposed to check the presence and determine the frequency of the contribution of radial nerve in the innervations of the brachialis muscle. In this study we used 30 upper limbs fixed in fixative and conservative solution. Dissection of the brachial region was carried out, checking the branches that penetrated the muscle and taking samples of these branches to histological study. It was possible to observe the presence of branches of the radial nerve innervating the brachialis muscle in a 90 percent of the sample used in this study; the motor point of these branches was always located in the distal third of this muscle. According with the results of this study, the dual innervations of the brachial muscles observed by classical authors and reported by several investigations is also present in a high percentage of the sample. These findings can serve as reference for surgical procedures, electromyographic and ultrasound studies.

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