Anatomical study of pronator teres muscle innervation and clinical significance in nerve transfer / Estudio anatómico de la inervación del músculo pronador redondo y significado clínico en la transferencia nerviosa

The anatomical relationship of the median nerve and its innervation pattern are variable and may have direct implications in surgical procedures such as distal nerve transfers. The objective of this study was to evaluate the anatomical variations of pronator teres muscle (PTM) innervation and its clinical significance in nerve transfers. Data were collected regarding the number of median nerve branches, site of their origin, contribution with branches of other muscles and the possibility of transferring expendable branches of PTM to the anterior interosseous nerve (AIN) and radial nerve. The most common origin of the branches was proximal to the humeral intercondylar line. The presence of only one PTM branch was identified in 9 limbs, in which 6 was exclusive for this muscle. The majority of specimens presented more than one branch to the PTM, with two branches in 19, although only 6 of these did not share branches with other muscles. The proximal branch of the PTM was long enough to be transferred to the AIN in 23 limbs and branches of the radial nerve in all. These transfers were possible even during the forearm prone-supination and flexion-extension of the elbow. The use of the PTM branch may be considered for transfers in C7-T1 root injuries of the brachial plexus, with care regarding the availability of multiple PTM branches and tension to the AIN and radial nerve branches.

La relación anatómica del nervio mediano y su patrón de inervación son variables y pueden tener implicaciones directas en los procedimientos quirúrgicos, como las transferencias de los nervios distales. El objetivo de este estudio fue evaluar las variaciones anatómicas de la inervación del músculo pronador redondo (MPR) y su importancia clínica en las transferencias nerviosas. Se obtuvieron datos sobre el número de ramas del nervio mediano, el lugar de origen, la contribución con ramas de otros músculos y la posibilidad de transferir ramas prescindibles de la MPR al nervio interóseo anterior (NIA) y al nervio radial. El origen más común de las ramas fue proximal a la línea intercondilar humeral. Se identificó la presencia de una sola rama de MPR en 9 miembros superiores, de los cuales 6 fueron exclusivas para este músculo. La mayoría de los especímenes presentaron más de una rama al MPR, con dos ramas en 19 de ellos, aunque solamente 6 no compartían ramas con otros músculos. La rama proximal del MPR fue lo suficientemente larga como para ser transferida a la NIA en un total de 23 miembros superiores y ramas del nervio radial. Estas transferencias fueron posibles incluso en el antebrazo, durante la supinación y la flexiónextensión del codo. El uso de la rama MPR puede considerarse para transferencias en lesiones de raíz C7-T1 del plexo braquial, con cuidado en cuanto a la disponibilidad de múltiples ramas de MPR y tensión a la NIA y las ramas nerviosas radiales.

Transfer of nerve branches of the flexor carpi radialis to the posterior interosseous nerve / Transferência de ramos nervosos do músculo flexor radial do carpo para o nervo interósseo posterior

ABSTRACT Objective: The objective of this paper was to study the anatomical variations of the flexor carpi radialis muscle (FCR) and determine in cadaver limbs whether the FCR nervous branch can be connected to the posterior interosseous nerve (PIN) without tension and how close to the target muscles the transfer can be performed. Method: Thirty cadaveric upper limbs were dissected. Results: The FCR received exclusive innervation of the median nerve, distally to the intercondylar line of the humerus. In 5 limbs, an isolated branch was found and in 25, a common trunk with other nervous branches occurred. We investigated whether the branch for the FCR was long enough to be transferred to the PIN. The diameter of the nerve branch for the FCR corresponded on average to 50% of the PIN. Conclusion: In 12 limbs, the branch destined to the FCR could be connected to the PIN, distally to the nerve branches to the supinator muscle even during the movements of the forearm and the elbow. In 18 specimens, it was necessary to mobilize the PIN for this innervation. Level of Evidence IV, Case Series.

RESUMO Objetivo: O objetivo do trabalho foi estudar as variações anatômicas do músculo flexor radial do carpo (FRC) e determinar, em membros de cadáveres, se o ramo nervoso do músculo FRC pode ser conectado ao nervo interósseo posterior (NIP) sem tensão e quão próximo dos músculos alvos a transferência pode ser realizada. Método: Trinta membros superiores cadavéricos foram dissecados. Resultados: O FRC recebeu inervação exclusiva do nervo mediano, distalmente à linha intercondilar do úmero. Em 5 membros encontrou-se um ramo isolado e em 25 ocorreu um tronco comum com outros ramos nervosos. Investigamos se o ramo para o FRC tinha comprimento suficiente para ser transferido para o NIP. O diâmetro do ramo nervoso para o músculo FRC correspondia, em média, a 50% do NIP. Conclusão: Em 12 membros, o ramo destinado ao FRC poderia ser conectado ao NIP, distalmente aos ramos nervosos para o músculo supinador mesmo durante os movimentos do antebraço e do cotovelo. Em 18 peças foi necessária a mobilização do NIP para essa inervação. Nível de Evidência IV, Série de Casos.