Características morfológicas y morfométricas del músculo aductor del hállux y sus ramos motores / Morphological and morphometric characteristics of the hallux adductor muscle and its motor branches

El hállux se encuentra en aducción en relación al eje del pie y para mantener esta posición requiere de una adecuada alineación ósea, la que está determinada principalmente por la actividad muscular. Una de las estructuras involucradas en esta función es el músculo aductor del hállux, el cual puede producir hállux valgus o hállux rígido cuando ocurre un desbalance en su actividad normal. A pesar de la importancia de este músculo, existen pocos estudios de su complejo neuromuscular. El objetivo de esta investigación fue describir las características morfológicas y morfométricas del músculo aductor del hállux y sus ramos motores en 30 miembros inferiores. Se disecó la planta del pie hasta alcanzar el plano del músculo aductor del hállux y sus ramos motores. La longitud media de la cabeza oblicua del músculo aductor del hállux fue de 78,16 mm (±13,35) con un ancho máximo promedio de 20,55 mm (±2,59) y un tendón de 25,87 mm (±7,97) de longitud. Respecto a las mismas medidas en la cabeza transversa, estas fueron 39,55 (±8,26), 15,04 (±3,52) y 18,51 (±10,04), respectivamente. La inervación de ambas cabezas del músculo aductor del hállux provenía del ramo profundo del nervio plantar lateral. En la mayoría de las muestras dicho nervio emitió un ramo para la cabeza oblicua y uno para la cabeza transversa. La cabeza oblicua presentaba uno o dos puntos motores, localizados generalmente en su tercio medio. La cabeza transversa presentaba sólo un punto motor localizado frecuentemente en su tercio lateral. El conocimiento de las características morfológicas y morfométricas del músculo aductor del hállux y de sus ramos motores son clínicamente significativos, puesto que permiten realizar una aproximación de la localización del punto motor en los procedimientos electromiográficos.

The hallux is adducted in relation to the axis of the foot and to maintain this position requires adequate bone alignment, which is determined mainly by muscle activity. One of the structures that is involved in this function is the adductor muscle of the hallux, which can produce hallux valgus or rigid hallux when an imbalance occurs in its normal activity. Despite the importance of this muscle, there are few studies of its neuromuscular complex. The objective of this study was to describe the morphological and morphometric characteristics of the adductor muscle of the hallux and its motor branches in 30 lower limbs. The sole of the foot was dissected until it reached the plane of the muscle and its motor branches. The average length of the oblique head of the adductor muscle of the hallux was 78.16 mm (± 13.35), with an average maximum width of 20.55 mm (± 2.59) and a tendon of 25.87 mm (± 7, 97) in length. Regarding the same measurements of the transverse head were 39.55 (± 8.26), 15.04 (± 3.52) and 18.51 (± 10.04), respectively. The innervation of both heads came from the deep branch of the lateral plantar nerve. In most of the samples, said nerve emitted a bouquet for the oblique head and one for the transverse head. The oblique head had one or two motor points, generally located in its middle third. The transverse head had only one motor point that was usually in its lateral third. The knowledge of the morphological and morphometric characteristics of the adductor muscle of the hallux and its motor branches are clinically significant, since they allow an approximation of the location of the motor point in electromyographic procedures.

Functional equivalence of dihydropyridine receptor a1S and b1a subunits in triggering excitation-contraction coupling in skeletal muscle

Molecular understanding of the mechanism of excitation-contraction (EC) coupling in skeletal muscle has been made possible by cultured myotube models lacking specific dihydropyridine receptor (DHPR) subunits and ryanodine receptor type 1 (RyR1) isoforms. Transient expression of missing cDNAs in mutant myotubes leads to a rapid recovery, within days, of various Ca2+ current and EC coupling phenotypes. These myotube models have thus permitted structure-function analysis of EC coupling domains present in the DHPR controlling the opening of RyR1. The purpose of this brief review is to highlight advances made by this laboratory towards understanding the contribution of domains present in a1S and b1a subunits of the skeletal DHPR to EC coupling signaling. Our main contention is that domains of the a1S II-III loop are necessary but not sufficient to recapitulate skeletal-type EC coupling. Rather, the structural unit that controls the EC coupling signal appears to be the a1S/b1a pair.