Anatomy and functional architecture of the anconeus muscle / Anatomía y arquitectura funcional del músculo ancóneo

The anconeus is a small muscle situated at the elbow. Although the anconeus is active during elbow extension its importance for the movement is probably small. It could work as an elbow stabilizer. The object of this study was to investigate some anatomic and architectural characteristics of the anconeus, in the hope of shedding light on its function. We studied twenty adult cadaveric specimens. The anconeus originates by the lateral epicondyle of the humerus and inserts along the proximal ulna. The superficial shape of the anconeus is triangular. Tridimensionally the anconeus resembles a hemisected rectangular-based pyramid, with the base at the ulna and apex at the lateral epicondyle. The muscle fibers arise obliquely from the tendinous expansion and inserts at the ulna. Thus, the architecture of the anconeus is penniform, an architecture able to produce more force then displacement. The design index of 0.3 also suggests a force muscle.

El ancóneo es un pequeño músculo situado en la región del codo. Aunque el músculo ancóneo es activo durante la extensión del codo su importancia para este movimiento es probablemente pequeña. Podría actuar como estabilizador del codo. El objetivo de este trabajo fue investigar algunas características anatómicas y arquitectónicas del músculo ancóneo, con la esperanza de lanzar una cierta luz en su función. Estudiamos 20 cadáveres de adultos. El músculo ancóneo se origina al lado del epicóndilo lateral y se inserta en la ulna. La forma superficial del músculo ancóneo es triangular. Tridimensionalmente, el músculo ancóneo se asemeja a la mitad de una pirámide de base rectangular, con la base en la ulna y el ápice lateral al epicóndilo lateral. Sus fibras musculares describen un trayecto oblicuo con una extensión tendinosa que se insertan en la ulna. Por lo tanto, la arquitectura del músculo ancóneo es peniforme, una arquitectura conveniente para producir mayor fuerza con el desplazamiento. El índice de diseño de 0,3 también lo sugiere como un músculo de fuerza.

Diagnostic Sensitivity of Several Muscles in Repetitive Nerve Stimulation Test for Myasthenia Gravis / 영남의대학술지

BACKGROUND: This study was undertaken to evaluate the diagnostic sensitivity of several muscles in repetitive nerve stimulation test (RNST) for myasthenia gravis (MG) patients. MATERIALS AND METHODS: The study population consisted of 39 MG patients classified by modified Ossermann's classification. Using Stalberg's method, RNST was systematically performed in facial (orbicularis oculi and nasalis) and upper extremity (flexor carpi ulnaris, abductor digiti quinti and anconeus) muscles. RESULTS: The significant electrodecremental response of RNST were noted in orbicularis oculi (58.9%), nasalis (51.3%), flexor carpi ulnaris (42%), anconeus (41%) and abductor digiti quinti muscles (27%). Among the 3 muscles of upper extremity (abductor digiti quinti, flexor carpi ulnaris and anconeus), the positive electrodecremental response of anconeus muscles was significantly higher than other two muscles (p<0.05) in type IIa, IIb and there were no statistical differences of the positive electrodecremental response between orbicularis oculi and nasalis muscles. The facial muscles showed more prominent decremental responses than upper extremity muscles in type I MG(p<0.05). In type IIa MG patients, there were no significant statistical differences between facial and upper extremity muscles but significant statistical differences among upper extremity muscles. In type IIb MG patients, there were no significant statistical differences in all tested muscles in spite of the increased positive electrodecremental response of RNST. CONCLUSION: On the basis of this study, RNST would be initially performed for the orbicularis or nasalis in type I MG and for the anconeus in type IIa or IIb MG.