Torques in the human upper ankle joint level and their importance in conservative and surgical treatment.

The paper deals with the torques of external muscles acting on the upper ankle joint under weight-bearing conditions and their importance in diagnosing and treating the human foot. Experimental data were collected and calculations were performed. Based on the experiments with the biomechanical model of the foot and upper ankle joint, it was shown how the changes in the force arms of the external muscles of the foot under weight-bearing conditions, change the torque. The real values of muscle forces and torques of the external muscles of the foot were calculated. Taking into account the distance of the lines of muscle action from the axis of rotation of the upper ankle joint the rotational force of the muscles was calculated. The influence of changing the force arm on the rotational efficiency of the muscle balancing the moment of gravity was shown. Knowledge of muscle torque under weight-bearing conditions is crucial for correctly assessing foot biomechanics. It has been shown that torque (gravitational and muscular), not pure force, is crucial when assessing the rotational capacity of the analyzed joint. A change in the approach to diagnostics and treating paresis or weakness of extrinsic foot muscles was proposed through the manipulation of the distance of their action line from the axis of joint rotation.

The MRI appearance of myloglossus.

PURPOSE: This case report describes the MRI appearance and significance of the myloglossus muscle, a variant extrinsic tongue muscle. METHODS: The myloglossus muscle was incidentally discovered on imaging performed for head and neck cancer evaluation. RESULTS: The myloglossus is best visualized on non-fat saturated T2 MRI and has signal characteristics that match those of muscle. It originates at the angle of the mandible and inserts into the tongue between the styloglossus and hyoglossus. CONCLUSION: Accurate identification and delineation of the extrinsic muscles of the tongue, including the myloglossus, is essential for proper staging and treatment of head and neck cancers. This case report attempts to fill a void in depicting the MRI appearance of myloglossus muscle.

Comparison of foot posture and foot muscle morphology between lifesaver athletes and healthy adults.

This study aimed to compare the foot muscle morphology and foot posture between healthy adults and lifesavers in sandy beach sports. The participants included 15 lifesaver athletes and 15 healthy adults. Using a non-contact three-dimensional foot measurement device, the foot length, width, and arch height of the right foot were measured while standing and sitting without back support, and the transverse arch length ratio and arch height index were subsequently calculated. Muscle cross-sectional area was measured using an ultrasound imaging device. Muscle cross-sectional areas, arch height, foot width, arch height index, and transverse arch length ratio were larger in the lifesaver than in the healthy adult group. Lifesavers had higher arches and more developed intrinsic and extrinsic muscles than healthy adults. Performing physical activity while barefoot on sandy beaches may effectively develop the foot intrinsic and extrinsic muscles and raise the arch.

Morphological description of extrinsic muscles of the thoracic limb in a specimen of pudu (Pudu puda) / Descripción morfológica de la musculatura extrínseca del miembro torácico de un espécimen de pudú (Pudu puda)

SUMMARY: The pudu (Pudu puda) is classified as an artiodactyl of the Cervidae family. It is a native species found in Argentina and Chile. It is estimated that its population has been substantially reduced due to several causes, such as loss of forests, predation, hunting, and vehicle accident. Therefore, this species is protected due to its vulnerable conservation status. The extrinsic muscles of the thoracic limb have great importance in the biomechanical functionality of the suspension of the limb, neck, and head, as well as participating in the movement of the thoracic wall and thoracic limb. The objective of the present study is to describe the extrinsic musculature of the thoracic limb of a specimen of pudu, comparing the results with those described for domestic ruminants in the classical anatomical bibliography. Basic procedures: All extrinsic muscles were analyzed, describing shape, distribution, origin, and insertion. The results indicate that the pudu specimen has anatomical characteristics similar to domestic ruminants; however, some differences should be considered. Main findings: The brachiocephalicus muscle has an evident clavicular intersection that separates it into cleidobrachialis, cervicalis, and mastoideus pars. The pectoralis superficialis muscle has two distinct and independent pars, and the pectoralis profundus muscle has a partial fusion with the latissimus dorsi and cutaneous trunci muscles. The subclavius muscle is small and has an elongated shape and goes deep into the cephalic vein, just at the point it is a tributary of the external jugular vein. The results of this study present specific anatomical features of Pudu puda providing novel reference information and expanding scientific knowledge of this scarcely studied wild species.

RESUMEN: El pudu (Pudu puda) se clasifica como un artiodáctilo de la familia Cervidae. Es una especie nativa que se encuentra en Argentina y Chile y se estima que su población se ha reducido sustancialmente debido a varias causas, tal como la pérdida de bosques, depredación, caza y accidentes de vehículo. Debido a lo anterior esta especie está protegida por su estado de conservación vulnerable. Los músculos extrínsecos del miembro torácico tienen gran importancia en la funcionalidad biomecánica de la suspensión del miembro, el cuello y la cabeza, además de participar en el movimiento de la pared torácica y el miembro torácico. El objetivo del presente estudio es describir la musculatura extrínseca del miembro torácico de un ejemplar de pudu, comparando los resultados con los descritos para rumiantes domésticos en la bibliografía anatómica clásica. Se analizaron todos los músculos extrínsecos, describiendo la forma, distribución, origen e inserción. Los resultados indican que el espécimen de pudu tiene características anatómicas similares a las de los rumiantes domésticos; sin embargo, deben tenerse en cuenta algunas diferencias. Hallazgos principales: El músculo braquiocefálico tiene una interección clavicular evidente que lo separa en pars cleidobraquial, cervical y mastoideo. El músculo pectoral superficial tiene dos porciones distintas e independientes, y el músculo pectoral profundo tiene una fusión parcial con los músculos latissimus dorsi y cutáneo del tronco. El músculo subclavio es pequeño y tiene una forma alargada y se ubica profundamente a la vena cefálica, justo en el punto en el que es un afluente de la vena yugular externa. Los resultados de este estudio presentan características anatómicas específicas de Pudu puda proporcionando información de referencia novedosa y ampliando el conocimiento científico de esta especie silvestre escasamente estudiada.

Evidence for a trigeminal mesencephalic-hypoglossal nuclei loop involved in controlling vibrissae movements in the rat.

Previous studies performed in rats showed that the whisker-pad motor innervation involves not only the facial nerve, but also some hypoglossal neurons whose axons travel within the trigeminal infraorbital nerve (ION) and target the extrinsic muscles surrounding the whisker-pad macrovibrissae. Furthermore, the electrical stimulation of the ION induced an increase in the EMG activity of these muscles, while the hypoglossal nucleus stimulation elicited evoked potentials and single motor unit responses. However, the existence of a neural network able to involve the XIIth nucleus in macrovibrissae whisking control was totally unknown until now. Since other recent experiments demonstrated that: (1) the mesencephalic trigeminal nucleus (Me5) neurons respond to both spontaneous and artificial movements of macrovibrissae, and (2) the Me5 peripheral terminals provide a monosynaptic sensory innervation to the macrovibrissae, the present study was aimed at analyzing a possible role of the Me5 nucleus as a relay station in the sensory-motor loop that involves the XIIth nucleus neurons in rhythmic whisking control. Two tracers were used in the same animal: Fluoro Gold, which was injected into the whisker pad to retrogradely label the hypoglossal whisker-pad projection neurons, and Dil, which was instead injected into the Me5 to label its projections to these hypoglossal neurons. Results demonstrated that terminals of the Me5 neurons monosynaptically target the hypoglossal whisker-pad projection neurons. The functional role of this sensory-motor connection is discussed, with particular regard to a hypothesized proprioceptive reflex in whisker-pad extrinsic muscles that can be elicited by the activation of the Me5 macrovibrissae receptors.

Activation of individual extrinsic thumb muscles and compartments of extrinsic finger muscles.

Mechanical and neurological couplings exist between musculotendon units of the human hand and digits. Studies have begun to understand how these muscles interact when accomplishing everyday tasks, but there are still unanswered questions regarding the control limitations of individual muscles. Using intramuscular electromyographic (EMG) electrodes, this study examined subjects' ability to individually initiate and sustain three levels of normalized muscular activity in the index and middle finger muscle compartments of extensor digitorum communis (EDC), flexor digitorum profundus (FDP), and flexor digitorum superficialis (FDS), as well as the extrinsic thumb muscles abductor pollicis longus (APL), extensor pollicis brevis (EPB), extensor pollicis longus (EPL), and flexor pollicis longus (FPL). The index and middle finger compartments each sustained activations with significantly different levels of coactivity from the other finger muscle compartments. The middle finger compartment of EDC was the exception. Only two extrinsic thumb muscles, EPL and FPL, were capable of sustaining individual activations from the other thumb muscles, at all tested activity levels. Activation of APL was achieved at 20 and 30% MVC activity levels with significantly different levels of coactivity. Activation of EPB elicited coactivity levels from EPL and APL that were not significantly different. These results suggest that most finger muscle compartments receive unique motor commands, but of the four thumb muscles, only EPL and FPL were capable of individually activating. This work is encouraging for the neural control of prosthetic limbs because these muscles and compartments may potentially serve as additional user inputs to command prostheses.