Measurement of Lateral Transmission of Force in the Extensor Digitorum Longus Muscle of Young and Old Mice

The main function of skeletal muscles is to generate force. The force developed by myofiber contraction is transmitted to the tendon. There are two pathways of force transmission from myofibers to tendons: longitudinal transmission that depends on tension elicited via the myotendinous junction and lateral transmission that depends on shear elicited via the interface between the myofiber surface and surrounding connective tissue. Experiments using animal muscle and mathematical models indicated that lateral transmission is the dominant pathway in muscle force transmission. Studies using rat muscle showed that the efficiency of lateral force transmission declines with age. Here, the lateral transmission of force was measured using the extensor digitorum longus muscle from young and old mice. Dependence on longitudinal transmission increased in the old muscle, and there was a trend for lower efficiency of lateral force transmission in the old muscle compared to the young muscle. There was a noticeable increase in the connective tissue volume in the old muscle; however, there was no significant change in the expression of dystrophin, a critical molecule for the link between the myofiber cytoskeleton and extracellular matrix. This study demonstrates the measurement of lateral force transmission in mouse muscles and that alteration in force transmission property may underlie age-related muscle weakness.

Anatomical Variations of the Peroneus Tertius and Extensor Digitorum Longus Muscles – Case Presentation

Introduction: The extensor digitorum longus and peroneus tertius muscles have multiple morphological variations. The tendinous slips of these muscles are used as grafts to replace other damaged tendons. Case presentation: We present a unique anatomical variant observed during dissection of a cadaver at the Department of Anatomy and Embryology of the “George Emil Palade” University of Medicine, Pharmacy, Science and Technology of Târgu Mureș, Romania. The peroneus tertius muscle was identified on the left lower extremity as originating from the inferior third of the fibula and interosseus membrane. The posterior belly of this muscle joins the muscular belly of the extensor digitorum longus muscle. The tendons of toes II to V detach from the extensor digitorum longus muscle with an additional tendon. This last tendon gives off an accessory tendinous slip; lateral to this, the peroneus tertius muscle tendon is observed. In case of the right lower limb we also noted the peroneus tertius muscle originating from the distal part of the extensor digitorum longus muscle. Regarding the extensor digitorum longus muscle we describe an accessory tendinous slip. Conclusion: The anatomical variation reported in this study is similar to those reported by previous studies, but displays particular characteristics regarding the VI tendon of extensor digitorum longus and the joining of the peroneus tertius and extensor digitorum longus muscles in the left lower extremity.

Prevalence and Topography of the Peroneus tertius Muscle: a Study of Human Cadavers

Introduction The peroneus tertius muscle, also known as fibularis tertius, is classified as an anatomic variation and has been described as inconstant in a wide variety of contemporaneous studies and in the classical medical literature. Its fibers are sometimes mistaken for those of the extensor digitorum longus muscle. In fact, peroneus tertius is detached from the extensor digitorum longus muscle through a tendon inserted into the base of the fifth metatarsal bone, after passing through the frondiform ligament of the extensor retinaculum. Objectives The present study evaluated the prevalence, origin and insertion point of the peroneus tertius muscle in human cadavers. Methods and Results Thirty-two lower limbs, 18.75% of which came from female cadavers, were obtained from two different anatomy laboratories at two separate institutes. The cadaver parts were dissected and photographed. Overall, the muscle was present in 93.75% of the samples and in 100% of the samples from female cadavers. The fibers of the muscle originated in the proximal third of the fibula in 6.68% of cases, in the middle third in 46.66% and in the distal third in 46.66% of cases. Insertion of the tendon was at the base of the fifth metatarsal in 70% of cases and in the space between the fourth and the fifth metatarsal in 30%. Conclusion Therefore, the peroneus tertius muscle was present in the majority of the cadaver parts analyzed; however, the sites of origin and insertion varied. These results contradict data in the classical literature and in contemporaneous studies.