Deep Myofascial Kinetic Lines in Horses, Comparative Dissection Studies Derived from Humans

Abstract

Seven superficial myofascial kinetic lines have been described earlier in horses in a comparative dissection study to the human lines. The lines act as an anatomical basis for understanding locomotion, stabilization, and posture. Further dissections verified three profound equine lines comparable to those described in humans and a fourth line not described previously. Forty-four horses of different breed and gender were dissected, imaged and video recorded. The horses were euthanized due to reasons not related to this study. A Deep Ventral Line (DVL) very similar to that in the human was verified in these studies. The line spans from the insertion of the profound flexor tendon in the hindlimb to the base of the cranium and oral part of the cavities of the head. It includes the profound, hypaxial myofascial structures, the ventral coccygeal muscles, the psoas muscles, the diaphragm, the longus colli/capitis muscles and the ventral capital muscles. The inner lining of the pelvic, abdominal and thoracic cavities with all the organs, vessels and nerves are also included. The line is closely connected to the autonomic nervous system by the vagus nerve, the pelvic nerves, the sympathetic trunk and several of the prevertebral nerves and ganglia. The new line identified in this study, is a Deep Dorsal Line (DDL), which starts in the dorsal tail muscles. It comprises myofascial structures of the spinocostotransversal system from the tail to the head including the nuchal ligament. It connects to the dura mater and has a major role in controlling the motion and stabilization of the Columna vertebralis. Both the DDL and the DVL include the coccygeal myofascia and periosteum of the skull. Due to differences in biped and quadruped anatomy the Front Limb Adduction Line (FADL) and the Front Limb Abduction Line (FABL) differ from the human lines. The lines are identified as slings in the brachial and antebrachial regions. The FABL includes structures for abduction and internal rotation connecting to the Front Limb Retraction Line (FLRL), and the FADL structures of adduction and external rotation in close proximity to the Front Limb Protraction Line (FLPL). The front limb lines support the movement of the front limb around the “thoraco-scapula pivot joint” medially at the level of the upper third of the scapula. The DVL identified in this study is similar to the human DFL whereas the front limb lines differ somewhat from the deep human arm lines due to differences in bi- and quadruped anatomy and biomechanics. We have identified and described this new equine DDL. The lines altogether explain a profound body balance and confirm the three-dimensional equine fascial network, which is of great clinical and biomechanical importance.