We know and understand in an intellectual way that the entire body is connected; that there are close direct connections as well as indirect connections between the different structures and systems of the body. But do we really understand the impact of specific connections between body systems, and how we can influence them and use them to our patients’ advantage during rehabilitation?
Understanding the superficial and deep myofascial connections within the equine body can help us to more effectively rehabilitate the whole body, including the digestive system and organs, the nervous system and the musculoskeletal systems.
Let’s discuss a few of the intricate connections between the somatic and visceral systems of the equine body.
The fascial lines and slings
The fascia can be divided into seven superficial and four deep lines, as found by Elbrond and Schultz during systematic dissections of the equine body. The superficial lines include the
- Superficial Dorsal Line (SDL),
- Superficial Ventral Line (SVL),
- Lateral Line (LL),
- Spiral Line (SL),
- Functional Line (FL),
- Front Limb Protraction line (FLPL),
- Front limb Retraction line (FLRL).
The deep myofascial kinetic lines include the
- Deep Dorsal Line (DDL),
- Deep Ventral Line (DVL),
- Front Limb Abduction Line (FABL),
- Front Limb Adduction line (FADL).
Each of these lines serves to connect sections of the body in a functional manner, to promote specific movements and functions of the body.
For a description of where these lines run and which anatomical structures are included in each, please watch the research refresh videos in the Onlinepethealth Equine members portals, or read the open-access research publications.
The Fascia and the Nervous System
We are increasingly aware of the intricate connection between the fascia and the nervous system, understanding that every nerve ending is housed in fascia, that nerves have to travel through fascial layers and sheets, and, most importantly, that the fascia itself is richly innervated and in constant communication with the nervous system.
Consider the DDL (deep dorsal line) as it runs along the spinal column from the tail to the suboccipital muscles – the rectus capitis major and minor, and the obliquus capitus caudalis and cranialis. These muscles connect to the atlantooccipital and atlantoaxial membranes, connecting to the dura mater, forming myodural bridges. Connections similar to this can be found along the length of the spine at the dorsal intervertebral foramenae.
This close relationship of the DDL with the spinal column and the dura mater highlights one of the mechanisms of action of craniosacral therapy, osteopathy or chiropractic interventions.
The DVL likewise runs along the ventral bodies of the spine, as well as encapsulating the thoracic and abdominal cavities. From a neurological perspective, we find the vagus nerve running through and along this fascial line. The health and correct functioning of the ventral fascial line is paramount to the optimal functioning of the vagus nerve, which controls parasympathetic functions such as digestion, heart rate and the horse’s immune response.
The Poll to Pelvis Connection
The link between the poll and the pelvis is one that we are very aware of as Vetrehabbers – rarely will a dysfunction in one occur without dysfunction in the other, and often we can lessen symptoms of pain and dysfunction in one by treating the other.
Multiple fascial lines contribute to the connection between the poll and the pelvis, including the superficial and deep dorsal lines, the superficial and deep ventral lines, the lateral line, and the spiral line.
The poll and pelvis are connected along a dorsal chain, a ventral chain, a lateral chain and a spiral chain. Understanding this really highlights why we have been able to observe such a close connection clinically for many years!
The Thoracolumbar Junction
On the ventral aspect of the thoracolumbar junction, the iliopsoas complex attaches to the spine in a cranial direction, while the diaphragm connects in the same area, in a caudal direction. These two structures form part of the DVL and create a direct connection between the locomotory muscles of the hindlimb and the diaphragm responsible for inspiration, also accessing both the thoracic and abdominal cavities.
This connection highlights the role of the locomotory muscles in the inspiration and expiration of the horse – a relationship we are already familiar with – but also forces us to think about that relationship in reverse – when respiration affects the locomotion of the hindlimbs. When there is a dysfunction or source of pain in the ribs or diaphragm, hindlimb locomotion may be adversely affected as well.
On the dorsal aspect of the thoracolumbar region, the functional line crosses over from one side to the other, connecting the humerus of the forelimb, through the latissimus dorsi and the thoracolumbar fascia, to the opposite hindlimb, specifically through the fascia latae and vastis lateralis to the patella ligaments of the stifle joint.
This functional connection between a diagonal pair of limbs over the thoracolumbar region again highlights the importance of this area of the spine and its role in the healthy and optimal function or action of the fore- and hindlimbs of the horse.
The cervicothoracic junction
The lower cervical area, or the cervicothoracic junction, is an area we are considering more and more frequently in our patients as malformations in this area of the cervical spine become more commonly recognised. In this region, the cervical spine takes on a curve in extension, which compresses the intervertebral joints and makes adequate stabilisation of this area essential.
The DVL (deep ventral line) forms part of the stabilisation of this area through the longus colli and scalenus muscles, as well as forming part of the cranial thoracic aperture. The cranial thoracic aperture is a wide and complex region of the DVL, where the role of the fascial structures changes from the thoracic cavity to a more active line of fascia in the cervical spine.
The connection between the visceral and the somatic systems of the body is again highlighted in this area, where a direct connection can be made with the tongue, pharynx, larynx, hyoid and guttural pouch of the horse, through the muscles of the cervical spine and into the thoracic cavity.
Understanding these myofascial connections and lines can give us a deeper understanding of the function of the equine body, as well as how we might be able to influence both superficial and deeper structures during rehabilitation for a more profound and long-lasting change.