Back problems in horse
Back problems in horses have been recognized for centuries and descriptions are included in historical veterinary and farrier textbooks. However, just as in 1876 when Lupton wrote that back injuries are among the most common and least understood of equine afflictions, the causes of back problems in today’s horses are still difficult to pinpoint (1). In recent years some advances have been seen in technology and imaging tools to help with diagnoses of back problems, but the common application of clinical aids such as radiology, ultrasonography and scintigraphy are typically not sufficient (2), although some vertebral lesions can be visible in x-ray examination. Therefore, just like in the past, the modern diagnoses of back issues in horses commonly involves ruling out other possible conditions such as injuries or problems associated with the pelvis, stifle, proximal limb issues and poorly fitting tack (1,3).
Back pain is a common worry of an owner of a riding horse and a typical reason why the owner may contact a manual therapist to visit the horse. The owner may note that the horse is not quite right and a (subtle) loss in performance is typically observed (1,4). Symptoms of back problems may include sensitivity to palpation, stiffness (limited range of motion), hypertonicity of topline muscles and temperament change in a horse (4). It is highly debatable if primary back pain can cause direct lameness in a horse. For example, studies where reversible back pain was induced by injecting lactic acid into the long back muscle, longissimus dorsi, noted no change in the horse’s temporal and linear stride characteristics. However, a notable increase was observed in the rigidity of the back (5). Thus, it remains unproven if prolonged, long-term back pain and associated rigidity of the back could in principle lead to altered, irregular locomotion due to reduced swinging of the back. Most commonly, it is believed that if lameness and back pain coexist, thorough veterinary examination of proximal limbs should be carried out. Therefore, a veterinarian should be consulted prior to proceeding with any manual therapy in treatment of back pain in association with clinical lameness.
The primary causes of back pain in horses are typically divided into three categories, including (i) soft tissue injuries involving muscles, tendons and ligaments; (ii) osseous injuries involving bones and joints, and (iii) neurological injuries involving the nervous system (1,6). As many manual therapies, such as massage, mainly focus muscles and soft tissue mobilisation, the main muscles having an influence on the equine back are discussed further in the next section.
The muscles of the back and their relation to back problems
In this section the main muscles of the equine back are described and their link to back issues in horses are listed. In addition to the main locamotory muscles, the diaphragm is considered. Due to its vital role in the body it has direct influence on the whole horse including the back.
The topline epaxial (located above the spine) muscles in horses are located above the line of the transverse processes. These muscles are typically involved in lateral bending of the spine, or if contracted bilaterally they extend or hollow the spine. The largest muscle in the equine back is the epaxial muscle longissimus dorsi (LD), which originates at the ilium and the spinous processes of the sacrum, lumbar and thoracic vertebrae, inserting at transverse processes of the tubercles of ribs (2). LD has an important locamotory role as it makes a functional connection to the pelvis and sacrum. A recent study (7), investigating LD muscle fiber type also showed that this muscle is composed mainly of muscle fibers with fast twitch (MFT-II, muscle fiber type II), thus confirming the skeletal and locamotory role of LD. Therefore, this muscle is not made to carry a rider, although it does play a key role in the training of a riding horse (8, 9). Common causes of pain associated with LD are often directly or indirectly related to training of a riding horse. For example, poor saddle fit, poor balance of rider and incorrect training techniques are typically associated with tension or soreness in LD, although proximal limb lameness should not be excluded (8, 10, 11). Multifidus thoracic and lumborum (MTL) is another important epaxial muscle. It originates from the articular processes of the thoracic, lumbar and sacral spine and inserts on the summit (or sides) of spinous processes (11). In the study of the Hyytiäinen et al (7), MTL was shown to contain both slow and fast twitch fibers in relatively equal amounts, thus suggesting that this muscle plays a role both in postural support of the spine and in locomotion (extension and lateral bend of vertebrae). Atrophy, or muscle wastage, in MTL has been noted in a number of people suffering with chronic back pain (5, 12). In horses similar studies are still lacking to date, however, a recent paper by Stubbs et al (13) showed that a group of Thoroughbred racehorses suffering from osseous pathological changes in skeletal vertebrae also showed measurable left/right asymmetry in MTL muscle at or close to the site of pathology. In addition to skeletal problems, poor training techniques and incorrect saddle fit should be examined if problems are found in the MTL.
Hypaxial muscles, which are involved in spinal flexion and rotation of the vertebral column, are located below the line of the transverse processes. Of the hypaxial muscles this essay will focus on psoas minor and psoas major. These deep muscles insert on the ventral aspect of the lumbar and caudal three thoracic vertebrae from where they act mainly at the lumbosacral junction but are also able to flex the thoracolumbar junction and the lumbar spine. The psoas muscle is known to play an important role in stabilization and functioning of a healthy human spine (14, 15). In horses the psoas minor was shown to play a postural stabilising role where as psoas major seems to play a greater role in locomotion (7). In any case, the correct activation of psoas muscles is vital for the health of a riding horse as they aid in the coiling of the loins and enable the correct carriage of the rider (9). Injuries or problems associated with psoas may be difficult to pinpoint. Chronic contraction, or hypertonicity, of psoas muscles has been shown to cause bilateral back and sacro-iliac pain. Due to the deep position of these muscles in the body of a horse (or any animal), problems with psoas muscles may be difficult for veterinarians to diagnose and equine chiropractors and osteopaths to treat and manipulate (16). It has been suggested that psoas hypertonicity is often associated with chiropractic issues in the cervical or upper thoracic vertebrae from where the torque would be transmitted to lumbosacral dura (16). Therefore, like with many issues, psoas problems require thorough examination and a whole horse approach.
Psoas muscles have a connection with the diaphragm (via fascia discussed in the following sections). The diaphragm is a large hypaxial, muscular and tendinous structure that separates the chest from the abdominal cavity (17). It plays a vital role in respiration and also behaves as a pump, acting on organs, lymph vessels and general circulation. Each inhalation aids lymph drainage, organ filling and emptying, as well as allowing oxygen in and carbon dioxide out of the body (18). Horses that experience respiratory and back problems typically also suffer from restricted inhalation and subsequent problems in the diaphragm. The restricted respiration and subsequent lack of intake of oxygen will have many consequences for the health of the horse, including development of poor posture (e.g. hollow back, stiff shoulders, tight neck), shallow breathing and poor performance (17).
Fascia and its function in a body
In this essay special attention is given to the function of healthy fascia, and its role in locomotion and wellness of every individual being or animal, including its back and posture. The word ‘fascia’ originated from Latin with an original root meaning of bundle, strap, bandage and/or binding together. The current definition of fascia, outlined at the international Fascia Research Congress in 2007, states that fascia is “the soft tissue component of the connective tissue system that permeates the human body, forming a continuous, whole-body, three-dimensional matrix of structural support. It interpenetrates and surrounds all organs, muscles, bones and nerve-fibers, creating a unique environment for body system function (as cited in (19)).” In other words, fascia is a connective tissue present everywhere in the body, forming a three-dimensional web from head to toe and from skin to internal organs.
Fascia is made of three components: (i) the elastic portion, (ii) the collagenous portion and (iii) extra cellular matrix (also known as ground substance) (20). All the components are important, contributing to the healthy function of fascia in a body. The elastic portion, for example, creates flexibility and resilience, while the microtubules of crystalline saline solution in the collagenous part give fascia its shape, strength and stability. The form of ground substance varies according to cell function (from solid to more viscous fluid or gel), acting as a cushion. Fascia is also known as colloidal tissue, meaning that it is made of aggregates of small molecules that are relatively evenly distributed in a medium. This provides fascia more flexibility than other tissue types which can be made of more complex long-chained molecules. Furthermore, fascia has several distinctive properties, including elastic, plastic, viscoelastic and piezoelectric (20, 21). Due to its viscoelastic nature fascia can change in shape in response to activity, as well as make phase changes from liquid to plastic, or liquid to dense or liquid to dehydrated (20). In addition, due to its piezoelectricity, fascia is able to conduct electricity and transmit ionic changes down to cellular level.
So why is fascia so important? Fascia plays a vital role in healthy biomechanics (19, 22 and references therein). For example, fascia aids movement by allowing gliding of muscles (or cells within a muscle) over and around all the adjacent muscles and ligaments in a body. It also allows sliding of structures in tendon sheaths without any interference from the surrounding tissue. Further, fascia connects groups of muscles or connects muscles to non-muscular structures. Here focusing on the equine back, the thoracic and lumbar parts of the trunk are covered in a thoracolumbar sheet of fascia. This sheet of connective tissue plays an important role in biomechanics and body motility as it also links some of the largest muscles in a body – the latissumus dorsi and gluteus maximus (23). Restrictions and injuries in the thoracolumbar fascia can cause direct pain in the area, have postural implications and cause further compensations restrictions elsewhere in the body due to the three dimensional structure of fascia. Another crucial fascia-muscle connection influencing the equine back is the connection between the psoas muscles and the diaphragm. The fascial sheet linking these muscles is directly involved in posture, movement and breathing. Restrictions here can have undoubtedly body-wide implications.
So how is fascia injured and what does it mean in terms of body function and biomechanics? Just like other soft tissues, fascia may get injured in a direct trauma (including surgery) or it may get injured from repetitive motion or strain injury (20). When fascia gets injured, it loses its important properties, including its elasticity. Therefore, the three-dimensional network tightens, causing restriction and tension in the body. Further, the structure of the ground substance changes, becoming more solid. The arrangement of collagen fibers alters, leading to formation of cross-links, and denser and more fibrous structure (21). Therefore the connective tissue, or fascia, which plays a vital role in the biomechanics of the body, cannot support the body as it should and movement patterns become restricted. If the restriction in the connective tissues persists, in the long term this may be detrimental to the functioning of the fascial tissues (21). Furthermore, fascial restrictions and tightening can cause mechanical stress patterns in the body, pulling osseous structures out of correct alignment. This stress in turn can lead to pain and dysfunction in joints. Typically, alignment issues are noted in the pelvis, which is pulled crooked. In horses, misalignment in the pelvis is noted when the orientation of ischial tuberosities and tuber coxae are inspected. For example, one side of the pelvis may feel as if it has sheared upwards or forwards, or one side of the pelvis has rotated more down or laterally outwards. The misalignments in the pelvis are also typically transmitted through the whole spine and when inspected in detail these patterns of crookedness are also noted elsewhere in the body (e.g. individual vertebrae and level/position of shoulders and facial asymmetries) (20). To make matters more complex, multiple strain patterns are typically noted, especially in persistent traumas, leading to complex patterns of compensations. Compensation in the body will ultimately lead to uneven muscle development, incorrect biomechanics and possible further injuries.
Easing back pain with application of Myofascial Release
As fascia is present everywhere in the body, nearly all aspects of the body can be addressed with MFR in some way. Whether it is a scar, an alignment issue of spine, tendon or ligament injury, pain associated with muscle spasm in the back or a trapped nerve, MFR techniques can be applied to address these issue, keeping in mind the fascial connections in the body and the whole horse approach.
The physiological aim of the MFR is to restore the form and function of fascia by modifying cell permeability and by realigning the collagen fibers. The deformation of fascia happens as the therapist places her/his hands on the animal/patient. Due to the viscoelastic properties of fascia, the light and persistent mechanical pressure from the hands leads to changes in the electrical potential of the tissue (20, 21). The electrical change is further transmitted by the extra cellular matrix of the body leading to rehydration of the restricted area. As water is drawn into the tissue, it softens and metabolic status of the area changes. Importantly, the fascial tissue elongates and reduces muscle spams. All in all, this provides the animal/patient increased function, mobility, pain relief and reduces swelling (20).
In practice, the function of fascia is restored by the MFR therapist softly sinking their hands into the horse’s tissue, for example in the lumbar area, and carrying out the MFR move for a minimum of 90-120 seconds, although moves can last up to several or even over ten minutes. The element of time is very important in MFR, as it is needed for the deformation and rehydration of fascia. This also sets MFR apart from other manual therapy modalities. During a fascial release, the therapist is able to feel the tissue softening and starting to expand under the hands. Before the restriction is released, the therapist may feel a tingling sensation, stillness or pounding under her/his hands. At times some horses may get temporarily anxious but as the fascial barrier “breaks” the horse relaxes and can enter a dream-like state. Following the release the therapist feels a melting-like sensation as the tissue is rehydrated, followed by slow gliding of the hands, which is guided by intuition rather than intent, toward point of the next fascial restriction.
With respect to direct back pain and/or hypertonicity associated with the epaxial back muscles (LD and MTL), MFR performed at the area of the thoracolumbar fascia can offer pain relief and comfort, facilitate healing and enhance tissue repair in the top line muscles (20). In addition, MFR will also improve the circulation in the body, thus stimulating the elimination of waste products, such as lactic acid, which can accumulate in overworked muscles, including LD and MTL.
MFR can also be applied alleviate problems in the deep muscles, like the psoas and diaphragm (20); muscles which may be out of reach with other manual therapy modalities, such as sport massage. Specific MFR techniques can target these deep muscles and their surrounding fascia, hence releasing tissue and easing problems in these areas and other areas linked to these muscles via their fascial connections.
As fascia is also present around the ligaments, MFR can also aid the repair of ligament injuries and ease the soft tissue pain associated with them. In the case of primary back pain, injuries to the supraspinous and sacroiliac ligaments must be considered. MFR techniques targeting the thoracolumbar fascia can be applied. In addition, if the site of injury is visible in a form of focal swelling or asymmetry along the topline, a technique (e.g. crossed fingers) targeting the injured area can be applied.
Alignment issues in the spine and the vertebrae, causing musculoskeletal dysfunction and back pain, can be addressed with MFR. However, in MFR no direct spinal manipulations are performed like in chiropracty and osteopathy. Instead, a series of MFR moves are done to soften and mobilize the tissue in the pelvis, the thoracolumbar area and the neck. The mobilization of the soft tissue along the spine and pelvis will allow the bones along the vertebrae to realign themselves in the correct position with no direct force used. However, in some cases corrective techniques may be applied, which will aid the vertebra in the realignment process. However, these moves are only used if needed and they are only performed after MFR techniques have already softened and prepared the tissue along the restrictions.
- Fascia plays a crucial role in the biomechanics horses.
- The aim of the MFR is to restore the form and function of fascia by modifying the cell permeability and realigning the collagen fibers.
- With respect to back pain MFR is a powerful modality of manual therapy with several advantages over other techniques. MFR can address both soft tissue injuries and musculoskeletal dysfunctions (e.g. spine) in horses. Furthermore, due to the three-dimensional network of fascia, MFR can aid in alleviating back pain resulting from both primary and secondary issues.
- In MFR the horse is always considered as a whole. Fascial restriction in the back for example may have its origin elsewhere in the body.
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