Introduction
The spine is a central stabilizing structure in any mammal. All appendages are connected to it via bony or soft tissue attachment. Chiropractic, or spinal manipulative therapy (SMT), can be a powerful tool in restoring the body to its proper mechanical and neurophysiologic state after injury or disease, and can assist with maintainance of health of canine patients. This chapter reviews the history, theory, and terminology of animal chiropractic; gives a general overview of adjustment and techniques; reviews common indications and precautions; discusses anatomy, biomechanics, and functional neurology; and finally, discusses educational opportunities and legal issues. Although manipulative therapy can be applied to any accessible joint in the body, the focus of this chapter will be on the spine.
Animal Chiropractic History
Early History
Chiropractic originated with D.D. Palmer in 1895. Believing that the spine was the key to all disease and disorders, he used chiropractic as an entire system of medicine, and started the first school of chiropractic, now known as the Palmer School of Chiropractic. His son, B.J. Palmer, took over the school and promoted the newly developed profession. He was reputed to have treated animals as well as people at the school. Many individuals trained by the Palmers went on to develop their own theories and techniques.
The 1980s
In the 1980s, the field of animal chiropractic came into being when Sharon Willoughby, DVM, began to apply this medical system to her patients. After practicing general medicine for several years, she enrolled at the Palmer School and studied the differences between human and animal anatomy. Tom Offen, DC, mentored her work adapting chiropractic to animal patients, and she went on to finish her Doctor of Chiropractic (DC) degree. Dr. Willoughby established the first course in animal chiropractic and founded the American Veterinary Chiropractic Association in 1989.
Animal Chiropractic as a Profession
Animal chiropractic is not legally recognized as a unique profession. Both veterinarians and chiropractors have opportunities for advanced training and certification. Much progress has been made with respect to understanding biomechanics and neurophysiology, resulting in a more scientific and evidence-based modality. To distinguish it from practice on humans, the term veterinary spinal manipulative therapy (VSMT) is used.
Chiropractic Theory
Evolution of Chiropractic Theory
As the profession grew, so did the desire for a more thorough understanding of the process by which dysfunction occurs and why manual therapy is effective (Figure 23.1). Today, many theories are being investigated, including nerve compression, spinal cord compression, axoplasmic aberration, somatoautonomic dysfunction, and facilitation (Leach & Phillips, 1986). Central to these theories is the concept of subluxation.
Figure 23.1 Evolution of subluxation theory. Subluxation theory has grown and developed since the early days of chiropractic, reflecting a more thorough understanding of complexity in both pathophysiology and treatment.
Adapted from Vernon (2010).
Segmental Spinal Dysfunction or Subluxation
The word chiropractic is derived from the Greek roots, cheir (the hands) and praxis (to practice). Initially, D.D. Palmer believed that a bone out of place was the cause of a number of clinical signs in his patients. He termed this abnormal relationship between two adjacent vertebrae a subluxation. The signs that he attributed to the subluxation were metabolic and neurologic as well as musculoskeletal.
The term subluxation is the hallmark of chiropractic theory and practice. Many individuals have sought to define it, leading to over 100 synonymous terms (Gatterman, 1995). The Consortium for Chiropractic Research defines it as “a motion segment in which alignment, movement integrity, and/or physiologic function are altered though contact between the joint surfaces remains intact” (Gatterman, 1995).
Subluxation and Other Chiropractic Terminology
To better understand the concept of subluxation, it is important to be familiar with basic chiropractic terminology (Table 23.1).
Table 23.1 Chiropractic terminology
| Term | Definition |
| Subluxation | Dysrelationship between two vertebral segments; may be anatomic but is often a subtle, functional dysrelationship. |
| Motion segment | Two adjacent vertebra and all of the associated structures (muscles, ligaments, vessels, and the contents of the intervertebral foramen). |
| Intervertebral foramen | Space between vertebrae through which the spinal nerves and associated structures pass. |
| Adjustment | High velocity, low amplitude manipulation (thrust) delivered to a specific hypomobile motion segment using a specific force and depth. Used to restore mobility to that segment. |
| Contact point | The part of the chiropractor’s hand that is used to deliver the adjustment. There are many possible contact points, but most often the “v-trough” (between the thumb and second metacarpal) or supported thumb is used. |
| Segmental contact point | The part of the vertebra that the chiropractor uses to adjust the segment. Contact points vary with spinal regions as well as extremities. The points typically used include spinous processes, transverse processes, mammillary processes, lamina, and other bony prominences (tuber sacrale). |
| Line of correction | The direction of the manipulative thrust, along the plane of the zygapophysial joint which is restricted. Subtleties vary from segment to segment, as with joint mobilization. |
| Zygapophysial joint (Z joint) | Joint formed by the cranial and caudal articular processes of adjacent vertebrae. Also known as a facet joint. See anatomy section for detailed description. |
| Static palpation | Assessment of positional symmetry or dysrelationships without regard to mobility. |
| Motion palpation | Assessment of functional mobility without regard to static position. |
The Motion Segment
The motion segment (Figure 23.2) is generally accepted as the smallest unit of motion in the spine and is composed of two adjacent vertebrae and all of the associated structures. These structures include muscles, tendons and ligaments, joints, nerves and vessels, and the contents of the intervertebral foramen (IVF). The relationship between the two vertebrae is anatomically and neurologically complex. When there is a minute alteration in this relationship, the body responds with numerous mechanisms designed to maintain homeostasis.
Figure 23.2 The motion segment consists of two adjacent vertebrae and all associated structures. A. Dorsal spinous processes. B. Vertebral bodies. C. Transverse processes. D. Articular facets. E. Supraspinous ligament. F. Interspinous ligament. G. Ligamentum flavum. H. Dorsal longitudinal ligament. I. Ventral longitudinal ligament. J. Joint capsule. K. Intervertebral disk. L. Intervertebral foramen.
Adapted from Jurek & McCauley (2006).
The IVF
The IVF is the communication portal of the nervous system (Willoughby, 1998). Foramina are found at each spinal segment from C2 through the sacrum. The boundaries of the IVF include the vertebral notches and facet joint capsules on either side, intervertebral disk (IVD) ventrally, and ligamentum flavum dorsally. The primary content is the spinal nerve, surrounded by the cerebrospinal fluid (CSF) and supported by a dural extension that eventually blends with the epineurium, the recurrent meningeal nerve that supplies the IVD (and other areas), the dorsal longitudinal ligament, meninges, spinal artery, intervertebral veins, lymphatics, and connective tissue that serves as a shock absorber to protect the delicate structures within.
The Vertebral Subluxation Complex (VSC)
The VSC is a model used to describe the interrelationship of clinical signs associated with segmental dysfunction in the spine. Rather than defining a distinct subluxation, it describes a more general view of the complexity of alteration in spinal motion. The VSC consists of nine components of pathology that can occur individually, but more often collectively, when a vertebral subluxation occurs, with kinesiopathology as the central factor around which all other changes occur (Figure 23.3).
Figure 23.3 The vertebral subluxation complex model. Muscles, nerves, vessels, and connective tissue (all part of the motion segment) are intimately involved in development of kinesiopathology and incur pathologic changes as a result. The sequela to this pathology is inflammation eventually leading to tissue damage.
Adapted from Lantz (1995).
Clinical Procedure
The Chiropractic Examination
The chiropractic examination is not significantly different from a thorough rehabilitation evaluation. It begins with attaining a signalment and thorough history followed by assessment of general physical health. Particular emphasis is placed on posture (Figure 23.4) and gait analysis as well as palpation of the spine and extremities.
Figure 23.4 A. Normal posture. Note the squarely placed limbs, level topline, and smooth muscle outlines in this dog. B. Abnormal posture. This geriatric canine exhibits pelvic limbs held forward under her body and a slightly kyphotic topline. There is some loss of the secondary curvature in the lower cervical spine, resulting in low head carriage.
Abnormalities in static alignment, muscle tone/strength/symmetry, and range of motion are noted for each vertebral segment, each extremity joint, the temporomandibular joint (TMJ), and often the ribs, sternum, and tail. Symmetry in the bones and soft tissue of the cranium is also noted (Figure 23.5). Any signs of segmental dysfunction (pain, excessive tightening or spasm of muscles, heat, and reduced or increased mobility) are noted. Neurologic assessment is completed to establish a baseline, and radiographic evaluation is performed as indicated.
Figure 23.5 A Papillon is examined for symmetry in the head, static alignment, and anterior/posterior motion of the atlas.
Adjustment or Spinal Manipulation
An adjustment is defined as a high velocity, low amplitude thrust directed at a specific spinal segment with a specific force and depth. It is synonymous with a grade 5 joint mobilization. Grades 1–4 joint mobilizations deliver intervention via low velocity motion with increasing amplitude (lowest for grade 1, highest for grade 4) within the passive range of motion. Initial models described an adjustment as going beyond normal passive range of motion into a paraphysiologic space. This is where the spring occurs with overpressure in a normal joint. Manipulations are performed only on hypomobile joints. Vernon proposed a new model that more rationally describes the adjustment as occurring within the clinical physiological range, slightly before the end limit of this range (Figure 23.6) (Vernon & Mrozek, 2005). This results in restoration of full range of motion after manipulation (Figure 23.7).
Figure 23.6 Model of mobility in a dysfunctional joint. AC = active range of motion. P = passive range of motion. PH = “paraphysiologic space.”
Adapted from Vernon & Mrozek (2005).
Figure 23.7 Model of mobility in manipulation. AC = active range of motion. P = passive range of motion. PH = “paraphysiologic space.”
Adapted from Vernon & Mrozek (2005).
The setup involves finding the line of correction across the plane of the joint and placing the contact point of the therapist’s hand (most frequently the supported thumb) on the segmental contact point (muscles over a bony prominence, most often dorsal spinous, transverse, or mammillary process in the thoracolumbar spine, lamina/pedicle junction in the cervical spine, and various contact points in the pelvis and extremities).
Initially, the joint is taken to tension (developing a preload force). A rapid thrust is applied in a specific direction (line of correction) along the plane of the hypomobile joint to provide gapping in the joint. This may produce an audible sound due to fluid cavitation (Brodeur, 1995) although other mechanisms have been proposed.
Follow-up is generally recommended based on the degree of pathology and the likelihood of the patient holding the adjustment for a particular length of time. For patients with significant pathology, a second adjustment may be recommended in 2–3 days. For those with many compensatory issues, repetition may initially be done weekly. Therapy is tapered as the patient improves. For maintenance of health, intervals from monthly to every few months may be appropriate. Sporting dogs at major competitions may be treated daily to optimize performance.
Commonly Used Techniques
Because philosophies differ regarding the primary or root issue contributing to dysfunction, over 100 different techniques have been developed to address spinal subluxations, including
- Gonstead
- Diversified
- Logan basic
- Sacro-occipital
- Applied kinesiology
- Activator
- Network
- Thompson.
Directional and Anatomical Descriptions, Listings
The language that is used when recording findings and documenting therapy is relative to human anatomy (e.g., anterior, superior) (Table 23.2). This is referred to as a listing and is written in the form of an abbreviation. Because motion tends to be complex, the listing is based on the predominant restriction (Table 23.3).
Table 23.2 Directional and anatomic abbreviations and terms
| Abbreviation | Human term | Veterinary term |
| P | Posterior | Dorsal |
| A | Anterior | Ventral |
| S | Superior | Cranial |
| I | Inferior | Caudal |
| PSIS | Posterior superior iliac spine | Tuber sacrale |
| ASIS | Anterior superior iliac spine | Tuber coxae |
| TMJ | Temporomandibular joint | Temporomandibular joint |
Table 23.3 Listings
Indications and Precautions
Indications
Any disorder that results in abnormal musculoskeletal or neurologic function is an indication for application of chiropractic. This includes an almost exhaustive list of problems when considering the complexity of the nervous system and potential for modulation. Many studies have established efficacy of chiropractic in humans, principally related to back and neck pain (Bronfort et al., 2004).
Primary Spinal or Joint Disorders
With the exception of treating contraindicated areas (such as painful intervertebral disk disease [IVDD]), manipulative therapy can improve mobility, assist neurologic healing, and rebalance muscle tone and function while reducing pain. Table 23.4 lists common disorders that may improve with chiropractic.
Table 23.4 Indications for chiropractic intervention
| Primary spinal and peripheral joint disorders |
| Spondylosis |
| Facet joint osteoarthritis |
| Intervertebral disk disease |
| Fibrocartilagenous embolus |
| Lumbosacral stenosis |
| Cervical vertebral instability/stenosis |
| Discospondylitis |
| Degenerative myelopathy |
| Muscle pathology in the lumbar spine (iliopsoas strain) |
| Spine and neck trauma (only when stability present) |
| Temporomandibular joint pain |
| Rib injuries |
| Osteoarthritis |
| Fibrosis/adhesion |
Nonprimary Problems Resulting in Spinal Hypomobility
Many other musculoskeletal diseases result in abnormalities in spinal mobility as a result of increased stress or imbalance in the body. Chronic lameness typically results in abnormal position of the spine at rest and/or in motion. Muscle tightness and spasm can result in segmental dysfunction and pain. Immobility from enforced rest (crating) or nonspinal paresis (i.e., Coonhound paralysis, diabetic neuropathy) can lead to significant dysfunction and loss of segmental mobility. Overuse injury can contribute to subluxation, with athletic patients at higher risk. This is especially true of those who undergo chronic repetitive patterns of stress, such as working dogs and those competing in flyball and agility.
Precautions and Risks
The benefits of chiropractic can be profound, but the risks also must be taken into account. The most notable risks in humans include cauda equine syndrome resulting from lumbar manipulation (Shekelle et al., 1992) and vertebrobasilar accidents following cervical manipulation (Hurwitz et al., 1996). The incidence of complications remains quite small (1 per 100 million and 5–10 per 10 million adjustments, respectively) compared to procedures that we consider routine, such as vaccination (38.2 per 10,000 dogs vaccinated; Moore et al., 2005). Chiropractic must be performed by only well-trained professionals.
Pain
Although muscle spasm and hypertonicity of an intrinsic spinal muscle can cause significant pain, it is important to determine whether the degree of pain is appropriate to the clinical signs. Abnormal stresses on joint capsule, tendons, and ligaments can generate pain, and it can be referred from other areas (several segments above and below). Addressing muscle spasm and pain in the course of therapy may result in complete resolution and may restore functional biomechanics and neurologic input. Adjusting an area of reduced mobility where other pathology (IVDD, discospondylitis) exists could result in damage to the surrounding tissues. The prudent therapist manipulates a painful area only when the source of pain can be confidently determined.
Acute Injury/Postsurgical Areas/Instability
In the acute phase of injury, there is often considerable edema and inflammation (and possibly hemorrhage), so an area that is actually unstable may appear to be hypomobile. Any area that is unstable and any adjacent areas should not be adjusted due to the risk of creating further instability and tissue damage. Once the affected area has stabilized, it may be manipulated, beginning with gentle procedures and progressing as needed based on the stage of healing and tissue pliability.
Neoplasia
Extreme caution must be used when manipulating patients with neoplasia. Neoplastic tissue is abnormal and reactive by nature, and caution must be used to avoid increasing blood flow and resultant circulation of neurotransmitters that may be stimulatory to cancer cells. Areas adjacent to cancerous tumors should not be adjusted due to concerns for pain and inflammation, potential instability, and the potential to stimulate metastasis.
Infection/Fever
Spinal manipulation has the potential to increase circulation and lymphatic flow to and from a site of infection. If the infection is local, this may result in dissemination.
Anatomy and Biomechanics
The Canine Vertebral Column
The canine spine articulates in a manner that promotes proper stability as well as mobility in the body. It functions to protect the spinal cord and nerves and serves as a central axis of stability as well as motion for the body.
Typical Vertebra
Canine vertebrae are considered irregular bones, defined by their prominent protuberances where tendons and ligaments attach.
A typical vertebra has a distinct structure related to its function (Figure 23.8). The body is the main bony structure with a cranial (convex) and caudal (concave) articular surface. A vertebral arch consisting of a lamina (dorsal) and pedicle (lateral) on each side lies dorsal to the body. This forms a protective housing for the spine, with the opening known as the vertebral foramen. Collectively, these foramina are known as the vertebral canal.
Figure 23.8 Typical vertebral structure, L1. Note that the accessory process is typically found only from T11–12 to L4–5.
Adapted from Miller et al. (1979).
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