Manual Therapy and Chiropractic

Manual therapy involves the application of the hands directly to the body, with the goal of treating soft tissue injuries or articular dysfunction. Chiropractic, osteopathy, massage therapy, therapeutic touch, and certain physical therapy techniques are considered forms of manual therapy. Chiropractic is a health profession concerned with the diagnosis, treatment, and prevention of disorders of the musculoskeletal system and the effects of these disorders on the nervous system and general health.¹ The word chiropractic is derived from the Greek words cheir, meaning “hand,” and praktikos, meaning “concerning action.” The goal of chiropractic is to optimize health through the inherent healing ability of the body (i.e., homeostasis) as affected by and integrated through the nervous system.² The practice of chiropractic focuses on the relationship between structure (primarily the spinal column) and function (as coordinated by the nervous system) and how that relationship affects the preservation and restoration of health. Chiropractic uses controlled forces (i.e., adjustments), which are applied to specific joints or anatomical regions, to induce therapeutic responses through induced changes in joint structures, muscle function, and neurological reflexes. Research in people demonstrated reductions in pain and muscle hypertonicity and increased joint range of motion after chiropractic treatment.^2,3

Joint mobilization and manipulation are two types of induced articular movements used in musculoskeletal rehabilitation to restore joint function. Mobilization is characterized as repetitive joint movements induced within the normal physiological range of joint motion (Figure 93-1). Joint manipulation (e.g., chiropractic adjustment) occurs within the paraphysiological zone, which lies outside of the active (i.e., patient induced) and passive ranges of joint motion. In people, joint mobilization and manipulation induce different physiological responses. Manipulation in people relieved adjacent spontaneous myoelectrical activity immediately, whereas mobilization did not.²

Fig. 93-1 Schematic representation of the three articular zones of joint motion: physiological, paraphysiological, and pathological. The elastic barrier and the anatomical limit mark the transitional boundaries among the three articular zones.

Practitioner Qualifications

Equine practitioners have seen a proliferation in the use of chiropractic techniques on horses, in one form or another. Veterinarians currently do not receive any formal education in chiropractic principles or techniques; therefore many equine clinicians do not have a basic understanding of chiropractic principles or clinical applications. Conversely, chiropractors (doctors of chiropractic) do not have any formal training in comparative anatomy, physiology, or pathology or clinical equine experience. Veterinary medicine, for the most part, has been forced to acknowledge the use of chiropractic and other nontraditional modalities by horse owners who have sought practitioners who use these techniques and have experienced their perceived therapeutic effects.⁴ However, limited research has been done to evaluate the clinical effectiveness of chiropractic techniques in horses. If veterinarians have not taken the time or made the effort to learn more about these nontraditional techniques, objectively evaluating the use of chiropractic, discussing the indications or contraindications for a specific treatment modality, or applying these techniques clinically is difficult. Therefore owners often seek advice about alternative therapies or treatment from someone who is not their regular veterinarian and often without his or her knowledge. To complicate matters, many laypersons claiming to be equine chiropractors are not professionally trained or licensed in chiropractic or veterinary medicine. These lay practitioners often have a limited knowledge of equine musculoskeletal anatomy, physiology, biomechanics, and pathology. Because of the potential misapplication, chiropractic evaluation and treatment should be provided only by licensed professionals (i.e., veterinarians or chiropractors working under the direct supervision of a veterinarian) who have pursued additional postgraduate training in animal chiropractic principles and techniques. The primary organizations in North America currently involved in training and certifying veterinarians and chiropractors in animal chiropractic are Options for Animals, based in Wellsville, Kansas; Parker College of Chiropractic in Dallas, Texas; and the Healing Oasis Wellness Center in Sturtevant, Wisconsin and in Canada. An additional course on equine osteopathy is offered at the Vluggen Institute in San Marcos, Texas. Equine manual therapy courses in Europe include Focus on the Equine Spine in the Netherlands; McTimoney College of Chiropractic in England; the International Academy of Veterinary Chiropractic in both Germany and England; and a Healing Oasis Wellness Center–sponsored course in Germany.

Most state chiropractic and veterinary medical boards do not allow chiropractors to treat animals unless they are working under the direct supervision of a veterinarian. This requires that the veterinarian and chiropractor work together in evaluating and treating the horse and provide appropriate follow-up care as indicated. It is strongly recommended that owners and referring veterinarians seek out licensed professionals (veterinarians or chiropractors) who have had specialized training and experience in chiropractic evaluation and treatment of horses. Veterinarians who have not pursued formal postgraduate training are not qualified to provide chiropractic care and risk producing more harm than potential benefit. It is a good idea to ask equine chiropractors about their professional and postgraduate training or certification, horse experience, and the types of techniques that they use (i.e., hands only versus more aggressive techniques, or the use of additional instruments). Chiropractic and osteopathy require a working knowledge and understanding of vertebral anatomy, physiology, biomechanics, pathology, and rehabilitation. Combining the knowledge and expertise of the veterinary and chiropractic professions provides practitioners with new insights and methods for diagnosing and managing horses with select vertebral or musculoskeletal disorders. A similar multidisciplinary approach has developed in human medicine in the last 20 years to address chronic pain syndromes and vertebral column disorders.

History of Equine Chiropractic

Chiropractors often have been asked to treat the horses of clients who have experienced the benefits of chiropractic care for their own back or neck problems. Horse owners often want the opportunity to have the same type of care for their horses, without the potential adverse effects of medications or surgery. The recent increased awareness of the prevalence and management options to address back problems with which traditional veterinary medicine has had difficulty in dealing has also stimulated horse owners’ interest in complementary forms of treatment.⁵ Any vertebral column disorder can have serious effects on a horse’s ability to perform. Back problems can be classified into three basic types of injuries—those involving the muscles, tendons, and ligaments (soft tissue injuries); bones and joints (osseous injuries); or nervous system (neurological disorders). However, several concurrent injuries have been reported in 17% of horses with back pain.⁶ Diagnosis of the underlying vertebral pathological conditions in horses with back pain is important for the appropriate treatment and management of these disorders (see Chapter 52).

Many horses in which chiropractic may be useful often have a history of a traumatic event or an injury related to overexertion.⁷ Trauma may occur as a single event (i.e., macrotrauma), such as a trailer accident, flipping over backward, or substantial falls over jumps. Severe musculoskeletal injuries may improve gradually, but they never resolve totally, or debilitating arthritis or soft tissue fibrosis may subsequently develop. Chronic overuse injuries (i.e., microtrauma) usually are associated with poor saddle fit, improper riding techniques, inadequate shoeing, or faulty conformation. Long periods of confinement, inconsistent training programs, or cumulative stresses and strains related to prolonged, high-level athletic activities also may predispose horses to musculoskeletal injuries and reduced performance. Older horses, like elderly people, are susceptible to loss of vertebral column flexibility, joint degeneration, and loss of muscle strength. Aged horses also have increased healing times and increased chances of having chronic conditions or abnormal musculoskeletal compensations from prior injuries. Chiropractic techniques have helped identify and treat some of these previously undiagnosed or poorly managed problems in horses. Most veterinarians use chiropractic techniques to complement their conventional veterinary practice.

Complementary Approaches

Prevalence of back problems in horses varies greatly (from 0.9% to 94%), depending on the specialization or type of practice surveyed: general practice, 0.9%; Thoroughbred racehorse practice, 2%; veterinary school referrals, 5%; mixed equine practice including dressage, show jumpers, and eventing, 13%; spinal research clinic, 47%; and equine chiropractic clinic, 94%.⁸ Clinicians often have difficulties when dealing with horses with no obvious localized pain or vague, unspecified lameness. Neck or back problems and limb injuries often are interrelated. Distal limb injuries can cause an alteration in carriage of the affected limb and altered gait, which subsequently can overwork or injure proximal limb musculature and the paraspinal musculature. Similarly, vertebral column injuries can produce gait abnormalities, increased concussive forces, and distal limb lameness. The diagnostic dilemma facing clinicians is to decide whether the limb or the vertebral column is the primary or initial cause of the horse’s clinical problem. Unless the primary cause of the neck or back pain is identified and treated, most horses will have recurrent back pain when returned to work after a period of rest or a trial of antiinflammatory medications. Nonspecific back pain most likely is related to a functional impairment and not a structural disorder. Therefore many back problems may be related to muscle or joint dysfunction, with secondary soft tissue irritation and pain generation.⁹

Chiropractic provides expertise in evaluating vertebral column disorders and can provide an additional means of diagnosis and early treatment options in certain types of gait abnormalities or performance problems. Prepurchase examinations using chiropractic examination techniques can help identify horses that have chronic underlying neck or back problems.⁷ Chiropractic addresses subclinical conditions or abnormal biomechanics, which may progress to future debilitating musculoskeletal injuries. Chiropractors are trained in using physiotherapy modalities, strength training exercises, massage, stretching techniques, and other forms of musculoskeletal and nerve rehabilitation. Equine chiropractic is a complementary modality that can be used in veterinary medicine for the diagnosis, treatment, and potential prevention of select musculoskeletal disorders in horses. However, although a few recent studies have investigated the short-term effectiveness of chiropractic intervention in the horse, none have addressed performance benefits, long-term efficacy, and the safety or cost-effectiveness of chiropractic procedures in equine veterinary medicine.

Pathophysiology and Mechanisms of Action

The vertebral motion segment is the functional unit of the vertebral column and includes two adjacent vertebrae and the associated soft tissues that bind them together. The basic elements of joint dysfunction include altered articular neurophysiology, biochemical alterations, pathological conditions of the joint capsule, and articular degeneration.^2,3 Vertebral segment dysfunction (i.e., chiropractically defined subluxation) is a vertebral lesion characterized by the following:

Fig. 93-2 Diagram of patterns of normal and altered joint range of motion. Symmetrical joint hypomobility is characterized by generalized stiffness. Asymmetrical joint hypomobility is characterized by reduced joint mobility in one or more directions (e.g., left lateral bending).

Numerous theories have been proposed and tested over the years to explain the causes of vertebral segment dysfunction in people and its effects on the neuromusculoskeletal system.^2,3 The chiropractically defined vertebral subluxation complex is a theoretical model that incorporates the complex mechanical and biochemical interactions of injured nervous, muscular, articular, ligamentous, vascular, and connective tissues.¹⁰ The theory of a “bone out of place” is outdated and not supported by current spinal research in people.

The goal of chiropractic treatment is to reduce pain and muscle hypertonicity, restore joint motion, and stimulate neurological reflexes. The exact mechanisms by which chiropractic techniques produce therapeutic effects are not certain. Chiropractic treatment may reduce musculoskeletal pain by stimulating nociceptive reflexes and release of neuropeptides (i.e., endorphins and enkephalins).^2,11,12 Concurrent muscle spasms restrict joint motion and may contribute to the further development of joint stiffness. In people, palpatory changes in osseous symmetry after manipulation often are associated with soft tissue alterations and not actual reduction of an articular misalignment.⁹ Chiropractic care can improve restricted joint motion and may reduce the associated harmful effects of joint immobilization.^2,3 In response to chronic pain or stiffness, new movement patterns are learned by the nervous system and adopted in an attempt to reduce pain or discomfort. Long after the initial injury has healed, adaptive or secondary movement patterns that predispose additional joints or muscles to injury may persist.⁹ Chiropractic treatment is thought to affect mechanoreceptors (i.e., Golgi tendon organ and muscle spindles) to induce reflex inhibition of pain and reflex muscle relaxation and to correct abnormal movement patterns.^10,12 Additional modalities used to address altered movement patterns in people and horses include stretching or relaxing hypertonic muscles, strengthening weak muscles, and reeducating movement patterns.⁹

Successful chiropractic treatment requires specific techniques and psychomotor skills.³ A thorough knowledge of vertebral anatomy and joint biomechanics is required for proper chiropractic evaluation and treatment. Joint manipulation often induces a palpable release or movement of the restricted articulations. An audible cracking or popping also may be heard during chiropractic treatment as the applied force overcomes the elastic barrier of joint resistance.^13,14 The rapid articular separation produces a cavitation of the synovial fluid.¹⁵ Radiological studies of synovial articulations after manipulation in people have shown a radiolucent cavity within the joint space (i.e., vacuum phenomenon) that contains 80% carbon dioxide and lasts for 15 to 20 minutes. A second attempt to recavitate the joint will be unsuccessful and potentially painful until the intraarticular gas is reabsorbed (i.e., refractory period).

Equine Chiropractic Research

The focus of recent equine manual therapy research has been on assessing the clinical effects of chiropractic techniques on relieving pain, improving flexibility, and restoring spinal motion symmetry. A veterinarian’s ability to physically induce movement in a horse’s back has been questioned. Pilot work in three horses that were instrumented with spinal transducers attached to Steinman pins implanted into dorsal spinous processes at adjacent vertebrae demonstrated that manually applied forces associated with chiropractic techniques were able to produce substantial segmental spinal motion.¹⁶ The induced spinal motions were usually beyond the normal range of segmental motion that was measured during treadmill locomotion (up to 227% larger segmental spinal range of motion induced by high-velocity, low-amplitude thrusts than measured at the walk). The next logical research question would be what, if any, are the therapeutic effects of these induced spinal movements? In two randomized, controlled clinical trials, pressure algometry was used to measure mechanical nociceptive thresholds (MNTs) in the thoracolumbar region and to evaluate whether chiropractic treatment can reduce back pain (or increase MNTs) relative to findings in a control group of horses.^17,18 The first study evaluated 24 horses in active exercise, with the treatment group receiving high-velocity, low-amplitude thrusts applied to the thirteenth thoracic vertebra (T13) to the sixth lumbar vertebra (L6) region.¹⁷

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