Manual therapy is a general term that refers to treatment approaches involving the hands (such as massage or chiropractic). Treatments done with the hands may also be instrument-assisted. Although manual therapies are most commonly used for the treatment of somatic pain or other musculoskeletal maladies, other indications may include lymphedema, immunosuppression, or visceral discomfort.
Massage techniques vary widely, ranging from the traditional kneading and stroking to deep tissue work requiring concerted pressure. The most commonly researched technique is Swedish massage, also known as classic muscular massage. Swedish massage incorporates several maneuvers, including effleurage (stroking and gliding), tapotment (percussion), petrissage (kneading), and friction massage. Effleurage involves tissue compression. Tapotment vibrates tissue, petrissage stretches adherent fibrous tissue, and friction lengthens connective tissue to reduce contractures. Massage techniques are multicultural and share similarities; for example, Swedish massage has similarities to the Chinese manual therapy technique Tui Na. Other massage techniques include German connective tissue massage and Rolfing, a strong and sometimes painful form of “deep tissue” massage introduced in the USA. "Medical massage" addresses specific diagnoses with soft-tissue techniques, with the goal of treating certain conditions. It differs from relaxation massage in its "manual medicine" approach, ie, using the hands to help heal conditions seen in practice.
Manual therapy frequently targets the spine. When people speak about “animal chiropractic,” “veterinary manual therapy,” or “animal adjusting,” they are usually referring to forceful maneuvers directed to the back or neck in an effort to alleviate pain or, more generally, spinal dysfunction. Some interventions are borrowed from the human chiropractic field and incorporate mechanical devices known as adjusting tools or activators. When used, this hand-held device, which resembles a metal syringe with a rubber knob at the end, delivers a rapid “thump” to the patient, roughly mimicking the action of a person applying a thumb thrust to the body. More violent and less sophisticated methods applied to horses incorporate mallets and blocks of wood intended to “drive protruding spines into line”; all such methods have, as yet, failed to demonstrate therapeutic utility in animals.
Massage focuses on soft-tissue elements—namely, muscles and the enveloping fascia. Benefits such as stress and blood pressure reduction, normalized gastric motility, immune regulation, and amelioration of depression may share a common mechanism of action. That is, the neuromodulatory and homeostatic effects of massage likely pertain to parasympathetic nervous system stimulation.
Evidence now supports use of massage as an aid to muscle recovery after exercise or injury, a means to improved circulation, and a way to bolster immune function. It also addresses GI motility dysfunction and neonatal issues such as failure to thrive. Massage also can improve lymphatic drainage in cases of lymphedema, although the effects may be transient.
In contrast to massage, the rapid thrusts in chiropractic have many theoretical—but no proven—mechanism(s) of action. The lack of current knowledge tends to be extrapolated into speculation, and chiropractic theories may be presented as fact. Claims are made that chiropractic manipulation activates muscle spindles, Golgi tendon organs, joint capsule mechanoreceptors, and receptors in the skin, and that simultaneous firing of multiple types of receptors modifies CNS activity, blunting nociception and normalizing muscle tone, joint mobility, and sympathetic nervous system activity. However, there is inadequate basic science data to substantiate any of these claims. No chiropractic technique has been shown to be superior to another; little chiropractic research has been done in veterinary patients.
For massage and chiropractic in veterinary patients, indications may include neck or back pain or stiffness, inability to sit straight, reduced flexibility, muscle spasms, poor performance, difficulty going up or down stairs, inability to walk or run in a straight line, and abnormal tail carriage. However, there are no data from well-designed scientific trials to support the utility of such interventions in dogs, cats, or horses. The evidence for massage in human babies and adults suggests support for including this approach in animals with stress, pain, arthritis, sluggish digestion, or spinal cord injury.
Because adverse events of complementary therapies are underreported, the true range and incidence of risks from massage remain unknown. Patients who are especially fragile or ill generally require briefer and gentler treatments with less digital pressure and compression. Soft-tissue techniques would not be applied directly over areas of infection, acute inflammation, tumor, recent surgical procedures, or thrombosis. Similarly, massage may not be ideal in areas of acute inflammation, skin infection, bone fracture, burn, deep vein thrombosis, or cancer.
Contraindications for chiropractic might include conditions that weaken bone or other structural elements such that applying a thrust to a vulnerable spine or limb could lead to serious injury. Examples of deossifying or destabilizing conditions include hyperadrenocorticism, neoplasia, secondary renal hyperparathyroidism, degenerative joint disease, and disk disease. Some animal chiropractors have advocated chiropractic for a gamut of problems, including idiopathic lameness, intervertebral disc disease, Wobbler syndrome/cervical vertebral insufficiency, spondylosis, cauda equina syndrome, urinary incontinence, neuropathies, postsurgical rehabilitation, trauma, and organ pathology. However, many of these may actually constitute contraindications. One research-based human CAM reference places joint hypermobility, arthritis, and neurologic problems from disc disease under the heading of contraindications to chiropractic, along with cancer, infectious disease, fractures, clotting disorders, osteopenia, and osteoporosis.
Excessive pressure from massage and forceful thrusts from chiropractic both have the potential to injure organs, vessels, neural tissue, or bones. Deep massage of the abdomen may damage organs (rupture/bleeding) and nerves (from direct pressure onto nerves); intense pressure could dislodge a stent or catheter or embolize thrombi. With chiropractic manipulation, thrusts are not always innocuous. A heavy-handed individual can seriously harm or even kill an animal. Even milder thrusts may injure animals weakened by age, joint pathology, osteopenia, or neoplasia.
Injuries from chiropractic usually result from trauma to the spinal cord or brain arising from impacted blood vessels, discs, or nervous tissue. Human neurologic and neurosurgical reports have revealed an association between stroke and upper cervical manipulation. In addition to high velocity techniques, deep massage or other pressing techniques in the suboccipital region have damaged vessels and caused neurologic impairment and death. Although rare, stroke from cervical chiropractic manipulation of human patients is well recognized and likely occurs more often than is reported. The mechanism of injury typically involves arterial dissection or spasm.
A study of human patients with neck pain showed that 25% of patients reported increased neck pain or stiffness after chiropractic treatment, and adverse reactions were more likely to follow higher force techniques. The study concluded that because high-force techniques failed to demonstrate superior effectiveness to low-force maneuvers, chiropractors should consider conservative manipulative procedures. Especially in geriatric or otherwise fragile animals, manual therapy techniques from the soft-tissue therapy repertoire constitute safer approaches than forceful, high-velocity techniques.
From a mechanical standpoint, extrapolating human chiropractic theories to animals raises questions. Biomechanical forces on the spine of a quadruped differ from those in bipeds. Furthermore, the vertebrae of horses are the size of a human fist and are surrounded by muscle, tendon, and ligament layers several inches thick, leading to questions as to whether equine vertebrae can be manipulated at all.
Claims that spinal joints or other bones move “out of place” have not been substantiated. Even if such lesions exist, the diagnostic measures commonly used to detect them are not reproducible or reliable. The overall utility of manipulative therapy for the treatment of a condition (including its most common indication, musculoskeletal pain) has not been established.
Finally, additional controversy arises from the fact that manual therapies may be delivered by nonveterinarians. Manual therapies pose potential risks; when they are practiced by overzealous therapists with insufficient education about anatomy and pathology, the risk of injury to the patient or the practitioner increases. Lack of familiarity with animal behavior, zoonotic illness, and proper restraint techniques can pose risks to the therapist or bystanders. Furthermore, nonprofessionals may not have suitable liability insurance for such incidents.
State laws may or may not allow nonveterinarians to treat animals. Some may allow a human chiropractor or massage therapist to treat nonhumans but require a certain level of supervision by a veterinarian. Because state laws differ, veterinarians should check into the legal framework that allows or specifically disallows this form of care by nonveterinarians before referring or delegating care to them.