Advances in small-animal medicine and surgery have led to an improved and sophisticated level of healthcare for pets. Patients with problems that were once considered untreatable can now be evaluated by specialists in a variety of disciplines. For example, in patients with orthopedic problems, diagnostic and treatment options have widely expanded. Orthopedic surgery is unique in that the corrective procedure is completed rapidly relative to the patient's recovery. After an orthopedic procedure, it is common to have a convalescent period of weeks to months before recovery is attained. Physical rehabilitation may help patients achieve maximum recovery. Physical therapy is also valuable for easing chronic pain in pets.
Physical therapy has become more common is small-animal patients, in part, because of its benefits in people. Clients are aware of these benefits because of the importance and ubiquity of physical therapy in human medicine. Many protocols in human physical therapy have been developed by using animal models. Likewise, techniques used in human physical therapy are being adapted for use in small and large animals. As information concerning physical rehabilitation increases in the veterinary literature, additional techniques will be incorporated in veterinary practices to improve the standard of care.
In this article, we introduce a variety of physical rehabilitation modalities available to small-animal practitioners, including their most common indications and their benefits. The benefits of physical rehabilitation are multifaceted, and some may not be intuitive. Depending on the modality used, benefits include pain relief, decreased inflammation and swelling, increased tissue extensibility and flexibility, strengthening, improved balance and proprioception, mobilization of tissues, improved limb and joint biomechanics, improved weightbearing, psychological benefits, weight loss, and improved cardiovascular and respiratory fitness.1-4
Postoperative rehabilitation begins with aggressive analgesia before anesthetic recovery to reduce peripheral and central nervous system sensitization to pain.5-9 Since pain is one of the primary factors limiting mobility, it is paramount that it be eliminated or minimized. Optimal pain relief encourages early mobilization of an affected limb. Untreated pain leads to an increased metabolic rate, cardiovascular stress, impaired immunity, central and peripheral hyperalgesia, pulmonary dysfunction, and guarding of the limb with the joints in a flexed position, a condition referred to as reflex inhibition.8,10
Nonsteroidal anti-inflammatory drugs (NSAIDs) that spare the cyclooxygenase-1 (COX-1) enzyme but inhibit the cyclooxygenase-2 (COX-2) enzyme, such as deracoxib and carprofen, significantly reduce the production of prostaglandins and inflammation associated with injury or surgical trauma.6 Other NSAIDs, such as tepoxalin, etodolac, and meloxicam, are also good anti-inflammatory agents but are not approved for administration before surgery in dogs. They may be given postoperatively if there is no danger of continued hemorrhage or to manage chronic pain. However, different NSAIDs should be not be given concurrently, and an appropriate washout period is necessary when changing NSAIDs. Avoid drugs that selectively inhibit the COX-1 enzyme, such as aspirin, in the perioperative period because they can inhibit platelet function and contribute to intraoperative hemorrhage.11,12
Other medications that may be used alone or in combination with NSAIDs for analgesia in dogs include acetaminophen, codeine (either alone or in combination with acetaminophen), and tramadol. An opioid narcotic, such as buprenorphine, morphine, hydromorphone, or oxymorphone, should also be used to provide multimodal analgesia, which is more effective for pain control than a single agent used alone.13 Ketamine blocks N-methyl-D-aspartate (NMDA) receptors that are at least partly responsible for the wind-up effect of an uncontrolled pain stimulus and may be combined with NSAIDs and opioid drugs in the immediate postoperative period for additional analgesia.7,14,15 Lidocaine may be used as a constant-rate infusion to decrease the amount of narcotics needed for pain control.14 Lidocaine can be combined with ketamine or an opioid, such as fentanyl or morphine, and be given as a constant-rate infusion after trauma, intraoperatively, or postoperatively to combat pain. Epidurals and regional and local nerve blocks should be used when appropriate to further alleviate pain. Intra-articular injections of bupivacaine or lidocaine administered before surgery and again at the end of surgery also provide analgesia.16
Analgesics should be continued through the postoperative period and should include opioids and NSAIDs along with physical therapy for pain relief. Physical rehabilitation is an effective adjunct to traditional anti-inflammatory and analgesic medications. In fact, physical rehabilitation can lower the dose or frequency of medication needed to control pain.2,4,13
Superficial thermal modalities
Ice compresses provide an excellent method to help control pain and inflammation in the immediate postoperative period. Not only is cryotherapy beneficial in the acute phase of tissue injury and inflammation, it is also advantageous after exercise and throughout rehabilitation when inflammation occurs. The effects of cryotherapy include vasoconstriction, decreased blood flow, reduced cellular metabolism and permeability, attenuation of traumatic or exercise-induced edema, and decreased muscle spasm.17,18 Another primary effect of cryotherapy is analgesia, which is thought to be a result of decreased sensory and motor nerve conduction velocity that occurs when nerve fibers are cooled.19,20
Cryotherapy can be accomplished with a variety of methods. The simplest way is by placing crushed ice in a sealed plastic bag and then wrapping the bag in a thin cloth, such as a pillowcase or towel. Alternatively, you can prepare a mixture consisting of two parts water and one part alcohol in a double-sealed plastic bag and place it in a freezer. The resulting pack is a frozen slush that conforms to any surface. Apply the cold pack for 15 to 20 minutes immediately after surgery while the patient is still recovering from anesthesia. Be careful when applying cold packs to patients that are already hypothermic postoperatively. Use cryotherapy for the first three or four days after surgery to help minimize inflammation, swelling, and pain from surgery. Apply the cold compress for 15 to 30 minutes three or four times a day.21,22 Monitor the patient for discomfort, and assess the tissues periodically for signs of adverse effects such as white or pale areas. Do not use cryotherapy in patients with poor or absent pain sensation.
Cryotherapy results in significant reductions in intra-articular temperatures of peripheral joints. After 15 minutes of ice application to the canine stifle, the temperature inside the joint can drop 7.4 F (4.1 C). Immersion in ice water can produce a more marked decrease in stifle joint temperatures (36.4 F [20.2 C]) but may produce decreases in rectal temperatures.22 Temperature changes vary depending on the type and depth of tissues cooled.21,23 In one study, ice packs applied to dogs' thighs for 20 minutes resulted in a precipitous drop in temperature of tissues up to a depth of 1 cm, but minimal cooling occurred at tissue depths of 3 cm. However, the tissue temperature remained below normal for 100 minutes.24
Apply heat to tissues only after the acute phase of inflammation is complete, generally three to five days after surgery or injury. Commercially available hot packs are generally used for heat therapy and may be heated in a microwave until they are warm to the touch. Alternatively, you can make a microwavable hot pack by placing rice in a sock and knotting it closed. Test that the pack is not too hot by placing it on the back of your neck. Use a blanket or towel as an insulating layer between the patient's skin and the heat source to prevent burns. Therapeutic ultrasound also effectively heats tissues up to 5 cm deep.
Superficial heat causes vasodilation, which improves circulation to the superficial tissues, increases tissue oxygenation and transportation of metabolites, and increases the rate of enzymatic and biochemical reactions to facilitate tissue healing.23,25,26 Heating soft tissues before stretching allows for greater extensibility of collagenous tissues. Maximum deformation occurs when tissue temperatures are maintained at 104 to 113 F (40 to 45 C) for a maximum of five to 10 minutes while applying a stretch force.26 Joint stiffness can be reduced and range of motion can be improved immediately after heat is applied.27 Do not apply heat in the early inflammatory phase of healing because swelling and edema may increase and result in further tissue damage.
Range of motion and stretching exercises
Range of motion and stretching exercises are vital activities to help improve joint motion and flexibility in pets after surgery or in patients with chronic orthopedic conditions. These exercises help prevent adhesions between soft tissues and bone, improve muscle extensibility, and prevent further injury to joints, ligaments, tendons, and muscles. True passive range of motion exercise is performed without muscle contraction and is facilitated by a therapist. Complete relaxation is rare in veterinary patients, so most range of motion exercises are active-assisted.
When performing range of motion exercises, make sure to have the patient in a quiet environment with little external stimuli. Use adequate support and padding to ensure patient comfort. Lightly stroke and massage the limb to be manipulated for a few minutes before range of motion exercise. The joint motion should be smooth and controlled, with steady motion through a comfortable range of extension and flexion. Ideally, the range of motion should involve only one joint at a time while the other joints assume a neutral position. The excursive movements should start small and increase until the endpoint of the range of motion is reached and the patient appears to slightly resist, indicated by tensing its limb muscles or turning its head toward the therapist to indicate early discomfort.
As patient comfort allows, encourage incremental increases in range of motion. With repeated range of motion sessions combined with some stretching at the end of motion, gradual increases in joint excursion may be expected over the course of several days to weeks. If much joint capsule fibrosis is present, however, the gains in motion may be less pronounced. Fifteen to 20 repetitions performed two to four times a day is likely sufficient. If you use true stretching, take the joint slightly beyond comfortable flexion, and hold it for at least 15 to 30 seconds. Then take the joint slightly beyond comfortable extension, and hold it for at least 15 to 30 seconds.
Special cases, such as articular fractures, physeal fractures, joint contractures, and immobilized joints, may require adaptations to routine stretching and range of motion protocols. Motions can graduate to a bicycling motion that can simulate or exaggerate a functional range of motion of all joints simultaneously in a limb. You can objectively assess improved range of motion by using a goniometer; be sure to record the angle measurements in the medical record. The unaffected contralateral limb can often be used as a reference. Improvements achieved with range of motion exercises will be slow and gradual. Safety is important, and it is recommended to have a handler restrain the patient during the initial sessions.
Therapeutic exercises are some of the most beneficial activities in a physical rehabilitation program.2-4,28-31 The degree of activity allowed depends on the surgical procedure performed, the condition of the tissues involved, and the stage of tissue healing.32 Relatively slow and low-impact exercises are initiated early in the postoperative period, and as limb use and patient comfort allow, more advanced exercises should be instituted. In all cases, the stage of healing and the strength of tissues must be considered so that excessive forces are not placed on healing tissues, causing tissue damage.
Common activities include assisted standing or walking, controlled leash exercises, treadmill walking, dancing, and wheelbarrowing, as well as sit-to-stand activities and stair climbing. Jogging, stepping over rails, pulling or carrying weights, playing ball, and exercising with therapy balls are also used.32 If patients are reluctant to use an injured leg, a syringe cap, coin, or marble can be taped to the bottom of the contralateral unaffected limb to help encourage use of the injured limb. Only use this stimulus intermittently because dogs will quickly become desensitized to its presence.
Assisted standing or walking
Exercising with therapy balls
Controlled leash walks
The main exercise for most patients in the early rehabilitation period is slow, short, controlled leash walks in which the patient is encouraged to achieve the most normal gait possible and use the affected limb to the best of its ability. Unfortunately, this exercise is often performed incorrectly; if a patient is led too quickly, the pet tends to skip with the affected limb or not use the limb at all. Slow walks increase stance time, flexibility, strength, and weightbearing. When an animal has mastered the slow walk, faster walks can further develop endurance, strength, balance, coordination, and proprioception.32
Walking inclines provides a low-impact method to strengthen the gluteal muscles as well as the cranial and caudal thigh muscles. The handler should be able to control the patient's head and may want to have it slightly raised to transfer additional weight to the hindlimbs or slightly lowered to transfer weight to the forelimbs, depending on the desired effect. It is best to start with small inclines and progress as the patient is able. Declines are also beneficial for forelimb muscle strengthening and limb use. Walking downhill may also result in increased hock, stifle, and hip flexion during the stance phase of gait because the limbs are advanced further cranially under the body as the dog walks downhill.32 Although walking results in some joint motion, the joints do not undergo their maximum range of motion.33
Dancing exercises allow additional weight transfer to the patient's hindlimbs. This activity increases weightbearing and challenges balance, coordination, and proprioception. Hip extension is greater with dancing backward as compared with dancing forward, and stance time is slightly increased with dancing. Assess a patient's range of motion before dancing so that a comfortable range of motion is not exceeded. The patient should be consistently using the affected limb at a walk before graduating to dancing. Muzzle the patient during initial sessions for handler safety.35
Another form of therapeutic exercise, wheelbarrowing, focuses on using the forelimbs. Place your hands under the dog's caudal abdomen and gently lift the dog's hindquarters off the ground a few inches while the dog walks forward. Lifting the animal higher does not seem to increase the peak force placed on the forelimbs. This is likely because of the decreased stride length when wheelbarrowing and the partial hindquarter support. While shoulder extension is increased with wheelbarrowing, the extension and flexion of the other joints are less than achieved with walking.35
Jogging may be initiated when weightbearing improves and there is decreasing lameness at a walk. Initially, patients may jog for 30 to 60 seconds two to four times a day. The amount of jogging may be increased 10% to 15% per week as long as lameness does not worsen.
Stepping over rails
Pulling or carrying weights
To enhance muscle strength, you can fit patients with a harness to pull weighted sleds to increase power and muscle tone. The amount of weight will vary depending on the animal's size and the design of the sled and harness. Initially, use only light weights. The animal's gait should change only slightly so that the sled is easily pulled over the desired distance. Heavier weights can be added after technique, strength, and endurance have been mastered with lighter weights. Similarly, strap-on weights may be placed on the affected limb to improve muscle strength and stamina. Weights are generally used two or three times a week. Again, it is important that the tissues subjected to increased forces be at the later stages of tissue healing, and patients should experience no pain or lameness after exercise.
Surface tension becomes an important factor to overcome if motion occurs at the surface of the water. A joint undergoes increased motion and work to break through the water's surface. In general, activities or motions that occur below or above the surface are easier than those occurring at the surface.32,43 The degree of resistance and buoyancy can be adjusted by changing the water depth. Surface tension is constant regardless of water depth but can be manipulated by changing the water level to the level of specific joints. Joint motion is altered as the height of the water changes because of the force necessary to break through the surface.
The collective benefits of aquatic exercises include assisted weightbearing; improved strength and endurance, cardiovascular fitness, range of motion, agility, balance, and proprioception; as well as decreased joint effusion and peripheral edema.38,42,44,45 Be sure to monitor the patient closely and ensure its safety. Floatation devices may be used, and a handler should be with the patient at all times. A patient that tires suddenly or experiences acute anxiety may require immediate attention.
Water temperature may also affect the cardiovascular response to exercise. Peripheral vasoconstriction occurs in people when they are submerged in cool water. Blood moves centrally, enhancing venous return, which results in increased stroke volume and decreased heart rate, increasing exercise efficiency.46 Blood pressure decreases slightly as well when working in cooler water. Because of these physiological effects of water temperature, it has been recommended that whirlpools and underwater treadmills be kept in the range of 78.8 to 82.4 F (26 to 28 C) to prevent heat-related complications.32 People who exercise in water that exceeds body temperature have higher cardiovascular demands that result in increased blood pressure47; this may hold true for dogs as well. One study suggests that slightly warmer water temperatures ranging from 86 to 94 F (30 to 34.4 C) had negligible influence on heart rate, respiratory rate, and rectal temperature.48
It is recommended to wait until after suture removal in an uncomplicated wound or incision before beginning aquatic therapy. Some clinicians believe that it is only necessary to wait until the wound is sealed by fibrin. The cleanliness of the water, urgency of the therapy, availability, and the patient's overall health may be factors to consider when determining when to initiate aquatic therapy. In conditions that necessitate early aquatic therapy before the wound is sealed, surgical sites can be temporarily covered and protected with water-resistant bandages, dressings, or wound sealants.
Neuromuscular electrical stimulation
NMES is a common modality used in physical rehabilitation. Most NMES units use surface electrodes to excite nerves, which in turn, stimulate muscles to contract. The depolarization of the motor nerve results in skeletal muscle contraction. Three types of currents are commonly used: continuous direct, continuous alternating, and pulsed currents. Most NMES devices are pulsed current, which consists of unidirectional or bidirectional flow of DC or AC electrical current that stops for brief periods. NMES is used in a variety of orthopedic and neurologic conditions, including cranial cruciate ligament pathology, fractures, and spinal cord trauma.49 The benefits of NMES include increased joint mobility, decreased joint contracture, decreased edema, improved circulation, improved muscle strength, and pain relief.2,32,50,51 Patients that should not receive electrical stimulation are those with pacemakers or seizure disorders. It should also not be used over a carotid sinus, a gravid uterus, or areas of thrombosis or neoplasia.
Therapeutic ultrasound is a deep tissue heating modality that may be an effective adjunct when rehabilitating musculoskeletal conditions such as restricted range of motion resulting from joint contracture, pain, and muscle spasm. It also appears to be helpful in stimulating tissue healing at lower intensities. The degree of heat production and penetration depends on the intensity, frequency, and duration of ultrasound and the size of the treatment area. The tissue type being treated is also an important factor. High collagen content tissues (bone, cartilage, and tendons) are affected more than those with less collagen (fat, blood vessels, and muscles).
The temperature of the tissues being treated can be raised 1 to 4 C (1.8 to 7.2 F) through the use of ultrasound. Some treatment protocols have been extrapolated from experimental studies done in people.52-54 One study that looked at the effects of various ultrasound treatments on caudal thigh musculature in dogs showed significant heating during 3.3 MHz ultrasound.26 Another study demonstrated a significant increase in hock flexion and tissue heating with 10 minutes of continuous ultrasound at 1.5 W/cm2 applied to the calcanean tendon.27 The effects were transient and suggest a need to apply other stretching and range of motion exercises immediately after heating. The skin over the target tissue must be clipped so that the ultrasound waves are not attenuated.55
PHYSICAL REHABILITATION FOR ARTHRITIC PATIENTS
Osteoarthritis is the most common cause of chronic pain in dogs, affecting about 20% of the canine population, or 10 to 12 million dogs in the United States.56,57 Sadly, more than half of these animals go untreated. Management of osteoarthritis must be viewed as a lifelong commitment. NSAIDs, used consistently, have markedly decreased the degree of discomfort associated with this debilitating disease.6,58-61 Drug therapy is the cornerstone of pain control. Because of the chronic nature of the disease, however, other interventions such as slow-acting disease-modifying agents, weight reduction, modified exercise programs, and physical rehabilitation should be incorporated into the treatment plan.4,62,63 You can think of the pharmaceutical therapy as an adjunct and a means by which a patient can undergo physical rehabilitation to ultimately reduce the amount and frequency of medication needed to maintain a comfortable lifestyle. NSAIDs alone can provide pain relief, but by themselves, they do not directly increase range of motion, muscle mass, or improve synovial fluid production and turnover. Improvements in these factors can be met through exercise and physical rehabilitation.
Keep in mind that older animals are often afflicted with other systemic conditions that may limit the amount or duration of medications they can tolerate.64-68 These patients require a thorough medical workup, including a complete blood count and serum chemistry profile and complete radiographic, physical, neurologic, and orthopedic examinations. Concurrent medical conditions must be treated to ensure the optimal benefits from physical rehabilitation.
Surgical options to treat, prevent, or delay the onset of osteoarthritis include stifle stabilization for cranial cruciate ligament rupture, surgery to correct patellar luxation surgery, triple pelvic osteotomy, joint arthrodesis, femoral head and neck ostectomy, and removal of a fragmented coronoid process, ununited anconeal process, or osteochondritis dissecans lesion. Physical rehabilitation modalities that often benefit arthritic patients include aquatic exercises; ground treadmill exercise; walking on level, incline, and decline surfaces; jogging; neuromuscular electrical stimulation (NMES); and therapeutic ultrasound; as well as massage and other modalities.
A wealth of information exists regarding physical rehabilitation in people, and more information is becoming available regarding its application in small-animal patients. It is important to be well-versed in the various modalities, the benefits associated with each and their indications and contraindications. Tailor rehabilitation programs to the individual because the severity of the condition varies in each patient. Many of the major cities in the United States have physical rehabilitation centers for pets. These facilities work closely with referring veterinarians to design and implement programs appropriate for each patient and its condition. It is not difficult to develop a rehabilitation program as a new service within a clinic or hospital. Therapeutic exercises require little financial investment and equipment. Like all disciplines in medicine and surgery, it is important to have proper training before beginning a rehabilitation program.
Greg Arnold, DVM
Darryl L. Millis, MS, DVM, DACVS
Department of Small Animal Clinical Sciences
College of Veterinary Medicine
The University of Tennessee
Knoxville, TN 37996
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