Physical Therapy in Veterinary Medicine

Robert Taylor United States

There is a lot of interest in canine physical therapy and rehabilitation and courses are being offered at many of the major meetings. There is one certification process in motion, which will be sanctioned by several universities, and active canine physical therapy-related research is happening. What has triggered this interest?

There are several factors to consider:

1.   Public demand.

2.   Emergence of the working dog; with need to return to previous level of activity.

3.   Demonstrated efficacy in other species (man).

4.   Increased sophistication in veterinary surgery.

5.   Animals are living longer.

6.   Adds value to veterinary services.

7.   Potential source of veterinary income.

8.   Rewarding to veterinary staff, owner and animal.

In the recent past, there was little attention paid to post operative care and many animals were lost to follow-up following suture removal. This, coupled with the notion that the animal would use the limb when it felt �good� and the reluctance on the part of veterinarians to urge early mobility, were factors that limited the use and concept of physical therapy. In spite of recent advances, there are still veterinary surgeons that routinely immobilize their post-operative cruciate patients for four to six weeks, and this is often done with casts, braces, or splints. Early motion has been shown to be efficacious in hastening recovery and limiting the effects of disuse on bone, cartilage, periarticular soft tissue, ligaments, and tendons.

The goal of physical therapy and rehabilitation is to return the affected part and the animal to full function. We first began our Physical Therapy and Rehabilitation (PTH) program working with racing Greyhounds. Owners and trainers were reluctant to invest the time and money to allow us to repair their injuries unless we could insure that they would return to the track and perform at their previous level or better. While we were not always successful, we learned the value of early and appropriate PTH.

One current challenge is to prove that PTH is as meritorious in the dog as it has been in man. There are many studies done in man demonstrating the value of PTH on earlier recovery, resumption of lifestyle, return to athleticism, and enhanced quality of life. There have been studies in animals, notably Johnson�s work on early use of electrostimulation; Levine and Millis� work on goniometry, range of motion and ultrasound; Steiss on ultrasound; Adamson on photon therapy and the underwater treadmill; to mention only a few. The recent interest will only stimulate new areas of investigation and research.

PTH measures should be included in every post-surgical plan. The benefits of PTH include:

1.   Increased blood flow and lymphatic drainage to the injured area.

2.   Early resolution of inflammation.

3.   Increased production of collagen.

4.   Prevention of periarticular contractions.

5.   Promotion of normal joint homeostasis.

6.   Promotion of normal joint biomechanics.

7.   Prevention or minimize muscle atrophy.

8.   Positive psychological effects for the animal and owner.

There are two distinct intervals in the recovery process where PTH can be useful to facilitate full post-surgical recovery and return to function. For every one patient recovering from a traumatic injury and/or surgery there are ten patients who could benefit from PTH and these patients include those with obesity, degenerative joint disease, tissue atrophy and residual neurologic disease. For purposes of this paper, we will address the needs of the post trauma/surgery patient.

PHASE ONE

Phase 1 activities begin the day of surgery and typically involve icing, passive range of motion, and early wound mobilization. This period begins with the traumatic injury and or surgery and encompasses the inflammatory phase and early wound healing that occurs in the first three to four weeks. The goal of PTH during this time is to minimize inflammation and pain, preserve joint range of motion, and to prevent or further minimize muscle and soft tissue atrophy.

PHASE TWO

Phase 2 activities begin as inflammation is resolving and healing begins to be the predominate theme in the wound. It is very important to combine phase two activities with the temporal aspects of wound healing. By that, we mean applying appropriate stresses to healing tissues so as to optimize their healing but not so much that the biomechanical stability is threatened. Ideally, the phase two activities should parallel the gradual increase in tensile strength observed in the wound. If one is too aggressive with PTH during this period, failure can occur; conversely, if one lags in PTH activities, the goal of early return to function is not accomplished.

RESPONSE OF CONNECTIVE TISSUES TO DISUSE AND IMMOBILIZATION

In order to better understand the needs of PTH during recovery it is appropriate to understand the way connective tissues respond to immobilization and disuse.

Skeletal muscle changes from reduced weight bearing and loading:

1. Type 1 muscle fiber and muscles with a large population of type 1 fibers show perpetual atrophy. These include the extensor muscles and the antigravity muscles.

2. The loss of muscle strength is caused by not only atrophy but biochemical changes in the sarcoplasmic reticulum.

3. Normal dogs undergoing surgical transaction of the cranial cruciate ligament and immediate stabilization undergo early atrophy of the affected limb muscles, which continues for at least five weeks. The atrophy is most significant in the quadriceps, biceps semitendinosus, and semimembraneous muscle groups.

4. The presence of fast twitch proteins in slow twitch muscle fibers indicating a biochemical conversion of these fibers.

Ligament changes to immobilization:

1. Stress reduction is detrimental to the mechanical, biochemical and structural properties of collagen and ligaments. Following five weeks of immobilization of the knee of primates, there was a 39% decrease in maximum load to failure (Noyes).

2. Stress reduction in a rabbit femur ligament tibia model produced a 69% decrease in load to failure
(Woo et al.).

Cartilage changes associated with reduced weight bearing and immobilization:

1. Immobilization creates degenerative changes in the articular cartilage. There a gradual reduction in proteoglycan content of the cartilage, thinning of cartilage, a decrease in proteoglycan production, and loss of subchondral bone. Immobilization of a limb in extension results in increased muscle contraction and changes similar to those seen in osteoarthritic cartilage including osteophyte formation, fibrillation of cartilage, pitting, and erosion of articular cartilage.

Bone changes associated with immobilization and disuse:

1. Immobilization causes decreased bone formation, increased bone absorption and trabecular bone is more affected than cortical bone. The effects of immobilization are most pronounced on distal bones.

2. Immobilization (stages of response):

a.   �Stage 1: six weeks of immobilization, quick loss with near full recovery requiring 8�12 weeks.

b.   �Stage 2: 12�32 weeks of immobilization slower loss but longer recovery.

c.   �Stage 3: Greater than 32 weeks of immobilization loss maintained at 30�50% of normal.

WOUND HEALING

Those involved in PTH must be students of wound healing. For example, it is important to know that tendons subjected to surgical repair only have 40% of their tensile strength at four months. The reader is referred to a standard text for a more in-depth discussion of the temporal aspects of wound healing. It is important that the PTH activities parallel the acquisition of wound strength during the period of immobilization and healing.

PTH Modalities

Modalities that are currently used in veterinary PTH include therapeutic ultrasound, neuromuscular stimulation, cryotherapy, heat therapy, massage, therapeutic exercise, aquatic therapy, and passive range of motion activity. Each of these modalities will be discussed in the lecture portion of the presentation.

Ultrasound

Therapeutic ultrasound is a commonly used modality in PTH and has been shown in clinical and scientific trials to increase collagen extensibility, enhance collagen remodeling, enhance collagen production, increase heat in deep tissues, increase blood flow, increase range of motion, reduce pain and muscle spasm, and accelerate wound healing. Therapeutic ultrasound is produced by applying an electric current through a piezoelectric crystal causing it to vibrate at its resonance frequency. These oscillations of the crystal cause pressure waves to be emitted and these are subsequently absorbed by the tissues. The two most commonly used US frequencies are 1.0 MHz and 3.3 MHz. The 1 MHz penetrates more deeply and is used for heating tissues from 2�5 cm in depth. The 3.3 MHz head is used to heat tissues to a depth of 1�2 cm. With the 3.3 MHz head maximum heat is generated at the 2 cm level. In most cases, the amount of time tissue temperatures remain elevated is short (within 10 minutes).

The thermal effects of US include:

1.   Increased metabolic rate of tissues.

2.   Increased blood and lymphatic flow.

3.   Increased extensibility of collagenous tissues (tendons, scars, muscle sheaths, joint capsules, ligaments).

4.   Decreased pain and muscle spasm.

The non-thermal effects of US are:

1.   Increased cell diffusion and cell membrane permeability.

2.   Increased production of collagen and hydroxyproline.

3.   Increased fibroblast proliferation and activity increases GAG synthesis.

Dosage

The rate at which the US energy is delivered per unit area is expressed in Watts/cm². Intensities of 1�2 W/cm² are used in areas that have a lot of muscle (such as the thigh) and less intensity is used for other areas (0.5�1.0 W/cm²). Continuous US is best used to heat tissues, and if available, the pulsed delivery is used when the non-thermal effects of US are desired.

Coupling Agent

A coupling agent is needed to connect the US head with the skin in order to maximize transfer of the US energy in top the tissues. Water-soluble gels are advisable.

Treatment time and frequency

It is important that the hair be clipped over the desired treatment area. Steiss has shown that the presence of hair interferes with the absorption of the US energy and it is possible to burn the skin if this is not done, furthermore the hair absorbs the US energy and little is available to heating deeper tissues. The time necessary to treat an area depends on the size of the treatment area and the size of the transducer head. One can estimate how many transducer heads fit into the treatment area and for every two heads allow five minutes. We typically do daily or every other day treatments.

Electrical stimulation

The use of electrical stimulation to stimulate a peripheral nerve to cause the desired effect is called neuromuscular stimulation. Electrical stimulation is a commonly used modality in PTH and been shown efficacious in:

1.   Increasing muscle strength.

2.   Improving muscle tone.

3.   Increasing range of motion.

4.   Pain relief.

5.   Muscle re-education.

6.   Reducing muscle spasms.

Current types

AC current is commonly used for muscle stimulation and reeducation delivered in a pulsed format. Medium frequency polyphasic current is called Russian stimulation. The device is connected to the patient via a pair or more electrodes. They should be flexible, offer low resistance, and may be trimmed to custom fit the part of the body where they will be used.

Treatment parameters

Amplitude is the size of the current waveform. Ramp is the time from the beginning of the phase to increase in amplitude from the zero current baseline to the peak amplitude. Waveform, the shape of the visual representation of pulsed current, can be symmetrical, asymmetrical, balanced, unbalanced, monophasic, or polyphasic. Frequency, the rate of oscillation in cycle/second, expressed as pulses/sec. on/off time, indicates the amount of time the stimulator is delivering current compared to the rest period between contractions.

Current Parameters for strengthening:

Millis and Levine recommend a frequency of 25�50Hz/sec with a biphasic waveform with pulse duration of 150�250 microseconds with a 2�4 second ramp time.

THERAPEUTIC EXERCISE

Of all the modalities used in Canine Physical Therapy, therapeutic exercise is often the most effective in cost and achievement. Therapeutic exercise (TE) can be utilized in every clinic and its use and implementation is only limited by one�s imagination. TE can be used to preserve ROM and muscle mass and to challenge healing tissues during recovery.

An important factor to acknowledge is the need to match the specific injury/and or surgical repair with the appropriate exercise. We know from clinical/research data in animals and man that following cranial cruciate loss/repair the quadriceps, biceps and semimembranosus under go significant atrophy. When developing a TE plan for a postoperative cruciate patient, we concentrate specifically on these muscles. In man, ability to achieve full extension of the knee is a desired endpoint, however, due to the functional angle of the dog�s knee, this is less important.

Listed below are post-operative cruciate repair TE exercises:

1.   Sit/stand.

2.   Corner stands.

3.   Figure of 8/circle walks.

4.   Wheel barreling.

5.   E-stim. of hamstrings/quads.

6.   U.S./stretching of hamstrings, quads.

7.   Initial decline treadmill followed by incline treadmill.

8.   Leg weights.

9.   Enhancement of proprioception�unbalancing.