Orthotics and prosthetics in veterinary rehabilitation

In veterinary school, I was taught that animals do well on three legs. While it is true that many of them adapt amazingly well, this is functional adaptation—not necessarily the highest quality of life. During the time I spent in general practice, I came to expect—even accept—that limited mobility, limb breakdown and chronic neck or back pain were consequences of limb amputation. I thought that cast-related wounds were unavoidable and that dogs with cranial cruciate ruptures would be uncomfortable for the remainder of their lives without surgical stabilization. But I was seeing dogs with mobility issues every day, and it seemed there should be something more I could do to help them run, chase balls and harass squirrels again.

Rehabilitation moves to the forefront

Over the past decade, there has been a tremendous increase in our understanding of physical fitness for both people and animals. We now know that optimal movement and mobility can significantly impact the physical and mental health of our patients. Canine rehabilitation has moved to the forefront of modern veterinary medicine with the advent of the American College of Veterinary Sports Medicine and Rehabilitation. With this new paradigm comes the idea that using mechanical appliances to improve the mobility and functionality of impaired patients is no longer the purview of human medicine alone.

Veterinarians have a history of creating assistive devices from things at hand, using everything from plywood to low temperature thermoplastics and aluminum rods to PVC pipe. As our understanding of the intricacies of quadruped mobility and biomechanics has grown, so have the variety and sophistication of these devices. Now they incorporate veterinary-specific hinges, composite plastics, titanium, carbon fiber and specialty foam liners. Veterinary orthotics and prosthetics (V-OP) is evolving into a new specialty.

Orthoses (braces) are defined as any medical device attached to the body to support, align, position, immobilize, prevent or correct deformity; assist weak muscles or control and improve function. They are not a replacement for surgery, but complementary. Orthoses can be used as preoperative or postoperative solutions or even as alternatives to surgery. In cases in which surgery must be delayed, they can provide interim support, protect a limb and minimize disuse atrophy. Postoperatively, orthoses can provide a safe, effective and dynamic alternative to casting. Orthoses can also be used when surgery is not an option such as in patients that are poor candidates for anesthesia or have comorbidities or advanced age or if finances are an issue for the owner. These patients are seen daily in veterinary clinics everywhere, and until the advent of V-OP, there were no options to offer them.

The structural consequences of a missing limb or limb segment are now being recognized, in part through the efforts of rehabilitation therapists who understand the biomechanics of locomotion. Reestablishing a quadruped structure should be the goal whenever possible. Prostheses, like orthoses, are readily accepted by veterinary patients with congenital limb deformities as well as by those requiring an elective level amputation. In human medicine, amputation at the hip for a catastrophic ankle injury would be unthinkable, but elective level amputation is a recent development in veterinary medicine. Why amputate an entire limb if only the distal segment is not salvageable? When a friend of mine lost the lower half of her leg in an accident, her surgeons did everything they could to save her knee. Why don't we do this for dogs? Lack of awareness or knowledge? These reasons are no longer tenable in this era of V-OP.

There are many advantages afforded by orthoses and prostheses. Simply put, they offer treatment options where none existed before. They can improve quality of life and functional independence, preventing premature decisions to euthanize. Patients can return to an active lifestyle that curtails obesity and associated comorbidities. Biomechanics can be improved, decreasing secondary or compensatory pain. Cast-related wounds with associated pain and expense can be prevented. This is particularly notable given that in a recent retrospective study,1 cast-related injuries were shown to occur in 63 percent of casted patients at a cost that in some cases actually exceeded that of the original orthopedic procedure.

Rehabilitation and V-OP: A team approach with a precedent

When people receive a knee or ankle orthosis, they work with a physical therapist to learn how to use the device properly. They find out how to protect the injured joint and do exercises to increase proprioception, strength and range of motion. There is a common misconception that orthoses are static, causing muscle atrophy, diminished joint range of motion and dependence on the device. This is just not true of modern dynamic orthoses. These devices are hinged and actually promote muscle development, normalize range of motion and assist in balance and coordinaton—all by stabilizing an unstable limb segment.

V-OP has created a new challenge for veterinary rehabilitation therapists: assistive device-specific rehabilitation. Animals adapt and will learn ways of ambulating in an orthosis or a prosthesis. However, using the human experience as a precedent, it is reasonable to suggest that patients are more likely to return to highest-level function faster with professionally guided assistance. Veterinary patients present a seemingly endless variety of injury types and an exceptional drive to recover. For the creative rehabilitation therapist this is an exciting area for professional growth.

The V-OP evaluation

A V-OP patient evaluation must be thorough enough to provide a specific device prescription. At least five separate examinations should be conducted to fully define the presenting deficit, characterize biomechanical implications, identify complicators or co-morbidities and diagnose all primary and secondary pain generators. These examinations should include a general wellness examination in addition to orthopedic, myofascial, biomechanical and neurologic examinations. The case must be understood from the standpoint of the following issues:

• Injury or deficit

• Functional and mechanical impairment resulting from the injury or deficit

• Comorbidities or complicators

• Lifestyle, environment, family dynamics, sport or activity

• Goals and intended outcome as defined by the client and veterinarian

• Alignment of goals with the proposed orthotic or prosthetic device.

Once a plan is developed and the device is designed, the next step in creating a custom orthosis or prosthesis is cast molding of the limb. This step is critical for optimal fit and correct function of the device. Casting the limb in a thin layer of fiberglass tape requires a bit of artistic acumen and a clear sense of device purpose. The limb is cast in the properly aligned position. This fiberglass cast is used to create a plaster model from which the custom device will be fabricated.

Manufacturing requires skilled modification of the model by hand to build plaster reliefs, which accommodate limb topography and create appropriate corrective forces when the completed device is applied to the limb. The modified plaster model is the structure upon which a thermo-plastic shell is vacuum formed. The shell is then hand cut, trimmed and ground to the final shape, or shapes, in the case of a multishell device. A custom foam lining designed to change color with abnormal skin contact is added along with appropriate hinges, straps and pads. The final product is typically completed in about a week at an average cost of $600 to $850, depending on the components required.

V-OP is a hands-on specialty, so each case should be managed carefully from diagnosis to device orientation using a cohesive team approach. The ideal team includes the pet owner, the family veterinarian, a certified rehabilitation therapist and a V-OP specialist skilled in custom design, fabrication and fitting of devices for quadrupeds. This growing specialty has made options available to animals with mobility issues that did not exist when I was in general practice. As veterinarians, we owe it to our patients and their owners to be familiar with orthotic and prosthetic devices and how they can be used to improve the quality of an animal's life. The squirrels probably won't appreciate our efforts, but the dogs that can chase after them again certainly will.

Dr. Mich is a faculty member of the Canine Rehabilitation Institute in Wellington, Fla., and co-owner and medical director of OrthoPets Center for Animal Pain Management and Mobility Solutions in Denver, Colo.

REFERENCE

1. Meeson RL, Davidson C, Arthurs GI. Soft-tissue injuries associated with cast application for distal limb orthopaedic conditions. Vet Comp Orthop Traumatol 2011; 24(2): 126-131.