General Considerations When Using Assistive Devices for Ambulation

Assistive devices present unique challenges to rehabilitation clinicians because their design, fabrication, fitting, and the patient training are most often unique. Their successful use requires an accurate assessment of the biologic situation and the mechanical needs of the patient, requiring knowledge in the fields of orthopedics, rehabilitation, biomechanics, and prosthetics.⁶

Dogs wearing assistive devices should not be left unsupervised because they may damage their assistive devices or injure themselves. Assistive devices may be tolerated differently by individual animals. They may present risks when they are partially dislodged. As a general rule hair protects the skin from abrasions and hair should be left intact unless it interferes with the performance of an assistive device. In patients with long hair, the hair may be trimmed or clipped to enhance the fit of a device. New devices should be worn under controlled conditions (i.e., indoors and under direct supervision) and for limited periods of time, starting with a few minutes. Devices should not interfere with blood flow. If a device is too tight blood flow to an extremity will be decreased, potentially leading to a loss of tissue oxygenation or impaired venous drainage with resultant swelling of the lower part of the limb. Devices should be stable on the limbs to avoid problems created by constant friction, slippage, or rotation. The condition of the limb should be assessed each time the device is removed. Skin redness, bruising, or focal hair loss should be noted early and immediately addressed, by potentially modifying the assistive device (removing hard material responsible for skin wear or adding foam protection). Devices should be inspected for wear and damage and cleaned daily. Cleaning is especially important if there are any incisions, wounds, or open sores in contact with the assistive device.

Boots

Boots are used to protect pads and feet from abrasion or to provide support. They may be used in normal dogs to protect against abrasions created by rough surfaces; for example, for search and rescue dogs working in areas with broken glass. Sled dogs may wear fleece boots to avoid the accumulation of ice on their feet or to avoid skin lesions from ice crystals, for example (Figure 17-1). Boots may be used to avoid abrasions of the dorsal surface of digits and metatarsal bones of dogs with sciatic nerve palsy, provided that they have some residual hock function. If the hock is flaccid, a support orthosis may also be necessary to maintain the lower limb in a functional standing position. Similarly boots may be used to protect the dorsal surface of the manus in patients with palsy of the branch of the radial nerve that innervates the extensor muscles of the antebrachium (Figure 17-2). Because most radial nerve palsies or brachial plexus injuries also affect the triceps brachii muscle and therefore severely limit weight bearing by the entire forelimb, boots may not provide adequate support alone. Boots may also be used in dogs with degenerative myelopathy and other conditions that lead to scuffing of the feet. Boots must be lightweight, particularly for patients that have weak motor function because the added weight of the boot on the foot may further decrease limb use. Boots may be made of nylon mesh, cotton, fleece, neoprene, rubber, or other materials. They may have a rubber sole for increased traction.² They may be held in place through the use of straps or hook-and-loop fasteners. Bootstraps are most often placed immediately proximal to the distal portion of the metacarpal or metatarsal bones in order to secure the boot.

Orthoses, Including Sleeves and Braces

Orthoses are devices applied to limbs for support and protection. They are applied on limbs in order to assist or limit joint motion. The most common orthoses are used to restrict the excessive joint motion present in patients with ligamentous or tendinous problems, including patients with ruptures of their palmar fibrocartilage or common calcaneal tendon (Figure 17-3). Orthoses function by placing the limb segments proximal and distal to unstable joints in a foam-lined rigid shell. Orthoses are most often made of rigid thermoplastics. They may be lined with foam, fleece, or terry cloth. They are most often held in place with hook-and-loop fasteners. Orthoses may be commercially available premade or they may be custom made. Premade orthoses are affordable and are best suited to patients with normal anatomy and healthy skin (i.e., patients with rupture of the common calcaneal tendon). Custom orthoses are usually necessary in patients with abnormal anatomy (limb deformity, abnormal skin contours) and in very small or very large patients. They are generally based on a cast of the abnormal limb made by use of semirigid or rigid fiberglass or plaster of Paris. They may also be based on a computed tomography–based replica of the limb. Solid replicas may be made of cyanoacrylate-impregnated plaster, ABS plastic, or laser-cured photopolymers.⁷ Orthoses may be hinged to enhance their functionality.⁸ The hinges most often connect rigid shells placed around the pes (or manus) and the crus (or antebrachium). These hinges may be passive or dynamic (i.e., spring loaded). Passive hinges may be made of nylon or metal (Figure 17-4).⁸ Orthoses with passive hinges may enhance limb function because part or all of the motion of the tarsus (or carpus) may be maintained. Orthoses may have dynamic hinges that may be used to enhance the support of weak joints or to stretch contracted joints. Hinges are made dynamic by using springs embedded in the hinges or elastic bands.