Nonsurgical Treatment of Foot and Ankle Conditions

Over-the-Counter Inserts

With the advances in materials used in shoe manufacturing, it is often possible to accomplish many of the functional goals of foot orthoses without the expense of custom-molded inlays. Several companies offer padded insoles for shock absorption and heel cushioning ( Fig. 5-2 ). Spenco, Viscopeds, Dr. Scholl’s, and other companies provide padded insoles and inlays that can provide relief for metatarsalgia and fat-pad atrophy. The addition of metatarsal supports, such as the Hapad longitudinal metatarsal pad on a cushioned inlay or in a shoe with a soft sole, can effectively relieve metatarsalgia or neuroma symptoms. Various heel inserts, such as Visco heels or Tuli heel cups, are often helpful in treating plantar heel pain. These devices are readily available through online medical supply websites and are often found in pharmacies and athletic shoe stores. Patients should be educated on their proper placement and use. Thin full-length OTC carbon fiber inserts are also available to limit metatarsophalangeal motion for conditions such as turf toe. These can be placed under the regular insert of an athletic shoe.

Once the patient has been evaluated and the desired intervention is chosen, the proper shoewear should be selected. In some instances, this may be all that is needed. If additional correction is needed, off-the-shelf items should be prescribed. The cost to the patient is considerable for custom foot orthoses, and more insurance companies now refuse payment for any orthosis that does not cross the ankle joint.

Custom Foot Orthoses

If the patient has a deformity or disorder that is not amenable to treatment with an OTC device, a custom orthosis may be appropriate. There are three general types of custom inserts: soft, semirigid, and rigid ( Fig. 5-3 ).

Soft orthoses are made with materials that may include (but are not limited to) polyurethane foam, polyvinyl chloride foam, ethylene vinyl acetate, and latex foam. These materials are used when the effect is cushioning, impact absorption, and reducing shear forces or friction. This is particularly important for use in the insensate foot. Also, soft inserts are beneficial for use with fixed deformities (such as those in rheumatoid arthritis), especially those with bony prominences. Soft materials can be used with semi-rigid material underneath to gain better mechanical control of the foot. These inserts are generally thicker than the rigid orthoses and may require the use of a shoe with a thick removable insole and increased depth, depending on the pathology.

Semi-rigid orthoses are the most commonly prescribed inserts. Unlike rigid orthoses, they offer shock absorption and some flexibility while still providing tensile strength and durability. They are used to support and stabilize flexible deformities and relieve pressure by weight transfer. Combinations of materials are often used; the inserts are generally thicker than rigid inserts and might require the patient to wear a deeper shoe. The materials used include leather, polyethylene compounds, closed or open cellular rubber compounds, cork, felt, and viscoelastic polymers. The advantage of this type of insole, as well as the soft custom insole, is the adjustability for altering pathology or to meet patient preference.

Rigid orthoses are used to decrease or control motion, such as in the treatment of arthritis of the midfoot or forefoot. The device stiffens the shoe and functions like a steel shank within the shoe. Patients with plantar prominences or significant fat-pad atrophy might find these too uncomfortable to wear. A rigid orthosis is often prescribed to block pronation but may be no more effective than a semirigid device and may be more difficult to tolerate. Furthermore, rigid orthoses offer no shock-absorbing properties and should be avoided in patients with impaired sensation. The materials used are thermoplastics or carbon fiber.

Custom orthoses are generally made from a foam impression of the feet of patients, in which the foot is pressed into the foam box in a corrected semi-weightbearing position or with a cast mold in a fully corrected position. New technologies are currently being investigated to assess the offloading capacity of foot orthoses.

University of California Biomechanics Laboratory Foot Orthoses

The University of California Biomechanics Laboratory (UCBL) insert is a custom molded foot orthosis, which controls flexible postural deformities by controlling the hindfoot. A full foot UCBL can assist with controlling forefoot abduction but is not as well tolerated as a sulcus or ¾ length orthosis. The orthosis should be molded with the heel in a neutral position. To work successfully, the orthosis must maintain purchase about the heel and prevent it from moving into valgus. It can also control forefoot abduction in the transverse plane better than an orthotic. By keeping the calcaneus in a neutral position, the orthosis stiffens the transverse tarsal joints, and pronation and forefoot abduction can be diminished. It may be necessary to add medial posting to the heel and forefoot to keep the heel out of valgus.

For fixed deformities, such as arthritis of the midfoot, a UCBL can decrease motion and reduce pain. The foot is molded in situ, and the polypropylene should have a relief over the area of bony prominence. The orthosis can be lined with a material for pressure absorption, such as polyurethane foam, and then the entire orthosis can be covered with a material such as polyethylene foam (Plastazote) for comfort ( Fig. 5-4 ).

Posterior Leaf Spring Ankle Foot Orthosis

The PLS AFO is designed to provide control of ankle plantarflexion in the sagittal plane by effectively limiting plantarflexion during swing phase and loading response. Made of either thermoplastic or carbon fiber, the PLS AFO is typically used to address dorsiflexion weakness in patients. It provides minimal control of the ankle in the coronal plane during stance phase as well as limited resistance to tibial advancement as the patient progresses from midstance to terminal stance. PLS AFOs can be custom fabricated to provide molded support and aid in the positioning of the foot; however, prefabricated devices with nonmolded footplates are more commonplace.

Articulated Ankle Foot Orthosis

Articulated AFOs are intended to permit motion of the ankle joint in the sagittal plane while providing coronal and transverse plane stability to the subtalar and transverse tarsal joints. A mechanical ankle joint is incorporated into the AFO allowing for dorsiflexion and plantarflexion range of motion to be unlimited or controlled utilizing stops. These orthoses are custom fabricated with molded footbeds that encompass the calcaneus to varying degrees and provide total contact support to the midfoot. Similar to functional foot orthoses, posting or wedging is often incorporated to accommodate fixed deformities or resist flexible varus or valgus deformities of the hindfoot and forefoot. Dorsiflexion assist joints can be used to improve toe clearance in swing phase and resist rapid plantarflexion during loading response in patients with foot drop. Dorsiflexion stops may limit stress transfer to the Achilles tendon, aiding patients with chronic tendinopathy.

Modern articulated AFOs are typically made of thermoplastic or carbon fiber; however, conventional metal and leather orthoses attached to a shoe are still being used in cases where fluctuating edema prohibits the use of a fixed volume device. They may also be utilized with neuropathic or dysvascular patient populations when skin integrity would be threatened with a more rigid design.

Solid-Ankle Ankle Foot Orthoses

Solid-ankle AFOs are custom fabricated to provide rigid support to the foot and ankle complex in all three planes of motion. Typically made of thermoplastic, these devices are prescribed when immobilization is necessary to improve stability and function during both stance and swing phases of gait. During swing phase, plantarflexion resistance in the sagittal plane and control of inversion and eversion in the coronal plane preposition the foot and ankle for initial contact. In stance phase, a solid-ankle AFO will resist plantarflexion during loading response and then will resist dorsiflexion and tibial progression from midstance to terminal stance. The ankle typically is set to neutral alignment, 0 degree dorsiflexion, unless range of motion is limited by pain or joint immobility. The ankle trimlines of the orthosis are kept anterior to the apex of the malleoli and may be further reinforced with corrugation of the plastic or carbon composite inserts to provide adequate stiffness and resistance to deforming forces in the sagittal plane during stance phase. Coronal and transverse plane control of the subtalar and transverse tarsal joints is achieved through customization of the AFO’s trimlines as well as the molded footbed of the orthosis. The solid-ankle AFO significantly restricts range of motion, particularly in the sagittal plane; this interferes with the smooth progression through stance phase, which is critical for a typical gait. Additionally, the impacts of a fixed ankle posture on knee position throughout stance phase should also be a consideration. Shoes incorporating a SACH wedge or rocker bottom modification can help mitigate some of the impacts of the orthosis on normal gait.

Arizona-Type Ankle Foot Orthosis

The Arizona-type AFO is a custom semi-rigid, thermoplastic AFO encapsulated within a lace-up molded leather gauntlet. This name is in reference to the patented Arizona Brace made by Arizona AFO. This orthosis resists ankle plantarflexion during loading response and ankle dorsiflexion from midstance to terminal stance phase. The leather ankle gauntlet wraps around the anterior aspect of the leg providing a broad surface area to further restrict dorsiflexion range of motion in late stance. Additionally, the subtalar joint is immobilized in the coronal plane. The molded footbed, which provides midfoot support, traditionally extends to the metatarsal heads, allowing for extension of the metatarsophalangeal joints in terminal stance and pre-swing. This AFO’s primary application is to address posterior tibial tendon dysfunction (PTTD) by stabilizing the hindfoot through three-point fixation similar to a short-leg cast. It has the advantage of being shorter than a standard molded AFO, and the padded leather gauntlet may yield better comfort and patient acceptance. As with most ankle foot orthoses, cosmesis is a concern for many patients since the device is often visible and may be considered to be bulky. A comfort lace-up or Velcro closure shoe is required for this type of orthosis. Furthermore, patients with limited hand function, such as from arthritic fingers, may have difficulty with the numerous laces required to don and doff the Arizona brace. Patients should be counseled appropriately as to the advantages and disadvantages of all orthotic devices.