Current Concepts In Diagnosing And Treating Drop Foot

Start Page: 68

A Guide To Common Foot Drop Etiologies

• Hypothyroidism
• Lymphomas
(Hodgkin’s or non-Hodgkin’s)
• Guillain-Barré Syndrome
• HIV infection
• Cytomegalovirus infection
• Diabetes
• Megaloblastic anemia
• Intracranial tumors
• Brain lesions
• Tumors of the head and neck
• Trauma (direct injury)
• Antineoplastic drugs
• Spinal cord compression
• Direct peripheral
nerve invasion
• Autoimmunity
• Obesity or weight loss
• Idiopathic
• Local tumors such as ganglion or synovial cysts
• Nerve sheath tumors (schwannoma)
• Neurofibroma
• Bone tumors
• Postural (prolonged squatting, sitting or kneeling)
• Prolonged hospitalization
• Bed rest
• Internal surgery
(positioning on table)
• Ankle inversion/sprains
• Orthopedic (fibular fractures)
• Cast immobilization
• Tibial plateau repair/fracture
• Knee arthroplasty
• Hip surgery

Nicholas Romansky, DPM, Kelly Scollon-Grieve, MD, and James G. McGinness, CPO

   The primary purpose of the AFO is to increase dorsiflexion during swing phase, provide medial and lateral stability at stance, and possibly increase pushoff stimulation at the late phase of stance. An equinus contracture can decrease the maximum success of the AFO. Generally if the AFO is constructed for anterior use to the malleoli, it requires rigid immobilization, which one would employ in patients with upper motor neuron lesions or diseases, or post-cerebrovascular accident victims. If an AFO fits posterior to the malleoli and plantarflexes at heel strike, push off occurs to neutral during swing phase, providing dorsiflexion assistance. This results in a more natural, functional gait.

   The Foot Up Device (Innovative Technologies) is a simple AFO that works surprisingly well for partial drop foot.

   Years ago, the profession considered short leg braces, conventional or metal bracing attached to the shoes as the main solution for this gait dysfunction. A simple leg tracing, accurate measurements and a skilled orthotist are all that is necessary to construct this type of brace. Providing enough dorsiflexory assistance often required the use of a Klenzak ankle system in which dual spring mechanisms supply assistive forces that would overcome the resistance of the foot and ankle with no active dorsiflexion. One can modify all the patient’s shoes for removal of the brace, which allows easy shoe interchange.

   The advent of plastic bracing has been an especially significant addition for the treatment of drop foot. This process involves the orthotist taking a cast of the lower limb and carefully crafting a custom made orthosis. Various modifications, such as the addition of joint systems with these thermoplastic braces, can further customize the treatment of the individual patient’s condition. Tamerac joints simulate spring action and assist the foot and ankle in moving through a normal range of motion. Controlled ankle motion joints can limit joint motion to a specific degree range of motion. In treating drop foot and other mechanical problems of a weakened foot and ankle, another axiom is to brace only what the deficit demonstrates. Over-bracing, while well intended, may weaken other critically needed support systems of the ankle complex. If patients are always in the brace, then the leg muscles go unused and the muscles weaken.

   However, there are certain contraindications for bracing. Do not recommend plastic bracing if the patient has swelling of the lower extremities, insensate feet or compromised circulation. In our opinion, the condition of diabetes is also a valid reason for not prescribing a total contact plastic orthoses. Skin breakdown problems can be daunting and may ultimately lead to additional complications.

   The adaptation of new materials has provided us with a new option for the treatment of drop foot. Carbon fiber AFOs are very light and offer very good cosmesis. Although it may come in different designs, the single carbon upright extends from the foot plate and up the posterior portion of the leg. Using the stored potential energy principle at heel strike, the brace allows the foot to plantarflex as normal. When the foot is flat and subsequent to initiation of toe off, the brace coils and picks up the toe in time to offer clearance for swing through.

   The advantages of this brace are that it has minimal skin contact and is very comfortable for the patient to wear. The disadvantages include patient weight limitations as well as the need to avoid aggressive bending while hyperflexing, which may lead to brace failure.

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