Current Concepts In Diagnosing And Treating Drop Foot

Author(s): 
Nicholas Romansky, DPM, Kelly Scollon-Grieve, MD, and James G. McGinness, CPO

   Drop foot can occur prior to lumbosacral spine surgical nerve decompression as a result of nerve decompression or because of an intraoperative complication of decompression. The etiology in these cases revolves around acute and chronic lumbar degeneration.4 Typically, the result of surgical nerve decompression depends on the acute or chronic nature as well as magnitude and duration of compression of the L-S spine. If surgery occurs, most improvement occurs six weeks postoperatively.

   Drop foot can occur following hip and knee replacement with damage and localized hematoma to the sciatic nerve and its branches. This is especially the case if bleeding occurs at the operative site.

   For a full list of drop foot etiologies, see “A Guide To Common Drop Foot Etiologies” at right).4-9

Pertinent Pearls On The Workup And Diagnosis Of Drop Foot

The workup of a drop foot should include a thorough neurologic exam to rule out any more serious central or primary causes of the drop foot. This includes motor strength testing and sensation and reflex examination of all limbs, including assessment for pathologic reflexes such as Babinski, Hoffmann’s and clonus reflexes.

   Physicians must access the entire clinical picture through the use of laboratory studies and other diagnostic modalities. Nerve conduction and electromyographic studies are an important extension of the neurologic examination as they can help zero in on the local site of injury, establish the degree of damage and predict the degree of recovery. Laboratory studies to evaluate for a metabolic or toxic cause may be indicated if there is no trauma or obvious cause for the drop foot. The following tests are useful: fasting blood sugar, hemoglobin A1c, erythrocyte sedimentation rate, C-reactive protein, serum protein electrophoresis, blood urea nitrogen, creatinine and vitamin B12 levels.1

   Imaging is also important in establishing the cause of drop foot. If there is trauma to the area, plain films of the tibia and fibula are indicated to determine if there is any bony injury. One may employ magnetic resonance imaging (MRI) to help evaluate for local tibia/fibula injury, brain injury, spinal cord pathology or nerve root impingement. Ultrasound evaluation of the peroneal nerve may be useful in assessing for a focal entrapment around the fibular head.1

   One must take numerous factors into account when deciding on the treatment approach for the individual with drop foot. The etiology, chronicity, prognosis, distribution, location, severity and medical comorbidities are critical factors. Treatment modalities can consist of nonsurgical, surgical and brace assistance, or any combination of the above.

How Effective Are AFOs And Bracing?

Bracing with an AFO and physical therapy is useful in all causes of drop foot to assist in ambulation and prevent contracture of the ankle plantar flexors. Clinicians may use conventional AFOs for those who would benefit from minimal skin contact. These patients would include those who have lower limb swelling, circulation concerns, and/or insensitivity.

   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.

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