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Call It a Symptom

Instead of a diagnosis, foot drop usually results from a neuromuscular disorder-but treatment can be tricky.

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Physical therapists old enough to remember go-go boots may also recall unexpected cases of foot drop caused by the fashionable footwear. Fortunately, designers have largely abandoned the elastic boot band that put pressure on the peroneal nerve, which weakened the tibialis anterior muscle, and led to the troublesome condition.

Steven Huber, PT, CKTI, uses the go-go example to illustrate the fundamental idea that foot drop, sometimes referred to as "drop foot syndrome," is not really a diagnosis, but is instead a symptom. Neuromuscular diseases such as multiple sclerosis, ALS and Guillain Barre are often the culprits, but traumatic injuries can also be the cause.

As owner of Huber Associates, a private physical therapy practice in Auburn, ME, Huber has seen many cases of foot drop. Due to the sheer variety of maladies that lead to the condition, he views it as one of the trickier ailments. "A very thin lady who crosses her legs for an extended period of time at the knee may get a temporary tingling down her foot," said Huber, who is also an orthotist. "The pressure on the peroneal nerve could lead to peroneal nerve palsy, and a permanent version of that would be foot drop."

Huber explained that injuries to the knee and back can also affect the nerve that innervates the tibialis anterior; thus, people can get foot drop from a herniated disk. "The most common causes would probably be stroke, back injuries and peripheral nerve injuries," said Huber.

Gad Alon, PT, PhD, associate professor at the University of Maryland School of Medicine, Baltimore, agrees with Huber as to the primary causes, while adding polio and vascular problems to the list. Dr. Alon has treated cases that stemmed from all of these conditions, and points out that treatment and cause are inextricably linked.

"Cause often dictates to what degree the patients are likely to recover," said Dr. Alon, who teaches in UM's Department of Physical Therapy and Rehabilitation Sciences. "If there is damage to the peripheral nerve that goes to the muscles and the nerve is not repaired surgically, or if the dorsiflexors were severed and not repaired, then patients will likely have drop foot for the rest of their lives."

It doesn't take an expert to spot the drop-foot gait, exemplified by a foot that is pointing down as it goes through the swing phase. Sufferers make awkward adjustments to get to the stance phase and avoid hitting the toe and tripping.

"Treatments are designed to prevent the foot from dropping downward during the swing phase of gait so you can clear the floor," explained Huber. "Some people would simply elevate the heel on that side, and then the foot's already plantar flexed. Other people would use a type of brace that does not allow the foot to drop down."

While some foot drop cases can be readily predicted, others take clinicians by surprise. Huber recalls one patient who had a back injury with a disc herniation and severe scoliosis. The man had surgery and woke up with foot drop.

"We put him in a stretching program to stretch out the heel cord," said Huber. "We put him into a plastic ankle foot orthosis (AFO) called a posterior leaf spring, and then worked on a strengthening program and a home exercise program. After a year, he was out of the brace and functioning."

Some cases are transient and some are more permanent, so determining the natural progression to eliminate the problem is the first priority. "Often you'll see bracing to prevent the immediate situation of the foot dropping down," said Huber. "That is usually an AFO, followed by strengthening and stretching exercises, because patients lose strength in the tibialis anterior, which is the muscle that lifts the front of the foot up as the gastroc pushes it down. What happens is the back gets tight, and that inhibits the front from working."

Huber believes that allowing time to work its healing ways is usually not the best treatment, primarily because the danger of falling is too great. "To compensate for foot drop, the person does a high steppage gate, raising his knee higher to clear the foot during swing phase," he said. "That can also make back issues worse."

Low-Tech and High-Tech

New information about electrical stimulation braces is building each year, and Huber believes the devices work.

Surface electrodes on the skin activate the electricity, while timing of the stimulation is determined by a tilt sensor. "Patients wear a calf band over the peroneal nerve," said Huber. "When patients unweight the leg, or the device picks up the vectors moving, then it stimulates the nerve and the muscle works during swing phase. This is a viable alternative that's really been advancing in the last 4 to 5 years. It is still not covered by most insurance, and it costs around $6,000. I am writing an appeal right now on one of them."

According to Dr. Alon, the simplest device is similar to a rubber band that connects the shoe to above the ankle, and there are commercial units that work in this manner. Especially if expense is an issue, this low-tech approach may do the job. However, most of the time, patients will have additional issues, and higher-tech equipment will be necessary.

Dr. Alon recently completed a one-year follow-up report for research he did on a sophisticated functional electrical stimulation (FES) device designed specifically for drop foot. As of today, the device has been deemed "expensive" by CMS, although some private insurances have started to pay for it.

The wireless system is easy to take on and off. "There is smart sensing in the system that automatically knows when you sit and don't need to stimulate," said Dr. Alon.

The good news is that successful healing is often possible without electronics. About a month ago, Huber treated a stroke patient with complete foot drop who has since made a full recovery. "He did not have to be braced," said Huber. "We did a simple strengthening program for him. There are also functional taping techniques with kinesiology tape that are used to facilitate those muscles as well."

Stimulate More Muscles?

Last year, David G. Embrey, PT, PhD, Children's Therapy Unit, Good Samaritan Movement Laboratory, Puyallup, WA, published research (Dr. Alon co-authored) that documented foot drop treatment efforts aimed at stimulating not just the dorsiflexors, but also the plantar-flexors. The investigators concluded that working on muscles that pull the foot up (dorsiflexors), as well as those that push the foot down (plantar-flexors), could lead to better outcomes. Another group at the University of Delaware is doing similar work, and new research will likely continue to target more muscle groups for stretching, strengthening and FES.

Dr. Alon is working with a PhD student to assess FES in the realm of pediatric cerebral palsy. "CP is complex, and can affect the entire body, not just one side," he said. "I advised the student to incorporate the treadmill into her training with children. Incorporating FES with other types of intervention, such as treadmill training and other technologies including robotics and video games, is something we'll see in the near future of foot drop treatment. If you want to maximize outcomes for any given patient, no one intervention-including FES alone-can maximize performance. It must be a combination."

Gaining experience with these combinations is admittedly a difficult task, since treating what amounts to "just the foot-ankle complex" of foot drop is ultimately a small issue for PTs in daily practice. Dr. Alon contends that even therapists who specialize in neurological problems are not fully aware of the electrical stimulation options. "They never got adequate FES education, and too often do not know how, why or when to use it," said the 31-year teaching veteran.

Greg Thompson is a freelance writer in Fort Collins, CO.





     

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