Understanding The Impact Of Diabetic Neuropathy On Gait

Author(s): 
By Gordon Zernich, CP, BOCPO, Tomas Dowell, CPO, LPO, and Ronald B. Tolchin, DO, FAAPM&R

A Closer Look At The MLS/AFO Device
The orthotic-prosthetic lab at the Veterans Affairs Medical Center in Miami, directed by Tomas Dowell, CPO, LPO, developed another AFO option for sensorimotor diabetic neuropathy and drop foot.
The Miami Leaf Spring ankle-foot orthosis (MLS/ AFO) synthesizes elements of the PLS/AFO, the carbon fiber composite and metal types by combining a carbon fiber composite with a posterior leaf spring AFO that attaches to the heel area of the shoe by way of a metal caliper. The brace accesses the shoe heel posteriorly and is transferable to other shoes that have the caliper modification.
It is a safer AFO than the prefabricated carbon fiber composite or either type of hard plastic AFO, the posterior leaf spring or the one with dorsiflexion assist ankle joints. The MLS/AFO attaches to the posterior heel of the shoe to provide the leverage needed to correct the drop foot condition. It also keeps the sensorimotor neuropathic foot in an environment that is accommodative and dedicated entirely to its need. One may also include a custom molded arch support, a depth inlay shoe, or custom molded shoes with inserts for the insensate foot.
Another advantage of the MLS/AFO over the PLS/AFO is its performance. The laminated fiber carbon material of the MLS has a greater memory. In most cases, the plastic PLS/AFO stretches posteriorly because the PLS provides a very limited amount of plantarflexion at heel strike in the gait cycle. While that is initially good in regards to the gait cycle, it loses the memory of its original shape over time.
Accordingly, this AFO loses its original purpose to correct equinovarus through swing phase and keep the toe of the shoe from scuffing during the toe off phase of the gait cycle. In this regard, the MLS/AFO is safer and more effective. It not only provides more plantarflexion bias at heel strike than the PLS/AFO but it maintains its original shape for a significantly longer amount of time. It does not stretch.
In contrast, the metal AFO, either the single or double upright AFO, and the plastic AFO with dorsiflexion assist ankle joints provide no plantarflexion bias without a SACH modification to the shoe. One may add the same modification to the shoe heel of the MLS/AFO to enhance that bias to approach something closer to normal without compromising its purpose. Aside from this, most people would find the MLS/AFO more cosmetically appealing and slightly lighter in weight.
Another AFO that is comparable in function and design to the MLS/AFO is the VAPC clip-on type. It is prefabricated with a distal clip that clips on to the heel counter of a shoe. The device also has an anterior strap attached to the cuff that grasps the proximal, posterior calf. It also has a semi-rigid stay between the cuff and the clip that provides leverage to alleviate the drop foot condition. Its main detriment is that the clip will not reliably remain in place on the shoe. It “clips off” too frequently.

Final Notes
People with diabetic sensorimotor neuropathy and drop foot are in a precarious state of health. They require a meticulous approach to treatment and lifestyle changes to maintain hope for their well being. With these patients, there is a direct correlation with PVD and they have a heightened risk for foot complications such as loss of protective sensation, infection, ulcer, stress fracture to bone and joint subluxation.
Selecting the right type of AFO is important for restoring a more efficient, healthier gait pattern and reducing the risk of further complications. Some AFOs do this better than others. Ideally, it becomes a choice of which type restores the patient’s gait pattern in the most effective manner while minimizing the risk of further injury.
The MLS/AFO approaches this with its posterior placement to the shoe heel with a caliper modification isolated from the compromised condition of the foot. By virtue of its plantarflexion bias without the need for a SACH modification to the shoe, this AFO exceeds other AFOs in function and durability while maintaining its capacity to lift the foot and provide dorsiflexion assist throughout the gait cycle.

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