A Guide To Preventative Offloading Of Diabetic Foot Ulcers
Single or multiple ray amputations or resections may result in a significant reduction of the weightbearing plantar surface. Custom-made multi-layer, multi-density insoles can help distribute pressure under the remainder of the foot. Patients with central ray resections usually need minor modifications to their molded insoles in order to ensure proper fit.19
Compared to a regular sneaker, extra-depth shoes have an extra vertical depth of 3/16 to 1/2 inch. Patients with mild deformities, such as hammertoes or bunions, are often unable to wear regular shoes due to their toes feeling crowded. When it comes to diabetic patients with pedal deformities, regular shoes are not good options. In this patient population, regular shoes may lead to the development of recurrent ulcerations due to a likelihood of neuropathy and a resulting inability to detect pressure points.
A regular shoe is also not a good option for the neuropathic patient with or without deformity because these patients require a custom molded insole. “Diabetic” shoes have enough extra depth to allow a custom insole for extra protection whereas regular shoes have trouble accommodating the custom insole. Custom insoles distribute pressure across the entire plantar foot, thereby decreasing shearing forces for the neuropathic patient. Different styles of insoles can be custom made from a mold of the patient’s foot in order to accommodate various deformities, including but not limited to hammertoe contractures, bunions and plantar foot ulcers.20
“Rocker sole” is a general term comprising a variety of rigid sole shoes but all these shoes unload pressure almost entirely at the forefoot. Research suggests that rocker soles effectively reduce peak plantar pressures in patients at risk for diabetic foot ulceration, particularly when one pairs these shoes with custom orthoses. Research has shown that this combination reduces pressure under the metatarsal heads by as much as 30 to 50 percent.21
The rigid sole limits foot movement at all joints, specifically extension at the metatarsophalangeal joints. In turn, this prevents movement of tissue at the plantar aspect and distributes forefoot load over a larger area.21 Patients with digital amputations, including the hallux, may benefit from the rocker sole devices. Following a digital amputation, the remaining adjacent digits naturally attempt to compensate for the deficit and this compensation can overload the remaining rays, increasing the risk of plantar foot ulcerations.19
The AFO with custom insoles is characterized by a rigid ankle design that patients can use for a variety of pedal problems including drop foot and ankle instability. Ankle foot orthoses provide the necessary decrease in strain rate required for maintenance and prevention of the diabetic foot ulcer.12 This is an excellent option when dealing with DFU prevention with either an underlying equinus component or multilevel foot amputations that require controlled ankle motion due to the loss of extensor tendon insertions.
The CROW boot not only serves to accommodate the Charcot foot but can also be a preventative offloading option for patients with a history of recurrent diabetic foot ulcers secondary to sensory neuropathy, pedal deformity or increased plantar pressure due to midfoot amputation.
Preventative offloading of the diabetic foot with amputation is difficult for several reasons. Amputation of the lower extremity leads to a considerable loss of weightbearing areas due to shortening of the foot, making footwear selection extremely important. One can provide adequate footwear under the condition that the remaining foot stump allows for proper weightbearing. The device needs to compensate for the loss of the weightbearing area, whether it is a custom shoe or prosthesis. Total contact of the foot is important in providing a snug fit of the stump with the prosthesis.20
So what does the future hold with regard to evolving our current offloading modalities for diabetic foot ulcers? How can we preserve a steady decrease in strain rate necessary for wound healing while improving patient adherence with offloading devices?