7.1 Offloading and Protective Footwear

Why plantar diabetic ulcers fail without offloading

A diabetic foot ulcer (DFU) on the plantar surface is a mechanics problem as much as a moisture or infection problem. Peripheral neuropathy lets the person keep walking on a peak-pressure spot. Each step loads the first or second metatarsal head, the hallux, or a collapsed Charcot midfoot. Vertical pressure and shear between bone and insole saw the tissue from the inside. Independent OpenExamPrep teaching for Certified Wound Care Nurse (CWCN) candidates treats offloading—reducing peak plantar pressure and shear at the ulcer—as a first-order intervention, not an accessory after a dressing is chosen.

Peak pressure is not evenly spread. Forefoot ulcers cluster under the metatarsal heads and hallux. Midfoot ulcers often sit under a rocker-bottom Charcot foot. Heel ulcers in a bedridden person are usually pressure injuries from the mattress, not walk-on neuropathic ulcers, so a walking boot that unloads the forefoot will not float a heel on a stretcher. Match the device to ulcer location and to whether the person is walking, sitting, or lying.

Total contact cast: gold-standard overview

For many non-infected neuropathic plantar DFUs with adequate perfusion, the total contact cast (TCC) remains the classic gold-standard offloading device. A well-applied TCC spreads load over a large contact area, shortens stride, and—because it cannot come off for a trip to the mailbox—removes the adherence failure that sinks removable walkers. The 2023 International Working Group on the Diabetic Foot (IWGDF) recommendation is slightly broader: a non-removable knee-high device is first choice, and that class includes either a TCC or a prefabricated removable cast walker (RCW) rendered non-removable. Know both facts for this exam: TCC is the traditional gold-standard custom device, and wrapping a walker so the person cannot easily remove it is an evidence-based equivalent when casting skill, time, or cost is the barrier.

Full TCC application, padding maps, windowing, serial recasting, and the complete how-to contraindication list belong in Chapter 13. This chapter only sets the decision: if the ulcer is plantar and neuropathic, infection is absent or only mild, and the foot is adequately perfused, plan a non-removable knee-high device rather than a postoperative shoe plus a lecture.

Reasons to hold or avoid a TCC include infection that needs frequent inspection or wet drainage, ischemia that cannot tolerate a closed rigid device, fluctuating edema that turns yesterday's cast into today's tourniquet or today's loose shell, and wet, highly exudative wounds that soak padding. Claustrophobia, inability to use a gait aid, and unstable gait also push you toward another plan. Do not flatten this into “never cast any infected foot.” IWGDF allows clinicians to consider a non-removable knee-high device when there is either mild infection or mild ischemia. If both mild infection and mild ischemia are present, or if either infection or ischemia is moderate, a removable knee-high or ankle-high device is the more typical choice so the foot can be inspected. Severe infection or severe ischemia is treated as a limb threat first; offloading still matters, but it does not outrank revascularization or source control.

Removable walkers, instant TCC, and the adherence trap

A removable cast walker (RCW) is a prefabricated, usually knee-high boot with a rigid rocker sole and a stock or custom insole. On a bench test it can drop plantar pressure nearly as much as a TCC if it stays on. The clinical failure is not the plastic; it is the sentence “I’ll take it off at home.” Showers, sleeping, “just to the mailbox,” and dressing changes become hours of unprotected walking. Trials that force the walker to stay on close the healing gap with TCC. Non-removable devices improve adherence because the person cannot bargain with the device at 9 p.m.

An instant total contact cast (iTCC) is that same RCW wrapped with cohesive bandage or casting tape so the walker cannot slip off without cutting the wrap. You keep the offloading geometry of the walker and add the adherence of a non-removable device. Recheck skin at wrap changes. Document why the device is non-removable so night-shift staff do not unwrap it “for comfort.”

When a knee-high device is not tolerated, step down rather than giving up:

• Ankle-high walkers
• Felted foam with an aperture over the ulcer, worn inside an extra-depth or postoperative shoe
• Forefoot or heel wedge shoes (half-shoes) that unload the ulcer zone
• Postoperative shoes with a rigid sole

Each step down usually means more residual pressure and more dependence on the person actually wearing the device. Felted foam is a clinic technique: adhesive felt with a U-shaped or windowed cut-out around the ulcer, applied to the skin or to the insole, then covered with a surgical shoe. Replace it when it compresses, soaks, or walks off-center. A felt pad that has migrated onto the ulcer increases local pressure. Wedge shoes unload one region of the foot but can destabilize gait and are a poor match for midfoot Charcot deformity.

Protective footwear after the ulcer, not instead of a cast

Once the ulcer is closed—or for the contralateral foot—the goal shifts from aggressive offloading to protective footwear. Extra-depth shoes create volume for a custom or prefabricated accommodative insert without crushing the dorsum. Custom orthoses redistribute pressure away from the healed site and from bony prominences. Rocker soles reduce forefoot pressure by rolling the person over the metatarsal heads instead of bending through them. Postoperative shoes are a short-term discharge tool, not a six-month plan. A healed plantar ulcer is a reason to escalate footwear, not a reason to return to the same athletic shoe that helped create the ulcer. Extra-depth shoes and orthoses prevent recurrence; they are not a substitute for a knee-high non-removable device on an open plantar DFU.

Heels, chairs, and beds are different problems

Heel ulcers are usually pressure injuries from the mattress. A walking boot that unloads the forefoot does not float a heel in bed. Purpose-built heel-offloading boots that suspend the heel in air and support the calf are more reliable than a pillow, because pillows migrate. A pillow that starts under the calf ends under the Achilles or under the knee, and the heel drops back onto the mattress. Pillows can work for a short supervised interval if they truly float the heel and the person does not kick them away; they are a weak plan for restless, delirious, or long-stay patients. Do not add an extra pillow under the knee when a heel boot is already in place—that can drop the heel back onto the bed. Do not pull a sheet or pillowcase over the boot; hammocking can cancel the float.

Do not confuse a chair cushion with a bed support surface. A wheelchair cushion offloads the ischium and coccyx while sitting; it does nothing for heels on a stretcher. Sitting with heels jammed against a wheelchair footplate is another heel-injury pattern. Reposition the feet, pad the footplate, or use a device that actually lifts the heel.

Clinical scenario

A 62-year-old with neuropathy and a 2 cm plantar first-metatarsal ulcer, no cellulitis, palpable pulses, and an ankle-brachial index of 0.95 is given a postoperative shoe and told to “stay off it.” Two weeks later the ulcer is larger. The miss is mechanics and adherence, not the brand of foam dressing. A non-removable knee-high device (TCC or iTCC) is the evidence-based next step if infection remains absent or mild. Education that the person “should keep the shoe on” is not a substitute for a device they cannot take off. If moderate infection appears, switch to a removable walker so the foot can be inspected, treat infection, and return to non-removable offloading when it is safe. Full cast technique is still Chapter 13 work; the decision to stop using a flimsy shoe is this chapter's work.