Diabetic Neuropathy and a New Below-Knee Orthosis
A 62-year-old man with type 2 diabetes (HbA1c 9.4%), peripheral neuropathy, and a healed plantar ulcer presents for a custom molded ankle-foot orthosis for foot drop after a tibial nerve decompression. Sensation to 10 g monofilament is absent over the plantar forefoot and heel; posterior tibial and dorsalis pedis pulses are palpable. He has a 12 mm fixed plantarflexion contracture, 8 degrees of dorsiflexion available passively with firm end-feel, and 4/5 dorsiflexion strength. Skin is intact but thin, with a callus over the first metatarsal head. He lives alone, works as a delivery driver, and reports he cannot feel his feet when they get cold. He is eager to return to full-time driving within two weeks.
1. Which assessment findings most change your design and material decisions, and how do they change them?
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The sensory loss is the dominant driver, not the motor deficit. Absent 10 g monofilament protection means any pressure point can become an ulcer without warning, so the device must distribute load over the largest possible area and avoid focal trimlines over the metatarsal heads and malleoli. A total-contact, well-flared shell with a soft interface and a rocker bottom is preferred over a thin rigid leaf-spring design that concentrates force.
The fixed plantarflexion contracture (12 mm) and limited passive dorsiflexion mean the device must accommodate the existing position rather than force correction; attempting to correct at casting risks skin breakdown and pain. Cast in the corrected-as-tolerated position and plan serial adjustment.
Palpable pulses and intact skin lower, but do not eliminate, vascular risk; document them. The callus over the first metatarsal head is a pre-ulcerative signal and should be offloaded by design, not just by padding. His inability to sense cold is a safety flag for any device that could mask temperature or pressure cues.
2. He asks to be back driving in two weeks. How do you sequence the plan and what do you tell him?
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Two weeks is not a realistic break-in for a first custom device in an insensate limb. A defensible sequence: cast/scan now with the foot in its tolerant position; deliver a check socket or temporary device first if the timeline is tight; inspect skin at every visit and teach him daily mirror checks since he cannot feel pressure.
Break-in should be graded (e.g., 1-2 hours initially, increasing with skin inspection between intervals), and return to driving should be gated on demonstrated tolerance plus a driving-specific check: can he feel and operate pedals, does the device interfere with ankle motion needed for braking, and does he have adequate reaction time and proprioceptive feedback?
State clearly that the timeline depends on skin tolerance, not on the calendar, and document the counseling. Coordinate with his physician regarding glycemic control, since poor control impairs healing if a pressure injury occurs.
3. At delivery, a small red area appears over the first metatarsal head after 30 minutes of wear. What is your next step and why?
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Stop wear, document the location, size, and blanching behavior, and treat it as a pressure warning in an insensate foot rather than a minor finding. Do not simply tell him to 'wear it in.'
Relieve the area by modifying the shell or interface (additional relief, softer topcover, or broader load distribution) and re-check with a controlled wear trial and skin inspection. Because he cannot feel the pressure, the objective skin response is the only reliable feedback, so each trial must be time-limited and followed by inspection.
If redness persists or does not resolve with modification, escalate (reduce wear, refer for wound evaluation). Document the finding, the modification, and the re-check. This is a follow-up and safety issue, not a cosmetic one.