5.3 Neuropathic Foot Ulcers, Charcot, and Wagner Grading

5.3 Neuropathic Foot Ulcers, Charcot, and Wagner Grading

Quick Answer: Neuropathic foot ulcers grow on insensate, high-pressure plantar skin, especially under metatarsal heads, often beneath callus or hemorrhage in callus. Test LOPS with a 10-g monofilament, 128-Hz tuning fork, and proprioception. Wagner grades 0–5 run from intact high-risk skin to whole-foot gangrene. Charcot feet are warm and swollen, sometimes almost painless; they are immobilized and offloaded, not walked in street shoes. Infection on a numb foot can be quiet—look for drainage, glucose spikes, and new collapse, not a pain score of 10.

Independent OpenExamPrep teaching treats the diabetic foot as a mechanical and neurologic problem first. Many of these ulcers also have PAD (neuroischemic disease). Always overlay the arterial exam from section 5.2; neuropathy does not grant a free pass to ignore pulses.

LOPS and the sensory-motor-autonomic triad

Loss of protective sensation (LOPS) means the person cannot feel a 10-gram force that would ordinarily make a person shift weight. Use a 10-g (5.07) Semmes-Weinstein monofilament on intact skin, not on an ulcer, callus pile, or scar. Common teaching sites include the pulp of the hallux and metatarsal heads (protocols use four or ten sites—follow your facility’s map and document which sites were tested). Apply the filament until it bends; the patient, with eyes closed, says when it is felt. Inability to feel it at tested sites supports LOPS. Do not stab, do not slide, and do not test through socks.

Add vibration with a 128-Hz tuning fork, typically at the dorsal hallux interphalangeal joint. Ask when the buzz stops and compare with the examiner’s finger or the opposite side. Proprioception: hold the hallux at the sides, move it a few degrees up or down, and ask the direction. Large-fiber loss shows up here even when light touch seems “pretty good.”

Autonomic neuropathy reduces sweating (anhidrosis). Skin becomes dry, shiny, and cracked; heel fissures become entry points. Do not celebrate “no sweat” as good hygiene. Motor neuropathy weakens intrinsic muscles. The result is claw toes, prominent metatarsal heads, and a high-pressure forefoot. The fat pad migrates; bone sits closer to the shoe.

If the patient laughs that they “haven’t felt their feet in years,” believe them and look at the shoe, not only the A1C.

Callus, hemorrhage, and the plantar metatarsal-head ulcer

Repetitive load on insensate skin builds callus. Callus is both a marker of pressure and a source of more pressure. Hemorrhage under callus (a maroon or rusty stain in the keratin) is a pre-ulcer or a hidden ulcer until you gently reduce the hyperkeratosis per protocol and look. Leaving a blood-stained callus “because it isn’t open” is how a probe-to-bone cavity is missed.

The classic diabetic foot ulcer (DFU) is plantar, under a metatarsal head (first and fifth are common), with a hyperkeratotic rim, often undermined. Dorsal ulcers over claw-toe proximal interphalangeal joints are shoe-trauma neuropathic ulcers. Interdigital ulcers come from moisture plus deformity. Contrast location with LEVD (gaiter) and isolated LEAD (toe tips, lateral malleolus without a plantar pressure story).

Pulses may be present or even bounding when medial calcification stiffens vessels—another reason ABI can mislead and TBI belongs in diabetes.

Wagner 0–5: depth and gangrene, not a personality scale

The Wagner grade is a high-yield classification for diabetic foot lesions. Memorize the rungs; items will hand you a stem and ask for the grade or the next action implied by the grade.

• Grade 0: Skin intact. The foot is still high-risk—deformity, LOPS, prior ulcer, or callus. This is a prevention and offloading grade, not “nothing to see.”
• Grade 1: Superficial ulcer through the dermis, not obviously involving tendon, capsule, or bone.
• Grade 2: Deep ulcer to tendon, ligament, joint capsule, or bone without named abscess or osteomyelitis in the original scheme.
• Grade 3: Deep ulcer with abscess, osteomyelitis, or joint sepsis.
• Grade 4: Gangrene of the forefoot (toes or forefoot region).
• Grade 5: Gangrene of the entire foot.

Wagner does not replace perfusion testing or a probe-to-bone exam. A grade 1 ulcer with an ABI of 0.40 is still a threatened limb. A grade 3 finding (deep infection) needs surgical and infectious-disease pathways, not a thicker foam. Do not invent extra grades. Do not use Wagner for a sacral pressure injury; it is a foot language.

University of Texas and other systems exist in clinics; if the stem names Wagner, answer in Wagner.

Charcot neuro-osteoarthropathy

Charcot is inflammation and bone-joint destruction in a neuropathic foot (or ankle). In the acute phase the foot is warm, red, and swollen, often unilateral. Pain may be absent or far less than the appearance would suggest in a person with intact sensation. Midfoot collapse produces a rocker-bottom sole; the cuboid or midfoot becomes a new plantar pressure point and a future ulcer site.

Differential diagnoses that steal time:

• Cellulitis / deep infection: more likely with a portal of entry, drainage, fluctuance, fever, or marked hyperglycemia. Charcot can coexist with infection; when in doubt, image and offload while you work it up.
• Gout: exquisite pain in a sensate person, often first MTP; a numb Charcot foot may not scream.
• DVT: calf-centered swelling; Charcot swelling is a foot story. Still, do not skip a venous study if the calf is the swollen segment.

Immediate action: offload and immobilize (total contact cast or a bivalved walker per the team’s protocol), non-weight-bearing or protected weight-bearing as ordered, and do not send the patient home to walk in regular shoes. Continued ambulation on an inflamed neuropathic midfoot is how the arch collapses. Temperature comparison with the contralateral foot helps follow activity of disease once you have a baseline.

Infection when the foot cannot hurt

Insensate feet do not reliably produce wound pain. Look for new drainage, odor after cleansing, delayed healing, unexplained hyperglycemia, a suddenly tighter shoe, leukocytosis, or a probe that reaches bone. Erythema can be Charcot, infection, or both. Educate that “I would feel it if it were infected” is false. A silent Wagner 3 abscess presents as a little plantar hole and a sick glucose chart.

Scenario: the painless rocker and the hidden grade

A 58-year-old man with a 20-year diabetes history notices his left shoe feels tight. The midfoot is 3 °C warmer than the right, swollen, and mildly pink. He rates pain 2/10 and wants to keep working on a warehouse floor. There is no open ulcer. Monofilament is unfelt at four plantar sites; vibration is absent at the hallux. A covering clinician considers a 10-day course of oral antibiotics for “cellulitis” and a return to steel-toe boots. The CWCN treats this as acute Charcot until proven otherwise: immobilize, stop unprotected walking, and obtain urgent Charcot-capable imaging and offloading, while still considering infection if a portal appears. Two weeks later a callus under the collapsed midfoot shows hemorrhage; careful reduction reveals a superficial plantar ulcer—Wagner 1 on a grade 0 foot that was allowed to walk. The missed step was the shoe, not the hydrogel.

Neuropathic assessment is sensation plus structure plus depth. If any of the three is missing from the note, the etiology is incomplete.