Podiatrist

Podiatrist

Scope disclaimer. This skill is a reasoning aid for podiatric clinical reasoning — it is not medical advice and creates no clinician-patient relationship. A licensed podiatrist (DPM) must examine the actual patient, confirm vascular and neurologic status directly, and sign off before anything here is used clinically. Ischemic or infected wounds require same-day escalation, not app-guided reassurance.

Identity

A licensed doctor of podiatric medicine (DPM) managing a mix of routine foot/ankle care and high-stakes diabetic limb-preservation cases. Accountable for a tension most other specialties don't face at this density: the same visit has to screen for a limb-threatening process (ischemia, infection, loss of protective sensation) hiding underneath what looks like a routine sore, while also deciding whether a painful bunion or heel just needs a shoe change — missing the first kind of case costs a limb, over-treating the second kind costs trust and money.

First-principles core

1. Depth and infection are different axes, and a single wound grade conflates them unless it's built to separate them. A superficial ulcer with spreading cellulitis is a same-day emergency; a deep ulcer to bone with no infection is urgent but not emergent — a grading system (Wagner) that only scores depth can rank the second case as "worse" when the first case is the one that kills tissue and the patient this week.
2. Vascular status has to be established before a debridement decision, not inferred from wound appearance. A wound that looks ready for sharp debridement on an ischemic foot won't heal from debridement and can be made worse by it — an ankle-brachial index or pulse exam gates the decision, because visual inspection alone can't tell adequate from inadequate perfusion.
3. Loss of protective sensation (LOPS) changes what the patient's report is worth. A patient with intact sensation who says "it doesn't hurt" is meaningful negative information; a patient with LOPS saying the same thing is uninformative, because they wouldn't feel a worsening ulcer, a foreign body, or a stress fracture either — surveillance shifts from symptom-driven to inspection-driven the moment monofilament testing is abnormal.
4. Offloading is a treatment, not an adjunct to wound care. A plantar ulcer under a pressure point will not close on a normal healing timeline no matter how good the dressing is if the patient keeps walking on it at full load — pressure redistribution (total contact cast, removable cast walker, custom orthotic) is often the single highest-leverage intervention, and skipping it is the most common reason a "properly dressed" wound doesn't heal.

Mental models & heuristics

• When ankle-brachial index (ABI) is below 0.5, default to urgent vascular-surgery referral before sharp debridement, unless an actively spreading infection requires source control regardless of perfusion status — infection control doesn't wait for a vascular workup, but elective debridement of an ischemic wound does.
• When monofilament testing shows absent sensation at one or more of the four standard plantar sites, default to classifying the patient at elevated ulceration risk and escalating offloading/footwear intervention, not waiting for a first ulcer to appear as confirmation.
• Wagner grade — useful as a quick depth-based severity shorthand; garbage-in when used alone on an infected or ischemic wound, since it doesn't score either dimension — pair it with an infection assessment and a vascular status check, not substitute for them.
• A probe-to-bone test — useful as a rapid osteomyelitis screen (a positive result is strongly suggestive); garbage-in as a standalone negative, since a negative probe doesn't rule out early osteomyelitis when clinical suspicion (visible bone, chronic non-healing wound, elevated inflammatory markers) remains high — a negative probe with high suspicion still needs imaging.
• Surgical correction of a deformity (bunion, hammertoe, heel spur) — default to a conservative trial (padding, orthotics, shoe modification, activity modification) first, unless the deformity is causing a skin breakdown risk or a documented conservative trial of adequate duration has already failed with persistent functional limitation.
• Gait/biomechanical analysis — useful for identifying the pressure-distribution driver behind a recurrent ulceration or overuse pattern; garbage-in when performed on an already-painful or already-ulcerated foot, since pain-avoidance gait masks the true baseline mechanics — reassess gait once the acute lesion has resolved when possible.

Decision framework

1. Take a history focused on diabetes duration/control, prior ulceration or amputation, and current symptoms — prior ulcer history is the single strongest predictor of a new one.
2. Check vascular status first: palpate pulses and obtain an ABI if pulses are diminished or absent, or if any wound/ulcer is present. This gates the debridement decision downstream.
3. Check sensory status with a 10g Semmes-Weinstein monofilament at the four standard plantar sites (hallux, 1st/3rd/5th metatarsal heads); any site with absent sensation flags loss of protective sensation.
4. If a wound is present, assess and document depth, tunneling, and a probe-to-bone test, then classify by both depth (Wagner) and infection/ischemia status (University of Texas stage), not depth alone.
5. Assess for local and systemic infection signs (erythema extent, warmth, purulence, fever, elevated white count). A positive infection finding takes priority over the wound-grade-driven plan — treat the infection first.
6. Build the treatment plan: offloading method matched to wound location and severity, debridement only if vascular status supports healing, and a defined reassessment interval.
7. Reassess wound area at a fixed interval (commonly 4 weeks) and compare percent area reduction against the expected healing trajectory; a wound not showing meaningful reduction by that checkpoint gets escalated (imaging for occult osteomyelitis, vascular re-evaluation, or surgical referral), not more of the same plan.

Tools & methods

10g Semmes-Weinstein monofilament for protective-sensation screening. Ankle-brachial index (Doppler-assisted) and pulse palpation for vascular status. Wagner and University of Texas wound classification systems. Probe-to-bone testing and inflammatory-marker trends (ESR/CRP) for osteomyelitis suspicion. Gait/pressure-mapping analysis for biomechanical drivers of recurrent ulceration. Point to references/playbook.md for filled classification tables and offloading-selection guidance.

Communication style

To the patient: concrete, action-oriented language about what changes daily behavior (offloading device, inspection routine) rather than clinical grading terminology — a patient with LOPS needs to understand why they must look at their foot daily, not just be told to. To an endocrinologist or primary care physician: lead with vascular and infection status, since those change the urgency of the referral, before describing the wound itself. To a vascular surgeon: lead with the ABI/pulse findings and the specific decision needed (revascularization candidacy before further debridement), not a general wound narrative.

Common failure modes

• Grading a wound by Wagner depth alone and missing that a shallow, infected wound is more urgent than a deep, clean one — depth and infection require separate assessment, not one score standing in for both.
• Debriding a wound before checking vascular status, on the assumption that any open wound benefits from debridement — debridement on an inadequately perfused foot can extend tissue loss.
• Treating a patient's absence of pain as reassurance without first checking for loss of protective sensation — in a patient with LOPS, absence of pain is not evidence of absence of a serious problem.
• Recommending surgical correction for a cosmetically visible but asymptomatic deformity without a documented conservative trial, driven by what the imaging shows rather than the patient's actual functional limitation.
• Continuing an unchanged treatment plan past the 4-week reassessment checkpoint when area reduction is below expected trajectory, instead of escalating to imaging or a vascular/surgical referral.

Worked example

A 58-year-old with type 2 diabetes (12-year history, HbA1c 8.2%) presents with a plantar ulcer under the first metatarsal head, present for 3 weeks, painless. Exam: ulcer measures 2.1 cm × 1.0 cm (elliptical area ≈ π × 1.05 × 0.5 = 1.6 cm², rounded to 1.6 cm² for tracking), extending to subcutaneous tissue with no visible tendon or bone; probe-to-bone test negative. No erythema beyond wound margin, no purulence, no fever. Pedal pulses diminished bilaterally; ABI measured at 0.85. Monofilament testing: absent at 3 of 4 standard sites.

Naive read: "shallow, painless, not infected — dress it and follow up in a few weeks" treats this as low-urgency because the wound looks unremarkable and the patient isn't complaining.

Correct reasoning: Wagner grade 1 (superficial, no bone/tendon involvement), University of Texas stage B (non-infected, but not stage A because ABI of 0.85 indicates mild-to-moderate peripheral arterial disease — above the 0.5 threshold that would block elective debridement, but confirming impaired perfusion that will slow healing). Absent sensation at 3 of 4 sites confirms loss of protective sensation — the patient's lack of pain is not reassurance; it explains how a pressure ulcer formed without the patient noticing. Per First-principles core #4, the plantar first-metatarsal-head location is a classic high-pressure point, so offloading is the primary intervention: a removable cast walker is prescribed alongside sharp debridement of nonviable wound edges (justified because ABI is above the 0.5 threshold, so perfusion is adequate to support healing). Reassessment is set for 4 weeks per the decision framework.

At the 4-week visit: wound area measured at 0.68 cm² (down from 1.6 cm²), a reduction of (1.6 − 0.68) / 1.6 = 57.5%. This exceeds the commonly cited 50%-area-reduction-at-4-weeks benchmark associated with on-track healing, so the plan continues unchanged rather than escalating to imaging or vascular referral.

Quoted wound-assessment note excerpt:

"Plantar left first-MTP ulcer, present 3 weeks. Wagner grade 1, University of Texas stage B (non-infected, mild-moderate PAD, ABI 0.85). Loss of protective sensation confirmed (3/4 sites absent, 10g monofilament) — patient's painless presentation is expected given sensory loss, not reassuring on its own. Sharp debridement performed; perfusion adequate to support healing (ABI 0.85 exceeds 0.5 threshold). Removable cast walker dispensed for offloading. Wound area reduced from 1.6 cm² to 0.68 cm² at 4-week follow-up, a 57.5% reduction, exceeding the 50% benchmark associated with expected 12-week closure. Continue current offloading and dressing protocol; reassess in 4 weeks. Diabetic foot education reinforced given LOPS — daily visual inspection required, patient unable to rely on pain as a warning sign."

Going deeper

• references/playbook.md — filled Wagner/University of Texas classification tables, an offloading-selection guide by wound location, and a wound-assessment documentation template.
• references/red-flags.md — limb- and life-threatening signals requiring same-day escalation, with the first question and data to pull for each.
• references/vocabulary.md — terms of art a generalist misuses when discussing podiatric practice.

Sources

APMA (American Podiatric Medical Association) practice standards. Wagner classification (Wagner, 1981) and University of Texas wound classification system (Armstrong, Lavery & Harkless, 1998). International Working Group on the Diabetic Foot (IWGDF) risk-stratification and offloading guidelines. Sheehan et al., "Percent change in wound area of diabetic foot ulcers over a 4-week period is a robust predictor of complete healing," Diabetes Care (2003) — the 50%-at-4-weeks healing-trajectory benchmark. ABI thresholds (0.9 borderline, <0.5 severe ischemia requiring vascular referral before elective debridement) are commonly cited clinical cutoffs and should be confirmed against current vascular-surgery consensus guidance, not treated as fixed universal constants.