Probeable plantar ulcer with equivocal X-ray — workup, duration, and the surgical threshold

Expected management

Combine before scanning. The ulcer probes to bone (JAMA positive LR 6.4) with an ESR of 85 (above the 70 threshold at LR 11) — so add the plain-X-ray result to the probe rather than ordering MRI first: the sequential combination reaches 0.97 sensitivity with 0.92 specificity and likelihood ratios of 12.8 and 0.02, and pooled analysis puts the combination at 0.94 sensitivity with a diagnostic odds ratio of 82 — MRI-comparable, accessible and inexpensive in trained hands.^[28][32][31] Note the prevalence honesty aloud: at 12% prevalence the probe's positive value is only 0.57 while its negative value is 0.98 — in this high-risk probe-positive foot the test rules in, and a negative test would have ruled out.^[29][30]

Discipline the MRI with biopsy. MRI is the preferred test at 0.90 sensitivity and 0.79 specificity (pooled to 0.96/0.84), and a normal scan at LR 0.14 makes osteomyelitis much less likely — but 29.3% of MRI diagnoses go unconfirmed at biopsy with 12 false positives in the county series, so a positive MRI earns a bone biopsy with culture or histology as gold, plus a radiologist conversation, before committing to resection or weeks of antibiotics.^{[33][34][28][35]}

Shorten antibiotics to the tested floor. Her cellulitis without systemic toxicity and probable osteomyelitis fit the ladder as study regimens: 6 weeks where non-surgical treatment is chosen (65% remission, gut events 15 vs 45%); 3 weeks after adequate debridement (84 vs 73%, noninferior); 10 days for the soft-tissue component after debridement (77 vs 71%) — disclosing the 23-versus-16% new-osteomyelitis tail so surveillance, not duration, carries the residual risk.^[36][37][38]

Set the surgical threshold by threat and response. Without life-threat, limb-threat or failure, the non-surgical path holds an 82.3% apparent-remission precedent with oral outpatients and 77% of relapses re-arrested — so admit only the threatened foot for intravenous therapy and operate the failing one.^[39] If surgery comes, prioritise foot-sparing conservative procedures (49.1% need no amputation of any part) with S. aureus expected in just over half — and resect to clean margins to shorten antibiotics (21 vs 37 days) while warning that 12-month ulceration, reinfection, amputation and healing do not change either way.^[40][41]

Close with classification and cover. Describe the ulcer by SINBAD variables in words — never a lone total, since no system predicts individual outcomes — offload non-removably while it heals, and book lifelong surveillance: recurrence runs 22.1% per person-year.^[14][18][4]