What is the appropriate management of a plantar corn in an adult, and what precautions are required for diabetes mellitus or peripheral arterial disease?

Management of Plantar Corns

For plantar corns in adults, the primary treatment is scalpel debridement by a trained foot care specialist combined with pressure redistribution through properly fitted therapeutic footwear, with critical additional precautions required for patients with diabetes mellitus or peripheral arterial disease including mandatory vascular assessment, loss of protective sensation screening, and strict avoidance of barefoot walking. 1, 2

Initial Assessment Requirements

Standard Evaluation for All Patients

• Examine the patient's current footwear as ill-fitting shoes are the most frequent cause of corn formation 1
• Inspect for erythema, warmth, or signs of impending tissue breakdown around the lesion 2
• Assess foot biomechanics and identify any bony deformities (hammertoes, prominent metatarsal heads, bunions) that increase plantar pressure 1

Mandatory Additional Screening for Diabetes or Suspected Diabetes

• Perform 10-g monofilament testing to assess for loss of protective sensation (LOPS) - absent monofilament sensation indicates LOPS 1, 2
• Ideally combine monofilament with at least one other test: pinprick, temperature sensation, 128-Hz tuning fork vibration, or ankle reflexes 1
• Palpate pedal pulses and assess for peripheral arterial disease 1, 2
• If pedal pulses are absent or diminished, measure ankle-brachial index (ABI) - values <0.9 indicate PAD 1
• Consider toe pressure (normal >30 mmHg) or transcutaneous oxygen pressure (TcPO2, normal >25 mmHg) as ankle pressures may be falsely elevated due to arterial calcification 1

Treatment Algorithm

Primary Treatment: Debridement and Pressure Redistribution

• Scalpel debridement by a trained foot care specialist is the cornerstone of treatment, removing callus until it resolves and does not recur 2, 3
• Frequent debridement may be necessary for recurrent lesions 1
• Pressure redistribution through well-fitted walking shoes or athletic shoes that cushion the feet and redistribute plantar pressure 1, 2

Footwear Recommendations Based on Deformity Severity

• Patients with mild increased plantar pressure or early neuropathy: Well-fitted walking shoes or athletic shoes with cushioning 1
• Patients with bony deformities (hammertoes, prominent metatarsal heads, bunions): Extra-wide or depth shoes 1
• Patients with severe deformities (Charcot foot) that cannot be accommodated with commercial therapeutic footwear: Custom-molded shoes 1
• For moderate-to-high risk diabetic patients: Prescribe therapeutic footwear with demonstrated plantar pressure-relieving effect during walking 1

Surgical Consideration (Rarely Indicated)

• Surgery is rarely indicated and should only target correction of abnormal mechanical stresses 4
• Consider flexor tendon tenotomy for non-rigid hammertoe with pre-ulcerative lesion 1
• Surgical excision with primary or secondary intention closure may be considered for intractable plantar keratoses unresponsive to conservative management 5

Critical Precautions for Diabetes Mellitus

Risk Stratification and Monitoring Frequency

• Corns and calluses are considered pre-ulcerative lesions in patients with PAD and substantially increase ulceration risk 1
• Screen annually for patients at very low risk (IWGDF risk 0) 1
• Screen every 6-12 months for IWGDF risk 1 (LOPS or PAD alone) 1
• Screen every 3-6 months for IWGDF risk 2 (LOPS + PAD, or LOPS + foot deformity, or PAD + foot deformity) 1
• Screen every 1-3 months for IWGDF risk 3 (LOPS or PAD with history of foot ulcer or amputation) 1

Mandatory Patient Education

• Never walk barefoot, in socks only, or in thin-soled slippers whether indoors or outdoors 1, 2
• Perform daily foot inspection for new lesions, warmth, redness, or drainage 2
• Immediately report any signs of infection or tissue breakdown 2
• Understand that loss of protective sensation eliminates pain as a warning sign 1

Vascular Assessment Requirements

• If ABI <0.6, toe pressure <50 mmHg, or TcPO2 <30 mmHg: Healing will be severely impaired and revascularization should be considered 1
• Urgent vascular imaging and revascularization should be considered if ankle pressure <50 mmHg, toe pressure <30 mmHg, or TcPO2 <25 mmHg 1
• Emphasize cardiovascular risk reduction: smoking cessation, treatment of hypertension and dyslipidemia, aspirin use 1

Critical Precautions for Peripheral Arterial Disease

Initial Screening

• Obtain history of decreased walking speed, leg fatigue, or claudication 1
• Perform ankle-brachial index testing in patients with symptoms or signs of PAD 1
• Many patients with PAD are asymptomatic, making objective testing essential 1

Management Considerations

• PAD is the most important factor relating to outcome of any foot lesion in diabetic patients 1
• Refer patients with significant claudication or positive ABI for further vascular assessment 1
• Consider exercise programs, medications, and surgical revascularization options 1

Common Pitfalls to Avoid

• Never allow patients with diabetes or neuropathy to perform self-debridement - risk of inadvertent injury and infection 2
• Do not dismiss corns as merely cosmetic issues in high-risk patients - they represent critical pre-ulcerative lesions 1, 6
• Avoid footbaths as they induce maceration of the skin 1
• Do not rely solely on ankle pressures in diabetic patients due to potential arterial calcification - use toe pressures or TcPO2 1
• Never assume adequate perfusion based on palpable pulses alone in diabetic patients - objective vascular testing is essential 1