What is the ICD-10 code for a callused area over the plantar surface of the first metatarsal, potentially related to conditions such as diabetes (Diabetes Mellitus, DM) or hallux valgus?

ICD-10 Code for Plantar First Metatarsal Callus

For a callused area over the plantar surface of the first metatarsal, use ICD-10 code L84 (Corns and callosities), with additional codes for any underlying conditions such as diabetes (E11.621 for Type 2 diabetes with foot ulcer, or E11.622 for Type 2 diabetes with other skin ulcer) or hallux valgus (M20.1) when present. 1

Primary Diagnosis Code

• L84 is the appropriate ICD-10 code for corns and callosities, which includes plantar calluses regardless of location 1, 2
• This code captures the hyperkeratotic lesion itself as the primary pathology 1

Essential Additional Coding for Context

When Diabetes is Present

• Add E11.621 (Type 2 diabetes mellitus with foot ulcer) if the callus has broken down into an ulcer 2
• Add E11.622 (Type 2 diabetes mellitus with other skin ulcer) for pre-ulcerative calluses in diabetic patients, as calluses are considered pre-ulcerative lesions requiring documentation 3, 1
• Use E10.621 or E10.622 for Type 1 diabetes with the same distinctions 2
• The ICD-10 system provides significantly improved specificity for diabetic foot complications compared to ICD-9, with 96% capture rate for incident ulcers versus 85% with ICD-9 2

When Hallux Valgus is Present

• Add M20.10 (Hallux valgus, unspecified foot) or M20.11/M20.12 for right/left foot respectively when the callus is secondary to this deformity 4, 1
• ICD-10 allows laterality specification (left versus right), which ICD-9 did not capture 2

When Flatfoot Deformity is Present

• Add M21.40 (Flat foot, unspecified foot) or M21.41/M21.42 for right/left foot when the callus results from collapsed arch mechanics 5

Critical Documentation Requirements

• Document precise anatomical location using standardized terminology: "plantar surface of first metatarsal head" rather than simply "callus" 1
• Measure and record dimensions in millimeters (length × width) to enable tracking of healing progress 1
• Probe depth after debridement using a sterile blunt probe—bone contact indicates osteomyelitis risk and requires different coding 1, 4
• Test protective sensation with 10-g Semmes-Weinstein monofilament at the first metatarsal head; loss of sensation at 2 or more sites indicates high-risk status requiring documentation 1, 4
• Document pedal pulses (dorsalis pedis and posterior tibial); if absent or diminished, document ankle-brachial index values 1, 4

Common Coding Pitfalls to Avoid

• Never code as simply "L84" without additional context codes when diabetes, vascular disease, or structural deformities are present—this provides insufficient information for risk stratification 1
• Distinguish from plantar warts by paring the lesion: pinpoint bleeding indicates wart (use L82.1 for seborrheic keratosis or A63.0 for anogenital warts) rather than mechanical hyperkeratosis 1
• Do not confuse with ulceration: if the callus has broken through to expose deeper tissue, this requires ulcer coding (E11.621 for diabetic foot ulcer) rather than L84 alone 2, 4
• Document infection signs explicitly (purulence, warmth, tenderness, induration) as these change the primary diagnosis to infection codes 1, 4

Risk Stratification Impact on Coding

• An ankle-brachial index <0.5 or ankle pressure <50 mmHg indicates critical ischemia requiring urgent vascular evaluation and should trigger additional peripheral arterial disease coding (I70.25 for atherosclerosis of native arteries of extremities) 1, 4
• Loss of protective sensation combined with callus formation in diabetic patients represents high-risk status requiring integrated foot care every 1-3 months, which affects documentation frequency 3, 4