ICD-10 Guide

M21

Billable

Other acquired deformities of limbs

Chapter 13:Diseases of the musculoskeletal system

BILLABLE STATUSYes

IMPLEMENTATION DATEOctober 1, 2015

LAST UPDATED09/17/2025

Code Description

ICD-10 M21 is a billable code used to indicate a diagnosis of other acquired deformities of limbs.

Key Diagnostic Point:

M21 encompasses a variety of acquired deformities affecting the limbs, which can arise from various causes such as trauma, infections, or underlying medical conditions. These deformities may include abnormalities of the fingers and toes, such as syndactyly (fusion of digits), polydactyly (extra digits), and hallux valgus (bunion formation). Hallux valgus is characterized by lateral deviation of the great toe, often leading to pain and difficulty in ambulation. Corrective procedures may involve surgical interventions such as osteotomy or arthrodesis to realign the affected digits. Accurate coding requires a thorough understanding of the patient's history, the specific deformity present, and any corrective measures taken. Documentation should detail the nature of the deformity, the functional impact on the patient, and any previous treatments attempted. This code is essential for capturing the complexity of limb deformities that are not classified elsewhere in the ICD-10 system.

Code Complexity Analysis

Complexity Rating: Medium

Medium Complexity

Complexity Factors

Variety of deformities covered under the code
Need for precise documentation of the deformity type
Differentiation between congenital and acquired conditions
Potential for multiple corrective procedures

Audit Risk Factors

Inadequate documentation of the deformity type
Failure to specify the acquired nature of the deformity
Incorrect linkage of procedures to the diagnosis
Omission of prior treatment history

Specialty Focus

Medical Specialties

Orthopedic Surgery

Documentation Requirements

Detailed operative reports, pre-operative assessments, and post-operative follow-ups.

Common Clinical Scenarios

Surgical correction of hallux valgus, treatment of finger deformities post-trauma.

Billing Considerations

Ensure that all surgical interventions are documented with specific details regarding the procedure and outcomes.

Podiatry

Documentation Requirements

Comprehensive foot examinations, patient history regarding foot pain, and treatment plans.

Common Clinical Scenarios

Management of bunions, treatment of toe deformities, and conservative versus surgical options.

Billing Considerations

Document the functional impact of the deformity on the patient's daily activities.

Coding Guidelines

Inclusion Criteria

Use M21 When

Follow official ICD
10 coding guidelines, ensuring accurate documentation of the acquired nature of the deformity
Include any relevant history of trauma or underlying conditions that may have contributed to the deformity

Exclusion Criteria

Do NOT use M21 When

No specific exclusions found.

Related CPT Codes

28296CPT Code

Bunionectomy

Clinical Scenario

Performed for hallux valgus correction.

Documentation Requirements

Operative report detailing the procedure and indications.

Specialty Considerations

Orthopedic surgeons should document pre-operative assessments and post-operative care.

ICD-10 Impact

Diagnostic & Documentation Impact

Enhanced Specificity

ICD-10 Improvements

The transition to ICD-10 has allowed for more specific coding of acquired deformities, improving the accuracy of patient records and facilitating better treatment planning.

ICD-9 vs ICD-10

The transition to ICD-10 has allowed for more specific coding of acquired deformities, improving the accuracy of patient records and facilitating better treatment planning.

Reimbursement & Billing Impact

The transition to ICD-10 has allowed for more specific coding of acquired deformities, improving the accuracy of patient records and facilitating better treatment planning.

Resources

Clinical References

•
ICD-10-CM Official Guidelines for Coding and Reporting

Coding & Billing References

•
ICD-10-CM Official Guidelines for Coding and Reporting

Frequently Asked Questions

What types of deformities are included under M21?

M21 includes various acquired deformities such as hallux valgus, finger abnormalities, and other limb deformities resulting from trauma or disease.

How do I differentiate between congenital and acquired deformities?

Congenital deformities are present at birth, while acquired deformities develop after birth due to factors like injury, disease, or infection.

ICD-10 M21 is a billable code used to indicate a diagnosis of other acquired deformities of limbs.