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ICD-10 Guide
ICD-10 CodesM21.70

M21.70

Billable

Unequal limb length (acquired), unspecified site

BILLABLE STATUSYes
IMPLEMENTATION DATEOctober 1, 2015
LAST UPDATED09/17/2025

Code Description

ICD-10 M21.70 is a billable code used to indicate a diagnosis of unequal limb length (acquired), unspecified site.

Key Diagnostic Point:

Unequal limb length, or limb length discrepancy, refers to a condition where one limb is shorter or longer than the other due to acquired factors. This can result from various conditions such as trauma, surgical interventions, or diseases that affect bone growth or structure. Common causes include fractures that heal improperly, infections that affect bone integrity, or conditions like osteomyelitis. The condition can lead to functional impairments, gait abnormalities, and increased risk of osteoarthritis in the affected joints. Treatment often involves corrective procedures such as limb lengthening or shortening surgeries, orthotic devices, and physical therapy to improve function and alleviate discomfort. Accurate coding is essential for proper reimbursement and to reflect the complexity of the patient's condition and treatment plan.

Code Complexity Analysis

Complexity Rating: Medium

Medium Complexity

Complexity Factors

  • Variety of underlying causes leading to unequal limb length.
  • Need for detailed documentation of the acquired nature of the condition.
  • Potential for multiple associated procedures and co-morbidities.
  • Variability in treatment approaches based on the severity and cause of the discrepancy.

Audit Risk Factors

  • Inadequate documentation of the cause of limb length discrepancy.
  • Failure to specify the site of the limb length discrepancy.
  • Incorrect coding of associated procedures.
  • Lack of clarity in treatment plans and outcomes.

Specialty Focus

Medical Specialties

Orthopedics

Documentation Requirements

Detailed history of the patient's condition, including any trauma or surgical history, and specific measurements of limb lengths.

Common Clinical Scenarios

Patients presenting with post-fracture limb length discrepancies or those requiring corrective surgery.

Billing Considerations

Ensure that all relevant imaging studies and assessments are documented to support the diagnosis.

Physical Therapy

Documentation Requirements

Functional assessments, treatment plans, and progress notes detailing the impact of limb length discrepancy on mobility.

Common Clinical Scenarios

Patients undergoing rehabilitation post-surgery for limb length correction.

Billing Considerations

Documenting the patient's response to therapy and any modifications made to the treatment plan.

Coding Guidelines

Inclusion Criteria

Use M21.70 When
  • According to ICD
  • 10 guidelines, M21
  • 70 should be used when the specific site of the limb length discrepancy is not documented
  • Coders should ensure that the acquired nature of the condition is clearly stated in the medical record

Exclusion Criteria

Do NOT use M21.70 When
No specific exclusions found.

Related ICD-10 Codes

Related CPT Codes

27500CPT Code

Lengthening of limb

Clinical Scenario

Used when a patient undergoes surgical correction for limb length discrepancy.

Documentation Requirements

Surgical notes detailing the procedure and pre-operative assessments.

Specialty Considerations

Orthopedic surgeons must document the rationale for surgery and expected outcomes.

ICD-10 Impact

Diagnostic & Documentation Impact

Enhanced Specificity

ICD-10 Improvements

The transition to ICD-10 has allowed for more specific coding of acquired conditions like unequal limb length, improving the accuracy of patient records and reimbursement processes.

ICD-9 vs ICD-10

The transition to ICD-10 has allowed for more specific coding of acquired conditions like unequal limb length, improving the accuracy of patient records and reimbursement processes.

Reimbursement & Billing Impact

reimbursement processes.

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 documentation is required to support the use of M21.70?

Documentation must include a clear history of the acquired condition, specific measurements of limb lengths, and any associated treatment plans or procedures.