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ICD-10 Guide
ICD-10 CodesM21.764

M21.764

Billable

Unequal limb length (acquired), left fibula

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

Code Description

ICD-10 M21.764 is a billable code used to indicate a diagnosis of unequal limb length (acquired), left fibula.

Key Diagnostic Point:

Unequal limb length, particularly when acquired, refers to a condition where one limb is shorter than the other due to various factors such as trauma, surgery, or disease. In the case of M21.764, the focus is on the left fibula, which may have been affected by conditions such as fractures, infections, or surgical interventions that lead to a discrepancy in limb length. This condition can result in functional impairments, gait abnormalities, and increased risk of joint problems due to altered biomechanics. The acquired nature of this deformity distinguishes it from congenital limb length discrepancies, necessitating careful assessment and management. Treatment options may include physical therapy, orthotic devices, or surgical interventions aimed at correcting the length discrepancy and restoring normal function. Accurate coding is essential for appropriate reimbursement and to reflect the complexity of the patient's condition and treatment plan.

Code Complexity Analysis

Complexity Rating: Medium

Medium Complexity

Complexity Factors

  • Differentiating between congenital and acquired conditions
  • Understanding the underlying causes of limb length discrepancy
  • Documenting the specific anatomical site affected (left fibula)
  • Identifying associated conditions or complications

Audit Risk Factors

  • Inadequate documentation of the acquired nature of the condition
  • Failure to specify the affected limb and anatomical site
  • Lack of clarity on the underlying cause of the limb length discrepancy
  • Incorrect coding of associated conditions or complications

Specialty Focus

Medical Specialties

Orthopedics

Documentation Requirements

Detailed clinical notes on the patient's history, physical examination findings, imaging studies, and treatment plans.

Common Clinical Scenarios

Patients presenting with post-traumatic limb length discrepancies, those undergoing corrective surgeries, or individuals with chronic conditions affecting bone growth.

Billing Considerations

Ensure that all relevant surgical procedures and follow-up care are documented to support the coding of M21.764.

Physical Therapy

Documentation Requirements

Progress notes detailing the patient's functional status, treatment interventions, and response to therapy.

Common Clinical Scenarios

Patients receiving rehabilitation for gait abnormalities due to unequal limb length or post-surgical recovery.

Billing Considerations

Documenting the specific goals of therapy and any modifications made to treatment plans based on the patient's progress.

Coding Guidelines

Inclusion Criteria

Use M21.764 When
  • According to ICD
  • 10 coding guidelines, M21
  • 764 should be used when the condition is specifically acquired and affects the left fibula
  • Coders must ensure that the documentation supports the diagnosis and that any associated conditions are also coded appropriately

Exclusion Criteria

Do NOT use M21.764 When
No specific exclusions found.

Related ICD-10 Codes

Related CPT Codes

27400CPT Code

Osteotomy, tibia and/or fibula

Clinical Scenario

Used in cases where surgical intervention is required to correct limb length discrepancy.

Documentation Requirements

Operative reports detailing the procedure, indications, and post-operative care.

Specialty Considerations

Orthopedic surgeons must document the rationale for surgery and any pre-operative assessments.

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 M21.764, improving the accuracy of patient records and facilitating better reimbursement processes.

ICD-9 vs ICD-10

The transition to ICD-10 has allowed for more specific coding of acquired conditions like M21.764, improving the accuracy of patient records and facilitating better 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 is the difference between congenital and acquired unequal limb length?

Congenital unequal limb length is present at birth and often due to genetic factors, while acquired unequal limb length develops later in life due to trauma, surgery, or disease.