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ICD-10 Guide
ICD-10 CodesM21.721

M21.721

Billable

Unequal limb length (acquired), right humerus

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

Code Description

ICD-10 M21.721 is a billable code used to indicate a diagnosis of unequal limb length (acquired), right humerus.

Key Diagnostic Point:

Unequal limb length, or limb length discrepancy, refers to a condition where one limb is shorter or longer than the other. In the case of M21.721, the acquired discrepancy specifically involves the right humerus. This condition can arise from various factors, including trauma, surgical interventions, or diseases that affect bone growth and development. Acquired deformities may result from conditions such as osteomyelitis, fractures that heal improperly, or surgical resections. The clinical implications of unequal limb length can be significant, leading to functional limitations, gait abnormalities, and increased risk of osteoarthritis in the affected limb. Patients may experience discomfort or pain due to compensatory mechanisms that the body employs to maintain balance and mobility. Treatment options often include physical therapy, orthotic devices, or surgical interventions aimed at correcting the length discrepancy. Understanding the underlying cause of the acquired deformity is crucial for effective management and rehabilitation.

Code Complexity Analysis

Complexity Rating: Medium

Medium Complexity

Complexity Factors

  • Differentiating between congenital and acquired conditions
  • Identifying the specific limb affected
  • Documenting the cause of the acquired discrepancy
  • Understanding associated conditions that may complicate coding

Audit Risk Factors

  • Inadequate documentation of the cause of the acquired discrepancy
  • Failure to specify the affected limb
  • Misclassification of congenital versus acquired conditions
  • Lack of supporting clinical evidence for the diagnosis

Specialty Focus

Medical Specialties

Orthopedics

Documentation Requirements

Detailed clinical notes on the patient's history, physical examination findings, and imaging studies that support the diagnosis of unequal limb length.

Common Clinical Scenarios

Patients presenting with post-fracture limb length discrepancies, those with previous surgeries affecting limb length, or individuals with conditions like osteomyelitis.

Billing Considerations

Orthopedic surgeons must document the specific nature of the acquired deformity and any surgical interventions planned or performed.

Physical Therapy

Documentation Requirements

Records of functional assessments, treatment plans, and progress notes that reflect the impact of limb length discrepancy on mobility.

Common Clinical Scenarios

Patients undergoing rehabilitation post-surgery or those receiving therapy for compensatory gait patterns due to limb length differences.

Billing Considerations

Physical therapists should document the functional limitations caused by the discrepancy and the effectiveness of interventions.

Coding Guidelines

Inclusion Criteria

Use M21.721 When
  • According to ICD
  • 10 coding guidelines, M21
  • 721 should be used when the condition is specifically acquired and documented as affecting the right humerus
  • Coders must ensure that the documentation supports the diagnosis and that any associated conditions are also coded appropriately

Exclusion Criteria

Do NOT use M21.721 When
No specific exclusions found.

Related ICD-10 Codes

Related CPT Codes

20610CPT Code

Arthrocentesis, aspiration and/or injection into a major joint or bursa

Clinical Scenario

Used when a patient with unequal limb length requires joint aspiration due to associated pain.

Documentation Requirements

Document the reason for the procedure, including the diagnosis of unequal limb length.

Specialty Considerations

Orthopedic specialists should ensure that the procedure is linked to the diagnosis of limb length discrepancy.

ICD-10 Impact

Diagnostic & Documentation Impact

Enhanced Specificity

ICD-10 Improvements

The transition to ICD-10 has allowed for more specific coding of conditions like unequal limb length, improving the accuracy of data collection and reimbursement processes. M21.721 provides a clear distinction between acquired and congenital conditions, enhancing clinical understanding and treatment planning.

ICD-9 vs ICD-10

The transition to ICD-10 has allowed for more specific coding of conditions like unequal limb length, improving the accuracy of data collection and reimbursement processes. M21.721 provides a clear distinction between acquired and congenital conditions, enhancing clinical understanding and treatment planning.

Reimbursement & Billing Impact

reimbursement processes. M21.721 provides a clear distinction between acquired and congenital conditions, enhancing clinical understanding and 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 is the difference between congenital and acquired limb length discrepancies?

Congenital discrepancies are present at birth and result from developmental issues, while acquired discrepancies develop due to factors such as trauma, surgery, or disease affecting bone growth.