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v1.0.0
ICD-10 Guide
ICD-10 CodesM21.73

M21.73

Billable

Unequal limb length (acquired), ulna and radius

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

Code Description

ICD-10 M21.73 is a billable code used to indicate a diagnosis of unequal limb length (acquired), ulna and radius.

Key Diagnostic Point:

Unequal limb length (acquired) involving the ulna and radius refers to a condition where one forearm is shorter than the other due to various factors such as trauma, surgical intervention, or disease processes. This acquired deformity can result from conditions like osteomyelitis, fractures that heal improperly, or surgical resections. Patients may present with functional limitations, altered biomechanics, and compensatory postures that can lead to secondary musculoskeletal issues. The condition can affect daily activities and quality of life, necessitating a multidisciplinary approach for management, including physical therapy, orthotic devices, or surgical correction. Corrective procedures may involve lengthening techniques or osteotomies to restore limb symmetry and function. Accurate coding requires thorough documentation of the underlying cause and any associated conditions.

Code Complexity Analysis

Complexity Rating: Medium

Medium Complexity

Complexity Factors

  • Variability in underlying causes (trauma, surgery, disease)
  • Need for detailed documentation of limb measurements
  • Potential for co-existing conditions affecting coding
  • Differentiation from congenital limb length discrepancies

Audit Risk Factors

  • Inadequate documentation of the cause of unequal limb length
  • Failure to document associated conditions or treatments
  • Misclassification of congenital vs. acquired conditions
  • Lack of detailed clinical notes on functional limitations

Specialty Focus

Medical Specialties

Orthopedics

Documentation Requirements

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

Common Clinical Scenarios

Post-traumatic limb length discrepancies, post-surgical complications leading to unequal limb lengths.

Billing Considerations

Ensure that the cause of the acquired condition is clearly documented to support the use of M21.73.

Physical Therapy

Documentation Requirements

Progress notes detailing functional assessments and treatment plans.

Common Clinical Scenarios

Rehabilitation following corrective surgery for limb length discrepancies.

Billing Considerations

Document functional limitations and progress towards goals to support the need for therapy.

Coding Guidelines

Inclusion Criteria

Use M21.73 When
  • Follow official ICD
  • CM guidelines for coding acquired conditions
  • Ensure that the documentation supports the diagnosis of unequal limb length as acquired, including the specific cause and any associated conditions

Exclusion Criteria

Do NOT use M21.73 When
No specific exclusions found.

Related ICD-10 Codes

Related CPT Codes

27500CPT Code

Lengthening of limb

Clinical Scenario

Used in surgical correction of acquired limb length discrepancies.

Documentation Requirements

Surgical notes detailing the procedure and indications for surgery.

Specialty Considerations

Orthopedic surgeons must document the rationale for surgical intervention.

ICD-10 Impact

Diagnostic & Documentation Impact

Enhanced Specificity

ICD-10 Improvements

The transition to ICD-10 allows for more specific coding of acquired conditions like unequal limb length, improving data accuracy and facilitating better patient management.

ICD-9 vs ICD-10

The transition to ICD-10 allows for more specific coding of acquired conditions like unequal limb length, improving data accuracy and facilitating better patient management.

Reimbursement & Billing Impact

The transition to ICD-10 allows for more specific coding of acquired conditions like unequal limb length, improving data accuracy and facilitating better patient management.

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 needed to support the use of M21.73?

Documentation should include the patient's history, physical examination findings, imaging results, and a clear statement of the acquired nature of the limb length discrepancy.