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ICD-10 Guide
ICD-10 CodesM21.751

M21.751

Billable

Unequal limb length (acquired), right femur

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

Code Description

ICD-10 M21.751 is a billable code used to indicate a diagnosis of unequal limb length (acquired), right femur.

Key Diagnostic Point:

Unequal limb length, also known as limb length discrepancy, refers to a condition where one limb is shorter than the other due to various acquired factors. In the case of M21.751, the discrepancy specifically involves the right femur. This condition can arise from several causes, including trauma, surgical interventions, infections, or diseases that affect bone growth and development. Acquired limb length discrepancies can lead to functional impairments, gait abnormalities, and increased risk of osteoarthritis in the affected limb. Clinically, patients may present with complaints of pain, difficulty walking, or compensatory postural changes. Diagnosis typically involves a thorough clinical examination, imaging studies such as X-rays or MRI, and sometimes gait analysis. Treatment options vary based on the severity of the discrepancy and may include physical therapy, orthotic devices, or surgical interventions such as limb lengthening procedures or osteotomies. Accurate coding of this condition is essential for appropriate management and reimbursement.

Code Complexity Analysis

Complexity Rating: Medium

Medium Complexity

Complexity Factors

  • Variability in documentation of limb length discrepancies
  • Differentiation between congenital and acquired conditions
  • Need for precise measurement and clinical correlation
  • Potential for multiple underlying causes requiring detailed history

Audit Risk Factors

  • Inadequate documentation of the cause of the acquired condition
  • Failure to specify the affected limb
  • Lack of supporting imaging studies
  • Inconsistent clinical findings in the medical record

Specialty Focus

Medical Specialties

Orthopedics

Documentation Requirements

Detailed clinical notes including history, physical examination findings, imaging results, and treatment plans.

Common Clinical Scenarios

Patients presenting with post-traumatic limb length discrepancies, osteomyelitis leading to shortening, or post-surgical changes.

Billing Considerations

Ensure that all relevant imaging studies are documented and correlate with the clinical findings to support the diagnosis.

Physical Medicine and Rehabilitation

Documentation Requirements

Comprehensive assessment of functional limitations, treatment goals, and progress notes.

Common Clinical Scenarios

Patients requiring rehabilitation after limb lengthening procedures or those with gait abnormalities due to unequal limb lengths.

Billing Considerations

Focus on functional outcomes and the impact of the limb length discrepancy on daily activities.

Coding Guidelines

Inclusion Criteria

Use M21.751 When
  • According to ICD
  • 10 coding guidelines, M21
  • 751 should be used when the condition is specifically acquired and affects the right femur
  • Coders must ensure that the documentation supports the diagnosis and that any associated conditions are also coded appropriately

Exclusion Criteria

Do NOT use M21.751 When
No specific exclusions found.

Related ICD-10 Codes

Related CPT Codes

27500CPT Code

Osteotomy, femur, for limb lengthening

Clinical Scenario

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

Documentation Requirements

Surgical notes detailing the procedure, indications, and post-operative care.

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 conditions like unequal limb length, improving the accuracy of diagnoses and treatment tracking. M21.751 provides specificity that was not available in ICD-9, facilitating better patient management and reimbursement processes.

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 diagnoses and treatment tracking. M21.751 provides specificity that was not available in ICD-9, facilitating better patient management 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 is the difference between congenital and acquired limb length discrepancy?

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