Limb Length Discrepancies

Limb Length Discrepancies - Uneven Steppers

• Definition: Limb Length Discrepancy (LLD) is a condition characterized by a clinically significant difference in the length of corresponding limbs.
• Types of LLD:
  • True LLD: An actual anatomic shortening of one or more bones in the limb.
  • Apparent LLD: Limbs have equal bony lengths, but appear unequal due to factors like joint contractures (hip, knee, ankle) or fixed pelvic obliquity.

Common Etiologies:

Limb Length Discrepancies - Measure Up!

• History (Key Clues)

  • Birth: Congenital (e.g., hemihypertrophy, fibular hemimelia)
  • Trauma: Physeal injury
  • Infection: Osteomyelitis, septic arthritis affecting physis

• Physical Examination

  • Galeazzi test (Allis sign): Observe knee height (supine, hips & knees flexed) for femoral vs. tibial LLD.
  • Block test: Place calibrated blocks under shorter limb until iliac crests level; quantifies LLD.
  • Assess for: Pelvic obliquity, compensatory/functional scoliosis, Trendelenburg gait.
  • Differentiate: True LLD (measure ASIS to medial malleolus) vs. Apparent LLD (due to adduction/abduction contractures, pelvic asymmetry).

• Measurement Techniques

  Technique	Accuracy	Radiation	Notes
  Tape Measure	↓	None	Screening; high inter-observer variability
  Orthoroentgenogram	Moderate	Moderate	Single long film; prone to magnification error
  Scanogram	↑	↓	Multiple focused X-rays over joints with ruler
  CT Scanogram	Highest	Moderate	Gold Standard; precise, 3D assessment

⭐ CT scanogram is considered the gold standard for accurate LLD measurement, especially for complex cases or when surgical planning is required.

Limb Length Discrepancies - Treat or Wait?

Key considerations for management. Consequences of untreated LLD: - Gait abnormalities (e.g., Trendelenburg) - Chronic back pain - Functional scoliosis - Premature hip/knee Osteoarthritis (OA) Growth prediction uses Moseley straight line graph or Anderson-Green charts.

⭐ Projected LLD at skeletal maturity is crucial for planning treatment in growing children; Moseley charts aid this.

Management algorithm:

Limb Length Discrepancies - Bridging Gaps

• Non-operative: Shoe lift (for < 2 cm discrepancy).
• Operative Options:

-   Techniques: Ilizarov, ISKD, Precice.
-   Rate: $1 \text{ mm/day}$ (e.g., **0.25 mm** QID).
-   Consolidation Index: Healing duration/cm.
![Bone Transport in Tibia with Internal Nail](https://ylbwdadhbcjolwylidja.supabase.co/storage/v1/object/public/notes/L1/Orthopaedics_Pediatric_Orthopaedics_Limb_Length_Discrepancies/987a0a5a-5232-45e8-96ae-66d80029dfbd.webp)

• Complications: Pin tract infection, joint stiffness, nonunion, nerve injury, premature/delayed consolidation.

⭐ The law of tension-stress (Ilizarov principle) is fundamental to successful limb lengthening by distraction osteogenesis.

High‑Yield Points - ⚡ Biggest Takeaways

• Limb Length Discrepancy (LLD) >2-2.5 cm is generally considered clinically significant, often requiring intervention.
• Common etiologies include congenital anomalies (e.g., fibular hemimelia), physeal injury (trauma, infection), tumors, and neuromuscular conditions.
• Accurate measurement using scanogram or CT scanogram is crucial; always assess skeletal maturity.
• Management strategy depends on magnitude and growth remaining: shoe lift (<2 cm), epiphysiodesis (2-5 cm with growth potential), or limb lengthening (>5 cm).
• Ilizarov technique (distraction osteogenesis) is a key method for significant limb lengthening.
• Potential complications of lengthening procedures include pin-tract infections, joint contractures/stiffness, and neurovascular injury.