Leg-Length Discrepancy (LLD)

Key Points

• Defined as inequality between the lengths of lower limbs
• Can be congenital or acquired
• Classified as structural (anatomic) or functional
• Clinical significance varies with magnitude of discrepancy
• Treatment approach depends on current discrepancy and predicted discrepancy at maturity

Overview

Leg-length discrepancy is a condition where one lower limb is shorter than the other, measured from the hip to the ground. The difference can range from a few millimeters to several centimeters, with varying clinical significance based on the magnitude.

Etiology

Congenital Causes:

• Proximal Focal Femoral Deficiency (PFFD)
• Fibular Hemimelia
• Tibial Hemimelia
• Developmental Dysplasia of Hip (DDH)
• Hemihypertrophy syndromes:
  • Beckwith-Wiedemann Syndrome
  • Klippel-Trenaunay-Weber Syndrome
  • Neurofibromatosis

Acquired Causes:

• Trauma:
  • Physeal injuries
  • Fractures with malunion
  • Growth plate arrests
• Infection:
  • Osteomyelitis
  • Septic arthritis
• Tumors and tumor-like conditions
• Paralytic disorders
• Radiation therapy

Clinical Presentation

History:

• Age of onset
• Rate of progression
• Associated symptoms:
  • Back pain
  • Hip pain
  • Knee pain
  • Gait abnormalities
• Family history
• Developmental history

Physical Examination:

• Standing Assessment:
  • Pelvic obliquity
  • Compensatory scoliosis
  • Standing alignment
• Gait Assessment:
  • Trendelenburg gait
  • Compensatory mechanisms
• Measurement Techniques:
  • Direct measurement
  • Block test
  • Indirect measurement

Diagnosis & Assessment

Imaging Studies:

• Standing AP radiographs of lower extremities
• Scanogram:
  • Three separate exposures of hips, knees, and ankles
  • Allows precise measurement
• CT scanogram:
  • More accurate than conventional scanogram
  • Lower radiation exposure
• MRI:
  • Useful for soft tissue abnormalities
  • Growth plate assessment

Growth Prediction:

• Moseley Straight Line Graph
• Anderson and Green Growth Remaining Charts
• Multiplier Method

Management

Treatment Guidelines:

• < 2 cm: Observation or shoe lift
• 2-5 cm: Consider epiphysiodesis
• > 5 cm: Limb lengthening procedures

Non-operative Treatment:

• Shoe lifts:
  • Internal lift up to 1.5 cm
  • External lift for larger discrepancies
• Physical therapy
• Regular monitoring

Operative Treatment:

• Epiphysiodesis:
  • Permanent growth arrest
  • Timing crucial
  • Techniques: percutaneous, permanent
• Limb Lengthening:
  • External fixation methods
  • Internal lengthening nails
  • Gradual correction

Complications & Long-term Outcomes

Untreated LLD Complications:

• Chronic back pain
• Degenerative joint disease
• Gait abnormalities
• Functional scoliosis
• Hip and knee osteoarthritis

Treatment Complications:

• Epiphysiodesis:
  • Over/under correction
  • Angular deformity
• Limb Lengthening:
  • Pin tract infection
  • Joint contractures
  • Muscle weakness
  • Nerve injury
  • Delayed consolidation