Leg Length Discrepancy (LLD)

Topic updated on 07/28/16 2:43pm
  • Common causes of LLD 
    • congenital disorders 
      • hemihypertrophy
      • dysplasias
      • PFFD
      • DDH
      • unilateral clubfoot
    • paralytic disorders
      • spasticity (cerebral palsy)
      • polio
    • physis disruption
      • infection
      • trauma
      • tumor
  • Epidemiology
    • 2cm LLD occurs in up to 2/3 of the population
  • Associated conditions
    • back pain
      • increased prevalence of back pain 
    • osteoarthritis
      • decreased coverage of femoral head on long leg side leads to osteoarthritis 84% of the time
    • structural scoliosis
      • LLD increases the incidence of structural scoliosis
    • inefficient gait
    • equinus contracture of ankle
  • Static
    • malunion of femur or tibia
  • Progressive
    • physeal growth arrest
    • congenital
      • absolute discrepancy increases
      • proportion stats the same
  • Symptoms
    • usually asymptomatic
  • Physical exam
    • block testing
      • with the patient standing, add blocks under the short leg until the pelvis is level, then measure the blocks to determine the discrepancy
      • block testing is considered the best initial screening method  
    • tape measurement
      • measure from the anterior superior iliac spine to the medial malleolus with a tape measure
    • evaluate for hip, knee and ankle contractures
      • affect apparent limb length
      • hip adduction contracture causes apparent shortening of adducted side
  • Radiographs
    • teleoroentgenography (scanography) 
      • measure discrepancy with single exposure from 2m away
    • bone age hand films
      • determine bone age with bone age xray (hand)
  • CT Scanography
    • CT scanography is the most accurate diagnostic test with contractures of the hip, knee, or ankle 
LLD Projections
  • General assumptions
    • growth continues until 16 yrs in boys and until 14 yrs in girls 
  • Methods to project LLD at maturity
    • Mosley graph
    • estimation technique    q 
      • leg grows 23 mm/year, with most of that coming from the knee (15 mm/yr)
        • proximal femur - 3 mm / yr (1/8 in)
        • distal femur - 9 mm / yr (3/8 in)
        • proximal tibia - 6 mm / yr (1/4 in)
        • distal tibia - 5 mm / yr (3/16 in)
  • Can be tracked with 
    • Green-Anderson tables 
      • uses extremity length for a given age
    • Moseley straight line graph
      • improves on Green-Anderson method by reformatting data in a graph form
      • accounts for differences between skeletal and chronologic age
      • minimizes error
        • averages serial measurements
    • Multiplier method
      • prediction based on multiplying the current discrepancy by a sex and age specific factor
      • most accurate for congenital LLD
      • 1/2 of final leg length 
        • girls at age 3
        • boys at age 4 
  • Nonoperative
    • shoe lift or observation only q
      • indications
        • < 2 cm projected LLD at maturity
      • outcomes
        • not associated with scoliosis or back pain
  • Operative
    • shortening of long side via epiphysiodesis of femur, tibia, or both
      • indications
        • 2-5 cm projected LLD 
    • limb lengthening of short side
      • indications
        • > 5 cm projected LLD
        • lengthening often combined with a shortening procedure (epiphysiodesis, ostectomy) on long side
    • physeal bar excision
      • indications
        • bony bridge involves <50% of physis
        • at least 2 years left of growth
    • amputation and prosthetic fitting
      • indications
        • non-reconstructable limb
        • > 20 cm projected LLD
Surgical Techniques
  • Distraction osteogenesis (Ilizarov principles)
    • initiation
      • perform osteotomy and place fixator
      • metaphyseal corticotomy to preserve medullary canal and blood supply
    • distraction
      • wait 5-7 days then begin distraction
      • distract ~ 1 mm/day
      • following distraction keep fixator on for as many days as you lengthened
    • concurrent procedures
      • may lengthen over a nail so ex-fix can be removed sooner
      • lengthening often combined with a shortening procedure (epiphysiodesis, ostectomy) on long side
  • Incomplete arrest/ angular deformity
    • open technique
    • percutaneous technique
  • Pin site infections
  • Fracture
  • Delayed union
  • Premature cessation of lengthening
  • Joint subluxation/dislocation
  • Mechanical axis deviation (MAD)  
    • lengthening along the anatomical axis of the femur leads to lateral MAD
    • shortening along the anatomical axis of the femur leads to medial MAD


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Qbank (10 Questions)

(OBQ12.29) At what age does longitudinal growth usually arrest in boys at the distal femur physeal growth plate? Topic Review Topic

1. 18
2. 16
3. 14
4. 12
5. 10

(OBQ11.203) A 13-year-old boy presents with a leg-length discrepancy with the right leg shorter than the left. He has normal height for his age and his skeletal age is equal to his chronologic age. History and examination of Tanner staging reveals that he began puberty 1 month ago. His final leg length discrepancy at skeletal maturity is projected to be 4.0cm. Which of the following surgical options is the most appropriate?
Topic Review Topic

1. Physeal stapling of the medial left tibial and femoral physis now with staged removal of staples at age 16
2. Immediate lengthening of the right femur with ring external fixator
3. Epiphysiodesis of the left femur 1 year after the onset of puberty
4. Epiphysiodesis of the left femur and tibia 6 months from now
5. Epiphysiodesis of the bilateral femurs and shortening of the left tibia now

(OBQ08.6) A 14-year-old boy sustains a significant distal femoral physeal fracture. Assuming that he has a complete growth arrest, what is the predicted leg length discrepency? Topic Review Topic

1. 1cm
2. 2cm
3. 3cm
4. 4cm
5. 5cm

(OBQ07.255) A 9-year-old male sustains the fracture seen in Figure A. If a complete growth arrests occurs, his expected leg length discrepancy at skeletal maturity would be? Topic Review Topic
FIGURES: A          

1. 2 cm
2. 3 cm
3. 4 cm
4. 5 cm
5. 6 cm

(OBQ06.108) A 14-year-old male patient with a leg-length discrepancy undergoes a distal femoral and proximal tibial epiphysiodesis on the longer leg. What is the anticipated amount of correction achieved with this procedure in this child? Topic Review Topic

1. 1.6 cm
2. 2 cm
3. 3.2 cm
4. 4 cm
5. 6.4 cm

(OBQ05.159) A 9-year-old girl presents with a history of juvenile rheumatoid arthritis, and a 20 degree flexion contracture of her left knee. A clinical photo is shown in Figure A. Which of the following is the most accurate method of determining leg length discrepancy in this patient? Topic Review Topic
FIGURES: A          

1. Teloradiograph
2. Orthoradiograph
3. Scanogram
4. CT scanogram
5. Bone scan

(OBQ04.62) A 14-year-old boy has complete growth arrest of his left proximal tibia after a skateboarding injury. He currently has a 3mm leg-length discrepancy with left shorter than the right. A radiograph of the patients left hand, wrist, and fingers demonstrate a bone-age of 14 years. What is the most appropriate management of this patient? Topic Review Topic

1. Observation
2. Left tibial lengthening
3. Right tibia epiphysiodesis
4. Right femur epiphysiodesis
5. Amputation

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