paediatric
Leg Length Discrepancy
advanced
6 min
28 marks
6 questions
Clinical Scenario
A 10-year-old boy presents with a limp and his parents have noticed his left leg appears shorter. He had a proximal tibial fracture at age 5 years which was treated in a cast. On examination, there is apparent limb shortening with pelvic obliquity. Block testing reveals a 4cm discrepancy. His current height is 140cm, and both parents are of average height. He is Tanner stage 2. A scanogram confirms 4cm total shortening (2cm femur, 2cm tibia). The question is whether to lengthen or shorten.
Scanogram (full-length lower limb radiograph) of a 10-year-old child demonstrating left leg length discrepancy of 4cm. The femur is 2cm shorter and the tibia is 2cm shorter on the left compared to the right. Skeletal age markers are visible. The mechanical axes are normal bilaterally. This degree of discrepancy at this age will likely exceed 5cm at maturity and may benefit from lengthening or contralateral epiphysiodesis depending on predicted final height.
Source: Pediatric Lower Extremity Case with Leg Length Discrepancy • PMC518976 • CC-BY
Questions
Question 1 (4 marks)
Describe the causes and classification of leg length discrepancy.
Question 2 (5 marks)
How do you measure and assess LLD?
Question 3 (6 marks)
Explain the methods for predicting LLD at skeletal maturity.
Question 4 (5 marks)
Describe the treatment algorithm and epiphysiodesis timing.
Question 5 (4 marks)
What are the principles of limb lengthening?
Question 6 (4 marks)
What are the complications of treatment?
Exam Day Cheat Sheet
Must Mention
- •Treatment: <2cm observe, 2-5cm epiphysiodesis, >5cm lengthen
- •Prediction: Paley multiplier, Moseley graph, growth remaining
- •Epiphysiodesis timing based on growth remaining
- •Lengthening: 1mm/day (Ilizarov principle)
- •Distal femur 10mm/yr, proximal tibia 6mm/yr
Common Pitfalls
- •Wrong treatment thresholds
- •Missing prediction methods
- •Not calculating timing
- •Missing growth rates
- •Wrong lengthening rate
- •Missing complications