✅ Model Answer: • Imaging study: Scanogram (orthoroentgenogram).
• Purpose: To accurately measure anatomical leg length and quantify leg length discrepancy (LLD).
• Technique: Three separate exposures of the hips, knees, and ankles on a long cassette with a radiopaque ruler to measure the distance from the femoral head to the talar dome (or medial malleolus).

✅ Model Answer: • Anatomical LLD: A true structural shortening of the bony skeleton (femur, tibia, or both). Measured from the femoral head to the medial malleolus on scanogram.
• Functional LLD: A perceived leg length discrepancy due to factors other than bone shortening (e.g., pelvic obliquity, scoliosis, knee flexion contracture, hip abduction contracture, or foot deformities).
• Clinical significance: Functional LLD does not require surgical correction; treatment focuses on the underlying cause. Anatomical LLD may require surgical intervention if symptomatic.

✅ Model Answer: • Scanogram technique:
- Patient lies supine with both legs extended and the feet in a neutral position.
- A long cassette with a radiopaque ruler is placed under the patient.
- Three separate exposures:
1. Hips: Centered on the femoral heads.
2. Knees: Centered on the knee joints.
3. Ankles: Centered on the ankles (talar domes).
- The ruler is used to calibrate measurements.
- Measurement: The distance from the femoral head to the talar dome (or medial malleolus) is measured on both sides, and the difference is calculated as the LLD.

✅ Model Answer: • Indications for scanogram:
- Clinical suspicion of LLD: Limp, pelvic tilt, unequal iliac crest heights, positive block test.
- Quantifying LLD: To determine the exact discrepancy in millimeters.
- Preoperative planning: For epiphysiodesis, limb lengthening, or other corrective surgeries.
- Monitoring progression: Serial scanograms to track LLD over time (e.g., in congenital or post-traumatic cases).
- Assessing treatment response: After surgical intervention.
- Evaluation of scoliosis: To differentiate spinal from lower extremity causes of pelvic obliquity.

✅ Model Answer: • Clinical measurement of LLD:
- True leg length: Measure from the anterior superior iliac spine (ASIS) to the medial malleolus.
- Apparent leg length: Measure from the umbilicus to the medial malleolus (accounts for pelvic obliquity).
- Block test: Place wooden blocks under the shorter leg until the pelvis is level (iliac crests at the same height). The thickness of the blocks gives an estimate of the LLD.
- Gait observation: Observe for limp, pelvic tilt, or Trendelenburg gait.
- Limitation: Clinical measurement is less accurate than scanogram; may be affected by contractures or pelvic obliquity.

✅ Model Answer: • Bone age (left wrist X-ray): Used to predict remaining growth and estimate the final LLD at skeletal maturity.
• Growth remaining:
- Distal femur: ~9 mm/year of growth remaining.
- Proximal tibia: ~6 mm/year of growth remaining.
- Distal tibia: ~3 mm/year of growth remaining.
• Application: If a child with a 3 cm LLD has 2 years of growth remaining, the predicted final LLD may increase by 2-3 cm.
• Treatment decision: Epiphysiodesis is performed when the predicted LLD at maturity is 2-5 cm to equalize leg length.

✅ Model Answer: • Management of 2 cm LLD:
- Observation: If asymptomatic, no intervention is needed.
- Shoe lift (heel lift): For symptomatic patients (limp, pelvic tilt, low back pain). A 2 cm lift is well-tolerated.
- Monitoring: Serial scanograms to track progression.
- No surgical intervention is typically indicated for <2 cm LLD, as it does not cause significant functional impairment.
- Indications for treatment: Only if symptoms (pain, gait abnormality) develop.

✅ Model Answer: • Management:
- Predict final LLD: With 2 years of growth remaining, the LLD may increase by ~2-3 cm (distal femur ~9 mm/yr + proximal tibia ~6 mm/yr = ~15 mm/yr x 2 years = ~3 cm).
- The final LLD is predicted to be ~6.5 cm, which is >5 cm.
- Options:
- Epiphysiodesis: If the final LLD is predicted to be 2-5 cm, epiphysiodesis of the longer leg would be indicated. However, if predicted >5 cm, this alone may not be sufficient.
- Limb lengthening: For predicted LLD >5 cm, lengthening of the shorter leg is often recommended.
- Combination: Epiphysiodesis of the longer leg + lengthening of the shorter leg may be considered.
- Orthopedic referral: For surgical planning.

✅ Model Answer: • Epiphysiodesis: A surgical procedure to stop the growth of a long bone (usually the distal femur, proximal tibia, or proximal fibula) by destroying the physis (growth plate).
• Mechanism: Arrests growth on the longer leg to allow the shorter leg to catch up.
• Indications:
- LLD of 2-5 cm at skeletal maturity.
- Sufficient growth remaining (typically at least 1-2 years) to achieve equalization.
- Performed in growing children (usually before skeletal maturity).
- The timing is critical: must be performed when the remaining growth on the longer leg is equal to the LLD.

✅ Model Answer: • Limb lengthening (distraction osteogenesis): A surgical procedure to lengthen a shorter bone using an external fixator (Ilizarov frame) or internal nail (motorized intramedullary nail).
• Mechanism: After osteotomy (cutting the bone), the bone segments are gradually distracted (1 mm/day) to stimulate new bone formation.
• Indications:
- LLD >5 cm (predicted at skeletal maturity).
- Congenital conditions: Fibular hemimelia, proximal femoral focal deficiency.
- Post-traumatic: Malunion, nonunion.
- Infections: Septic arthritis sequelae.
- Complications: Pain, joint stiffness, nerve injury, infection, regenerate bone fractures.

✅ Model Answer: • Scanogram (plain radiograph):
- Advantages: Lower radiation dose than CT, widely available, less expensive, accurate for measuring anatomical LLD.
- Disadvantages: Higher radiation than clinical measurement, does not provide 3D anatomy, may be affected by patient positioning.
• CT scanogram:
- Advantages: More accurate, can measure rotational deformities, provides 3D anatomy.
- Disadvantages: Higher radiation dose, more expensive, less widely available.
- Clinical use: CT scanogram is often reserved for complex cases (e.g., rotational deformity, difficult anatomy).

✅ Model Answer: • EOS imaging: A low-dose, biplanar (AP + lateral) X-ray system that provides full-body imaging in standing (weight-bearing) position.
• Role in LLD:
- Provides accurate anatomical and functional LLD measurements.
- Allows assessment of pelvic obliquity, scoliosis, and lower limb alignment simultaneously.
- Advantages:
- Very low radiation dose (up to 80% less than conventional X-ray).
- Weight-bearing (functional) assessment.
- Allows 3D reconstruction from 2D images.
- Disadvantages: Not available in all centers, more expensive.

✅ Model Answer: • "Your child has a leg length discrepancy of 3 cm. This means one leg is shorter than the other. It can cause a limp, pelvic tilt, and sometimes back pain."
• "We have done a scanogram (a special X-ray) to measure the exact difference. We will also check your child's bone age to predict how much growth remains."
• "If the discrepancy is small (<2 cm), we may just use a shoe lift. For a 3 cm discrepancy, we may consider a surgical procedure called epiphysiodesis to stop the longer leg from growing so that the shorter leg can catch up."
• "The timing of surgery is important – it should be done when the child has enough growth remaining to equalize the legs."
• "We will monitor your child regularly with repeat scanograms and work with an orthopedic surgeon to decide the best time for intervention."

✅ Model Answer: • Causes of LLD in children:
- Congenital:
- Fibular hemimelia, tibial hemimelia.
- Proximal femoral focal deficiency (PFFD).
- Congenital short femur.
- Hip dislocation (developmental dysplasia of the hip – DDH).
- Traumatic:
- Growth plate injury (physis fracture) → growth arrest.
- Malunion of femur or tibia fracture.
- Infectious: Septic arthritis, osteomyelitis → growth disturbance.
- Neuromuscular: Cerebral palsy, poliomyelitis → unequal growth.
- Vascular: Avascular necrosis (Legg-Calvé-Perthes).
- Tumors: Osteochondroma, fibrous dysplasia.
- Idiopathic.

✅ Model Answer: • Physical therapy role:
- Strengthening: Strengthen the hip abductors and core muscles to improve pelvic stability and reduce limp.
- Stretching: Prevent contractures (hip flexor, hamstring, calf).
- Gait training: Improve walking efficiency and reduce energy expenditure.
- Balance and proprioception: Improve balance and reduce fall risk.
- Preoperative optimization: Strengthen muscles before surgery (epiphysiodesis or lengthening).
- Postoperative rehabilitation: Range of motion, strengthening, and gait training after surgery.
- Shoe lift adjustment: Help the child adapt to a shoe lift (if used conservatively).