MCQs – Lower Extremity 1

Modern Study Review (AI-Generated)

High-Yield Summary

This topic is a staple of the Royal College exam, focusing heavily on pediatric lower extremity deformities, fracture management, and growth-related decision-making. The single most important clinical trade-off often lies between timing and type of intervention—particularly in Blount disease surgery timing and leg length discrepancy treatment thresholds. The examiner frequently forces a choice between conservative bracing versus surgical correction based on patient age and deformity severity. While classic exam answers favor early surgery or rigid thresholds, modern practice increasingly emphasizes individualized growth modulation and minimally invasive techniques guided by precise imaging and growth prediction models.

High-Yield Decision Matrix

Active Recall Q&A

Femur Fracture Management

Q: What is the preferred treatment for a multi-traumatized child with head injury and femur fracture?
A: ORIF is preferred; external fixation is acceptable; traction alone is insufficient.
Related Pearl: Traction alone risks malunion and instability in multi-trauma; early rigid fixation improves mobilization and reduces complications.

Q: Why is antegrade standard intramedullary nailing contraindicated in skeletally immature femurs?
A: It carries an unacceptable risk of avascular necrosis (AVN).
Related Pearl: The femoral head blood supply is vulnerable in immature patients, especially when nails cross the piriformis fossa.

Blount Disease

Q: What is the recommended bracing for a 2.5-year-old child with Blount disease?
A: Single upright bracing using Denis/Brown boots and bar with midline upright and knee straps applying valgus force.
Related Pearl: Early bracing before age 4 optimizes correction and reduces internal tibial torsion by externally rotating the feet.

Q: When is the best time to perform surgery for Blount disease?
A: Between 4 and 5 years of age.
Related Pearl: Surgery delayed beyond 4 years often leads to poorer outcomes and more invasive procedures.

Osteochondritis Dissecans

Q: What is the most significant prognostic factor in osteochondritis dissecans?
A: Skeletal maturity.
Related Pearl: Healing potential declines sharply after physeal closure, emphasizing early diagnosis.

Leg Length Discrepancy

Q: At what ages do girls and boys typically stop growing for leg length discrepancy calculations?
A: Girls at 14 years; boys at 16 years.
Related Pearl: These ages guide timing for growth modulation procedures like epiphysiodesis.

Q: What are the growth rates of the distal femoral and proximal tibial physes?
A: Distal femoral physis grows ~1 cm/year; proximal tibial physis grows ~0.6 cm/year.
Related Pearl: Accurate growth rates are essential for predicting final leg length and planning interventions.

Q: What treatment is recommended for leg length discrepancies of 0-2 cm?
A: Shoe lift.
Related Pearl: Small discrepancies rarely require surgery and can be managed conservatively.

Q: What treatment is recommended for leg length discrepancies of 2-5 cm?
A: Epiphysiodesis.
Related Pearl: Precise timing is critical to avoid over- or under-correction.

Q: What treatment is recommended for leg length discrepancies of 5-15 cm?
A: Leg lengthening procedures.
Related Pearl: Lengthening carries risks including infection, joint stiffness, and prolonged rehabilitation.

Q: What is the management for leg length discrepancies greater than 15 cm?
A: Amputation is often considered.
Related Pearl: Functional outcomes with prosthetics may surpass those of extensive lengthening in very large discrepancies.

Q: Why must you be cautious when shutting down the growth plate on the contralateral side in a short child?
A: It may exacerbate overall short stature.
Related Pearl: Growth modulation should consider total height potential to avoid unintended height loss.

Fractures and Deformities

Q: What type of injury causes triplane fractures?
A: Lateral rotation injuries.
Related Pearl: Triplane fractures involve epiphysis, physis, and metaphysis, requiring CT for accurate assessment.

Q: How does posteromedial tibial bowing differ from anterolateral bowing?
A: Posteromedial bowing is detected at birth, usually resolves, and mainly causes leg length discrepancy; anterolateral bowing is associated with congenital pseudarthrosis.
Related Pearl: Differentiation is critical as anterolateral bowing often requires surgical intervention.

Q: What complication is common after proximal metaphyseal tibial fractures despite anatomical reduction?
A: Late valgus deformity.
Related Pearl: Etiology is unclear; close follow-up is essential to detect and manage deformity early.

Femoral Anteversion and Muscle Transfer

Q: What surgical intervention may be needed for a 9-year-old with severe femoral anteversion and minimal passive external rotation?
A: Femoral osteotomy at the intertrochanteric level.
Related Pearl: Intertrochanteric osteotomy corrects rotational deformity while preserving growth plates.

Q: What nerve root function is required for a Sharrard transfer of iliopsoas to greater trochanter?
A: L1 and L2 function.
Related Pearl: Adequate innervation is necessary for successful muscle transfer and functional improvement.

Meniscus and Ankle Deformities

Q: Which type of discoid meniscus has the poorest prognosis?
A: Wrisberg type.
Related Pearl: The Wrisberg type lacks normal meniscal attachments, leading to instability and higher failure rates.

Q: What conditions are associated with a ball and socket ankle joint?
A: Short femur, fibular hemimelia, hypoplastic lateral femoral condyle, absent lateral foot rays, and tarsal coalition.
Related Pearl: This deformity is a response to hindfoot stiffness and is not seen with cavus foot deformity.

Physeal Closure and Rotational Osteotomies

Q: Which part of the distal tibial physis closes last?
A: The anterolateral aspect.
Related Pearl: This area is the site of Tillaux fractures in adolescents.

Q: When is femoral rotational osteotomy indicated in adolescents with intoeing?
A: Medial hip rotation >85°, external rotation <10°, or CT anteversion >50°.
Related Pearl: Surgery is deferred until after age 10 due to natural improvement.

Q: Why should rotational osteotomies generally not be performed before age 10?
A: Because children tend to improve spontaneously until this age.
Related Pearl: Premature surgery risks unnecessary intervention and complications.

Q: What tibial rotational deformity angle indicates pathologic internal tibial torsion?
A: Medial thigh-foot angle >10°.
Related Pearl: This threshold guides surgical correction decisions.

Q: What tibial rotational deformity angle indicates pathologic external tibial torsion?
A: Lateral thigh-foot angle >35°.
Related Pearl: Excessive external torsion can cause gait abnormalities and requires intervention.

Classic Clinical Notes

• A multi-traumatized child with head injury and femur fracture should be treated with ORIF, even if in traction that is keeping things well aligned. PERIOD. External fixation would be acceptable too.

• Antegrade standard intramedullary nailing of a femur in a skeletally immature patient has an unacceptable risk of AVN.

• A 2.5 year old child with Blount’s is a candidate for single upright bracing. The braces we use are a Denis/Brown boots and bar system with a single midline upright that has straps for the knees. The straps pull the knees in towards midline while the boots and bar keep the feet apart, thus applying a valgus force to the knees. The boots and bar is also helpful to reduce the internal tibial torsion that develops with this deformity – you can point the toes outwards! The best results are to perform the surgery before the age of 4 – so get on and treat this kid with bracing NOW. If he is not corrected by age 4, you should probably do the surgery.

• One of the multiple choice questions asks about when the best time is for a child to undergo operative treatment for Blounts – depending on who you read, it is 4-5 years.

• The most significant factor in the prognosis of osteochondritis dessicans is skeletal maturity. Also important I guess is the size of the lesion, but really, skeletal maturity has the greatest influence on healing, and this is what it is all about.

• For calculating leg length discrepancy, keep in mind the arithmetic method;
• Girls stop growing at age 14; boys stop growing at age 16.
• The distal femoral physis grows about 1 cm per year, the proximal tibial physis grows about .6 cm per year.

• For deciding what to do about leg length discrepancy, keep in mind what the guidelines are for ultimate discrepancy at skeletal maturity:
• For 0-2 cm – shoe lift
• For 2-5 cm – epiphyseodesis
• For 5-15 cm – leg lengthening
• For greater than 15 cm – probably better to amputate

• You can always gain a little by shutting down the growth plate of the other side – beware the kid that is already pretty short!

• Triplane fractures are lateral rotation injuries.

• Posteromedial bowing of the tibia is often detected at birth – it is different from the anterolateral bowing of congenital pseudarthrosis. It typically resolves to the most extent, and the biggest thing to worry about is LEG LENGTH discrepancy.

• For proximal metaphyseal fractures of the tibia, even when reduced anatomically, there is an usual preponderance of late valgus deformity that you need to watch for. The etiology of this is unclear.

• For a 9 year old with severe femoral anteversion (with barely any passive external rotation), you may need to do femoral osteotomy at the intertrochanteric level.

• For a Sharrard transfer of iliopsoas to GT – need L1/2 function.

• For a discoid meniscus, the Wrisberg type has the poorest prognosis.

• A ball and socket ankle joint is associated with short femur, fibular hemimelia, hypoplastic lateral femoral condyle, absent rays on the lateral aspect of the foot, and tarsal coalition. (In fact, some say that it is a response of the ankle to the stiffness of the hindfoot in tarsal coalition) It is not seen with cavus foot deformity.

• The anterolateral aspect of the distal tibial physis closes last – ie. Tillaux fracture.

• For the intoe adolescent – there are some guidelines about when to pull the trigger on their osteotomies:
• Rotational osteotomy of the femur is indicated if medial hip rotation is more than 85 and external rotation is less than 10, or if on CT scan their anteversion is greater than 50 degrees.
• In general, rotational osteotomies should not be performed before the age of 10 because kids tend to improve up till this point.
• On the tibia, a medial thigh foot angle (or transmalleolar angle) of more than 10 degrees is probably sufficiently pathologic internal tibial torsion to do something.
• On the tibia, a lateral thigh foot angle greater than 35 degrees is sufficiently pathologic external tibial torsion to do something.

Last Updated on January 25, 2026 by Christian Veillette