This practice set contains high-yield board review questions covering key concepts in 4. Pediatrics. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.
Question 4001
Topic: 4. Pediatrics
A 5-year-old girl with untreated monoarticular JIA of the right knee presents for evaluation. Her parents note a progressive gait abnormality. On examination, the right knee is warm and swollen with a 15-degree flexion contracture. Which of the following limb length discrepancies is most likely to be present?
Correct Answer & Explanation
. The right leg will be longer due to chronic hyperemia stimulating physeal growth
Explanation
In growing children with monoarticular JIA, chronic inflammation and hyperemia stimulate the adjacent physes. This typically results in limb overgrowth and a longer affected limb.
Question 4002
Topic: 4. Pediatrics
In a child with polyarticular JIA who requires a distal femoral extension osteotomy to correct a severe fixed knee flexion contracture, what is a primary concern if performed before skeletal maturity?
Correct Answer & Explanation
. High risk of iatrogenic physeal arrest
Explanation
Performing corrective osteotomies near open physes in children with JIA carries a notoriously high risk of iatrogenic physeal arrest. Surgeons often delay such procedures until skeletal maturity to prevent exacerbating limb length discrepancies.
Question 4003
Topic: Pediatric Upper Extremity & Spine
A 6-year-old boy falls from the monkey bars and sustains an extension-type supracondylar humerus fracture. Radiographs in the emergency department reveal a Gartland Type III fracture with posterolateral displacement of the distal fragment. Based on this specific displacement pattern, which neurological structure is at the highest risk of injury?
Correct Answer & Explanation
. Anterior interosseous nerve (AIN)
Explanation
In extension-type supracondylar humerus fractures, the direction of displacement of the distal fragment dictates which structures are at risk from the sharp proximal fragment. When the distal fragment is displaced posterolaterally, the proximal fragment is driven anteromedially. This anteromedial spike puts the median nerve (specifically its anterior interosseous nerve branch) and the brachial artery at the highest risk of injury. Conversely, if the distal fragment is displaced posteromedially (the most common pattern), the proximal fragment is driven anterolaterally, putting the radial nerve at risk. The ulnar nerve is most commonly injured in flexion-type supracondylar fractures or iatrogenically during medial pin placement for fixation.
Question 4004
Topic: Pediatric Upper Extremity & Spine
A 6-year-old boy is brought to the emergency department after falling from monkey bars. Radiographs confirm a Gartland type III extension-type supracondylar humerus fracture. On physical examination, the hand is well-perfused and pink, with brisk capillary refill, but the radial pulse is absent. What is the most appropriate next step in management?
Correct Answer & Explanation
. Urgent closed reduction and percutaneous pinning (CRPP) in the operating room.
Explanation
The management of a "pink, pulseless" hand in the setting of a displaced pediatric supracondylar humerus fracture is a classic orthopedic emergency scenario. The absence of a palpable pulse is often due to kinking, spasm, or tethering of the brachial artery over the proximal fracture fragment, rather than a complete transection. Because the hand remains pink and well-perfused (indicating adequate collateral circulation), the immediate next step is urgent closed reduction and percutaneous pinning (CRPP) in the operating room. Reduction relieves the tension on the neurovascular bundle, and the pulse often returns. If the hand were "white and pulseless" (ischemic), urgent reduction is still the first step, but if it remains ischemic after reduction, open vascular exploration is mandated. Delaying reduction for advanced imaging (CT angiogram or Doppler) in a pink, pulseless hand is contraindicated as it delays definitive treatment. Skeletal traction is a historical treatment rarely used today for this indication.
Question 4005
Topic: Pediatric Upper Extremity & Spine
A 6-year-old boy sustains a Gartland type III extension-type supracondylar humerus fracture after falling from monkey bars. Radiographs demonstrate posteromedial displacement of the distal fracture fragment. Based on this specific displacement pattern, which neurological deficit is most likely to be present on initial physical examination?
Correct Answer & Explanation
. Inability to extend the metacarpophalangeal joints of the fingers
Explanation
In extension-type supracondylar humerus fractures, the direction of displacement of the distal fragment dictates which structures are at risk from the sharp proximal fragment. When the distal fragment is displaced posteromedially, the proximal fragment is driven anterolaterally. This anterolateral spike puts the radial nerve at the highest risk of injury. A radial nerve injury would present as an inability to extend the wrist and the metacarpophalangeal (MCP) joints of the fingers (Option B). Conversely, if the distal fragment is displaced posterolaterally, the proximal fragment is driven anteromedially, putting the median nerve (specifically the anterior interosseous nerve, AIN) at risk. AIN injury presents as an inability to flex the IP joint of the thumb and DIP joint of the index finger (the "OK" sign) (Option A). Options C, D, and E describe ulnar nerve deficits, which are more commonly associated with flexion-type supracondylar fractures or iatrogenic injury during medial pin placement.
Question 4006
Topic: Pediatric Upper Extremity & Spine
A 6-year-old boy falls from the monkey bars and sustains an extension-type supracondylar humerus fracture. Radiographs demonstrate that the distal fragment is displaced posteromedially. Based on this specific displacement pattern, which of the following neurological deficits is MOST likely to be observed on physical examination?
Correct Answer & Explanation
. Inability to extend the wrist and digits
Explanation
Correct Answer: B (Inability to extend the wrist and digits)In extension-type supracondylar humerus fractures, the direction of distal fragment displacement dictates which neurovascular structures are at greatest risk due to the relative position of the proximal fragment spike. When the distal fragment displaces posteromedially, the sharp proximal fragment is driven anterolaterally. The radial nerve is located anterolaterally in the distal arm and is therefore the most commonly injured nerve in this specific displacement pattern, leading to an inability to extend the wrist and digits. Conversely, if the distal fragment displaces posterolaterally, the proximal fragment is driven anteromedially, placing the anterior interosseous nerve (AIN) and median nerve at risk (leading to an inability to flex the IP joint of the thumb and DIP of the index finger). Ulnar nerve injuries (numbness in the small finger, weak thumb adduction) are more commonly associated with flexion-type supracondylar fractures or iatrogenic injury during medial pinning.
Question 4007
Topic: 4. Pediatrics
A 3-month-old infant is evaluated for short limbs, frontal bossing, and midface hypoplasia. Radiographs demonstrate rhizomelic shortening of the long bones. What is the mechanism of the primary gene mutation responsible for this condition?
Correct Answer & Explanation
. Gain-of-function mutation in FGFR3
Explanation
Achondroplasia, the most common form of dwarfism, is caused by an activating (gain-of-function) mutation in the Fibroblast Growth Factor Receptor 3 (FGFR3) gene. This overactivity continuously inhibits normal chondrocyte proliferation at the physis, leading to decreased endochondral ossification. Complications can include foramen magnum stenosis and thoracolumbar kyphosis.
Question 4008
Topic: 4. Pediatrics
A newborn is diagnosed with achondroplasia. This condition is caused by a gain-of-function mutation in FGFR3. Which specific region of the physis is primarily affected by this mutation?
Correct Answer & Explanation
. Proliferative zone
Explanation
Achondroplasia involves a quantitative defect in chondrocyte proliferation due to an activating FGFR3 mutation. This suppresses chondrocyte activity in the proliferative zone of the physis, leading to rhizomelic dwarfism.
Question 4009
Topic: 4. Pediatrics
A 4-year-old child with short-trunk dwarfism presents for evaluation. Radiographs show coxa vara, platyspondyly, and hypoplasia of the odontoid. What ocular complication must be carefully screened for in this patient?
Correct Answer & Explanation
. Retinal detachment
Explanation
Spondyloepiphyseal Dysplasia Congenita (SEDc) is caused by a COL2A1 (Type II collagen) mutation. Because Type II collagen is abundant in the vitreous humor of the eye, these patients are at high risk for high myopia and retinal detachment.
Question 4010
Topic: 4. Pediatrics
A 6-month-old infant is evaluated for short stature, a prominent forehead, and a waddling gait. Radiographs reveal rhizomelic shortening of the limbs and narrowing of the interpedicular distances in the lumbar spine. A mutation in which gene is responsible for this condition?
Correct Answer & Explanation
. FGFR3
Explanation
Achondroplasia is caused by a gain-of-function mutation in the FGFR3 gene, which inhibits normal endochondral ossification. A hallmark radiographic finding is the progressive narrowing of the lumbar interpedicular distances.
Question 4011
Topic: 4. Pediatrics
A 12-year-old child presents with a waddling gait and joint pain. Radiographs reveal delayed epiphyseal ossification and a "double-layered" appearance of the patella. What is the most likely diagnosis?
Correct Answer & Explanation
. Multiple epiphyseal dysplasia
Explanation
Multiple epiphyseal dysplasia (MED) often presents with joint pain, waddling gait, and classically a 'double-layered' patella on lateral radiographs. It is commonly caused by an autosomal dominant mutation in the COMP gene.
Question 4012
Topic: 4. Pediatrics
A newborn is examined in the nursery and noted to have a "hitchhiker" thumb, severe rigid clubfeet, and swelling of the external ears (cauliflower ears). Which of the following is the most likely diagnosis?
Correct Answer & Explanation
. Diastrophic dysplasia
Explanation
Diastrophic dysplasia is caused by a defect in the sulfate transporter gene (SLC26A2). Classic clinical features include 'hitchhiker' thumbs, cauliflower ears, cleft palate, and severe rigid clubfeet.
Question 4013
Topic: 4. Pediatrics
A 4-year-old child presents with painful, progressive swelling of the neck and back after a minor fall. Physical examination reveals bilateral congenital shortening and valgus deviation of the great toes. Radiographs show early soft tissue ossification. Which of the following is the primary genetic mechanism for this disease?
Correct Answer & Explanation
. Mutation in the ACVR1 gene
Explanation
Fibrodysplasia ossificans progressiva (FOP) is caused by an activating mutation in the ACVR1 gene, a BMP type I receptor. Biopsy is strictly contraindicated as trauma induces explosive heterotopic ossification.
Question 4014
Topic: 4. Pediatrics
A 12-year-old boy with multiple bony prominences around his knees and wrists is diagnosed with multiple hereditary exostoses. Which of the following best describes the underlying molecular pathophysiology?
Correct Answer & Explanation
. Defective processing of heparan sulfate
Explanation
Multiple hereditary exostoses (MHE) is caused by mutations in the EXT1 or EXT2 genes. These genes encode glycosyltransferases essential for synthesizing heparan sulfate, which is crucial for normal chondrocyte regulation at the growth plate.
Question 4015
Topic: 4. Pediatrics
Which of the following genetic factors is most commonly associated with impaired fracture healing or increased risk of nonunion in humans?
Correct Answer & Explanation
. Polymorphisms in Vitamin D receptor (VDR) gene
Explanation
Polymorphisms in the Vitamin D receptor (VDR) gene have been frequently associated with variations in bone mineral density and susceptibility to fractures, as well as influencing fracture healing outcomes. While other genetic factors can affect bone health, VDR polymorphisms are a well-studied example in the context of fracture healing variability. Type I collagen gene variations are more associated with osteogenesis imperfecta. FGFR3 mutations are associated with achondroplasia.
Question 4016
Topic: 4. Pediatrics
During pediatric bone growth, the diaphysis of long bones typically increases in diameter. This remodeling process, termed periosteal apposition, primarily increases which biomechanical property that enhances the bone's structural integrity?
Correct Answer & Explanation
. Area Moment of Inertia
Explanation
Periosteal apposition, which adds bone to the outer surface, significantly increases the Area Moment of Inertia of the bone. By distributing bone material further from the neutral axis, the bone becomes much more resistant to bending and torsional forces, even if the overall bone mineral density or material properties (elastic modulus) within the cortex remain constant or change slightly. This geometric adaptation is a key mechanism for increasing bone strength during growth and in response to mechanical loading.
Question 4017
Topic: 4. Pediatrics
A patient with osteogenesis imperfecta has abnormally fragile bones. Biomechanically, this fragility is often attributed to both poor material properties (e.g., abnormal collagen) and a reduction in which key geometric property affecting resistance to bending and torsion?
Correct Answer & Explanation
. Area Moment of Inertia
Explanation
In osteogenesis imperfecta, bones are not only qualitatively poor (due to abnormal collagen) but often also quantitatively deficient, exhibiting reduced cortical thickness and overall smaller bone diameters. These geometric deficiencies lead to a significantly reduced Area Moment of Inertia, making the bones less resistant to bending and torsional forces, explaining the high fracture rates. While other factors like density or porosity are relevant, MOI directly quantifies the geometric resistance to these specific loading types.
Question 4018
Topic: 4. Pediatrics
A surgeon applies a unilateral external fixator for a pediatric femoral fracture. To maximize the bending stiffness of the construct, which component of the fixator provides the greatest opportunity for optimization related to its Area Moment of Inertia?
Correct Answer & Explanation
. The distance between the connecting bar and the bone axis
Explanation
The distance between the connecting bar and the bone axis (Option D) provides the greatest opportunity for optimizing the bending stiffness of a unilateral external fixator construct by leveraging the Area Moment of Inertia principles. The stiffness of the frame is highly dependent on this distance; increasing the distance significantly increases the MOI of the overall frame relative to the bone, thus improving bending resistance. While pin diameter (affecting pin MOI) and connecting bar diameter/material (affecting bar MOI) are important, the leverage gained by increasing the bar-to-bone distance has a cubic or even higher power relationship to overall construct stiffness in some models, making it a critical geometric parameter for MOI. Number of pins affects load sharing and interface stability, not directly MOI of the structural members. Coating is not related to MOI.
Question 4019
Topic: 4. Pediatrics
Which of the following describes a common indication for plate removal in children that is less common in adults?
Correct Answer & Explanation
. Arrest of physeal growth due to plate impingement.
Explanation
In children, the presence of growth plates (physes) means that plates applied across or near these structures can impinge upon or damage the physis, leading to growth arrest or angular deformities. Therefore, plates are often removed once healing is complete or if they are crossing a physis and growth remains. While symptomatic prominence, refracture, infection, and non-union can occur in both, physeal arrest is a unique consideration for pediatric patients, making implant removal often necessary to prevent or correct growth disturbances.
Question 4020
Topic: 4. Pediatrics
In the context of pediatric fracture fixation, why might a biodegradable plate be advantageous over a metallic plate in specific circumstances?
Correct Answer & Explanation
. Eliminates the need for a second surgery to remove the implant, avoiding potential growth plate disturbance.
Explanation
Similar to adults, the elimination of a second surgery for hardware removal is a major advantage of biodegradable plates in pediatric patients. This is particularly relevant in children to avoid the risks associated with a repeat anesthetic and surgery, and more importantly, to prevent potential disturbance or damage to the growth plate (physis) if the metallic implant needs removal and is in proximity to or crossing a physis. Biodegradable plates resorb over time, allowing the bone to gradually take over load-bearing, and reducing the risk of growth arrest due to hardware. They are generally not stronger, cheaper, or better visualized than metallic implants.
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