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4. Pediatrics MCQs

Practice Set 61 of 334

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 1201

Topic: 4. Pediatrics

A 10-year-old child with a history of septic arthritis of the hip presents with a progressive leg length discrepancy (LLD). The surgeon is reviewing Shapiro's patterns of LLD progression to plan for future lengthening procedures. Given the nature of post-septic hip destruction, which of the following statements best characterizes the expected LLD progression pattern and its implications for prediction?

. A. It typically follows a Shapiro Type 1 (Upward Slope Pattern), allowing for accurate prediction using the multiplier method.
. B. It is characterized by a Shapiro Type 3 (Upward Slope-Plateau Pattern), indicating a static discrepancy that does not worsen over time.
. C. It often resembles a Shapiro Type 2 (Upward Slope-Deceleration Pattern) or a combination, making absolute mathematical prediction challenging.
. D. It is primarily a Shapiro Type 5 (Upward Slope-Plateau-Downward Slope Pattern), where initial overgrowth is followed by growth arrest.
. E. The LLD is solely due to physeal destruction and does not involve mechanical migration, simplifying prediction.

Correct Answer & Explanation

. C. It often resembles a Shapiro Type 2 (Upward Slope-Deceleration Pattern) or a combination, making absolute mathematical prediction challenging.

Explanation

Correct Answer: CThe case states, 'However, the LLD resulting from post-septic hip destruction is highly complex. It often resembles a Type 2 pattern or a combination of patterns, as the initial physeal destruction is followed by unpredictable mechanical migration. Because types 2 through 5 have periods of acceleration or deceleration, they cannot always be predicted with absolute mathematical certainty. Therefore, continuous monitoring and dynamic surgical planning using Paley's multiplier method are essential...'Option A is incorrectbecause while the multiplier method is used, the LLD pattern is not typically a simple Type 1, which is for linear, predictable discrepancies. The complexity of post-septic hip destruction makes absolute prediction challenging.Option B is incorrectbecause Type 3 is seen in fractured femurs with small, static discrepancies, which does not fit the progressive nature of post-septic hip destruction.Option D is incorrectbecause Type 5 is seen in conditions like rheumatoid arthritis with initial overgrowth followed by arrest, which is not the primary pattern for post-septic hip sequelae.Option E is incorrectbecause the case explicitly mentions that the LLD is due to 'destruction of the proximal femoral growth plate (physis), combined with the continuous superior mechanical migration of the femur,' indicating both factors contribute, and the migration adds complexity.

Question 1202

Topic: 4. Pediatrics

A surgeon is comparing two historical approaches to pelvic support osteotomy for a patient with a destroyed femoral head: the Milch osteotomy versus the modern Paley-Ilizarov double-level reconstruction. The diagram below illustrates the fundamental difference in their biomechanical outcomes. Which of the following statements accurately describes the primary advantage of the Paley-Ilizarov approach over the Milch osteotomy, as depicted?

. A. The Milch osteotomy provides superior pelvic stability due to a more aggressive valgus angulation.
. B. The Paley-Ilizarov reconstruction achieves pelvic support without inducing a secondary deformity at the knee.
. C. The Milch osteotomy allows for simultaneous leg length correction, which the Paley-Ilizarov method cannot.
. D. The Paley-Ilizarov approach requires only a single osteotomy, simplifying the surgical procedure.
. E. The Milch osteotomy restores the mechanical axis to the center of the knee, preventing lateral compartment arthritis.

Correct Answer & Explanation

. B. The Paley-Ilizarov reconstruction achieves pelvic support without inducing a secondary deformity at the knee.

Explanation

Correct Answer: BThe case explicitly states, 'The Milch osteotomy (left) creates pelvic support but induces a severe valgus knee deformity. The Paley-Ilizarov reconstruction (right) solves this by combining two distinct osteotomies: 1. A Proximal Valgus-Extension Osteotomy... 2. A Distal Varus-Lengthening Osteotomy... This elegant, two-level approach solves all components of the deformity simultaneously: pelvic instability, mechanical malalignment, and limb length discrepancy.' The primary advantage is that the Paley-Ilizarov method corrects the iatrogenic deformity created by the proximal osteotomy, specifically restoring the mechanical axis to the knee center, thus preventing the severe valgus knee deformity and lateral compartment arthritis seen with the Milch osteotomy.Option A is incorrectbecause while Milch provided pelvic stability, it did so at a tremendous biomechanical cost to the knee, which is not superior overall.Option C is incorrectbecause the Paley-Ilizarov method specifically includes a distal lengthening osteotomy for LLD correction, whereas the Milch osteotomy does not inherently address LLD.Option D is incorrectbecause the Paley-Ilizarov approach is explicitly described as a 'double-level femoral osteotomy,' requiring two distinct osteotomies.Option E is incorrectbecause the case states the Milch osteotomy 'created a catastrophic valgus deformity at the knee and shifted the mechanical axis far outside the lateral compartment,' leading to lateral compartment arthritis, not preventing it.

Question 1203

Topic: 4. Pediatrics

A 17-year-old male presents for preoperative planning of an Ilizarov hip reconstruction. On a single-leg stance radiograph, the maximum adduction angle of the affected hip is measured at 40 degrees. According to Paley's principles for calculating the proximal osteotomy, what is the required valgus angle for the proximal osteotomy?

. A. 40 degrees
. B. 25 degrees
. C. 55 degrees
. D. 15 degrees
. E. 70 degrees

Correct Answer & Explanation

. C. 55 degrees

Explanation

Correct Answer: CThe case provides the Paley formula for calculating the proximal osteotomy: 'Proximal Valgus Angle = Maximum Adduction Angle + 15° Overcorrection.' Given a maximum adduction angle of 40 degrees, the calculation is 40° + 15° = 55° of required valgus. The 15-degree overcorrection is critical to ensure the femur remains securely locked against the ischium and re-tension the abductor muscles.Option A is incorrectas it does not include the necessary 15-degree overcorrection.Option B is incorrectas it subtracts 15 degrees, which is contrary to the formula.Option D is incorrectas 15 degrees is the overcorrection amount, not the total valgus angle.Option E is incorrectas it represents an arbitrary overcorrection not specified by the formula.

Question 1204

Topic: 4. Pediatrics

During an Ilizarov double-level hip reconstruction, the surgeon performs a proximal valgus-extension osteotomy. According to Paley's Osteotomy Rules, this proximal osteotomy is intentionally created away from the distal segment's true CORA. What is the immediate biomechanical consequence of this specific application of Paley's rules?

. A. Pure angular correction without any translation of the bone segments.
. B. Correction of the mechanical axis with simultaneous restoration of the mLDFA to 87 degrees.
. C. Creation of a secondary translational deformity, specifically a severe lateral Mechanical Axis Deviation (MAD).
. D. Direct restoration of the Joint Line Congruency Angle (JLCA) to 0 degrees.
. E. Elimination of the need for a distal osteotomy, as the correction is complete.

Correct Answer & Explanation

. C. Creation of a secondary translational deformity, specifically a severe lateral Mechanical Axis Deviation (MAD).

Explanation

Correct Answer: CThe case states, 'The Ilizarov hip reconstruction masterfully employs a combination of these rules. A proximal osteotomy is intentionally created away from the distal segment's true CORA, utilizing a modified Rule 2 to create a supportive angulation against the pelvis. This deliberately creates a massive secondary deformity—specifically, a severe lateral Mechanical Axis Deviation (MAD).' This iatrogenic deformity then necessitates the second, distal osteotomy for correction.Option A is incorrectbecause Rule 1 describes an osteotomyatthe CORA, which allows pure angular correction without translation. The proximal osteotomy is intentionallyawayfrom the distal segment's true CORA.Option B is incorrectbecause the proximal osteotomycreatesthe lateral MAD, it does not correct the mechanical axis or restore the mLDFA; that is the role of the distal osteotomy.Option D is incorrectbecause JLCA relates to the knee joint line, and its direct restoration is not the immediate consequence of the proximal osteotomy.Option E is incorrectbecause the creation of the lateral MAD explicitly requires a second, distal osteotomy to correct this iatrogenic deformity.

Question 1205

Topic: Pediatric Upper Extremity & Spine

A 25-year-old patient, who underwent a single-level Milch osteotomy in childhood for septic hip sequelae, now presents with severe lateral knee instability and early-onset medial compartment osteoarthritis of the knee. The orthopedic surgeon attributes these long-term complications primarily to:

. A. Inadequate tensioning of the hip abductor muscles, leading to persistent Trendelenburg gait.
. B. The creation of a severe valgus deformity at the knee due to lateral translation of the distal femur and medial mechanical axis deviation.
. C. Residual hip flexion contracture that was not addressed by the single osteotomy.
. D. The inability of the Milch osteotomy to provide sufficient pelvic support, leading to chronic pelvic obliquity.
. E. Overcorrection of the leg length discrepancy, causing contralateral limb overload.

Correct Answer & Explanation

. B. The creation of a severe valgus deformity at the knee due to lateral translation of the distal femur and medial mechanical axis deviation.

Explanation

Correct Answer: BThe case explicitly details the pitfalls of the Milch osteotomy: 'The severe valgus angulation at the proximal femur translated the entire distal femur laterally. This created a catastrophic valgus deformity at the knee and shifted the mechanical axis far outside the lateral compartment. This single-level approach led to severe patellar instability, rapid lateral compartment arthritis, and an unacceptable cosmetic deformity.' The question describes medial compartment osteoarthritis, which is a direct result of the varus moment induced by the mechanical axis shiftingmedialto the knee, causing medial compartment overload, despite the overall limb appearing valgus. The text states: 'The load-bearing line now falls far medial to the center of the knee, a condition known as Mechanical Axis Deviation (MAD)... This chronic varus force is devastating to the knee joint, leading to... Medial Compartment Overload... Degenerative Arthritis: The combination of ligamentous laxity and asymmetric cartilage overload inevitably precipitates early-onset medial compartment osteoarthritis of the knee.'Option A is incorrectbecause the Milch osteotomy was often successful in eliminating the Trendelenburg limp by providing pelvic support, even if at a cost.Option C is incorrectbecause while flexion contractures can be present, the primary knee complications described are due to the mechanical axis deviation, not directly from an uncorrected flexion contracture.Option D is incorrectbecause the Milch osteotomy's primary goal, and often its success, was in providing pelvic support, even with its other drawbacks.Option E is incorrectbecause the Milch osteotomy does not inherently address LLD, and overcorrection of LLD is not cited as its primary pitfall leading to these specific knee complications.

Question 1206

Topic: Pediatric Hip

A 4-year-old boy presents with right hip pain, a limp, and a temperature of 38.2°C. He refuses to bear weight. Laboratory tests reveal a WBC count of 11,500/mm3, an ESR of 35 mm/hr, and a CRP of 3.5 mg/dL. Based on the modified Kocher criteria (Caird et al.), what is the most appropriate next step in management?

. Reassurance and outpatient follow-up in 48 hours
. Empiric oral antibiotics and observation
. Urgent ultrasound-guided hip aspiration
. MRI of the bilateral hips without contrast
. Application of a Pavlik harness

Correct Answer & Explanation

. Urgent ultrasound-guided hip aspiration

Explanation

The addition of a CRP > 2.0 mg/dL to the Kocher criteria creates an excellent independent predictor of septic arthritis. With fever, inability to bear weight, and elevated CRP, the probability is high, necessitating urgent aspiration.

Question 1207

Topic: 4. Pediatrics

When utilizing the Paley multiplier method to predict leg length discrepancy (LLD) at skeletal maturity for a patient with congenital short femur, which variables are primarily required?

. The child's bone age, current LLD, and the Green-Anderson growth chart
. The child's chronological age, sex, and current LLD
. The child's birth weight, current femoral length, and chronological age
. The mother's height, father's height, and child's bone age
. The child's chronological age, tibial length, and mLDFA

Correct Answer & Explanation

. The child's chronological age, sex, and current LLD

Explanation

The multiplier method developed by Paley is independent of bone age; it relies solely on the child's chronological age, sex, and the current measured discrepancy to predict LLD at maturity for congenital cases.

Question 1208

Topic: 4. Pediatrics

A 2-year-old child presents with a mildly swollen, painful knee and a low-grade fever. Routine synovial fluid cultures are negative at 48 hours. A nucleic acid amplification test (PCR) eventually identifies the causative organism. Which of the following is most likely responsible?

. Staphylococcus aureus
. Streptococcus pneumoniae
. Kingella kingae
. Neisseria gonorrhoeae
. Borrelia burgdorferi

Correct Answer & Explanation

. Kingella kingae

Explanation

Kingella kingae is a fastidious Gram-negative organism that is now a leading cause of pediatric septic arthritis in children under 4. It frequently presents with milder systemic symptoms and requires PCR for reliable detection.

Question 1209

Topic: 4. Pediatrics

A 10-year-old child with a history of severe neonatal septic arthritis of the hip presents with a painless limp. Radiographs demonstrate a completely absent femoral head and neck, with the proximal femur migrating proximally (Choi Type IV). Which salvage procedure is most commonly utilized to improve biomechanics and abductor function?

. Varus derotational osteotomy
. Slipped capital femoral epiphysis pinning
. Pelvic support osteotomy (Ilizarov concept)
. Total hip arthroplasty
. Shelf acetabuloplasty

Correct Answer & Explanation

. Pelvic support osteotomy (Ilizarov concept)

Explanation

For Choi Type IV sequelae (absent head and neck), a pelvic support osteotomy utilizes a proximal valgus-extension osteotomy to stabilize the femur against the pelvis, restoring abductor tension and improving Trendelenburg gait.

Question 1210

Topic: 4. Pediatrics

In a patient with Paley Type 1a Congenital Femoral Deficiency (normal ossification, intact hip and knee joints), what is the typical progression pattern of the leg length discrepancy according to the Shapiro classification?

. An initial exponential increase followed by a plateau
. A steady, constant absolute discrepancy in centimeters
. A constant percentage of inhibition relative to the normal limb
. A slowly decreasing discrepancy over time
. Unpredictable growth requiring yearly bone age assessments

Correct Answer & Explanation

. A constant percentage of inhibition relative to the normal limb

Explanation

Congenital Femoral Deficiency generally follows a Shapiro Type 1 pattern, where the affected limb maintains a constant percentage of growth inhibition relative to the contralateral normal limb throughout development.

Question 1211

Topic: Pediatric Hip

A 2-week-old neonate presents with asymmetric gluteal folds and pseudoparalysis of the right lower extremity. The infant is afebrile with normal inflammatory markers. Ultrasound demonstrates a right hip effusion. What is the most appropriate next step?

. Observation and repeat ultrasound in 1 week
. Application of a Pavlik harness for suspected DDH
. Urgent hip aspiration and surgical drainage
. Intravenous antibiotics without joint aspiration
. MRI of the lumbosacral spine

Correct Answer & Explanation

. Urgent hip aspiration and surgical drainage

Explanation

Neonates with septic arthritis often lack systemic signs like fever or elevated inflammatory markers. Pseudoparalysis and an effusion demand urgent aspiration and drainage to prevent devastating joint destruction.

Question 1212

Topic: Pediatric Upper Extremity & Spine

When predicting the timing of epiphysiodesis utilizing the Green-Anderson growth remaining method, which assessment tool is strictly required to ensure accuracy?

. The multiplier method coefficient tables
. Greulich and Pyle atlas of skeletal development
. Mose concentric circles
. Tanner-Whitehouse sexual maturity grading
. Risser staging of the iliac apophysis

Correct Answer & Explanation

. Greulich and Pyle atlas of skeletal development

Explanation

The Green-Anderson method relies heavily on skeletal age (bone age), not chronological age. The Greulich and Pyle atlas of left hand/wrist radiographs is the standard tool used to determine this parameter.

Question 1213

Topic: 4. Pediatrics

A 10-year-old boy presents with a progressive valgus deformity of the left knee secondary to a distal femoral physeal bar following a Salter-Harris IV fracture. MRI mapping reveals the bar occupies 30% of the cross-sectional area of the physis, located centrally. Skeletal age is 10 years. What is the most appropriate management?

. Observation and shoe lift
. Contralateral distal femoral epiphysiodesis
. Physeal bar resection with interposition material
. Complete ipsilateral distal femoral epiphysiodesis
. Immediate corrective osteotomy without bar resection

Correct Answer & Explanation

. Physeal bar resection with interposition material

Explanation

Physeal bar resection is indicated if the bar occupies less than 50% of the physis and the patient has at least 2 years of growth remaining. Interposition with fat or Cranioplast prevents recurrence of the bony bridge.

Question 1214

Topic: 4. Pediatrics

During limb lengthening via distraction osteogenesis (Ilizarov technique), the optimal rate and rhythm of distraction are critical to bone regenerate formation. What is the standard recommended rate and rhythm?

. 0.25 mm/day divided into 1 increment
. 1.0 mm/day divided into 4 increments
. 1.5 mm/day divided into 2 increments
. 2.0 mm/day divided into 4 increments
. 1.0 mm/day continuous distraction at 1 increment

Correct Answer & Explanation

. 1.0 mm/day divided into 4 increments

Explanation

Ilizarov's fundamental research showed that 1.0 mm per day, divided into four 0.25 mm increments, optimizes the tension-stress effect, producing the best regenerate bone while protecting soft tissues.

Question 1215

Topic: 4. Pediatrics

A 10-year-old undergoes a 5 cm femoral lengthening using a monolateral external fixator. During the consolidation phase, the child develops a severe knee flexion contracture and subluxation. Tightness in which of the following structures is the primary anatomical driver of this complication?

. Hamstrings
. Rectus femoris
. Vastus intermedius
. Iliotibial band
. Gastrocnemius

Correct Answer & Explanation

. Hamstrings

Explanation

Femoral lengthening stretches the quadriceps, specifically the fascial structures and the iliotibial band. However, kneeflexioncontracture and posterior subluxation are primarily driven by tight hamstrings crossing the knee joint posteriorly opposing the lengthening femur.

Question 1216

Topic: Pediatric Lower Extremity

A newborn is diagnosed with Proximal Focal Femoral Deficiency (PFFD). Radiographs demonstrate an absent femoral head, non-existent acetabulum, and a severely shortened, dysplastic femoral shaft. According to the Aitken classification, which class does this represent?

. Class A
. Class B
. Class C
. Class D
. Class E

Correct Answer & Explanation

. Class D

Explanation

In Aitken Class D PFFD, both the acetabulum and femoral head are completely absent, and the proximal femur is severely dysplastic or absent. This represents the most severe form in the Aitken classification.

Question 1217

Topic: 4. Pediatrics
A 5-year-old child presents with a severe leg length discrepancy and limp. History reveals a prolonged NICU stay for prematurity and sepsis. Radiographs show complete absence of the femoral head and neck, with the greater trochanter abutting the ilium. This sequela of infantile septic arthritis is classified as which Choi type?
. Type I
. Type II
. Type III
. Type IV
. Type V

Correct Answer & Explanation

. Type IV

Explanation

The Choi classification describes post-septic hip sequelae. Type I is a normal x-ray with coxa magna. Type II is deformity of the head. Type III is a coxa vara/neck nonunion. Type IV is destruction of both the femoral head and neck.

Question 1218

Topic: 4. Pediatrics
A 2-year-old child presents with an acute onset of a painful, swollen knee and refusal to bear weight. The synovial fluid aspirate has a WBC count of 65,000/mm³. Traditional Gram stain and cultures are negative, but the pathogen is successfully isolated after inoculating the joint fluid into aerobic blood culture vials (BACTEC). What is the most likely causative organism?
. Staphylococcus aureus
. Kingella kingae
. Streptococcus agalactiae
. Haemophilus influenzae type B
. Borrelia burgdorferi

Correct Answer & Explanation

. Kingella kingae

Explanation

Kingella kingae is a fastidious Gram-negative organism that is increasingly recognized as a leading cause of pediatric septic arthritis in children under 4 years of age. It often yields negative results on standard cultures and requires inoculation into blood culture vials for detection.

Question 1219

Topic: 4. Pediatrics

According to the Paley multiplier method, how is the predicted leg length discrepancy at skeletal maturity calculated for a child with a congenital discrepancy?

. Current LLD multiplied by the age- and sex-specific multiplier
. Current LLD divided by the age- and sex-specific multiplier
. Current LLD plus (annual growth rate multiplied by years remaining)
. Current length of the long leg multiplied by the inhibition percentage
. Target adult height multiplied by the current LLD percentage

Correct Answer & Explanation

. Current LLD multiplied by the age- and sex-specific multiplier

Explanation

The Paley multiplier method calculates the LLD at maturity by simply multiplying the current LLD by an age- and sex-specific multiplier. This method is highly accurate and does not require complex serial measurements or skeletal age determination for congenital cases.

Question 1220

Topic: Pediatric Lower Extremity

A 6-year-old boy presents for evaluation of a leg length discrepancy. Radiographs reveal fibular hemimelia. Which of the following physical examination or radiographic findings is most classically associated with this condition?

. Polydactyly of the foot
. Anterior cruciate ligament (ACL) deficiency
. Vertical talus
. Medial ray deficiency
. Patella alta with quadriceps contracture

Correct Answer & Explanation

. Anterior cruciate ligament (ACL) deficiency

Explanation

Fibular hemimelia is a longitudinal deficiency commonly associated with anterior cruciate ligament (ACL) deficiency, ball-and-socket ankle deformities, tarsal coalition, and absent lateral (not medial) rays of the foot.

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