Menu

4. Pediatrics MCQs

Practice Set 242 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 4821

Topic: 4. Pediatrics

Which zone of the physis (growth plate) is the primary site of cellular abnormality in a patient with achondroplasia?

. Reserve zone
. Proliferative zone
. Hypertrophic zone
. Zone of provisional calcification
. Primary spongiosa

Correct Answer & Explanation

. Reserve zone

Explanation

Achondroplasia is caused by a gain-of-function mutation in the FGFR3 gene, which leads to abnormal inhibition of chondrocyte proliferation. Therefore, the primary histopathological defect manifests in the proliferative zone of the physis.

Question 4822

Topic: Pediatric Hip

A 6-week-old female infant is currently being treated with a Pavlik harness for Developmental Dysplasia of the Hip (DDH). During her 2-week follow-up appointment, the mother reports that the infant is no longer kicking her left leg. On examination, the infant exhibits a lack of spontaneous knee extension on the left side, though ankle and toe movements are intact. What is the most appropriate next step in management?

. Adjust the anterior strap to increase hip flexion
. Adjust the posterior strap to increase hip abduction
. Remove the Pavlik harness and observe for neurologic recovery
. Transition immediately to a rigid hip abduction orthosis (e.g., Ilfeld splint)
. Schedule an emergency closed reduction and spica casting

Correct Answer & Explanation

. Adjust the anterior strap to increase hip flexion

Explanation

The clinical presentation is highly suggestive of a femoral nerve palsy, a known complication of Pavlik harness treatment caused by excessive hip flexion. The femoral nerve becomes compressed beneath the inguinal ligament, leading to decreased quadriceps function (lack of knee extension). The most appropriate management is immediate removal of the harness to allow for neurologic recovery, which typically occurs within days to weeks. Once the nerve recovers, a different method of treatment (such as a rigid orthosis or closed reduction) should be considered.

Question 4823

Topic: 4. Pediatrics

A 12-year-old obese male presents with a 4-week history of left groin pain and a limp. He is diagnosed with a stable left slipped capital femoral epiphysis (SCFE) and undergoes in situ pinning. Prophylactic pinning of the contralateral asymptomatic hip is widely debated but is most strongly indicated in patients with which of the following underlying conditions?

. Type 1 Diabetes Mellitus
. Hypothyroidism
. Achondroplasia
. Neurofibromatosis Type 1
. Marfan Syndrome

Correct Answer & Explanation

. Type 1 Diabetes Mellitus

Explanation

Prophylactic pinning of the contralateral hip in SCFE is generally recommended for patients with endocrine disorders (e.g., hypothyroidism, growth hormone deficiency, panhypopituitarism), renal osteodystrophy, or a history of prior pelvic radiation. These patients have a significantly higher risk of bilateral involvement compared to the idiopathic SCFE population. The modified Oxford bone age score is also used to determine risk, but among the choices provided, hypothyroidism is the primary indication for prophylactic pinning.

Question 4824

Topic: Pediatric Hip
An 8-year-old boy is evaluated for a painless limp and restricted hip abduction. Radiographs confirm Legg-Calvé-Perthes disease in the fragmentation stage. According to the Lateral Pillar (Herring) classification, which radiograph is evaluated, and what is the primary determinant for a 'C' classification?
. Frog-leg lateral radiograph; the anterior pillar retains >50% of its original height
. AP radiograph; the central pillar retains <50% of its original height
. AP radiograph; the lateral pillar retains <50% of its original height
. Frog-leg lateral radiograph; the lateral pillar retains <50% of its original height
. AP radiograph; the medial pillar retains >50% of its original height

Correct Answer & Explanation

. AP radiograph; the lateral pillar retains <50% of its original height

Explanation

The Lateral Pillar (Herring) classification evaluates the AP pelvis radiograph specifically during the fragmentation phase of Legg-Calvé-Perthes disease. It is divided into three groups based on the height of the lateral third of the femoral epiphysis. Group A has no lateral pillar involvement. Group B maintains >50% of lateral pillar height. Group C maintains <50% of lateral pillar height. Age >8 years at onset and a lateral pillar B/C or C grade portend a poor prognosis and typically warrant surgical containment.

Question 4825

Topic: 4. Pediatrics
A 3-year-old child who was successfully treated for an idiopathic right clubfoot via the Ponseti method presents with a relapsed deformity. The parents note that the child walks on the lateral border of the right foot. Examination reveals dynamic supination during the swing phase of gait, but the foot is passively correctable. Which of the following is the most appropriate surgical management?
. Extensive posteromedial soft tissue release
. Split anterior tibial tendon transfer (SPLATT) to the cuboid
. Full tibialis anterior tendon transfer (TATT) to the lateral cuneiform
. Calcaneocuboid joint fusion
. Peroneus brevis to peroneus longus transfer

Correct Answer & Explanation

. Full tibialis anterior tendon transfer (TATT) to the lateral cuneiform

Explanation

In cases of relapsed clubfoot treated via the Ponseti method, dynamic supination during the swing phase is the most common presentation. If the foot is passively correctable (often achieved with a short period of re-casting), the treatment of choice in a child over 2.5-3 years of age is a full tibialis anterior tendon transfer (TATT) to the lateral cuneiform. A split transfer (SPLATT) is not recommended in Ponseti-treated clubfeet because the medial half of the tendon continues to act as a supinator.

Question 4826

Topic: 4. Pediatrics

A 6-year-old girl with spastic quadriplegic cerebral palsy (GMFCS Level V) is evaluated in the multidisciplinary hip surveillance clinic. Her AP pelvis radiograph demonstrates a Reimers migration percentage (MP) of 55% on the right hip with associated acetabular dysplasia. What is the most widely accepted surgical intervention for this degree of subluxation?

. Adductor and iliopsoas tenotomies alone
. Botulinum toxin A injections to the hip adductors
. Proximal femoral varus derotational osteotomy (VDRO) with a pelvic osteotomy (e.g., Dega)
. Shelf arthroplasty
. Proximal femoral resection (Castle procedure)

Correct Answer & Explanation

. Adductor and iliopsoas tenotomies alone

Explanation

In children with cerebral palsy (especially GMFCS levels IV and V), a Reimers migration percentage >40-50% indicates significant hip subluxation that is unlikely to respond to soft tissue release alone. The gold standard surgical management for a displaced and dysplastic hip in this population is a combined procedure: a proximal femoral varus derotational osteotomy (VDRO) combined with a volume-reducing pelvic osteotomy (such as Dega or San Diego) to improve acetabular coverage. Salvage procedures (like resection) are reserved for painful, chronically dislocated, arthritic hips in older patients.

Question 4827

Topic: Pediatric Lower Extremity

A 2-year-old boy is brought to the clinic for bilateral bowing of the lower extremities. The physician is trying to differentiate between physiological genu varum and infantile Blount's disease. Measurement of the metaphyseal-diaphyseal (MD) angle of Drennan on standing AP radiographs is performed. Which of the following MD angles most strongly indicates a high likelihood of progression to true infantile Blount's disease?

. 5 degrees
. 9 degrees
. 12 degrees
. 14 degrees
. 18 degrees

Correct Answer & Explanation

. 5 degrees

Explanation

The metaphyseal-diaphyseal (MD) angle, described by Drennan, is a critical radiographic parameter to differentiate physiological bowing from infantile tibia vara (Blount's disease). An MD angle greater than 16 degrees has a high positive predictive value for progression to Blount's disease. An angle between 10 and 16 degrees requires close follow-up, while an angle less than 10 degrees is typical for physiologic bowing.

Question 4828

Topic: 4. Pediatrics

A 4-year-old female with blue sclerae and a history of multiple long bone fractures after minimal trauma is diagnosed with Osteogenesis Imperfecta (OI). Genetic testing is ordered. The primary pathophysiology of this condition is a mutation in the COL1A1 or COL1A2 genes leading to the substitution of a crucial amino acid in the triple helix of Type I collagen. Which of the following amino acids is abnormally substituted in this disorder?

. Proline
. Hydroxyproline
. Lysine
. Glycine
. Glutamine

Correct Answer & Explanation

. Proline

Explanation

Osteogenesis Imperfecta is predominantly caused by mutations in the COL1A1 or COL1A2 genes, which encode the alpha-1 and alpha-2 chains of type I collagen. The most common and structurally devastating mutation is a point mutation leading to the substitution of glycine by a bulkier amino acid. Glycine normally occupies every third position (Gly-X-Y) in the collagen alpha chain. Its small side chain (a single hydrogen atom) allows the three alpha chains to pack tightly into the triple helix. Substitution disrupts this tight packing, leading to defective collagen (quantitative or qualitative defects).

Question 4829

Topic: 4. Pediatrics

Achondroplasia is the most common form of skeletal dysplasia and short-limb dwarfism. The underlying genetic defect is an activating mutation in the Fibroblast Growth Factor Receptor 3 (FGFR3) gene. In which zone of the epiphyseal growth plate does this mutation primarily exert its inhibitory effect?

. Reserve (resting) zone
. Proliferative zone
. Hypertrophic zone
. Zone of provisional calcification
. Primary spongiosa

Correct Answer & Explanation

. Reserve (resting) zone

Explanation

Achondroplasia is caused by an autosomal dominant, gain-of-function mutation in the FGFR3 gene. FGFR3 normally acts as a negative regulator of bone growth. The mutation leads to constitutive activation of the receptor, which severely inhibits chondrocyte proliferation and differentiation. This primarily affects the proliferative zone of the physis, leading to decreased longitudinal bone growth and the classic rhizomelic dwarfism.

Question 4830

Topic: 4. Pediatrics
A 4-month-old infant is referred to pediatric orthopedics due to an obvious bowing deformity of the right lower leg. Radiographs reveal an anterolateral bow of the tibia with medullary sclerosis and cortical thickening. Based on the most common association with this specific condition, which of the following physical examination findings should the physician actively search for?
. Café-au-lait spots
. Blue sclerae
. Sacral dimple or hair tuft
. Cleft palate
. Preaxial polydactyly

Correct Answer & Explanation

. Café-au-lait spots

Explanation

The clinical and radiographic presentation describes Congenital Pseudarthrosis of the Tibia (CPT), typically preceded by an anterolateral bowing of the tibia. CPT is highly associated with Neurofibromatosis Type 1 (NF-1). More than 50% of patients with CPT have NF-1. Therefore, the physician must thoroughly examine the child for signs of NF-1, such as café-au-lait spots (need 6 or more for diagnosis), axillary/inguinal freckling, or neurofibromas.

Question 4831

Topic: 4. Pediatrics
A 14-year-old male sustains an ankle injury while skateboarding. Radiographs reveal a Salter-Harris III fracture of the anterolateral aspect of the distal tibial epiphysis. This fracture pattern (Tillaux fracture) is specifically dictated by the asymmetric closure of the distal tibial physis. What is the correct chronological order of distal tibial physeal closure?
. Anterolateral, Posteromedial, Central
. Central, Anterolateral, Posteromedial
. Central, Posteromedial, Anterolateral
. Posteromedial, Central, Anterolateral
. Central, Anteromedial, Posterolateral

Correct Answer & Explanation

. Central, Posteromedial, Anterolateral

Explanation

The distal tibial physis undergoes asymmetric closure over an 18-month period. Closure begins centrally, proceeds medially (posteromedial), and finally closes anterolaterally. During this transitional period, an external rotation force causes the anterior inferior tibiofibular ligament (AITFL) to avulse the unfused anterolateral portion of the epiphysis, resulting in a Tillaux fracture (Salter-Harris III).

Question 4832

Topic: 4. Pediatrics

A pediatric orthopedic surgeon is discussing ambulation prognosis with the parents of a child born with myelomeningocele (spina bifida). The infant has a documented neurologic level of L4. Assuming appropriate orthopedic care and bracing are provided, what is the most likely lifelong ambulatory potential for this patient?

. Household ambulator only, relying on a wheelchair for community transport
. Non-ambulator, fully reliant on a wheelchair
. Community ambulator with ankle-foot orthoses (AFOs) and forearm crutches
. Community ambulator requiring no orthoses or walking aids
. Independent ambulator but requires hip-knee-ankle-foot orthoses (HKAFOs)

Correct Answer & Explanation

. Household ambulator only, relying on a wheelchair for community transport

Explanation

Ambulation potential in myelomeningocele correlates directly with the lowest functioning motor level. A patient with an L4 level has functioning hip flexors (L1, L2, L3), hip adductors (L2, L3, L4), knee extensors/quadriceps (L2, L3, L4), and medial hamstrings, as well as tibialis anterior (L4, allowing dorsiflexion). The strong quadriceps function is the primary discriminator for community ambulation. These patients typically function as excellent community ambulators but usually require AFOs (due to absent plantar flexion/gluteal weakness) and crutches to prevent crouch gait and optimize efficiency.

Question 4833

Topic: Pediatric Hip

A 15-month-old child undergoes open reduction for a neglected developmental dysplasia of the hip (DDH) via an anterior approach. During the procedure, several intra-articular anatomical obstacles to reduction are encountered and addressed. Which of the following structures is located most inferiorly and must be incised to allow the femoral head to seat concentrically in the true acetabulum?

. Ligamentum teres
. Inverted limbus
. Pulvinar
. Transverse acetabular ligament
. Iliopsoas tendon

Correct Answer & Explanation

. Ligamentum teres

Explanation

Obstacles to reduction in DDH include extra-articular structures (iliopsoas tendon, adductor longus) and intra-articular structures. The intra-articular obstacles include the pulvinar (fibrofatty tissue in the cotyloid fossa), an elongated/hypertrophic ligamentum teres, an inverted acetabular labrum (limbus), and a contracted transverse acetabular ligament. The transverse acetabular ligament crosses the acetabular notch at the inferior aspect of the joint. It is often contracted in DDH and must be radially incised (not excised) to allow the femoral head to seat fully.

Question 4834

Topic: 4. Pediatrics
The pathogenesis of Legg-Calvé-Perthes disease involves avascular necrosis of the capital femoral epiphysis. In a 6-year-old child, the predominant blood supply to the femoral head is provided by the lateral epiphyseal artery. From which parent vessel does this specific artery originate?
. Obturator artery
. Medial circumflex femoral artery
. Lateral circumflex femoral artery
. Inferior gluteal artery
. Foveal artery (ligamentum teres)

Correct Answer & Explanation

. Medial circumflex femoral artery

Explanation

In children between the ages of 4 and 8 years (the peak age for Perthes disease), the metaphyseal blood supply across the physis decreases dramatically, and the foveal artery provides negligible contribution. The femoral head becomes almost entirely dependent on the lateral epiphyseal artery. This artery is the terminal branch of the medial circumflex femoral artery (MCFA). Disruption or thrombosis of this vessel leads to avascular necrosis of the capital femoral epiphysis.

Question 4835

Topic: 4. Pediatrics

A 6-month-old infant is brought to the emergency department for irritability and swelling of the right knee. Radiographs reveal a distal femoral fracture characterized by a thin layer of metaphyseal bone avulsed at the periphery of the physis. Which of the following best describes the specificity of this injury for non-accidental trauma (child abuse)?

. Low specificity; commonly caused by normal infant rolling
. Moderate specificity; often seen in severe osteogenesis imperfecta
. High specificity; classic 'corner' or 'bucket-handle' fracture
. Low specificity; classic Toddler's fracture
. High specificity; pathognomonic for a direct blow to the knee

Correct Answer & Explanation

. Low specificity; commonly caused by normal infant rolling

Explanation

The description provided is that of a classic metaphyseal lesion (CML), also known as a 'corner' or 'bucket-handle' fracture. These occur due to forceful pulling, twisting, or shaking (shear forces across the primary spongiosa of the metaphysis). CMLs, along with posterior rib fractures, scapular fractures, and sternal fractures, have a very high specificity for non-accidental trauma (child abuse) and mandate a thorough child protection investigation.

Question 4836

Topic: 4. Pediatrics
A 7-year-old boy with spastic diplegic cerebral palsy is classified as Level III on the Gross Motor Function Classification System (GMFCS). Based on this classification, which of the following best describes his expected functional mobility in community settings?
. Walks independently without assistive devices but has difficulty with speed and balance
. Walks with an ankle-foot orthosis but requires no handheld mobility device
. Walks using a handheld mobility device (e.g., walker or crutches) in most indoor settings and uses wheeled mobility for long distances
. Self-mobility is severely limited; relies entirely on manual transport by caregivers
. Uses powered mobility primarily; can stand only with physical assistance

Correct Answer & Explanation

. Walks using a handheld mobility device (e.g., walker or crutches) in most indoor settings and uses wheeled mobility for long distances

Explanation

The GMFCS is a 5-level classification system for cerebral palsy. Level I: Walks without limitations. Level II: Walks with limitations (e.g., struggles with long distances or uneven terrain). Level III: Walks using a handheld mobility device (canes, crutches, or walkers) indoors/outdoors, and may use wheeled mobility when traveling long distances. Level IV: Self-mobility with limitations; may use powered mobility or require assistance. Level V: Transported in a manual wheelchair in all settings (severe limitations in head and trunk control).

Question 4837

Topic: 4. Pediatrics

A 5-year-old child with spastic quadriplegic cerebral palsy presents for a routine visit. Gross Motor Function Classification System (GMFCS) level is V. Radiographs show a migration percentage of 55% bilaterally with an acetabular index of 35 degrees. What is the most appropriate next step in management?

. Observation with repeat radiographs in 1 year
. Bilateral adductor tenotomies alone
. Bilateral varus derotational osteotomies (VDRO) without pelvic osteotomies
. Bilateral VDRO and pelvic osteotomies
. Bilateral hip arthrodesis

Correct Answer & Explanation

. Observation with repeat radiographs in 1 year

Explanation

In a non-ambulatory child (GMFCS V) with a high migration percentage (>50%) and significant acetabular dysplasia (acetabular index >30 degrees), a combined approach including a varus derotational osteotomy (VDRO) of the proximal femur and a pelvic osteotomy (e.g., Dega or San Diego) is required to establish stable hip reduction and prevent painful dislocation. Soft tissue release alone is insufficient at this stage.

Question 4838

Topic: Pediatric Lower Extremity

A 4-year-old boy presents with a recurrent clubfoot deformity after successful initial Ponseti casting and Achilles tenotomy in infancy. The mother notes he drops his foot and walks on the lateral border. Examination reveals dynamic supination during the swing phase of gait. Passive range of motion allows the foot to be brought to neutral. What is the most appropriate management?

. Repeat Ponseti casting followed by a lateral sliding calcaneal osteotomy
. Fractional lengthening of the Achilles tendon alone
. Tibialis anterior tendon transfer to the lateral cuneiform
. Split tibialis posterior tendon transfer
. Triple arthrodesis

Correct Answer & Explanation

. Repeat Ponseti casting followed by a lateral sliding calcaneal osteotomy

Explanation

Dynamic supination during swing phase is a classic presentation of recurrent clubfoot deformity caused by an overactive tibialis anterior pulling against a weakened or lengthened antagonist. Since the deformity is flexible passively, the treatment of choice is transferring the tibialis anterior tendon to the lateral cuneiform to balance the foot dynamically. Bony procedures are reserved for fixed deformities.

Question 4839

Topic: Pediatric Hip

A 12-year-old obese boy presents to the emergency department with severe acute left hip pain after slipping on ice. He is completely unable to bear weight, even with crutches. Radiographs show a severe left Slipped Capital Femoral Epiphysis (SCFE). Which of the following complications is he at greatest risk for compared to a patient who presents with an ability to bear weight?

. Chondrolysis
. Avascular necrosis (AVN)
. Subtrochanteric fracture
. Femoroacetabular impingement (FAI)
. Infection

Correct Answer & Explanation

. Chondrolysis

Explanation

The inability to bear weight defines an unstable SCFE according to the Loder classification. Unstable SCFE has a significantly higher risk of avascular necrosis (AVN), reported to be up to 20-50%, compared to a nearly 0% risk in stable SCFE. Chondrolysis is more commonly associated with unrecognized hardware penetration into the joint.

Question 4840

Topic: Pediatric Hip
A 7-year-old boy is diagnosed with Legg-Calvé-Perthes disease. According to the Herring Lateral Pillar Classification, which of the following is the most important radiographic parameter for determining long-term prognosis?
. Extent of epiphyseal necrosis in the anterior half of the femoral head
. Maintenance of lateral pillar height greater than 50%
. Presence of a subchondral lucency (Crescent sign)
. Extrusion of the femoral head laterally
. Premature physeal closure

Correct Answer & Explanation

. Maintenance of lateral pillar height greater than 50%

Explanation

The Herring Lateral Pillar Classification is the most reliable prognostic indicator for Legg-Calvé-Perthes disease. It assesses the height of the lateral pillar of the femoral head on an AP radiograph during the fragmentation stage. Group A (>100%), Group B (>50%), and Group C (<50%). Patients with <50% lateral pillar height (Group C) have a poor prognosis and a higher likelihood of an aspherical femoral head and early osteoarthritis.

Test Yourself

Switch to an interactive, timed exam simulation to truly master this topic.

On this Page