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4. Pediatrics MCQs

Practice Set 217 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 4321

Topic: 4. Pediatrics
Osteogenesis imperfecta types I and III represent two different clinical severities of the disease. Which of the following best contrasts the underlying collagen defect between classical type I and classical type III OI?
. Type I involves a quantitative defect of structurally normal collagen; Type III involves a qualitative defect with structurally abnormal collagen.
. Type I involves a qualitative defect of structurally abnormal collagen; Type III involves a quantitative defect of structurally normal collagen.
. Both involve quantitative defects, but Type III has a complete absence of type 1 collagen.
. Both involve qualitative defects, but Type I only affects COL1A2.
. Type I is caused by a non-collagenous gene mutation; Type III is caused by COL1A1 mutation.

Correct Answer & Explanation

. Type I involves a quantitative defect of structurally normal collagen; Type III involves a qualitative defect with structurally abnormal collagen.

Explanation

Type I OI is primarily caused by haploinsufficiency (a premature stop codon), leading to a decreased amount (quantitative defect) of structurally normal collagen. Type III is typically caused by a missense mutation (glycine substitution), leading to structurally abnormal collagen (qualitative defect).

Question 4322

Topic: 4. Pediatrics

A 5-year-old child with SMA Type II requires general anesthesia for the placement of a gastrostomy tube. The anesthesiologist must strictly avoid which of the following agents to prevent a life-threatening complication?

. Propofol
. Sevoflurane
. Succinylcholine
. Rocuronium
. Fentanyl

Correct Answer & Explanation

. Succinylcholine

Explanation

Succinylcholine is a depolarizing neuromuscular blocker that must be avoided in patients with denervating diseases like SMA. Its use can cause massive potassium efflux from upregulated extrajunctional acetylcholine receptors, leading to fatal hyperkalemia.

Question 4323

Topic: 4. Pediatrics

A 6-year-old boy with severe Osteogenesis Imperfecta presents with teeth that are opalescent, severely worn, and appear brown-blue. The underlying pathophysiology of this dental manifestation is due to a defect primarily affecting which tooth structure?

. Enamel
. Dentin
. Cementum
. Pulp
. Periodontal ligament

Correct Answer & Explanation

. Dentin

Explanation

Dentinogenesis imperfecta (DI) is common in OI. The defect is in the dentin, which contains type I collagen. The enamel is actually normal but tends to flake off because the underlying dentin lacks structural integrity to support it.

Question 4324

Topic: Pediatric Hip

A 13-year-old obese male presents with left groin and knee pain that has been worsening over 6 months. Radiographs reveal a severe chronic Slipped Capital Femoral Epiphysis (SCFE). He undergoes in situ percutaneous pinning. What is the most significant recognized mechanical risk factor for developing chondrolysis in this patient?

. Patient obesity (BMI > 35)
. Unrecognized penetration of the hardware into the joint space
. Development of avascular necrosis (AVN) of the femoral head
. Performing a prophylactic pinning on the contralateral asymptomatic hip
. Use of a fully-threaded screw rather than a partially-threaded screw

Correct Answer & Explanation

. Unrecognized penetration of the hardware into the joint space

Explanation

Chondrolysis is a devastating complication of SCFE characterized by rapid destruction of the articular cartilage. Unrecognized penetration of the pin/screw into the hip joint space is the most significant mechanical risk factor for chondrolysis. To prevent this, careful fluoroscopic evaluation (e.g., the 'approach-withdraw' technique) is critical.

Question 4325

Topic: Pediatric Lower Extremity

A 4-week-old infant with idiopathic clubfoot is being treated with the Ponseti method. After 5 weeks of serial casting, the cavus, adductus, and varus deformities have completely resolved. However, passive ankle dorsiflexion is only 5 degrees. What is the next most appropriate step in management?

. Continue serial casting for 3 additional weeks to stretch the Achilles tendon
. Perform a percutaneous Achilles tenotomy
. Perform an open posterior medial release
. Transition directly to a foot abduction orthosis (boots and bar)
. Perform an anterior tibial tendon transfer

Correct Answer & Explanation

. Perform a percutaneous Achilles tenotomy

Explanation

In the Ponseti method, after the cavus, adductus, and varus deformities are corrected (which relies on abduction around the talar head), the equinus is addressed. If ankle dorsiflexion is less than 10 to 15 degrees, a percutaneous Achilles tenotomy is indicated. This is required in 80% to 90% of patients with idiopathic clubfoot.

Question 4326

Topic: 4. Pediatrics

A 7-year-old child with spastic quadriplegic cerebral palsy (GMFCS Level V) is evaluated for hip pain and difficulty with perineal hygiene. An AP pelvis radiograph demonstrates a Reimers' migration index of 65% bilaterally. What is the most appropriate surgical intervention to stabilize the hips?

. Adductor and iliopsoas tenotomies alone
. Varus derotational osteotomy (VDRO) of the proximal femur alone
. VDRO of the proximal femur combined with a pelvic osteotomy
. Proximal femoral resection (Castle procedure)
. Bilateral total hip arthroplasty

Correct Answer & Explanation

. VDRO of the proximal femur combined with a pelvic osteotomy

Explanation

In a child with cerebral palsy, a Reimers' migration percentage > 40-50% indicates significant hip subluxation with secondary acetabular dysplasia. Soft-tissue releases alone are inadequate. A reconstructive procedure combining a proximal femoral varus derotational osteotomy (VDRO) and a pelvic volume-reducing osteotomy (e.g., Dega, San Diego, or Pemberton) is the gold standard for reconstruction.

Question 4327

Topic: Pediatric Hip
A 6-week-old female infant, born in a breech presentation, is evaluated for Developmental Dysplasia of the Hip (DDH). A coronal ultrasound of the hip is performed. The alpha angle is measured at 40 degrees and the beta angle at 80 degrees. According to the Graf classification, what is the diagnosis and the most appropriate management?
. Type I hip; observe and reassure the parents
. Type IIa hip; observe with repeat ultrasound in 4 weeks
. Type IIc hip; immediate closed reduction in the operating room
. Type III hip; initiate treatment with a Pavlik harness
. Type IV hip; immediate open reduction and spica casting

Correct Answer & Explanation

. Type III hip; initiate treatment with a Pavlik harness

Explanation

According to Graf's ultrasound classification, a Type III hip has an alpha angle < 43 degrees and a beta angle > 77 degrees, indicating an eccentrically located (subluxated) femoral head with no structural alteration of the acetabular cartilage rim. The standard initial non-operative treatment for a Graf III hip in an infant < 6 months is a Pavlik harness.

Question 4328

Topic: 4. Pediatrics

A 6-year-old child sustains a widely displaced, extension-type supracondylar humerus fracture. On presentation to the emergency department, the hand is pink, warm, and has a brisk capillary refill, but the radial pulse is entirely non-palpable. What is the most appropriate initial step in the management of this patient?

. Immediate vascular surgery consultation for open arterial exploration
. Urgent closed reduction and percutaneous pinning in the operating room
. CT angiography to pinpoint the exact site of brachial artery intimal tear
. Application of a warm compress, elevation, and observation for 24 hours
. Open reduction via an anterior approach with immediate arterial repair

Correct Answer & Explanation

. Urgent closed reduction and percutaneous pinning in the operating room

Explanation

This is a classic 'pulseless, pink hand' scenario in a pediatric supracondylar humerus fracture. The hand remains perfused via collateral circulation despite brachial artery entrapment or kinking at the fracture site. The recommended initial management is urgent closed reduction and percutaneous pinning (CRPP). Pulse typically returns after realignment; if the hand becomes cold/white post-reduction, vascular exploration is indicated.

Question 4329

Topic: 4. Pediatrics
An 8-year-old boy is diagnosed with Legg-Calvé-Perthes disease. During the fragmentation stage, the treating orthopaedist assesses the radiographs for 'head-at-risk' signs described by Catterall. Which of the following is considered a Catterall 'head-at-risk' sign?
. Medial joint space narrowing
. Gage's sign
. Decreased radiodensity of the metaphysis
. Vertical alignment of the physis
. Coxa magna

Correct Answer & Explanation

. Gage's sign

Explanation

Catterall described five 'head-at-risk' signs indicating a poorer prognosis in Perthes disease: 1) Gage's sign (a V-shaped radiolucency in the lateral portion of the epiphysis/metaphysis), 2) calcification lateral to the epiphysis, 3) lateral subluxation of the femoral head, 4) a horizontal growth plate, and 5) metaphyseal cysts.

Question 4330

Topic: 4. Pediatrics
A 3-year-old obese female presents with bilateral bowing of the legs. Standing AP radiographs show a sharp varus angulation at the proximal tibial metaphyses. The metaphyseal-diaphyseal angle (Drennan's angle) is measured at 18 degrees bilaterally. What is the most appropriate management?
. Reassurance and observation, as this is physiologic bowing
. Treatment with bilateral Knee-Ankle-Foot Orthoses (KAFOs)
. Bilateral proximal tibial valgus osteotomies
. Hemiepiphysiodesis of the lateral proximal tibial physis
. Surgical resection of the medial physeal bar

Correct Answer & Explanation

. Treatment with bilateral Knee-Ankle-Foot Orthoses (KAFOs)

Explanation

A metaphyseal-diaphyseal angle (Drennan's angle) > 16 degrees strongly suggests infantile Blount disease rather than physiologic bowing. In children under 3 to 4 years of age with early-stage infantile Blount disease (Langenskiöld stage I or II), bracing with knee-ankle-foot orthoses (KAFOs) is the initial non-operative treatment of choice.

Question 4331

Topic: 4. Pediatrics

A 5-year-old child is evaluated for a painless waddling gait. AP pelvis radiographs reveal a decreased neck-shaft angle and a Hilgenreiner Epiphyseal Angle (HEA) of 65 degrees. A triangular fragment of bone is visible in the inferior aspect of the femoral neck. What is the recommended treatment for this condition?

. Observation with serial radiographs every 6 months
. Spica casting in maximum abduction and internal rotation
. Proximal femoral valgus-producing osteotomy
. In situ percutaneous pinning of the capital femoral epiphysis
. Epiphysiodesis of the greater trochanter

Correct Answer & Explanation

. Proximal femoral valgus-producing osteotomy

Explanation

This patient has developmental coxa vara, characterized by a 'fairbank' triangle and a high Hilgenreiner Epiphyseal Angle (HEA). An HEA > 60 degrees has a high rate of progressive deformity and is an absolute indication for surgery. The treatment of choice is a valgus-producing proximal femoral osteotomy to correct the HEA to < 35-40 degrees, thereby converting shear forces into compressive forces.

Question 4332

Topic: Pediatric Upper Extremity & Spine
A newborn infant presents with severe radial deviation of both wrists. Radiographs confirm bilateral absent radii. Physical examination reveals that the thumbs are present bilaterally. Laboratory evaluation shows a profoundly low platelet count. Which of the following is the most likely diagnosis?
. Fanconi anemia
. Holt-Oram syndrome
. VACTERL association
. TAR (Thrombocytopenia-Absent Radius) syndrome
. Cornelia de Lange syndrome

Correct Answer & Explanation

. TAR (Thrombocytopenia-Absent Radius) syndrome

Explanation

TAR (Thrombocytopenia-Absent Radius) syndrome is classically characterized by the absence of the radius with the preservation of the thumb. This critical clinical feature distinguishes TAR syndrome from Fanconi anemia and Holt-Oram syndrome, where an absent radius is almost universally accompanied by an absent or severely hypoplastic thumb.

Question 4333

Topic: 4. Pediatrics

A 2-year-old child presents with an anterolateral bowing deformity of the left tibia. Radiographs demonstrate a diaphyseal fracture with sclerotic, tapered ends that has failed to heal. This condition, congenital pseudarthrosis of the tibia (CPT), is most highly associated with which of the following systemic disorders?

. Achondroplasia
. Neurofibromatosis type 1
. Osteogenesis Imperfecta
. Marfan syndrome
. Cleidocranial dysplasia

Correct Answer & Explanation

. Neurofibromatosis type 1

Explanation

Anterolateral bowing of the tibia is the hallmark precursor to Congenital Pseudarthrosis of the Tibia (CPT). CPT is highly associated with Neurofibromatosis type 1 (NF1); approximately 50% of patients diagnosed with CPT will have or develop clinical signs of NF1.

Question 4334

Topic: Pediatric Hip

A 12-year-old male presents with acute severe groin pain after jumping off a swing. He is completely unable to bear weight, even with crutch assistance. Radiographs demonstrate a Slipped Capital Femoral Epiphysis (SCFE). What is the approximate risk of avascular necrosis (AVN) in this type of SCFE compared to a 'stable' slip?

. 0-5%
. 10-15%
. 25-50%
. 75-85%
. 95-100%

Correct Answer & Explanation

. 25-50%

Explanation

Loder classified SCFE into 'stable' (able to bear weight with or without crutches) and 'unstable' (unable to bear weight). Unstable SCFE is an acute emergency that carries a high risk of avascular necrosis (AVN), historically ranging from 25% to 50% (often cited around 47%), whereas stable SCFE has an AVN risk of nearly 0%.

Question 4335

Topic: 4. Pediatrics

What radiographic parameter is considered the most reliable and predictive marker for the risk of hip dislocation in a non-ambulatory child with Cerebral Palsy (GMFCS Level IV or V)?

. Acetabular index
. Center-edge angle of Wiberg
. Reimers' migration percentage
. Femoral neck-shaft angle
. Tonnis angle

Correct Answer & Explanation

. Reimers' migration percentage

Explanation

Reimers' migration percentage is the primary tool used in hip surveillance programs for children with cerebral palsy. It measures the percentage of the ossified femoral head outside the lateral margin of the acetabulum (Perkin's line). A migration percentage greater than 30% indicates subluxation and an increased risk for progression to dislocation, particularly in non-ambulatory children (GMFCS IV and V).

Question 4336

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 findings places him in Group C and predicts the poorest clinical outcome?
. No involvement of the lateral pillar on the AP radiograph
. Maintenance of greater than 50% of lateral pillar height
. Exactly 50% maintenance of lateral pillar height with early fragmentation
. Maintenance of less than 50% of lateral pillar height
. Flattening of the femoral head with a non-spherical congruency

Correct Answer & Explanation

. Maintenance of less than 50% of lateral pillar height

Explanation

The Herring Lateral Pillar Classification is highly prognostic in Legg-Calvé-Perthes disease. Group A involves no lateral pillar involvement. Group B involves >50% maintenance of lateral pillar height. Group C involves <50% maintenance of lateral pillar height, which portends a poor outcome with a high risk of developing an aspherical femoral head and early osteoarthritis.

Question 4337

Topic: Pediatric Hip

Which of the following patients presenting with a unilateral Slipped Capital Femoral Epiphysis (SCFE) has the strongest absolute indication for prophylactic in situ pinning of the contralateral hip?

. A 12-year-old boy with a BMI of 35
. A 14-year-old boy with a positive family history of SCFE
. A 10-year-old girl with end-stage renal disease and renal osteodystrophy
. A 13-year-old girl with a retroverted acetabulum
. An 11-year-old boy with delayed skeletal age

Correct Answer & Explanation

. A 10-year-old girl with end-stage renal disease and renal osteodystrophy

Explanation

Endocrine disorders (such as hypothyroidism) and metabolic bone diseases (like renal osteodystrophy) or a history of radiation therapy carry an exceptionally high risk (up to 50-100%) for the development of a bilateral SCFE. While obesity and delayed skeletal age are risk factors, a diagnosed underlying systemic endocrinopathy or metabolic disorder is considered a strong and almost absolute indication for prophylactic contralateral pinning.

Question 4338

Topic: Pediatric Lower Extremity

A 2-year-old girl presents with progressive bowing of her left leg. Standing full-length radiographs demonstrate a marked varus deformity isolated to the proximal tibia. Which of the following radiographic parameters is most strongly predictive of progression to true infantile Blount's disease rather than physiological bowing?

. Tibiofemoral angle greater than 10 degrees
. Metaphyseal-diaphyseal angle greater than 16 degrees
. Mechanical axis deviation passing through the medial compartment
. Epiphyseal-metaphyseal angle greater than 20 degrees
. Lateral distal femoral angle greater than 90 degrees

Correct Answer & Explanation

. Metaphyseal-diaphyseal angle greater than 16 degrees

Explanation

The metaphyseal-diaphyseal angle (Drennan's angle) is the most reliable early radiographic predictor for infantile Blount's disease. An angle > 16 degrees indicates a high likelihood (up to 95%) of progression to Blount's disease, whereas an angle < 10 degrees strongly suggests physiological bowing. Angles between 10 and 16 degrees require close observation.

Question 4339

Topic: 4. Pediatrics

A 4-month-old infant with molecularly confirmed achondroplasia is being evaluated. What is the most common cause of sudden, unexpected infant death in patients with this skeletal dysplasia?

. Progressive hydrocephalus
. Odontoid hypoplasia leading to atlantoaxial instability
. Cervicomedullary compression from foramen magnum stenosis
. Severe progressive thoracolumbar kyphosis
. Congenital cardiac septal defects

Correct Answer & Explanation

. Cervicomedullary compression from foramen magnum stenosis

Explanation

Infants with achondroplasia have a narrow skull base, which can lead to severe foramen magnum stenosis. This stenosis can compress the cervicomedullary junction, resulting in central apnea and sudden infant death syndrome (SIDS). Evaluation typically involves MRI and polysomnography. Suboccipital decompression is indicated if severe compression or apnea is identified.

Question 4340

Topic: Pediatric Lower Extremity
A 2.5-year-old boy treated successfully in infancy for a right idiopathic clubfoot using the Ponseti method returns to the clinic. His parents report worsening of his foot shape over the last 3 months and admit to discontinuing the foot abduction orthosis. Examination reveals dynamic supination and recurrent equinus. What is the most appropriate initial management?
. Achilles tendon lengthening and immediate AFO bracing
. Comprehensive posteromedial surgical release
. Anterior tibial tendon transfer (ATTT)
. Repeat manipulation and serial long-leg casting
. Talectomy

Correct Answer & Explanation

. Repeat manipulation and serial long-leg casting

Explanation

Relapse of clubfoot deformities after Ponseti treatment is most commonly due to poor compliance with bracing. Regardless of the child's age or the presence of a dynamic supination component, the first-line treatment for a relapse is always repeat manipulation and serial long-leg casting to correct the deformities. Once the foot is supple and plantigrade, a surgical procedure such as an Anterior Tibial Tendon Transfer (ATTT) may be indicated to prevent further relapse, but it should not be performed before recasting.

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