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4. Pediatrics MCQs

Practice Set 215 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 4281

Topic: Pediatric Hip

A 10-year-old boy presents with a sudden onset of left hip and knee pain, non-weight-bearing. Radiographs show a unilateral left Slipped Capital Femoral Epiphysis (SCFE). Further workup reveals a significantly elevated TSH and low T4 levels. What is the most important clinical implication of these endocrinological findings regarding his SCFE?

. The SCFE is likely chronic and requires a more aggressive surgical approach.
. He is at increased risk for contralateral SCFE and future slipped progression, even after surgical fixation.
. The SCFE is likely stable and will respond well to conservative management.
. He requires emergent endocrine consultation, but it does not impact SCFE management.
. The endocrinological disorder makes him a poor surgical candidate for in situ pinning.

Correct Answer & Explanation

. He is at increased risk for contralateral SCFE and future slipped progression, even after surgical fixation.

Explanation

Slipped Capital Femoral Epiphysis (SCFE) is more commonly associated with obesity and rapid growth. However, SCFE occurring at an atypical age (e.g., younger than 10 or older than 16) or in patients with unusual body habitus should raise suspicion for an underlying endocrine disorder. Hypothyroidism (elevated TSH, low T4) is one such disorder strongly associated with SCFE. The most important clinical implication of finding an endocrine disorder, particularly hypothyroidism, is that these patients have a significantly higher risk of contralateral SCFE (often synchronous or metachronous) and may be at increased risk of further slip progression even after initial surgical fixation. Therefore, prophylactic pinning of the contralateral hip is often recommended in these cases, and close follow-up is essential. The endocrine disorder itself does not necessarily make him a poor surgical candidate, nor does it mean the SCFE is stable or will respond to conservative management. The need for endocrine consultation is clear, but it directly impacts the management strategy for the SCFE, specifically regarding contralateral risk.

Question 4282

Topic: 4. Pediatrics
A 6-year-old child with cerebral palsy (GMFCS Level III) presents with progressive crouch gait, bilateral hip flexion contractures (30 degrees), knee flexion contractures (25 degrees), and ankle equinus (20 degrees). She has undergone extensive physical therapy and bracing without significant improvement. What is the most appropriate single-stage surgical plan to address her gait pathology?
. Bilateral hamstring lengthening and Achilles tendon lengthening.
. Bilateral distal femoral extension osteotomy and Achilles tendon lengthening.
. Bilateral hip flexor release, hamstring lengthening, distal femoral extension osteotomy, and Achilles tendon lengthening.
. Bilateral hip flexor release and posterior capsulotomy of the knee.
. Single-event multilevel surgery (SEMLS) including appropriate soft tissue releases and bony corrections.

Correct Answer & Explanation

. Single-event multilevel surgery (SEMLS) including appropriate soft tissue releases and bony corrections.

Explanation

This child with cerebral palsy (GMFCS Level III) presents with a classic 'crouch gait' pattern involving multiple fixed flexion deformities at the hips, knees, and ankles. In such cases, isolated procedures (Options A, B, D) are often insufficient to address the complex, multilevel pathology. Single-event multilevel surgery (SEMLS) (Option E) is the gold standard for correcting multiple fixed deformities in children with cerebral palsy. SEMLS involves performing all necessary soft tissue releases (e.g., hip flexor release, hamstring lengthening, Achilles tendon lengthening) and bony corrections (e.g., distal femoral extension osteotomy for persistent knee flexion contracture) in a single operative session. This approach aims to restore more physiological alignment and improve gait efficiency and energy expenditure. Performing multiple surgeries at different times increases morbidity and may lead to compensatory deformities. Therefore, a comprehensive, single-stage multilevel approach is most appropriate.

Question 4283

Topic: 4. Pediatrics

A 3-year-old child presents with a high-energy Salter-Harris type IV fracture of the distal tibia, involving the medial malleolus and extending into the weight-bearing articular surface. The fracture is displaced by 4mm. Which of the following is the most appropriate management strategy to prevent long-term complications?

. Closed reduction and long-leg cast immobilization for 6 weeks.
. Open reduction and internal fixation (ORIF) with percutaneous screws avoiding the physis.
. Percutaneous pinning of the fracture fragments without open reduction.
. Open reduction and internal fixation (ORIF) with smooth K-wires or screws placed parallel to the physis, carefully achieving anatomic reduction.
. Observe for 2 weeks, then consider cast immobilization if swelling subsides.

Correct Answer & Explanation

. Open reduction and internal fixation (ORIF) with smooth K-wires or screws placed parallel to the physis, carefully achieving anatomic reduction.

Explanation

Salter-Harris type IV fractures involve both the epiphysis and metaphysis, crossing the physis and entering the joint. Anatomic reduction, especially of the articular surface, is crucial to prevent growth arrest (due to physeal damage) and premature degenerative arthritis. A displacement of 4mm in a Salter-Harris IV fracture requires operative intervention. Closed reduction (Option A) is unlikely to achieve and maintain anatomic reduction, especially of the articular surface. Percutaneous pinning without open reduction (Option C) risks inadequate reduction. Options B and D both involve ORIF, but the critical distinction is the method of fixation. Screws crossing the physis (Option B) are generally avoided in children unless absolutely necessary, and if used, must be removed promptly. Smooth K-wires or screws placed parallel to the physis (Option D) are preferred to minimize physeal damage while achieving stable fixation after an anatomic open reduction. Option E is inappropriate for a displaced articular fracture in a child. Therefore, ORIF with meticulous anatomic reduction and appropriate fixation is key.

Question 4284

Topic: Pediatric Hip
A 4-year-old child presents with progressive bilateral hip pain and a limping gait. Radiographs show flattening and fragmentation of both femoral heads, consistent with Legg-Calvรฉ-Perthes disease (LCPD). His Catterall classification is Group III on the right and Group II on the left. The right hip has signs of early subluxation. What is the most appropriate initial management for the right hip, given the severity?
. Strict bed rest and non-weight bearing until healing occurs.
. Observation with activity restriction and regular physiotherapy.
. Containment surgery, such as a varus osteotomy of the femur or Salter innominate osteotomy.
. Core decompression of the femoral head.
. Arthroscopic debridement of the joint capsule.

Correct Answer & Explanation

. Containment surgery, such as a varus osteotomy of the femur or Salter innominate osteotomy.

Explanation

LCPD management aims to contain the femoral head within the acetabulum to maintain its spherical shape during revascularization and remodeling. For a 4-year-old with Catterall Group III and early subluxation, containment surgery (Option C) is often indicated. A varus osteotomy of the femur or a Salter innominate osteotomy are common procedures to improve femoral head coverage. Strict bed rest (Option A) is rarely indicated now and has significant downsides. Observation (Option B) may be appropriate for very young children with limited involvement (e.g., Catterall I/II), but not for Group III with subluxation. Core decompression (Option D) is primarily for adult avascular necrosis. Arthroscopic debridement (Option E) is not a primary treatment for LCPD. Surgical containment offers the best chance to prevent severe deformity and osteoarthritis in this specific scenario.

Question 4285

Topic: 4. Pediatrics

A 6-year-old child presents with progressive weakness and contractures in multiple joints, including bilateral hip flexion, knee flexion, and ankle equinovarus deformities. This condition was noted at birth and has worsened. Passive range of motion is severely limited. Neurological examination reveals normal sensation but decreased muscle mass. This clinical presentation is most consistent with which of the following diagnoses?

. Developmental Dysplasia of the Hip (DDH).
. Cerebral Palsy (CP).
. Juvenile Idiopathic Arthritis (JIA).
. Spina Bifida.
. Arthrogryposis Multiplex Congenita (AMC).

Correct Answer & Explanation

. Arthrogryposis Multiplex Congenita (AMC).

Explanation

The presentation of progressive weakness, severe contractures in multiple joints present at birth and worsening, and severely limited passive range of motion is classic for Arthrogryposis Multiplex Congenita (AMC) (Option E). AMC is a non-progressive condition characterized by multiple congenital joint contractures. DDH (Option A) primarily affects the hip and is typically isolated. Cerebral Palsy (Option B) is a non-progressive neurological disorder, but contractures are usually secondary to spasticity or dystonia, and often not present from birth in such a severe, widespread, fixed manner. JIA (Option C) is an inflammatory arthritis, typically manifesting later in childhood with joint swelling and pain, not congenital contractures. Spina Bifida (Option D) involves a neural tube defect and often results in neurological deficits and associated deformities, but the widespread, severe, non-progressive contractures are more typical of AMC.

Question 4286

Topic: 4. Pediatrics

A 3-year-old child presents with a congenital pseudarthrosis of the tibia (CPT) that has failed multiple previous attempts at bone grafting and immobilization. The defect is significant, and there is persistent non-union with progressive deformity. Considering current treatment strategies for recalcitrant CPT, which of the following offers the most promising long-term outcome for achieving union and preventing refracture?

. Repeated conventional bone grafting with internal fixation
. Application of an Ilizarov external fixator for compression-distraction osteogenesis
. Vascularized free fibular graft to bridge the defect
. Amputation below the knee due to high recurrence rates
. Continuous casting and observation

Correct Answer & Explanation

. Vascularized free fibular graft to bridge the defect

Explanation

Congenital pseudarthrosis of the tibia is notoriously difficult to treat, with high rates of non-union and refracture. While Ilizarov fixation can be effective, vascularized free fibular grafting is often considered one of the most promising techniques for recalcitrant cases or those with large defects, due to its ability to provide live, osteoinductive bone with its own blood supply. This significantly enhances the chances of union and reduces refracture rates compared to conventional bone grafting. Amputation is a salvage procedure considered after multiple failed attempts and significant complications, not usually an initial 'most promising' option. Repeated conventional grafting without advanced techniques often fails in these complex cases. Continuous casting is rarely effective for established pseudarthrosis.

Question 4287

Topic: Pediatric Hip

A 12-month-old infant is diagnosed with unilateral developmental dysplasia of the hip (DDH) after having failed a trial of Pavlik harness treatment initiated at 6 months of age. Clinical examination reveals a reducible but unstable hip. What is the most appropriate next step in management?

. Another trial of Pavlik harness for an extended duration
. Initiation of an abduction orthosis (e.g., hip abduction brace)
. Closed reduction under general anesthesia followed by spica cast application
. Open reduction with a capsulorrhaphy and possibly a pelvic osteotomy
. Observation with serial ultrasounds until 18 months

Correct Answer & Explanation

. Closed reduction under general anesthesia followed by spica cast application

Explanation

For a 12-month-old infant with DDH that has failed Pavlik harness treatment, the hip is past the age where harness treatment is typically effective. Given that the hip is reducible but unstable, closed reduction under general anesthesia followed by spica cast immobilization is the generally accepted next step. Open reduction with capsulorrhaphy and possibly a pelvic osteotomy is usually reserved for cases where closed reduction fails or for older children with more severe dysplasia. A second trial of Pavlik harness or an abduction orthosis is unlikely to be successful at this age and stage. Observation would risk further progression of the dysplasia.

Question 4288

Topic: 4. Pediatrics

A 3-month-old infant presents with a severe, rigid congenital clubfoot that has failed initial Ponseti casting attempts (residual cavus and adductus after 6 weeks). The foot remains severely deformed and non-reducible. What is the most appropriate next step in management?

. Continue Ponseti casting for a longer duration, possibly with increased force
. Switch to a dynamic splint or brace for 3 months to stretch the tissues
. Perform a comprehensive posteromedial release surgery
. Refer for a trial of a custom-molded ankle-foot orthosis (AFO)
. Wait until the child is older (e.g., 1 year) before considering further intervention

Correct Answer & Explanation

. Perform a comprehensive posteromedial release surgery

Explanation

The Ponseti method is highly successful for congenital clubfoot, but in rare cases of severe, rigid, or atypical clubfoot, it may fail. When Ponseti casting fails and the foot remains severely deformed and rigid, a comprehensive posteromedial release (PMR) surgery is the most appropriate next step. Continuing casting with increased force is unlikely to be successful and may cause skin breakdown. Dynamic splints or AFOs are typically used after successful correction to maintain position, not to achieve correction in a failed Ponseti case. Waiting would lead to more severe deformity and stiffness, making future correction more difficult. PMR allows for direct release of tight structures and correction of bony deformities.

Question 4289

Topic: 4. Pediatrics

A neonate presents with short-limbed dwarfism, macrocephaly, and characteristic facial features. Genetic testing reveals a gain-of-function mutation in the Fibroblast Growth Factor Receptor 3 (FGFR3) gene. This mutation is most commonly associated with which of the following conditions?

. Osteogenesis Imperfecta Type I
. Achondroplasia
. Marfan Syndrome
. Hypophosphatasia
. Multiple Epiphyseal Dysplasia

Correct Answer & Explanation

. Achondroplasia

Explanation

Achondroplasia, the most common form of short-limbed dwarfism, is caused by a dominant gain-of-function mutation in the FGFR3 gene. FGFR3 normally negatively regulates chondrocyte proliferation and differentiation in the growth plate. A gain-of-function mutation leads to excessive signaling, resulting in premature closure of the growth plates and severely impaired endochondral ossification, particularly in long bones. Osteogenesis Imperfecta is a collagen disorder. Marfan Syndrome affects fibrillin-1. Hypophosphatasia involves alkaline phosphatase deficiency. Multiple Epiphyseal Dysplasia has various genetic causes, but not typically a direct FGFR3 gain-of-function mutation.

Question 4290

Topic: 4. Pediatrics

Achondroplasia, the most common form of dwarfism, is caused by a gain-of-function mutation in which receptor, leading to impaired endochondral ossification?

. Insulin-like growth factor 1 receptor (IGF1R)
. Bone morphogenetic protein receptor (BMPR)
. Fibroblast growth factor receptor 3 (FGFR3)
. Parathyroid hormone receptor 1 (PTHR1)
. Vitamin D receptor (VDR)

Correct Answer & Explanation

. Fibroblast growth factor receptor 3 (FGFR3)

Explanation

Achondroplasia is an autosomal dominant disorder caused by a gain-of-function mutation in the Fibroblast Growth Factor Receptor 3 (FGFR3) gene. FGFR3 typically acts to negatively regulate chondrocyte proliferation and differentiation in the growth plate. The activating mutation in achondroplasia leads to constitutive activation of FGFR3, resulting in excessive inhibition of chondrocyte proliferation and hypertrophy, thus severely impairing endochondral ossification and longitudinal bone growth. The other receptors listed play roles in bone metabolism but are not directly linked to the pathogenesis of achondroplasia.

Question 4291

Topic: 4. Pediatrics
Which molecular signaling pathway is commonly implicated in the pathogenesis of achondroplasia, leading to impaired endochondral ossification and dwarfism?
. Wnt/ฮฒ-catenin pathway hyperactivation
. BMP signaling pathway overactivity
. FGFR3 gain-of-function mutation
. TGF-ฮฒ pathway inhibition
. Hedgehog pathway hypofunction

Correct Answer & Explanation

. FGFR3 gain-of-function mutation

Explanation

Achondroplasia is caused by an autosomal dominant gain-of-function mutation in the Fibroblast Growth Factor Receptor 3 (FGFR3) gene. This mutation leads to constitutive activation of FGFR3, which normally acts as a negative regulator of chondrocyte proliferation and differentiation. The overactive FGFR3 signaling prematurely inhibits chondrocyte proliferation and hypertrophy in the growth plates, severely impairing endochondral ossification and resulting in short stature and other skeletal abnormalities. The other options describe dysregulation of different pathways or incorrect mechanisms.

Question 4292

Topic: 4. Pediatrics

A 10-year-old boy presents with a history of recurrent fractures, blue sclerae, and opalescent teeth. Genetic testing reveals a mutation in COL1A1. Which of the following best describes the fundamental defect in the collagen synthesis pathway for this patient?

. Substitution of glycine with a bulkier amino acid in the triple helix
. Defect in the hydroxylation of proline residues
. Failure of cleavage of the C-propeptide
. Mutation in the IFITM5 gene
. Defective cross-linking by lysyl oxidase

Correct Answer & Explanation

. Substitution of glycine with a bulkier amino acid in the triple helix

Explanation

Osteogenesis Imperfecta (OI) types I-IV are typically caused by autosomal dominant mutations in the COL1A1 or COL1A2 genes. The most common severe mutation is a single base substitution leading to the replacement of a crucial glycine residue with a bulkier amino acid (like arginine or valine). This disrupts the tight coiling of the collagen triple helix, leading to qualitative or quantitative defects in type I collagen. Type V OI is associated with the IFITM5 gene.

Question 4293

Topic: 4. Pediatrics

A 12-year-old male with Osteogenesis Imperfecta develops a painful, rapidly enlarging mass over his right femur following a minor trauma. Radiographs show a massive, dense ossification surrounding the femoral shaft. Genetic testing would most likely reveal a mutation in which of the following genes?

. COL1A1
. COL1A2
. CRTAP
. IFITM5
. LEPRE1

Correct Answer & Explanation

. IFITM5

Explanation

The clinical presentation is highly suggestive of hypertrophic callus formation, a hallmark of Osteogenesis Imperfecta (OI) Type V. OI Type V is inherited in an autosomal dominant manner and is caused by a specific heterozygous mutation in the IFITM5 gene, which encodes BRIL (bone-restricted IFITM-like protein). It is not caused by defects in type 1 collagen genes (COL1A1/COL1A2). Other typical findings in Type V include calcification of the interosseous membrane of the forearm and radial head dislocation.

Question 4294

Topic: 4. Pediatrics
A 3-year-old girl with severe osteogenesis imperfecta (Sillence Type III) presents with marked anterolateral bowing of both femurs, interfering with her ability to stand in braces. Which of the following is the most appropriate surgical management for her deformities?
. Closed osteoclasis and spica casting
. Multiple-level osteotomies and fixation with a single-piece rigid intramedullary nail
. Multiple-level osteotomies and fixation with a telescoping intramedullary rod
. Application of a circular external fixator for gradual correction
. Submuscular plating of the femur

Correct Answer & Explanation

. Multiple-level osteotomies and fixation with a telescoping intramedullary rod

Explanation

In growing children with severe OI and significant long bone deformities, the gold standard surgical treatment is multiple-level osteotomies (often referred to as 'shish kebab' osteotomies) stabilized with a telescoping intramedullary rod (e.g., Fassier-Duval rod). Telescoping rods accommodate bone growth, prolonging the time until revision surgery is needed. Rigid nails are quickly outgrown, leading to recurrent deformity ('migration' or 'spinnaker' effect) and fractures at the end of the nail.

Question 4295

Topic: 4. Pediatrics
A 4-year-old boy is recently diagnosed with SMA. His parents state he can sit independently if placed in position, but he has never been able to stand or walk. Based on this clinical milestone, which type of SMA does he have, and what is the expected lifespan?
. SMA Type I; death usually by age 2 without treatment
. SMA Type II; survival into adulthood is common with aggressive supportive care
. SMA Type III; normal lifespan expected
. SMA Type I; normal lifespan expected
. SMA Type IV; normal lifespan expected

Correct Answer & Explanation

. SMA Type II; survival into adulthood is common with aggressive supportive care

Explanation

SMA Type II (intermediate form) is characterized by the ability to sit independently but an inability to walk independently. Onset is usually between 6 and 18 months. With aggressive respiratory and nutritional support, many patients survive well into adulthood, although respiratory failure is the most common cause of morbidity and mortality. SMA Type I (Werdnig-Hoffmann) infants never achieve independent sitting and typically die before age 2 without treatment.

Question 4296

Topic: 4. Pediatrics

A 10-year-old girl with OI Type IV undergoes bilateral femoral osteotomies and telescoping intramedullary rod insertion. Two years later, radiographs show that the male (distal) portion of the rod has migrated proximally out of the distal epiphysis. Which complication of telescoping rods does this represent?

. Spinnaker effect
. T-piece pullout
. Failure of expansion
. Sub-trochanteric fracture
. Varus collapse

Correct Answer & Explanation

. Failure of expansion

Explanation

Failure of expansion (or failure to telescope) is a common complication of telescoping intramedullary rods (such as the Fassier-Duval rod). This occurs when the male and female components fail to slide apart as the bone grows. Consequently, the fixation at the distal epiphysis pulls out, leading to proximal migration of the distal component, loss of fixation, and recurrent deformity.

Question 4297

Topic: 4. Pediatrics
A patient with osteogenesis imperfecta presents with severe dentinogenesis imperfecta (DI). DI is most frequently associated with which mutation and which classification of OI?
. COL1A1 haploinsufficiency; Type I
. CRTAP mutation; Type VIII
. IFITM5 mutation; Type V
. COL1A2 structural mutation; Type III and IV
. LEPRE1 mutation; Type VIII

Correct Answer & Explanation

. COL1A2 structural mutation; Type III and IV

Explanation

Dentinogenesis imperfecta (DI) is most commonly and severely seen in OI Types III and IV, which are typically caused by structural mutations (qualitative defects) in collagen, predominantly in COL1A2 (though COL1A1 structural mutations also cause it). OI Type I, typically caused by haploinsufficiency (quantitative defect, usually COL1A1 null alleles), has a much lower incidence of DI.

Question 4298

Topic: 4. Pediatrics
A 1-year-old infant is suspected of having a lethal form of osteogenesis imperfecta. They have multiple in utero fractures, 'crumpled' long bones, and an extremely soft skull. According to the Sillence classification, which type of OI does this infant have?
. Type I
. Type II
. Type III
. Type IV
. Type V

Correct Answer & Explanation

. Type II

Explanation

According to the Sillence classification: Type I is mild (blue sclera, normal height, minimal deformity). Type II is perinatal lethal (multiple in utero fractures, crumpled long bones, severe pulmonary hypoplasia). Type III is severe and progressively deforming. Type IV is moderate. Type V is characterized by hypertrophic callus and calcification of the interosseous membrane.

Question 4299

Topic: 4. Pediatrics

A non-ambulatory 8-year-old child with SMA Type II presents with unilateral hip subluxation noted on a routine surveillance radiograph. The patient is completely pain-free, tolerates sitting well, and has a symmetrical, level pelvis. What is the most appropriate management for this hip subluxation?

. Varus derotational osteotomy (VDRO) with Dega pelvic osteotomy
. Open reduction and spica casting
. Observation and continuation of current physical therapy
. Proximal femoral resection (Girdlestone procedure)
. Adductor tenotomy and psoas release alone

Correct Answer & Explanation

. Observation and continuation of current physical therapy

Explanation

Hip subluxation and dislocation are extremely common in non-ambulatory patients with SMA Type II. In contrast to cerebral palsy, the dislocated hips in SMA are almost universally painless and do not typically interfere with sitting or hygiene. Surgical reconstruction in this population has a high recurrence rate, significant complication risk, and does not improve function. Therefore, painless hip dislocation in a non-ambulatory SMA patient is best managed with observation.

Question 4300

Topic: 4. Pediatrics
A 7-year-old with OI Type III underwent placement of Fassier-Duval telescoping rods in both femurs 2 years ago. He now presents with anterior thigh pain. Radiographs reveal proximal migration of the female rod component out of the bone and into the gluteal soft tissues. What is the most common technical error leading to this specific complication?
. Failure to engage the male component securely in the distal epiphysis
. Failure to thread the female component adequately into the proximal apophysis/epiphysis
. Excessive longitudinal growth of the femur outstripping the rod's capacity
. Rod fracture secondary to an unhealed diaphyseal osteotomy
. Delayed postoperative administration of bisphosphonates

Correct Answer & Explanation

. Failure to thread the female component adequately into the proximal apophysis/epiphysis

Explanation

The Fassier-Duval rod is an intramedullary telescoping system designed to elongate with the child's bone growth. The female component must be securely threaded into the proximal bone (e.g., the greater trochanteric apophysis or proximal epiphysis), while the male component anchors in the distal epiphysis. Proximal migration of the female component typically occurs when it is not adequately threaded or loses purchase in the proximal anchoring site.

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