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4. Pediatrics MCQs

Practice Set 295 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 5881

Topic: Pediatric Hip

A 13-year-old boy undergoes in situ pinning of a stable, moderate left SCFE. One year later, he presents with progressive stiffness and pain in the left hip. Examination reveals severe global restriction of hip motion. Radiographs show joint space narrowing and subchondral sclerosis without focal collapse. What is the most likely diagnosis?

. Avascular necrosis (AVN)
. Chondrolysis
. Septic arthritis
. Osteoarthritis
. Hardware failure

Correct Answer & Explanation

. Chondrolysis

Explanation

Chondrolysis is a severe complication of SCFE, presenting with global loss of motion and joint space narrowing. It is commonly associated with unrecognized pin penetration into the joint but can also occur idiopathically in severe slips.

Question 5882

Topic: 4. Pediatrics

A 4-week-old female infant has a positive Ortolani test on the right hip. An ultrasound is performed. What alpha angle measurement is considered the threshold for a normal hip (Graf Type I)?

. > 40 degrees
. > 50 degrees
. > 60 degrees
. < 50 degrees
. < 60 degrees

Correct Answer & Explanation

. > 60 degrees

Explanation

According to Graf's ultrasound classification for DDH, an alpha angle greater than 60 degrees indicates a normal, well-developed bony acetabular roof (Type I hip). Angles less than 60 degrees indicate varying degrees of dysplasia.

Question 5883

Topic: 4. Pediatrics

A 5-year-old boy presents with progressive, asymmetric hypertrophy of his right lower extremity, cutaneous capillary malformations (port-wine stains), and varicose veins. Which condition is the most likely diagnosis?

. Proteus syndrome
. Neurofibromatosis type 1
. Klippel-Trenaunay syndrome
. Russell-Silver syndrome
. Beckwith-Wiedemann syndrome

Correct Answer & Explanation

. Klippel-Trenaunay syndrome

Explanation

Klippel-Trenaunay syndrome is a rare congenital vascular disorder characterized by the triad of capillary malformations (port-wine stains), venous varicosities, and bony and soft tissue hypertrophy, typically involving one extremity.

Question 5884

Topic: Pediatric Hip

A 28-year-old hockey player presents with groin pain worsened by deep hip flexion and internal rotation. Radiographs display an alpha angle of 65 degrees. What is the primary pathomechanism of cartilage damage in this specific condition?

. Linear contact between the acetabular rim and femoral neck causing labral infolding
. Pincer impingement leading to contrecoup cartilage lesions posteromedially
. Shear forces at the chondrolabral junction leading to articular cartilage delamination
. Global joint incongruity mimicking developmental dysplasia
. Chondral necrosis secondary to retinacular vascular compression

Correct Answer & Explanation

. Shear forces at the chondrolabral junction leading to articular cartilage delamination

Explanation

Cam impingement (high alpha angle) involves a non-spherical femoral head entering the acetabulum, creating shear forces at the chondrolabral junction. This leads to inside-out delamination of the acetabular cartilage.

Question 5885

Topic: Pediatric Hip
In the evaluation of a 7-year-old boy with Legg-Calvé-Perthes disease, the Herring lateral pillar classification dictates prognosis and treatment. Which of the following radiographic findings correctly defines a Herring Group C classification?
. No loss of height in the lateral pillar
. Less than 50% loss of lateral pillar height
. Greater than 50% loss of lateral pillar height
. A visible subchondral crescent sign extending into the entire lateral pillar
. Medial joint space widening greater than 5 millimeters

Correct Answer & Explanation

. Greater than 50% loss of lateral pillar height

Explanation

The Herring classification assesses the height of the lateral pillar on AP radiographs during the fragmentation phase. Group C is defined by >50% loss of height, portending a poorer prognosis and a higher likelihood of non-spherical healing.

Question 5886

Topic: Pediatric Hip

A 13-year-old obese male sustains an acute-on-chronic slipped capital femoral epiphysis (SCFE) and is unable to bear weight even with crutches. He is treated with single in situ screw fixation. What is the most devastating, yet relatively common, complication specifically associated with this variant of SCFE?

. Chondrolysis
. Avascular necrosis (AVN) of the femoral head
. Progressive slip post-fixation
. Intra-articular pin penetration
. Subtrochanteric femur fracture

Correct Answer & Explanation

. Avascular necrosis (AVN) of the femoral head

Explanation

By the Loder classification, the inability to bear weight defines an unstable SCFE. Unstable slips carry a high risk of avascular necrosis (up to 47%), resulting from kinking or disruption of the vulnerable retinacular vessels.

Question 5887

Topic: Pediatric Hip

A 35-year-old female with secondary osteoarthritis due to severe developmental dysplasia of the hip (Crowe Type IV) requires a total hip arthroplasty. To successfully place the acetabular cup in the true acetabulum and safely reduce the hip, which adjunctive procedure is most frequently required?

. Greater trochanteric advancement
. Proximal femoral valgus osteotomy
. Subtrochanteric shortening osteotomy
. Distal femoral extension osteotomy
. Ischial tuberosity osteotomy

Correct Answer & Explanation

. Subtrochanteric shortening osteotomy

Explanation

Crowe Type IV DDH involves a high, completely dislocated hip. Bringing the femoral head down to the true acetabulum heavily stretches the sciatic nerve, routinely requiring a subtrochanteric shortening osteotomy to prevent nerve palsy.

Question 5888

Topic: Pediatric Hip

A 5-year-old girl with developmental dysplasia of the hip (DDH) requires a pelvic osteotomy. The surgeon plans an incomplete osteotomy through the ilium, hinging on the triradiate cartilage, to reduce the acetabular volume and improve anterior and lateral coverage. Which osteotomy is described?

. Salter osteotomy
. Pemberton osteotomy
. Chiari osteotomy
. Steel osteotomy
. Ganz osteotomy

Correct Answer & Explanation

. Pemberton osteotomy

Explanation

The Pemberton osteotomy is an incomplete pericapsular osteotomy that hinges on the triradiate cartilage. It actively alters the shape of the acetabulum and reduces its volume, making it highly effective for true acetabular dysplasia.

Question 5889

Topic: 4. Pediatrics
A 4-year-old child presents with severe infantile Blount disease. Radiographs show a Langenskiöld stage IV lesion with a prominent medial metaphyseal beak and a step-off in the epiphysis. What is the most appropriate surgical management?
. Bracing with knee-ankle-foot orthosis
. Proximal tibial valgus osteotomy only
. Proximal tibial osteotomy with lateral epiphysiodesis
. Physeal bar excision with corrective osteotomy
. Medial hemi-epiphysiodesis

Correct Answer & Explanation

. Physeal bar excision with corrective osteotomy

Explanation

Langenskiöld stage IV infantile Blount disease involves the formation of a medial physeal bar. Management requires excision of the bony bridge (bar) with fat interposition and a concurrent valgus-producing proximal tibial osteotomy.

Question 5890

Topic: Pediatric Hip

A 12-year-old obese male presents with a unilateral stable slipped capital femoral epiphysis (SCFE). Which of the following is the strongest clinical indication for prophylactic in situ pinning of the contralateral asymptomatic hip?

. Male sex
. Body mass index greater than the 95th percentile
. Age greater than 14 years
. Initial slip angle greater than 50 degrees
. Presentation with a concomitant endocrine disorder

Correct Answer & Explanation

. Presentation with a concomitant endocrine disorder

Explanation

Endocrine or metabolic disorders (e.g., hypothyroidism, renal osteodystrophy) carry a very high risk of bilateral involvement in SCFE. This makes underlying endocrinopathy a strong, widely accepted indication for prophylactic pinning of the contralateral hip.

Question 5891

Topic: Pediatric Hip

A 5-year-old boy is evaluated for a painless waddling gait. Radiographs show developmental coxa vara. The Hilgenreiner's epiphyseal angle (HEA) is measured at 65 degrees. What is the most appropriate management?

. Observation and annual radiographs
. Hip spica casting
. Proximal femoral valgus osteotomy
. Greater trochanteric epiphysiodesis
. Pelvic support osteotomy

Correct Answer & Explanation

. Proximal femoral valgus osteotomy

Explanation

An HEA greater than 60 degrees in developmental coxa vara generally indicates a progressive deformity that will not resolve spontaneously. A proximal femoral valgus osteotomy is required to correct the neck-shaft angle and mechanical axis.

Question 5892

Topic: Pediatric Hip
A 45-year-old male presents with early-onset hip osteoarthritis. He has a history of Legg-Calvé-Perthes disease as a child. Radiographs show an enlarged, flat femoral head that is congruent with a similarly flattened acetabulum. This presentation most closely correlates with which Stulberg classification from childhood?
. Stulberg I
. Stulberg II
. Stulberg III
. Stulberg IV
. Stulberg V

Correct Answer & Explanation

. Stulberg III

Explanation

Stulberg III describes an aspherical but congruent joint (coxa magna), which leads to mild-to-moderate osteoarthritis in middle age. Stulberg IV and V are aspherical and incongruent, typically leading to severe, early arthritis before age 40.

Question 5893

Topic: Pediatric Lower Extremity

A 2-year-old child with Proximal Focal Femoral Deficiency (PFFD) has a severely short femur, but a normal, stable knee and ankle. The foot is at the level of the contralateral knee. To optimize the child for a functional prosthesis, the surgeon considers a Van Nes rotationplasty. What critical prerequisite must be met for this procedure to be successful?

. Normal hip joint articulation
. Bilateral PFFD
. Ankle plantarflexion and dorsiflexion of at least 20 degrees
. Intact anterior cruciate ligament
. A functioning ankle joint capable of acting as a knee joint

Correct Answer & Explanation

. A functioning ankle joint capable of acting as a knee joint

Explanation

For a successful Van Nes rotationplasty, the ankle must be fully functional and have near-normal range of motion. Following the 180-degree rotation, the ankle joint will function as the new knee joint to power the prosthesis.

Question 5894

Topic: Pediatric Hip

A 6-month-old girl undergoes closed reduction and spica casting for developmental dysplasia of the hip. Which of the following positions during casting is most heavily associated with the development of iatrogenic avascular necrosis (AVN) of the femoral head?

. Hip flexion of 90 degrees and abduction of 45 degrees
. Hip flexion of 100 degrees and adduction of 10 degrees
. Extreme hip abduction greater than 60 degrees with internal rotation
. Hip extension and external rotation
. Hip flexion of 60 degrees and neutral abduction

Correct Answer & Explanation

. Extreme hip abduction greater than 60 degrees with internal rotation

Explanation

Immobilization in extreme hip abduction (the 'frog-leg' position) increases pressure on the delicate retinacular vessels. This dramatically increases the risk of iatrogenic avascular necrosis of the femoral head in DDH treatment.

Question 5895

Topic: 4. Pediatrics

Achondroplasia is the most common form of short-limbed dwarfism. The underlying genetic defect is a gain-of-function mutation in the FGFR3 gene. Which zone of the physis is primarily affected by this mutation?

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

Correct Answer & Explanation

. Proliferative zone

Explanation

Achondroplasia is caused by an activating mutation in FGFR3, which inhibits chondrocyte proliferation. This directly affects the proliferative zone of the physis, leading to impaired endochondral ossification.

Question 5896

Topic: 4. Pediatrics

A 30-year-old female presents with multiple cartilaginous lesions in the phalanges and multiple soft tissue hemangiomas. Which of the following gene mutations is most strongly associated with this syndrome?

. EXT1
. FGFR3
. IDH1/IDH2
. GNAS
. COL1A1

Correct Answer & Explanation

. IDH1/IDH2

Explanation

This presentation describes Maffucci syndrome, characterized by multiple enchondromas and soft tissue hemangiomas. Both Ollier disease and Maffucci syndrome are strongly linked to somatic mosaic mutations in the IDH1 or IDH2 genes.

Question 5897

Topic: 4. Pediatrics

A newborn is diagnosed with a skeletal dysplasia characterized by rhizomelic shortening, frontal bossing, and midface hypoplasia. Radiographs show narrowing of the interpedicular distances in the lumbar spine. What is the inheritance pattern and associated gene mutation?

. Autosomal recessive, FGFR3
. Autosomal dominant, FGFR3
. X-linked recessive, DMD
. Autosomal dominant, EXT1
. Autosomal recessive, DTDST

Correct Answer & Explanation

. Autosomal dominant, FGFR3

Explanation

Achondroplasia is the most common form of short-limb dwarfism, inherited in an autosomal dominant pattern. It is caused by an activating mutation in the FGFR3 gene, with approximately 80% of cases representing new spontaneous mutations.

Question 5898

Topic: 4. Pediatrics

An infant presents with short limbs and frontal bossing. Radiographs show narrowing of interpedicular distances from L1 to L5.

What is the primary cellular mechanism affected by the genetic mutation in this condition?

. Defective type 1 collagen synthesis
. Decreased proliferation of chondrocytes in the physeal proliferative zone
. Defective heparan sulfate synthesis
. Impaired osteoclast ruffled border formation
. Mutation in COMP gene causing misfolded proteins

Correct Answer & Explanation

. Decreased proliferation of chondrocytes in the physeal proliferative zone

Explanation

Achondroplasia is caused by a gain-of-function mutation in FGFR3. This results in the suppression of chondrocyte proliferation within the proliferative zone of the physis, leading to rhizomelic dwarfism.

Question 5899

Topic: 4. Pediatrics

A 4-year-old boy presents with short trunk dwarfism, prominent joints, myopia, and coxa vara. Cervical spine radiographs demonstrate odontoid hypoplasia. What is the genetic basis of this disorder?

. Mutation in the COMP gene
. Mutation in the FGFR3 gene
. Defect in type I collagen
. Mutation in the COL2A1 gene
. Defect in sulfate transport (DTDST gene)

Correct Answer & Explanation

. Mutation in the COL2A1 gene

Explanation

Spondyloepiphyseal dysplasia congenita (SEDc) is caused by a mutation in COL2A1 (Type II collagen). It is characterized by short-trunk dwarfism, atlantoaxial instability (odontoid hypoplasia), coxa vara, and myopia.

Question 5900

Topic: 4. Pediatrics

A newborn is diagnosed with achondroplasia. Which of the following accurately describes the molecular pathophysiology of this skeletal dysplasia?

. Loss-of-function mutation in the FGFR3 gene
. Gain-of-function mutation in the FGFR3 gene
. Defect in type I collagen synthesis
. Mutation in the COMP gene
. Defect in the diastrophic dysplasia sulfate transporter

Correct Answer & Explanation

. Gain-of-function mutation in the FGFR3 gene

Explanation

Achondroplasia is caused by a gain-of-function mutation in the Fibroblast Growth Factor Receptor 3 (FGFR3) gene. This mutation constitutively activates the receptor, leading to the abnormal inhibition of chondrocyte proliferation in the proliferative zone of the physis.

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