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4. Pediatrics MCQs

Practice Set 21 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 401

Topic: Pediatric Lower Extremity

During the Ponseti casting technique for idiopathic clubfoot, what is the final deformity corrected before considering an Achilles tenotomy?

. Cavus
. Adductus
. Varus
. Equinus
. Forefoot pronation

Correct Answer & Explanation

. Equinus

Explanation

The Ponseti method corrects deformities in the order of CAVE: Cavus, Adductus, Varus, and finally Equinus. An Achilles tenotomy is frequently required to correct the residual equinus.

Question 402

Topic: Pediatric Hip

A 4-month-old female is treated with a Pavlik harness for developmental dysplasia of the hip (DDH). At her follow-up appointment, the parents report she is not kicking her right leg as much as the left. Which of the following nerve palsies is the most common complication of excessive hip flexion in a Pavlik harness?

. Sciatic nerve
. Obturator nerve
. Femoral nerve
. Superior gluteal nerve
. Pudendal nerve

Correct Answer & Explanation

. Femoral nerve

Explanation

Femoral nerve palsy is the most common nerve injury associated with the Pavlik harness, typically caused by excessive hip flexion. Excessive abduction, conversely, increases the risk of avascular necrosis of the femoral head.

Question 403

Topic: 4. Pediatrics

A pediatric orthopedic surgeon is utilizing the Ponseti method to correct an infant's idiopathic clubfoot. What is the correct sequential order of deformity correction in this technique?

. Equinus, Varus, Adductus, Cavus
. Cavus, Adductus, Varus, Equinus
. Adductus, Varus, Cavus, Equinus
. Cavus, Varus, Equinus, Adductus
. Varus, Cavus, Adductus, Equinus

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus

Explanation

The Ponseti method corrects clubfoot deformities in a specific sequence represented by the mnemonic CAVE: Cavus, Adductus, Varus, and finally Equinus. The cavus is corrected first by elevating the first ray.

Question 404

Topic: Pediatric Hip

A 13-year-old obese male presents with left knee pain and a limp. Examination reveals obligate external rotation of the hip with passive flexion. Radiographs confirm a slipped capital femoral epiphysis (SCFE). Which of the following best describes the anatomical displacement of the femoral neck relative to the epiphysis?

. Anterior and Superior
. Anterior and Inferior
. Posterior and Superior
. Posterior and Inferior
. Medial and Inferior

Correct Answer & Explanation

. Posterior and Inferior

Explanation

In SCFE, the epiphysis remains seated within the acetabulum while the femoral neck displaces anteriorly and superiorly. Radiographically, the epiphysis appears to have slipped posteriorly and inferiorly.

Question 405

Topic: Pediatric Hip
During the progression of Legg-Calvé-Perthes disease, which radiographic sign represents a subchondral fracture and typically heralds the onset of the fragmentation stage?
. Gage sign
. Crescent sign
. Sagging rope sign
. Trethowan sign
. Waldenström sign

Correct Answer & Explanation

. Crescent sign

Explanation

The crescent sign represents a subchondral fracture of the femoral head. It usually indicates the transition from the initial avascular necrosis phase to the fragmentation stage in Legg-Calvé-Perthes disease.

Question 406

Topic: 4. Pediatrics

A 2-year-old girl is evaluated for multiple low-energy fractures. Clinical examination reveals blue sclerae and opalescent, abnormally wearing teeth (dentinogenesis imperfecta). A mutation in which of the following genes is most likely responsible for her condition?

. FGFR3
. COL1A1
. COL2A1
. COMP
. RUNX2

Correct Answer & Explanation

. COL1A1

Explanation

Osteogenesis imperfecta is primarily caused by autosomal dominant mutations in the COL1A1 or COL1A2 genes, which encode for type I collagen. This leads to bone fragility, blue sclerae, and dentinogenesis imperfecta.

Question 407

Topic: 4. Pediatrics
A 3-year-old boy presents with progressive bowing of his left leg. Radiographs reveal a depressed medial tibial metaphysis with a beaked appearance, consistent with Langenskiöld stage III infantile Blount's disease. What is the most appropriate surgical treatment?
. Guided growth with a medial tension band plate
. Proximal tibial valgus osteotomy
. Lateral hemiepiphysiodesis
. Medial plateau elevation osteotomy
. Observation with serial bracing

Correct Answer & Explanation

. Proximal tibial valgus osteotomy

Explanation

For a child aged 3 or older with Langenskiöld stage III or higher infantile Blount's disease, proximal tibial valgus osteotomy is the standard of care to correct the severe mechanical axis deviation and relieve pressure on the medial physis.

Question 408

Topic: 4. Pediatrics

A 13-year-old boy sustains a twisting injury to his ankle. CT scan reveals a classic triplane fracture. In which planes do the fracture lines of a classic triplane fracture occur?

. Coronal in the metaphysis, transverse in the physis, sagittal in the epiphysis
. Sagittal in the metaphysis, coronal in the physis, transverse in the epiphysis
. Transverse in the metaphysis, sagittal in the physis, coronal in the epiphysis
. Coronal in the metaphysis, sagittal in the physis, transverse in the epiphysis
. Sagittal in the metaphysis, transverse in the physis, coronal in the epiphysis

Correct Answer & Explanation

. Coronal in the metaphysis, transverse in the physis, sagittal in the epiphysis

Explanation

A triplane fracture typically occurs in adolescents during asymmetric physeal closure. The fracture lines propagate in the coronal plane through the metaphysis, transverse plane through the physis, and sagittal plane through the epiphysis.

Question 409

Topic: 4. Pediatrics
A 14-year-old girl presents with an isolated juvenile Tillaux fracture of the distal tibia. Which of the following describes the mechanism of injury and the deforming anatomical structure?
. Plantarflexion causing avulsion by the posterior talofibular ligament
. External rotation causing avulsion by the anterior inferior tibiofibular ligament
. Axial loading causing impaction of the talar dome
. Inversion causing avulsion by the calcaneofibular ligament
. Hyperdorsiflexion causing anterior distal tibial impaction

Correct Answer & Explanation

. External rotation causing avulsion by the anterior inferior tibiofibular ligament

Explanation

A juvenile Tillaux fracture is a Salter-Harris III fracture of the anterolateral distal tibial epiphysis. It is caused by an external rotation force where the anterior inferior tibiofibular ligament (AITFL) avulses the bony fragment.

Question 410

Topic: 4. Pediatrics

A 7-year-old child with spastic quadriplegic cerebral palsy presents for routine hip surveillance. AP pelvis radiographs reveal a migration percentage of 45% in the right hip. Which of the following is the most appropriate management?

. Botulinum toxin injection to the adductors
. Observation and repeat radiographs in 1 year
. Adductor tenotomy alone
. Varus derotational osteotomy (VDRO) with or without pelvic osteotomy
. Total hip arthroplasty

Correct Answer & Explanation

. Varus derotational osteotomy (VDRO) with or without pelvic osteotomy

Explanation

In children with cerebral palsy, a hip migration percentage >40% typically indicates a progressive subluxation that will not resolve with soft tissue releases alone. Bony reconstruction with a VDRO, often combined with a pelvic osteotomy, is required.

Question 411

Topic: 4. Pediatrics

A 2-year-old child presents with a history of recurrent fractures following minimal trauma, blue sclerae, and early hearing loss. This presentation is primarily due to a genetic defect in the synthesis of which of the following?

. Type I collagen
. Type II collagen
. Fibroblast growth factor receptor 3 (FGFR3)
. Cartilage oligomeric matrix protein (COMP)
. Core binding factor alpha 1 (CBFA1)

Correct Answer & Explanation

. Type I collagen

Explanation

Osteogenesis imperfecta is characterized by bone fragility, blue sclerae, and dentinogenesis imperfecta. It is caused by mutations in the COL1A1 or COL1A2 genes, which lead to qualitative or quantitative defects in Type I collagen.

Question 412

Topic: 4. Pediatrics

A 6-year-old boy sustains a completely displaced extension-type supracondylar fracture of the humerus. During the neurological exam, he is unable to flex the interphalangeal joint of his thumb or the distal interphalangeal joint of his index finger. Which nerve has most likely been injured?

. Radial nerve
. Ulnar nerve
. Anterior interosseous nerve
. Posterior interosseous nerve
. Musculocutaneous nerve

Correct Answer & Explanation

. Anterior interosseous nerve

Explanation

The anterior interosseous nerve (AIN), a branch of the median nerve, is the most commonly injured nerve in extension-type pediatric supracondylar humerus fractures. Injury to the AIN results in the inability to flex the IP joint of the thumb and the DIP joint of the index finger (the "A-OK" sign).

Question 413

Topic: Pediatric Hip
In a child diagnosed with Legg-Calvé-Perthes disease, which of the following factors has been shown to be the most significant prognostic indicator for the long-term anatomic outcome of the hip?
. Gender of the patient
. Age of the patient at the onset of symptoms
. Body mass index
. Family history of hip dysplasia
. Duration of the initial limp

Correct Answer & Explanation

. Age of the patient at the onset of symptoms

Explanation

Age at the onset of Legg-Calvé-Perthes disease is the most critical prognostic factor. Children who develop the disease before 6 to 8 years of age have a significantly better prognosis due to the greater remaining growth potential for femoral head remodeling.

Question 414

Topic: Pediatric Hip

A 13-year-old obese boy presents with acute knee pain and inability to bear weight. Radiographs show a severe acute-on-chronic slipped capital femoral epiphysis (SCFE). Which of the following is the most devastating potential complication of forceful anatomic reduction of the slip prior to fixation?

. Chondrolysis
. Avascular necrosis (AVN) of the femoral head
. Premature closure of the triradiate cartilage
. Cam-type femoroacetabular impingement
. Slipped capital femoral epiphysis of the contralateral hip

Correct Answer & Explanation

. Avascular necrosis (AVN) of the femoral head

Explanation

Forceful reduction of a displaced SCFE significantly stretches or tears the delicate epiphyseal blood supply (retinacular vessels), dramatically increasing the risk of avascular necrosis (AVN). In situ pinning is generally preferred to minimize this risk.

Question 415

Topic: 4. Pediatrics
A 14-year-old boy presents with an ankle injury. Radiographs reveal a Salter-Harris III fracture of the anterolateral aspect of the distal tibial epiphysis (Tillaux fracture). What is the primary anatomical basis for this specific injury pattern in adolescents?
. Avulsion by the strong deltoid ligament
. Asymmetrical closure of the distal tibial physis from medial to lateral
. Asymmetrical closure of the distal tibial physis from lateral to medial
. The interosseous membrane acts as a fulcrum during pronation
. Avulsion by the posterior talofibular ligament

Correct Answer & Explanation

. Asymmetrical closure of the distal tibial physis from medial to lateral

Explanation

The distal tibial physis closes asymmetrically, starting centrally, then moving medially, and finally laterally. In adolescence, the lateral portion remains open and vulnerable to avulsion by the anterior inferior tibiofibular ligament (AITFL), causing a Tillaux fracture.

Question 416

Topic: 4. Pediatrics

A 2-year-old boy is diagnosed with congenital pseudarthrosis of the tibia (CPT). This condition is most strongly associated with which of the following systemic disorders?

. Ehlers-Danlos syndrome
. Osteogenesis imperfecta
. Neurofibromatosis type 1
. Marfan syndrome
. Cleidocranial dysplasia

Correct Answer & Explanation

. Neurofibromatosis type 1

Explanation

Congenital pseudarthrosis of the tibia is highly associated with Neurofibromatosis type 1 (NF-1). Approximately 50% of patients with CPT have NF-1, characterized by anterolateral bowing of the tibia that progresses to pseudarthrosis.

Question 417

Topic: Pediatric Hip
A 13-year-old boy who underwent in situ fixation of slipped capital femoral epiphysis 1 year ago calls your office to complain of knee pain on the other side. He is able to bear his weight on the leg. You recommend:
. No sports for 1 month and an office visit if the symptoms continue
. An office visit within the next 2 weeks for evaluation
. Crutches and an office visit within 24 hours
. Magnetic resonance image of the knee and an office visit if the results are abnormal
. Arthroscopy of the knee

Correct Answer & Explanation

. Crutches and an office visit within 24 hours

Explanation

This patient most likely has a contralateral slipped capital femoral epiphysis. It may even be in the "preslip" category. Acute progression to an unstable slip is possible at any time and may lead to avascular necrosis and permanent loss of motion. Therefore, urgent examination with physical examination and plain radiographs is necessary.

Question 418

Topic: 4. Pediatrics

Which population of patients with cerebral palsy is at greatest risk of neuromuscular hip subluxation:

. Monoplegics
. Spastic hemiplegics
. Spastic diplegics
. Total-involvement
. Athetoid

Correct Answer & Explanation

. Total-involvement

Explanation

Patients with total-involvement cerebral palsy are at the greatest risk of hip subluxation. The rate is documented to be between 25% and 60%.

Question 419

Topic: 4. Pediatrics

Which group of children with cerebral palsy are at greatest risk of hip subluxation after selective dorsal rhizotomy:

. Under age 4
. Over age 10
. Spastic diplegics
. Nonambulators
. Spastic hemiplegics

Correct Answer & Explanation

. Nonambulators

Explanation

Nonambulators with some degree of pre-existing hip migration are at highest risk of hip subluxation after selective dorsal rhizotomy. Patients over the age of 10 and those with hemiplegia are not typically offered selective rhizotomy.

Question 420

Topic: 4. Pediatrics

Which of the following muscles is most often preserved during adductor tenotomy for patients with cerebral palsy:

. Adductor longus
. Adductor brevis
. Gracilis
. Adductor magnus
. Pectineus

Correct Answer & Explanation

. Adductor magnus

Explanation

Adductor tenotomy performed on patients with cerebral palsy typically involves multiple releases until abduction of more than 60° is obtained. This usually begins with release of the longus, brevis, and gracilis (with the pectineus if necessary). The adductor magnus is almost never released because of its important extensor function.

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