Menu

4. Pediatrics MCQs

Practice Set 221 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 4401

Topic: Pediatric Hip

A 13-year-old obese male presents with a 2-day history of severe right thigh pain and inability to bear weight after a minor trip. Examination shows obligatory external rotation of the right hip with flexion.

According to the Loder classification, which of the following criteria defines an 'unstable' slipped capital femoral epiphysis (SCFE)?

. Slip angle greater than 50 degrees
. Inability to ambulate with or without crutches
. Presence of a significant joint effusion on ultrasound
. Duration of symptoms less than 3 weeks
. Development of early chondrolysis

Correct Answer & Explanation

. Inability to ambulate with or without crutches

Explanation

The Loder classification divides SCFE into stable and unstable based on the patient's ability to bear weight. An unstable SCFE is defined by the inability to ambulate even with crutches, regardless of the duration of symptoms. This classification is clinically highly relevant because unstable SCFE has a significantly higher rate of avascular necrosis (AVN) approaching 50%.

Question 4402

Topic: Pediatric Hip

A 3-month-old female is being treated with a Pavlik harness for Developmental Dysplasia of the Hip (DDH). During a follow-up visit, it is noted that the anterior straps are adjusted too tightly, causing excessive hip flexion. This specific positioning error places the child at greatest risk for which of the following complications?

. Avascular necrosis of the femoral head
. Femoral nerve palsy
. Sciatic nerve palsy
. Obturator nerve palsy
. Inferior dislocation of the hip

Correct Answer & Explanation

. Femoral nerve palsy

Explanation

In the Pavlik harness, excessive hip flexion (typically > 120 degrees) can impinge the femoral nerve against the inguinal ligament, leading to a femoral nerve palsy (evident by loss of active knee extension/quadriceps function). Conversely, excessive abduction (posterior straps too tight) increases the risk of avascular necrosis (AVN) of the femoral head.

Question 4403

Topic: Pediatric Lower Extremity

The Ponseti method is the gold standard for the conservative management of idiopathic clubfoot, involving sequential manipulation and casting. Based on the Ponseti protocol, which of the following components of the clubfoot deformity is corrected LAST?

. Cavus
. Adductus
. Varus
. Equinus
. Forefoot supination

Correct Answer & Explanation

. Equinus

Explanation

The Ponseti method addresses clubfoot deformities in a specific sequence described by the acronym CAVE: Cavus (corrected first by elevating the first ray to supinate the forefoot), Adductus, Varus, and finally Equinus. Equinus is corrected last and in the vast majority of cases requires a percutaneous Achilles tenotomy to achieve adequate dorsiflexion.

Question 4404

Topic: 4. Pediatrics
A 12-year-old child presents with frequent fractures, blue sclerae, and hearing loss. This condition is primarily caused by a quantitative defect in which of the following structural components?
. Type I collagen
. Type II collagen
. Type III collagen
. Type IV collagen
. Type X collagen

Correct Answer & Explanation

. Type I collagen

Explanation

Osteogenesis imperfecta is most commonly caused by an autosomal dominant mutation affecting the COL1A1 or COL1A2 genes. This results in a quantitative or qualitative defect in Type I collagen, which is the major structural protein of bone.

Question 4405

Topic: Pediatric Hip

A 13-year-old obese male presents with left groin pain and an obligatory external rotation of the hip during active flexion. An AP pelvis radiograph is obtained.

What is the most appropriate management for a stable presentation of this condition?

. Spica casting
. In situ single screw fixation
. Closed reduction and multiple pinning
. Imhauser osteotomy
. Open reduction and internal fixation via surgical dislocation

Correct Answer & Explanation

. In situ single screw fixation

Explanation

The presentation is classic for a Slipped Capital Femoral Epiphysis (SCFE). The gold standard treatment for a stable SCFE is in situ fixation across the physis with a single cannulated screw.

Question 4406

Topic: Pediatric Upper Extremity & Spine
A 6-year-old boy falls from monkey bars and sustains a completely displaced, extension-type supracondylar humerus fracture (Gartland Type III). Radiographs show the distal fragment is displaced posteromedially. Which of the following peripheral nerves is at highest risk of injury with this specific displacement pattern?
. Median nerve
. Anterior interosseous nerve (AIN)
. Radial nerve
. Ulnar nerve
. Musculocutaneous nerve

Correct Answer & Explanation

. Radial nerve

Explanation

In a posteromedially displaced supracondylar fracture, the proximal fragment displaces anterolaterally, commonly piercing the brachialis muscle and tenting or injuring the radial nerve. Posterolateral displacement endangers the anterior interosseous nerve (AIN).

Question 4407

Topic: Pediatric Hip

A 12-year-old obese male presents with a 2-week history of left thigh pain and an antalgic limp. Examination reveals obligate external rotation with passive hip flexion. A radiograph is shown

. He is diagnosed with a Slipped Capital Femoral Epiphysis (SCFE). Which of the following is the strongest indication for prophylactic pinning of the contralateral asymptomatic hip?

. Male sex
. Modified Oxford bone age score of 20
. Initial presentation with acute slip
. Presence of an endocrine disorder (e.g., hypothyroidism)
. Body mass index in the 99th percentile

Correct Answer & Explanation

. Presence of an endocrine disorder (e.g., hypothyroidism)

Explanation

Prophylactic pinning of the contralateral hip in SCFE is highly recommended for patients with an underlying endocrine disorder (such as hypothyroidism, panhypopituitarism, or renal osteodystrophy), as they have a significantly higher risk of a subsequent bilateral slip. A low modified Oxford bone age score (<16), denoting skeletal immaturity, is also a relative indication, but a score of 20 indicates skeletal maturity.

Question 4408

Topic: Pediatric Hip

A 6-month-old female with developmental dysplasia of the hip (DDH) has failed 4 weeks of compliant Pavlik harness treatment. An ultrasound

reveals the hip remains persistently dislocated. What is the most appropriate next step in her management?

. Continue the Pavlik harness for an additional 4 weeks
. Switch to an abduction orthosis (e.g., Ilfeld splint)
. Closed reduction under anesthesia and spica casting
. Open reduction and femoral shortening osteotomy
. Varus derotational osteotomy (VDRO)

Correct Answer & Explanation

. Closed reduction under anesthesia and spica casting

Explanation

If a Pavlik harness fails to achieve reduction of a dislocated hip after 3 to 4 weeks of compliant use, it should be abandoned to prevent "Pavlik harness disease" (damage to the posterior acetabulum). The definitive next step in management for a 6-month-old is a closed reduction under general anesthesia, usually accompanied by an arthrogram and adductor tenotomy, followed by spica casting.

Question 4409

Topic: Pediatric Lower Extremity

According to the Ponseti method for the non-operative treatment of idiopathic clubfoot, serial casting must correct the components of the deformity in a highly specific order to prevent midfoot breach. What is the correct sequence of deformity correction?

. Cavus, Adductus, Varus, Equinus (CAVE)
. Equinus, Varus, Adductus, Cavus
. Cavus, Varus, Equinus, Adductus
. Adductus, Cavus, Varus, Equinus
. Varus, Adductus, Cavus, Equinus

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus (CAVE)

Explanation

The Ponseti method dictates that the deformities of clubfoot be corrected in the CAVE sequence: first the Cavus (by elevating the first ray to supinate the forefoot), then Adductus and Varus (simultaneously corrected by abducting the foot around the head of the talus), and finally Equinus (usually requiring a percutaneous Achilles tenotomy as the last step).

Question 4410

Topic: Pediatric Hip

A 13-year-old obese boy is brought to the emergency department strictly unable to bear weight on his left leg after a minor slip. Radiographs confirm a severe, unstable slipped capital femoral epiphysis (SCFE).

He undergoes urgent single-screw in situ fixation. Which of the following is the most feared and highest-risk complication specifically associated with an unstable SCFE compared to a stable SCFE?

. Chondrolysis
. Osteonecrosis (Avascular necrosis) of the femoral head
. Subtrochanteric femur fracture
. Slipped capital femoral epiphysis of the contralateral hip
. Deep vein thrombosis

Correct Answer & Explanation

. Osteonecrosis (Avascular necrosis) of the femoral head

Explanation

An unstable SCFE is defined clinically by the inability of the patient to ambulate, even with crutches. Unstable slips carry a profoundly higher risk of osteonecrosis (avascular necrosis) of the femoral head (ranging from 20% to nearly 50%), whereas AVN is exceedingly rare in stable SCFE. Chondrolysis is another complication but is classically associated with unrecognized pin joint penetration.

Question 4411

Topic: 4. Pediatrics

A child presenting with rhizomelic short stature, a prominent forehead, and midface hypoplasia is diagnosed with achondroplasia. What is the specific genetic and molecular basis of this condition?

. Defect in type I collagen synthesis (COL1A1)
. Gain-of-function mutation in FGFR3
. Loss-of-function mutation in COMP
. Defect in RUNX2 (CBFA1) transcription factor
. Mutation in the PHEX gene

Correct Answer & Explanation

. Gain-of-function mutation in FGFR3

Explanation

Achondroplasia is an autosomal dominant condition caused by a gain-of-function mutation in the Fibroblast Growth Factor Receptor 3 (FGFR3) gene. FGFR3 is normally a negative regulator of chondrocyte proliferation in the growth plate; its constant activation prematurely halts endochondral ossification. COL1A1/COL1A2 mutations cause osteogenesis imperfecta. COMP mutations cause pseudoachondroplasia and multiple epiphyseal dysplasia. RUNX2 mutations cause cleidocranial dysplasia. PHEX mutations cause X-linked hypophosphatemic rickets.

Question 4412

Topic: 4. Pediatrics

Slipped capital femoral epiphysis (SCFE) is a common adolescent hip disorder characterized by the displacement of the proximal femoral epiphysis. Pathologically, failure and slippage occur through which specific zone of the proximal femoral physis?

. Reserve zone
. Proliferative zone
. Zone of maturation
. Zone of provisional calcification
. Hypertrophic zone

Correct Answer & Explanation

. Hypertrophic zone

Explanation

In SCFE, the structural failure occurs through the hypertrophic zone of the physis. This zone is the weakest portion of the growth plate biomechanically due to the large size of the chondrocytes and the relatively low matrix-to-cell ratio. The hypertrophic zone is widened in SCFE, making it particularly vulnerable to shear stresses.

Question 4413

Topic: Pediatric Upper Extremity & Spine
A 6-year-old boy presents after falling from monkey bars with an extension-type Gartland III supracondylar humerus fracture. Examination reveals weak index finger flexion and absent flexion of the IP joint of the thumb. Which nerve is most likely 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) is the most commonly injured nerve in extension-type supracondylar humerus fractures. It is evaluated by checking the patient's ability to make an "OK" sign, requiring flexion of the thumb IP and index DIP joints.

Question 4414

Topic: 4. Pediatrics

A 9-month-old female is referred for asymmetric thigh folds. Ultrasound reveals a dysplastic left hip with a subluxated femoral head.

She has not received any prior treatment. What is the most appropriate initial management?

. Observation and repeat ultrasound in 6 weeks
. Application of a Pavlik harness
. Closed reduction and spica casting
. Open reduction via an anterior approach
. Proximal femoral varus derotational osteotomy

Correct Answer & Explanation

. Closed reduction and spica casting

Explanation

While the Pavlik harness is the gold standard for infants under 6 months with DDH, its success rate drops significantly in older infants. Closed reduction and spica casting is generally the preferred initial intervention for a child presenting at 6 to 18 months of age.

Question 4415

Topic: 4. Pediatrics

A 4-month-old infant is being treated with a Pavlik harness for developmental dysplasia of the hip. The parents report the child has stopped kicking the right leg. On examination, the infant lacks active knee extension but has normal ankle movements. What is the most likely cause?

. Excessive hip flexion
. Excessive hip extension
. Excessive hip adduction
. Excessive hip abduction
. Inadequate harness wear time

Correct Answer & Explanation

. Excessive hip flexion

Explanation

Excessive hip flexion in a Pavlik harness can compress the femoral nerve against the inguinal ligament, leading to femoral nerve palsy. This classically presents with absent active knee extension.

Question 4416

Topic: Pediatric Hip

A 13-year-old boy with a slipped capital femoral epiphysis (SCFE) cannot bear weight even with crutches. According to the Loder classification, this is an unstable SCFE. What is the most significant risk associated with an unstable SCFE compared to a stable SCFE?

. Chondrolysis
. Avascular necrosis (AVN)
. Femoral-acetabular impingement (FAI)
. Premature physeal closure
. Contralateral slip

Correct Answer & Explanation

. Avascular necrosis (AVN)

Explanation

An unstable SCFE (inability to bear weight with or without crutches) has a significantly higher risk of avascular necrosis (up to nearly 50%) compared to a stable SCFE, which has an AVN rate close to 0%.

Question 4417

Topic: 4. Pediatrics

A 6-year-old child sustains a completely displaced supracondylar humerus fracture. On examination, the hand is pink but lacks a palpable radial pulse. Capillary refill is less than 2 seconds. What is the most appropriate initial management?

. Immediate CT angiogram of the upper extremity
. Urgent closed reduction and percutaneous pinning
. Immediate open exploration of the brachial artery
. Prophylactic forearm fasciotomy
. Observation in a long arm splint at 90 degrees of flexion

Correct Answer & Explanation

. Urgent closed reduction and percutaneous pinning

Explanation

For a "pink, pulseless" hand following a supracondylar fracture, the initial step is urgent closed reduction and percutaneous pinning. Restoration of skeletal alignment relieves kinking of the brachial artery, which frequently restores palpable pulses without the need for open vascular exploration.

Question 4418

Topic: 4. Pediatrics
In the management of a Type III pediatric supracondylar humerus fracture, after closed reduction and pinning, the patient's hand remains a "pink, pulseless hand". Capillary refill is less than 2 seconds. What is the most appropriate next step?
. Immediate vascular exploration by a vascular surgeon
. Removal of all pins and open reduction
. Observation with close inpatient monitoring
. Fasciotomy of the forearm
. Arteriography of the upper extremity

Correct Answer & Explanation

. Observation with close inpatient monitoring

Explanation

A "pink, pulseless hand" with excellent perfusion (capillary refill <2 seconds) after reduction and pinning typically indicates vascular spasm rather than complete occlusion. The standard of care is close inpatient observation, as the pulse often returns within 24 to 48 hours.

Question 4419

Topic: 4. Pediatrics

A 6-year-old child presents with a grossly displaced extension-type supracondylar humerus fracture. Following closed reduction and percutaneous pinning, the hand is pink and capillary refill is less than 2 seconds, but the radial pulse remains completely absent. What is the most appropriate next step in management?

. Immediate open vascular exploration
. Doppler ultrasound of the brachial artery
. Observation and hospital admission for 24-48 hours
. CT angiography of the upper extremity
. Administration of intravenous heparin

Correct Answer & Explanation

. Observation and hospital admission for 24-48 hours

Explanation

According to AAOS guidelines, a 'pink, pulseless hand' following satisfactory reduction and pinning of a supracondylar fracture indicates adequate collateral perfusion. The standard of care is close observation and admission, as pulses typically return over time.

Question 4420

Topic: Pediatric Upper Extremity & Spine
A 6-year-old boy presents with a Gartland type III extension-type supracondylar humerus fracture. Examination reveals a pink, pulseless hand with intact capillary refill. Following closed reduction and percutaneous pinning, the radial pulse remains absent, but the hand remains pink and well-perfused. What is the most appropriate next step in management?
. Immediate exploration of the brachial artery via an anterior approach.
. Removal of the pins and open reduction via a posterior triceps-sparing approach.
. Observation and admission for continuous pulse oximetry and neurovascular checks.
. Emergent CT angiography of the upper extremity to localize the vascular lesion.
. Administration of systemic tissue plasminogen activator (tPA).

Correct Answer & Explanation

. Observation and admission for continuous pulse oximetry and neurovascular checks.

Explanation

In a pediatric supracondylar humerus fracture, a pink, pulseless hand following adequate closed reduction and pinning indicates sufficient collateral circulation. Current AAOS guidelines recommend close observation and admission rather than routine immediate vascular exploration, provided the hand remains well-perfused.

Test Yourself

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

On this Page