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4. Pediatrics MCQs

Practice Set 165 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 3281

Topic: 4. Pediatrics
A 9-year-old girl is evaluated for a limp and a leg length discrepancy. Radiographs of her proximal femur demonstrate a 'shepherd's crook' deformity with a ground-glass matrix in the medullary canal. She has a history of precocious puberty and café-au-lait macules with irregular, 'coast of Maine' borders. The underlying pathophysiology of her musculoskeletal condition involves a somatic activating mutation in a gene encoding for:
. Alpha subunit of the stimulatory G protein (Gs-alpha)
. Fibroblast growth factor receptor 3 (FGFR3)
. Cartilage oligomeric matrix protein (COMP)
. Type I collagen
. Adenomatous polyposis coli (APC)

Correct Answer & Explanation

. Alpha subunit of the stimulatory G protein (Gs-alpha)

Explanation

This patient has McCune-Albright syndrome, classically defined by the triad of polyostotic fibrous dysplasia, precocious puberty (or other endocrinopathies), and café-au-lait spots with irregular borders. The disease is caused by a somatic, post-zygotic activating mutation in the GNAS gene, which encodes the alpha subunit of the stimulatory G protein (Gs-alpha). This mutation results in constitutional activation of adenylate cyclase and overproduction of intracellular cAMP. FGFR3 mutations cause achondroplasia. COMP mutations are associated with pseudoachondroplasia and multiple epiphyseal dysplasia. Type I collagen defects cause osteogenesis imperfecta.

Question 3282

Topic: Pediatric Hip

A 14-year-old boy undergoes a surgical dislocation of the hip for treatment of severe slipped capital femoral epiphysis (SCFE). During the exposure, the surgeon must protect the primary blood supply to the femoral head. Which of the following vessels provides the predominant blood supply to the femoral head in this age group, and what is its anatomical course?

. Anterior ascending cervical branches of the lateral femoral circumflex artery
. Medial epiphyseal branches of the obturator artery via the ligamentum teres
. Posterosuperior and posteroinferior retinacular branches of the medial femoral circumflex artery
. Inferior gluteal artery branches running along the piriformis tendon
. Superior gluteal artery branches supplying the greater trochanteric anastomosis

Correct Answer & Explanation

. Posterosuperior and posteroinferior retinacular branches of the medial femoral circumflex artery

Explanation

The predominant blood supply to the adult and adolescent femoral head is derived from the medial femoral circumflex artery (MFCA). Specifically, the posterosuperior and posteroinferior retinacular branches of the MFCA pierce the capsule and run along the femoral neck to enter the head. During surgical dislocation, it is vital to protect the external rotators (particularly the obturator externus) to avoid stretching or severing the MFCA, which courses between the quadratus femoris and the obturator externus.

Question 3283

Topic: 4. Pediatrics

Following a closed reduction and percutaneous pinning of a displaced extension-type supracondylar humerus fracture, a 7-year-old child demonstrates an inability to flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger. Which of the following muscles is also most likely to be weakened due to this specific nerve injury?

. Flexor carpi radialis
. Flexor digitorum superficialis
. Pronator quadratus
. Pronator teres
. Abductor pollicis brevis

Correct Answer & Explanation

. Pronator quadratus

Explanation

The scenario describes an anterior interosseous nerve (AIN) palsy, which is the most common nerve injury associated with extension-type supracondylar humerus fractures. The AIN is a pure motor branch of the median nerve that innervates the flexor pollicis longus (FPL), the flexor digitorum profundus (FDP) to the index and middle fingers, and the pronator quadratus. The flexor carpi radialis, FDS, and pronator teres are innervated by the median nerve proximal to the AIN origin, while the abductor pollicis brevis is supplied by the recurrent motor branch.

Question 3284

Topic: 4. Pediatrics

A pediatric patient sustains a widely displaced supracondylar humerus fracture. Post-operatively, the patient presents with an inability to flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger.

The nerve responsible for this specific motor deficit branches from a major nerve trunk that classically travels between the two heads of which of the following muscles?

. Flexor carpi ulnaris
. Pronator teres
. Flexor digitorum superficialis
. Supinator
. Brachioradialis

Correct Answer & Explanation

. Pronator teres

Explanation

The clinical presentation describes an anterior interosseous nerve (AIN) palsy, a recognized complication of supracondylar humerus fractures. The AIN is a motor branch of the median nerve. The median nerve classically travels between the humeral and ulnar heads of the pronator teres muscle in the proximal forearm before passing under the fibrous arch of the flexor digitorum superficialis (FDS). The AIN typically branches off the median nerve precisely as it exits the pronator teres.

Question 3285

Topic: Pediatric Hip

A 12-year-old overweight boy is diagnosed with a severe slipped capital femoral epiphysis (SCFE). The treating orthopedic surgeon counsels the parents on the risk of avascular necrosis. The primary blood supply to the capital femoral epiphysis in this age group is derived from the lateral epiphyseal vessels. These vessels are terminal branches of which of the following arteries?

. Medial circumflex femoral artery
. Lateral circumflex femoral artery
. Inferior gluteal artery
. Obturator artery
. Internal pudendal artery

Correct Answer & Explanation

. Medial circumflex femoral artery

Explanation

In children older than 3 to 4 years of age and adolescents, the primary blood supply to the femoral head is derived from the lateral epiphyseal artery. This artery is a terminal branch of the medial circumflex femoral artery (MCFA). The artery of the ligamentum teres (a branch of the obturator artery) provides a negligible amount of blood supply in this age group. Disruption of the MCFA or its terminal branches during a SCFE or its surgical treatment can lead to avascular necrosis.

Question 3286

Topic: Pediatric Hip

A 26-year-old ice hockey player presents with insidious onset of anterior groin pain exacerbated by hip flexion and internal rotation. Radiographs demonstrate a crossover sign and an alpha angle of 70 degrees. What is the predominant pathomorphology causing his symptoms?

. Isolated Cam impingement
. Isolated Pincer impingement
. Combined Cam and Pincer impingement
. Developmental dysplasia of the hip
. Slipped capital femoral epiphysis

Correct Answer & Explanation

. Combined Cam and Pincer impingement

Explanation

The crossover sign indicates acetabular retroversion (Pincer morphology), while an alpha angle greater than 50-55 degrees indicates femoral head-neck junction asphericity (Cam morphology). Therefore, this patient has combined Cam and Pincer impingement.

Question 3287

Topic: Pediatric Upper Extremity & Spine
A 6-year-old boy falls on an outstretched hand and sustains a supracondylar humerus fracture. A radiograph reveals a completely displaced extension-type (Gartland Type III) fracture. On physical examination in the emergency department, an anterior interosseous nerve (AIN) palsy is diagnosed. Which of the following clinical findings is most likely present to confirm this diagnosis?
. Inability to flex the wrist with ulnar deviation
. Inability to flex the distal interphalangeal joint of the index finger
. Inability to extend the interphalangeal joint of the thumb
. Loss of sensation over the volar aspect of the index finger
. Inability to abduct the fingers against resistance

Correct Answer & Explanation

. Inability to flex the distal interphalangeal joint of the index finger

Explanation

Anterior interosseous nerve (AIN) palsy is the most common neurologic injury associated with extension-type supracondylar humerus fractures. The AIN is a pure motor branch of the median nerve that innervates the flexor pollicis longus (FPL), the flexor digitorum profundus (FDP) to the index and middle fingers, and the pronator quadratus. Clinically, it presents as an inability to make the 'A-OK' sign due to weakness in flexing the distal interphalangeal joint of the index finger and the interphalangeal joint of the thumb. It does not cause sensory deficits.

Question 3288

Topic: 4. Pediatrics

A 6-year-old girl with spastic quadriplegic cerebral palsy (GMFCS level V) is evaluated for hip pain and difficulty with perineal hygiene. An anteroposterior pelvis radiograph reveals a migration percentage of 45% on the right hip and 40% on the left hip, with moderate acetabular dysplasia.

What is the most appropriate surgical management for this patient?

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

Correct Answer & Explanation

. VDRO of the proximal femur combined with a volume-reducing pelvic osteotomy

Explanation

In children with cerebral palsy, hip surveillance is critical. For significant hip subluxation (migration percentage > 40%) with acetabular dysplasia in a child of this age, soft tissue releases alone are inadequate and have an unacceptably high failure rate. Bony reconstruction with a varus derotational osteotomy (VDRO) of the femur combined with a volume-reducing pelvic osteotomy (e.g., Dega or San Diego osteotomy) is the gold standard. It provides durable coverage, reduces the head into the true acetabulum, and halts progressive subluxation.

Question 3289

Topic: 4. Pediatrics

A 6-week-old female infant is undergoing treatment with a Pavlik harness for developmental dysplasia of the left hip. During the 2-week follow-up visit, the mother notes that the child has stopped kicking her left leg. On physical examination, the infant exhibits an absent patellar reflex on the left side and decreased active knee extension. Sensibility appears intact. What is the most appropriate next step in management?

. Adjust the anterior straps to increase hip flexion past 120 degrees
. Adjust the posterior straps to increase hip abduction
. Perform a closed reduction and application of a hip spica cast
. Remove the harness entirely until active knee extension returns
. Re-evaluate with ultrasound and continue the harness unmodified

Correct Answer & Explanation

. Remove the harness entirely until active knee extension returns

Explanation

The clinical scenario describes a femoral nerve palsy, a known complication of Pavlik harness treatment resulting from excessive hip flexion (typically > 120 degrees), which compresses the femoral nerve against the rim of the pelvis. The standard and most appropriate management is to remove the harness or cease its use until quadriceps function returns (which usually takes a few days to a few weeks). Only after the nerve palsy has resolved should alternative bracing or modified harness treatment be attempted.

Question 3290

Topic: Pediatric Lower Extremity

A 4-year-old boy presents with a relapsed left idiopathic clubfoot. The deformity was initially treated successfully in infancy with the Ponseti method. The parents report he is now walking on the outside of his foot. Gait analysis demonstrates dynamic supination of the foot during the swing phase. Physical examination reveals an easily correctable deformity with completely passive plantigrade positioning. What is the most appropriate surgical treatment?

. Achilles tendon lengthening and plantar fascia release
. Transfer of the anterior tibial tendon to the lateral cuneiform
. Lateral column lengthening osteotomy
. Split posterior tibial tendon transfer to the peroneus brevis
. A short period of Ponseti casting followed by anterior tibial tendon transfer

Correct Answer & Explanation

. Transfer of the anterior tibial tendon to the lateral cuneiform

Explanation

Relapsed clubfoot frequently presents with dynamic supination due to muscle imbalance, predominantly overactivity of the anterior tibial tendon (ATT) overpowering the peroneal muscles. The definitive treatment for dynamic supination in a relapsed clubfoot is a transfer of the entire ATT to the lateral cuneiform. However, a strict prerequisite for this tendon transfer is that the foot must be completely passively correctable. Any residual fixed deformity must first be corrected by a short period of serial Ponseti casting before the tendon transfer is performed.

Question 3291

Topic: Pediatric Hip
An 8-year-old boy presents with a 3-month history of a painless limp and right hip stiffness. Radiographs demonstrate fragmentation of the capital femoral epiphysis. Measurements reveal that exactly 40% of the lateral pillar height is maintained. According to the Herring Lateral Pillar Classification, what group does this patient fall into, and what is the typical outcome associated with surgical containment for his age and classification?
. Group B; surgical containment leads to a significantly better Stulberg outcome
. Group B/C border; excellent outcomes with non-weight-bearing alone
. Group C; surgical containment leads to a significantly better Stulberg outcome
. Group C; outcomes are generally poor, and surgical containment provides no significant benefit over non-operative care
. Group A; outcomes are universally excellent regardless of treatment

Correct Answer & Explanation

. Group C; outcomes are generally poor, and surgical containment provides no significant benefit over non-operative care

Explanation

The Herring Lateral Pillar Classification evaluates the height of the lateral pillar of the capital femoral epiphysis during the fragmentation stage of Legg-Calvé-Perthes disease. Group A retains 100% height, Group B retains >50% height, and Group C retains <50% height. This patient has 40% height, placing him in Group C. For children 8 years of age and older with Group C hips, the prognosis is generally poor (high likelihood of Stulberg III-V outcome). Large multicenter studies have demonstrated that surgical containment (e.g., femoral or pelvic osteotomy) does not significantly improve radiographic outcomes compared to non-operative treatment in this specific subgroup.

Question 3292

Topic: 4. Pediatrics
A 6-year-old girl with Osteogenesis Imperfecta (Sillence Type III) is referred to the orthopedic clinic after sustaining her fourth diaphyseal femur fracture in two years. She is currently undergoing cyclic intravenous bisphosphonate therapy. Which of the following surgical interventions is the gold standard for managing recurrent diaphyseal femur fractures in this patient population?
. Open reduction and internal fixation with locked compression plating
. Application of a circular fine-wire external fixator
. Insertion of a Fassier-Duval telescopic intramedullary rod
. Insertion of static flexible intramedullary titanium elastic nails (TENs)
. Prolonged hip spica cast immobilization after closed reduction

Correct Answer & Explanation

. Insertion of a Fassier-Duval telescopic intramedullary rod

Explanation

In patients with moderate to severe Osteogenesis Imperfecta (OI) exhibiting recurrent fractures or progressive long bone bowing, intramedullary rodding is the standard of care to straighten the bone, prevent recurrent fractures, and provide internal support. Telescopic rods, such as the Fassier-Duval rod, are the gold standard for growing children because they elongate with the child's growth. This prevents the bone from 'growing off' the end of the rod, a common complication with static rods (like TENs) that leads to fractures adjacent to the implant. Plate fixation is contraindicated due to poor bone stock and the high risk of stress risers.

Question 3293

Topic: 4. Pediatrics
A newborn male is evaluated in the nursery for a significant right upper extremity deformity. The forearm is shortened and bowed volarly, and the hand is in fixed radial deviation. Radiographs confirm an absent radius and an absent thumb. Before addressing the orthopedic deformity, which of the following systemic evaluations is most critical?
. Cranial ultrasound and electroencephalogram (EEG)
. Echocardiogram and renal ultrasound
. Ophthalmic examination for cataracts
. Thyroid function tests and growth hormone levels
. Gastrointestinal endoscopy for midgut volvulus

Correct Answer & Explanation

. Echocardiogram and renal ultrasound

Explanation

Radial longitudinal deficiency (radial clubhand) is highly associated with several systemic syndromes. The most critical and common associations include VACTERL association (Vertebral anomalies, Anal atresia, Cardiac defects, Tracheoesophageal fistula, Renal anomalies, Limb defects), Holt-Oram syndrome (cardiac septal defects), and TAR syndrome (Thrombocytopenia-Absent Radius). Therefore, a thorough systemic workup is mandatory prior to any surgical intervention. An echocardiogram and a renal ultrasound are paramount to rule out potentially life-threatening congenital heart and renal anomalies.

Question 3294

Topic: 4. Pediatrics
A 2-year-old boy presents with a 3-day history of right knee swelling, a mild limp, and a low-grade fever (37.9°C). Initial laboratory work reveals a WBC count of 11,000/mm³, an ESR of 30 mm/hr, and a CRP of 2.5 mg/dL. Synovial fluid aspiration yields 65,000 WBCs/mm³ with 80% neutrophils. Gram stain is negative, and routine aerobic solid cultures show no growth at 48 hours. Which of the following pathogens is the most likely culprit, and what specific diagnostic technique is required to identify it?
. Staphylococcus aureus; prolonged incubation on standard blood agar
. Borrelia burgdorferi; dark-field microscopy of synovial fluid
. Kingella kingae; inoculation in BACTEC blood culture vials or PCR assay
. Streptococcus pneumoniae; culturing on chocolate agar at 4°C
. Neisseria gonorrhoeae; immediate plating on Thayer-Martin agar

Correct Answer & Explanation

. Kingella kingae; inoculation in BACTEC blood culture vials or PCR assay

Explanation

Kingella kingae is a leading cause of pediatric osteoarticular infections, particularly in children under 4 years of age. Clinically, it frequently presents with milder systemic symptoms (low-grade fever, mildly elevated ESR/CRP) compared to infections caused by Staphylococcus aureus. K. kingae is famously fastidious and rarely grows on routine solid media. Diagnosis is significantly enhanced by directly inoculating the synovial fluid into aerobic BACTEC blood culture vials or by utilizing nucleic acid amplification tests (PCR).

Question 3295

Topic: Pediatric Hip

A 13-year-old obese male presents with an inability to bear weight on the right leg after a minor fall. He reports having had a mild, aching knee pain for 2 months prior to the fall. Radiographs reveal a severe posterior and inferior displacement of the proximal femoral epiphysis. If an open reduction and internal fixation via a surgical dislocation approach (modified Dunn procedure) is planned, preservation of which of the following vessels is most critical to prevent osteonecrosis of the femoral head?

. Ascending branch of the lateral circumflex femoral artery
. Deep branch of the medial circumflex femoral artery
. Artery of the ligamentum teres
. Inferior gluteal artery
. Superior gluteal artery

Correct Answer & Explanation

. Deep branch of the medial circumflex femoral artery

Explanation

The deep branch of the medial circumflex femoral artery (MCFA) is the primary blood supply to the femoral head in adolescents. During a modified Dunn procedure for an unstable slipped capital femoral epiphysis (SCFE), meticulous protection of the external rotator muscles and the retinacular vessels arising from the deep branch of the MCFA is paramount to minimize the high risk of avascular necrosis.

Question 3296

Topic: Pediatric Hip

A 6-week-old female is being treated with a Pavlik harness for a dislocated left hip. At the 2-week follow-up, an ultrasound confirms the hip remains dislocated. The examiner also notes that the infant has decreased spontaneous extension of the left knee, though she vigorously kicks the right leg. What is the most likely cause of this new clinical finding?

. Transient synovitis of the hip
. Femoral nerve palsy from hyperflexion
. Obturator nerve palsy from hyperabduction
. Sciatic nerve palsy from harness straps
. Avascular necrosis of the femoral head

Correct Answer & Explanation

. Femoral nerve palsy from hyperflexion

Explanation

Femoral nerve palsy is a well-documented complication of the Pavlik harness, typically caused by hyperflexion of the hip which compresses the nerve against the inguinal ligament. It presents as decreased active knee extension. When this occurs, or if the hip fails to reduce after 3-4 weeks of harness wear, the harness must be discontinued to prevent further nerve damage and 'Pavlik harness disease' (excoriation, dysplasia, or AVN).

Question 3297

Topic: Pediatric Upper Extremity & Spine
A 6-year-old boy falls from the monkey bars and sustains a completely displaced, extension-type supracondylar humerus fracture. On arrival, his hand is pink but the radial pulse is absent. Capillary refill is brisk (< 2 seconds). Following closed reduction and percutaneous pinning, the hand remains pink with brisk capillary refill, but the radial pulse remains unpalpable. What is the next best step in management?
. Immediate exploration of the brachial artery
. Removal of pins and open reduction
. Observation and admission for 24-48 hours
. Urgent CT angiography of the upper extremity
. Prophylactic volar fasciotomy of the forearm

Correct Answer & Explanation

. Observation and admission for 24-48 hours

Explanation

The management of a 'pink, pulseless' hand following a well-reduced and pinned supracondylar humerus fracture is observation. Because perfusion is clinically adequate (pink color, brisk capillary refill), the collateral circulation is sufficient to sustain the limb. Vascular exploration is indicated only if the hand becomes white and pulseless (ischemia) after reduction, which suggests brachial artery entrapment or severe intimal injury without adequate collateral flow.

Question 3298

Topic: Pediatric Hip
An 8-year-old boy presents with a limp and right hip pain of several months' duration. Radiographs demonstrate sclerosis and early fragmentation of the proximal femoral epiphysis. Which of the following is considered the most significant prognostic factor for the development of early osteoarthritis in patients with this condition?
. Age at clinical onset
. Gender of the patient
. Presence of a Gage sign
. Limitation of internal rotation
. Family history of the disease

Correct Answer & Explanation

. Age at clinical onset

Explanation

Age at clinical onset is the single most important prognostic factor in Legg-Calvé-Perthes disease. Children who present at an older age (typically defined as > 8 years) have less remaining growth potential for femoral head remodeling, leading to an increased risk of permanent aspherical deformity (coxa magna) and subsequent early-onset osteoarthritis. A Gage sign is a radiographic 'head at risk' sign, but age remains the primary prognostic determinant.

Question 3299

Topic: 4. Pediatrics

A 7-year-old with spastic quadriplegic cerebral palsy (GMFCS Level V) presents for routine hip surveillance. An AP pelvis radiograph demonstrates a migration percentage (Reimer's index) of 45% on the right and 15% on the left. Clinically, the right hip can be abducted to 20 degrees. What is the most appropriate management for the right hip?

. Botulinum toxin injection to the adductors
. Bilateral adductor tenotomies
. Varus derotational osteotomy (VDRO) with or without pelvic osteotomy
. Total hip arthroplasty
. Observation with repeat radiographs in 1 year

Correct Answer & Explanation

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

Explanation

In children with cerebral palsy, a migration percentage > 40% combined with restricted abduction typically indicates progressive hip subluxation that is no longer amenable to soft-tissue releases alone. Bony reconstruction with a varus derotational osteotomy (VDRO) of the proximal femur, frequently accompanied by a pelvic osteotomy (e.g., Dega or San Diego), is the standard of care to restore joint congruency and prevent painful dislocation.

Question 3300

Topic: 4. Pediatrics

A newborn is evaluated for a shortened right lower extremity. Physical examination reveals an anteromedial bowing of the tibia, a dimple over the anterior mid-tibia, and an absent lateral ray (3-ray foot).

Which of the following is the most common associated skeletal anomaly found in the ipsilateral limb of patients with this specific condition?

. Congenital femoral deficiency
. Developmental dysplasia of the hip
. Congenital pseudarthrosis of the tibia
. Tarsal coalition
. Idiopathic clubfoot

Correct Answer & Explanation

. Congenital femoral deficiency

Explanation

The clinical presentation is classic for fibular hemimelia, which includes anteromedial tibial bowing, an anterior dimple, and absent lateral rays of the foot. Fibular hemimelia is highly associated with congenital femoral deficiency (formerly proximal focal femoral deficiency), as well as cruciate ligament deficiency and ball-and-socket ankle geometry. Pseudarthrosis of the tibia is typically associated with anterolateral bowing and neurofibromatosis type 1.

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