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 1121
Topic: 4. Pediatrics
A 24-year-old male with a history of Multiple Hereditary Exostoses (MHE) presents with enlarging, painless masses around his knees. He brings genetic testing results indicating a mutation in the EXT1 gene. What is the precise molecular consequence of this mutation?
Correct Answer & Explanation
. Decreased synthesis of heparan sulfate proteoglycans
Explanation
EXT1 and EXT2 genes encode glycosyltransferases responsible for the synthesis of heparan sulfate. Mutations in these genes lead to a deficiency in heparan sulfate proteoglycans, altering normal chondrocyte proliferation and maturation.
Question 1122
Topic: 4. Pediatrics
A 6-year-old boy falls from monkey bars and sustains a significantly displaced extension-type supracondylar humerus fracture. On examination, he is unable to make an 'A-OK' sign. Which of the following muscle functions is directly impaired?
Correct Answer & Explanation
. Flexor pollicis longus and flexor digitorum profundus to the index finger
Explanation
The inability to make an 'A-OK' sign points to an anterior interosseous nerve (AIN) palsy, the most common nerve injury in extension-type pediatric supracondylar humerus fractures. The AIN innervates the flexor pollicis longus and the flexor digitorum profundus of the index and middle fingers.
Question 1123
Topic: 4. Pediatrics
A 12-year-old boy presents with multiple painless, hard bony bumps around his knees and ankles. Radiographs reveal multiple sessile and pedunculated lesions pointing away from the joint line. Mutations in which of the following genes are most commonly associated with this patient's underlying condition?
Correct Answer & Explanation
. EXT1
Explanation
Multiple hereditary exostoses (MHE) is an autosomal dominant disorder caused by loss-of-function mutations in the EXT1 or EXT2 genes, which are involved in heparan sulfate synthesis. FGFR3 is associated with achondroplasia, and COL1A1 is linked to osteogenesis imperfecta.
Question 1124
Topic: 4. Pediatrics
A 6-year-old child presents with a crush injury to the distal phalanx of the thumb, exhibiting a Salter-Harris Type I physeal fracture with an associated nail bed laceration and dorsal displacement of the distal fragment. This injury pattern, commonly known as a Seymour fracture, requires specific management to prevent long-term complications. Which of the following is the most critical step in its surgical management?
Correct Answer & Explanation
. Open reduction, meticulous repair of the germinal matrix tear, and percutaneous K-wire fixation across the physis.
Explanation
Correct Answer: BTheDetailed Surgical Approach and Techniquesection, underDistal Phalanx Fracture Management, specifically addressesSeymour Fractures (Physeal Fractures): 'These require meticulous reduction and often involve direct repair of the nail bed tear (germinal matrix) and percutaneous K-wire fixation across the physis to stabilize the distal fragment.' This comprehensive approach is critical to prevent complications such as growth arrest and chronic nail deformity.Incorrect Options:A. Closed reduction and splinting without nail bed exploration:This is inadequate for a Seymour fracture, as the nail bed laceration (germinal matrix tear) must be repaired to prevent chronic nail deformity and potential infection.C. Excision of the nail plate and simple trephination of any hematoma:While nail plate removal is often necessary for exploration, simple trephination is insufficient; the underlying germinal matrix tear requires meticulous repair.D. Application of a volar plate and screw construct for rigid fixation:Plate and screw fixation is generally not used for distal phalangeal physeal fractures in children due to the small size of the bone, the presence of the physis, and the risk of growth disturbance. K-wires are the standard.E. Primary amputation due to high risk of growth arrest:Primary amputation is an extreme measure and is not indicated for a Seymour fracture, which is typically salvageable with appropriate surgical management.
Question 1125
Topic: 4. Pediatrics
During preoperative planning for a nail unit repair, the surgeon discusses anesthesia options. While a digital block with plain lidocaine is commonly used, the case mentions an evolving concept regarding the use of vasoconstrictors. Which statement accurately reflects the current understanding regarding epinephrine in digital blocks for nail unit injuries, as presented in the case?
Correct Answer & Explanation
. Current evidence suggests judicious use of lidocaine with epinephrine is safe for digital blocks in non-compromised digits, though many surgeons still prefer plain lidocaine.
Explanation
Correct Answer: CUnder theSummary of Key Literature and Guidelinessection, inEvolving Concepts and Controversies, it states: 'The long-held dogma of avoiding epinephrine in digital blocks has been challenged by recent evidence. Multiple prospective studies and meta-analyses, particularly in emergency medicine and hand surgery literature, suggest that the judicious use of lidocaine with epinephrine is safe for digital blocks in non-compromised digits, offering prolonged anesthesia and a bloodless field. However, many orthopedic surgeons still prefer plain lidocaine for nail unit repair to mitigate any perceived, albeit low, risk.'Incorrect Options:A. Epinephrine is absolutely contraindicated in all digital blocks due to high risk of digital ischemia:This reflects the outdated dogma, which has been challenged by recent evidence.B. Epinephrine is recommended for all digital blocks to ensure a bloodless field and prolonged anesthesia:While it offers these benefits, the case notes that 'many orthopedic surgeons still prefer plain lidocaine,' indicating it's not universally recommended for all cases.D. Epinephrine should only be used in pediatric patients to minimize pain during the procedure:The case does not specify its use only for pediatric patients or primarily for pain minimization, but rather for prolonged anesthesia and a bloodless field in non-compromised digits.E. The use of epinephrine in digital blocks is a new technique with no supporting evidence for safety:This is incorrect; the case explicitly mentions 'multiple prospective studies and meta-analyses' supporting its judicious use.
Question 1126
Topic: 4. Pediatrics
A 1-year-old child presents with a hypoplastic thumb. On examination, the thumb is slightly shortened and narrowed, but all intrinsic and extrinsic muscles appear to be present and functional. The carpometacarpal (CMC) joint is stable, and the first web space is adequate, allowing for nearly full abduction and opposition. Radiographs confirm normal skeletal components, albeit slightly hypoplastic. The child's parents report mild difficulty with fine motor tasks requiring precise pinch. Based on the Blauth classification, what is the most appropriate initial management strategy?
Correct Answer & Explanation
. Observation with regular follow-up and referral for occupational therapy.
Explanation
The clinical presentation describes a Blauth Type I hypoplastic thumb: slight shortening and narrowing, intact intrinsic and extrinsic musculature, normal skeletal components, stable CMC joint, and adequate first web space. Blauth Type I thumbs typically have minimal functional deficit. The primary management for Blauth Type I is observation with regular follow-up and referral for occupational therapy to optimize existing function and monitor for any progression of functional impairment. Surgical intervention is generally not indicated for Type I unless significant functional limitations develop that cannot be addressed non-operatively.
Question 1127
Topic: 4. Pediatrics
A 6-month-old infant presents with a hypoplastic thumb. Physical examination reveals a narrow first web space, palpable but weak abductor pollicis brevis (APB) muscle, and a stable carpometacarpal (CMC) joint. Radiographs show a hypoplastic first metacarpal and phalanges, but all skeletal elements are present. The child is unable to achieve effective pinch or grasp. Which of the following surgical interventions is most appropriate for this presentation?
Correct Answer & Explanation
. First web space deepening (e.g., Z-plasty) combined with an opposition tendon transfer.
Explanation
This clinical scenario describes a Blauth Type II hypoplastic thumb: moderate hypoplasia with a narrow first web space, mild intrinsic muscle deficiency (weak APB), and a stable CMC joint. The extrinsic muscles are generally present, and skeletal elements are diminished but present. Management involves first web space deepening (e.g., Z-plasty or dorsal rotation flap) often combined with an opposition tendon transfer if the APB is functionally deficient. The goal is to improve abduction and opposition.
Question 1128
Topic: 4. Pediatrics
A 4-year-old child who underwent reconstruction for a Blauth Type IIIA hypoplastic thumb 6 months ago presents with a progressive inability to abduct the thumb away from the palm, despite diligent post-operative therapy. Examination reveals a tight, contracted first web space and limited active opposition. The CMC joint remains stable. What is the most likely complication and its appropriate initial salvage strategy?
Correct Answer & Explanation
. Recurrent adduction contracture; revision web space deepening (e.g., repeat Z-plasty or dorsal rotation flap).
Explanation
The patient's symptoms of 'progressive inability to abduct the thumb away from the palm' and a 'tight, contracted first web space' despite therapy are classic signs of recurrent adduction contracture. The case material lists 'Recurrent Adduction Contracture' as a common complication (10-30% incidence) and states its salvage strategy: 'Aggressive post-operative splinting/therapy. Serial casting. If established, revision web space deepening (repeat Z-plasty, dorsal rotation flap), full-thickness skin grafting, or release of deeper structures (adductor pollicis tenotomy/myotomy).' Since the contracture is established and progressive, revision web space deepening is the most appropriate surgical salvage strategy.
Question 1129
Topic: 4. Pediatrics
A 7-year-old patient with a history of Blauth Type IIIA hypoplastic thumb reconstruction 3 years prior presents with persistent, severe instability of the carpometacarpal (CMC) joint, significantly compromising pinch strength. Previous capsulodesis and K-wire fixation failed to provide lasting stability. The patient is otherwise healthy. What is the most appropriate surgical option for this patient's CMC joint instability?
Correct Answer & Explanation
. CMC joint arthrodesis.
Explanation
CMC arthrodesis is indicated for severe, intractable CMC instability in older patients, failed previous reconstructions, or arthritic changes. Given the patient is 7 years old, has persistent severe instability after a failed capsulodesis, and is experiencing functional compromise, CMC arthrodesis is the most appropriate definitive solution to provide a stable base for pinch.
Question 1130
Topic: 4. Pediatrics
A 1-year-old patient is diagnosed with a Blauth Type IIIA hypoplastic thumb. During the pre-operative workup, the orthopedic surgeon orders a thorough diagnostic evaluation to identify potential systemic associations. Which of the following syndromes or conditions is most commonly associated with congenital thumb hypoplasia and should be specifically screened for?
Correct Answer & Explanation
. VACTERL association.
Explanation
Thumb hypoplasia can occur as an isolated anomaly or, more commonly, in association with other syndromes and conditions, including VACTERL association (vertebral defects, anal atresia, cardiac defects, tracheoesophageal fistula, renal anomalies, limb defects). Other associated conditions include Fanconi's anemia, Holt-Oram syndrome, and thrombocytopenia-absent radius (TAR) syndrome.
Question 1131
Topic: 4. Pediatrics
A newborn presents with bilateral absent thumbs and severe radial hypoplasia. Echocardiogram reveals an atrial septal defect. Genetic testing is most likely to show a mutation in which of the following genes?
Correct Answer & Explanation
. TBX5
Explanation
Holt-Oram syndrome is an autosomal dominant condition caused by a TBX5 gene mutation, presenting with radial longitudinal deficiency and congenital heart defects. Unlike TAR syndrome, the thumb is frequently hypoplastic or absent.
Question 1132
Topic: 4. Pediatrics
A 9-year-old boy sustains a hyperflexion injury to his long finger, resulting in a clinically displaced Salter-Harris I fracture of the distal phalanx and an associated laceration at the proximal nail fold with the nail plate resting superficial to the eponychium. What is the most critical step in initial management?
Correct Answer & Explanation
. Removal of the nail plate, copious irrigation, and repair of the germinal matrix
Explanation
This describes a Seymour fracture, an open physeal fracture of the distal phalanx with an associated nail bed injury. Management requires nail plate removal, irrigation, and meticulous repair of the matrix to prevent osteomyelitis and premature physeal closure.
Question 1133
Topic: Pediatric Upper Extremity & Spine
A 1-year-old boy with a Blauth Type IV thumb hypoplasia is being evaluated for pollicization. He is noted to have short stature and café-au-lait spots. Which of the following laboratory tests is mandatory before proceeding with elective surgery?
Correct Answer & Explanation
. Diepoxybutane (DEB) chromosomal breakage test
Explanation
The patient's presentation suggests Fanconi anemia, an autosomal recessive disorder associated with radial longitudinal deficiency and aplastic anemia. The diagnosis is confirmed by demonstrating increased chromosomal breakage in the presence of clastogenic agents like diepoxybutane (DEB).
Question 1134
Topic: Pediatric Upper Extremity & Spine
A neonate is evaluated in the nursery for bilateral upper extremity anomalies. Examination reveals bilateral absent radii, but the thumbs are present and appear normal. What systemic hematologic abnormality is classically associated with this specific presentation?
Correct Answer & Explanation
. Thrombocytopenia
Explanation
Thrombocytopenia Absent Radius (TAR) syndrome is uniquely characterized by the absence of the radius with the preservation of the thumb. This distinguishes it from Fanconi anemia or Holt-Oram syndrome, where the thumb is typically hypoplastic or absent.
Question 1135
Topic: 4. Pediatrics
A 7-year-old boy catches his finger in a door, sustaining an injury where the proximal nail plate rests superficial to the eponychium.
Radiographs confirm a displaced distal phalanx physeal fracture. What is the most appropriate management?
Correct Answer & Explanation
. Nail plate removal, copious irrigation, fracture reduction, and nail bed repair
Explanation
This describes a Seymour fracture (an open Salter-Harris I or II fracture of the distal phalanx with an associated nail bed injury). Treatment requires nail removal, thorough irrigation, anatomical nail bed repair, and fracture reduction.
Question 1136
Topic: 4. Pediatrics
A 1-year-old child with severe congenital thumb hypoplasia and radial longitudinal deficiency is suspected of having Fanconi anemia. Which diagnostic test is the gold standard for confirming this syndrome?
Correct Answer & Explanation
. Chromosomal breakage testing with diepoxybutane (DEB)
Explanation
Fanconi anemia is an autosomal recessive condition associated with radial limb defects and potentially fatal aplastic anemia. It is diagnosed using a chromosomal breakage test stimulated by diepoxybutane (DEB) or mitomycin C.
Question 1137
Topic: 4. Pediatrics
In patients with Blauth Type II or IIIA thumb hypoplasia, the flexor pollicis longus (FPL) tendon frequently exhibits an aberrant anatomical characteristic known as "pollex abductus." What is the defining feature of this anomaly?
Correct Answer & Explanation
. A tendinous connection between the FPL and the extensor pollicis longus (EPL)
Explanation
Pollex abductus is a congenital anomaly frequently seen in thumb hypoplasia, characterized by an anomalous tendinous slip connecting the flexor pollicis longus to the extensor mechanism (EPL).
Question 1138
Topic: Pediatric Lower Extremity
A 9-year-old boy with Duchenne Muscular Dystrophy presents with progressive tiptoe walking and frequent tripping. On examination, what is the most typical lower extremity contracture pattern driving this gait abnormality in ambulatory DMD patients?
Correct Answer & Explanation
. Equinovarus
Explanation
Equinovarus contractures are the most common deformity in ambulatory boys with DMD. This is due to the relative sparing and overpull of the posterior tibialis muscle and Achilles tendon compared to the weaker dorsiflexors and evertors.
Question 1139
Topic: Pediatric Hip
A 12-year-old girl with a history of chronic renal failure and renal osteodystrophy presents with a unilateral slipped capital femoral epiphysis (SCFE). After successful in situ pinning of the symptomatic hip, what is the most appropriate management for the contralateral asymptomatic hip?
Correct Answer & Explanation
. Prophylactic in situ pinning
Explanation
Patients with underlying endocrine disorders or renal failure are at a significantly elevated risk for bilateral SCFE. Prophylactic pinning of the contralateral asymptomatic hip is strongly indicated in this population to prevent future displacement.
Question 1140
Topic: Pediatric Hip
A 4-month-old infant is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). During a follow-up visit, the parents report the infant has stopped kicking the affected leg. Physical examination reveals absent active knee extension. Which harness adjustment error most likely caused this complication?
Correct Answer & Explanation
. Excessive hip flexion
Explanation
Excessive hip flexion in a Pavlik harness can lead to compression of the femoral nerve against the inguinal ligament, causing transient femoral nerve palsy. Excessive hip abduction is classically associated with avascular necrosis (AVN) of the femoral head.
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