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4. Pediatrics MCQs

Practice Set 59 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 1161

Topic: Pediatric Hip

A 13-year-old obese male presents with acute severe groin pain and an inability to bear weight. Radiographs show a slipped capital femoral epiphysis (SCFE). He is diagnosed with an unstable SCFE. Which of the following is the most significant risk factor for the development of avascular necrosis (AVN) in this patient?

. The radiographic slip angle exceeding 50 degrees
. The clinical instability of the slip (inability to bear weight)
. Prophylactic pinning of the contralateral hip
. Surgical intervention delayed beyond 24 hours
. Patient body mass index (BMI) greater than the 95th percentile

Correct Answer & Explanation

. The clinical instability of the slip (inability to bear weight)

Explanation

The defining feature of an unstable SCFE is the clinical inability to bear weight, even with crutches. This instability correlates with a significantly higher risk of AVN (up to 50%) compared to stable slips.

Question 1162

Topic: 4. Pediatrics

An examiner presents a case of a 5-year-old child with a completely displaced, extension-type supracondylar humerus fracture. Post-reduction and pinning, the child's hand is pink but pulseless. The examiner asks for the next step. What is the safest, most appropriate response?

. Immediate exploration of the brachial artery.
. Remove the pins and leave the arm in extension.
. Observe the patient closely, as a pink, pulseless hand typically indicates adequate collateral perfusion.
. Perform a sympathetic nerve block.
. Administer intravenous heparin.

Correct Answer & Explanation

. Observe the patient closely, as a pink, pulseless hand typically indicates adequate collateral perfusion.

Explanation

A pink, pulseless hand following adequate reduction and stabilization of a supracondylar humerus fracture is generally observed, as collateral circulation is sufficient. Vascular exploration is indicated if the hand becomes pale, cold, and poorly perfused.

Question 1163

Topic: Pediatric Hip

A 12-year-old obese male presents with left knee pain and an obligate external rotation of the hip during passive flexion. Radiographs confirm a mild stable slipped capital femoral epiphysis (SCFE). What is a primary indication for prophylactic pinning of the contralateral asymptomatic hip?

. Age greater than 14 years
. Female gender
. Endocrine disorders such as hypothyroidism or renal osteodystrophy
. Body mass index greater than 35
. Participation in contact sports

Correct Answer & Explanation

. Endocrine disorders such as hypothyroidism or renal osteodystrophy

Explanation

Endocrine disorders significantly increase the risk of developing bilateral SCFE. Prophylactic pinning of the contralateral hip is highly recommended in these specific metabolic populations.

Question 1164

Topic: Pediatric Hip

A 6-month-old female with developmental dysplasia of the hip (DDH) is planned for closed reduction and spica casting. According to Ramsey's criteria, the 'safe zone' of reduction is defined by the arc between the angle of maximum abduction and the angle of:

. Maximum adduction
. Maximum flexion
. Maximum internal rotation
. Redislocation (adduction)
. Maximum extension

Correct Answer & Explanation

. Redislocation (adduction)

Explanation

The safe zone of Ramsey is the arc of motion between maximum abduction and the angle of redislocation. Maintaining the hip within this zone minimizes AVN risk while preventing loss of reduction.

Question 1165

Topic: Pediatric Lower Extremity

Patella alta is a known risk factor for recurrent patellar instability. Which of the following correctly describes the Caton-Deschamps index used to diagnose this condition?

. The ratio of the patellar tendon length to the greatest diagonal length of the patella.
. The ratio of the distance from the inferior articular margin of the patella to the anterior superior angle of the tibia, divided by the patellar articular surface length.
. The perpendicular distance from the inferior pole of the patella to the tibial plateau line, divided by the patellar articular surface length.
. The angle formed by the lines connecting the highest points of the medial and lateral femoral condyles to the deepest point of the trochlear groove.
. The distance between the tibial tubercle and the deepest portion of the trochlear groove.

Correct Answer & Explanation

. The ratio of the distance from the inferior articular margin of the patella to the anterior superior angle of the tibia, divided by the patellar articular surface length.

Explanation

The Caton-Deschamps index relies on articular margins rather than the inferior pole, making it useful even if a patient has had Osgood-Schlatter disease or previous distal pole excision. A value greater than 1.2 indicates patella alta.

Question 1166

Topic: 4. Pediatrics

A 7-year-old child presents with a severe congenital tibial deformity where the CORA is precisely located at the open proximal tibial physis. The surgeon needs to correct the angular deformity while preserving the growth plate. Which of Paley's Osteotomy Rules is the most appropriate strategy for this scenario, and what is its expected outcome?

. Rule One, performing the osteotomy directly at the physis to achieve pure angular correction.
. Rule Two, placing the hardware hinge (ACA) at the physis (CORA) but performing the osteotomy in the healthy metaphysis, resulting in planned translation at the osteotomy site.
. Rule Three, placing the hardware hinge (ACA) distal to the physis and performing the osteotomy at the physis, leading to iatrogenic translation.
. Rule One, but only if an acute correction is performed to minimize growth plate disturbance.
. Rule Three, as it allows for a gradual correction that is safer for the physis.

Correct Answer & Explanation

. Rule Two, placing the hardware hinge (ACA) at the physis (CORA) but performing the osteotomy in the healthy metaphysis, resulting in planned translation at the osteotomy site.

Explanation

Correct Answer: BThe scenario describes a classic indication for Paley Osteotomy Rule Two. The CORA is at an 'un-cuttable' location (the open physis), which must be preserved. Rule Two allows the surgeon to place the hardware hinge (ACA) at the CORA (the physis) to ensure proper axis realignment, but perform the actual osteotomy at a different, surgically accessible and safe level (e.g., the metaphysis). The text states: 'Hinge at the level of the CORA with osteotomy distal (or proximal) to the CORA leads to translation of the bone ends but not of the axis lines.' This results in a planned translation at the osteotomy site, but the overall mechanical alignment is flawlessly restored.Option A is incorrect because performing an osteotomy directly through an open physis would cause growth arrest. Option C is incorrect because Rule Three is an error that leads to iatrogenic translation and failure of axis realignment. Options D and E misapply the rules and their implications for growth plates.

Question 1167

Topic: 4. Pediatrics

A 25-year-old patient presents with a significant genu varum deformity and a 2 cm limb length discrepancy (shortening) in the affected limb. The surgeon plans a gradual correction using an external fixator. To address both the angular deformity and the limb shortening simultaneously, which hinge placement strategy along the transverse bisector line should be employed?

. A closing wedge osteotomy with the hinge placed over the concave cortex.
. An opening wedge osteotomy with the hinge placed precisely over the convex cortex.
. An angular correction with distraction, where the hinge is placed on the bisector line but more convex than the convex cortex (out in space).
. A neutral hinge placement directly through the center of the bone, irrespective of the bisector line.
. A hinge placement that is distal to the CORA, regardless of the osteotomy site.

Correct Answer & Explanation

. An angular correction with distraction, where the hinge is placed on the bisector line but more convex than the convex cortex (out in space).

Explanation

Correct Answer: CThe patient requires both angular correction and significant lengthening (2 cm). The text describes 'Angular Correction with Distraction' as the method for maximizing lengthening: 'By moving the hinge away from the bone, the convex cortex no longer acts as a simple pivot. Instead, both the convex and concave cortices are distracted apart during the angular correction. Effect on Length: This createssignificant lengtheningand prevents premature consolidation at the convex side... Indication: This is the preferred Ilizarov method for the gradual correction of large angular deformities combined with substantial limb shortening.' This strategy involves placing the hinge on the bisector line but 'more convex than the convex cortex (out in space).'Option A (closing wedge) would shorten the limb, which is contraindicated here. Option B (opening wedge with hinge on convex cortex) would cause slight lengthening, but not 'significant lengthening' as required for a 2 cm discrepancy. Option D is incorrect as hinge placement must be along the transverse bisector line. Option E describes a hinge placement relative to the CORA, not specifically along the bisector line for length modification.

Question 1168

Topic: 4. Pediatrics

The introduction to Paley's Principles of Deformity Correction emphasizes that before his methodologies, deformity correction was often an 'empirical, "eyeball" science fraught with unpredictable outcomes and iatrogenic errors.' What is the primary advantage offered by Paley's systemized, mathematical framework for orthopedic surgeons?

. It eliminates the need for extensive preoperative radiographic imaging.
. It allows for faster surgical procedures due to standardized steps.
. It provides a reproducible, quantitative system for analysis and planning, leading to predictable, high-precision corrections.
. It primarily focuses on non-surgical management of limb deformities.
. It simplifies the selection of surgical hardware, making all options equally effective.

Correct Answer & Explanation

. It provides a reproducible, quantitative system for analysis and planning, leading to predictable, high-precision corrections.

Explanation

Correct Answer: CThe text highlights that 'Before Paley's methodologies became the global standard, deformity correction was often an empirical, "eyeball" science fraught with unpredictable outcomes and iatrogenic errors. Today, Paley's Principles of Deformity Correction provide a reproducible, mathematical framework for tackling even the most complex congenital, post-traumatic, or developmental limb abnormalities.' This framework allows surgeons to describe, analyze, and plan for deformities in a standardized, quantitative way, leading to predictable and precise corrections.Option A is incorrect; Paley's methods heavily rely on meticulous preoperative radiographic imaging (e.g., full-length standing AP radiographs). Option B is incorrect; while standardization can improve efficiency, the primary advantage is precision and predictability, not necessarily speed. Option D is incorrect; Paley's principles are fundamentally about surgical correction. Option E is incorrect; the text mentions strategic selection of hardware, implying that selection is critical and not simplified to 'all options equally effective.'

Question 1169

Topic: 4. Pediatrics

A 4-year-old girl has a congenital short femur resulting in a current limb length discrepancy of 3 cm. The surgeon uses the Paley multiplier method to predict her discrepancy at skeletal maturity.

What is the fundamental mathematical principle behind the Paley multiplier method for limb length prediction?

. The growth of the shorter limb decelerates exponentially with age.
. The proportion of the child's current limb length to mature limb length is independent of the child's gender.
. The ratio of limb length at any given age to limb length at maturity is a constant for that specific age and gender.
. Growth arrest occurs symmetrically in both limbs after menarche.
. Congenital deformities grow at a fixed, predictable rate of 1 mm per month.

Correct Answer & Explanation

. The ratio of limb length at any given age to limb length at maturity is a constant for that specific age and gender.

Explanation

The Paley multiplier method is based on the principle that the ratio of a child's limb length at a given age to their final length at maturity is a constant value. These multipliers are specific to the patient's age and gender.

Question 1170

Topic: 4. Pediatrics

When using a circular external fixator (e.g., Ilizarov or Taylor Spatial Frame) to correct a deformity, placing the mechanical hinge exactly at the CORA anatomically corresponds to matching the hinge with which theoretical concept?

. The Mechanical Axis Deviation (MAD)
. The Axis of Correction of Angulation (ACA)
. The Center of Rotation of Translation (CORT)
. The Anatomical Axis of the Diaphysis
. The Joint Orientation Line

Correct Answer & Explanation

. The Axis of Correction of Angulation (ACA)

Explanation

In circular frame mechanics, the hinge precisely represents the Axis of Correction of Angulation (ACA). Placing the hinge at the CORA fulfills Paley's Rule 1, allowing pure angular correction without unintended translation.

Question 1171

Topic: 4. Pediatrics

A 5-year-old child presents with a progressive Trendelenburg gait. Radiographs reveal significant coxa vara, characterized by a reduced neck-shaft angle. Based on the principles of lever arm dysfunction discussed in the case, the primary biomechanical reason for this child's gait abnormality is:

. Increased intrinsic power generation by the gluteus medius muscle.
. Pathologic alteration in the fulcrum position of the hip joint.
. A significantly shortened abductor muscle lever arm.
. Excessive load placed on the hip joint due to increased body weight.
. Reduced effort required by the abductor muscles to stabilize the pelvis.

Correct Answer & Explanation

. A significantly shortened abductor muscle lever arm.

Explanation

Correct Answer: CThe case specifically uses coxa vara as a 'classic example of a dynamic deformity caused by lever arm dysfunction.' It states, 'In both of these structural anomalies [severe femoral anteversion or coxa vara], the length of the abductor muscle lever arm is significantly shortened. Because the lever arm is reduced, the abductor muscles (the effort) must generate a massively increased force to stabilize the pelvis (the load) over the hip joint (the fulcrum) during the single-leg stance phase of gait. This leads to rapid abductor fatigue, dysfunction, and the classic compensatory Trendelenburg gait.' Therefore, a significantly shortened abductor muscle lever arm (Option C) is the direct biomechanical cause. Option A is incorrect because the problem is not increased power, but inefficient use of power due to the shortened lever. Option B is incorrect; while the joint is the fulcrum, the primary alteration described is in the lever arm, not the fulcrum's position itself. Option D is not directly supported as the primary cause of lever arm dysfunction. Option E is incorrect as the abductor muscles must generateincreasedforce, not reduced effort.

Question 1172

Topic: 4. Pediatrics

A 10-year-old boy presents with a 3.0 cm limb length discrepancy (LLD) of the right lower extremity due to a congenital growth arrest. He exhibits noticeable vaulting during gait and complains of occasional lower back pain. His parents are concerned about long-term consequences. Based on the LLD severity classification and management strategies outlined in the case, what is the most appropriate initial management strategy for this patient?

. Observation with regular follow-up, as this is a minor discrepancy.
. Prescription of an external shoe lift as the definitive treatment.
. Surgical epiphysiodesis of the contralateral (longer) limb.
. Complex multi-level lengthening using an external fixator.
. Immediate intramedullary lengthening of the shorter limb.

Correct Answer & Explanation

. Surgical epiphysiodesis of the contralateral (longer) limb.

Explanation

Correct Answer: CThe case categorizes LLD severity: 'Moderate (2.0 - 5.0 cm): Measurable gait asymmetry. Vaulting or circumduction present. Increased oxygen consumption during ambulation. High risk of secondary back pain and contralateral joint arthritis over time. Surgical candidates. Often treated with isolated bone lengthening (e.g., magnetic internal lengthening nails) or epiphysiodesis in growing children.' Given the patient is 10 years old (a growing child) and has a 3.0 cm LLD with symptoms (vaulting, back pain), he falls into the 'Moderate' category and is a surgical candidate. Epiphysiodesis of the contralateral limb (Option C) is a common and appropriate treatment for growing children with moderate LLD to equalize limb lengths by slowing growth on the longer side. Option A is incorrect as 3.0 cm is not considered minor and warrants intervention. Option B is a temporary measure and not definitive for a moderate LLD with symptoms and long-term risks. Option D (multi-level lengthening with external fixator) is typically reserved for severe LLD (>5.0 cm). Option E (immediate intramedullary lengthening) is a valid option for lengthening, but epiphysiodesis is also a primary consideration in a growing child and often preferred for this range of discrepancy if growth remains.

Question 1173

Topic: Pediatric Hip

A 42-year-old patient presents with a painful varus knee deformity. A full-length standing radiograph is obtained, and the joint orientation angles are measured as shown in the diagram below. The measured Mechanical Lateral Distal Femoral Angle (mLDFA) is 95°, and the Medial Proximal Tibial Angle (MPTA) is 87°.

Based on Paley's principles and the provided normal values, where is the primary anatomical location of this patient's varus deformity?

. Proximal femur (coxa vara).
. Distal femur.
. Proximal tibia.
. Distal tibia (ankle valgus).
. Intra-articular knee joint.

Correct Answer & Explanation

. Distal femur.

Explanation

Correct Answer: BThe case provides the normal values for Paley's joint orientation angles: mLDFA (Mechanical Lateral Distal Femoral Angle) normal range is 85° to 90° (Avg 87°), and an mLDFA > 90° indicates distal femoral varus. The MPTA (Medial Proximal Tibial Angle) normal range is 85° to 90° (Avg 87°), and an MPTA < 85° indicates proximal tibial varus. In this patient, the mLDFA is 95°, which is significantly greater than 90°, indicating a distal femoral varus deformity. The MPTA is 87°, which falls within the normal range (85°-90°), indicating normal proximal tibial alignment. Therefore, the primary anatomical location of the varus deformity is the distal femur (Option B). Option A (proximal femur) would be indicated by an abnormal mLPFA. Option C (proximal tibia) would be indicated by an abnormal MPTA. Option D (distal tibia) would be indicated by an abnormal LDTA. Option E (intra-articular) would be indicated by an abnormal JLCA, or if both mLDFA and MPTA were normal despite a varus MAD.

Question 1174

Topic: 4. Pediatrics

A 35-year-old patient with a history of cerebral palsy presents with a severe bilateral knee flexion deformity, requiring a crouched gait pattern. Radiographic evaluation reveals normal Posterior Distal Femoral Angles (PDFA = 83°) and normal Posterior Proximal Tibial Angles (PPTA = 81°). Despite these normal bony parameters, the patient has a fixed flexion contracture of 30 degrees bilaterally. Which of the following is the most likely primary etiology of this patient's knee flexion deformity?

. Distal femoral procurvatum
. Proximal tibial procurvatum
. Anterior sagittal mechanical axis deviation
. Posterior soft tissue contracture of the knee
. Ankle equinus deformity

Correct Answer & Explanation

. Posterior soft tissue contracture of the knee

Explanation

Correct Answer: DThe case clearly differentiates between bony deformity and soft tissue contracture. It states that a pure soft tissue contracture involves a completely normal bony geometry (normal PDFA of 83° and normal PPTA of 81°) but a pathological restriction from the soft tissues. The posterior structures of the knee (posterior joint capsule, hamstring tendons, gastrocnemius heads) become shortened and non-compliant, physically blocking extension. This is frequently seen in cerebral palsy, as described in the vignette. Given the normal PDFA and PPTA, bony procurvatum is ruled out, making a posterior soft tissue contracture the most likely primary etiology.Option A is incorrectbecause distal femoral procurvatum is characterized by an increased PDFA (>83°), which is not present in this patient.Option B is incorrectbecause proximal tibial procurvatum is characterized by an increased PPTA (>81°), which is also not present in this patient.Option C is incorrect. Anterior sagittal mechanical axis deviation is aconsequenceof knee flexion deformity, not its primary etiology. It describes the shift of the weight-bearing line due to the flexed posture.Option E is incorrect. While an ankle equinus deformity (plantarflexion contracture) can coexist and worsen a crouched gait, the question asks for the primary etiology of theknee flexion deformity. In this scenario, the normal bony angles point directly to a soft tissue issue at the knee itself, rather than a primary ankle problem causing the knee flexion.

Question 1175

Topic: 4. Pediatrics

Which of the following parameters represents the classic, most widely accepted optimal rate and rhythm for distraction osteogenesis in a healthy adult undergoing limb lengthening?

. 0.25 mm four times a day
. 0.5 mm twice a day
. 1.0 mm once a day
. 2.0 mm twice a day
. 0.5 mm four times a day

Correct Answer & Explanation

. 0.25 mm four times a day

Explanation

The classic Ilizarov principle dictates an optimal distraction rate of 1 mm per day. Dividing this into a rhythm of 0.25 mm four times daily provides optimal conditions for regenerate bone formation and soft tissue adaptation.

Question 1176

Topic: 4. Pediatrics

Modern six-axis circular external fixators (such as the Taylor Spatial Frame) utilize computer software to correct complex, multiplanar deformities simultaneously. These devices rely on which foundational mathematical and engineering principle?

. Pythagorean theorem
. Stewart-Gough platform principle
. Fibonacci sequence geometry
. Ilizarov planar geometry
. Euler's rotation theorem

Correct Answer & Explanation

. Stewart-Gough platform principle

Explanation

Hexapod external fixators are based on the Stewart-Gough platform principle. This mechanism uses six independently adjustable struts to control an object in six degrees of freedom, allowing for simultaneous correction of translation, angulation, and rotation.

Question 1177

Topic: 4. Pediatrics

A 35-year-old male undergoes correction of a multiplanar post-traumatic tibial deformity using a hexapod circular external fixator (e.g., Taylor Spatial Frame). The surgeon inputs the required anteroposterior, lateral, and axial translation and angulation parameters into the software. Which of the following best describes the principle biomechanical advantage of a hexapod frame over a traditional Ilizarov frame in this scenario?

. Elimination of the need for daily pin site care
. Ability to correct six degrees of freedom simultaneously without frame modification
. Increased construct stiffness in axial loading during early consolidation
. Faster biological rate of bone regenerate consolidation
. Reduced risk of neurovascular injury during initial wire placement

Correct Answer & Explanation

. Ability to correct six degrees of freedom simultaneously without frame modification

Explanation

Hexapod external fixators utilize the Stewart-Gough platform principle, allowing simultaneous correction of angulation, translation, and rotation in all planes (six degrees of freedom) by simply adjusting strut lengths via a computer schedule. Traditional Ilizarov frames typically require complex hinge adjustments or physical frame remounting to correct multiplanar deformities.

Question 1178

Topic: 4. Pediatrics

A 9-year-old girl with idiopathic genu valgum undergoes medial femoral hemiepiphysiodesis using a tension band construct (8-plate). Twelve months postoperatively, her mechanical axis has been restored to neutral, and the plates are removed. Which of the following is the most recognized complication following hardware removal in this specific patient population?

. Premature complete physeal closure
. Valgus rebound deformity
. Persistent knee stiffness
. Hardware failure of the retained screws
. Unintentional limb lengthening

Correct Answer & Explanation

. Valgus rebound deformity

Explanation

Rebound growth (returning to the valgus deformity) is a well-documented phenomenon following the removal of tension band plates for guided growth, particularly in younger children with significant remaining growth potential. Surgeons often overcorrect the deformity slightly into mild varus prior to hardware removal to account for this predictable rebound effect.

Question 1179

Topic: 4. Pediatrics
A 12-year-old patient with cerebral palsy presents with a 'recurvatum thrust' during the stance phase of gait, despite having normal Mechanical Posterior Distal Femoral Angle (mPDFA) and Mechanical Posterior Proximal Tibial Angle (mPPTA) measurements. The clinical presentation is analogous to Panel (iii) in the provided diagram.
. Primary osseous deformity of the distal femur
. Isolated rupture of the posterior cruciate ligament (PCL)
. Weak or paralyzed hamstrings leading to progressive attenuation of posterior static restraints
. Quadriceps contracture causing fixed hyperextension
. Primary posterior capsule tear requiring surgical repair

Correct Answer & Explanation

. Weak or paralyzed hamstrings leading to progressive attenuation of posterior static restraints

Explanation

The case content highlights the crucial role of hamstrings: 'They are the primary dynamic guardians against knee hyperextension.' It further explains that in patients with neuromuscular conditions like cerebral palsy, 'this dynamic check-rein is often lost. The knee is driven into hyperextension with every single step. This repetitive micro-trauma gradually attenuates the posterior capsule and cruciate ligaments, ultimately transforming a purely dynamic muscle imbalance into a fixed, static ligamentous laxity.' Panel (iii) of the image specifically illustrates 'Dynamic Recurvatum' due to 'atrophied, weak, or paralyzed hamstrings.' The normal mPDFA and mPPTA rule out a primary osseous deformity.

Question 1180

Topic: 4. Pediatrics

A 35-year-old patient with a history of congenital knee deformity undergoes radiographic evaluation. On a true lateral radiograph, the measured Posterior Distal Femoral Angle (PDFA) is 75°, and the Posterior Proximal Tibial Angle (PPTA) is 86°. Based on Paley's principles and the provided normal values (PDFA 83° ± 4°, PPTA 81° ± 4°), what do these measurements indicate?

. Femoral recurvatum and tibial procurvatum.
. Femoral procurvatum and tibial recurvatum.
. Both femoral and tibial procurvatum.
. Both femoral and tibial recurvatum.
. Normal femoral alignment and tibial recurvatum.

Correct Answer & Explanation

. Femoral procurvatum and tibial recurvatum.

Explanation

Correct Answer: BAccording to the case, a decreased PDFA signifies femoral procurvatum, and an increased PDFA signifies femoral recurvatum. A decreased PPTA signifies tibial procurvatum, and an increased PPTA signifies tibial recurvatum.PDFA:Measured at 75°. Normal range is 83° ± 4° (79° to 87°). Since 75° is less than 79°, this indicates adecreased PDFA, which signifiesfemoral procurvatum.PPTA:Measured at 86°. Normal range is 81° ± 4° (77° to 85°). Since 86° is greater than 85°, this indicates anincreased PPTA, which signifiestibial recurvatum.Therefore, the patient has femoral procurvatum and tibial recurvatum.

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