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4. Pediatrics MCQs

Practice Set 66 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 1301

Topic: 4. Pediatrics

A patient with Blount's disease presents with a complex proximal tibial deformity. Typical three-dimensional analysis of this deformity usually reveals which of the following combinations?

. Varus, internal rotation, and procurvatum.
. Valgus, external rotation, and recurvatum.
. Varus, external rotation, and recurvatum.
. Valgus, internal rotation, and procurvatum.
. Varus, internal rotation, and recurvatum.

Correct Answer & Explanation

. Varus, internal rotation, and procurvatum.

Explanation

Infantile Blount's disease classically produces a three-dimensional proximal tibial deformity characterized by varus angulation, internal tibial torsion, and procurvatum (anterior bowing) due to delayed growth of the posteromedial physis.

Question 1302

Topic: 4. Pediatrics

A patient undergoes bone transport for a 6 cm tibial defect using an Ilizarov frame. The distraction phase is completed successfully. As a general rule, the consolidation phase (time from end of distraction to frame removal) is expected to last how long relative to the distraction phase?

. Half the time of the distraction phase.
. Equal to the time of the distraction phase.
. Twice the time of the distraction phase.
. Three times the time of the distraction phase.
. Four times the time of the distraction phase.

Correct Answer & Explanation

. Twice the time of the distraction phase.

Explanation

The consolidation phase allows the regenerate bone to mineralize and strengthen sufficiently for weight-bearing without the frame. It is generally expected to take roughly twice as long as the distraction phase (a 2:1 ratio).

Question 1303

Topic: 4. Pediatrics

A 14-year-old male is undergoing tibial lengthening via distraction osteogenesis using a circular Ilizarov frame. According to classic Ilizarov principles, what is the optimal rate and rhythm for distraction to promote ideal regenerate bone formation?

. 0.5 mm per day in a single adjustment
. 1.0 mm per day divided into four 0.25 mm increments
. 1.5 mm per day divided into two 0.75 mm increments
. 2.0 mm per day divided into four 0.5 mm increments
. 1.0 mm per day in a single adjustment

Correct Answer & Explanation

. 1.0 mm per day divided into four 0.25 mm increments

Explanation

The classic Ilizarov method utilizes a distraction rate of 1 mm per day, optimally divided into four 0.25 mm increments (rhythm) to provide a steady mechanical stimulus for osteogenesis while protecting surrounding soft tissues.

Question 1304

Topic: 4. Pediatrics

A 45-year-old female undergoes a 6-axis Taylor Spatial Frame (TSF) application for a complex multi-planar tibial deformity. In distraction osteogenesis, what is the standard recommended optimal rate and rhythm of distraction to promote high-quality bone regenerate?

. 1.0 mm per day performed as a single adjustment
. 1.0 mm per day performed in four divided increments of 0.25 mm
. 2.0 mm per day performed in two divided increments of 1.0 mm
. 0.5 mm per day continuous continuous distraction
. 1.5 mm per day performed in three divided increments of 0.5 mm

Correct Answer & Explanation

. 1.0 mm per day performed in four divided increments of 0.25 mm

Explanation

Ilizarov's original research demonstrated that a distraction rate of 1 mm per day is optimal for bone regeneration. Dividing this into smaller increments (e.g., 0.25 mm four times daily) decreases soft tissue tension and improves regenerate quality.

Question 1305

Topic: 4. Pediatrics

When performing a corticotomy for distraction osteogenesis using the Ilizarov technique, preserving the endosteal blood supply and periosteum is crucial for optimal regenerate formation. Which of the following surgical techniques best adheres to these principles?

. Aggressive reaming of the medullary canal followed by oscillating saw osteotomy
. Wide subperiosteal stripping and complete diaphyseal transverse osteotomy with a power saw
. Low-energy corticotomy using multiple small drill holes and a narrow osteotome without violating the medullary canal
. Thermal ablation of the cortex using an uncooled high-speed burr
. Immediate distraction of 5 mm intraoperatively to confirm completion

Correct Answer & Explanation

. Low-energy corticotomy using multiple small drill holes and a narrow osteotome without violating the medullary canal

Explanation

The classic Ilizarov corticotomy relies on a low-energy technique to divide the outer cortex while sparing the endosteal vessels and periosteum. Using multiple drill holes and an osteotome minimizes thermal necrosis and preserves the biological environment for osteogenesis.

Question 1306

Topic: 4. Pediatrics

A patient presents with a 'multi-apical' bow of the femur resulting from osteogenesis imperfecta. When applying Paley's principles to map this deformity, what is the appropriate planning strategy?

. Use a single CORA calculated from the hip center to the ankle center
. Identify the magnitude and independent CORA for each individual deformity apex
. Perform a single distal femoral osteotomy using Rule 3
. Use only translation at a diaphyseal osteotomy to align the mechanical axis
. Correct the entire deformity acutely with intramedullary lengthening nails

Correct Answer & Explanation

. Identify the magnitude and independent CORA for each individual deformity apex

Explanation

For multi-apical (complex) deformities, the mechanical and anatomic axes must be drawn segmentally. A distinct CORA must be identified for each apex of the deformity to plan appropriate multiple osteotomies for anatomic restoration.

Question 1307

Topic: 4. Pediatrics

The Taylor Spatial Frame (TSF) utilizes the principles of a hexapod to allow simultaneous correction in multiple planes. In which of the following clinical scenarios does the TSF offer the most significant mechanical advantage over a traditional classic Ilizarov circular frame?

. Simple isolated mono-planar limb lengthening
. Acute intraoperative correction of a simple angular deformity
. Multi-planar deformity requiring simultaneous correction of angulation, rotation, and translation
. Arthrodesis of the ankle joint in a neutral position
. Stabilization of a fresh transverse diaphyseal tibial fracture

Correct Answer & Explanation

. Multi-planar deformity requiring simultaneous correction of angulation, rotation, and translation

Explanation

The TSF is a 6-axis hexapod external fixator. Its primary advantage over traditional hinged Ilizarov frames is the ability to use software to simultaneously correct complex multi-planar deformities (angulation, translation, rotation, and length) via a single strut adjustment schedule.

Question 1308

Topic: 4. Pediatrics

A 45-year-old man requires bone transport for a 6 cm tibial defect using distraction osteogenesis (Ilizarov method). The surgeon performs a corticotomy and begins distraction. What is the standard recommended rate and rhythm of distraction?

. 0.25 mm per day, divided into 4 increments
. 1.0 mm per day, divided into 4 increments
. 1.5 mm per day, divided into 2 increments
. 2.0 mm per day, performed as a single adjustment
. 1.0 mm per week, divided into 7 increments

Correct Answer & Explanation

. 1.0 mm per day, divided into 4 increments

Explanation

The classic Ilizarov principle for distraction osteogenesis utilizes a rate of 1.0 mm per day, optimally divided into four 0.25 mm increments to ensure adequate bone regeneration while avoiding premature consolidation or nonunion.

Question 1309

Topic: Pediatric Lower Extremity

A 16-year-old male with Blount's disease undergoes correction of a severe proximal tibial deformity.

Based on Paley's principles of oblique plane deformities, if a patient has both a coronal varus deformity and a sagittal apex posterior (procurvatum) deformity, what is the geometric relationship to the true plane of the deformity?

. The true deformity is a pure translational shift in the axial plane
. The true deformity lies in a single oblique plane located somewhere between the coronal and sagittal planes
. The true deformity is exclusively rotational and requires a transverse derotational osteotomy
. There are always two distinct CORAs that cannot be corrected by a single osteotomy
. The maximum angulation occurs at an orientation exactly 90 degrees to the oblique plane

Correct Answer & Explanation

. The true deformity lies in a single oblique plane located somewhere between the coronal and sagittal planes

Explanation

A combined angulation in orthogonal planes (e.g., coronal varus and sagittal procurvatum) actually represents a single angular deformity occurring in a single oblique plane. It can be corrected mathematically with a single appropriately aligned hinge or spatial frame.

Question 1310

Topic: 4. Pediatrics

A 14-year-old female presents with a 4 cm true leg length discrepancy secondary to physeal arrest, without any angular deformity. Lengthening Over a Nail (LON) is planned. What is the primary advantage of LON compared to classic Ilizarov external fixation lengthening?

. Decreased risk of deep intramedullary infection
. Shorter duration of external fixator wear
. Elimination of the need for an osteotomy or corticotomy
. Ability to adjust residual angular deformities during the consolidation phase
. Lower cost of the implants

Correct Answer & Explanation

. Shorter duration of external fixator wear

Explanation

The primary advantage of Lengthening Over a Nail (LON) is that the external fixator can be removed immediately at the end of the distraction phase once the nail is statically locked. This drastically reduces the time the patient must wear the external frame.

Question 1311

Topic: 4. Pediatrics

The concept of "tension-stress" in the regeneration of bone and soft tissue was extensively studied and popularized by Gavriil Ilizarov. Which of the following parameters is considered the optimal rhythm for bone distraction to maximize the tension-stress effect?

. 1.0 mm distraction performed once daily.
. 0.5 mm distraction performed twice daily.
. 0.25 mm distraction performed four times daily.
. 2.0 mm distraction performed once every other day.
. 0.1 mm distraction performed ten times daily via an automated continuous distracter.

Correct Answer & Explanation

. 0.25 mm distraction performed four times daily.

Explanation

Ilizarov demonstrated that high-frequency, small-increment distraction provides the best biologic regenerate. The clinical gold standard for rhythm is 0.25 mm four times a day, totaling 1.0 mm per day, balancing bone formation with soft tissue tolerance.

Question 1312

Topic: Pediatric Upper Extremity & Spine

A surgeon is evaluating a post-traumatic supracondylar femoral malunion. The Lateral Distal Femoral Angle (mLDFA) is measured using the mechanical axis of the femur. If the surgeon decides to use the anatomic axis of the femur instead to calculate the distal femoral joint orientation, what is the corresponding normal anatomic angle (aLDFA)?

. 87 degrees
. 81 degrees
. 93 degrees
. 99 degrees
. 75 degrees

Correct Answer & Explanation

. 87 degrees

Explanation

The normal mechanical LDFA (mLDFA) is approximately 87 degrees. Because the anatomic axis of the femur is in about 7 degrees of valgus relative to the mechanical axis, the normal anatomic LDFA (aLDFA) is approximately 81 degrees (87 - 6 to 7 degrees).

Question 1313

Topic: 4. Pediatrics

A 12-year-old girl with a congenital femoral deficiency has a severe valgus deformity and limb length discrepancy.

When utilizing the anatomical axis for preoperative planning of the femur, the surgeon must account for its normal relationship to the mechanical axis. What is the normal angle between the anatomical and mechanical axes of the femur?

. 0 degrees
. 2-3 degrees
. 5-7 degrees
. 9-11 degrees
. 13-15 degrees

Correct Answer & Explanation

. 5-7 degrees

Explanation

The normal angle between the femoral mechanical axis (center of hip to center of knee) and the femoral anatomical axis (piriformis fossa down the medullary canal) is typically 5 to 7 degrees.

Question 1314

Topic: 4. Pediatrics

According to Ilizarov's principles of distraction osteogenesis for deformity correction and lengthening, what is the most optimal rate and rhythm of distraction to promote regenerate bone formation while avoiding premature consolidation or nonunion?

. 0.5 mm per day in a single adjustment
. 1.0 mm per day divided into four 0.25 mm increments
. 1.5 mm per day divided into three 0.5 mm increments
. 2.0 mm per day divided into two 1.0 mm increments
. 1.0 mm per day in a single adjustment

Correct Answer & Explanation

. 1.0 mm per day divided into four 0.25 mm increments

Explanation

Ilizarov established that a rate of 1.0 mm per day is optimal. High-frequency rhythms (e.g., 0.25 mm four times daily) provide a more constant tension on the tissues, promoting better regenerate formation and minimizing soft tissue complications.

Question 1315

Topic: 4. Pediatrics

To maximize the axial stiffness of a circular external fixator (Ilizarov frame) during a complex deformity correction, which of the following modifications is most effective?

. Increasing the ring diameter
. Decreasing the wire tension
. Decreasing the ring diameter and increasing wire diameter
. Increasing the distance between the bone and the ring
. Using single-level wire fixation instead of two-level

Correct Answer & Explanation

. Decreasing the ring diameter and increasing wire diameter

Explanation

Frame stability and axial stiffness in circular fixators are significantly increased by using smaller diameter rings (bringing the ring closer to the bone), increasing wire diameter, and increasing wire tension.

Question 1316

Topic: 4. Pediatrics

A 10-year-old child presents with a valgus deformity of the left knee. The surgeon opts for guided growth utilizing a tension band plate (eight-Plate) on the medial distal femur. Which of the following laws best describes the principle governing this deformity correction?

. Wolff's Law
. Hueter-Volkmann Law
. Hilton's Law
. Heuter's Law
. Davis's Law

Correct Answer & Explanation

. Hueter-Volkmann Law

Explanation

The Hueter-Volkmann Law states that increased mechanical compression across a physis decreases longitudinal growth, while decreased compression stimulates it. Guided growth mechanically tethers one side of the physis, modulating growth to correct the deformity.

Question 1317

Topic: 4. Pediatrics

During distraction osteogenesis for a post-traumatic tibial length discrepancy using an Ilizarov frame, a patient asks about the optimal timing to begin lengthening after the corticotomy. What is the standard recommended latent period for a healthy adult metaphyseal corticotomy?

. 1 to 3 days
. 5 to 7 days
. 10 to 14 days
. 14 to 21 days
. 21 to 28 days

Correct Answer & Explanation

. 5 to 7 days

Explanation

A latent period of 5 to 7 days is generally recommended before beginning distraction to allow the initial phase of fracture healing and optimal regenerate bone formation.

Question 1318

Topic: Pediatric Lower Extremity

A 10-year-old girl is noted to have a significant leg length discrepancy. Radiographs reveal anteromedial bowing of the shortened tibia, a deficient lateral malleolus, and an absent 5th ray of the foot. What is the most likely underlying diagnosis?

. Congenital pseudarthrosis of the tibia
. Proximal focal femoral deficiency
. Tibial hemimelia
. Fibular hemimelia
. Posteromedial bowing of the tibia

Correct Answer & Explanation

. Fibular hemimelia

Explanation

Fibular hemimelia is classically associated with an anteromedial tibial bow, an equinovalgus foot with absent lateral rays, and a deficient or absent fibula.

Question 1319

Topic: 4. Pediatrics

What is the primary mechanical advantage of the tensioned fine wires used in the Ilizarov circular external fixator compared to traditional large-diameter half-pins?

. They provide absolute rigidity, completely preventing any micromotion
. They allow for controlled axial micromotion while maintaining high bending and torsional stiffness
. They eliminate the risk of pin tract infections
. They do not cross the anatomical axis of the bone
. They are primarily used to compress the fracture rather than distract

Correct Answer & Explanation

. They allow for controlled axial micromotion while maintaining high bending and torsional stiffness

Explanation

Tensioned fine wires provide a "trampoline effect," offering high bending and torsional stiffness while permitting axial micromotion. This specific mechanical environment stimulates robust bone regenerate formation in distraction osteogenesis.

Question 1320

Topic: 4. Pediatrics

A child with congenital pseudarthrosis of the tibia (CPT) undergoes resection of the pseudarthrosis and bone transport. What systemic condition is most classically associated with this specific tibial deformity?

. Achondroplasia
. Neurofibromatosis type 1
. Osteogenesis imperfecta
. Marfan syndrome
. Multiple hereditary exostoses

Correct Answer & Explanation

. Neurofibromatosis type 1

Explanation

Congenital pseudarthrosis of the tibia (CPT) is strongly associated with Neurofibromatosis type 1 (NF1). It typically presents with anterolateral bowing of the tibia that spontaneously fractures and fails to heal.

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