Menu

1. General Principles & Basic Science MCQs

Practice Set 473 of 789

This practice set contains high-yield board review questions covering key concepts in 1. General Principles & Basic Science. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 9441

Topic: 1. General Principles & Basic Science

Which of the following demographic profiles is most consistent with the typical presentation of Dysplasia Epiphysealis Hemimelica?

. Adolescent females aged 12-16
. Young male children aged 2-8
. Elderly males over 65
. Middle-aged females aged 40-50
. Neonates of both sexes

Correct Answer & Explanation

. Young male children aged 2-8

Explanation

DEH primarily presents in early childhood, typically between the ages of 2 and 8 years. It also has a marked male predominance, with a male-to-female ratio of roughly 3:1.

Question 9442

Topic: 1. General Principles & Basic Science

A 5-year-old girl is diagnosed with Dysplasia Epiphysealis Hemimelica (DEH) of the medial distal tibia after a painless, hard bump was noted by her parents. Clinical examination reveals a mild varus deformity of 5 degrees, but she is completely asymptomatic with full, unrestricted range of motion. What is the most appropriate initial management for this patient?

. Observation with regular clinical and radiographic follow-up
. Immediate complete surgical excision of the mass
. Prophylactic epiphysiodesis of the distal tibia
. Corrective closing wedge osteotomy
. Intra-articular corticosteroid injections

Correct Answer & Explanation

. Observation with regular clinical and radiographic follow-up

Explanation

Asymptomatic DEH lesions that do not cause mechanical blocks or severe, progressive deformities are best managed with observation. Surgical excision is generally reserved for symptomatic patients with pain, mechanical impingement, or progressive joint deformity, as early surgery carries significant risks.

Question 9443

Topic: 1. General Principles & Basic Science

When correcting a lower extremity diaphyseal angular deformity, what is the biomechanical consequence of performing an opening wedge osteotomy at a level proximal to the Center of Rotation of Angulation (CORA), while maintaining the Axis of Correction of Angulation (ACA) at the osteotomy site?

. Pure angulation without mechanical axis translation
. Translation of the mechanical axis
. Overlengthening of the limb by a factor of 2
. Medialization of the joint line without angulation
. Loss of joint congruence in the sagittal plane

Correct Answer & Explanation

. Translation of the mechanical axis

Explanation

According to Paley's rules of deformity correction, if the osteotomy and the ACA are at a level different from the CORA, correcting the angulation will inevitably result in translation of the mechanical axis. This produces a secondary translational deformity.

Question 9444

Topic: 1. General Principles & Basic Science



A 45-year-old patient is undergoing correction of a diaphyseal tibial angular deformity. The surgeon plans an osteotomy at a level distant from the Center of Rotation of Angulation (CORA). According to the principles of deformity correction, what is the inevitable geometric consequence of fully realigning the mechanical axis with this technique?

. The bone ends will align perfectly without any translation.
. The bone ends must translate to achieve mechanical axis alignment.
. A rotational deformity will inadvertently be created.
. The anatomical axis will align, but the mechanical axis will remain deviated.
. An opening wedge must be used rather than a closing wedge.

Correct Answer & Explanation

. The bone ends must translate to achieve mechanical axis alignment.

Explanation

According to Paley's Rule 2 of osteotomies, if the osteotomy is performed at a level different from the CORA, the mechanical and anatomical axes can only be realigned by introducing translation at the osteotomy site. Failure to translate will result in a residual mechanical axis deviation.

Question 9445

Topic: Biomechanics & Biomaterials

A surgeon is performing a medial opening wedge high tibial osteotomy (HTO) for a 40-year-old active male with medial compartment osteoarthritis and varus alignment. To prevent altering the patient's sagittal plane kinematics, how should the anterior gap compare to the posterior gap at the osteotomy site?

. The anterior gap should be strictly equal to the posterior gap.
. The anterior gap should be roughly half the size of the posterior gap.
. The anterior gap should be roughly twice the size of the posterior gap.
. The osteotomy should only be opened anteriorly.
. The posterior gap should be completely closed.

Correct Answer & Explanation

. The anterior gap should be roughly half the size of the posterior gap.

Explanation

Due to the triangular shape of the proximal tibia, opening the anterior and posterior gaps equally during a medial opening wedge HTO inappropriately increases the posterior tibial slope. To maintain the native posterior slope, the anterior gap must be roughly half the height of the posterior gap.

Question 9446

Topic: Biology, Genetics & Bone Healing

A patient undergoes distraction osteogenesis using an Ilizarov frame. Six weeks post-operatively, radiographs show a lucent zone in the regenerate without evidence of bridging callus. The distraction rate is 1.0 mm per day. What is the most appropriate management for this delayed consolidation?

. Increase the rate of distraction to 1.5 mm per day.
. Remove the external fixator and apply a walking cast.
. Perform an accordion maneuver (alternating compression and distraction).
. Perform a second corticotomy at a different level.
. Administer systemic bisphosphonates immediately.

Correct Answer & Explanation

. Perform an accordion maneuver (alternating compression and distraction).

Explanation

Delayed consolidation or poor regenerate during distraction osteogenesis can be stimulated by the "accordion maneuver," which involves sequential cycles of compression and distraction to stimulate osteogenesis at the regenerate site.

Question 9447

Topic: Infection, Pharmacology & VTE

During a TKA for a severe varus deformity, the medial compartment remains tight in full extension but is well balanced in flexion. Which structure should be incrementally released next to specifically address the tight extension gap?

. Anterior medial collateral ligament
. Posteromedial capsule
. Pes anserinus
. Lateral collateral ligament
. Popliteus tendon

Correct Answer & Explanation

. Posteromedial capsule

Explanation

The posteromedial capsule acts as a primary secondary stabilizer in extension. Releasing the posteromedial capsule selectively opens the tight medial compartment in extension without significantly affecting the flexion gap.

Question 9448

Topic: 1. General Principles & Basic Science

A patient undergoes a medial closing wedge distal femoral osteotomy (DFO) for a valgus deformity. Which of the following is an expected biomechanical consequence of this specific procedure compared to a lateral opening wedge DFO?

. Increase in overall limb length
. Decrease in overall limb length
. Increased risk of peroneal nerve stretch injury
. Significant increase in the Q-angle
. Creation of an iatrogenic valgus alignment

Correct Answer & Explanation

. Decrease in overall limb length

Explanation

A medial closing wedge DFO intrinsically shortens the limb due to the removal of a wedge of bone. Conversely, a lateral opening wedge osteotomy lengthens the limb and carries a higher risk of stretching the common peroneal nerve.

Question 9449

Topic: 1. General Principles & Basic Science

In deformity correction planning, the Center of Rotation of Angulation (CORA) is determined by the intersection of the proximal and distal anatomical axes. If an osteotomy and hinge are placed exactly at the CORA, what is the biomechanical result during angular correction?

. Pure angulation without translation
. Angulation with secondary translation
. Lengthening of the mechanical axis
. Shortening of the mechanical axis
. Medialization of the mechanical axis deviation

Correct Answer & Explanation

. Pure angulation without translation

Explanation

Placing the osteotomy and the hinge exactly at the CORA allows for pure angular correction of the deformity. If the hinge is moved away from the CORA, secondary translation will inevitably occur during the correction.

Question 9450

Topic: 1. General Principles & Basic Science
Which of the following frame modifications will most effectively INCREASE the axial stability of a circular external fixator applied to the tibia?
. Increasing the distance between the bone and the ring
. Decreasing the diameter of the half-pins
. Using standard wires instead of olive wires
. Decreasing the ring diameter
. Decreasing the tension on the transfixing wires

Correct Answer & Explanation

. Decreasing the ring diameter

Explanation

Decreasing the ring diameter reduces the working length of the transfixing wires, significantly increasing the stiffness and axial stability of the frame construct. Increased wire tension and larger pin diameters also increase stability.

Question 9451

Topic: 1. General Principles & Basic Science

According to Paley's rules of deformity correction, if an osteotomy is performed at a level different from the Center of Rotation of Angulation (CORA) but the hinge is placed exactly at the CORA (Rule 2), what is the expected outcome?

. The mechanical axis will be completely realigned without any translation at the osteotomy site.
. The mechanical axis will be realigned, but translation will occur at the osteotomy site.
. The mechanical axis will remain unaligned and perfectly parallel to its original position.
. A secondary angular deformity will be created at the osteotomy site.
. The mechanical axis will shift significantly, requiring a second osteotomy.

Correct Answer & Explanation

. The mechanical axis will be realigned, but translation will occur at the osteotomy site.

Explanation

Paley's Rule 2 states that if the osteotomy is outside the CORA but the hinge axis is at the CORA, the mechanical axes will align collinearly, but translation of the bone ends will unavoidably occur at the osteotomy site.

Question 9452

Topic: 1. General Principles & Basic Science

According to the principles of deformity correction, if the Axis of Correction of Angulation (ACA) and the osteotomy are both located away from the Center of Rotation of Angulation (CORA), what is the resultant biomechanical effect on the mechanical axis after angular correction?

. The mechanical axis will be fully restored without translation.
. The mechanical axis will remain uncorrected and parallel to its original path.
. The mechanical axis lines will be parallel but translated.
. The deformity will undergo pure rotational correction.
. The bone ends will align anatomically but the mechanical axis will deviate into severe valgus.

Correct Answer & Explanation

. The mechanical axis lines will be parallel but translated.

Explanation

Paley's Rule 3 states that if both the ACA and osteotomy are away from the CORA, angular correction will result in parallel but translated mechanical axis lines. This leaves an ongoing mechanical axis deviation (MAD) despite restoring joint orientation.

Question 9453

Topic: 1. General Principles & Basic Science

When performing an osteotomy to correct a tibial deformity, the surgeon places the osteotomy and the Axis of Correction of Angulation (ACA) at a level distant from the Center of Rotation of Angulation (CORA). According to Paley's rules, what is the expected geometric outcome?

. Pure angulation without translation
. Angulation combined with translation of the mechanical axis
. Pure translation without angulation
. Lengthening without translation
. Pure axial rotation

Correct Answer & Explanation

. Angulation combined with translation of the mechanical axis

Explanation

According to Paley's Rule 3, if the osteotomy and the ACA are placed at a level separate from the CORA, the mechanical axis will undergo both angulation and translation. This often results in a secondary translation deformity.

Question 9454

Topic: 1. General Principles & Basic Science

When programming a six-axis hexapod frame for complex lower extremity deformity correction, which of the following represents a strictly defined "mounting parameter"?

. The distance from the CORA to the distal joint line
. The location of the reference ring relative to the origin of the reference bone segment
. The magnitude of the acute translation at the osteotomy
. The Joint Line Convergence Angle
. The desired daily distraction rate

Correct Answer & Explanation

. The location of the reference ring relative to the origin of the reference bone segment

Explanation

Mounting parameters tell the software exactly where the hardware (the reference ring) is located in space relative to the anatomic origin of the reference bone segment. This is critical for the software to calculate the correct strut lengths.

Question 9455

Topic: 1. General Principles & Basic Science

A 40-year-old male presents with a symptomatic diaphyseal varus deformity of the tibia.

Surgical planning dictates that an osteotomy will be performed exactly at the Center of Rotation of Angulation (CORA). To avoid any translational displacement of the mechanical axis, the Axis of Correction of Angulation (ACA) is placed directly on the convex cortex of the deformity. Which of the following correctly describes the resulting geometric correction?

. An opening wedge osteotomy achieving pure angular correction.
. A closing wedge osteotomy achieving pure angular correction.
. An opening wedge osteotomy with an obligatory lengthening effect.
. A neutral wedge osteotomy resulting in simultaneous lateral translation.
. A closing wedge osteotomy resulting in medial translation.

Correct Answer & Explanation

. A closing wedge osteotomy achieving pure angular correction.

Explanation

According to Paley's osteotomy rules, when the osteotomy and ACA are both located at the CORA, pure angular correction without translation is achieved. Placing the ACA on the convex cortex inherently dictates a closing wedge technique, whereas an ACA on the concave cortex requires an opening wedge.

Question 9456

Topic: 1. General Principles & Basic Science

When correcting a multi-apical tibial deformity, the surgeon plans an osteotomy at a site anatomically distant from the Center of Rotation of Angulation (CORA) but places the Axis of Correction of Angulation (ACA) exactly at the CORA. Which of the following best describes the resulting alignment?

. Complete angular correction with no translation at the osteotomy site
. Complete angular correction with translation at the osteotomy site
. Incomplete angular correction with an induced secondary angular deformity
. Overcorrection of the mechanical axis deviation (MAD)
. Translation without any angular correction

Correct Answer & Explanation

. Complete angular correction with translation at the osteotomy site

Explanation

According to Paley's osteotomy rule 2, if the osteotomy is placed away from the CORA but the ACA is maintained at the CORA, the mechanical axes will realign perfectly, but the bone ends will translate at the osteotomy site.

Question 9457

Topic: 1. General Principles & Basic Science

According to Paley's principles of deformity correction, how is the Center of Rotation of Angulation (CORA) geometrically defined on an anteroposterior radiograph of a deformed long bone?

. The intersection of the anatomical axis of the proximal segment and the mechanical axis of the distal segment
. The midpoint of the diaphyseal angular deformity on the concave side
. The intersection of the mechanical or anatomical axes of the proximal and distal bone segments
. The center of the joint closest to the deformity
. The point of maximum cortical thickening on the convex side

Correct Answer & Explanation

. The intersection of the mechanical or anatomical axes of the proximal and distal bone segments

Explanation

The CORA represents the apex of the deformity. It is identified by the intersection of the longitudinal axes (either anatomical or mechanical) of the bone segments proximal and distal to the deformity.

Question 9458

Topic: 1. General Principles & Basic Science

In the principles of lower extremity deformity correction, if the Axis of Correction of Angulation (ACA) is placed at a different level than the Center of Rotation of Angulation (CORA), what is the inevitable geometric consequence?

. Pure angulation without translation
. Translation of the mechanical axis without angulation
. Angulation accompanied by iatrogenic translation of the bone segments
. Joint line obliquity with a perfectly restored mechanical axis
. Limb lengthening without any alteration to the mechanical axis

Correct Answer & Explanation

. Angulation accompanied by iatrogenic translation of the bone segments

Explanation

If the ACA is placed at a site other than the CORA (Paley's Rule 2), correction of the angular deformity will induce a translational deformity. To achieve pure angular correction, the ACA must pass directly through the CORA.

Question 9459

Topic: 1. General Principles & Basic Science

A 50-year-old male undergoes a medial opening wedge high tibial osteotomy (HTO) for isolated medial compartment osteoarthritis. If the osteotomy gap is opened equally at the anterior and posterior cortices, what unintended biomechanical change is most likely to occur?

. Decreased posterior tibial slope
. Increased posterior tibial slope
. Lateralization of the tibial tubercle
. Medialization of the mechanical axis
. Patella alta

Correct Answer & Explanation

. Increased posterior tibial slope

Explanation

The proximal tibia has a triangular cross-section that is narrower anteriorly. Opening an HTO gap equally anteriorly and posteriorly disproportionately distracts the anterior aspect, which inadvertently increases the posterior tibial slope.

Question 9460

Topic: 1. General Principles & Basic Science

A patient with a severe proximal tibial varus deformity requires an extra-articular osteotomy. The Center of Rotation of Angulation (CORA) is located in the proximal metaphysis. If a dome osteotomy is performed with the Axis of Correction of Angulation (ACA) perfectly aligning with the CORA, what is the geometric result?

. The fragments translate medially by half the shaft diameter
. The fragments separate significantly, requiring structural bone graft
. The fragments angulate without translation, maintaining optimal bony contact
. The distal segment translates laterally, leading to mechanical axis deviation
. The overall limb length shortens by the exact width of the saw blade

Correct Answer & Explanation

. The fragments angulate without translation, maintaining optimal bony contact

Explanation

A dome (cylindrical) osteotomy centered perfectly on the CORA adheres to Paley's Rule 1. This allows pure angular correction around the ACA without any translation, while the curved cut maintains excellent bony apposition for healing.

Test Yourself

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

On this Page