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1. General Principles & Basic Science MCQs

Practice Set 768 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 15341

Topic: 1. General Principles & Basic Science

A 14-year-old boy is diagnosed with multiple hereditary exostoses (MHE). What is the normal physiological function of the proteins encoded by the genes most commonly mutated in this condition?

. Synthesis of heparan sulfate
. Regulation of the parathyroid hormone-related protein (PTHrP) receptor
. Degradation of type II collagen
. Inhibition of beta-catenin signaling
. Vascular endothelial growth factor (VEGF) receptor activation

Correct Answer & Explanation

. Synthesis of heparan sulfate

Explanation

MHE is primarily caused by autosomal dominant mutations in the EXT1 or EXT2 genes. These genes encode glycosyltransferases that are essential for the synthesis of heparan sulfate, which regulates normal chondrocyte proliferation and maturation.

Question 15342

Topic: 1. General Principles & Basic Science

When planning a deformity correction, an osteotomy is performed at a level different from the center of rotation of angulation (CORA), but the mechanical axis is aligned using the CORA as the hinge point. What is the expected geometric outcome according to established osteotomy rules?

. Pure angulation without translation.
. Angulation with translation.
. Pure translation.
. Shortening without angulation.
. Lengthening without translation.

Correct Answer & Explanation

. Angulation with translation.

Explanation

According to Paley's Osteotomy Rule 2, if the osteotomy and the hinge are at different levels but the hinge is placed directly on the CORA, the correction will result in both angulation and translation at the osteotomy site. This achieves a straight mechanical axis but with an intentional structural step-off.

Question 15343

Topic: Infection, Pharmacology & VTE

During a primary total knee arthroplasty in a patient with a severe, unyielding 20-degree varus deformity, what is the widely accepted standard sequence for sequential medial soft tissue release?

. Deep MCL, posteromedial capsule, superficial MCL, pes anserinus.
. Superficial MCL, pes anserinus, deep MCL.
. Deep MCL, semimembranosus, superficial MCL, pes anserinus.
. Posteromedial capsule, pes anserinus, deep MCL.
. Pes anserinus, deep MCL, superficial MCL.

Correct Answer & Explanation

. Deep MCL, posteromedial capsule, superficial MCL, pes anserinus.

Explanation

The standard sequence for a medial soft tissue release in a varus TKA begins with the deep MCL. This is followed sequentially by the posteromedial capsule (and semimembranosus), the superficial MCL (periosteal sleeve release), and finally the pes anserinus if severe contracture persists.

Question 15344

Topic: Surgical Anatomy & Approaches

A surgeon is performing a primary total hip arthroplasty using the direct anterior approach (Smith-Petersen). The superficial internervous plane lies between which two muscles?

. Tensor fasciae latae and Gluteus medius
. Sartorius and Tensor fasciae latae
. Rectus femoris and Gluteus minimus
. Adductor longus and Pectineus
. Gluteus maximus and Tensor fasciae latae

Correct Answer & Explanation

. Sartorius and Tensor fasciae latae

Explanation

The superficial interval in the direct anterior approach to the hip is between the sartorius (innervated by the femoral nerve) and the tensor fasciae latae (innervated by the superior gluteal nerve).

Question 15345

Topic: 1. General Principles & Basic Science

In deformity correction principles, 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, what is the geometric result of the correction?

. Pure angulation without translation
. Angulation with translation, resulting in collinear mechanical axes
. Pure translation without angulation
. Angulation with translation, resulting in parallel but non-collinear axes
. Opening wedge correction without translation

Correct Answer & Explanation

. Angulation with translation, resulting in collinear mechanical axes

Explanation

Placing the hinge at the CORA always restores collinearity of the axes. If the osteotomy is at a different level than the CORA, correction will result in both angulation and simultaneous translation at the osteotomy site.

Question 15346

Topic: Biology, Genetics & Bone Healing

In distraction osteogenesis of the tibia, what is the primary physiological rationale for maintaining a latency period of 7 to 10 days prior to initiating distraction?

. To allow for complete resolution of soft tissue edema
. To facilitate the primary inflammatory phase and initial revascularization of the hematoma
. To ensure the osteotomy gap is filled with woven bone
. To permit early mobilization of the adjacent joints
. To minimize the risk of premature consolidation

Correct Answer & Explanation

. To facilitate the primary inflammatory phase and initial revascularization of the hematoma

Explanation

A latency period of 7-10 days allows the initial fracture hematoma to revascularize and multipotent stem cells to populate the osteotomy gap. Distracting too early disrupts this fragile neovascular network, leading to poor regenerate formation and delayed union.

Question 15347

Topic: 1. General Principles & Basic Science

When planning an opening wedge osteotomy to correct an angular deformity, placing the hinge on the convex cortex precisely at the level of the Center of Rotation of Angulation (CORA) will result in:

. A pure opening wedge correction without altering limb length
. An opening wedge correction that concurrently lengthens the mechanical axis
. An opening wedge correction that shortens the mechanical axis
. Translation of the distal segment without lengthening
. Simultaneous opening and closing wedges (neutral wedge)

Correct Answer & Explanation

. An opening wedge correction that concurrently lengthens the mechanical axis

Explanation

Placing the hinge on the convex cortex at the CORA produces an opening wedge osteotomy. Because bone is strictly added to the concave side without removal, this geometric maneuver inherently results in a net lengthening of the limb segment.

Question 15348

Topic: 1. General Principles & Basic Science

When utilizing a hexapod external fixator (e.g., Taylor Spatial Frame) for deformity correction, the concept of 'chronic' parameters primarily refers to:

. The duration the patient has had the deformity prior to surgery
. The daily rate and rhythm of strut adjustments
. The spatial relationship between the reference ring and the reference bone segment
. The location of the osteotomy relative to the frame
. The soft tissue tension limits during correction

Correct Answer & Explanation

. The spatial relationship between the reference ring and the reference bone segment

Explanation

In hexapod circular fixation, 'chronic' (or mounting) parameters define the precise spatial relationship between the reference ring (usually the proximal ring) and its attached reference bone segment in the coronal, sagittal, and axial planes.

Question 15349

Topic: 1. General Principles & Basic Science

According to Paley's osteotomy rules, if the osteotomy and the hinge of the correction are both located at the Center of Rotation of Angulation (CORA), what is the resultant effect on the mechanical axis?

. Angulation with translation
. Pure angulation without translation
. Translation without angulation
. Secondary deformity induction
. Lengthening without angulation

Correct Answer & Explanation

. Pure angulation without translation

Explanation

Paley's Rule 1 states that if the osteotomy passes through the CORA and the hinge is at the CORA, correction results in pure angulation without translation. This perfectly realigns the bone segments without inducing secondary deformities.

Question 15350

Topic: 1. General Principles & Basic Science



When planning a deformity correction, if the osteotomy is performed at a level different from the CORA but the hinge remains exactly at the CORA, what is the expected outcome according to Paley's Rule 2?

. Pure angulation without translation
. Angulation with translation of the bone ends
. Creation of a secondary deformity
. Lengthening of the mechanical axis without angulation
. Shortening of the mechanical axis without angulation

Correct Answer & Explanation

. Angulation with translation of the bone ends

Explanation

Paley's Rule 2 dictates that an osteotomy outside the CORA with the hinge at the CORA results in angulation and translation at the osteotomy site. This successfully realigns the mechanical axis without creating a secondary "zig-zag" deformity.

Question 15351

Topic: 1. General Principles & Basic Science

In a medial opening wedge high tibial osteotomy (HTO) for a varus knee, how does the correction typically alter the sagittal plane alignment if the anterior and posterior gaps are opened equally?

. It maintains the posterior tibial slope
. It decreases the posterior tibial slope
. It increases the posterior tibial slope
. It translates the tibia anteriorly
. It shifts the mechanical axis posteriorly

Correct Answer & Explanation

. It increases the posterior tibial slope

Explanation

Opening the anterior and posterior gaps equally in a proximal tibial osteotomy increases the posterior tibial slope due to the triangular cross-section of the proximal tibia. To maintain the original slope, the anterior gap must be opened approximately half as much as the posterior gap.

Question 15352

Topic: 1. General Principles & Basic Science

According to the principles of deformity correction, if an opening wedge osteotomy is performed with the axis of the hinge placed exactly at the Center of Rotation of Angulation (CORA), which of the following best describes the resulting correction?

. Realignment of the mechanical axis without translation
. Realignment of the mechanical axis with translation
. Translation of the mechanical axis without angular correction
. Creation of a secondary CORA
. No effect on the mechanical axis

Correct Answer & Explanation

. Realignment of the mechanical axis without translation

Explanation

Rule 1 of osteotomy states that if the osteotomy and the hinge are both located at the CORA, angular correction occurs without translation. This perfectly aligns the proximal and distal mechanical axes.

Question 15353

Topic: Infection, Pharmacology & VTE

During a Total Knee Arthroplasty in a patient with a severe fixed varus deformity, what is the standard sequential soft tissue release performed on the medial side?

. Superficial MCL, Deep MCL, Pes Anserinus
. Deep MCL, Posteromedial capsule, Semimembranosus, Superficial MCL
. Pes Anserinus, Semimembranosus, Deep MCL
. Posteromedial capsule, Superficial MCL, PCL
. Superficial MCL, ACL, PCL, Semimembranosus

Correct Answer & Explanation

. Deep MCL, Posteromedial capsule, Semimembranosus, Superficial MCL

Explanation

The classic sequential medial release for a fixed varus knee begins with osteophyte excision, followed by the deep MCL, posteromedial capsule, semimembranosus insertion, and finally the superficial MCL if further correction is needed.

Question 15354

Topic: 1. General Principles & Basic Science

A 15-year-old male is undergoing femoral lengthening with a unilateral external fixator. If the bone is lengthened along the anatomical axis of the femur rather than the mechanical axis, what secondary deformity will be induced?

. Medial mechanical axis deviation (varus)
. Lateral mechanical axis deviation (valgus)
. Procurvatum deformity
. Recurvatum deformity
. Internal rotational deformity

Correct Answer & Explanation

. Lateral mechanical axis deviation (valgus)

Explanation

Because the anatomical axis of the femur is normally in 5-7 degrees of valgus relative to the mechanical axis, lengthening strictly along the anatomical axis lateralizes the distal mechanical axis, creating a valgus deformity (lateral MAD).

Question 15355

Topic: 1. General Principles & Basic Science

According to Rule 2 of deformity correction, if an osteotomy is performed at a level different from the CORA, but the axis of the hinge is placed exactly at the CORA, what is the geometric result?

. Correction of angulation without translation
. Correction of angulation with expected collinear translation
. Translation only, with no correction of angulation
. Induction of a secondary angulation
. Failure to close the osteotomy gap

Correct Answer & Explanation

. Correction of angulation with expected collinear translation

Explanation

Rule 2 states that when the hinge is at the CORA but the osteotomy is at a different level, the angulation is corrected and the mechanical axes become collinear. However, this relies on an intentional and necessary translation at the osteotomy site.

Question 15356

Topic: 1. General Principles & Basic Science

According to Paley's rules of deformity correction, if an osteotomy and the hinge (axis of rotation) are both placed at a level outside the center of rotation of angulation (CORA), what is the resulting geometric effect on the bone?

. Pure angulation without translation
. Angulation with translation resulting in collinear mechanical axes
. Angulation with translation resulting in parallel but non-collinear mechanical axes
. Pure translation without angulation
. Pure rotational correction without angulation

Correct Answer & Explanation

. Angulation with translation resulting in parallel but non-collinear mechanical axes

Explanation

Osteotomy Rule 3 states that if both the osteotomy and the hinge are outside the CORA, the mechanical axes will become parallel but translated (non-collinear). Rule 1 yields pure angulation, and Rule 2 yields angulation with collinear translated axes.

Question 15357

Topic: 1. General Principles & Basic Science

According to the principles of deformity correction, if the center of rotation of angulation (CORA) is identified, but both the osteotomy and the hinge are placed at a level proximal to the CORA, what is the expected geometric outcome upon alignment of the mechanical axes?

. Pure angulation without translation
. Angulation with translation
. Pure translation without angulation
. Shortening without angulation
. Lengthening without translation

Correct Answer & Explanation

. Angulation with translation

Explanation

According to Paley's Osteotomy Rule 3, if the hinge and osteotomy are both located at a level different from the CORA, correction of the angulation will result in translation of the bony fragments. Rule 1 yields pure angulation, while Rule 2 yields colinear axes with translation.

Question 15358

Topic: 1. General Principles & Basic Science

A 7-year-old boy presents with an insidious onset of a painless limp. Radiographs demonstrate fragmentation of the capital femoral epiphysis with exactly 50% maintenance of the lateral pillar height. According to the Herring lateral pillar classification, what is the most appropriate management?

. Observation and activity restriction
. Bilateral spica casting
. Proximal femoral varus osteotomy
. Core decompression
. In situ percutaneous pinning

Correct Answer & Explanation

. Proximal femoral varus osteotomy

Explanation

The patient has Herring Lateral Pillar Group borderline B/C (exactly 50%). In children over 8 years, or those 6-8 years old with lateral pillar B or B/C, surgical containment (such as a proximal femoral varus osteotomy) yields significantly better radiographic outcomes than nonoperative management.

Question 15359

Topic: 1. General Principles & Basic Science

A patient requires correction of a valgus deformity of the proximal tibia.

To accurately plan the correction, the surgeon must map the normal mechanical axis. Where does the mechanical axis line (MAD) typically fall in relation to the center of the knee joint in a normal patient?

. 10 mm lateral to the center
. 8 mm medial to the center
. 25 mm medial to the center
. Dead center of the knee joint
. 15 mm lateral to the center

Correct Answer & Explanation

. 8 mm medial to the center

Explanation

In a normal lower extremity, the mechanical axis line passes approximately 8 mm (range 3-17 mm) medial to the center of the knee joint. This corresponds to the typical slight mechanical varus alignment of the native knee.

Question 15360

Topic: 1. General Principles & Basic Science

When utilizing a hexapod circular frame (e.g., Taylor Spatial Frame) for simultaneous six-axis deformity correction, what does the concept of the "virtual hinge" represent?

. A physical hinge placed at the CORA on the reference ring
. The mathematical point in space around which the software calculates the correction
. The intersection of the transfixing wires on the proximal ring
. The midpoint of the lengthening struts
. The required osteotomy level

Correct Answer & Explanation

. The mathematical point in space around which the software calculates the correction

Explanation

In hexapod frame systems, physical hinges are absent. Instead, the software utilizes a "virtual hinge"โ€”a mathematical point in space (usually set at the CORA)โ€”around which all translation and angulation corrections are calculated and executed via strut adjustments.

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