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1. General Principles & Basic Science MCQs

Practice Set 141 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 2801

Topic: 1. General Principles & Basic Science

A surgeon is correcting a complex tibial deformity using Paley's Osteotomy Rule 3. The ACA (Angulation Correction Axis) and the osteotomy are both located at a level distinct from the CORA (Center of Rotation of Angulation). What will be the alignment outcome of the mechanical axes after pure angular correction at the ACA?

. The proximal and distal mechanical axes will be collinear.
. The proximal and distal mechanical axes will be parallel and translated.
. The osteotomy gap will close primarily on the concave side.
. The deformity will paradoxically worsen.
. A pure translational deformity will be corrected completely.

Correct Answer & Explanation

. The proximal and distal mechanical axes will be parallel and translated.

Explanation

According to Paley's Rule 3, when both the ACA and the osteotomy are placed away from the CORA, pure angular correction will result in parallel, rather than collinear, mechanical axes (unintended translation of the limb segments).

Question 2802

Topic: 1. General Principles & Basic Science

A patient with a diaphyseal femoral deformity has an anatomic-mechanical angle (AMA) evaluated on standing radiographs. Which of the following statements best describes the normal relationship between the femoral anatomic and mechanical axes?

. They are identical and perfectly superimposed.
. The anatomic axis is typically 7 degrees valgus relative to the mechanical axis.
. The anatomic axis is typically 7 degrees varus relative to the mechanical axis.
. The mechanical axis passes through the greater trochanter while the anatomic axis passes through the femoral head.
. The axes are parallel but separated by approximately 10 mm.

Correct Answer & Explanation

. The anatomic axis is typically 7 degrees valgus relative to the mechanical axis.

Explanation

The normal femoral mechanical axis is drawn from the center of the femoral head to the center of the knee. The anatomic axis runs down the intramedullary canal. The anatomic axis typically diverges in 7 degrees of valgus relative to the mechanical axis.

Question 2803

Topic: 1. General Principles & Basic Science

A patient presents with a multi-apical tibial deformity. Radiographic analysis reveals that the proximal mechanical axis and distal mechanical axis are parallel but do not intersect. This finding is indicative of what type of deformity?

. Pure angular deformity
. Pure translational deformity
. Rotational deformity
. Length discrepancy without malalignment
. Intra-articular deformity

Correct Answer & Explanation

. Pure translational deformity

Explanation

When the proximal and distal mechanical axes are parallel but do not intersect, the deformity is purely translational. A true CORA does not exist at a single finite point; instead, correction requires translation rather than angulation.

Question 2804

Topic: 1. General Principles & Basic Science

Which peripheral nerve is most at risk and requires close clinical monitoring during acute correction of a severe genu valgum deformity or proximal tibial medial opening wedge osteotomy?

. Tibial nerve
. Deep peroneal nerve
. Common peroneal nerve
. Saphenous nerve
. Sural nerve

Correct Answer & Explanation

. Common peroneal nerve

Explanation

The common peroneal nerve is tethered at the fibular neck and is highly susceptible to stretch injury during acute correction of severe valgus deformities or substantial lengthening of the lateral column of the lower leg.

Question 2805

Topic: 1. General Principles & Basic Science

In distraction osteogenesis, plain radiographs show a 'cystic' or radiolucent appearance in the central fibrous interzone of the regenerate after 6 weeks of distraction at 1 mm/day. What is the most appropriate next step in management?

. Increase the rate of distraction to 1.5 mm/day.
. Decrease the rate of distraction or institute 'accordion' maneuvers (compression-distraction).
. Immediately proceed to bone grafting.
. Remove the fixator and place a cast.
. Administer systemic corticosteroids to reduce inflammation.

Correct Answer & Explanation

. Decrease the rate of distraction or institute 'accordion' maneuvers (compression-distraction).

Explanation

A cystic or widely radiolucent interzone indicates poor bone formation (delayed consolidation). The initial management is to slow the distraction rate (e.g., to 0.5 mm/day) or perform accordion maneuvers (compression then distraction) to stimulate osteogenesis.

Question 2806

Topic: 1. General Principles & Basic Science

A surgeon utilizes a Taylor Spatial Frame (TSF) for a complex multiplanar tibial deformity. The software utilizes a web-based program requiring input of specific parameters. Which of the following is NOT one of the required radiographic inputs for generating the prescription in the standard TSF program?

. Anteroposterior view translation
. Lateral view translation
. Anteroposterior view angulation
. Axial view rotation
. Joint line congruency angle (JLCA)

Correct Answer & Explanation

. Joint line congruency angle (JLCA)

Explanation

The standard TSF software requires 6 parameters of deformity (AP angulation/translation, Lateral angulation/translation, Axial rotation, and Length discrepancy). The JLCA is an anatomic measurement used for analysis but is not a direct input parameter for the TSF strut calculation software.

Question 2807

Topic: 1. General Principles & Basic Science

A surgeon plans to correct a distal femoral deformity.

The Angulation Correction Axis (ACA) is placed exactly at the CORA, but the osteotomy is performed 3 cm proximal to the CORA. According to Paley's Osteotomy Rule 2, what is the expected outcome of this configuration?

. Pure angulation resulting in parallel, non-collinear mechanical axes.
. Pure angulation resulting in perfectly collinear mechanical axes.
. Angulation and translation occurring simultaneously, resulting in collinear mechanical axes.
. Angulation and translation resulting in parallel, non-collinear mechanical axes.
. Pure translation with no angular correction.

Correct Answer & Explanation

. Angulation and translation occurring simultaneously, resulting in collinear mechanical axes.

Explanation

Paley's Osteotomy Rule 2 states that if the ACA is at the CORA but the osteotomy is at a different level, the correction will result in both angulation and translation at the osteotomy site. This simultaneous translation ensures that the proximal and distal mechanical axes end up fully collinear.

Question 2808

Topic: 1. General Principles & Basic Science

According to Paley's Osteotomy Rule 3, if both the Angulation Correction Axis (ACA) and the osteotomy are placed at a level distinct from the Center of Rotation of Angulation (CORA), what is the geometric result after angular correction?

. Pure angulation resulting in perfectly collinear mechanical axes.
. Angulation and translation resulting in parallel but non-collinear mechanical axes.
. Angulation and translation resulting in fully collinear mechanical axes.
. Pure translation resulting in collinear mechanical axes.
. The mechanical axes will intersect at the level of the joint line.

Correct Answer & Explanation

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

Explanation

Osteotomy Rule 3 dictates that placing the ACA and the osteotomy outside the CORA leads to an angular correction that leaves the mechanical axes parallel but shifted (non-collinear). This introduces a secondary translation deformity that must be addressed.

Question 2809

Topic: 1. General Principles & Basic Science

In the context of deformity correction geometry, how can pure translation of a bone segment be achieved without any angular change?

. Placing the ACA at the CORA and the osteotomy at the CORA.
. Placing the ACA at infinity and performing the osteotomy at the level of the desired translation.
. Placing the ACA at the CORA and the osteotomy away from the CORA.
. Utilizing an opening wedge osteotomy with the hinge on the concave cortex.
. Performing a closing wedge osteotomy with the hinge in the medullary canal.

Correct Answer & Explanation

. Placing the ACA at infinity and performing the osteotomy at the level of the desired translation.

Explanation

Pure translation mathematically requires an axis of rotation (ACA) located at infinity. In practical circular fixator application, this is achieved by using two parallel hinges or programming a spatial frame for pure translation.

Question 2810

Topic: 1. General Principles & Basic Science

When planning correction for a diaphyseal long bone deformity, drawing the proximal and distal anatomical axes reveals that they do not intersect within the confines of the bone. What does this geometric finding indicate?

. A purely rotational deformity.
. A simple uni-apical deformity.
. A multi-apical deformity requiring a multi-level osteotomy or a single osteotomy with translation.
. An intra-articular deformity.
. A compensatory deformity of the adjacent joint.

Correct Answer & Explanation

. A multi-apical deformity requiring a multi-level osteotomy or a single osteotomy with translation.

Explanation

If the axes do not intersect within the bone, the deformity cannot be uni-apical. This indicates a multi-apical deformity, necessitating either multiple osteotomies at each CORA or a single osteotomy that incorporates significant translation.

Question 2811

Topic: 1. General Principles & Basic Science

A surgeon is evaluating a tibial diaphyseal deformity using Paley's principles.

According to Osteotomy Rule 1, if the osteotomy and the Angulation Correction Axis (ACA) are both placed precisely at the Center of Rotation of Angulation (CORA), what is the resulting geometric correction?

. Pure angulation with collinear mechanical axes
. Angulation with intentional translation and collinear mechanical axes
. Angulation with unintended translation and parallel mechanical axes
. Pure translation without angular change
. Lengthening with a secondary rotational deformity

Correct Answer & Explanation

. Pure angulation with collinear mechanical axes

Explanation

Paley's Osteotomy Rule 1 states that when both the osteotomy and the ACA are performed at the CORA, the mechanical axes will fully realign collinearly through pure angulation. No translation is produced.

Question 2812

Topic: 1. General Principles & Basic Science

According to Paley's Osteotomy Rule 2, if the angulation correction axis (ACA) is placed exactly at the center of rotation of angulation (CORA), but the osteotomy is performed at a different diaphyseal level, what is the resulting alignment after correction?

. Pure angulation without translation
. Angulation with expected translation and collinear mechanical axes
. Angulation with unintended translation and parallel mechanical axes
. Pure translation without angulation
. Creation of a secondary multi-apical deformity

Correct Answer & Explanation

. Angulation with expected translation and collinear mechanical axes

Explanation

Osteotomy Rule 2 states that if the ACA is at the CORA but the osteotomy is at a different level, the mechanical axes will fully realign (collinear). However, the bone fragments will predictably translate at the osteotomy site.

Question 2813

Topic: 1. General Principles & Basic Science

A 60-year-old female presents with severe varus knee osteoarthritis. Radiographs reveal a Medial Proximal Tibial Angle (MPTA) of 86°, a Mechanical Lateral Distal Femoral Angle (mLDFA) of 88°, and a Joint Line Convergence Angle (JLCA) of 7° opening laterally. Which of the following best explains the varus mechanical axis deviation (MAD) in this patient?

. Tibial diaphyseal bowing
. Distal femoral varus deformity
. Intra-articular deformity
. Proximal tibial varus deformity
. Combined extra-articular bony deformities

Correct Answer & Explanation

. Intra-articular deformity

Explanation

Both the MPTA and mLDFA are within normal limits, ruling out an extra-articular bony deformity. A JLCA greater than 2° indicates an intra-articular source, typically due to asymmetric cartilage loss or ligamentous laxity.

Question 2814

Topic: Biomechanics & Biomaterials
A 30-year-old construction worker sustains a Rockwood Type III AC joint separation. Understanding the biomechanics of the AC joint is crucial for treatment planning. Which of the following statements accurately describes the primary role of the coracoclavicular (CC) ligaments in AC joint stability?
. They primarily resist anterior and posterior shear forces at the AC joint.
. They are the main stabilizers against superior translation of the clavicle.
. They provide the majority of horizontal stability to the AC joint.
. The conoid ligament primarily resists anterior displacement, while the trapezoid resists posterior displacement.
. They form part of the coracoacromial arch, preventing superior humeral head migration.

Correct Answer & Explanation

. They are the main stabilizers against superior translation of the clavicle.

Explanation

The coracoclavicular (CC) ligaments (conoid and trapezoid) are the primary vertical stabilizers of the AC joint. They provide approximately 70-80% of the vertical stability, resisting superior translation of the clavicle relative to the acromion.

Question 2815

Topic: 1. General Principles & Basic Science

Following the wide surgical resection and epimesial dissection of the sciatic nerve, the patient underwent postoperative management. Given the history of neoadjuvant radiation therapy, which of the following is the *most* critical aspect of acute postoperative wound management?

. A. Early aggressive range of motion exercises to prevent stiffness.
. B. Immediate removal of surgical drains within 24 hours to reduce infection risk.
. C. Meticulous drain management, leaving drains in until output is consistently low, to prevent seroma and wound dehiscence.
. D. High-dose systemic corticosteroids to reduce inflammation and promote wound healing.
. E. Strict bed rest for the first week to minimize stress on the wound.

Correct Answer & Explanation

. C. Meticulous drain management, leaving drains in until output is consistently low, to prevent seroma and wound dehiscence.

Explanation

Correct Answer: CThe most critical aspect of acute postoperative wound management, especially after neoadjuvant radiation, ismeticulous drain management, leaving drains in until output is consistently low, to prevent seroma and wound dehiscence. The case highlights this: 'Drain management is critical. The closed-suction drains were left in place until the output decreased to less than 30 cc per 24-hour period for two consecutive days. In irradiated fields, lymphatic leakage can be prolonged, and premature drain removal frequently leads to seroma formation and subsequent wound dehiscence.'Option A (Early aggressive range of motion exercises to prevent stiffness): While rehabilitation is important, early aggressive range of motion could jeopardize wound healing, especially in an irradiated field prone to dehiscence. Rehabilitation is phased and carefully progressed.Option B (Immediate removal of surgical drains within 24 hours to reduce infection risk): This is incorrect. Premature drain removal in irradiated fields is a major cause of seroma and wound complications, as lymphatic leakage can be prolonged. Drains are kept in longer than usual.Option D (High-dose systemic corticosteroids to reduce inflammation and promote wound healing): Corticosteroids can impair wound healing and increase infection risk, especially in the context of surgery and radiation. They are generally not used routinely for this purpose.Option E (Strict bed rest for the first week to minimize stress on the wound): While activity is restricted, strict bed rest is generally avoided due to the risk of DVT and other complications. Early mobilization within safe limits is encouraged, along with DVT prophylaxis.

Question 2816

Topic: 1. General Principles & Basic Science

During surgical reconstruction of a chronic Type V AC joint separation, the surgeon aims to restore normal clavicular translation. The conoid ligament is primarily responsible for resisting which of the following forces?

. Anterior translation
. Posterior translation
. Superior translation
. Inferior translation
. Axial compression

Correct Answer & Explanation

. Superior translation

Explanation

The conoid ligament is the primary restraint to superior translation of the distal clavicle. The trapezoid provides the primary restraint against axial compression.

Question 2817

Topic: 1. General Principles & Basic Science

When performing an anatomic reconstruction of the coracoclavicular ligaments, accurate tunnel placement is crucial. The normal footprint of the conoid ligament on the clavicle is located approximately how far medial to the AC joint line?

. 1.5 cm
. 2.5 cm
. 4.5 cm
. 6.0 cm
. 7.5 cm

Correct Answer & Explanation

. 4.5 cm

Explanation

The conoid ligament footprint is located posteromedially on the clavicle, approximately 4.5 cm medial to the AC joint. The trapezoid footprint is located more anterolaterally, roughly 2.5 cm medial.

Question 2818

Topic: 1. General Principles & Basic Science

A patient presents with an indeterminate AC joint injury. Routine AP and scapular Y views are inconclusive. Which of the following radiographic views is most useful to specifically evaluate posterior displacement of the clavicle relative to the acromion (Rockwood Type IV)?

. Zanca view
. Stryker Notch view
. Axillary lateral view
. West Point view
. Serendipity view

Correct Answer & Explanation

. Axillary lateral view

Explanation

The axillary lateral view is crucial for evaluating anterior-posterior displacement of the distal clavicle relative to the acromion. It definitively identifies Rockwood Type IV injuries.

Question 2819

Topic: 1. General Principles & Basic Science

In a biomechanical study evaluating AC joint stability, sequential sectioning of ligaments is performed. Sectioning of the superior AC ligament primarily increases which of the following translations of the distal clavicle?

. Superior translation
. Inferior translation
. Anterior and posterior translation
. Medial translation
. Axial compression

Correct Answer & Explanation

. Anterior and posterior translation

Explanation

The AC ligaments (specifically the superior and posterior bands) are the primary restraints to anterior-posterior translation of the distal clavicle. The CC ligaments are the primary restraints to vertical translation.

Question 2820

Topic: 1. General Principles & Basic Science

During a distal clavicle excision (Mumford procedure) for AC joint osteoarthritis, the surgeon must be careful not to resect too much bone. Resecting more than what length of the distal clavicle significantly increases the risk of anterior-posterior instability?

. 2-3 mm
. 5-7 mm
. 10-15 mm
. 20-25 mm
. 25-30 mm

Correct Answer & Explanation

. 10-15 mm

Explanation

Resecting >10-15 mm of the distal clavicle risks disruption of the superior and posterior AC joint capsule and ligaments. This leads to iatrogenic horizontal (A-P) instability of the clavicle.

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