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2. Trauma MCQs

Practice Set 137 of 640

This practice set contains high-yield board review questions covering key concepts in 2. Trauma. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 2721

Topic: 2. Trauma

A 35-year-old patient is undergoing a distal femoral osteotomy for a varus deformity. The surgeon has completed the focal dome osteotomy and is now applying the temporary external fixator. To ensure optimal control of the deformity during the subsequent reaming and nailing, which of the following statements accurately describes the ideal placement of the external fixator pins?

. All pins should be placed in the same plane (e.g., lateral) to simplify the construct.
. Pins should be placed as close as possible to the osteotomy site to maximize stability.
. Pins must be placed out of the path of the future intramedullary nail and in a multi-planar configuration.
. Only two pins are needed, one proximal and one distal, to allow for controlled angulation.
. Pins should be placed after reaming to avoid interference with the reamer.

Correct Answer & Explanation

. Pins must be placed out of the path of the future intramedullary nail and in a multi-planar configuration.

Explanation

Correct Answer: CThe comprehensive surgical workflow explicitly states: 'Step 2: Patient Positioning and Multi-Planar Pin Placement... Crucially, these pins must be placedout of the pathof the future intramedullary nail. The surgeon must place at least two pins proximally and two pins distally, ensuring a multi-planar construct (e.g., lateral and anterior pins) to control both the frontal and sagittal planes.'Option A is incorrect:The text warns against single-plane fixation (e.g., two lateral pins) as it is biomechanically incompetent in the sagittal plane, leading to procurvatum.Option B is incorrect:While proximity to the osteotomy can increase stability, the paramount concern is that the pins do not obstruct the path of the intramedullary nail. Placing them too close without considering the nail trajectory would be a critical error.Option D is incorrect:The text specifically highlights the 'Two-Pin Fixator Dilemma,' stating it is a 'recipe for failure' due to its inability to control the sagittal plane. A multi-planar construct with at least two pins per segment is required.Option E is incorrect:Pins are placedbeforethe osteotomy and certainly before reaming, as they are used to hold the correction during reaming and nailing. Placing them after reaming would mean the correction is not held during these critical steps.

Question 2722

Topic: Lower Extremity Trauma

A 50-year-old male presents with a long-standing distal femoral valgus deformity and associated lateral compartment knee pain. Preoperative planning indicates an mLDFA of 75° and a negative MAD of 20 mm. The surgeon plans a distal femoral osteotomy using Fixator-Assisted Nailing (FAN). To achieve optimal correction and prevent the most common iatrogenic complications, which combination of strategies is most critical?

. Performing a simple transverse osteotomy at the CORA and using a two-pin external fixator.
. Placing a blocking screw medially in the distal fragment and using a multi-planar external fixator with an anterior distal pin.
. Placing a blocking screw laterally in the distal fragment and using a single-bar external fixator.
. Performing an opening wedge osteotomy to lengthen the limb and avoiding blocking screws.
. Inserting the intramedullary nail first, then applying the external fixator for correction.

Correct Answer & Explanation

. Placing a blocking screw medially in the distal fragment and using a multi-planar external fixator with an anterior distal pin.

Explanation

Correct Answer: BThe patient has a valgus deformity (mLDFA 75°, negative MAD 20 mm). To correct this, the nail needs to be guided to create a varus-producing effect. According to the 'Golden Rule' for blocking screws, to prevent recurrent valgus (the original deformity), a blocking screw should be placed on the concave side, which is medially in the distal fragment. This forces the nail laterally, correcting the valgus. Furthermore, the case emphasizes that the most common and critical error in distal femoral FAN is iatrogenic procurvatum due to inadequate sagittal plane control. This is prevented by using a multi-planar external fixator, specifically by supplementing lateral pins with at least one anterior pin in the distal segment to counteract gastrocnemius pull and nail trajectory.Option A is incorrect:A simple transverse osteotomy is inferior to a dome osteotomy biomechanically, and a two-pin external fixator is biomechanically incompetent in the sagittal plane, leading to procurvatum.Option C is incorrect:Placing a blocking screw laterally would be for a varus deformity to prevent recurrent varus, not for a valgus deformity. A single-bar fixator is inadequate for sagittal control.Option D is incorrect:An opening wedge osteotomy is a valid technique, but avoiding blocking screws for a valgus deformity would risk recurrence. Limb lengthening is not the primary goal here, and the choice of osteotomy type (opening wedge vs. dome) is a separate consideration from the critical hardware strategies for stability.Option E is incorrect:The workflow clearly states that the external fixator is applied and correction achievedbeforereaming and nail insertion. Inserting the nail first would make acute correction impossible and risk malalignment.

Question 2723

Topic: 2. Trauma

During fixator-assisted nailing (FAN) of a distal femur malunion, you plan to use Poller (blocking) screws to direct the nail and maintain alignment. For a significant extra-articular distal valgus deformity, where should the blocking screw be placed in the distal segment relative to the anticipated nail path?

. On the convex (medial) side of the deformity
. Directly in the center of the medullary canal to block over-reaming
. On the concave (lateral) side of the deformity
. Anterior to the central axis to prevent sagittal plane translation
. In the proximal segment only, avoiding the distal metaphysis

Correct Answer & Explanation

. On the concave (lateral) side of the deformity

Explanation

Blocking (Poller) screws act to artificially narrow the medullary canal and guide the intramedullary nail. To correct an angular deformity (like valgus), the blocking screw should be placed on the concave side of the deformity (lateral side for valgus) to prevent the nail from following the path of least resistance.

Question 2724

Topic: 2. Trauma

A patient presents with a tibial diaphyseal malunion demonstrating 30 degrees of apex anterior angulation (procurvatum) and 40 degrees of apex lateral angulation (varus) on orthogonal radiographs. What is the magnitude of the maximal angular deformity in the true oblique plane?

. 10 degrees
. 35 degrees
. 50 degrees
. 70 degrees
. 120 degrees

Correct Answer & Explanation

. 50 degrees

Explanation

The true magnitude of a multi-planar deformity is calculated using the Pythagorean theorem for the orthogonal angles: square root of (30^2 + 40^2) = square root of (900 + 1600) = square root of 2500 = 50 degrees.

Question 2725

Topic: 2. Trauma

When evaluating a patient's lower extremity deformity with full-length standing radiographs, the Joint Line Convergence Angle (JLCA) is measured at 7 degrees (normal 0-2 degrees). Which of the following is the most likely primary contributor to this specific abnormal measurement?

. A diaphyseal malunion of the tibia
. An extra-articular metaphyseal femoral deformity
. Ligamentous laxity or unilateral intra-articular cartilage loss
. A rotational malalignment of the femur
. Normal physiological alignment in an elite athlete

Correct Answer & Explanation

. Ligamentous laxity or unilateral intra-articular cartilage loss

Explanation

The JLCA measures the angle between the articular surfaces of the distal femur and proximal tibia. An abnormally increased JLCA typically indicates intra-articular pathology, such as asymmetric cartilage loss (arthritis) or collateral ligament laxity, rather than an extra-articular bony deformity.

Question 2726

Topic: 2. Trauma

You are performing a Fixator-Assisted Nailing (FAN) of a rigid tibial shaft malunion. To prevent the complication of intramedullary nail incarceration or unintended displacement of the fixator-held reduction during insertion, which technical step is most critical?

. Undersizing the reamer by 1 mm relative to the nail
. Over-reaming the canal by 1.5 to 2.0 mm larger than the selected nail diameter
. Placing all external fixator pins exclusively in the medial cortex
. Using a solid (un-cannulated) intramedullary nail
. Removing the external fixator prior to passing the guidewire

Correct Answer & Explanation

. Over-reaming the canal by 1.5 to 2.0 mm larger than the selected nail diameter

Explanation

In FAN for rigid deformities, the medullary canal at the malunion site is often sclerotic, narrow, and eccentric. Over-reaming by 1.5 to 2.0 mm is critical to prevent nail incarceration and allow the nail to bypass dense bone without overpowering the fixator's hold on the reduction.

Question 2727

Topic: 2. Trauma

During Fixator-Assisted Nailing (FAN) of the femur, temporary external fixation half-pins must be placed strategically to maintain the reduction. Which of the following pin placement strategies is strictly required to prevent catastrophic intraoperative complications?

. Pins must cross the planned osteotomy site bridging proximal to distal
. Pins must be placed off-center or unicortically to avoid the anticipated intramedullary path of the reamer and nail
. Pins should be placed directly through the midline of the medullary canal to maximize rigidity
. Pins must exclusively be placed in the distal condyles and femoral neck
. Pins must be left in place permanently after the nail is locked

Correct Answer & Explanation

. Pins must be placed off-center or unicortically to avoid the anticipated intramedullary path of the reamer and nail

Explanation

In FAN, half-pins should be placed unicortically or strategically off-center to avoid intersecting the central path of the medullary canal. This prevents collision with the reamer and intramedullary nail, which could result in loss of reduction, pin breakage, or thermal necrosis.

Question 2728

Topic: 2. Trauma

A 35-year-old male is undergoing Fixator-Assisted Nailing (FAN) for a proximal tibial metaphyseal fracture with a tendency toward apex anterior (procurvatum) and valgus deformity. Where should the blocking (Poller) screws be placed relative to the intended nail path in the proximal segment to prevent this malalignment?

. Anterior and lateral
. Posterior and medial
. Anterior and medial
. Posterior and lateral
. Directly central in the medullary canal

Correct Answer & Explanation

. Posterior and medial

Explanation

Blocking screws should be placed on the concave side of the deformity to restrict the nail from following the path of least resistance. For apex anterior (procurvatum) and valgus, the concave sides are posterior and medial.

Question 2729

Topic: 2. Trauma

When performing Fixator-Assisted Nailing (FAN) of the femur, what is the most critical consideration for the placement of the temporary external fixator pins?

. They must be placed exactly at the CORA.
. They must penetrate the far cortex by at least 10 mm.
. They must be placed outside the intended path of the intramedullary reamers and nail.
. They must be placed in the sagittal plane only.
. They must remain in place for 6 weeks postoperatively.

Correct Answer & Explanation

. They must be placed outside the intended path of the intramedullary reamers and nail.

Explanation

In FAN, the external fixator is used temporarily to hold the reduction. Pins must be placed entirely outside the intramedullary trajectory to allow unobstructed reaming and nail insertion.

Question 2730

Topic: 2. Trauma

Which of the following best describes the mechanical mechanism by which Poller (blocking) screws aid in intramedullary nailing of metaphyseal deformities?

. They act as lag screws to compress the osteotomy.
. They functionally narrow the medullary canal to direct the nail centrally.
. They increase the bending stiffness of the nail itself.
. They prevent rotational micro-motion at the fracture site.
. They replace the need for interlocking screws.

Correct Answer & Explanation

. They functionally narrow the medullary canal to direct the nail centrally.

Explanation

Poller screws are placed adjacent to the intended nail path in the wide metaphyseal region to functionally narrow the canal. This forces the nail into a more central trajectory and maintains alignment.

Question 2731

Topic: 2. Trauma

A surgeon is considering Fixator-Assisted Plating (FAP) instead of Fixator-Assisted Nailing (FAN) for a distal femoral deformity. Which of the following represents a distinct advantage of FAP over FAN?

. FAP allows for immediate, unrestricted full weight-bearing.
. FAP has a lower risk of hardware failure in osteoporotic bone.
. FAP avoids violation of the medullary canal, reducing the risk of fat embolism and preserving endosteal blood supply.
. FAP requires less soft tissue dissection.
. FAP permits post-operative adjustment of the correction.

Correct Answer & Explanation

. FAP avoids violation of the medullary canal, reducing the risk of fat embolism and preserving endosteal blood supply.

Explanation

Fixator-Assisted Plating (FAP) utilizes a plate instead of an IM nail. It is advantageous when canal violation must be avoided and preserves the endosteal blood supply, though it typically involves more soft tissue stripping than FAN.

Question 2732

Topic: Lower Extremity Trauma

On a long-leg AP radiograph of a patient with a diaphyseal femoral deformity, the anatomic axis of the proximal segment and the anatomic axis of the distal segment intersect at the CORA. The angle measured between these two lines is 18 degrees. What does this angle represent?

. The joint line convergence angle
. The mechanical axis deviation
. The magnitude of the angulation deformity
. The required length of the intramedullary nail
. The required translation offset

Correct Answer & Explanation

. The magnitude of the angulation deformity

Explanation

The angle formed by the intersection of the proximal and distal anatomic (or mechanical) axes at the CORA represents the true magnitude of the angular deformity in that specific plane.

Question 2733

Topic: Lower Extremity Trauma

During a Fixator-Assisted Nailing (FAN) procedure for a distal femoral valgus deformity, blocking (Poller) screws are utilized. To prevent loss of reduction and guide the nail correctly, where should the blocking screw be placed in the distal fragment?

. Medial to the intended path of the intramedullary nail
. Lateral to the intended path of the intramedullary nail
. Directly anterior to the intramedullary nail
. Directly posterior to the intramedullary nail
. In the exact center of the medullary canal

Correct Answer & Explanation

. Lateral to the intended path of the intramedullary nail

Explanation

In a valgus deformity, the apex is medial and the concave side is lateral. Blocking screws should be placed on the concave side of the deformity (lateral) to narrow the canal and force the nail to maintain the corrected alignment.

Question 2734

Topic: 2. Trauma

Which of the following geometrically defines the Center of Rotation of Angulation (CORA) in lower extremity deformity planning?

. The midpoint of the diaphysis regardless of deformity shape
. The point where the mechanical axis crosses the knee joint line
. The intersection of the proximal and distal mechanical or anatomical axis lines
. The widest portion of the metaphyseal flare
. The center of the intramedullary canal at the exact level of the fracture

Correct Answer & Explanation

. The intersection of the proximal and distal mechanical or anatomical axis lines

Explanation

The CORA is defined as the point of intersection between the proximal axis and the distal axis of a deformed bone segment. It is the geometric apex of the deformity.

Question 2735

Topic: 2. Trauma

During intramedullary nailing of a proximal third tibial shaft fracture, the surgeon notes a persistent tendency for apex anterior (procurvatum) malalignment. To mechanically correct this using a blocking screw in the proximal fragment, where must the screw be placed?

. Anterior to the intended nail path
. Posterior to the intended nail path
. Medial to the intended nail path
. Lateral to the intended nail path
. Distal to the fracture site only

Correct Answer & Explanation

. Posterior to the intended nail path

Explanation

A procurvatum deformity has an anterior apex and a posterior concavity. Placing the blocking screw posterior to the nail in the proximal fragment narrows the canal, forces the nail anteriorly, and reduces the procurvatum.

Question 2736

Topic: 2. Trauma

What is the primary technical advantage of utilizing Fixator-Assisted Nailing (FAN) over traditional free-hand intramedullary nailing for complex diaphyseal deformities?

. It eliminates the need for intraoperative fluoroscopy.
. It provides rigid maintenance of multi-planar alignment while allowing unobstructed canal reaming.
. It allows the surgeon to skip the use of distal interlocking screws.
. It stimulates faster secondary bone healing through external micromotion.
. It avoids all risks of deep intramedullary infection.

Correct Answer & Explanation

. It provides rigid maintenance of multi-planar alignment while allowing unobstructed canal reaming.

Explanation

FAN uses an external fixator placed outside the path of the nail to hold the corrected alignment rigidly. This prevents loss of reduction during the high-torque steps of reaming and nail insertion.

Question 2737

Topic: Lower Extremity Trauma

A patient presents with a biapical (two-level) tibial deformity. The surgeon chooses to perform a single osteotomy located exactly halfway between the two CORAs. To successfully restore a collinear mechanical axis, what mandatory geometric maneuver must be performed at the osteotomy site?

. Pure angular rotation
. Bone grafting of the medial cortex only
. Substantial translation of the bone segments
. Shortening of the bone by 3 centimeters
. Use of a flexible intramedullary nail instead of a rigid one

Correct Answer & Explanation

. Substantial translation of the bone segments

Explanation

When a single osteotomy is placed between two CORAs, correcting the overall alignment mathematically requires significant translation of the bone segments at the osteotomy site to restore the mechanical axis.

Question 2738

Topic: 2. Trauma

When determining the proper placement of blocking screws in metaphyseal fractures, the "acute angle rule" dictates that the screw should be placed in the acute angle formed by the intersection of which two lines?

. The joint line and the mechanical axis
. The fracture plane and the anatomical axis of the fragment
. The anterior cortex and the posterior cortex
. The path of the reamer and the path of the nail
. The proximal anatomical axis and the distal anatomical axis

Correct Answer & Explanation

. The fracture plane and the anatomical axis of the fragment

Explanation

The acute angle rule states that blocking screws should be placed in the acute angle formed by the fracture line and the anatomical axis of the bone segment. This prevents the nail from migrating and causing malalignment.

Question 2739

Topic: 2. Trauma

In Fixator-Assisted Nailing (FAN), temporary Schanz pins are placed to hold reduction. To minimize the risk of devastating deep intramedullary infection postoperatively, what is the most critical technical principle regarding these pins?

. They must be coated with antibiotic cement.
. They must be inserted under tourniquet control.
. They must not intersect or violate the planned path of the reamers and intramedullary nail.
. They must be removed within 24 hours prior to nail insertion.
. They must only be placed in the diaphyseal bone.

Correct Answer & Explanation

. They must not intersect or violate the planned path of the reamers and intramedullary nail.

Explanation

If temporary Schanz pins contaminate the intramedullary canal, placing an IM nail afterward carries a high risk of deep infection. They must be carefully positioned outside the reaming and nailing trajectory.

Question 2740

Topic: Lower Extremity Trauma

During deformity planning with Paley's methods, what geometric advantage does a true dome osteotomy performed at the CORA provide over a simple transverse single-cut osteotomy?

. It allows for translation without any angular change.
. It enables angular correction without creating an asymmetric gap or altering bone length.
. It guarantees a 20% increase in overall bone length.
. It strictly requires plate fixation instead of intramedullary nailing.
. It intentionally alters the mechanical axis away from the joint center.

Correct Answer & Explanation

. It enables angular correction without creating an asymmetric gap or altering bone length.

Explanation

A dome osteotomy (cylindrical cut) centered on the CORA allows the bone ends to rotate against each other without creating large bone gaps or inherently altering the length, facilitating excellent bone contact.

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