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Lower Extremity Trauma MCQs

Practice Set 24 of 34

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

Question 461

Topic: Lower Extremity Trauma

A surgeon chooses to ream the femoral canal to upsize a solid intramedullary nail from 10 mm to 12 mm in diameter. By what approximate factor does the bending stiffness of the solid nail increase?

. 1.20
. 1.44
. 1.73
. 2.07
. 2.44

Correct Answer & Explanation

. 1.20

Explanation

The bending stiffness of a solid cylinder is proportional to the area moment of inertia, which scales with the radius to the fourth power (r^4). Therefore, increasing diameter by a factor of 1.2 yields a stiffness increase of (1.2)^4, or roughly 2.07.

Question 462

Topic: Lower Extremity Trauma

Which of the following modifications to an intramedullary nail design will most significantly increase its torsional rigidity?

. Increasing the working length
. Adding a full-length longitudinal slot
. Increasing the outer diameter of the nail
. Decreasing the inner diameter by 1 mm
. Changing the material from titanium to standard stainless steel

Correct Answer & Explanation

. Increasing the working length

Explanation

The torsional rigidity of a solid or hollow cylinder is proportional to the radius raised to the fourth power. Therefore, increasing the outer diameter is the most effective way to exponentially increase both torsional and bending rigidity.

Question 463

Topic: Lower Extremity Trauma

When considering the structural rigidity of a diaphyseal bone or an intramedullary nail, bending stiffness is proportional to the area moment of inertia. For a hollow cylinder, if the outer radius is increased, how does the area moment of inertia change?

. It increases proportionally to the radius squared
. It increases proportionally to the radius cubed
. It increases proportionally to the radius to the fourth power
. It remains unchanged
. It decreases proportionally to the radius

Correct Answer & Explanation

. It increases proportionally to the radius squared

Explanation

The area moment of inertia for a hollow cylinder is proportional to the difference between the fourth powers of the outer and inner radii. Therefore, slightly increasing the outer radius exponentially increases the bending stiffness.

Question 464

Topic: Lower Extremity Trauma

When calculating the bending stiffness of an intramedullary nail modeled as a solid cylinder, the stiffness is directly proportional to which specific parameter of its radius (r)?

. r
. r squared
. r cubed
. r to the fourth power
. Inversely proportional to r squared

Correct Answer & Explanation

. r

Explanation

The bending stiffness of a solid cylinder is directly proportional to its area moment of inertia. For a solid cylinder, the area moment of inertia is proportional to the radius to the fourth power.

Question 465

Topic: Lower Extremity Trauma

A patient presents with a knee injury sustained from a blow to the anterolateral aspect of the flexed knee. Clinical examination reveals anteromedial rotatory instability (AMRI), characterized by valgus laxity and anterior subluxation of the medial tibial plateau. Which primary structure of the posteromedial corner is injured?

. Posterior oblique ligament (POL)
. Popliteofibular ligament
. Fibular collateral ligament
. Anterolateral ligament (ALL)
. Biceps femoris tendon

Correct Answer & Explanation

. Posterior oblique ligament (POL)

Explanation

Anteromedial rotatory instability (AMRI) is the clinical hallmark of a posteromedial corner injury. The posterior oblique ligament (POL) and the superficial MCL are the primary restraints to valgus and external rotation forces in this quadrant.

Question 466

Topic: Lower Extremity Trauma

A professional American football player sustains a forced external rotation injury to his right ankle. On examination, he has pain over the anterior inferior tibiofibular ligament (AITFL) and a positive squeeze test. Initial radiographs are negative, but a gravity stress radiograph shows a medial clear space of 6 mm. What is the most appropriate definitive management?

. Non-weight-bearing cast for 6 weeks
. Walking boot for 3 weeks followed by physical therapy
. Syndesmotic screw or suture-button fixation
. Isolated open deltoid ligament repair
. Aspiration of the ankle joint and cortisone injection

Correct Answer & Explanation

. Non-weight-bearing cast for 6 weeks

Explanation

A medial clear space >4-5 mm on stress radiographs indicates a dynamically unstable syndesmotic injury. Operative reduction and stabilization with screws or suture-button devices is required to restore the mortise and prevent early osteoarthritis.

Question 467

Topic: Lower Extremity Trauma

In orthopedic implant biomechanics, the bending stiffness of a solid cylindrical intramedullary nail is proportional to its radius raised to which power?

. Radius to the first power
. Radius squared
. Radius cubed
. Radius to the fourth power
. Radius to the fifth power

Correct Answer & Explanation

. Radius to the first power

Explanation

The bending stiffness of a solid cylinder is determined by the area moment of inertia, which is proportional to the radius to the fourth power (r^4). Therefore, a small increase in the radius significantly increases the nail's resistance to bending.

Question 468

Topic: Lower Extremity Trauma

How does doubling the diameter of a solid intramedullary nail affect its torsional rigidity?

. Increases it by a factor of 2
. Increases it by a factor of 4
. Increases it by a factor of 8
. Increases it by a factor of 16
. Increases it by a factor of 32

Correct Answer & Explanation

. Increases it by a factor of 2

Explanation

Torsional rigidity of a solid cylinder is proportional to the radius to the fourth power. Therefore, doubling the diameter increases the torsional rigidity by a factor of 16.

Question 469

Topic: Lower Extremity Trauma

If the radius of a solid intramedullary nail is increased by a factor of two, its theoretical bending stiffness increases by a factor of:

. 2
. 4
. 8
. 16
. 32

Correct Answer & Explanation

. 2

Explanation

The bending stiffness of a solid cylinder is proportional to its area moment of inertia, which scales with the radius to the fourth power. Therefore, doubling the radius increases the theoretical bending stiffness by a factor of 16.

Question 470

Topic: Lower Extremity Trauma

When a long bone is subjected to bending forces, its resistance to bending is proportional to its area moment of inertia. For a hollow cylinder, area moment of inertia is proportional to the radius raised to which power?

. 1st power
. 2nd power
. 3rd power
. 4th power
. 5th power

Correct Answer & Explanation

. 1st power

Explanation

The area moment of inertia for a cylinder is proportional to the radius to the fourth power (r^4). Thus, placing intramedullary nails with a larger radius or increasing the outer diameter of a bone exponentially increases bending rigidity.

Question 471

Topic: Lower Extremity Trauma

During a medial subvastus approach to the distal femur, the adductor canal (Hunter's canal) is visualized. Which of the following nerves runs within the adductor canal?

. Medial femoral cutaneous nerve
. Obturator nerve
. Saphenous nerve
. Tibial nerve
. Deep peroneal nerve

Correct Answer & Explanation

. Medial femoral cutaneous nerve

Explanation

The adductor canal contains the superficial femoral artery, superficial femoral vein, and the saphenous nerve. The saphenous nerve exits anteriorly before the hiatus.

Question 472

Topic: Lower Extremity Trauma

Figure 19 highlights an arthroscopic view of a meniscus.

Which of the following describes a key anatomical difference between the medial and lateral menisci?

. Medial meniscus is more circular
. Lateral meniscus covers a larger percentage of its respective tibial plateau
. Medial meniscus is more mobile
. Lateral meniscus has a firmer attachment to the capsule
. Both have an avascular inner two-thirds

Correct Answer & Explanation

. Medial meniscus is more circular

Explanation

The lateral meniscus is more circular, covers a larger percentage of the articular surface area, and is more mobile because it lacks a dense continuous capsular attachment due to the popliteus hiatus.

Question 473

Topic: Lower Extremity Trauma

A 6-year-old child presents with a painless snapping knee. MRI demonstrates a lateral meniscus covering the entire tibial plateau. Arthroscopy reveals hypermobility of the posterior horn with an absent coronary ligament. Which discoid meniscus variant is this?

. Complete variant
. Incomplete variant
. Wrisberg variant
. Ring variant
. Anterior variant

Correct Answer & Explanation

. Complete variant

Explanation

The Wrisberg variant of a discoid lateral meniscus lacks normal posterior meniscotibial (coronary) attachments. The meniscus is attached posteriorly only by the meniscofemoral ligament of Wrisberg, leading to hypermobility and a symptomatic snapping knee in young children.

Question 474

Topic: Lower Extremity Trauma

A 24-year-old football player sustains an external rotation injury to his right ankle. Radiographs demonstrate a widened medial clear space and decreased tibiofibular overlap. In a syndesmotic injury, which ligament serves as the primary restraint to anterior translation of the distal fibula?

. Posterior inferior tibiofibular ligament (PITFL)
. Anterior inferior tibiofibular ligament (AITFL)
. Interosseous membrane
. Deltoid ligament
. Anterior talofibular ligament (ATFL)

Correct Answer & Explanation

. Posterior inferior tibiofibular ligament (PITFL)

Explanation

The anterior inferior tibiofibular ligament (AITFL) is the primary restraint to anterior translation of the distal fibula and is typically the first ligament to tear in a syndesmotic injury.

Question 475

Topic: Lower Extremity Trauma

Which specific type of tibial plateau fracture is most strongly associated with an injury to the medial collateral ligament (MCL) or a lateral meniscal tear?

. Schatzker I
. Schatzker II
. Schatzker IV
. Schatzker V
. Schatzker VI

Correct Answer & Explanation

. Schatzker I

Explanation

Schatzker II (lateral split-depression) fractures are typically caused by a valgus load with axial compression. This mechanism frequently results in a concurrent lateral meniscal tear or stretching/rupture of the medial collateral ligament (MCL).

Question 476

Topic: Lower Extremity Trauma

A 45-year-old male sustains a high-energy Schatzker VI tibial plateau fracture. CT imaging demonstrates a displaced posteromedial shear fragment. You elect to utilize a posteromedial approach for buttress plating. Which of the following represents the correct internervous or intermuscular plane for this approach?

. Between the pes anserinus and the medial head of the gastrocnemius
. Between the medial head of the gastrocnemius and the soleus
. Between the semimembranosus and semitendinosus
. Between the tibialis posterior and the flexor digitorum longus
. Between the popliteus and the soleus

Correct Answer & Explanation

. Between the pes anserinus and the medial head of the gastrocnemius

Explanation

The posteromedial approach to the tibial plateau utilizes the interval between the medial head of the gastrocnemius (tibial nerve) and the pes anserinus (femoral and tibial nerves). Retracting the medial gastrocnemius laterally protects the neurovascular bundle.

Question 477

Topic: Lower Extremity Trauma

A 28-year-old male sustains a Schatzker IV medial tibial plateau fracture. A CT scan reveals a displaced posteromedial coronal shear fragment. Which surgical approach is most appropriate for direct visualization and buttress plating of this specific fragment?

. Anterolateral approach
. Direct anterior approach with tibial tubercle osteotomy
. Posteromedial approach
. Posterolateral approach
. Standard medial approach

Correct Answer & Explanation

. Anterolateral approach

Explanation

A posteromedial approach allows direct visualization and application of an anti-glide or buttress plate on the posterior aspect of the medial tibial condyle. This mechanically counteracts the typical apex distal and posterior displacement of a posteromedial shear fragment.

Question 478

Topic: Lower Extremity Trauma

When using a laterally applied pre-contoured locking plate for a bicondylar tibial plateau fracture (Schatzker VI), what is the primary biomechanical advantage of the locking screws in the proximal segment?

. They rely on friction between the plate and bone for stability
. They pull the metaphyseal bone to the plate to aid reduction
. They act as fixed-angle devices to prevent varus collapse
. They provide dynamic compression across the articular surface
. They allow for earlier hardware removal

Correct Answer & Explanation

. They rely on friction between the plate and bone for stability

Explanation

Locking screws thread directly into the plate, creating a fixed-angle construct. In metaphyseal bone, this construct strongly resists cantilever bending and prevents varus collapse of the medial plateau when relying on a single lateral plate.

Question 479

Topic: Lower Extremity Trauma

A 45-year-old male sustains a high-energy Schatzker IV tibial plateau fracture with a significant posteromedial shear fragment. Which of the following describes the most appropriate surgical approach and interval for fixing this specific fragment?

. Anterolateral approach between the iliotibial band and biceps femoris
. Posteromedial approach between the medial head of the gastrocnemius and the pes anserinus
. Posterolateral approach between the lateral head of the gastrocnemius and the soleus
. Direct medial approach elevating the superficial medial collateral ligament
. Anterior midline approach with a medial parapatellar arthrotomy

Correct Answer & Explanation

. Anterolateral approach between the iliotibial band and biceps femoris

Explanation

The posteromedial approach is ideal for direct visualization and buttress plating of a posteromedial shear fragment. The classic surgical interval is between the medial head of the gastrocnemius and the pes anserinus.

Question 480

Topic: Lower Extremity Trauma

A 30-year-old man presents with a Schatzker IV tibial plateau fracture resulting from a high-energy varus directed force. The examiner notes diminished distal pulses. Which vascular structure is most likely compromised?

. Anterior tibial artery
. Posterior tibial artery
. Popliteal artery
. Peroneal artery
. Dorsalis pedis artery

Correct Answer & Explanation

. Anterior tibial artery

Explanation

High-energy medial tibial plateau fractures (Schatzker IV) share a similar mechanism to knee dislocations. The popliteal artery is firmly tethered between the adductor hiatus proximally and the soleus arch distally, making it highly susceptible to traction or transection.

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