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Lower Extremity Trauma MCQs

Practice Set 32 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 621

Topic: Lower Extremity Trauma

The meniscal horns are primarily composed of which type of tissue, contributing to their robust attachment to the tibia?

. Elastic cartilage.
. Hyaline cartilage.
. Dense regular fibrous connective tissue.
. Adipose tissue.
. Loose areolar tissue.

Correct Answer & Explanation

. Dense regular fibrous connective tissue.

Explanation

The anterior and posterior horns of the menisci, where they attach to the tibial plateau, are composed of dense regular fibrous connective tissue. This robust, tendon-like structure allows them to firmly anchor the menisci to the bone, resisting tensile forces and maintaining the meniscal position under load. Disruption of these root attachments severely compromises meniscal function.

Question 622

Topic: Lower Extremity Trauma

The meniscal extracellular matrix contains a small percentage of elastin fibers. What is their likely functional role?

. Primary load bearing.
. Providing tensile strength to resist tearing.
. Contributing to the elastic recoil and shape recovery of the meniscus.
. Anchoring the meniscal horns to the tibial plateau.
. Facilitating nutrient diffusion into the avascular zones.

Correct Answer & Explanation

. Contributing to the elastic recoil and shape recovery of the meniscus.

Explanation

While collagen provides tensile strength and proteoglycans provide compressive stiffness, the minor component of elastin fibers likely contributes to the elastic recoil properties of the meniscus. This allows the meniscus to deform under load and then return to its original shape, helping it adapt to varying joint configurations and stresses.

Question 623

Topic: Lower Extremity Trauma

Which meniscal structure is considered the most stable in terms of its attachment to the tibial plateau?

. Anterior horn of the lateral meniscus.
. Posterior horn of the lateral meniscus.
. Anterior horn of the medial meniscus.
. Posterior horn of the medial meniscus.
. Mid-body of the lateral meniscus.

Correct Answer & Explanation

. Posterior horn of the medial meniscus.

Explanation

The posterior horn of the medial meniscus has the broadest and most robust attachment to the tibial plateau, making it the most stable meniscal attachment. This stability is crucial for its role in resisting anterior tibial translation and maintaining the integrity of the medial compartment.

Question 624

Topic: Lower Extremity Trauma

The specific topographical shape of the menisci (concave superiorly) is critical for:

. Increasing the overall mass of the knee joint.
. Allowing direct nutrient diffusion from synovial fluid.
. Improving the congruity between the femoral condyles and tibial plateau.
. Providing a stable attachment point for the collateral ligaments.
. Reducing the overall joint volume.

Correct Answer & Explanation

. Improving the congruity between the femoral condyles and tibial plateau.

Explanation

The wedge-shaped, concave superior surface of the menisci is crucial for improving the congruity between the convex femoral condyles and the relatively flat tibial plateau. This enhanced congruity effectively increases the contact area across the tibiofemoral joint, thereby distributing loads more evenly and reducing peak contact stresses on the articular cartilage.

Question 625

Topic: Lower Extremity Trauma

What is the primary function of the meniscotibial ligaments (coronary ligaments)?

. To connect the anterior horns of the menisci.
. To attach the menisci to the femoral condyles.
. To anchor the menisci to the tibial plateau.
. To provide stability to the fibular head.
. To transmit proprioceptive signals from the posterior capsule.

Correct Answer & Explanation

. To anchor the menisci to the tibial plateau.

Explanation

The meniscotibial ligaments, also known as the coronary ligaments, are capsular attachments that anchor the peripheral borders of the menisci to the tibial plateau. These attachments provide stability to the menisci, limiting their excessive displacement during knee movement, though they allow for some degree of physiological translation.

Question 626

Topic: Lower Extremity Trauma

The meniscal 'white-white' zone is characterized by:

. High vascularity and cellularity.
. Lack of blood supply and poor healing capacity.
. Predominance of elastic fibers.
. Strongest mechanical attachment to the tibial plateau.
. High concentration of Pacinian corpuscles.

Correct Answer & Explanation

. Lack of blood supply and poor healing capacity.

Explanation

The 'white-white zone' refers to the inner two-thirds (or more) of the meniscal body that is completely avascular. This lack of blood supply means that tears in this region have extremely poor to non-existent intrinsic healing capacity, making surgical repair generally unsuccessful.

Question 627

Topic: Lower Extremity Trauma

The primary biomechanical role of the menisci in the knee joint is to:

. Limit hyperextension of the knee.
. Increase the congruity between the femoral condyles and tibial plateau.
. Provide intrinsic stability against varus and valgus stress.
. Lubricate the articular surfaces.
. House proprioceptive nerve endings for joint position sense.

Correct Answer & Explanation

. Increase the congruity between the femoral condyles and tibial plateau.

Explanation

The menisci are C-shaped fibrocartilaginous structures that sit on the tibial plateau. Their primary biomechanical roles include increasing the contact area between the femoral condyles and tibial plateau, which significantly reduces contact stress on the articular cartilage. They also contribute to joint stability, shock absorption, and some lubrication, but increasing congruity and reducing stress are their most critical functions. Ligaments limit hyperextension and provide varus/valgus stability.

Question 628

Topic: Lower Extremity Trauma

A 25-year-old male presents with lateral ankle pain and a snapping sensation behind the lateral malleolus when the ankle is actively dorsiflexed and everted. Radiographs demonstrate a small bony "fleck" lateral to the distal fibula. What is the anatomic basis of this pathology?

. Avulsion of the calcaneofibular ligament
. Avulsion of the superior peroneal retinaculum from the fibula
. Longitudinal split tear of the peroneus brevis
. Os trigonum impingement
. Rupture of the inferior peroneal retinaculum

Correct Answer & Explanation

. Avulsion of the superior peroneal retinaculum from the fibula

Explanation

The patient has peroneal tendon subluxation. The "fleck sign" on an AP ankle radiograph represents a bony avulsion of the superior peroneal retinaculum (SPR) from the lateral malleolus. Surgical treatment typically involves SPR repair and potential fibular groove deepening.

Question 629

Topic: Lower Extremity Trauma

During evaluation of a patient with an acute ankle sprain, a positive external rotation stress test is elicited. On the AP radiograph, what is the normal expected tibiofibular overlap measured 1 cm proximal to the joint line?

. Less than 1 mm
. Greater than 10 mm
. Greater than 1 mm
. Less than 5 mm
. Greater than 6 mm

Correct Answer & Explanation

. Greater than 6 mm

Explanation

In a normal ankle, the tibiofibular overlap on an AP radiograph should be >6 mm (or >1 mm on the mortise view). Decreased overlap indicates a syndesmotic injury (distal tibiofibular diastasis) which may require surgical stabilization.

Question 630

Topic: Lower Extremity Trauma

A 24-year-old soccer player sustains an inversion ankle injury. Weight-bearing radiographs reveal a 5 mm medial clear space, which increases to 8 mm on external rotation stress views. The fibula is intact. What is the most appropriate definitive management?

. Short leg cast for 6 weeks
. Cam boot with early functional rehabilitation
. Open reduction and internal fixation of the medial malleolus
. Syndesmotic screw or suture-button fixation
. Primary repair of the anterior talofibular ligament

Correct Answer & Explanation

. Syndesmotic screw or suture-button fixation

Explanation

This patient has a purely ligamentous syndesmotic injury with instability, demonstrated by widening of the medial clear space on stress views. Operative fixation with syndesmotic screws or suture-button devices is required to restore and maintain the mortise.

Question 631

Topic: Lower Extremity Trauma

A solid intramedullary nail has a radius of 'r'. If a new solid nail is manufactured with a radius of '2r', how much will its bending rigidity increase?

. 2 times
. 4 times
. 8 times
. 16 times
. 32 times

Correct Answer & Explanation

. 16 times

Explanation

The bending rigidity (area moment of inertia) of a solid cylinder is proportional to the radius raised to the fourth power (r^4). Therefore, doubling the radius (2r)^4 results in a 16-fold increase in bending rigidity.

Question 632

Topic: Lower Extremity Trauma

During a pivot-shift test for an anterior cruciate ligament (ACL) deficient knee, the tibia reduces at approximately 20-30 degrees of flexion. Which structure is primarily responsible for generating the force that reduces the tibia?

. Medial collateral ligament
. Posterior cruciate ligament
. Iliotibial band
. Biceps femoris
. Popliteus

Correct Answer & Explanation

. Iliotibial band

Explanation

The pivot-shift test demonstrates a subluxated tibia in extension that reduces in flexion. The iliotibial band (ITB) changes from an extensor to a flexor at 20-30 degrees of flexion, creating a posterior force vector that reduces the anteriorly subluxated lateral tibial plateau.

Question 633

Topic: Lower Extremity Trauma

In assessing a patient with a suspected syndesmotic injury, radiographs are obtained. Which radiographic parameter is considered the most reliable indicator of syndesmotic widening on a standard AP or Mortise view?

. Tibiofibular overlap > 10 mm on the AP view
. Medial clear space < 4 mm on the Mortise view
. Tibiofibular clear space > 6 mm measured 1 cm proximal to the plafond
. Talar tilt angle > 5 degrees on the Mortise view
. Shenton's line of the ankle disruption

Correct Answer & Explanation

. Tibiofibular clear space > 6 mm measured 1 cm proximal to the plafond

Explanation

A tibiofibular clear space greater than 5-6 mm on either the AP or Mortise view is the most reliable and reproducible radiographic parameter indicating syndesmotic widening.

Question 634

Topic: Lower Extremity Trauma

In performing a transfemoral amputation, myodesis is crucial to prevent adductor roll and optimize prosthetic fitting. To which structure should the adductor magnus be secured?

. Iliotibial band
. Linea aspera
. Lateral femur
. Distal posterior femur
. Anterior cortex of the distal femur

Correct Answer & Explanation

. Lateral femur

Explanation

In a transfemoral amputation, the adductor magnus is typically secured to the lateral aspect of the distal femur (adductor myodesis). This preserves the biomechanical advantage of the adductors and prevents an abduction contracture.

Question 635

Topic: Lower Extremity Trauma

A surgeon decides to increase the diameter of a solid titanium intramedullary nail from 10 mm to 12 mm. By what approximate factor will the torsional rigidity of the nail increase?

. 1.2
. 1.44
. 2.07
. 2.98
. 4.0

Correct Answer & Explanation

. 2.07

Explanation

The torsional rigidity of a solid cylinder is proportional to the fourth power of its radius (r^4). Increasing the diameter by a factor of 1.2 increases the rigidity by 1.2^4, which is approximately 2.07.

Question 636

Topic: Lower Extremity Trauma

During a posteromedial approach to the proximal tibia for fixation of a complex Schatzker IV plateau fracture, the surgeon develops the primary deep interval to expose the posterior aspect of the medial tibial condyle. Which two structures define this standard internervous/anatomical interval?

. Tibialis anterior and extensor digitorum longus
. Medial head of the gastrocnemius and the pes anserinus (semimembranosus)
. Lateral head of the gastrocnemius and the popliteus
. Soleus and flexor hallucis longus
. Tibialis posterior and flexor digitorum longus

Correct Answer & Explanation

. Medial head of the gastrocnemius and the pes anserinus (semimembranosus)

Explanation

The classic posteromedial approach to the tibial plateau utilizes the interval between the medial head of the gastrocnemius (which is retracted posterolaterally to protect the neurovascular bundle) and the pes anserinus / semimembranosus (which is retracted anteromedially). This safely exposes the posteromedial cortex of the proximal tibia.

Question 637

Topic: Lower Extremity Trauma
Based on the principles of biomechanics, if the outer radius of a solid cylindrical intramedullary nail is doubled while maintaining the same material, by what factor does its bending stiffness (area moment of inertia) increase?
. 2 times
. 4 times
. 8 times
. 16 times
. 32 times

Correct Answer & Explanation

. 16 times

Explanation

Bending stiffness of a solid cylinder is proportional to its area moment of inertia, which is calculated by the formula (π * r^4) / 4. Because the radius (r) is raised to the fourth power, doubling the radius (2^4) results in a 16-fold increase in the bending stiffness of the nail.

Question 638

Topic: Lower Extremity Trauma

A solid cylindrical intramedullary nail is being redesigned to increase its bending rigidity. If the radius of the solid nail is increased by a factor of two, by what factor does its bending rigidity increase?

. 2
. 4
. 8
. 16
. 32

Correct Answer & Explanation

. 16

Explanation

Bending rigidity of a solid cylinder is proportional to the area moment of inertia, which scales with the radius to the fourth power (r^4). Therefore, doubling the radius increases the bending rigidity by a factor of 2^4, or 16.

Question 639

Topic: Lower Extremity Trauma

During a total knee arthroplasty, the surgeon assesses the gaps with trial components. The knee is tight in extension and balanced in flexion. Which of the following is the most appropriate intraoperative adjustment?

. Upsize the femoral component
. Downsize the femoral component
. Resect more distal femur
. Resect more proximal tibia
. Recut the posterior femoral condyles

Correct Answer & Explanation

. Resect more distal femur

Explanation

A tight extension gap with a balanced flexion gap indicates that the distal femur is under-resected. Resecting more distal femur will increase the extension space without altering the balanced flexion gap.

Question 640

Topic: Lower Extremity Trauma

According to the principles of intramedullary nailing, increasing the radius of a solid intramedullary nail by a factor of 2 will increase its torsional rigidity by what factor?

. 2
. 4
. 8
. 16
. 32

Correct Answer & Explanation

. 16

Explanation

The torsional rigidity of a solid cylinder is proportional to the polar moment of inertia, which scales with the radius to the fourth power (r^4). Therefore, doubling the radius increases torsional rigidity by a factor of 16.

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