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Lower Extremity Trauma MCQs

Practice Set 26 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 501

Topic: Lower Extremity Trauma

A 20-year-old basketball player lands awkwardly after a jump and sustains a twisting knee injury.

A sagittal T2-weighted MRI demonstrates a complete disruption of the anterior cruciate ligament (ACL) and a characteristic 'bone bruise' pattern. In an acute, non-contact ACL tear, where are these bone bruises most typically located on MRI?

. Anterior aspect of the lateral femoral condyle and anterior lateral tibial plateau
. Central medial femoral condyle and medial tibial plateau
. Lateral femoral condyle near the terminal sulcus and the posterolateral tibial plateau
. Medial femoral condyle and the posteromedial tibial plateau
. Patella and the anterior femoral trochlea

Correct Answer & Explanation

. Lateral femoral condyle near the terminal sulcus and the posterolateral tibial plateau

Explanation

In a non-contact ACL injury, the typical mechanism involves valgus stress and internal rotation of the femur on a fixed tibia, leading to a pivot-shift phenomenon. As the tibia subluxates anteriorly, the posterolateral aspect of the tibial plateau impacts the lateral femoral condyle (often near the terminal sulcus). This impact results in the classic 'kissing' bone bruise pattern seen on T2-weighted fat-suppressed MRI in the posterolateral tibial plateau and the lateral femoral condyle.

Question 502

Topic: Lower Extremity Trauma

An 8-year-old boy complains of a painless snapping sensation and intermittent lateral pain in his right knee. Radiographs reveal widening of the lateral joint space, squaring of the lateral femoral condyle, and a cupped appearance of the lateral tibial plateau. MRI demonstrates a complete, intact discoid lateral meniscus with no evidence of a tear. Given his symptomatic presentation, what is the recommended surgical management?

. Observation and aggressive physical therapy
. Total lateral meniscectomy
. Subtotal meniscectomy (saucerization) with preservation of a stable peripheral rim
. Meniscal repair utilizing an inside-out suturing technique without resection
. Anterior horn meniscectomy leaving the posterior horn intact

Correct Answer & Explanation

. Subtotal meniscectomy (saucerization) with preservation of a stable peripheral rim

Explanation

The patient has a symptomatic complete discoid lateral meniscus. While asymptomatic discoid menisci should be observed, symptomatic ones (snapping, pain, locking) warrant surgical intervention. The modern standard of care is subtotal meniscectomy (saucerization) to reshape the meniscus into a normal crescent, while preserving a stable 6 to 8 mm peripheral rim to maintain meniscal function and prevent early osteoarthritis. Total meniscectomy is avoided due to the high risk of rapid, severe degenerative joint disease.

Question 503

Topic: Lower Extremity Trauma

During a primary TKA, a surgeon utilizes spacer blocks to assess gap kinematics after performing standard bone cuts. The extension gap is symmetric but tight, requiring significant force to insert the block. The flexion gap is symmetric and rectangular, and accepts the spacer block with 2 mm of balanced laxity. What is the most appropriate next step to achieve balanced gaps?

. Resect more posterior femur
. Resect more proximal tibia
. Resect more distal femur
. Downsize the femoral component
. Perform a posterior capsular release

Correct Answer & Explanation

. Resect more distal femur

Explanation

The patient has a tight extension gap and an acceptable/balanced flexion gap. Resecting more distal femur will increase the extension gap without affecting the flexion gap. Resecting the proximal tibia would increase both gaps. Downsizing the femoral component or resecting more posterior femur would increase only the flexion gap.

Question 504

Topic: Lower Extremity Trauma

During a posterior-stabilized TKA, the knee is found to be symmetrically tight in flexion and well-balanced in extension. Which of the following modifications is the most appropriate step to balance the knee?

. Recut the distal femur
. Downsize the femoral component
. Release the posterior capsule
. Upsize the femoral component
. Decrease the posterior tibial slope

Correct Answer & Explanation

. Downsize the femoral component

Explanation

A knee that is symmetrically tight in flexion and balanced in extension has an isolated tight flexion gap. Downsizing the femoral component reduces the posterior condylar offset, thereby increasing the flexion gap without affecting the extension gap. Recutting the distal femur would increase the extension gap. Decreasing the posterior tibial slope would further tighten the flexion gap.

Question 505

Topic: Lower Extremity Trauma

A surgeon decides to upsize a solid titanium intramedullary nail for a tibial shaft fracture to achieve greater stability.

According to the principles of biomechanics, the bending rigidity (area moment of inertia) of a solid cylinder is proportional to the radius raised to which power?

. Radius squared (r^2)
. Radius cubed (r^3)
. Radius to the fourth power (r^4)
. Radius to the fifth power (r^5)
. Diameter squared (d^2)

Correct Answer & Explanation

. Radius to the fourth power (r^4)

Explanation

For a solid cylinder, both the area moment of inertia (resistance to bending) and the polar moment of inertia (resistance to torsion) are proportional to the radius to the fourth power (r^4). Therefore, even small increases in the diameter (and thus radius) of a solid intramedullary nail result in dramatic increases in its bending and torsional rigidity.

Question 506

Topic: Lower Extremity Trauma

A 40-year-old man sustains a severe bicondylar tibial plateau fracture (Schatzker VI) with severe soft tissue swelling. A spanning external fixator is placed. Two weeks later, the soft tissue envelope has recovered (positive wrinkle test), and the patient undergoes definitive open reduction and internal fixation using dual plates. Which of the following surgical strategies historically carries the highest risk of devastating soft tissue complications and deep infection?

. Utilizing a single midline longitudinal incision to expose both medial and lateral sides
. Delaying definitive surgery until the soft tissue swelling has completely resolved
. Using an anterolateral approach combined with a separate posteromedial approach
. Elevating full-thickness fasciocutaneous flaps during the surgical approach
. Performing minimally invasive percutaneous plate osteosynthesis (MIPPO) for the medial side

Correct Answer & Explanation

. Utilizing a single midline longitudinal incision to expose both medial and lateral sides

Explanation

Historically, utilizing a single, extensive anterior midline incision to plate both the medial and lateral columns of the tibial plateau required massive subcutaneous stripping. This severely compromises the vascular supply to the skin flaps, leading to unacceptably high rates of wound edge necrosis, breakdown, and deep infection. Standard modern management requires either dual incisions (e.g., anterolateral and posteromedial with a wide skin bridge) or minimally invasive techniques to respect the vulnerable soft tissue envelope.

Question 507

Topic: Lower Extremity Trauma

Which radiographic parameter is considered the most reliable indicator of a syndesmotic injury on standard weight-bearing anteroposterior (AP) and mortise radiographs of the ankle?

. Tibiofibular overlap of less than 1 mm
. Medial clear space greater than 4 mm
. Talar tilt greater than 10 degrees
. Tibiofibular clear space greater than 5 mm
. Disruption of Shenton's line

Correct Answer & Explanation

. Tibiofibular clear space greater than 5 mm

Explanation

The tibiofibular clear space, measured 1 cm proximal to the joint line, is the most reliable radiographic indicator of syndesmotic widening. It should normally be less than 6 mm on both AP and mortise views.

Question 508

Topic: Lower Extremity Trauma

A 23-year-old football player presents with an acute rotational ankle injury. A syndesmotic sprain is suspected. On a standard AP radiograph of the ankle, what is the normal threshold for the tibiofibular clear space, measured 1 cm proximal to the tibial plafond?

. < 6 mm
. < 4 mm
. > 6 mm
. < 2 mm
. > 10 mm

Correct Answer & Explanation

. < 6 mm

Explanation

The tibiofibular clear space is the distance between the lateral border of the posterior tibial malleolus and the medial border of the fibula, measured 1 cm proximal to the joint line. A normal value is less than 6 mm on both AP and mortise views. Values greater than 6 mm are highly suggestive of syndesmotic injury.

Question 509

Topic: Lower Extremity Trauma

Following a traumatic posterior knee dislocation, a patient presents with an ischemic lower extremity. The popliteal artery is highly susceptible to stretch injury due to its fixed anatomic location between the adductor hiatus proximally and which of the following structures distally?

. Interosseous membrane
. Soleus arch
. Tibial plateau
. Superior extensor retinaculum
. Popliteus muscle belly

Correct Answer & Explanation

. Soleus arch

Explanation

The popliteal artery is firmly tethered proximally at the adductor hiatus and distally by the fibrous arch of the soleus muscle. This rigid fixation makes it vulnerable to severe stretch and intimal tearing during high-energy knee dislocations.

Question 510

Topic: Lower Extremity Trauma

An orthopedic surgeon is evaluating an ankle MRI for a suspected syndesmotic injury. Which ligament in the syndesmotic complex constitutes the primary restraint to excessive anterior translation of the distal fibula relative to the tibia?

. Anterior inferior tibiofibular ligament
. Posterior inferior tibiofibular ligament
. Interosseous ligament
. Transverse tibiofibular ligament
. Deltoid ligament

Correct Answer & Explanation

. Anterior inferior tibiofibular ligament

Explanation

The anterior inferior tibiofibular ligament (AITFL) is the weakest of the syndesmotic ligaments but serves as the primary anatomical restraint against anterior translation of the distal fibula.

Question 511

Topic: Lower Extremity Trauma

A 9-year-old girl presents with a painful, loud "clunk" in her left knee during extension. MRI demonstrates a thickened lateral meniscus covering the entire tibial plateau without tears, but lacking posterior meniscotibial attachments. What is the diagnosis and best treatment?

. Incomplete discoid meniscus; partial meniscectomy
. Complete discoid meniscus; observation
. Wrisberg variant discoid meniscus; partial meniscectomy and peripheral stabilization
. Torn discoid meniscus; total meniscectomy
. Normal variant; reassurance

Correct Answer & Explanation

. Wrisberg variant discoid meniscus; partial meniscectomy and peripheral stabilization

Explanation

The Wrisberg variant of a discoid meniscus lacks normal posterior meniscotibial attachments (coronary ligaments), leading to hypermobility and the classic snapping knee syndrome. Treatment requires saucerization (partial meniscectomy) along with surgical stabilization of the posterior horn to the capsule.

Question 512

Topic: Lower Extremity Trauma

A 9-year-old boy weighing 38 kg sustains an isolated, closed midshaft femur fracture. What is the current gold standard treatment modality for this patient?

. Early spica casting
. Flexible intramedullary nailing
. Rigid reamed intramedullary nailing via the piriformis fossa
. Rigid reamed intramedullary nailing via the lateral trochanter
. Open reduction and plate osteosynthesis

Correct Answer & Explanation

. Flexible intramedullary nailing

Explanation

Flexible intramedullary nailing is the treatment of choice for length-stable femoral shaft fractures in school-aged children (5-11 years) weighing less than 50 kg. Rigid nailing via the piriformis is contraindicated in this age group due to the risk of avascular necrosis of the femoral head.

Question 513

Topic: Lower Extremity Trauma

During a posterolateral approach to the tibial plateau, an osteotomy of the fibular head may be performed for extended access. Which of the following nerves is at greatest risk during this maneuver, and where is it typically located?

. Deep peroneal nerve; anterior to the interosseous membrane
. Superficial peroneal nerve; lateral compartment of the leg
. Common peroneal nerve; winding around the fibular neck
. Tibial nerve; deep to the soleus muscle
. Sural nerve; posterior to the lateral malleolus

Correct Answer & Explanation

. Common peroneal nerve; winding around the fibular neck

Explanation

The common peroneal nerve wraps around the fibular neck just distal to the fibular head. It is at high risk of iatrogenic injury during a fibular head osteotomy or retractor placement in this area.

Question 514

Topic: Lower Extremity Trauma

During arthroscopic meniscectomy, understanding the differences between the medial and lateral menisci is crucial to avoid complications. Which of the following is a characteristic feature of the lateral meniscus compared to the medial meniscus?

. It is more C-shaped
. It has broader anterior and posterior horn attachments
. It is more mobile and covers a larger portion of the articular surface
. It is securely attached to the fibular collateral ligament
. It receives a richer blood supply from the middle genicular artery

Correct Answer & Explanation

. It is more mobile and covers a larger portion of the articular surface

Explanation

The lateral meniscus is more circular (O-shaped), more mobile, and covers a larger area of the tibial plateau than the medial meniscus. It lacks an attachment to the lateral collateral ligament, separated from it by the popliteus tendon.

Question 515

Topic: Lower Extremity Trauma

A 16-year-old female gymnast presents with an insidious onset of anterior knee pain. Imaging reveals an open proximal tibial physis. Which of the following findings on a lateral radiograph indicates patella alta using the Caton-Deschamps index?

. Ratio less than 0.6
. Ratio of 1.0
. Ratio greater than 1.2
. Ratio of 0.8
. Ratio less than 0.8

Correct Answer & Explanation

. Ratio greater than 1.2

Explanation

The Caton-Deschamps index measures the distance from the lower articular margin of the patella to the anterior edge of the tibial plateau, divided by the patellar articular length. A ratio greater than 1.2 is indicative of patella alta.

Question 516

Topic: Lower Extremity Trauma

A 4-year-old boy presents with progressive bilateral genu varum. Standing radiographs reveal depression of the medial tibial plateau, metaphyseal beaking, and a metaphyseal-diaphyseal angle of 18 degrees. What is the most appropriate definitive treatment?

. Observation alone with yearly radiographs.
. Knee-ankle-foot orthosis (KAFO) bracing.
. Proximal tibial valgus osteotomy.
. Medial tibial epiphysiodesis.
. Vitamin D and calcium supplementation.

Correct Answer & Explanation

. Proximal tibial valgus osteotomy.

Explanation

An MDA >16 degrees confirms the diagnosis of infantile Blount disease. Because the child is 4 years old, bracing is unlikely to be effective, and a proximal tibial valgus osteotomy is the gold standard for realignment and joint preservation.

Question 517

Topic: Lower Extremity Trauma

A 22-year-old football player sustains a hyperplantarflexion injury to his midfoot. Radiographs show a small bony avulsion in the first intermetatarsal space, known as the Fleck sign. What does this finding pathognomonically represent?

. Avulsion of the anterior talofibular ligament
. Avulsion of the Lisfranc ligament from the base of the second metatarsal
. Fracture of the os peroneum
. Avulsion of the spring ligament
. Fracture of the cuboid

Correct Answer & Explanation

. Avulsion of the Lisfranc ligament from the base of the second metatarsal

Explanation

The Fleck sign is a small bony avulsion located in the first intermetatarsal space. It is pathognomonic for a Lisfranc injury, representing the avulsion of the Lisfranc ligament that connects the medial cuneiform to the second metatarsal base.

Question 518

Topic: Lower Extremity Trauma
A 7-year-old girl presents with torticollis and her head tilted to the right and rotated to the left following an upper respiratory infection. Dynamic CT shows atlantoaxial rotatory subluxation with 4 mm of anterior displacement of C1 on C2. What is the Fielding and Hawkins classification of this injury?
. Type I
. Type II
. Type III
. Type IV
. Type V

Correct Answer & Explanation

. Type II

Explanation

Fielding and Hawkins Type II atlantoaxial rotatory subluxation is characterized by unilateral anterior displacement of one lateral mass by 3-5 mm. This indicates a deficiency or rupture of the transverse ligament.

Question 519

Topic: Lower Extremity Trauma

During closed reduction and internal fixation of a syndesmotic injury, an external rotation stress test is performed under fluoroscopy. Widening of the medial clear space greater than 4 mm is observed. This finding specifically indicates incompetence of which of the following structures?

. Anterior inferior tibiofibular ligament
. Calcaneofibular ligament
. Spring ligament
. Deep deltoid ligament
. Interosseous membrane

Correct Answer & Explanation

. Deep deltoid ligament

Explanation

The medial clear space on a mortise view evaluates the integrity of the deltoid ligament. Widening >4 mm during external rotation or gravity stress testing indicates rupture or incompetence of the deep deltoid ligament.

Question 520

Topic: Lower Extremity Trauma

A 28-year-old skier presents with acute lateral ankle pain after catching an edge. Physical examination reveals tenderness posterior to the lateral malleolus and a snapping sensation with resisted active dorsiflexion and eversion. Radiographs show a small bony avulsion flake lateral to the distal fibula. What is the most likely mechanism of this specific injury?

. Inversion and plantarflexion with an axially loaded limb
. Direct crush injury to the lateral ankle
. Hyper-plantarflexion with internal rotation of the tibia
. Sudden forceful dorsiflexion with eversion of the foot
. Gradual repetitive microtrauma from tight footwear

Correct Answer & Explanation

. Sudden forceful dorsiflexion with eversion of the foot

Explanation

The clinical presentation and "fleck sign" on radiographs describe a superior peroneal retinaculum (SPR) avulsion and subsequent peroneal tendon subluxation. This injury classically occurs via sudden, forceful dorsiflexion combined with reflex contraction of the peroneal muscles during forced eversion.

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