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Lower Extremity Trauma MCQs

Practice Set 20 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 381

Topic: Lower Extremity Trauma
During a posterior cruciate ligament-sacrificing total knee arthroplasty with anterior referencing, 8 mm of distal femur is resected. It is noted that the flexion gap is tight and the extension gap appears stable. What is the next most appropriate step in management?
. Cut more proximal tibia.
. Cut more distal femur.
. Cut both the proximal tibia and distal femur.
. Decrease the size of the femoral component.
. Decrease the tibial polyethylene insert thickness.

Correct Answer & Explanation

. Decrease the size of the femoral component.

Explanation

If the flexion gap is tight and the extension gap is correct, it is preferable to change only the flexion gap and leave the extension gap unchanged; therefore, the treatment of choice is to decrease the size of the femoral component. The smaller component will be smaller in both medial-lateral as well as anterior-posterior dimensions. A smaller anterior-posterior size will allow more space for the flexion gap without significantly affecting the extension gap. Decreasing the size of the tibial polyethylene insert thickness or cutting more proximal tibia will affect both the flexion and extension gaps. Cutting more distal femur will increase the extension gap and not change the flexion gap, making the described situation worse. Cutting both the proximal tibia and distal femur will increase both the flexion and extension gaps.

Question 382

Topic: Lower Extremity Trauma
Which of the following factors is responsible for causing the distal femur to pivot about a medial axis as the knee moves from full extension into early flexion?
. Differential forces generated from the vastus lateralis and vastus medialis
. Differential tension within the bundles of the posterior cruciate ligament
. Differential radius of curvature between the medial and lateral femoral condyles
. Asymmetry of the tibial tubercle on the anterior surface of the tibia
. Asymmetric forces generated from the uneven patellar facets

Correct Answer & Explanation

. Differential radius of curvature between the medial and lateral femoral condyles

Explanation

DISCUSSION: The radius of curvature of the distal femur is greater over the distal aspect of the lateral femoral condyle than the distal aspect of the medial femoral condyle. As the femur rolls posteriorly during early knee flexion, both condyles undergo similar angular changes equal to the amount of flexion. With a similar amount of angular rotation, the sphere with the larger radius experiences greater net rollback, producing a pivoting motion.

Question 383

Topic: Lower Extremity Trauma

A 19-year-old sustains a high-energy knee dislocation. During evaluation in the emergency department, the knee is completely irreducible despite multiple closed attempts under procedural sedation. The skin over the anteromedial aspect of the knee exhibits a pronounced 'dimple sign' (transverse furrow). What is the specific anatomic cause of this irreducibility?

. Entrapment of the patella within the intercondylar notch
. Buttonholing of the medial femoral condyle through the anteromedial capsule
. Interposition of the torn anterior cruciate ligament stump in the joint
. Dislocation of the fibular head locking the lateral structures
. Entrapment of the popliteal artery behind the tibial plateau

Correct Answer & Explanation

. Entrapment of the patella within the intercondylar notch

Explanation

The 'dimple sign' or transverse furrow across the anteromedial joint line in a posterolateral knee dislocation indicates an irreducible dislocation. This is caused by the medial femoral condyle buttonholing through the anteromedial capsule, medial retinaculum, or vastus medialis. The capsule becomes interposed between the tibia and femur, preventing closed reduction and mandating open surgical reduction.

Question 384

Topic: Lower Extremity Trauma

A 45-year-old female presents with a Schatzker IV tibial plateau fracture featuring a large posteromedial fragment. A posteromedial surgical approach is planned for buttress plating. Which of the following defines the correct surgical interval for this approach?

. Between the medial head of the gastrocnemius and the soleus
. Between the pes anserinus anteriorly and the medial head of the gastrocnemius posteriorly
. Between the semimembranosus and the pes anserinus tendons
. Between the medial collateral ligament and the pes anserinus
. Between the popliteus muscle and the soleus

Correct Answer & Explanation

. Between the medial head of the gastrocnemius and the soleus

Explanation

The classic posteromedial approach to the tibial plateau utilizes the interval between the pes anserinus (sartorius, gracilis, semitendinosus) anteriorly and the medial head of the gastrocnemius posteriorly. Retracting the medial gastrocnemius posteriorly protects the neurovascular bundle in the popliteal fossa.

Question 385

Topic: Lower Extremity Trauma

A 45-year-old female presents with a Schatzker IV tibial plateau fracture involving a large, displaced posteromedial articular fragment. The surgeon plans an open reduction and internal fixation via a posteromedial approach. To safely access the posterior column of the tibial plateau, the surgical interval is developed between which two structures?

. The medial head of the gastrocnemius and the soleus
. The medial head of the gastrocnemius and the pes anserinus/semimembranosus
. The lateral head of the gastrocnemius and the biceps femoris
. The popliteus muscle substance and the posterolateral corner
. The sartorius and the gracilis

Correct Answer & Explanation

. The medial head of the gastrocnemius and the soleus

Explanation

The posteromedial approach to the tibial plateau is performed utilizing the internervous/intermuscular interval between the medial head of the gastrocnemius (retracted laterally with the neurovascular bundle) and the pes anserinus tendons/semimembranosus (retracted medially). This allows direct visualization and buttress plating of posteromedial shear fragments.

Question 386

Topic: Lower Extremity Trauma

An 8-year-old boy presents with a painless snapping sensation in his lateral knee. MRI reveals a discoid lateral meniscus of the Wrisberg variant. What distinguishes the Wrisberg variant from the complete and incomplete types of discoid menisci?

. It covers the entire tibial plateau articular surface
. It is always associated with a congenital ACL deficiency
. It lacks the normal posterior meniscotibial capsular attachments
. It has an anomalous attachment to the medial femoral condyle
. It only occurs in the medial compartment of the knee

Correct Answer & Explanation

. It lacks the normal posterior meniscotibial capsular attachments

Explanation

The Wrisberg variant of the discoid meniscus is abnormally mobile because it lacks the normal posterior meniscotibial (coronary ligament) attachments. It is anchored posteriorly only by the meniscofemoral ligament of Wrisberg, leading to a hypermobile, snapping meniscus.

Question 387

Topic: Lower Extremity Trauma

A 25 year-old-male sustains a closed injury shown in Figure A. If a tibial intramedullary nail is placed with the starting points shown (arrows), what subsequent alignment will occur?

. Neutral
. Varus, apex anterior
. Varus, apex posterior
. Valgus, apex anterior
. Valgus, apex posterior

Correct Answer & Explanation

. Neutral

Explanation

In proximal third tibial shaft fractures, due to the deforming forces of the pes anserine and the extensor mechanism, utilizing standard starting points during intramedullary nailing (IMN) will result in a valgus and apex anterior deformity.There are several tips and tricks to avoid subsequent deformity following tibial IMN of a proximal third fracture. One way to avoid deformity is to use a more lateral starting point than normal to ensure nail placement in the true center of the canal, which is more lateral when compared to the tibial plateau.Walker et al. studied 12 cadaveric tibias and inserted a Kirschner wire depending on rotated views of the knee. In order obtain a perfect starting point, a perfect anteroposterior as well as lateral of the knee must be obtained; otherwise, the authors noted that malrotation is bound to occur. With a perfect view, a more lateral starting point correlated with the center of the tibial canal.McConnell et al. studied cadaveric and subsequent radiographic correlation on a lateral knee x-ray to determine the ideal 'safe zone' for the starting point of a tibial nail. This safe zone is more lateral and posterior, when looking at the axial cut of the plateau.Figure A exhibits a proximal third tibia fracture with starting points that are not lateral enough, and too distal (on the lateral view), which will result in apex anterior and valgus deformity.Incorrect answers:

Question 388

Topic: Lower Extremity Trauma

A 42-year-old male sustains a high-energy Schatzker type IV tibial plateau fracture with significant posteromedial articular depression. A posteromedial approach is planned. What is the primary internervous/intermuscular interval utilized in this approach?

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

Correct Answer & Explanation

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

Explanation

The posteromedial approach to the tibial plateau utilizes the interval between the medial head of the gastrocnemius (tibial nerve) and the pes anserinus tendons (femoral/sciatic nerve branches), allowing direct access to the posteromedial articular fragment.

Question 389

Topic: Lower Extremity Trauma
A 28-year-old man reports knee stiffness, swelling, and a constant ache that is worse with activity. Examination reveals an effusion, global tenderness, and warmth to the touch. Flexion is limited to 110 degrees. Figures 48a through 48d show sagittal T1-weighted, sagittal T2-weighted, axial T1-weighted fat-saturated gadolinium, and axial gradient echo MRI scans. Based on these findings, what is the most likely diagnosis?
. Infection
. Arthritis
. Synovial chondromatosis
. Pigmented villonodular synovitis (PVNS)
. Reactive synovitis

Correct Answer & Explanation

. Pigmented villonodular synovitis (PVNS)

Explanation

DISCUSSION: The MRI scans show multiple low-signal intensity lesions scattered throughout the knee, extending posteriorly inferior to the tibial plateau. The low-signal intensity on both the T1- and T2-weighted images, the modest vascularity noted on the gadolinium image, and the “blooming” noted on the gradient echo image (ferrous-laden tissue) are all strongly suggestive of diffuse PVNS. Whereas synovial chondromatosis can present as diffuse masses in the knee, they present as nodule masses that have low T1- and high T2-weighted signal characteristics. REFERENCES: Resnick D (ed): Diagnosis of Bone and Joint Disorders. Philadelphia, PA, WB Saunders, 2002, pp 4241-4252. Sanders TG, Parsons TW: Radiographic imaging of musculoskeletal neoplasia. Cancer Control 2001;8:1-11.

Question 390

Topic: Lower Extremity Trauma

A 28-year-old soccer player experiences sudden lateral ankle pain accompanied by a popping sensation during a rapid cutting maneuver. Physical examination reveals subluxation of the peroneal tendons anterior to the lateral malleolus with resisted eversion. Insufficiency of which of the following structures is most likely responsible?

. Inferior peroneal retinaculum
. Superior peroneal retinaculum
. Calcaneofibular ligament
. Anterior talofibular ligament
. Posterior talofibular ligament

Correct Answer & Explanation

. Inferior peroneal retinaculum

Explanation

The superior peroneal retinaculum (SPR) is the primary restraint preventing anterior subluxation of the peroneal tendons over the lateral malleolus. Injury to the SPR or its fibular attachment ('fleck sign') is the hallmark of peroneal tendon dislocation.

Question 391

Topic: Lower Extremity Trauma
A 45-year-old female pedestrian is struck by a motor vehicle. Radiographs of her right knee demonstrate a displaced fracture of the medial tibial plateau with extension into the metaphysis. The lateral tibial plateau is completely intact. How is this fracture classified according to the Schatzker classification system?
. Schatzker II
. Schatzker III
. Schatzker IV
. Schatzker V
. Schatzker VI

Correct Answer & Explanation

. Schatzker IV

Explanation

The Schatzker classification is widely used for tibial plateau fractures. Schatzker I is a lateral split; II is a lateral split-depression; III is a pure lateral depression. Schatzker IV is a fracture of the medial tibial plateau. Schatzker V is a bicondylar fracture, and Schatzker VI involves metaphyseal-diaphyseal dissociation. This isolated medial plateau fracture is a Schatzker IV. It represents a high-energy injury and is highly associated with peroneal nerve and popliteal artery injuries, as well as knee dislocation variants.

Question 392

Topic: Lower Extremity Trauma

A 28-year-old female sustains a complete tear of her anterior cruciate ligament (ACL) and requires reconstruction. The pivot shift test is positive on examination. Which anatomic structure dynamically causes the visible 'clunk' or reduction of the tibia during the pivot shift maneuver as the knee is transitioned from extension to flexion?

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

Correct Answer & Explanation

. Iliotibial band

Explanation

The pivot shift test demonstrates dynamic rotatory instability of the ACL-deficient knee. Starting in extension with valgus and internal rotation applied, the lateral tibial plateau subluxates anteriorly. As the knee flexes past 20 to 30 degrees, the Iliotibial (IT) band transitions its orientation relative to the instantaneous center of rotation from an extensor to a flexor of the knee. This transition pulls the subluxated lateral tibial plateau posteriorly, creating the sudden reduction or 'clunk' characteristic of a positive pivot shift.

Question 393

Topic: Lower Extremity Trauma

A 40-year-old male manual laborer with symptomatic, isolated medial compartment knee osteoarthritis and a mechanical varus axis of 8 degrees is undergoing a medial opening-wedge high tibial osteotomy (HTO). To achieve optimal offloading of the diseased medial compartment without causing excessive lateral compartment overload, the mechanical axis should be corrected to pass through a specific anatomic coordinate on the tibial plateau. What is the standard target point for the mechanical axis post-correction?

. Exactly at the 50% coordinate (the center of the tibial spines)
. The Fujisawa point, located at approximately 62.5% of the tibial width (measured from medial to lateral)
. The lateral margin of the lateral meniscus (100% of tibial width)
. The medial intercondylar tubercle (40% of tibial width)
. 30% of the tibial width, keeping the axis slightly in the medial compartment

Correct Answer & Explanation

. Exactly at the 50% coordinate (the center of the tibial spines)

Explanation

The goal of a high tibial osteotomy (HTO) for medial compartment osteoarthritis in a varus knee is to shift the mechanical weight-bearing axis laterally to offload the diseased medial cartilage. The widely accepted standard target is the 'Fujisawa point', which is located at 62-62.5% of the tibial width, measured from the medial edge (0%) to the lateral edge (100%). This point lies just lateral to the lateral tibial spine. Overcorrection beyond 65-70% risks rapid degeneration of the lateral compartment, while undercorrection (<50%) fails to adequately relieve medial pain.

Question 394

Topic: Lower Extremity Trauma

A 32-year-old male sustains a midfoot injury while playing football. Weight-bearing radiographs demonstrate a 3 mm diastasis between the medial and middle cuneiforms and a "fleck sign" in the first intermetatarsal space. Which ligament complex is primarily disrupted in this injury?

. Plantar fascia
. Spring ligament (calcaneonavicular ligament)
. Interosseous ligament connecting the medial cuneiform to the second metatarsal base
. Dorsal tarsometatarsal ligament complex
. Bifurcate ligament

Correct Answer & Explanation

. Interosseous ligament connecting the medial cuneiform to the second metatarsal base

Explanation

The Lisfranc ligament is an oblique interosseous ligament that connects the lateral aspect of the medial cuneiform to the medial aspect of the base of the second metatarsal. It is the strongest and most critical ligament stabilizing the tarsometatarsal joint complex. The "fleck sign" is pathognomonic for a Lisfranc injury and represents a bony avulsion of this ligament, usually from the base of the second metatarsal.

Question 395

Topic: Lower Extremity Trauma

A 50-year-old female presents with an acute onset of medial knee pain after a deep squat. MRI reveals a complete radial tear adjacent to the medial meniscus posterior root attachment. What are the biomechanical consequences of this specific injury if left untreated?

. Decreased contact pressure in the medial compartment
. Complete loss of hoop stresses, functionally equivalent to a total medial meniscectomy
. Increased resting tension on the lateral collateral ligament
. Pathologic medial translation of the tibia relative to the femur
. Functional equivalence to an isolated anterior cruciate ligament tear

Correct Answer & Explanation

. Decreased contact pressure in the medial compartment

Explanation

A complete medial meniscus posterior root tear unanchors the meniscus from the tibial plateau. This disrupts the meniscus's ability to convert axial compressive loads into circumferential hoop stresses. Biomechanically, this results in significant meniscal extrusion under load and is equivalent to a total medial meniscectomy, leading to vastly increased peak contact pressures and rapid onset of unicompartmental osteoarthritis.

Question 396

Topic: Lower Extremity Trauma

You are performing a medial opening wedge high tibial osteotomy (HTO) on a 40-year-old active male with medial compartment osteoarthritis and varus malalignment. To optimize load distribution and long-term survivorship of the osteotomy, where should the postoperative mechanical axis pass on the tibial plateau (measured from medial to lateral)?

. 0% (Extreme medial edge)
. 30% (Medial compartment)
. 62% (Slightly lateral to the center of the plateau)
. 85% (Lateral compartment)
. 100% (Extreme lateral edge)

Correct Answer & Explanation

. 62% (Slightly lateral to the center of the plateau)

Explanation

The target for correction in an HTO is the Fujisawa point, which is located at approximately 62% of the tibial plateau width from medial to lateral. This transfers the mechanical axis slightly into the healthy lateral compartment, relieving medial stress.

Question 397

Topic: Lower Extremity Trauma

A 42-year-old man sustains a highly comminuted Schatzker VI tibial plateau fracture. During surgical approach and reduction, excessive traction is placed on the lateral tissues. Postoperatively, the patient has an inability to extend his great toe and loss of sensation over the first web space. Which specific nerve branch is most likely injured?

. Deep peroneal nerve
. Superficial peroneal nerve
. Tibial nerve
. Sural nerve
. Saphenous nerve

Correct Answer & Explanation

. Deep peroneal nerve

Explanation

The deep peroneal nerve innervates the extensor hallucis longus (great toe extension) and provides sensation to the first dorsal web space. It is vulnerable to traction injury or compression during lateral approaches to the proximal tibia.

Question 398

Topic: Lower Extremity Trauma

A 40-year-old man presents with a Schatzker IV tibial plateau fracture featuring a displaced posteromedial fragment. The surgeon plans an open reduction and internal fixation via a posteromedial approach. Which anatomic interval is classically utilized for this approach?

. Between the medial head of the gastrocnemius and the pes anserinus
. Between the lateral head of the gastrocnemius and the soleus
. Between the semimembranosus and semitendinosus
. Between the tibialis anterior and extensor hallucis longus
. Between the biceps femoris and the iliotibial band

Correct Answer & Explanation

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

Explanation

The posteromedial approach to the tibial plateau typically exploits the interval between the medial head of the gastrocnemius (retracted laterally/posteriorly) and the pes anserinus (retracted medially/anteriorly). This allows direct access to buttress posteromedial shear fragments.

Question 399

Topic: Lower Extremity Trauma

making a cut toward the ball. He felt a pop and his leg gave way. During physical examination, as the knee is moved from full extension into flexion with an internal rotation and valgus force, you notice a “clunk” within the knee. What is the most likely biomechanical basis for the “clunk”?

. In extension with internal rotation/valgus force, the medial tibial plateau is subluxated; with flexion, the medial tibial plateau reduces
. In extension with internal rotation/valgus force, the medial tibial plateau is reduced; with flexion, the medial tibial plateau subluxates
. In extension with internal rotation/valgus force, the lateral tibial plateau is reduced; with flexion, the lateral plateau subluxates
. In extension with internal rotation/valgus force, the lateral tibial plateau is subluxated; with flexion, the lateral plateau reduces

Correct Answer & Explanation

. In extension with internal rotation/valgus force, the medial tibial plateau is subluxated; with flexion, the medial tibial plateau reduces

Explanation

DISCUSSIONThis patient sustained an isolated anterior cruciate ligament (ACL) injury based upon the mechanism described and examination findings. The finding that produces the “clunk” is the pivot-shift maneuver, which is positive in a knee with an incompetent ACL. With an ACL-deficient knee in full extension and internal rotation, the lateral tibial plateau subluxates anteriorly. As the knee is flexed, the lateral tibial plateau slides posteriorly into a reduced position, causing an audible clunk. Response 4 correctly describes the pathomechanics that result in the audible clunk heard during the pivot-shift maneuver. Responses 1 and 2 are incorrect because they describe the medial tibial plateau, which is not part of the pathomechanics of the pivot shift. Response 3 is incorrect because in extension, the lateral tibial plateau is subluxated, not reduced.

Question 400

Topic: Lower Extremity Trauma

When utilizing suture button fixation for an ankle syndesmotic injury, what is a primary biomechanical advantage compared to traditional rigid trans-syndesmotic screw fixation?

. Higher maximum load to failure in external rotation forces
. Elimination of the need for an intact anterior inferior tibiofibular ligament
. Allowance of physiological fibular motion and rotation within the incisura
. Decreased risk of superficial peroneal nerve injury during placement
. Capability to rigidly over-compress a widened medial clear space

Correct Answer & Explanation

. Allowance of physiological fibular motion and rotation within the incisura

Explanation

Suture button fixation for syndesmotic injuries allows for physiological micromotion and fibular rotation within the incisura during ankle dorsiflexion. It also mitigates the need for routine hardware removal.

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