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2. Trauma MCQs

Practice Set 409 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 8161

Topic: 2. Trauma

A 45-year-old male sustains an open grade IIIB tibial shaft fracture following a motorcycle collision. The surgeon plans to use an intramedullary nail along with a biological adjuvant to promote bone healing. Which of the following is an FDA-approved osteoinductive agent specifically indicated for acute open tibial shaft fractures treated with an intramedullary nail?

. Platelet-derived growth factor (PDGF)
. Recombinant human bone morphogenetic protein-7 (rhBMP-7)
. Transforming growth factor-beta (TGF-beta)
. Recombinant human bone morphogenetic protein-2 (rhBMP-2)
. Fibroblast growth factor (FGF)

Correct Answer & Explanation

. Platelet-derived growth factor (PDGF)

Explanation

Recombinant human bone morphogenetic protein-2 (rhBMP-2) is a potent osteoinductive agent that has FDA approval for use in acute open tibial shaft fractures treated with an intramedullary nail, as well as for single-level anterior lumbar interbody fusion (ALIF). rhBMP-7 (also known as osteogenic protein-1 or OP-1) was previously utilized under a Humanitarian Device Exemption for recalcitrant tibial nonunions.

Question 8162

Topic: 2. Trauma

A 35-year-old patient undergoes plate fixation for a diaphyseal humerus fracture. During the procedure, the surgeon wishes to maximize the biomechanical strength of the construct. The pullout strength of a cortical screw is most directly proportional to which of the following screw parameters?

. Core diameter of the screw
. Pitch of the screw thread
. Length of the screw head
. Inner diameter of the thread
. Outer diameter of the screw thread

Correct Answer & Explanation

. Core diameter of the screw

Explanation

Screw pullout strength dictates the resistance of a screw to axial loading forces. It is directly proportional to the outer (major) diameter of the screw thread, the length of thread engagement in the bone, and the shear strength of the surrounding bone. It is inversely proportional to the thread pitch (the distance between adjacent threads). The core (minor) diameter determines the overall torsional and bending strength of the screw, rather than its pullout strength.

Question 8163

Topic: Lower Extremity Trauma

If a surgeon increases the diameter of a solid titanium intramedullary nail from 10 mm to 12 mm, the bending rigidity of the nail increases by a factor of approximately:

. 1.2
. 1.4
. 1.7
. 2.1
. 2.5

Correct Answer & Explanation

. 1.2

Explanation

The bending rigidity of a solid cylindrical object is proportional to its area moment of inertia, which is calculated as I = (π * r^4) / 4. Therefore, bending rigidity is proportional to the radius (or diameter) to the fourth power. Increasing the diameter from 10 to 12 mm represents a 1.2-fold increase. The new bending rigidity is (1.2)^4, which is 2.0736, or approximately a 2.1-fold increase.

Question 8164

Topic: 2. Trauma

The pull-out strength of a cortical screw used for fracture fixation is primarily determined by its thread design and the surrounding bone quality. Which of the following modifications to a screw's design will most effectively increase its pull-out strength?

. Decreasing the outer diameter
. Increasing the inner (root) diameter
. Decreasing the thread pitch
. Increasing the length of the unthreaded shaft
. Decreasing the thread depth

Correct Answer & Explanation

. Decreasing the outer diameter

Explanation

Pullout strength of a screw is directly proportional to its outer diameter, the length of thread engagement, and the shear strength of the bone; it is inversely proportional to the thread pitch. Decreasing the thread pitch increases the number of threads engaged in the bone per unit of length, thereby increasing pull-out strength. Increasing the inner diameter (root diameter) increases the bending strength of the screw but decreases the thread depth (if the outer diameter remains constant), which subsequently decreases pull-out strength.

Question 8165

Topic: 2. Trauma

Regarding the blood supply to the adult femoral head, which artery is considered the most critical contributor following physeal closure, particularly in the event of a femoral neck fracture?

. Medial circumflex femoral artery
. Lateral circumflex femoral artery
. Artery of the ligamentum teres (foveal artery)
. Superior gluteal artery
. Inferior gluteal artery

Correct Answer & Explanation

. Medial circumflex femoral artery

Explanation

In the adult, the medial circumflex femoral artery (MCFA), a branch of the deep femoral artery, is the most critical contributor to the blood supply of the femoral head. It sends retinacular branches (especially the posterior and superior retinacular arteries) that ascend the femoral neck and supply the femoral head. Fractures of the femoral neck, particularly displaced ones, commonly disrupt these retinacular vessels, leading to a high risk of avascular necrosis. The lateral circumflex femoral artery plays a lesser role. The artery of the ligamentum teres is significant in childhood but becomes less dominant in adulthood, providing a relatively minor contribution. Superior and inferior gluteal arteries supply the surrounding muscles but not directly the femoral head.

Question 8166

Topic: 2. Trauma

A 25-year-old male sustains a fall onto an outstretched hand, resulting in a scaphoid fracture. The surgeon explains the risk of nonunion and avascular necrosis. Which of the following describes the most common and clinically significant blood supply pattern to the scaphoid?

. Branches from the anterior interosseous artery entering the distal pole
. Volar branches from the radial artery entering the proximal pole
. Dorsal branches from the radial artery entering the distal pole and waist, with retrograde flow to the proximal pole
. Branches from the ulnar artery supplying the entire bone directly
. Medial and lateral circumflex arteries supplying the waist

Correct Answer & Explanation

. Branches from the anterior interosseous artery entering the distal pole

Explanation

The scaphoid's blood supply is highly precarious. The most common and clinically significant pattern involves dorsal branches from the radial artery entering the distal pole and waist of the scaphoid. These vessels then proceed to supply the proximal pole via intraosseous retrograde flow. This pattern explains why fractures of the waist or proximal pole often disrupt the blood supply to the proximal fragment, leading to a high incidence of avascular necrosis and nonunion. Volar branches are less significant. The ulnar artery and circumflex arteries do not directly supply the scaphoid.

Question 8167

Topic: Pelvic & Acetabular Trauma

The sacroiliac joint is a strong, weight-bearing joint stabilized by numerous ligaments. Which of the following ligaments is considered the strongest and most important for stabilizing the sacroiliac joint, restricting anterior and inferior rotation of the sacrum?

. Sacrospinous ligament
. Sacrotuberous ligament
. Iliolumbar ligament
. Interosseous sacroiliac ligament
. Posterior sacroiliac ligament

Correct Answer & Explanation

. Sacrospinous ligament

Explanation

The sacroiliac (SI) joint is stabilized by an intricate complex of ligaments. The interosseous sacroiliac ligament is considered the strongest and most important ligament for SI joint stability. It consists of multiple short, strong fibers that fill the irregular space between the sacral and iliac tuberosities, connecting them firmly. It effectively resists anterior and inferior rotation of the sacrum relative to the ilium. The posterior sacroiliac ligaments reinforce the posterior aspect, the iliolumbar ligament connects L5 to the ilium, and the sacrospinous and sacrotuberous ligaments are extrinsic ligaments of the pelvis, providing less direct SI joint stability.

Question 8168

Topic: 2. Trauma

A 42-year-old male presents with inability to extend his fingers and thumb at the MCP joints following a Monteggia fracture-dislocation. Wrist extension is preserved but occurs with strong radial deviation. Surgical exploration of the posterior interosseous nerve (PIN) is planned. The most common site of PIN compression is the Arcade of Frohse. Which of the following defines this anatomic structure?

. The fibrous proximal edge of the superficial head of the supinator
. The tendinous leading edge of the extensor carpi radialis brevis
. The fascial band distal to the brachioradialis insertion
. The recurrent radial artery leash (Leash of Henry)
. The fibrous band between the two heads of the pronator teres

Correct Answer & Explanation

. The fibrous proximal edge of the superficial head of the supinator

Explanation

The Arcade of Frohse is formed by the thickened, fibrous proximal edge of the superficial head of the supinator muscle. It is the most common site of entrapment for the posterior interosseous nerve (PIN), leading to PIN syndrome, which classically presents with weakness in thumb and finger extension and radial deviation of the wrist during extension (due to ECRB/ECRL preservation and ECU weakness).

Question 8169

Topic: 2. Trauma

A 28-year-old skier sustains a severe external rotation ankle injury. MRI demonstrates a complete rupture of the anterior inferior tibiofibular ligament (AITFL) with an associated bony avulsion from its tibial attachment. What is the eponymous name for this specific anterolateral tibial avulsion fragment?

. Wagstaffe tubercle
. Chaput tubercle
. Volkmann tubercle
. Cedell tubercle
. Gerdy's tubercle

Correct Answer & Explanation

. Wagstaffe tubercle

Explanation

The Tillaux-Chaput tubercle is the bony prominence on the anterolateral distal tibia where the anterior inferior tibiofibular ligament (AITFL) attaches. An avulsion here is a Tillaux-Chaput fracture. The Wagstaffe (or Le Fort-Wagstaffe) tubercle is the fibular attachment of the AITFL. The Volkmann tubercle is the posterior tibial attachment of the posterior inferior tibiofibular ligament (PITFL).

Question 8170

Topic: 2. Trauma

A surgeon is utilizing the volar (Henry) approach to plate a proximal third radial shaft fracture. To safely expose the proximal radius while protecting the posterior interosseous nerve (PIN), the supinator muscle must be elevated. What is the safest and most anatomically sound method to manage the supinator insertion during this approach?

. Detach it from its ulnar origin and reflect it laterally
. Detach it from its radial insertion with the forearm in full supination
. Detach it from its radial insertion with the forearm in full pronation
. Split the muscle fibers longitudinally in the mid-substance
. Elevate it from the lateral epicondyle en masse

Correct Answer & Explanation

. Detach it from its ulnar origin and reflect it laterally

Explanation

During the volar (Henry) approach to the proximal radius, the forearm should be placed in full supination. This action displaces the posterior interosseous nerve (PIN) laterally and away from the surgical field. The supinator is then detached from its radial insertion and reflected laterally, protecting the PIN within the muscle substance.

Question 8171

Topic: 2. Trauma

A trauma surgeon is performing an open reduction and internal fixation of a complex subtrochanteric femur fracture. While clearing the linea aspera for plate application, meticulous hemostasis is required. Which vascular structure runs distally in the thigh in close proximity to the posterior femur and provides the major perforating branches at risk during this exposure?

. Superficial femoral artery
. Profunda femoris artery
. Obturator artery
. Medial circumflex femoral artery
. Lateral circumflex femoral artery

Correct Answer & Explanation

. Superficial femoral artery

Explanation

The profunda femoris (deep femoral) artery travels distally in the thigh posterior to the adductor longus and anterior to the adductor brevis and magnus. It provides multiple perforating branches that pierce the adductor magnus near its insertion on the linea aspera. These branches and the main trunk are at high risk of injury during posterior stripping or errant drilling at the linea aspera.

Question 8172

Topic: Pelvic & Acetabular Trauma

During an anterior intrapelvic (modified Stoppa) approach for the fixation of an acetabular fracture, the surgeon must identify and protect or ligate the 'corona mortis' to prevent life-threatening hemorrhage. This structure typically represents a vascular anastomosis between which of the following systems?

. Internal pudendal and external pudendal arteries
. Superior gluteal and inferior gluteal arteries
. Obturator and external iliac (or inferior epigastric) vessels
. Iliolumbar and deep circumflex iliac vessels
. Medial femoral circumflex and obturator arteries

Correct Answer & Explanation

. Internal pudendal and external pudendal arteries

Explanation

The corona mortis ('crown of death') is a recognized vascular anastomosis between the obturator vessels (internal iliac system) and the inferior epigastric or external iliac vessels. It is located on the posterior aspect of the superior pubic ramus, on average 5-6 cm from the pubic symphysis. Iatrogenic injury during approaches to the acetabulum or anterior pelvic ring can cause rapid, severe hemorrhage that is difficult to control.

Question 8173

Topic: 2. Trauma

A 25-year-old distance runner develops chronic exertional compartment syndrome requiring fasciotomy. The surgeon plans to release the deep posterior compartment of the lower leg. Which of the following structures is located within this anatomic compartment?

. Peroneus brevis
. Tibialis anterior
. Extensor hallucis longus
. Flexor hallucis longus
. Sural nerve

Correct Answer & Explanation

. Peroneus brevis

Explanation

The deep posterior compartment of the leg contains the flexor hallucis longus, flexor digitorum longus, tibialis posterior, as well as the posterior tibial artery, vein, and tibial nerve. The peroneus brevis is in the lateral compartment. The tibialis anterior and EHL are in the anterior compartment, while the sural nerve is superficial.

Question 8174

Topic: 2. Trauma

A 19-year-old man presents with a displaced fracture of the scaphoid waist. He is at high risk for avascular necrosis of the proximal pole due to retrograde blood flow. The primary intraosseous blood supply to the proximal scaphoid enters at which of the following anatomic locations?

. Volar proximal pole
. Volar distal pole
. Dorsal ridge
. Scaphoid tubercle
. Scapholunate ligament insertion

Correct Answer & Explanation

. Volar proximal pole

Explanation

The primary blood supply to the scaphoid is derived from the radial artery. Approximately 70-80% of the scaphoid (including the proximal pole and waist) is supplied by the dorsal carpal branch of the radial artery, which enters the scaphoid along its dorsal ridge. Because these vessels enter distally and flow proximally (retrograde flow), waist fractures frequently interrupt blood flow to the proximal pole.

Question 8175

Topic: Pelvic & Acetabular Trauma

During an ilioinguinal approach for an anterior column acetabular fracture, a vascular anastomosis connecting the obturator and external iliac (or inferior epigastric) vessels is encountered coursing over the superior pubic ramus. Injury to this "corona mortis" causes significant hemorrhage. At what average distance from the pubic symphysis does this structure typically lie?

. 1 to 2 cm
. 5 to 7 cm
. 9 to 11 cm
. 12 to 14 cm
. 15 to 17 cm

Correct Answer & Explanation

. 1 to 2 cm

Explanation

The corona mortis is a vascular connection between the obturator and external iliac or inferior epigastric vessels. It crosses the superior pubic ramus at an average distance of 5 to 7 cm (typically about 6 cm) lateral to the pubic symphysis. It must be carefully identified and ligated during anterior approaches to the pelvis and acetabulum to prevent massive, life-threatening bleeding.

Question 8176

Topic: 2. Trauma

A 21-year-old cross-country runner undergoes a four-compartment fasciotomy for chronic exertional compartment syndrome (CECS) using a double-incision technique. Post-operatively, the patient reports persistent deep leg pain during exercise. Failure to adequately release which muscle's distinct fascial envelope within the deep posterior compartment is the most likely cause of these persistent symptoms?

. Flexor hallucis longus
. Tibialis posterior
. Flexor digitorum longus
. Popliteus
. Soleus

Correct Answer & Explanation

. Flexor hallucis longus

Explanation

The deep posterior compartment of the leg contains the flexor hallucis longus, flexor digitorum longus, and the tibialis posterior. The tibialis posterior muscle often has its own distinct, rigid fascial envelope deeply situated between the tibia and fibula. During a medial fasciotomy incision, if the surgeon releases the superficial fascia of the deep posterior compartment but fails to dissect deeply enough to incise the specific fascial investment of the tibialis posterior, the patient may continue to suffer from CECS.

Question 8177

Topic: 2. Trauma

A surgeon is placing screws into the acetabulum for a highly comminuted fracture utilizing a reconstruction plate. According to Wasielewski's quadrant system, placement of a screw in the anteroinferior quadrant places which of the following structures at highest risk of injury?

. Sciatic nerve
. External iliac artery
. Internal pudendal artery
. Superior gluteal nerve
. Obturator nerve

Correct Answer & Explanation

. Sciatic nerve

Explanation

Wasielewski's quadrant system for the acetabulum defines safe and dangerous zones for screw placement. The anteroinferior quadrant contains the obturator nerve and vessels. The posterosuperior quadrant is generally considered the 'safe zone' for screw placement (longest available bone stock, though the sciatic nerve is posterior to it). The posteroinferior quadrant places the internal pudendal and inferior gluteal vessels at risk. The anterosuperior quadrant places the external iliac vessels at risk.

Question 8178

Topic: 2. Trauma

An anterolateral approach to the distal tibia is chosen for the fixation of a complex pilon fracture. The incision is made longitudinally in line with the fourth ray. Which of the following neurological structures is at greatest risk of iatrogenic injury during the superficial soft-tissue dissection of this approach?

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

Correct Answer & Explanation

. Sural nerve

Explanation

The superficial peroneal nerve is highly vulnerable during the anterolateral approach to the distal tibia and ankle. It typically pierces the deep fascia of the leg 10-15 cm proximal to the lateral malleolus and branches into the medial and intermediate dorsal cutaneous nerves, crossing the surgical field. Careful superficial dissection is necessary to identify and protect these branches.

Question 8179

Topic: 2. Trauma

A surgeon is performing a posterolateral approach to the proximal tibia for a highly comminuted tibial plateau fracture. During the deep dissection, the popliteus muscle is retracted proximally and the soleus muscle is retracted distally. Which of the following neurovascular structures is at the greatest risk of injury at the inferior border of the popliteus muscle during this specific maneuver?

. Posterior tibial artery
. Anterior tibial artery
. Common peroneal nerve
. Inferior lateral genicular artery
. Tibial nerve

Correct Answer & Explanation

. Posterior tibial artery

Explanation

During the posterolateral approach to the proximal tibia, the anterior tibial artery is at high risk. It branches from the popliteal artery and passes anteriorly through the oval aperture at the proximal aspect of the interosseous membrane. This anatomical transition occurs exactly at the distal (inferior) border of the popliteus muscle. Retracting the popliteus proximally and the soleus distally places tension on these vessels, making the anterior tibial artery highly vulnerable to iatrogenic injury if dissection strays too far distally or if retractors are placed carelessly.

Question 8180

Topic: 2. Trauma

A 32-year-old marathon runner presents with chronic exertional compartment syndrome of the lower leg. Intracompartmental pressure testing reveals isolated elevation within the deep posterior compartment. Which of the following major structures courses through this specific compartment?

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

Correct Answer & Explanation

. Superficial peroneal nerve

Explanation

The deep posterior compartment of the leg contains the tibialis posterior, flexor digitorum longus, and flexor hallucis longus muscles. The neurovascular bundle running through this compartment includes the tibial nerve and the posterior tibial artery and vein.

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