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2. Trauma MCQs

Practice Set 392 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 7821

Topic: 2. Trauma

Which of the following forms of fracture fixation relies primarily on intramembranous ossification and cutting cones for bone healing, without the formation of a visible fracture callus?

. Intramedullary nailing of a femur fracture
. Bridge plating of a comminuted tibia fracture
. Compression plating of a transverse radius fracture
. External fixation of a pilon fracture
. Casting of a distal radius fracture

Correct Answer & Explanation

. Intramedullary nailing of a femur fracture

Explanation

Compression plating provides absolute stability and abolishes interfragmentary strain, leading to primary bone healing. This process relies on direct Haversian remodeling via cutting cones rather than secondary callus formation.

Question 7822

Topic: 2. Trauma

When applying a bridge plate to a comminuted diaphyseal fracture, increasing the 'working length' of the construct has which of the following biomechanical effects?

. Increases the torsional stiffness of the construct
. Decreases the axial stiffness of the construct
. Increases the overall strain at the fracture site
. Increases the risk of screw pullout
. Decreases the micromotion at the fracture site

Correct Answer & Explanation

. Increases the torsional stiffness of the construct

Explanation

Working length is the distance between the innermost screws on either side of a fracture. Increasing the working length decreases the overall stiffness of the construct, which distributes strain and permits controlled micromotion for secondary bone healing.

Question 7823

Topic: Lower Extremity Trauma

According to the principles of biomechanics, the bending rigidity of a solid cylindrical intramedullary nail is proportional to its radius raised to which power?

. 1
. 2
. 3
. 4
. 5

Correct Answer & Explanation

. 1

Explanation

The area moment of inertia, which determines resistance to bending, is proportional to the radius to the fourth power (r^4) for a solid cylinder. A small increase in nail diameter significantly increases its bending stiffness.

Question 7824

Topic: 2. Trauma

In bridge plating of a comminuted diaphyseal fracture, increasing the 'working length' of the construct results in which of the following biomechanical outcomes?

. Increased axial stiffness
. Decreased axial stiffness
. Increased primary bone healing
. Decreased interfragmentary movement
. Increased risk of screw pull-out

Correct Answer & Explanation

. Increased axial stiffness

Explanation

The working length of a plate is the distance between the two innermost screws spanning the fracture. Increasing the working length makes the construct more flexible, decreasing axial stiffness and allowing more interfragmentary motion to stimulate secondary bone healing.

Question 7825

Topic: 2. Trauma

A 14-year-old male athlete presents with sudden onset of severe groin pain after forcefully kicking a soccer ball. Radiographs reveal an avulsion fracture of the lesser trochanter. Which of the following muscles is responsible for this injury?

. Sartorius
. Rectus femoris
. Iliopsoas
. Adductor longus
. Hamstrings

Correct Answer & Explanation

. Sartorius

Explanation

The iliopsoas muscle inserts onto the lesser trochanter and is responsible for avulsion fractures at this site, most commonly seen in adolescents during forceful hip flexion.

Question 7826

Topic: Pelvic & Acetabular Trauma

In a patient with a posterior pelvic ring disruption, which ligament is considered the primary and strongest stabilizer against vertical shear forces?

. Anterior sacroiliac ligament
. Sacrospinous ligament
. Sacrotuberous ligament
. Interosseous sacroiliac ligament
. Iliolumbar ligament

Correct Answer & Explanation

. Anterior sacroiliac ligament

Explanation

The interosseous sacroiliac ligament, part of the posterior sacroiliac ligament complex, is the strongest ligament in the body and provides the primary resistance against vertical shear forces across the sacroiliac joint.

Question 7827

Topic: Pelvic & Acetabular Trauma

In evaluating a patient with a pelvic ring injury, the presence of an open book pelvis (APC II or III) implies failure of the symphysis pubis and the anterior sacroiliac ligaments. Which pelvic ligament, if intact, prevents pure vertical displacement and distinguishes an APC II from an APC III injury?

. Posterior sacroiliac ligament
. Sacrospinous ligament
. Anterior sacroiliac ligament
. Sacrotuberous ligament
. Iliolumbar ligament

Correct Answer & Explanation

. Posterior sacroiliac ligament

Explanation

In an APC II injury, the anterior SI ligaments, sacrospinous, and sacrotuberous ligaments are torn, allowing external rotation. The intact posterior sacroiliac ligaments prevent vertical translation and differentiate it from an APC III injury.

Question 7828

Topic: 2. Trauma

An adolescent water skier sustains a sudden, forceful hip flexion with knee extension, resulting in an ischial tuberosity avulsion fracture. Which of the following muscles shares a conjoint tendon origin at this site?

. Semimembranosus and short head of biceps femoris
. Semitendinosus and long head of biceps femoris
. Adductor magnus and semimembranosus
. Gracilis and semitendinosus
. Sartorius and rectus femoris

Correct Answer & Explanation

. Semimembranosus and short head of biceps femoris

Explanation

The long head of the biceps femoris and the semitendinosus form a conjoint tendon that originates on the ischial tuberosity. The semimembranosus also originates here but has a distinct, more lateral footprint.

Question 7829

Topic: Pelvic & Acetabular Trauma

In evaluating an acetabular fracture on an anteroposterior pelvic radiograph, the ilioischial line is disrupted. This radiographic landmark represents which anatomic structure of the acetabulum?

. Anterior column
. Posterior column
. Anterior wall
. Posterior wall
. Acetabular dome

Correct Answer & Explanation

. Anterior column

Explanation

The ilioischial line is a radiographic landmark seen on an AP pelvis radiograph that represents the posterior column of the acetabulum. The iliopectineal line represents the anterior column.

Question 7830

Topic: 2. Trauma

In a 65-year-old patient sustaining a displaced intracapsular femoral neck fracture, the primary blood supply to the femoral head is typically disrupted. Which of the following arteries provides the majority of the blood supply to the adult femoral head?

. Ligamentum teres artery
. Lateral circumflex femoral artery
. Medial circumflex femoral artery
. Inferior gluteal artery
. Obturator artery

Correct Answer & Explanation

. Ligamentum teres artery

Explanation

The lateral epiphyseal branches of the medial circumflex femoral artery (MCFA) are the predominant blood supply to the adult femoral head. Disruption of these vessels in displaced femoral neck fractures leads to high rates of avascular necrosis.

Question 7831

Topic: Pelvic & Acetabular Trauma

A patient with a complex pelvic ring injury presents with profound weakness in hip adduction and an area of decreased sensation over the distal medial thigh. An injury to the obturator nerve is suspected. Which of the following adductor muscles will likely retain partial function due to dual innervation?

. Adductor longus
. Gracilis
. Adductor brevis
. Adductor magnus
. Obturator externus

Correct Answer & Explanation

. Adductor longus

Explanation

The adductor magnus is dually innervated by both the obturator nerve and the tibial division of the sciatic nerve (hamstring portion). Therefore, it retains partial function even with a complete obturator nerve palsy.

Question 7832

Topic: Pelvic & Acetabular Trauma

A 24-year-old male sustains a vertical shear pelvic fracture following a fall from height. Which ligamentous complex provides the most significant resistance to vertical displacement of the hemipelvis?

. Sacrospinous ligament
. Sacrotuberous ligament
. Anterior sacroiliac ligament
. Posterior sacroiliac ligament complex
. Iliolumbar ligament

Correct Answer & Explanation

. Sacrospinous ligament

Explanation

The posterior sacroiliac ligament complex, particularly the dense interosseous ligaments, is the strongest in the pelvis and provides the primary restraint against vertical shear forces. The sacrotuberous and sacrospinous ligaments primarily resist rotational forces.

Question 7833

Topic: 2. Trauma

During a posterior (Kocher-Langenbeck) approach to the hip for a posterior wall acetabular fracture, the short external rotators are sharply detached. The superior border of which muscle must be preserved intact to protect the deep branch of the medial circumflex femoral artery?

. Piriformis
. Superior gemellus
. Obturator internus
. Inferior gemellus
. Quadratus femoris

Correct Answer & Explanation

. Piriformis

Explanation

The deep branch of the medial circumflex femoral artery (MCFA) courses anterior to the quadratus femoris. Protecting the superior border of the quadratus femoris or leaving a cuff of the obturator externus intact prevents iatrogenic injury to the femoral head's primary blood supply.

Question 7834

Topic: 2. Trauma

A 16-year-old sprinter presents with acute buttock pain after feeling a 'pop' while running. Radiographs reveal an avulsion fracture of the ischial tuberosity. Which of the following muscles originates at this anatomical site?

. Rectus femoris
. Sartorius
. Biceps femoris (long head)
. Gluteus maximus
. Iliopsoas

Correct Answer & Explanation

. Rectus femoris

Explanation

The ischial tuberosity is the origin of the hamstring muscle complex, which includes the long head of the biceps femoris, semitendinosus, and semimembranosus. Sudden forceful contraction can cause avulsion of this apophysis in adolescents.

Question 7835

Topic: Pelvic & Acetabular Trauma

During surgical exposure of the posterior pelvic ring, the pudendal nerve must be protected. What is the anatomic path of the pudendal nerve relative to the sacrospinous and sacrotuberous ligaments?

. It passes posterior to both ligaments
. It passes anterior to both ligaments
. It passes between the sacrospinous and sacrotuberous ligaments
. It pierces the sacrotuberous ligament directly
. It runs strictly superior to the sacrospinous ligament

Correct Answer & Explanation

. It passes posterior to both ligaments

Explanation

The pudendal nerve exits the greater sciatic foramen, crosses posterior to the sacrospinous ligament, and enters the lesser sciatic foramen anterior to the sacrotuberous ligament. Thus, it passes between the two ligaments.

Question 7836

Topic: Upper Extremity Trauma

The coracoclavicular ligament complex is crucial for acromioclavicular joint stability. Which of the following describes the specific biomechanical function of the conoid ligament?

. Primary restraint to superior displacement of the clavicle
. Primary restraint to posterior displacement of the clavicle
. Resists axial compression of the AC joint
. Attaches anterolateral to the trapezoid ligament
. Primary restraint to anterior displacement of the clavicle

Correct Answer & Explanation

. Primary restraint to superior displacement of the clavicle

Explanation

The conoid ligament is the primary restraint to superior clavicular displacement. The trapezoid ligament is positioned anterolateral to the conoid and provides resistance against posterior translation and axial compression.

Question 7837

Topic: Lower Extremity Trauma

The lateral meniscus is structurally and kinematically distinct from the medial meniscus. Which of the following is a defining anatomical feature of the lateral meniscus?

. It is firmly attached to the lateral collateral ligament
. It has a larger radius of curvature than the medial meniscus
. It is more rigidly fixed to the tibial plateau than the medial meniscus
. It receives attachments from the meniscofemoral ligaments of Humphrey and Wrisberg
. Its posterior horn acts as the primary wedge against anterior tibial translation

Correct Answer & Explanation

. It is firmly attached to the lateral collateral ligament

Explanation

The lateral meniscus is highly mobile, O-shaped, and is physically separated from the LCL by the popliteus tendon. It receives capsular attachments from the anterior (Humphrey) and posterior (Wrisberg) meniscofemoral ligaments.

Question 7838

Topic: Pelvic & Acetabular Trauma

In an anteroposterior compression (APC) pelvic ring injury, progressive disruption of ligaments leads to widening of the symphysis. Which sacroiliac (SI) ligament is the strongest and typically tears last, differentiating an APC-II from an APC-III injury?

. Anterior sacroiliac ligament
. Sacrospinous ligament
. Sacrotuberous ligament
. Posterior sacroiliac ligament
. Iliolumbar ligament

Correct Answer & Explanation

. Anterior sacroiliac ligament

Explanation

The posterior sacroiliac ligament complex is the strongest ligamentous restraint of the pelvic ring. It remains intact in rotationally unstable but vertically stable APC-II injuries, but is torn in globally unstable APC-III injuries.

Question 7839

Topic: Upper Extremity Trauma

In an acromioclavicular (AC) joint dislocation, the coracoclavicular (CC) ligaments are disrupted. Which of the following describes the correct anatomy and primary biomechanical function of the conoid ligament?

. It is located lateral to the trapezoid and primarily resists anterior clavicular translation
. It is located medial to the trapezoid and primarily resists superior clavicular translation
. It is located lateral to the trapezoid and primarily resists posterior clavicular translation
. It is located medial to the trapezoid and primarily resists anterior clavicular translation
. It is composed of a single band that inserts on the anterior border of the clavicle

Correct Answer & Explanation

. It is located lateral to the trapezoid and primarily resists anterior clavicular translation

Explanation

The conoid ligament is the medial and posterior component of the CC ligament complex. It acts as the primary restraint to superior translation of the distal clavicle.

Question 7840

Topic: 2. Trauma

Intramedullary nailing of a diaphyseal femur fracture profoundly affects local hemodynamics. In an intact long bone, the normal direction of arterial blood flow within the diaphyseal cortex is primarily:

. Centripetal (from periosteum to endosteum)
. Centrifugal (from endosteum to periosteum)
. Purely longitudinal from the metaphysis
. Transverse from the muscle attachments
. Completely randomized within the Haversian systems

Correct Answer & Explanation

. Centripetal (from periosteum to endosteum)

Explanation

In the mature, uninjured diaphyseal cortex, the high-pressure nutrient artery system drives blood flow centrifugally from the endosteum to the periosteum. Following injury or intramedullary reaming, this flow temporarily reverses to a centripetal direction as the periosteal supply takes over.

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