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2. Trauma MCQs

Practice Set 293 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 5841

Topic: 2. Trauma

A candidate is asked about the 'stress shielding' phenomenon in orthopedic implants. Which statement best describes this concept?

. The implant protects the bone from excessive stress, leading to bone hypertrophy.
. The implant fails to bear sufficient load, transferring all stress to the bone.
. The implant bears a disproportionately large share of the load, leading to bone resorption and atrophy.
. The implant corrodes due to mechanical stress, releasing metal ions.
. The implant shields the surrounding soft tissues from inflammatory responses.

Correct Answer & Explanation

. The implant bears a disproportionately large share of the load, leading to bone resorption and atrophy.

Explanation

Stress shielding occurs when an orthopedic implant carries a large proportion of the mechanical load, 'shielding' the adjacent bone from its normal physiological stress. According to Wolff's Law, bone remodels in response to mechanical stress. When bone is shielded from stress, it responds by resorbing and atrophying, leading to decreased bone density around the implant. This can potentially compromise implant longevity or lead to periprosthetic fracture.

Question 5842

Topic: 2. Trauma

Which of the following describes the purpose of 'locking plates' in fracture fixation?

. To provide absolute stability through compression.
. To function as an internal fixator, creating an angular stable construct.
. To allow dynamic compression across the fracture site.
. To promote primary bone healing exclusively.
. To facilitate early full weight-bearing in all fracture patterns.

Correct Answer & Explanation

. To function as an internal fixator, creating an angular stable construct.

Explanation

Locking plates function as internal fixators, creating an angular stable construct. The screws lock into the plate, providing a fixed-angle device that does not rely on plate-bone compression for stability. This allows them to effectively 'splint' the fracture, preserving periosteal blood supply and promoting relative stability and secondary bone healing. They do not provide absolute stability through compression (that's conventional plating) and don't necessarily facilitate early full weight-bearing in all patterns. They are suitable for comminuted fractures or osteoporotic bone.

Question 5843

Topic: 2. Trauma

Which imaging modality is considered the 'gold standard' for diagnosing a stress fracture in its early stages when plain radiographs are often normal?

. Plain X-ray.
. Computed Tomography (CT).
. Bone scintigraphy (bone scan).
. Ultrasound.
. Magnetic Resonance Imaging (MRI).

Correct Answer & Explanation

. Magnetic Resonance Imaging (MRI).

Explanation

MRI is considered the 'gold standard' for early diagnosis of stress fractures. It can detect bone marrow edema, periosteal reaction, and early fracture lines before they are visible on plain radiographs or even CT scans. Bone scintigraphy is very sensitive but lacks specificity. Plain X-rays are often normal in early stress fractures. CT can show cortical changes but is less sensitive than MRI for early marrow changes. Ultrasound has limited utility for bone stress injuries.

Question 5844

Topic: 2. Trauma

A candidate is asked about common pitfalls in the management of open fractures. Which statement highlights a critical error in initial management?

. Delaying administration of broad-spectrum intravenous antibiotics.
. Performing wound irrigation with normal saline only.
. Using a topical antiseptic like povidone-iodine directly in the wound.
. Prioritizing skeletal stabilization over initial wound care.
. Scheduling definitive wound closure within 48 hours.

Correct Answer & Explanation

. Delaying administration of broad-spectrum intravenous antibiotics.

Explanation

Delaying the administration of broad-spectrum intravenous antibiotics is a critical error in the initial management of open fractures, as early antibiotic therapy significantly reduces the risk of infection. While copious irrigation and debridement are crucial, the antibiotics should be given as soon as possible after presentation. Topical antiseptics are generally avoided in open wounds. Skeletal stabilization and wound care should ideally occur concurrently or wound care slightly precede definitive fixation. Definitive wound closure within 48 hours (or sooner) is a management goal, not necessarily an error if delayed by patient factors.

Question 5845

Topic: 2. Trauma

The concept of 'tension band plating' is discussed. What is the primary biomechanical principle behind its effectiveness in fracture fixation?

. Neutralization of bending forces by rigid fixation.
. Converting tensile forces into compressive forces at the fracture site.
. Providing absolute stability through direct compression.
. Allowing controlled micromotion to stimulate callus formation.
. Shielding the bone from all stress to promote healing.

Correct Answer & Explanation

. Converting tensile forces into compressive forces at the fracture site.

Explanation

Tension band plating is based on the principle of converting tensile forces into compressive forces at the fracture site. By applying a plate to the tension side of a bone (e.g., anterior aspect of the femur with a transverse fracture), distraction forces during loading are resisted, creating compression across the fracture. This provides relative stability and promotes healing. It does not provide absolute stability in the same way as interfragmentary compression, nor does it typically allow controlled micromotion (unless designed for dynamic stabilization).

Question 5846

Topic: 2. Trauma

Which type of shock is most commonly encountered in a patient with a pelvic ring fracture and significant retroperitoneal hemorrhage?

. Cardiogenic shock.
. Obstructive shock.
. Distributive (septic) shock.
. Hypovolemic shock.
. Neurogenic shock.

Correct Answer & Explanation

. Hypovolemic shock.

Explanation

A pelvic ring fracture with significant retroperitoneal hemorrhage typically causes hypovolemic shock. The retroperitoneal space can accommodate a large volume of blood (several liters), leading to substantial blood loss and subsequent reduction in circulating blood volume. Cardiogenic shock is due to pump failure, obstructive shock from mechanical obstruction (e.g., tension pneumothorax), distributive shock from vasodilation (e.g., sepsis), and neurogenic shock from spinal cord injury (loss of sympathetic tone).

Question 5847

Topic: 2. Trauma

The concept of 'load sharing' is crucial in the biomechanics of fracture fixation. Which of the following fixation constructs best exemplifies the principle of load sharing?

. A lag screw providing interfragmentary compression.
. A fully articulated external fixator.
. A compression plate applied to a simple transverse fracture.
. An intramedullary nail for a diaphyseal fracture.
. A non-weight-bearing cast for a distal radius fracture.

Correct Answer & Explanation

. An intramedullary nail for a diaphyseal fracture.

Explanation

An intramedullary nail for a diaphyseal fracture is the best example of a load-sharing device. It shares the axial load with the bone, allowing controlled stress transfer that promotes callus formation and secondary bone healing. A lag screw provides interfragmentary compression (absolute stability). A compression plate also provides absolute stability. An external fixator, depending on its configuration, can be load-sharing but an intramedullary nail is the classic example in internal fixation. A cast is external and does not share load in the same biomechanical way as an IM nail.

Question 5848

Topic: Pelvic & Acetabular Trauma
During a Trauma viva, you are presented with a hemodynamically unstable patient with an Antero-Posterior Compression (APC) Type III pelvic injury. According to BOAST guidelines, what is the most appropriate initial mechanical intervention?
. Application of a pelvic binder over the iliac crests
. Application of a pelvic binder centered over the greater trochanters
. Immediate application of an anterior external fixator
. Emergency resuscitative endovascular balloon occlusion of the aorta (REBOA)
. Urgent internal fixation with symphyseal plating

Correct Answer & Explanation

. Application of a pelvic binder centered over the greater trochanters

Explanation

A pelvic binder provides rapid, non-invasive hemorrhage control by reducing pelvic volume. It must be centered over the greater trochanters to effectively close the pelvic ring, as placement over the iliac crests can worsen the deformity.

Question 5849

Topic: 2. Trauma

During a discussion on fracture fixation principles (Perren's Strain Theory), the examiner asks what level of interfragmentary strain is required to promote primary (direct) bone healing without callus formation. What is the correct threshold?

. Between 2% and 10%
. Between 10% and 30%
. Greater than 10%
. Less than 2%
. Exactly 0% exclusively

Correct Answer & Explanation

. Less than 2%

Explanation

Primary bone healing occurs via cutting cones and requires absolute stability. According to Perren's strain theory, this requires an interfragmentary strain of less than 2%, typically achieved with compression plating or lag screws.

Question 5850

Topic: 2. Trauma

A 35-year-old obtunded patient with a tibial shaft fracture is suspected of having acute compartment syndrome. Intracompartment syndrome. What is the universally accepted threshold for diagnosing compartment syndrome using intracompartmental pressure monitoring?

. An absolute intracompartmental pressure greater than 15 mmHg
. A diastolic blood pressure minus intracompartmental pressure (delta P) of less than 45 mmHg
. A diastolic blood pressure minus intracompartmental pressure (delta P) of less than 30 mmHg
. A mean arterial pressure minus intracompartmental pressure of less than 20 mmHg
. An absolute intracompartmental pressure greater than 20 mmHg

Correct Answer & Explanation

. A diastolic blood pressure minus intracompartmental pressure (delta P) of less than 30 mmHg

Explanation

Diagnosis in an obtunded patient relies on continuous or repeated intracompartmental pressure measurements. A delta pressure (Diastolic BP - Compartment Pressure) of less than 30 mmHg is highly indicative of acute compartment syndrome.

Question 5851

Topic: 2. Trauma
A patient presents with an open tibial fracture. According to the Gustilo-Anderson classification, the wound is 12 cm long, with extensive periosteal stripping and requires a rotational muscle flap for coverage. Which classification grade is this?
. Type II
. Type IIIA
. Type IIIB
. Type IIIC
. Type IV

Correct Answer & Explanation

. Type IIIB

Explanation

Gustilo-Anderson Type IIIB fractures involve extensive soft tissue injury with periosteal stripping and exposed bone requiring flap coverage (local or free). Type IIIA allows for primary closure without a flap, and Type IIIC indicates an arterial injury requiring repair.

Question 5852

Topic: 2. Trauma
According to the British Orthopaedic Association Standards for Trauma (BOAST) guidelines for open fractures, when should definitive soft tissue coverage ideally be achieved for a Gustilo-Anderson Grade IIIB tibial diaphyseal fracture?
. Within 24 hours of injury
. Within 48 hours of injury
. Within 72 hours of injury
. Within 7 days of injury
. Within 14 days of injury

Correct Answer & Explanation

. Within 72 hours of injury

Explanation

BOAST guidelines recommend that definitive skeletal fixation and soft tissue coverage for open tibial fractures should ideally be performed within 72 hours. Delayed coverage beyond this timeframe significantly increases the risk of deep infection.

Question 5853

Topic: 2. Trauma

An examiner in the Basic Science viva asks about the biomechanical principles of fracture fixation. Which of the following statements best describes the mechanical advantage of a locking compression plate (LCP) over a conventional dynamic compression plate (DCP)?

. It requires precise anatomical contouring to maintain fracture reduction.
. It relies on friction between the plate and the bone to provide stability.
. It acts as a fixed-angle construct that does not require compression against the bone.
. It provides absolute stability primarily through dynamic axial compression.
. It has a lower pull-out strength in osteoporotic bone compared to a DCP.

Correct Answer & Explanation

. It acts as a fixed-angle construct that does not require compression against the bone.

Explanation

Locking plates function as fixed-angle single-beam constructs because the screw heads thread directly into the plate. This eliminates the need for plate-to-bone friction, preserving periosteal blood supply and providing superior hold in osteoporotic bone.

Question 5854

Topic: 2. Trauma

A 30-year-old motorcyclist is brought into the resus room with a hemodynamically unstable pelvic ring injury. A pelvic binder is applied. To achieve optimal mechanical closure of the pelvic volume, where should the binder be centered?

. Level of the iliac crests
. Level of the anterior superior iliac spines (ASIS)
. Level of the greater trochanters
. Level of the mid-femoral diaphysis
. Level of the umbilicus

Correct Answer & Explanation

. Level of the greater trochanters

Explanation

A pelvic binder must be applied centered precisely over the greater trochanters to effectively reduce pelvic volume and stabilize the fracture. Application over the iliac crests is ineffective and can inadvertently open the pelvic ring further in some fracture patterns.

Question 5855

Topic: 2. Trauma

A 28-year-old male suffers a comminuted tibial diaphyseal fracture. Six hours post-intramedullary nailing, he complains of severe pain resistant to opioids. On examination, there is pain with passive stretch of the hallux. Which delta pressure (diastolic blood pressure minus intracompartmental pressure) is considered the threshold for diagnosing acute compartment syndrome?

. Less than 10 mmHg
. Less than 20 mmHg
. Less than 30 mmHg
. Less than 45 mmHg
. Less than 60 mmHg

Correct Answer & Explanation

. Less than 30 mmHg

Explanation

A delta pressure (diastolic BP minus intracompartmental pressure) of less than 30 mmHg is the widely accepted clinical threshold for diagnosing acute compartment syndrome. Absolute pressure readings are less reliable due to natural variations in systemic blood pressure.

Question 5856

Topic: 2. Trauma

During a trauma viva, you are presented with a 25-year-old intubated and ventilated polytrauma patient who has an isolated closed tibial shaft fracture. The leg is tense, pale, and pulseless. You diagnose acute compartment syndrome. Regarding consent and immediate management, what is the most appropriate next step under UK law (Mental Capacity Act) and FRCS principles?

. Delay surgery until a next-of-kin arrives to sign the consent form.
. Obtain an emergency court order before proceeding with a four-compartment fasciotomy.
. Wait for the patient to be extubated to assess capacity and obtain informed consent.
. Proceed immediately with a four-compartment fasciotomy under the principle of best interests to save life or limb.
. Perform a prophylactic two-incision fasciotomy without formal documentation since it is a life-saving emergency.

Correct Answer & Explanation

. Proceed immediately with a four-compartment fasciotomy under the principle of best interests to save life or limb.

Explanation

Under the Mental Capacity Act, if an adult lacks capacity and faces an immediate threat to life or limb, emergency treatment must proceed in their best interests without delay. Next-of-kin cannot legally consent on behalf of an adult in the UK, though they should be consulted if time permits.

Question 5857

Topic: Lower Extremity Trauma

A surgeon is performing a posteromedial approach to the tibia to fix a Schatzker IV tibial plateau fracture involving a posteromedial shear fragment. Between which two anatomical structures is the primary surgical interval developed?

. Tibialis posterior and Flexor digitorum longus
. Medial head of the gastrocnemius and the pes anserinus
. Popliteus and Soleus
. Semimembranosus and Semitendinosus
. Medial collateral ligament and medial meniscus

Correct Answer & Explanation

. 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 (which is retracted posteriorly) and the pes anserinus (which is retracted anteriorly). This provides excellent exposure to the posteromedial corner of the tibial plateau, allowing for buttress plating of posteromedial shear fragments often seen in Schatzker IV and bicondylar tibial plateau fractures.

Question 5858

Topic: Pelvic & Acetabular Trauma
A 40-year-old male arrives at the trauma bay with hemodynamic instability following a crush injury to the pelvis. AP pelvis radiograph demonstrates an APC-III pelvic ring injury. An emergent pelvic binder is to be applied. At what anatomic level should the binder be centered for optimal reduction of the pelvic volume?
. Over the iliac crests
. Midway between the iliac crests and the pubic symphysis
. Centered over the greater trochanters
. Directly over the lower lumbar spine and sacrum
. Centered over the proximal femoral shafts

Correct Answer & Explanation

. Centered over the greater trochanters

Explanation

Pelvic binders must be centered over the greater trochanters to effectively close the pelvic ring and reduce pelvic volume. Placement over the iliac crests is a common error and is less effective at closing the symphysis pubis; it can even paradoxically worsen inferior ring displacement.

Question 5859

Topic: 2. Trauma

A 28-year-old male sustains a closed spiral fracture of the distal third of the humeral shaft (Holstein-Lewis fracture). On initial examination, he is noted to have a complete radial nerve palsy. He is managed non-operatively in a functional brace. At what time point should an EMG and nerve conduction study be ordered if there is no clinical evidence of radial nerve recovery?

. 2 weeks post-injury
. 6 weeks post-injury
. 12 weeks post-injury
. 6 months post-injury
. 1 year post-injury

Correct Answer & Explanation

. 12 weeks post-injury

Explanation

Radial nerve palsy associated with closed humeral shaft fractures (including Holstein-Lewis types) is usually a neuropraxia or axonotmesis that recovers spontaneously. Initial management is observation. If there is no clinical evidence of nerve recovery (e.g., return of brachioradialis or extensor carpi radialis longus function) at 3 to 4 months (12-16 weeks) post-injury, EMG and nerve conduction studies are indicated to evaluate for reinnervation or the need for surgical exploration.

Question 5860

Topic: 2. Trauma

Nonunion is a recognized complication of scaphoid waist fractures, largely due to its tenuous blood supply. The primary blood supply to the proximal pole of the scaphoid enters the bone at which anatomical location and is derived from which artery?

. Enters the proximal pole directly from the ulnar artery
. Enters the distal pole and waist primarily from the dorsal carpal branch of the radial artery and flows in a retrograde fashion
. Enters the proximal pole directly from the superficial palmar arch
. Enters the volar aspect of the waist from the anterior interosseous artery and flows in an antegrade fashion
. Enters the distal pole from the deep palmar arch and flows in an antegrade fashion

Correct Answer & Explanation

. Enters the distal pole and waist primarily from the dorsal carpal branch of the radial artery and flows in a retrograde fashion

Explanation

Approximately 70-80% of the scaphoid's blood supply comes from the dorsal carpal branch of the radial artery, which enters the bone distally at the dorsal ridge (distal to the waist) and flows in a retrograde fashion to supply the proximal pole. This retrograde blood supply explains the high incidence of avascular necrosis and nonunion in fractures of the scaphoid waist and proximal pole.

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