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 2221
Topic: 2. Trauma
A 50-year-old female presents with a closed, isolated extra-articular scapular body fracture after a high-speed motor vehicle crash. Which of the following parameters represents a generally accepted indication for operative fixation?
Correct Answer & Explanation
. Angular deformity of 45 degrees
Explanation
Operative indications for extra-articular scapular fractures include severe angular deformity (typically >= 45 degrees), marked medial/lateral displacement (> 20 mm), or a glenopolar angle of <= 22 degrees.
Question 2222
Topic: Upper Extremity Trauma
When evaluating a standard anteroposterior chest radiograph for a suspected scapulothoracic dissociation, which finding is most diagnostic of this condition?
Correct Answer & Explanation
. Significantly increased distance from the spinous processes to the medial border of the scapula
Explanation
Scapulothoracic dissociation is defined by massive lateral displacement of the scapula. Radiographically, this is measured as a significantly increased distance from the thoracic spinous processes to the medial border of the scapula compared to the contralateral side.
Question 2223
Topic: 2. Trauma
During the closed reduction of a posterior sternoclavicular joint dislocation in the operating room, which of the following logistical precautions is most critical?
Correct Answer & Explanation
. Having a cardiothoracic surgeon available on standby
Explanation
Posterior SC dislocations place critical mediastinal structures at risk, and the medial clavicle may tamponade a lacerated vessel. A cardiothoracic surgeon must be immediately available during reduction in case catastrophic hemorrhage occurs upon disimpacting the clavicle.
Question 2224
Topic: 2. Trauma
Which of the following clinical findings represents the earliest and most reliable sign of compartment syndrome in an alert patient sustaining a tibial plateau fracture?
Correct Answer & Explanation
. Pain out of proportion to the injury and exacerbated by passive stretch
Explanation
Pain out of proportion to the injury, specifically pain elicited by passive stretch of the muscles in the involved compartment, is the most sensitive and earliest clinical sign of compartment syndrome. Pulselessness and paralysis are late, ominous signs.
Question 2225
Topic: 2. Trauma
When determining the need for fasciotomies in a patient with a closed tibial shaft fracture and suspected compartment syndrome, which pressure threshold is generally accepted as an absolute indication for surgery?
The delta pressure is the most reliable indicator for fasciotomy to avoid unnecessary surgery in normotensive patients. A delta pressure (diastolic blood pressure minus compartment pressure) of less than or equal to 30 mmHg is the accepted threshold for performing a fasciotomy.
Question 2226
Topic: Pelvic & Acetabular Trauma
A 35-year-old trauma patient with an unstable pelvic ring injury requires the application of a pelvic binder to reduce pelvic volume and control hemorrhage. For maximum biomechanical effectiveness, over which anatomical landmark should the binder be centered?
Correct Answer & Explanation
. Greater trochanters
Explanation
To effectively reduce pelvic volume and compress the bleeding surfaces of a disrupted pelvic ring, the pelvic binder must be centered over the greater trochanters. Placement over the iliac crests is incorrect and can paradoxically open the pelvic ring.
Question 2227
Topic: 2. Trauma
A 28-year-old male sustains a midshaft clavicle fracture. Which of the following radiographic findings is most strongly associated with a higher risk of nonunion if treated non-operatively?
Correct Answer & Explanation
. Displacement greater than 100% of the bone width
Explanation
Significant displacement (greater than 100% of the bone width), shortening greater than 2 cm, and severe comminution are the primary risk factors for nonunion in midshaft clavicle fractures treated non-operatively.
Question 2228
Topic: 2. Trauma
Which of the following describes the pathophysiology of a Neer Type II distal clavicle fracture, leading to its high nonunion rate?
Correct Answer & Explanation
. The fracture occurs medial to the coracoclavicular ligaments, which remain attached to the distal fragment.
Explanation
In a Neer Type II distal clavicle fracture, the fracture is medial to the intact coracoclavicular ligaments (which hold the distal fragment down), while the trapezius pulls the proximal fragment superiorly. This significant deforming force leads to a high rate of nonunion if treated conservatively.
Question 2229
Topic: 2. Trauma
A 25-year-old male sustains a gunshot wound to the thigh. Radiographs confirm a comminuted distal femur fracture with the bullet lodged entirely within the knee joint capsule. What is the most appropriate management regarding the retained bullet?
Correct Answer & Explanation
. Perform an arthrotomy or arthroscopy to remove the bullet, followed by fracture management
Explanation
Bullets retained within a synovial joint space must be removed surgically (via arthrotomy or arthroscopy). Synovial fluid breaks down the bullet, leading to severe joint destruction (lead arthropathy) and systemic lead toxicity (plumbism).
Question 2230
Topic: 2. Trauma
A 40-year-old male with multiple long bone fractures becomes acutely confused, hypoxic, and develops a petechial rash over his axilla and chest 48 hours after admission. What is the most likely diagnosis?
Correct Answer & Explanation
. Fat embolism syndrome
Explanation
Fat Embolism Syndrome typically presents 24-72 hours after major trauma involving long bone fractures. The classic triad includes hypoxemia, neurological abnormalities (confusion/agitation), and a petechial rash over the upper body.
Question 2231
Topic: 2. Trauma
Which of the following injuries is classified as a Gustilo-Anderson Type IIIA open fracture?
Correct Answer & Explanation
. A high-energy fracture with an 11 cm laceration, but adequate soft tissue coverage of the bone
Explanation
Gustilo-Anderson Type IIIA describes a high-energy open fracture with extensive soft tissue damage, but with adequate soft tissue coverage of the fractured bone despite the size of the laceration. Type IIIB requires a flap, and Type IIIC involves an arterial injury requiring repair.
Question 2232
Topic: 2. Trauma
In the setting of a severe 'mangled' lower extremity, which of the following is generally considered an absolute indication for primary amputation?
Correct Answer & Explanation
. Warm ischemia time exceeding 6 hours with irreversible muscle necrosis
Explanation
Prolonged warm ischemia (typically >6 hours) resulting in irreversible muscle necrosis is an absolute indication for amputation. Loss of plantar sensation on initial presentation is no longer considered an absolute indication, as sensation may recover after resuscitation and stabilization.
Question 2233
Topic: 2. Trauma
A patient with flail chest and multiple displaced rib fractures is being evaluated by the orthopedic trauma service. According to current literature, what is the most widely accepted primary indication for surgical rib fixation (plating)?
Correct Answer & Explanation
. Failure to wean from mechanical ventilation
Explanation
Surgical stabilization of severe rib fractures (rib plating) is primarily indicated for patients with flail chest who are failing to wean from mechanical ventilation. Plating restores chest wall mechanics, reducing ventilator days and pulmonary complications.
Question 2234
Topic: 2. Trauma
A 62-year-old female undergoes open reduction and internal fixation of a distal femur fracture. During the procedure, the orthopedic surgeon notes that the bone quality is osteoporotic. To maximize the pull-out strength of the cortical screws in this challenging bone, which of the following screw modifications or techniques would provide the MOST significant biomechanical advantage?
Correct Answer & Explanation
. C. Utilizing screws with a finer pitch and a larger outer diameter.
Explanation
Correct Answer: CExplanation:The pull-out strength of a screw is directly related to the contact surface area between the screw threads and the bone. In osteoporotic bone, maximizing this contact is crucial. Option C, utilizing screws with a finer pitch and a larger outer diameter, directly addresses this principle. Afiner pitchmeans there are more threads per unit length, thus increasing the number of threads engaged in a given depth of cortex, which significantly enhances resistance to pull-out. Alarger outer diameteralso increases the surface area of the threads in contact with the bone, further contributing to pull-out strength.Why other options are incorrect:A. Using screws with a larger core diameter:A larger core diameter, while potentially increasing the screw's bending strength, would decrease the thread depth and thus reduce the contact area between the threads and the bone, thereby reducing pull-out strength. To maximize pull-out strength, a smaller core diameter (relative to outer diameter) is generally preferred to allow for deeper threads.B. Increasing the pitch of the screw threads:Increasing the pitch (making it 'coarser') means there are fewer threads per unit length. This would decrease the number of threads engaged in the bone cortex for a given depth, thereby reducing the contact surface area and consequently the pull-out strength.D. Decreasing the number of threads engaged in the bone cortex:This directly contradicts the principle of maximizing pull-out strength. More threads engaged in the bone cortex lead to a greater contact surface area and higher pull-out resistance.E. Employing screws with a smooth, unthreaded shank that extends deep into the bone:While a smooth shank is part of some screw designs (e.g., lag screws where the unthreaded portion crosses the fracture line), extending it deep into the bone without threads would not contribute to pull-out strength in that region. Pull-out strength is primarily derived from the engagement of the threaded portion with the bone.
Question 2235
Topic: 2. Trauma
A 35-year-old male sustains a tibial plateau fracture requiring surgical fixation. During the procedure, the surgeon inadvertently makes the pilot hole for a cortical screw slightly larger than recommended. What is the most likely immediate biomechanical consequence of this technical error on the screw's performance?
Correct Answer & Explanation
. C. Significant reduction in the screw's pull-out strength.
Explanation
Correct Answer: CExplanation:Making too large a pilot hole is a well-known surgeon factor that significantly reduces screw pull-out strength. The pilot hole creates the space for the screw's core, and the threads then cut into the surrounding bone. If the pilot hole is too large, the screw threads will have less bone to engage with, leading to a reduced contact surface area between the threads and the bone. This diminished engagement directly translates to a lower axial force required to remove the screw, hence a significant reduction in pull-out strength.Why other options are incorrect:A. Increased torsional strength of the screw within the bone:Torsional strength refers to the screw's resistance to twisting. While the screw itself has inherent torsional strength, an oversized pilot hole weakens the bone-screw interface, making it more prone to stripping or loosening under torsional loads, not increasing its strength.B. Enhanced primary stability due to reduced stress shielding:Stress shielding occurs when the implant carries too much load, preventing the bone from being adequately stressed, which can lead to bone resorption. An oversized pilot hole leads to poor fixation and reduced primary stability, making stress shielding less relevant in this immediate context, and certainly not 'enhanced' stability.D. Improved bone-screw interface for osseointegration:Osseointegration is a long-term biological process. An oversized pilot hole creates a poor mechanical interface initially, which is detrimental to both primary stability and the conditions necessary for optimal osseointegration.E. Decreased risk of screw stripping during insertion:Screw stripping occurs when the threads in the bone are damaged, often due to excessive torque or a pilot hole that is too small (leading to high resistance). An oversized pilot hole might make it easier to insert the screw, but it increases the risk of the screw not achieving adequate purchase, or even stripping the already weakened bone interface, rather than decreasing the risk of stripping.
Question 2236
Topic: 2. Trauma
A 48-year-old male presents with a comminuted olecranon fracture. During surgical repair, the surgeon initially inserts a screw, but due to malalignment, removes it and reinserts it into the same pilot hole. What is the most likely biomechanical consequence of this repeated withdrawal and reintroduction on the screw's fixation?
Correct Answer & Explanation
. C. Damage to the negative threads in the bone tissue, reducing pull-out strength.
Explanation
Correct Answer: CExplanation:Repeated withdrawal and reintroduction of a screw into the same pilot hole is a critical surgeon factor that reduces pull-out strength. Each time the screw is removed and reinserted, it damages the 'negative threads' (the thread pattern created in the bone tissue) within the pilot hole. This damage reduces the effective contact surface area between the screw threads and the bone, leading to a significant decrease in the axial force required to remove the screw, thus compromising its pull-out strength and overall fixation stability.Why other options are incorrect:A. Increased bone density around the screw threads:Repeated insertion and removal would disrupt, not increase, bone density around the threads. It would lead to microfractures and widening of the bone-screw interface.B. Enhanced primary stability due to bone compaction:While initial screw insertion can cause some local bone compaction, repeated removal and reinsertion primarily cause damage and widening of the hole, which diminishes, rather than enhances, primary stability.D. Improved screw-bone interface for better load transfer:A damaged bone-screw interface from repeated insertion would lead to a poorer, not improved, interface, compromising load transfer and increasing the risk of loosening.E. No significant impact on pull-out strength if reinsertion is careful:This is incorrect. Even with careful reinsertion, some degree of damage to the bone threads is inevitable, especially in softer cancellous bone or osteoporotic cortical bone. The cumulative damage from repeated cycles will invariably reduce pull-out strength.
Question 2237
Topic: 2. Trauma
A 70-year-old patient with severe osteoporosis undergoes internal fixation of a proximal humerus fracture using a locking plate system. The surgeon aims to maximize the stability of the locking screws. Which biomechanical principle is primarily leveraged by the use of locking screws to enhance fixation in this scenario?
Correct Answer & Explanation
. B. Creation of a monobloc effect between the screw, plate, and bone.
Explanation
Correct Answer: BExplanation:The primary biomechanical advantage of locking screws, especially in osteoporotic bone, is the creation of amonobloc effect. Locking screws thread into the plate, forming a fixed-angle construct. This effectively transforms the screw-plate interface into a single, rigid unit. This rigid construct then acts as an internal fixator, providing angular stability and distributing forces over a larger area, rather than relying solely on screw purchase in potentially poor-quality bone. This 'monobloc' or 'fixed-angle' effect is crucial for stability in osteoporotic bone where traditional non-locking screws might easily pull out.Why other options are incorrect:A. Increased friction at the screw-plate interface:While there is friction, the primary mechanism of locking screws is not friction but rather the threaded engagement with the plate, creating a rigid connection. Non-locking screws rely on friction and compression at the screw-plate interface.C. Greater compression of the bone fragments by the screw head:Locking screws are designed to provide angular stability, not interfragmentary compression. They do not pull the bone fragments to the plate in the same way traditional non-locking screws do. In fact, overtightening a locking screw can strip the threads in the plate.D. Enhanced screw purchase through dynamic compression:Dynamic compression is a feature of certain plate designs (e.g., DCP, LC-DCP) where eccentric drilling allows the screw to pull the bone fragments together. Locking screws primarily provide angular stability and do not inherently provide dynamic compression.E. Reduction of stress shielding at the fracture site:While locking plates can sometimes lead to stress shielding due to their rigidity, their primary mechanism for enhancing fixation (especially in poor bone) is not to reduce stress shielding, but to provide stable fixation. The rigidity of the construct can sometimes be a disadvantage regarding stress shielding.
Question 2238
Topic: 2. Trauma
A 55-year-old male undergoes fixation of a distal radius fracture. The surgeon is using a standard cortical screw. Referring to the provided image of screw anatomy, which labeled component is primarily responsible for preventing the screw from sinking too deeply into the bone and provides the connection point for the screwdriver?
Correct Answer & Explanation
. C. Head
Explanation
Correct Answer: CExplanation:As described in the teaching case, theheadof the screw serves two primary functions: it provides the connection point for a screwdriver, allowing for insertion and removal, and it prevents the screw from sinking too deeply into the bone once it reaches its desired depth or engages the plate. The image clearly labels the 'Head' as the uppermost part of the screw, consistent with these functions.Why other options are incorrect:A. Shank:The shank is the smooth, unthreaded portion of the screw between the head and the threaded part. Its primary function is to provide a smooth link and, in some cases (like lag screws), to allow for compression across a fracture without engaging the near cortex. It does not prevent sinking or provide a screwdriver connection.B. Thread:The threads are the helical ridges that engage with the bone, providing purchase and pull-out strength. They are crucial for fixation but do not prevent sinking of the entire screw or serve as the screwdriver interface.D. Flute:Flutes are cutting features at the tip of some screws (self-tapping screws) that help remove bone debris during insertion. They are not involved in preventing sinking or screwdriver connection.E. Pitch:Pitch refers to the distance between adjacent screw threads. It is a characteristic of the thread geometry that influences pull-out strength but is not a physical component that prevents sinking or connects to the screwdriver.
Question 2239
Topic: 2. Trauma
During the insertion of a cortical screw for a fibular fracture, the surgeon experiences significant wobbling of the screwdriver handle. What is the most likely long-term consequence of this technical error on the screw's stability?
Correct Answer & Explanation
. C. Reduced pull-out strength due to damage to the bone threads.
Explanation
Correct Answer: CExplanation:Wobbling of the screwdriver handle during insertion is a surgeon factor that can significantly reduce screw pull-out strength. This wobbling causes the screw to oscillate within the pilot hole, leading to irregular and damaged bone threads (the 'negative threads') as the screw advances. This damage reduces the effective contact surface area between the screw threads and the bone, thereby decreasing the axial force required to remove the screw and compromising its long-term stability and pull-out strength.Why other options are incorrect:A. Increased bone formation around the screw due to micromotion:While controlled micromotion can sometimes stimulate bone healing, excessive and uncontrolled motion (like that caused by wobbling) typically leads to fibrous tissue formation or bone resorption, not increased bone formation, and certainly not enhanced stability.B. Enhanced primary stability through improved bone-screw contact:Wobbling damages the bone-screw interface, creating an irregular and less intimate contact, which diminishes, rather than enhances, primary stability.D. Accelerated osseointegration of the screw into the bone:Osseointegration requires a stable, undisturbed interface. Wobbling creates an unstable environment that is detrimental to osseointegration, potentially leading to fibrous encapsulation instead.E. No significant impact on stability if the screw is fully seated:This is incorrect. Even if the screw appears fully seated, the damage to the bone threads caused by wobbling means that the screw's purchase and pull-out strength are compromised from the outset, leading to reduced long-term stability.
Question 2240
Topic: 2. Trauma
A 28-year-old male sustains a spiral fracture of the tibia. The surgeon plans to use cortical screws for fixation. To optimize the screw's resistance to axial forces (pull-out strength), which of the following design characteristics would be most beneficial?
Correct Answer & Explanation
. C. Increased thread depth.
Explanation
Correct Answer: CExplanation:The pull-out strength of a screw is directly proportional to the contact surface area between the screw threads and the bone.Increased thread depthmeans that the threads penetrate deeper into the bone, maximizing the volume of bone engaged by the threads. This significantly increases the contact surface area, thereby enhancing the screw's resistance to axial pull-out forces.Why other options are incorrect:A. A larger core diameter relative to the outer diameter:A larger core diameter means the threads are shallower (less thread depth) for a given outer diameter. This reduces the contact surface area between the threads and the bone, thereby decreasing pull-out strength.B. A coarser thread pitch:A coarser pitch means fewer threads per unit length. This reduces the number of threads engaged in the bone cortex for a given depth, leading to a smaller contact surface area and reduced pull-out strength. A finer pitch is preferred for maximizing pull-out strength.D. A shorter threaded segment:A shorter threaded segment means fewer threads are engaged in the bone. To maximize pull-out strength, it is desirable to have as many threads as possible engaged in the bone cortex, implying a longer threaded segment where appropriate.E. A smooth, polished screw surface:A smooth surface would reduce friction and engagement with the bone, severely compromising pull-out strength. The rough, irregular surface of the threads is essential for mechanical interlock with the bone.
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