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2. Trauma MCQs

Practice Set 459 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 9161

Topic: 2. Trauma

Which radiographic sign is most indicative of a nonunion, as opposed to a delayed union?

. Persistent fracture line visible at 4 months
. Increasing callus formation with persistent pain at 5 months
. Sclerosis and smooth, corticated bone ends at the fracture gap at 8 months
. Decreased pain and progressive weight-bearing tolerance at 7 months
. Early bridging callus visible at 3 months

Correct Answer & Explanation

. Sclerosis and smooth, corticated bone ends at the fracture gap at 8 months

Explanation

Sclerosis and smooth, corticated bone ends at the fracture gap (often described as 'elephant foot' or 'horse hoof' for hypertrophic nonunion, or 'pencil-point' for atrophic nonunion) are classic radiographic signs of a nonunion, indicating a biological cessation of healing. A persistent fracture line or increasing callus with pain can be seen in delayed union. Progressive weight-bearing tolerance and bridging callus indicate healing.

Question 9162

Topic: 2. Trauma

What characterizes a hypertrophic nonunion?

. Absent callus formation with necrotic bone ends
. Excessive but non-bridging callus formation, often due to instability
. Gap defect with no biological activity
. Consolidated bone in an anatomically incorrect position
. Avascular bone fragments with no signs of attempted healing

Correct Answer & Explanation

. Excessive but non-bridging callus formation, often due to instability

Explanation

A hypertrophic nonunion is characterized by abundant callus formation that fails to bridge the fracture gap, typically due to excessive interfragmentary motion (instability). It is biologically active but mechanically unstable. Atrophic nonunion involves absent callus and biologically inert bone ends. Malunion is healed but malaligned. Avascular bone fragments are more descriptive of atrophic nonunion or avascular necrosis.

Question 9163

Topic: 2. Trauma

Malunion is defined as:

. A fracture that has not healed within 6 months
. A fracture that has healed in an anatomically unacceptable position
. A fracture with excessive fibrous tissue at the fracture site
. A fracture with complete lack of callus formation
. A fracture that requires surgical intervention for union

Correct Answer & Explanation

. A fracture that has healed in an anatomically unacceptable position

Explanation

Malunion refers to a fracture that has healed, but in an anatomically unacceptable position, leading to functional impairment, pain, or cosmetic deformity. Delayed union and nonunion describe failures of the healing process itself. Fibrous tissue or lack of callus are signs of nonunion. Not all fractures requiring surgery are malunions.

Question 9164

Topic: 2. Trauma
What is the primary treatment principle for a hypertrophic nonunion?
. Extensive débridement and bone grafting
. Bone stimulator with continued immobilization
. Increasing mechanical stability to reduce interfragmentary motion
. Pharmacological agents to stimulate callus formation
. Vascularized bone flap transfer

Correct Answer & Explanation

. Increasing mechanical stability to reduce interfragmentary motion

Explanation

Hypertrophic nonunions are biologically active but mechanically unstable. Therefore, the primary treatment is to increase mechanical stability, often by more rigid internal fixation (e.g., re-nailing, plate exchange, adding compression). Bone grafting is generally not required as there is already biological activity. Vascularized bone flaps are typically for large defects or atrophic nonunions.

Question 9165

Topic: 2. Trauma

Which physical modality uses low-intensity pulsed ultrasound (LIPUS) to promote fracture healing, particularly in delayed unions or nonunions?

. Pulsed electromagnetic fields (PEMFs)
. Capacitively coupled electric fields (CCEFs)
. Direct current stimulation (DCS)
. High-frequency vibration therapy
. Extracorporeal shockwave therapy (ESWT)

Correct Answer & Explanation

. Pulsed electromagnetic fields (PEMFs)

Explanation

Low-intensity pulsed ultrasound (LIPUS) is a non-invasive physical therapy known to accelerate fracture healing and promote union in delayed and nonunions. It is believed to stimulate cellular activity, enhance angiogenesis, and promote growth factor production. PEMFs and CCEFs are also forms of electrical bone stimulation, but LIPUS uses ultrasound. ESWT uses high-energy sound waves and is used for specific conditions like chronic tendinopathies or some nonunions.

Question 9166

Topic: 2. Trauma

When are bone graft substitutes (e.g., ceramics, polymers) most appropriate for use in fracture healing?

. In situations requiring immediate structural support and robust osteoinductivity
. When a large vascularized bone defect needs to be bridged
. As a primary alternative to autograft for all nonunions
. When osteoconductive properties are primarily needed, and the defect is not critical-sized
. To provide osteogenic cells in an atrophic nonunion

Correct Answer & Explanation

. When osteoconductive properties are primarily needed, and the defect is not critical-sized

Explanation

Bone graft substitutes are primarily osteoconductive (providing a scaffold for new bone growth) and are best suited for smaller defects where osteoinductive and osteogenic properties are not the primary requirement, or as extenders for autograft. They typically lack osteogenic cells and often strong osteoinductive capacity. Autograft remains the gold standard for critical-sized defects and atrophic nonunions requiring robust biological stimulation. Vascularized flaps are for large defects with poor local biology.

Question 9167

Topic: 2. Trauma

Reaming during intramedullary nailing of long bone fractures has several effects on fracture healing. Which of the following is considered a beneficial biological effect of reaming?

. It causes significant damage to the periosteal blood supply, enhancing callus formation.
. It allows for the insertion of a larger, stiffer nail, promoting primary healing.
. The reamings provide a bone graft material rich in osteogenic and osteoinductive factors.
. It significantly reduces the risk of fat embolism.
. It sterilizes the medullary canal.

Correct Answer & Explanation

. The reamings provide a bone graft material rich in osteogenic and osteoinductive factors.

Explanation

Reaming generates reamings (bone debris) that are rich in osteogenic cells, growth factors, and marrow elements. These reamings are forced into the fracture gap and surrounding soft tissues, providing a biological augmentation that promotes fracture healing. While reaming can compromise endosteal blood supply, the biological benefit of the reamings is significant. It does not primarily promote primary healing (IMN is usually secondary healing), nor does it reduce fat embolism or sterilize the canal.

Question 9168

Topic: 2. Trauma

In pathological fractures (e.g., due to metastatic bone disease), what is the primary goal of fixation and how does healing differ from traumatic fractures?

. Achieve biological union as the sole outcome, similar to traumatic fractures.
. Provide pain relief and mechanical stability, often without expecting complete biological union.
. Promote rapid callus formation through aggressive bone grafting.
. Utilize external fixation only to avoid further soft tissue damage.
. Administer high-dose corticosteroids to reduce inflammation and promote healing.

Correct Answer & Explanation

. Provide pain relief and mechanical stability, often without expecting complete biological union.

Explanation

In pathological fractures, especially those due to metastatic disease, the primary goal of fixation is often pain relief and mechanical stability to allow weight-bearing and improve quality of life. Complete biological union is often not expected or achieved, given the underlying disease process that impairs normal bone healing mechanisms. While some healing can occur, it's typically not the sole or primary outcome. Aggressive bone grafting may not be indicated, and corticosteroids can hinder healing.

Question 9169

Topic: 2. Trauma

According to Perren's Strain Theory, what biomechanical environment is most conducive to secondary (endochondral) fracture healing?

. Absolute rigidity (0% strain)
. High strain (>10%) leading to fibrous tissue
. Moderate, controlled interfragmentary motion (2-10% strain)
. Continuous compression without any shear stress
. Distraction without any interfragmentary contact

Correct Answer & Explanation

. Moderate, controlled interfragmentary motion (2-10% strain)

Explanation

Perren's Strain Theory describes how different tissues form based on local strain. Moderate, controlled interfragmentary motion (typically 2-10% strain) is optimal for secondary (endochondral) fracture healing, promoting chondrogenesis and subsequent bone formation. Absolute rigidity leads to primary healing, high strain to fibrous tissue, and excessive distraction or continuous compression without specific conditions is not optimal for secondary healing.

Question 9170

Topic: 2. Trauma

Dynamization of an intramedullary nail (e.g., removing a locking screw) is sometimes performed in delayed unions. What is the intended biomechanical effect of dynamization to promote healing?

. To increase rotational stability
. To convert primary healing to secondary healing by allowing axial micromotion
. To decrease interfragmentary compression
. To entirely eliminate all strain at the fracture site
. To increase the risk of nail bending failure

Correct Answer & Explanation

. To convert primary healing to secondary healing by allowing axial micromotion

Explanation

Dynamization is performed to convert a mechanically stable but biologically quiescent fracture (often one that was too rigidly fixed) into an environment that permits axial micromotion (controlled strain). This micromotion stimulates chondrogenesis and osteogenesis, thereby converting the healing process from a stalled primary healing attempt to a more robust secondary healing process. It reduces rigidity, allowing beneficial axial load and strain, which can break the fibrous nonunion.

Question 9171

Topic: 2. Trauma

In the context of bone healing, what does the term 'non-critical size defect' refer to?

. A bone defect that requires immediate bone grafting to heal.
. A defect that is too large to heal spontaneously without intervention.
. A defect that can spontaneously bridge and heal by itself.
. A defect that has resulted in a nonunion requiring revision surgery.
. A defect typically seen in pathological fractures.

Correct Answer & Explanation

. A defect that can spontaneously bridge and heal by itself.

Explanation

A non-critical size defect in bone is one that is small enough to heal spontaneously by native bone regeneration mechanisms without the need for additional biological intervention like bone grafting. Conversely, a 'critical size defect' is a defect that is too large to heal on its own and will typically lead to a nonunion if not treated with bone graft or other augmentation.

Question 9172

Topic: 2. Trauma
Which technique for managing nonunion involves deliberately cutting the nonunion site to create a new fracture, followed by re-fixation and potentially bone grafting, aiming to restart the healing cascade?
. Dynamization
. Bone transport
. Excision of fibrous tissue and re-osteosynthesis
. Ultrasound stimulation
. Allograft implantation

Correct Answer & Explanation

. Excision of fibrous tissue and re-osteosynthesis

Explanation

Excision of fibrous tissue (débridement) at the nonunion site and re-osteosynthesis, often combined with freshening the bone ends (effectively creating a 'new fracture') and bone grafting, aims to remove the inhibitory fibrous tissue and restart the biological healing cascade by providing a fresh hematoma and improved stability. Dynamization is adjusting existing fixation. Bone transport is for large defects. Ultrasound is a non-invasive stimulator. Allograft is a type of bone graft.

Question 9173

Topic: 2. Trauma

When utilizing a locked intramedullary nail for a comminuted femoral fracture, the goal is typically to achieve relative stability. What type of fracture healing is primarily promoted under these conditions?

. Primary (direct) healing
. Secondary (indirect/endochondral) healing
. Fibrous union
. Delayed union
. Pseudarthrosis formation

Correct Answer & Explanation

. Secondary (indirect/endochondral) healing

Explanation

Locked intramedullary nailing typically provides relative stability, allowing for controlled micromotion at the fracture site. This mechanical environment promotes secondary (indirect or endochondral) fracture healing, characterized by callus formation. Primary healing requires absolute rigidity, which IMN generally does not provide for comminuted fractures.

Question 9174

Topic: 2. Trauma

What is the primary reason why diaphyseal fractures of long bones tend to heal faster than metaphyseal fractures in the same bone, assuming similar patient factors and fracture severity?

. Diaphyseal bone has a richer periosteal blood supply.
. Metaphyseal bone is entirely cortical, leading to slower healing.
. Diaphyseal fractures typically experience less interfragmentary motion.
. The greater marrow cavity in diaphysis provides more progenitor cells.
. Metaphyseal bone has less intrinsic biomechanical stability.

Correct Answer & Explanation

. Diaphyseal bone has a richer periosteal blood supply.

Explanation

Diaphyseal bone often has a more robust periosteal blood supply contributing to callus formation compared to metaphyseal bone, which primarily relies on its endosteal blood supply. Additionally, the periosteum is thicker and more osteogenic in the diaphysis. While metaphyseal bone is largely cancellous (not entirely cortical) and typically has good vascularity, the contribution of the periosteal component is a key differentiating factor in favoring diaphyseal healing.

Question 9175

Topic: 2. Trauma

In a nonunion, the histological appearance of sclerotic bone ends and a wide fibrous gap with minimal cellular activity indicates which type?

. Hypertrophic nonunion
. Oligotrophic nonunion
. Atrophic nonunion
. Pseudarthrosis
. Elephant foot nonunion

Correct Answer & Explanation

. Atrophic nonunion

Explanation

Sclerotic bone ends and a wide fibrous gap with minimal cellular activity are characteristic features of an atrophic nonunion. This signifies a biological failure where there is insufficient biological activity to generate a callus. Hypertrophic and oligotrophic nonunions indicate some biological activity (hypertrophic more than oligotrophic), but inadequate mechanical stability. Pseudarthrosis refers to the development of a false joint, often with a synovial-lined cavity within a nonunion.

Question 9176

Topic: 2. Trauma

Which of the following interventions has been shown to be effective in promoting fracture healing by delivering concentrated growth factors and mesenchymal stem cells directly to the fracture site?

. Systemic administration of NSAIDs
. Application of a plaster cast alone
. Platelet-Rich Plasma (PRP) or Bone Marrow Aspirate Concentrate (BMAC)
. Continuous passive motion (CPM)
. High-dose systemic corticosteroids

Correct Answer & Explanation

. Platelet-Rich Plasma (PRP) or Bone Marrow Aspirate Concentrate (BMAC)

Explanation

Platelet-Rich Plasma (PRP) and Bone Marrow Aspirate Concentrate (BMAC) are biological augmentation techniques that deliver concentrated growth factors, cytokines, and mesenchymal stem cells directly to the fracture site. These can enhance osteoinduction and osteogenesis, particularly useful in delayed unions or nonunions. NSAIDs and corticosteroids hinder healing. A cast provides stability but no biological augmentation. CPM is rehabilitation, not a biological intervention.

Question 9177

Topic: 2. Trauma

Why is avascular necrosis (AVN) a common complication following certain intra-articular fractures, such as femoral neck fractures or talar neck fractures?

. The fracture disrupts the main blood supply to the bone segment, leading to ischemia.
. The intra-articular environment promotes excessive inflammatory response.
. The rich metaphyseal blood supply is overwhelmed by the trauma.
. These fractures typically heal with primary bone healing, which is prone to AVN.
. The fracture causes significant nerve damage, impairing healing.

Correct Answer & Explanation

. The fracture disrupts the main blood supply to the bone segment, leading to ischemia.

Explanation

Avascular necrosis (AVN) is common after certain intra-articular fractures (e.g., femoral neck, talar neck, scaphoid proximal pole) because these bones have a precarious or retrograde blood supply that is frequently disrupted by the fracture, leading to ischemia and subsequent death of the bone tissue. The intra-articular environment itself doesn't promote AVN, but the vascular anatomy combined with fracture location is key. Nerve damage is usually not the direct cause of AVN.

Question 9178

Topic: 2. Trauma

In the context of fracture fixation, a larger Area Moment of Inertia of a bone plate correlates with:

. Increased material fatigue life
. Reduced overall plate weight
. Increased bending stiffness and strength
. Improved biological response at the bone-plate interface
. Decreased stress shielding of the bone

Correct Answer & Explanation

. Increased bending stiffness and strength

Explanation

A larger Area Moment of Inertia (MOI) of a bone plate directly translates to increased bending stiffness and strength of the plate. This is a fundamental principle of structural mechanics, where resistance to deformation (stiffness) and resistance to yielding (strength) under bending or torsion are highly dependent on the MOI of the cross-section. While material fatigue life is important, it's also influenced by stress concentrations and material properties, not solely MOI. Reduced weight and improved biological response are not direct consequences of higher MOI. Increased stiffness from a higher MOI could potentially lead to increased stress shielding, not decreased.

Question 9179

Topic: 2. Trauma

When considering a transverse osteotomy stabilized with a bone plate, where should the plate ideally be positioned on the bone's cross-section to optimize its effectiveness in resisting bending forces?

. Medially, regardless of the expected load
. Laterally, to facilitate screw insertion
. On the tension side of the bone, relative to the anticipated primary bending load
. On the compression side of the bone, relative to the anticipated primary bending load
. Anteriorly, due to easier surgical access

Correct Answer & Explanation

. On the tension side of the bone, relative to the anticipated primary bending load

Explanation

To optimize resistance to bending, the bone plate should ideally be placed on the tension side of the bone. When a bone is bent, one side experiences tensile stress, and the other experiences compressive stress. Plates are most effective when resisting tension, as they prevent the tensile fracture of the bone. For example, in a femoral shaft, if the primary bending moment causes tension laterally, the plate should be placed laterally. This positioning maximizes the lever arm of the plate and enhances its Area Moment of Inertia relative to the composite bone-plate structure, thereby augmenting resistance to the bending moment.

Question 9180

Topic: 2. Trauma

A surgeon is considering two external fixator frame configurations for a comminuted tibia fracture. Frame A uses four pins in a square configuration. Frame B uses six pins in a hexagonal configuration, all with the same diameter and material. Frame B offers superior stability primarily due to:

. Increased number of pins per fragment
. Reduced pin-bone interface stress
. Increased Area Moment of Inertia of the frame's cross-section
. Enhanced biological response
. Decreased overall frame weight

Correct Answer & Explanation

. Increased Area Moment of Inertia of the frame's cross-section

Explanation

Frame B, with six pins in a hexagonal configuration, generally provides superior stability due to an increased Area Moment of Inertia of the frame's cross-section. Distributing the fixation elements (pins, and thus the frame bars) further from the central axis of the bone significantly enhances the frame's resistance to bending and torsion. While more pins also contribute to stability by increasing the bone-pin interface, the geometric arrangement of the frame and the resultant MOI are primary determinants of overall frame stiffness. The number of pins per fragment and pin-bone interface stress are secondary considerations to the overall structural rigidity determined by MOI.

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