Basic Science in Orthopaedics Practice Questions

Q: Tinel's sign that is positive and non-progressive is seen in:

Neurotmesis. ***Neurotmesis*** - A positive and non-progressive **Tinel's sign** indicates that regenerating nerve fibers are unable to cross an existing **neuroma** or scar tissue, which is characteristic of **neurotmesis**. - In **neurotmesis**, there is a complete disruption of the axon, myelin, and surrounding connective tissue, making regeneration across the gap highly improbable without surgical intervention. *Neuropraxia* - In **neuropraxia**, there is a **concussion** of the nerve without disruption of the axon; nerve conduction is temporarily blocked. - A **Tinel's sign** is typically **negative** in neuropraxia because there is no axonal regeneration occurring and the nerve is fundamentally intact. *Axonotmesis* - **Axonotmesis** involves axonal disruption, but the **endoneurium** and other connective tissue layers remain intact. - While regeneration occurs in axonotmesis, a **Tinel's sign** would typically be **progressive**, indicating the advancement of regenerating axons, rather than non-progressive. *All of the options* - This option is incorrect because **neuropraxia** generally does not present with a positive Tinel's sign, and in **axonotmesis**, the sign should be progressive, not non-progressive.

Q: Avascular necrosis of bone is LEAST likely to be associated with?

Osgood -Schlatter disease. ***Osgood-Schlatter disease*** - This condition is characterized by **inflammation of the patellar ligament** at its insertion into the tibial tuberosity, primarily due to repetitive stress in adolescents. - While it involves pain and swelling around the knee, it is a **traction apophysitis** and not a form of avascular necrosis. *Long-term use of corticosteroids* - **Corticosteroids** are a well-established risk factor for avascular necrosis, particularly in the femoral head, by affecting lipid metabolism and blood flow. - They can lead to **fat embolism** and increased intraosseous pressure, compromising blood supply to the bone. *Sickle-cell disease* - **Sickle cell disease** significantly increases the risk of avascular necrosis due to **vaso-occlusive crises**, where sickled red blood cells block small blood vessels. - This leads to **ischemia and infarction** in bone marrow, commonly affecting the femoral and humeral heads. *Legg-Perthes disease* - This is a specific type of **avascular necrosis of the femoral head** in children, causing a temporary interruption of blood supply to the epiphysis. - It results in the collapse of the femoral head and subsequent repair processes, consistent with the pathology of avascular necrosis.

Q: Which of the following is TRUE about bone healing in elderly patients?

Delayed Union is More Common. ***Delayed Union is More Common*** - **Aging** is associated with a decrease in the number and activity of **osteoblasts** and stem cells, leading to a slower bone remodeling process. - Reduced **blood supply** to the fracture site and the presence of comorbidities in elderly patients contribute to delayed healing and an increased risk of complications like non-union. *Enhanced Angiogenesis* - **Angiogenesis**, the formation of new blood vessels, tends to be reduced in elderly patients due to age-related changes in growth factor production and endothelial cell function. - A compromised blood supply to the fracture site negatively impacts the delivery of essential nutrients and cells required for bone repair. *Better Callus Formation* - **Callus formation**, a crucial step in secondary bone healing, is often impaired in elderly individuals. - This impairment is due to decreased cellular activity, reduced growth factor production, and a less robust inflammatory response. *Faster Healing Rate* - Bone healing is generally **slower** in elderly patients compared to younger individuals. - This diminished healing rate is attributed to a decline in osteogenic potential, reduced vascularity, and frequently, poorer overall health status.

Q: What does the Sunderland classification specifically categorize?

Nerve injury. ***Nerve injury*** - The **Sunderland classification** is a widely used system to categorize the severity of **peripheral nerve injuries** based on the degree of damage to the nerve components. - It expands upon the simpler Seddon classification (**neuropraxia, axonotmesis, neurotmesis**) by adding more detailed grades of axon and connective tissue damage. *Muscle injury* - **Muscle injuries** are typically classified using systems that describe the extent of fiber disruption, hematoma formation, and involvement of the fascia, such as the **British Athletics Muscle Injury Classification (BAMIC)**, not the Sunderland classification. - These classifications focus on the structural integrity of muscle tissue and its functional implications. *Tendon injury* - **Tendon injuries** are classified based on their severity (e.g., tendinopathy, partial tear, complete rupture) and location, often using systems like the **Blazina classification** for patellar tendinopathy. - The Sunderland classification is specific to nerve damage, not connective tissues like tendons. *Ligament injury* - **Ligament injuries** are typically graded from I to III, indicating a sprain, partial tear, or complete rupture, respectively, often with associated joint instability. - Classifications for ligament injuries, such as those used for ankle sprains or ACL tears, do not align with the Sunderland system for nerve damage.

Q: Callus formation is seen between what duration of fracture healing?

4 - 12 weeks. ***4 - 12 weeks*** - This period aligns with the **reparative phase** of fracture healing, where both **soft callus** (fibrocartilaginous) and then **hard callus** (woven bone) are formed. - Callus formation during this time significantly contributes to the **mechanical stability** of the fracture site. *0 - 2 weeks* - This initial phase primarily involves the **inflammatory stage**, characterized by **hematoma formation** and the recruitment of inflammatory cells. - While essential for initiating healing, significant structural callus formation does not typically occur within this timeframe. *2 - 4 weeks* - This period marks the transition from the inflammatory to the reparative phase, with the initial development of a **soft callus**. - However, the more robust and radiographically evident **hard callus formation** extends beyond this period. *12 - 16 weeks* - By this stage, the fracture is generally in the **remodeling phase**, where the woven bone of the hard callus is gradually replaced by **lamellar bone**. - While callus is present, its formation is more accurately described in the earlier 4-12 week period; this stage focuses on refinement and strengthening.

Q: What is the characteristic feature of neuropraxia?

No structural damage to the nerve. ***No structural damage to the nerve*** - **Neuropraxia** is the mildest form of nerve injury, characterized by a **temporary block in nerve conduction** without structural damage to the axon or surrounding connective tissues. - This typically results in **temporary sensory and/or motor deficits** that fully resolve within weeks to months. *Damage to the endoneurium* - Damage to the **endoneurium** would indicate a more severe injury, such as **axonotmesis**, where the axon is damaged but the connective tissue sheaths are preserved. - This level of injury suggests that wallerian degeneration would occur distal to the lesion, leading to **slower and incomplete recovery**. *Damage to the epineurium* - Damage to the **epineurium**, along with the endoneurium and perineurium, signifies **neurotmesis**, the most severe nerve injury. - This involves a **complete transection of the nerve**, requiring surgical intervention for any chance of functional recovery. *Damage to the axon* - Damage to the **axon** itself, often alongside preserved connective tissues, is characteristic of **axonotmesis**. - While recovery is possible through axonal regeneration, it is **slower and less complete** than in neuropraxia.

Q: Saturday night palsy is which type of nerve injury?

Neuropraxia. ***Neuropraxia*** - This is the mildest form of nerve injury, involving a **temporary conduction block** without axonal disruption, often due to **compression** or mild stretching. - **Saturday night palsy**, caused by prolonged compression of the radial nerve, is a classic example, characterized by rapid and complete recovery, typically within days to weeks. *Axonotemesis* - This involves **axon damage** and Wallerian degeneration distal to the injury, but the **endoneurium and connective tissue sheaths remain intact**. - Recovery is slower and often incomplete, as it requires axonal regeneration through the preserved connective tissue tubes, taking months. *Neurotmesis* - This is the most severe type of nerve injury, involving **complete transection of the nerve fiber**, including the axon, myelin, and all connective tissue sheaths. - Recovery is often poor and requires surgical intervention to attempt re-approximation of the nerve ends. *Complete section* - This term is largely synonymous with **neurotmesis**, indicating a full anatomical disruption of the nerve. - It involves the severance of all nerve components, leading to complete loss of function distal to the injury and the poorest prognosis for spontaneous recovery.

Q: Heterotopic ossification is primarily associated with which of the following?

Soft tissues. ***Soft tissues*** - **Heterotopic ossification** is the pathological formation of mature, lamellar bone in **non-osseous (soft tissues)** where bone does not normally exist. - This process often occurs in muscles, tendons, ligaments, or fascia, particularly after trauma or neurological injury. *Bone* - Heterotopic ossification is the formation of bone *outside* of normal skeletal structures, not within existing bone. - While it involves bone formation, its defining characteristic is its location in **extraskeletal sites**, not within the bone itself. *Joint* - Although heterotopic ossification can occur around joints, leading to **joint stiffness** and limited range of motion, it is the formation of bone within the **soft tissues surrounding the joint**, not within the joint capsule or articular cartilage itself. - The primary location is the adjacent soft tissue, which then secondarily impacts joint mobility. *None of the options* - This option is incorrect because "Soft tissues" accurately describes the primary location where heterotopic ossification occurs. - The condition is specifically defined by bone formation in these non-skeletal sites.

Q: Which of the following methods is used for titanium investment casting?

Casting under vacuum in an argon atmosphere. ***Casting under vacuum in an argon atmosphere*** - **Titanium** is highly reactive at casting temperatures and will readily oxidize in the presence of oxygen or nitrogen, hence why it must be cast in a **vacuum** or an **inert atmosphere** like argon. - The vacuum environment prevents oxidation, while the argon atmosphere further ensures an inert environment, protecting the molten titanium from atmospheric contaminants. *Casting under air pressure in a nitrogen atmosphere* - **Nitrogen** reacts with molten titanium to form titanium nitride, which is a brittle compound, compromising the mechanical properties of the cast. - Casting under **air pressure** would introduce oxygen, leading to significant oxidation and degradation of the titanium. *Using aluminum vanadium crucibles for casting* - **Aluminum vanadium** is an alloy often used with titanium, but it is not suitable as a crucible material because molten titanium would react with and dissolve the crucible. - Crucibles for titanium casting must generally be made of non-reactive materials like **graphite** or specialized ceramic crucibles. *Using CAD-CAM for design* - **CAD-CAM** (Computer-Aided Design/Computer-Aided Manufacturing) is a design and manufacturing tool used to create patterns and molds, but it is not a method for the actual casting process itself. - While CAD-CAM is often employed in the preparation of titanium prostheses, it pertains to the **design and fabrication of the mold**, not the environment of the molten metal during casting.

Question 1

Placing cast under tap water is to be avoided as

Accepted Answer

Gypsum is slightly soluble in water and the surface of the cast will be eroded

Answer

H2O Inhibits polymerization of dental resin

Answer

H2O interferes with hygroscopic expansion

Answer

H2O interferes with crystallization of dihydrate

Question 2

Tinel's sign that is positive and non-progressive is seen in:

Accepted Answer

Neurotmesis

Answer

Neuropraxia

Answer

Axonotmesis

Answer

All of the options

Question 3

Avascular necrosis of bone is LEAST likely to be associated with?

Accepted Answer

Osgood -Schlatter disease

Answer

Long-term use of corticosteroids

Answer

Sickle-cell disease

Answer

Legg-Perthes disease

Question 4

Which of the following is TRUE about bone healing in elderly patients?

Accepted Answer

Delayed Union is More Common

Answer

Enhanced Angiogenesis

Answer

Better Callus Formation

Answer

Faster Healing Rate

Question 5

What does the Sunderland classification specifically categorize?

Accepted Answer

Nerve injury

Answer

Muscle injury

Answer

Tendon injury

Answer

Ligament injury

Question 6

Callus formation is seen between what duration of fracture healing?

Accepted Answer

4 - 12 weeks

Answer

12 - 16 weeks

Answer

2 - 4 weeks

Answer

0 - 2 weeks

Question 7

What is the characteristic feature of neuropraxia?

Accepted Answer

No structural damage to the nerve

Answer

Damage to the endoneurium

Answer

Damage to the epineurium

Answer

Damage to the axon

Question 8

Saturday night palsy is which type of nerve injury?

Accepted Answer

Neuropraxia

Answer

Axonotemesis

Answer

Complete section

Answer

Neurotmesis

Question 9

Heterotopic ossification is primarily associated with which of the following?

Accepted Answer

Soft tissues

Answer

Bone

Answer

Joint

Answer

None of the options

Question 10

Which of the following methods is used for titanium investment casting?

Accepted Answer

Casting under vacuum in an argon atmosphere

Answer

Casting under air pressure in a nitrogen atmosphere

Answer

Using aluminum vanadium crucibles for casting

Answer

Using CAD-CAM for design

Basic Science in Orthopaedics — MCQs

Basic Science in Orthopaedics — MCQs

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