Image-Guided Surgery — MCQs
Fracture neck of femur in 80-year-old male sustained 1 week ago. The treatment of choice is -
Stereotactic Radiosurgery is a form of –
Identify the marked structure in the given image.
Recommended angle of root end resection is:
A child presents with painful limp and restricted hip rotation. ESR and CRP are elevated. Initial plain radiograph is normal. What is the next best imaging study?
Identify the implant shown in the image:
In a patient with a metallic foreign body in the eye, which investigation should NOT be done?
Air embolism in neural surgery maximum in which position:
What does the given image show?
A surgeon experiences pin-site fracture during reference array fixation in computer-navigated TKA in an osteoporotic patient. Subsequently, three more cases develop similar complications. What systematic approach should be implemented to prevent this complication?
Image-Guided Surgery Indian Medical PG Practice Questions and MCQs
Question 1: Fracture neck of femur in 80-year-old male sustained 1 week ago. The treatment of choice is -
- A. Hemiarthroplasty (Correct Answer)
- B. Closed reduction and fixation with three cancellous screws
- C. Longitudinal skin traction for 6 weeks
- D. Excision arthroplasty
Explanation: ***Hemiarthroplasty*** - For an 80-year-old with a **fracture of the femoral neck**, especially if sustained a week ago, **hemiarthroplasty** is the preferred treatment to allow early mobilization and prevent complications of prolonged recumbency. - This procedure replaces the **femoral head** and neck, minimizing the risk of **avascular necrosis** and **non-union** which are common complications in older patients with displaced femoral neck fractures. *Excision arthroplasty* - **Excision arthroplasty**, also known as **Girdlestone arthroplasty**, is a salvage procedure typically reserved for cases of severe infection, failed prosthetic implants, or when other options are not viable. - It involves removing the femoral head, creating a **pseudarthrosis**, and results in a shortened, unstable limb, making it unsuitable as a primary treatment. *Closed reduction and fixation with three cancellous screws* - This option is generally considered for **younger patients** with undisplaced or minimally displaced **femoral neck fractures** due to better bone quality and lower risk of avascular necrosis. - In an 80-year-old, the risks of **non-union** and **avascular necrosis** are significantly higher, and the prolonged weight-bearing restrictions associated with this method are detrimental. *Longitudinal skin traction for 6 weeks* - Prolonged **skin traction** is rarely used for femoral neck fractures, especially in the elderly, due to the high risk of complications such as **skin breakdown**, **deep vein thrombosis**, **pneumonia**, and **muscle atrophy**. - It does not provide definitive fixation and is not a definitive treatment for a bony fracture.
Question 2: Stereotactic Radiosurgery is a form of –
- A. Radioiodine therapy
- B. Cryosurgery
- C. Robotic Surgery
- D. Radiotherapy (Correct Answer)
Explanation: ***Radiotherapy*** - **Stereotactic radiosurgery** is a highly precise form of **radiotherapy** that delivers a single high dose or multiple fractionated high doses of radiation to a specific target area. - It uses focused **radiation beams** to treat tumors or other lesions, often as an alternative to conventional surgery, by causing damage to the DNA of target cells. *Radioiodine therapy* - **Radioiodine therapy** primarily uses **iodine-131** to treat thyroid conditions like hyperthyroidism or thyroid cancer. - This involves the patient ingesting a radioactive isotope, unlike the external radiation beams used in radiosurgery. *Cryo Surgery* - **Cryosurgery** involves the use of **extreme cold** to destroy abnormal tissues. - It is a physical method of tissue destruction and does not involve radiation. *Robotic Surgery* - **Robotic surgery** utilizes robotic systems to assist in performing surgical procedures, enhancing precision, and control for the surgeon. - This is a mode of performing traditional surgery and does not involve radiation as its primary therapeutic agent.
Question 3: Identify the marked structure in the given image.
- A. Electrode
- B. Coil (Correct Answer)
- C. Magnet
- D. Processor
Explanation: ***Coil*** - The marked structure appears to be a **cochlear implant's internal coil**, which is common in X-ray imaging of these devices. - The **cochlear implant internal coil** is crucial for transmitting processed sound signals via electromagnetic induction to the electrode array within the cochlea. *Electrode* - An **electrode array** is typically a thin, flexible wire with multiple contacts inserted into the cochlea, which is not what the arrow is pointing to directly. - While electrodes are part of a cochlear implant, the marked structure's shape and position are more consistent with the **internal coil** that connects to the electrode array. *Magnet* - A **magnet** is present in a cochlear implant system, typically in both the external processor and internal receiver, to hold these two components together through the skin. - Magnets usually appear as dense, circular structures in X-rays, often seen more anteriorly or superiorly to the coil for external component alignment. *Processor* - The **processor** for a cochlear implant is an external device worn behind the ear, not an implanted component visible on an X-ray. It processes sound and sends it to the internal coil. - The structures seen in the X-ray are **implanted components** of the cochlear implant, not the external sound processor.
Question 4: Recommended angle of root end resection is:
- A. 30 degrees
- B. 0 degrees (Correct Answer)
- C. 15 degrees
- D. 45 degrees
Explanation: ***0 degrees*** - A **0-degree** resection angle is recommended to minimize the number of exposed **dentinal tubules** and therefore potential **leakage channels**, fostering better apical sealing. - This approach aims for a **flat** or perpendicular cut to the long axis of the tooth, preserving as much root structure as possible. *30 degrees* - A **30-degree** resection angle would expose a significantly larger number of **dentinal tubules** and increase the risk of **apical leakage**. - It would also unnecessarily remove more **root structure**, which could weaken the tooth. *15 degrees* - While less severe than 30 or 45 degrees, a **15-degree** angle still exposes more **dentinal tubules** and creates a larger surface area for potential **leakage** compared to a 0-degree resection. - This angle is not considered ideal for maximizing the **seal** and preserving root integrity. *45 degrees* - A **45-degree** resection angle is associated with the **greatest exposure** of **dentinal tubules** and the highest risk of **microleakage**. - This aggressive angle also leads to the removal of the most **root structure**, potentially compromising the **tooth's stability**.
Question 5: A child presents with painful limp and restricted hip rotation. ESR and CRP are elevated. Initial plain radiograph is normal. What is the next best imaging study?
- A. CT Scan
- B. MRI with contrast (Correct Answer)
- C. Bone Scan
- D. Plain Radiograph
Explanation: ***MRI with contrast*** - An **MRI with contrast** is the most sensitive and specific imaging modality for detecting early changes in **osteomyelitis** or **septic arthritis**, which are serious conditions given the child's symptoms and elevated inflammatory markers. - It can visualize soft tissue and bone marrow edema, joint effusions, and abscesses, guiding immediate treatment. *CT Scan* - While useful for bony detail, a CT scan is **less sensitive than MRI** for detecting early bone marrow changes or soft tissue inflammation in the hip joint. - It also involves **radiation exposure**, which should be limited in children when other effective modalities are available. *Bone Scan* - A bone scan using **technetium-99m** is sensitive for detecting increased bone turnover, but it is **not specific for infection** and cannot differentiate between inflammatory processes, tumors, or fractures. - It provides less anatomical detail compared to MRI, making precise localization of an infection more challenging. *Plain Radiograph* - Plain radiographs are typically the **initial imaging study** for orthopedic complaints but are often **normal in early stages** of septic arthritis or osteomyelitis. - Significant radiographic changes, such as bone erosion or joint space widening, usually appear much later in the disease process.
Question 6: Identify the implant shown in the image:
- A. Dynamic hip screw (Correct Answer)
- B. Cannulated hip screw
- C. Condylar hip screw
- D. Intramedullary nail
Explanation: ***Dynamic hip screw*** - The image shows a **lag screw** inserted into the femoral neck and head, which slides within a **side plate** attached to the femoral shaft with cortical screws. - This construct allows for controlled **dynamic collapse** and impaction at the fracture site, promoting healing and providing stable fixation for **extracapsular hip fractures**. *Cannulated hip screw* - Cannulated screws are typically used in a **parallel configuration** or as a single large screw for hip fractures, particularly **femoral neck fractures**. - They do not feature a **side plate** that extends down the femoral shaft for additional fixation. *Condylar hip screw* - A condylar hip screw (DCS) is used for **distal femur fractures**, often extending into the **condyles**. - It involves a different angulation and design compared to the proximal femoral implant seen, which is fixed to the femoral shaft. *Intramedullary nail* - An intramedullary nail is inserted into the **medullary canal** of the bone, running through its center. - While some hip nails (e.g., trochanteric nails) have a cephalic screw component, they primarily stabilize the shaft from within, unlike the **extracortical side plate** seen here.
Question 7: In a patient with a metallic foreign body in the eye, which investigation should NOT be done?
- A. X-ray
- B. MRI (Correct Answer)
- C. CT
- D. USG
Explanation: ***MRI*** - **Magnetic Resonance Imaging (MRI)** is contraindicated in patients with suspected **metallic foreign bodies** in the eye. - The powerful magnetic fields of an MRI can cause the metallic object to move, potentially leading to further **tissue damage** or even loss of vision. *X-ray* - **X-rays** are often the initial investigation of choice for detecting **radio-opaque foreign bodies** within the eye. - They can effectively localize larger metallic objects and are readily available in most emergency settings. *CT* - **Computed Tomography (CT)** scans provide detailed cross-sectional images and are excellent for precisely localizing **intraocular foreign bodies**, especially smaller ones. - CT can differentiate between metallic and non-metallic objects and assess for associated injuries like orbital fractures. *USG* - **Ultrasound (USG)** of the eye can be useful for detecting **intraocular foreign bodies**, especially if they are non-metallic or located in the posterior segment. - It can also assess for associated complications such as **retinal detachment** or vitreous hemorrhage.
Question 8: Air embolism in neural surgery maximum in which position:
- A. Left lateral
- B. Sitting (Correct Answer)
- C. Supine
- D. Trendelenburg
Explanation: ***Sitting*** - In the **sitting position** for neural surgery, the surgical field, particularly the head, is often elevated above the heart. This creates a **negative pressure gradient** in the venous system, increasing the risk of air entrainment if a vein is opened and air is allowed to enter. - The **higher elevation of the operative site** relative to the right atrium significantly increases the likelihood of air being sucked into open veins. *Left lateral* - While air embolism can occur in any position, the **left lateral position** does not inherently create the same significant negative pressure gradient as the sitting position in the surgical field relative to the heart. - The patient's body is positioned on its side, which can help in certain surgical approaches but typically does not elevate the head as dramatically as the sitting position. *Supine* - In the **supine position**, the patient is lying on their back, and the operative field (head or spine) is generally at or below the level of the heart, reducing the pressure gradient that favors air entrainment. - This position typically offers a **lower risk of air embolism** compared to the sitting position due to less negative pressure in exposed veins. *Trendelenburg* - The **Trendelenburg position** involves placing the patient head-down and feet-up, which increases venous pressure in the upper body and head. - This position actively works against the negative pressure gradient, thereby **reducing the risk of air entrainment** into open veins through increased venous pressure.
Question 9: What does the given image show?
- A. Doyen's periosteal elevator (Correct Answer)
- B. Cobb's spinal elevator
- C. Leksell's rongeur
- D. Key periosteal elevator
Explanation: ***Doyen's periosteal elevator*** - This instrument is characterized by its **curved, spoon-like working end** and solid handle, designed for **elevating the periosteum** from bone. - Doyen's elevator comes in various sizes and angles, but the distinct hook-like curve is a key identifying feature, distinguishing it from other elevators. *Cobb's spinal elevator* - Cobb's elevator typically has a **flat, broad, and slightly curved blade** with a rounded or tapered tip, suitable for dissecting along bony surfaces, particularly in spinal surgery. - Its design prioritizes broad, even separation of tissue layers, contrasting with the more acute curve of the Doyen's. *Leksell's rongeur* - A rongeur is a biting instrument used for **gnawing away bone or tough tissue**, characterized by hinged jaws with sharp, cup-shaped ends. - The image clearly shows a single-piece instrument without hinged jaws, ruling out a rongeur. *Key periosteal elevator* - The Key elevator typically features a **broader, more rounded or slightly angled tip** and a flat, somewhat spatula-like working end, used for general periosteal elevation. - While also a periosteal elevator, its working end does not exhibit the characteristic deep, hook-like curve seen in the Doyen's elevator.
Question 10: A surgeon experiences pin-site fracture during reference array fixation in computer-navigated TKA in an osteoporotic patient. Subsequently, three more cases develop similar complications. What systematic approach should be implemented to prevent this complication?
- A. Switch to electromagnetic navigation system
- B. Use unicortical pins instead of bicortical pins with reduced insertion torque protocol (Correct Answer)
- C. Abandon navigation in all osteoporotic patients
- D. Increase pin diameter for better fixation
Explanation: ***Use unicortical pins instead of bicortical pins with reduced insertion torque protocol*** - **Pin-site fractures** are a known complication in navigated TKA, especially in **osteoporotic bone**, and can be mitigated by reducing the **stress risers** created by drilling. - Using **unicortical pins** and avoiding power drivers to limit **insertion torque** provides sufficient stability for reference arrays while minimizing the risk of cortical failure. *Switch to electromagnetic navigation system* - **Electromagnetic navigation** aims to resolve line-of-sight issues but does not inherently eliminate the need for stable skeletal fixation of reference sensors. - Switching systems is a costly equipment change that does not directly address the underlying **biomechanical failure** of the bone-pin interface in osteoporosis. *Abandon navigation in all osteoporotic patients* - Abandoning navigation denies the patient population the benefits of **precise alignment** and component positioning where it is often most needed due to poor bone quality. - Systematic technical modifications are preferred over total abandonment of a beneficial **surgical technology**. *Increase pin diameter for better fixation* - Increasing the **pin diameter** is counterproductive as larger holes create larger **stress concentrators**, significantly increasing the risk of **periprosthetic fracture** in brittle bone. - A thicker pin displaces more cortical volume, which reduces the **structural integrity** of the femur or tibia in osteoporotic patients.
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