Modern Advances in Prosthetics — MCQs
All of the following muscles have dual nerve supply, EXCEPT?
The ideal synthetic material used for femoropopliteal bypass when autologous vein is unavailable is:
When osseous defects amenable to reconstruction are present, technique of choice is?
Which of the following nerve fibre types is least susceptible to LA blockade?
Shortest functional level of trans tibial amputation is:
Most commonly used nerve for monitoring during anesthesia
Which of the following is the metal cofactor of the enzyme ALA dehydratase?
Which of the following flaps is known for having a fixed pivot point at the base?
If severe bony undercuts exist, what is the best treatment?
All of the following factors affect osseointegration EXCEPT:
Modern Advances in Prosthetics Indian Medical PG Practice Questions and MCQs
Question 1: All of the following muscles have dual nerve supply, EXCEPT?
- A. Flexor digitorum profundus
- B. Pectineus
- C. Brachialis
- D. Flexor digitorum superficialis (Correct Answer)
Explanation: No changes were made to the original explanation because none of the provided references met the relevance criteria for the specific muscles and nerves discussed. ***Flexor digitorum superficialis*** - This muscle is solely innervated by the **median nerve**. - It works to **flex the middle phalanges** of the medial four digits. *Flexor digitorum profundus* - The medial half of the muscle, which supplies the ring and little fingers, is innervated by the **ulnar nerve**. - The lateral half, which supplies the index and middle fingers, is innervated by the **anterior interosseous nerve** (a branch of the median nerve). *Pectineus* - This muscle typically receives innervation from both the **femoral nerve** and the **obturator nerve**. - Its primary action is **adduction and flexion of the hip**. *Brachialis* - While primarily innervated by the **musculocutaneous nerve**, a small component also receives innervation from the **radial nerve**. - It is a powerful **flexor of the elbow joint**.
Question 2: The ideal synthetic material used for femoropopliteal bypass when autologous vein is unavailable is:
- A. Dacron
- B. Xenograft
- C. Saphenous vein
- D. PTFE (non-expanded)
- E. Cryopreserved vein graft
- F. ePTFE (Correct Answer)
- . Polyethylene terephthalate (PET)
- . Allograft
Explanation: ***ePTFE (Expanded Polytetrafluoroethylene)*** - **ePTFE** is the preferred synthetic graft for femoropopliteal bypass when autologous vein is unavailable - Offers good **biocompatibility** and relative resistance to **thrombosis** - Provides superior patency rates in above-knee femoropopliteal bypasses compared to other synthetic materials (5-year patency ~50-60%) - The expanded structure allows tissue ingrowth and better integration *Dacron (Polyethylene terephthalate)* - Generally used for **larger diameter vessels** (e.g., aortoiliac grafts) - Has **inferior patency rates** in smaller diameter femoropopliteal position compared to ePTFE - More prone to kinking and associated with higher rates of intimal hyperplasia in peripheral circulation *Saphenous vein* - The autologous saphenous vein is the **gold standard** for femoropopliteal bypass with superior long-term patency (5-year patency ~70-80%) - However, this question specifically asks for synthetic material when vein is unavailable or unsuitable - Not always available or of adequate quality in all patients *PTFE (non-expanded)* - **Non-expanded PTFE** lacks the porous structure of ePTFE - Not used for vascular grafts due to absence of tissue ingrowth capability - The **expanded** form is specifically engineered for vascular applications
Question 3: When osseous defects amenable to reconstruction are present, technique of choice is?
- A. Sulcular flap
- B. Modified Widman flap
- C. Apically displaced flap
- D. Papilla preservation flap (Correct Answer)
Explanation: ***Papilla preservation flap*** - This technique is specifically designed to **preserve the interdental papilla**, which is critical for covering and protecting regenerative materials placed in osseous defects. - By maintaining the integrity of the papilla, it facilitates primary wound closure over the defect, enhancing the predictability of **guided tissue regeneration (GTR)** and bone grafting procedures. *Sulcular flap* - A sulcular flap involves an incision within the sulcus, which typically provides limited access and does not allow for adequate coverage of large **osseous defects**. - It does not offer the tissue volume needed for the stable primary closure essential for regenerative procedures. *Modified Widman flap* - While providing excellent access for debridement in periodontal pockets, the modified Widman flap's incisions often **transect the interdental papilla**, making primary closure over a regenerative defect less ideal. - Its primary goal is root debridement and pocket reduction, not necessarily **papilla preservation** for regenerative purposes. *Apically displaced flap* - An apically displaced flap is designed to **increase the zone of attached gingiva** or reduce pocket depths, by positioning the flap apically to its original position. - This flap design is not suitable for covering osseous defects amenable to reconstruction because it often exposes more root surface and does not provide the necessary coronal coverage for regenerative materials.
Question 4: Which of the following nerve fibre types is least susceptible to LA blockade?
- A. B fibers
- B. A beta
- C. C fibers
- D. A alpha (Correct Answer)
Explanation: **A alpha** - **A alpha fibers** are the **largest** and most heavily myelinated nerve fibers, responsible for **motor function** and **proprioception**. - Due to their large diameter and thick myelination, they have the **highest conduction velocity** and are the **least susceptible to local anesthetic blockade**, requiring higher concentrations or longer exposure times. *B fibers* - **B fibers** are **preganglionic autonomic fibers** that are myelinated but of relatively small diameter. - They are generally **highly sensitive to local anesthetics**, often being blocked even before A-delta and C fibers, due to their specific physiologic properties like repetitive firing and length of node of Ranvier. *C fibers* - **C fibers** are **unmyelinated** and have the **smallest diameter**, transmitting **pain, temperature, and autonomic information**. - Despite being unmyelinated, their small diameter makes them **highly sensitive to local anesthetics**, as the drug can easily penetrate to block sodium channels. *A beta* - **A beta fibers** are large, myelinated fibers involved in transmitting **touch and pressure sensations**. - While myelinated, they are **smaller than A-alpha fibers** and thus more susceptible to local anesthetic blockade than A-alpha, but less so than C or B fibers.
Question 5: Shortest functional level of trans tibial amputation is:
- A. Just proximal to tibial tuberosity
- B. 15 cm distal to joint line
- C. 10 cm distal to joint line
- D. Just distal to tibial tuberosity (Correct Answer)
Explanation: **Just distal to tibial tuberosity** - This level allows for a **short residual limb** but still provides sufficient leverage for effective prosthetic control and weight-bearing. - Amputations at this level generally preserve the **knee joint**, which is crucial for maximizing function and ambulation. *Just proximal to tibial tuberosity* - An amputation **proximal to the tibial tuberosity** would result in a **knee disarticulation** or above-knee amputation, leading to a much greater functional deficit. - This level means losing the **knee joint**, which is not considered a trans-tibial amputation. *15 cm distal to joint line* - This level of amputation would result in a **longer residual limb** than necessary, which can be beneficial, but it's not the *shortest functional* level. - While functional, a longer limb might sometimes present challenges with prosthetic fit or bulk in certain situations. *10 cm distal to joint line* - Similar to 15 cm distal, this length is considered a **standard or optimal length** for trans-tibial amputations, resulting in good function. - However, it is not the **shortest possible functional level** while still retaining an effective limb for prosthetic use.
Question 6: Most commonly used nerve for monitoring during anesthesia
- A. Facial nerve
- B. Ulnar nerve (Correct Answer)
- C. Radial nerve
- D. Median nerve
Explanation: ***Ulnar nerve*** - The **ulnar nerve** is most commonly used for **neuromuscular monitoring** during anesthesia due to its accessibility at the wrist and predictable response to stimulation. - Stimulation typically elicits an adductor pollicis contraction, which is easily observed and quantified with various monitoring devices. *Facial nerve* - The **facial nerve** is primarily monitored during **neurosurgical procedures** where facial nerve integrity is at risk, such as parotidectomy or acoustic neuroma resection. - While it can be monitored, it is not the standard choice for general neuromuscular blockade assessment due to its complex innervation patterns and the need for specific electrode placement. *Radial nerve* - The **radial nerve** is less frequently used for standard neuromuscular monitoring compared to the ulnar nerve. - Its stimulation can lead to more variable and less quantifiable thumb or finger extension, making it less ideal for precise assessment of blockade depth. *Median nerve* - The **median nerve** can be used for neuromuscular monitoring, often stimulating the thenar muscles to produce thumb flexion. - However, it is generally considered a secondary site compared to the ulnar nerve due to greater anatomical variability in electrode placement and response.
Question 7: Which of the following is the metal cofactor of the enzyme ALA dehydratase?
- A. Magnesium
- B. Zinc (Correct Answer)
- C. Lead
- D. Copper
Explanation: ***Zinc*** - **Zinc** acts as a crucial metal ion cofactor for **ALA dehydratase**, also known as **porphobilinogen synthase**. - It plays a vital role in the enzyme's catalytic activity, facilitating the **condensation of two molecules of aminolevulinate (ALA)** to form porphobilinogen. *Copper* - **Copper** is a cofactor for several enzymes, including **cytochrome c oxidase** and **superoxide dismutase**, but it is not the prosthetic group for ALA dehydratase. - While essential for various biological processes, its role does not extend to the direct catalysis of **heme synthesis** at the ALA dehydratase step. *Lead* - **Lead** is a well-known inhibitor of **ALA dehydratase**, not a prosthetic group. - The binding of lead to the enzyme's active site displaces essential cofactors like zinc, leading to the accumulation of **ALA** and causing **lead poisoning**. *Magnesium* - **Magnesium** is an important cofactor for many enzymes involved in **ATP hydrolysis**, **DNA replication**, and **RNA synthesis**. - However, it does not function as the prosthetic group for **ALA dehydratase** in the heme biosynthetic pathway.
Question 8: Which of the following flaps is known for having a fixed pivot point at the base?
- A. Interpolation flap
- B. Rotation flap (Correct Answer)
- C. Advancement flap
- D. Transposition flap
Explanation: ***Rotation flap*** - The **rotation flap** has a **fixed pivot point** at its base and rotates around this point in an arc to cover the adjacent defect. - The flap moves through a rotational movement, maintaining its blood supply through the base, which acts as the pivot. - Commonly used in scalp reconstruction, cheek defects, and trunk defects where rotational movement can close the defect. *Advancement flap* - The **advancement flap** moves forward in a **linear sliding motion** without rotation. - It does not have a fixed pivot point; instead, it advances directly into the defect. - Examples include V-Y advancement and bipedicle advancement flaps. *Transposition flap* - The **transposition flap** moves laterally over intervening normal tissue to reach the defect. - While it rotates, it does not have the same fixed pivot point characteristic as a rotation flap. - Examples include rhomboid flap and bilobed flap. *Interpolation flap* - The **interpolation flap** is transferred over or under intervening tissue, requiring a second stage to divide the pedicle. - It does not have a fixed pivot point at the base in the same manner as rotation flaps. - Examples include forehead flap for nasal reconstruction and cross-finger flap.
Question 9: If severe bony undercuts exist, what is the best treatment?
- A. Remove all undercuts so that no undercut exists (Correct Answer)
- B. Nothing but do only alveolar ridge contouring
- C. Remove undercut on one side
- D. None of the above
Explanation: ***Remove all undercuts so that no undercut exists*** - **Severe bony undercuts** can prevent the proper seating and insertion of a removable prosthesis, leading to trauma and instability. - **Complete removal** of such undercuts creates a uniform, unobstructed path of insertion, ensuring the prosthesis can be placed and removed without damaging tissues. *Nothing but do only alveolar ridge contouring* - **Alveolar ridge contouring** alone might not be sufficient to address severe bony undercuts, as these often involve areas beyond the immediate ridge crest. - Leaving severe undercuts can still cause ongoing **trauma** to the soft tissues during prosthesis insertion and removal, leading to pain and ulceration. *Remove undercut on one side* - Removing undercuts on only one side while leaving others untreated can lead to a **compromised path of insertion**. - This approach may not fully resolve the problem, potentially still causing difficulty in seating the prosthesis or leading to **uneven stress distribution** upon insertion. *None of the above* - This option is incorrect because removing all severe bony undercuts is indeed a standard and often necessary treatment to ensure successful prosthetic rehabilitation.
Question 10: All of the following factors affect osseointegration EXCEPT:
- A. Biocompatibility of implant material.
- B. Implant design.
- C. Patient's blood type (Correct Answer)
- D. Status of the host bed.
Explanation: ***Patient's blood type*** - A patient's **blood type** (e.g., A, B, AB, O) is determined by antigens present on red blood cells and plays no direct role in the biological processes of bone healing or the integration of a dental implant with bone. - While systemic factors can influence osseointegration, blood type itself does not affect the cellular and molecular mechanisms required for direct bone-to-implant contact. *Biocompatibility of implant material* - The **biocompatibility** of the implant material (e.g., **titanium**) is crucial for osseointegration, as it must not elicit adverse reactions and must permit host bone growth on its surface. - Materials that are cytotoxic or inflammatory will prevent bone apposition and lead to fibrous encapsulation rather than direct bone contact. *Implant design* - **Implant design**, including features like **surface roughness**, thread pitch, and macro-geometry, significantly influences the initial stability and long-term success of osseointegration. - A greater surface area and appropriate surface treatments can enhance bone cell attachment and differentiation, promoting faster and stronger bone integration. *Status of the host bed* - The **status of the host bone bed** refers to its quality and quantity (e.g., bone density, vascularity), which are critical for the biological processes of osseointegration. - Adequate bone volume and good bone quality provide a stable foundation and sufficient blood supply for bone regeneration around the implant.
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