Bone Grafting Techniques — MCQs
The graft with the maximum osteogenic potential is:
Highest point of iliac crest is seen at?
Which of the following is the POOREST recipient bed for a skin graft?
Best procedure for an injury to the leg with exposed bone and skin loss:
The type of graft best suited for renal transplantation is:
The best material for below-inguinal arterial graft is:
Which of the following tests is not used to assess the biocompatibility of dental materials?
Compression osteosynthesis may be used in all these areas except?
What is application of Plaster of Paris all around the surface called ?
When using low-flow circle absorber techniques, the uptake of nitrous oxide must be considered. In a healthy 70 kg adult, the expected uptake of nitrous oxide, with a 70% inspired concentration, after 1.5 hours would be about
Bone Grafting Techniques Indian Medical PG Practice Questions and MCQs
Question 1: The graft with the maximum osteogenic potential is:
- A. Allograft
- B. xenograft
- C. Autocortical
- D. autocancellus (Correct Answer)
Explanation: ***autocancellus*** - **Autocancellous** bone grafts are considered the gold standard due to their high osteogenic potential as they contain **viable osteoblasts** and **bone marrow stromal cells**. - The porous structure of cancellous bone also provides a **scaffold** for new bone formation and excellent revascularization. *Allograft* - **Allografts** are grafts transferred between genetically dissimilar individuals of the same species and are **osteoconductive** and **osteoinductive** but lack viable cells and thus have lower osteogenic potential than autografts. - They undergo sterilization processes that can further reduce their osteoinductive properties and may elicit an **immune response** from the recipient. *xenograft* - **Xenografts** are grafts transferred between different species and primarily serve as an **osteoconductive scaffold**. - They lack live osteogenic cells and have the **lowest osteogenic potential** due to significant immunological barriers and species-specific biochemical differences. *Autocortical* - **Autocortical** grafts are structural and provide mechanical support, but their **osteogenic potential is lower** than cancellous bone. - Cortical bone has a denser structure with fewer viable cells and a slower revascularization rate compared to cancellous bone.
Question 2: Highest point of iliac crest is seen at?
- A. L3
- B. L4 (Correct Answer)
- C. S2
- D. S1
Explanation: ***L4*** - The **highest point of the iliac crest** typically corresponds to the level of the **L4 vertebral body**. - This anatomical landmark is crucial for procedures like **lumbar punctures** and determining the location for **epidural anesthesia**. *L3* - The L3 vertebral level is generally located slightly **above the highest point of the iliac crest**. - While close, it is not the most consistent anatomical correlation for the highest point. *S2* - The **S2 vertebral level** is significantly **below the iliac crests**, marking the approximate midpoint of the sacroiliac joint. - This level is used as a landmark for the **dermatome of the posterior thigh**. *S1* - The **S1 vertebral level** is also located **below the iliac crests**, forming the most superior segment of the sacrum. - It is used as a landmark for the **dermatome of the lateral foot and posterior leg**, and corresponds to the ankle jerk reflex.
Question 3: Which of the following is the POOREST recipient bed for a skin graft?
- A. Fat (Correct Answer)
- B. Muscle
- C. Deep fascia
- D. Skull bone
Explanation: ***Fat*** - **Fat** is a poor recipient for a skin graft due to its **limited vascularity**, which hinders the necessary process of revascularization for graft survival. - The high metabolic demand of a graft cannot be adequately met by the relatively avascular subcutaneous fat, leading to graft failure. *Muscle* - **Muscle tissue** is an excellent recipient bed for skin grafts due to its **rich blood supply**. - Its robust vascularity effectively supports the revascularization and survival of the grafted tissue. *Deep fascia* - **Deep fascia** provides a good vascularized bed for skin grafts, as it has a reasonable blood supply from underlying muscles and surrounding tissues. - This vascularization is sufficient to nourish and ensure the take of a skin graft. *Skull bone* - **Skull bone** (specifically the periosteum covering it) can serve as an adequate graft bed due to its vascular supply. - If the **periosteum** is intact and healthy, it offers sufficient blood flow for graft survival.
Question 4: Best procedure for an injury to the leg with exposed bone and skin loss:
- A. Full thickness grafting
- B. Skin flap
- C. Split skin grafting
- D. Pedicle flap (Correct Answer)
Explanation: ***Pedicle flap*** - A pedicle flap provides **vascularized tissue** that can cover exposed bone, which requires a robust blood supply for healing and protection. - This method ensures good **tissue viability** and bulk, crucial for areas with high functional demands and potential for infection like the lower leg. *Full thickness grafting* - **Full-thickness skin grafts** are generally too thin to adequately cover exposed bone and do not provide sufficient vascularity or padding. - They rely entirely on the recipient bed for vascularization, which is poor over exposed bone, leading to a high risk of **graft failure**. *Skin flap* - While a generic "skin flap" implies a vascularized tissue transfer, it is less specific than a pedicle flap, which ensures continuous blood supply from the donor site until full integration. - The term "skin flap" alone doesn't specify if it's a local, regional, or free flap, and **pedicle flaps** are often the most direct and reliable solution for lower leg bone exposure. *Split skin grafting* - **Split-thickness skin grafts** are very thin and contain only a portion of the dermis, making them unsuitable for covering exposed bone or tendons. - They would likely **fail to take** due to lack of a vascular bed and offer no padding or protection against further injury.
Question 5: The type of graft best suited for renal transplantation is:
- A. Xenograft
- B. Autograft
- C. Allograft
- D. Isograft (Correct Answer)
Explanation: ***Isograft*** - An **isograft** is a transplant between **genetically identical individuals** (e.g., identical twins), leading to no immune rejection. - In renal transplantation, an isograft is ideal as it eliminates the need for **immunosuppressive drugs** and their associated side effects. *Xenograft* - A **xenograft** involves transplantation between **different species** (e.g., pig to human). - Xenografts face significant challenges due to **hyperacute rejection** caused by pre-existing natural antibodies. *Autograft* - An **autograft** is a transplant from one part of the body to another in the **same individual**. - While there is no immune rejection, it is not applicable for renal transplantation as the recipient's own kidneys are diseased. *Allograft* - An **allograft** is a transplant between **genetically different individuals of the same species**. - While common in renal transplantation, allografts still require **lifelong immunosuppression** to prevent rejection, distinguishing them from the ideal isograft.
Question 6: The best material for below-inguinal arterial graft is:
- A. Saphenous vein graft (upside-down) (Correct Answer)
- B. Cryopreserved vein
- C. Dacron
- D. PTFE
Explanation: ***Saphenous vein graft (upside-down)*** - The **autologous saphenous vein** is the material of choice for below-inguinal arterial bypasses due to its superior patency rates compared to synthetic grafts. - It is often harvested and implanted **'upside-down' (reversed)** to ensure the valves do not obstruct blood flow, or can be used *in situ* after rendering the valves incompetent. - Five-year patency rates for autologous vein grafts exceed 70-80% for femoropopliteal bypasses. *Cryopreserved vein* - **Cryopreserved saphenous vein allografts** are an alternative when autologous vein is unavailable or inadequate. - However, they have **significantly lower patency rates** compared to autologous vein grafts due to immunological responses and structural degradation. - They are generally reserved for salvage situations or as a bridge in limb-threatening ischemia. *Dacron* - **Dacron (polyethylene terephthalate)** grafts are primarily used for large-diameter arterial replacements, such as in **aortic bypasses**, and are less suitable for smaller, high-resistance vessels below the inguinal ligament. - They tend to have higher rates of **thrombosis** and infection when used in infra-inguinal positions compared to vein grafts. *PTFE* - **Polytetrafluoroethylene (PTFE)** grafts have lower patency rates than autologous vein grafts, particularly in smaller diameter vessels and below-knee positions, due to issues like **intimal hyperplasia** at the anastomoses. - While suitable when autologous vein is unavailable, it is generally considered inferior for below-inguinal peripheral arterial disease, with 3-year patency rates around 50-60% for above-knee and 30-40% for below-knee positions.
Question 7: Which of the following tests is not used to assess the biocompatibility of dental materials?
- A. Implantation test
- B. Sensitization test
- C. Ames test (Correct Answer)
- D. Buehler test
Explanation: ***Ames test*** - This test is a **mutagenicity assay** that assesses the ability of a chemical to cause mutations in DNA, primarily used to identify potential **carcinogens**. - While related to safety, it does not directly evaluate the **biocompatibility** (tissue response and interaction) of a material in a biological system. *Buehler test* - The Buehler test is a common method for assessing **sensitization potential** of a material, often used to evaluate whether a material causes an allergic contact dermatitis. - This is a direct measure of an adverse biological response and thus contributes to the overall assessment of **biocompatibility**. *Implantation test* - This test involves placing the material directly into an animal tissue (e.g., muscle, subcutaneous tissue) to evaluate the **local tissue response** over time. - It assesses aspects like **inflammation**, encapsulation, and tissue integration, which are primary indicators of a material's **biocompatibility**. *Sensitization test* - These tests, like the Buehler test mentioned, aim to identify if a material can induce an **allergic reaction** in a host. - Detecting such immune responses is crucial for determining if a material is safe for long-term contact with biological tissues, making it an essential part of **biocompatibility assessment**.
Question 8: Compression osteosynthesis may be used in all these areas except?
- A. Comminuted fractures of the mandible (Correct Answer)
- B. FZ suture (provides anatomical support)
- C. Bone graft fixation (promotes healing)
- D. Root of zygomatic arch (maintains structural integrity)
Explanation: ***Comminuted fractures of the mandible*** - **Compression osteosynthesis** is generally **contraindicated** in comminuted fractures because the application of compression can further **displace or fragment** the multiple bone pieces. - Such fractures often require **tension band plating** or **reconstruction plates** to stabilize the fragments without causing additional compression or displacement. *FZ suture (provides anatomical support)* - The **frontozygomatic (FZ) suture** is an area where compression osteosynthesis can be effectively used to achieve **stable fixation** and **anatomical reduction**. - Compression helps to **stabilize the bone segments** at the suture line, leading to better healing and restoration of orbital rim integrity. *Bone graft fixation (promotes healing)* - Compression osteosynthesis is often employed in **bone graft fixation** to promote **intimate contact** between the graft and the host bone, which is crucial for successful **graft incorporation and healing**. - This compression enhances **vascularization** and reduces movement, creating a more favorable environment for **osteogenesis**. *Root of zygomatic arch (maintains structural integrity)* - Compression osteosynthesis can be effectively used at the **root of the zygomatic arch** to maintain **structural integrity** and achieve stable fixation of fractures in this region. - Applying compression helps to **reduce fracture gaps** and provides stability, which is essential for restoring the contour and function of the midface.
Question 9: What is application of Plaster of Paris all around the surface called ?
- A. Slab
- B. Cast (Correct Answer)
- C. Spica
- D. None of the options
Explanation: ***Cast*** - A **cast** is a rigid dressing made from plaster of Paris or fiberglass that completely encircles a limb or body part. - Its primary application is to provide **immobilization** and support for fractures, dislocations, or other injuries, allowing for proper healing. *Slab* - A **slab** is an incomplete wrap, typically providing support on one side of a limb, acting more like a splint. - Unlike a cast, it does not completely encircle the limb and may be less restrictive to allow for swelling. *Spica* - A **spica** cast is a specific type of cast that includes the trunk and one or more extremities, often used for hip or shoulder immobilization. - While it uses plaster of Paris and involves complete coverage of specific areas, it's a specialized type of cast, not the general term for all-around application. *None of the options* - This option is incorrect because **cast** accurately describes the application of plaster of Paris all around the surface.
Question 10: When using low-flow circle absorber techniques, the uptake of nitrous oxide must be considered. In a healthy 70 kg adult, the expected uptake of nitrous oxide, with a 70% inspired concentration, after 1.5 hours would be about
- A. 500 ml/min
- B. 250 ml/min
- C. 1000 ml/min
- D. 100 ml/min (Correct Answer)
Explanation: ***100 ml/min*** - The uptake of **nitrous oxide (N2O)** decreases significantly over time as the blood and tissue compartments become saturated. After 1.5 hours, the uptake slows considerably. - At this point, the uptake rate for a 70 kg adult with 70% N2O is expected to be approximately **100 ml/min**, reflecting the near-saturation of less vascular tissues. *500 ml/min* - An uptake of **500 ml/min** is typical during the **initial, rapid uptake phase** of nitrous oxide (first 5-15 minutes) as it quickly equilibrates with the blood and highly perfused tissues. - This rate would be too high after 1.5 hours, as the body's capacity to absorb N2O has decreased significantly. *250 ml/min* - This rate represents an **intermediate phase** of N2O uptake, typically occurring within the first 30-60 minutes, when the drug is still being absorbed into moderately perfused tissues. - After 1.5 hours, the uptake would have slowed down further than this rate due to continued saturation of tissue compartments. *1000 ml/min* - An uptake of **1000 ml/min** (or 1 L/min) is an **extremely high rate** of N2O uptake, far exceeding what is physiologically possible in a 70 kg adult even during the initial rapid phase. - This would imply a massive, unsustainable absorption, which is not clinically relevant for N2O in a healthy individual.
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