Bone Graft Substitutes — MCQs

10 questions

Which of the following statements are correct about Kiel bone? 1. Xenograft 2. Allograft 3. Treated by detergent, sterilized, and freeze-dried 4. Ox or calf bone denatured with 20% H2O2, acetone, and sterilized

Which of the following structures is fixed first during reimplantation of an amputated digit -

The ideal synthetic material used for femoropopliteal bypass when autologous vein is unavailable is:

All of the following factors affect osseointegration EXCEPT:

What is the primary organic component of bone?

Technetium-99m methylene diphosphonate is structurally similar to

Compression osteosynthesis may be used in all these areas except?

All are true about aneurysmal bone cyst except -

The operative procedure known as "microfracture" is done for the

Q10

Which of the following is the POOREST recipient bed for a skin graft?

Bone Graft Substitutes Indian Medical PG Practice Questions and MCQs

Question 1: Which of the following statements are correct about Kiel bone? 1. Xenograft 2. Allograft 3. Treated by detergent, sterilized, and freeze-dried 4. Ox or calf bone denatured with 20% H2O2, acetone, and sterilized

A. 2 & 4
B. 2 & 3
C. 1 & 3
D. 1 & 4 (Correct Answer)

Explanation: ***1 & 4*** - **Kiel bone** is a type of **xenograft**, meaning it is derived from a different species (usually ox or calf). - It is prepared by **denaturing** ox or calf bone with 20% H2O2 and acetone, followed by sterilization, to reduce antigenicity and ensure safety. *2 & 4* - This option incorrectly states that Kiel bone is an **allograft**, while it is, in fact, a **xenograft**. - The preparation method of denaturing with 20% H2O2 and acetone, and sterilization, correctly describes Kiel bone processing. *2 & 3* - This option incorrectly identifies Kiel bone as an **allograft** and states that it is treated by detergent, sterilized, and freeze-dried. - While some bone grafts are treated this way, it is not the specific processing for Kiel bone, which uses H2O2 and acetone. *1 & 3* - This option correctly identifies Kiel bone as a **xenograft**, but incorrectly states its processing involves detergent, sterilization, and freeze-drying. - The distinguishing feature of Kiel bone preparation is the use of **H2O2 and acetone** for denaturing.

Question 2: Which of the following structures is fixed first during reimplantation of an amputated digit -

A. Bone (Correct Answer)
B. Vein
C. Nerve
D. Artery

Explanation: ***Bone*** - **Bone fixation** is the crucial first step to stabilize the digit, providing a stable framework for subsequent soft tissue repair. - This **restores skeletal integrity** and allows for proper alignment, reducing tension on delicate vascular and nervous structures. *Vein* - **Vein repair** is typically performed after arterial repair to ensure adequate outflow and prevent congestion, but after bone fixation. - While critical for successful reimplantation, venous repair without prior bone stability is difficult and prone to compromise. *Nerve* - **Nerve repair** is generally performed later in the sequence, after bone and vascular repairs have been completed. - The focus is on restoring blood flow first to ensure tissue viability before addressing nerve continuity for sensation and motor function. *Artery* - **Arterial reconstruction** is paramount for revascularization and tissue viability, but it follows initial bone stabilization. - Attempting to connect arteries without a stable skeletal foundation would make the repair challenging and increase the risk of avulsion or damage.

Question 3: 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 4: 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.

Question 5: What is the primary organic component of bone?

A. 10% collagen
B. 10% noncollagenous protein
C. 20% noncollagenous protein
D. 90% collagen protein (Correct Answer)

Explanation: ***90% collagen protein*** - **Type I collagen** constitutes around 90% of the organic matrix of bone, providing its tensile strength and flexibility [1]. - This extensive collagen network forms the framework upon which **mineral crystals** (hydroxyapatite) are deposited [1]. *10% collagen* - This percentage is significantly lower than the actual proportion of collagen in the organic matrix of bone. - If collagen only represented 10%, bone would lack its characteristic **tensile strength** and elasticity [2]. *10% noncollagenous protein* - While noncollagenous proteins like **osteocalcin** and **osteonectin** are important for bone mineralization and cell signaling, they only constitute about 10% of the *organic matrix*, not the entire bone, and are not the *primary organic component* [1]. - The dominant organic component is collagen, which provides the structural scaffold [1]. *20% noncollagenous protein* - This percentage is inaccurate; **noncollagenous proteins** typically make up about 10% of the bone's organic matrix [1]. - A higher proportion of noncollagenous proteins would alter the bone's mechanical properties, potentially making it more brittle.

Question 6: Technetium-99m methylene diphosphonate is structurally similar to

A. Sodium bicarbonate
B. Phosphorus
C. Calcium phosphate (Correct Answer)
D. Magnesium sulfate

Explanation: ***Calcium phosphate*** - **Technetium-99m methylene diphosphonate (Tc-99m MDP)** is used in bone scans because it structurally mimics **calcium phosphate**, the primary mineral component of bone. - This structural similarity allows Tc-99m MDP to be incorporated into the **hydroxyapatite crystals** present in bone, making it an effective tracer for skeletal imaging. *Sodium bicarbonate* - **Sodium bicarbonate** is a basic salt with a different chemical structure, primarily involved in maintaining pH balance in the body, not bone matrix. - It does not contain phosphate groups or the specific molecular configuration needed to bind to **hydroxyapatite crystals**. *Phosphorus* - While **phosphorus** is a component of calcium phosphate, free phosphorus (as an element) is not structurally similar to Tc-99m MDP. - Tc-99m MDP is a diphosphonate, a complex molecule where the phosphonate groups are critical for bone binding, not just elemental phosphorus. *Magnesium sulfate* - **Magnesium sulfate** is an inorganic salt used for various medical purposes, but it does not have the diphosphonate structure or the affinity for bone mineralization sites that Tc-99m MDP possesses. - Its chemical structure is fundamentally different from that of bone matrix components, preventing its use as a bone imaging agent.

Question 7: 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 8: All are true about aneurysmal bone cyst except -

A. Eccentric
B. Expansile & lytic
C. Treated by simple curettage (Correct Answer)
D. Metaphysis of long bones

Explanation: ***Treated by simple curettage*** - Aneurysmal bone cysts (ABCs) often require more aggressive treatment than simple curettage due to their **high recurrence rate** and the risk of incomplete removal. - **Sclerotherapy**, **embolization**, or **en bloc resection** may be necessary, especially for larger or recurrent lesions, as simple curettage alone is often insufficient. *Eccentric* - Aneurysmal bone cysts are indeed **eccentric lesions**, meaning they are located off-center within the bone. - This eccentric location is a characteristic feature often observed on **radiological imaging**. *Expansile & lytic* - ABCs are typically **expansile** (causing bone expansion) and **lytic** (destructive to bone tissue) lesions. - This combination of features contributes to the characteristic **"blow-out" appearance** on imaging. *Metaphysis of long bones* - The **metaphysis of long bones** is a common site for aneurysmal bone cysts, particularly in younger individuals. - Other frequently affected sites include the **spine** and **flat bones**.

Question 9: The operative procedure known as "microfracture" is done for the

A. Delayed union of femur
B. Osteochondral defect of femur (Correct Answer)
C. Non union of tibia
D. Loose bodies of ankle joint

Explanation: ***Osteochondral defect of femur*** - **Microfracture** is a surgical technique used to stimulate the growth of **fibrocartilage** in areas of damaged articular cartilage, such as an **osteochondral defect**. - It involves creating small holes in the **subchondral bone** to allow stem cells and growth factors from the bone marrow to form a new reparative tissue. *Delayed union of femur* - **Delayed union** typically involves an extended time for fracture healing, which is often managed through prolonged immobilization, **bone grafting**, or sometimes revision surgery. - Microfracture specifically targets cartilage repair, not the process of **bony union** after a fracture. *Non union of tibia* - **Non-union** refers to the failure of a fractured bone to heal within a reasonable timeframe, often requiring surgical intervention with **bone grafts** or **internal fixation**. - This condition involves bone healing problems, distinct from cartilage defects that microfracture addresses. *Loose bodies of ankle joint* - **Loose bodies** in a joint are typically removed surgically, often arthroscopically, to relieve pain and prevent joint damage. - This procedure does not involve the repair of cartilage defects, which is the primary goal of microfracture.

Question 10: 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.

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