Vascularized Bone Grafts — MCQs
The ideal synthetic material used for femoropopliteal bypass when autologous vein is unavailable is:
All of the following factors affect osseointegration EXCEPT:
Which statement is true regarding secondary contraction of skin grafts?
Meyer pedicle graft is used for?
Which artery is primarily responsible for supplying the head and neck of the femur?
During reconstruction of an amputated limb which of the following is done first?
In hand injury, the first structure to be repaired should be?
Following are the common sites of Avascular necrosis, EXCEPT:
Pediatric patient with an upper humerus lytic lesion and cortical thinning, which among the following is not a treatment modality?
Which of the following is the POOREST recipient bed for a skin graft?
Vascularized Bone Grafts Indian Medical PG Practice Questions and MCQs
Question 1: 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 2: 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 3: Which statement is true regarding secondary contraction of skin grafts?
- A. Thicker grafts are associated with more primary contracture.
- B. Thinner grafts are associated with more primary contracture.
- C. Thicker grafts are associated with both primary and secondary contracture.
- D. Thinner grafts are associated with more secondary contracture. (Correct Answer)
Explanation: ***Thinner grafts are associated with more secondary contracture.*** - **Secondary contracture** occurs days to weeks after grafting as the wound heals and is caused by **myofibroblasts** in the wound bed. - **Thinner grafts** (e.g., split-thickness grafts) contain less dermis, which means fewer **fibroblasts** and less **collagen** that would inhibit wound contraction. - This results in a greater degree of secondary contracture compared to thicker grafts. - The lack of dermal elements allows myofibroblasts to contract the wound more freely. *Thicker grafts are associated with more primary contracture.* - This statement addresses **primary contracture**, not secondary contracture. - Primary contracture occurs immediately upon graft harvesting due to elastic recoil of dermal collagen and elastin fibers. - While true for primary contracture, it does not answer the question about secondary contracture. *Thinner grafts are associated with more primary contracture.* - This is **incorrect** - thinner grafts have **less** primary contracture because they contain less dermal tissue and fewer elastic fibers. - Primary contracture is more pronounced in thicker grafts due to their higher content of elastic tissue. *Thicker grafts are associated with both primary and secondary contracture.* - While thicker grafts do experience more **primary contracture**, they are associated with **less secondary contracture** (not more). - The presence of more dermal tissue in thicker grafts helps stabilize the wound and resist contraction by myofibroblasts during the healing phase.
Question 4: Meyer pedicle graft is used for?
- A. Fracture through the waist of the scaphoid
- B. Non-union fracture neck of femur (Correct Answer)
- C. Inter-trochanteric fracture femur
- D. Fracture through neck of the talus
Explanation: ***Non-union fracture neck of femur*** - The **Meyer pedicle graft** is a vascularized bone graft technique specifically designed to address **non-union** in the **femoral neck**, where blood supply is crucial for healing. - It involves transferring a pedicle graft, often from the **quadratus femoris muscle**, including its vascular supply, to the femoral neck to promote bone healing. *Fracture through the waist of the scaphoid* - While scaphoid fractures can suffer from non-union due to precarious blood supply, the **Meyer pedicle graft** is not typically the primary or most common surgical technique used; other vascularized grafts like the **1,2 intercompartmental supraretinacular artery (1,2-ICSRA) graft** are more common. - Treatment often involves **screws** or **other specialized vascularized bone grafts**, not the Meyer graft, which is specific to the hip. *Inter-trochanteric fracture femur* - **Inter-trochanteric fractures** generally heal well due to their **rich blood supply** and are typically managed with internal fixation like a **dynamic hip screw (DHS)** or an **intramedullary nail**. - **Non-union** is rare in these fractures, so a vascularized pedicle graft like the Meyer graft is not indicated. *Fracture through neck of the talus* - Talus neck fractures have a risk of **avascular necrosis (AVN)** due to compromised blood supply, but the **Meyer pedicle graft** is not used for this location. - Treatment usually involves **open reduction and internal fixation (ORIF)**, and in cases of AVN, other specialized reconstructive procedures or fusions may be considered.
Question 5: Which artery is primarily responsible for supplying the head and neck of the femur?
- A. Medial circumflex artery (Correct Answer)
- B. Obturator artery
- C. Lateral circumflex artery
- D. Profunda femoris artery
Explanation: ***Medial circumflex artery*** - The **medial circumflex artery** is the primary blood supply to the **femoral head and neck** in adults. - Its branches, particularly the **retinacular arteries**, ascend along the femoral neck to perfuse the head. *Lateral circumflex artery* - The **lateral circumflex artery** supplies the **vastus lateralis muscle** and contributes to the supply of the **greater trochanter**. - While it anastomoses with the medial circumflex artery, its direct contribution to the femoral head is minimal. *Profunda femoris artery* - The **profunda femoris artery**, or deep femoral artery, is the main arterial supply to the **thigh muscles**. - It gives rise to the medial and lateral circumflex femoral arteries but does not directly supply the femoral head. *Obturator artery* - The **obturator artery** primarily supplies the **adductor muscles** of the thigh and contributes branches to the hip joint capsule. - While it has a small branch (artery to the head of the femur) that may contribute to the femoral head in children, it is not the main source in adults.
Question 6: During reconstruction of an amputated limb which of the following is done first?
- A. Arterial repair
- B. Venous repair
- C. Fixation of the bone (Correct Answer)
- D. Nerve anastomoses
Explanation: ***Fixation of the bone*** - **Bone stabilization** is the crucial first step to create a rigid framework, allowing for subsequent precise vascular and nerve repairs. - This prevents movement and tension on delicate repairs, which could lead to failure of the reconnected vessels and nerves. *Arterial repair* - While critical for blood supply, arterial repair is performed *after* bone fixation to ensure the vessels are not disrupted by later bone manipulation. - It's typically done before venous repair to establish arterial flow and identify any potential venous back pressure that needs addressing. *Venous repair* - Venous repair is usually performed after arterial repair, as establishing arterial inflow can help distend the veins, making them easier to identify and repair. - Repairing veins first without establishing arterial flow immediately is less effective and may lead to congestion once arterial flow is restored. *Nerve anastomoses* - Nerve repair is typically the last major step in an amputation reconstruction, following bone stabilization and full vascular repair. - Nerves are fragile and require a stable, well-perfused environment to optimize the chances of successful regeneration.
Question 7: In hand injury, the first structure to be repaired should be?
- A. Skin
- B. Muscle
- C. Nerve
- D. Bone (Correct Answer)
Explanation: ***Bone*** - In hand injury, **skeletal stability** is paramount and is typically the first structure to be addressed to provide a stable foundation. - Repairing bone first allows for proper alignment and length restoration, which is crucial for the subsequent repair of soft tissues like tendons, nerves, and vessels. *Skin* - While skin closure is the final step in wound management, it should only be performed after deeper structures like bone, tendons, and nerves have been repaired. - Repairing the skin first would prevent access to underlying damaged structures and could lead to functional impairment. *Muscle* - Muscle repair is important for restoring function but should follow bone stabilization to ensure proper length and tension. - Unstable bone fragments can impede effective muscle repair and healing. *Nerve* - Nerve repair is critical for restoring sensation and motor function and should be done with meticulous attention to detail. - However, nerve repair typically follows bone stabilization and sometimes tendon repair, as a stable environment is necessary for successful nerve coaptation and healing.
Question 8: Following are the common sites of Avascular necrosis, EXCEPT:
- A. Head of the femur
- B. The body of talus
- C. Patella (Correct Answer)
- D. Proximal half of scaphoid
Explanation: ***Patella*** - The patella is rarely affected by **avascular necrosis (AVN)** due to its robust and redundant blood supply, making it an exception to common AVN sites. - While patellar fractures can compromise local blood flow, spontaneous or atraumatic AVN of the patella is exceedingly uncommon compared to other skeletal sites. *Head of the femur* - The **femoral head** is the most common site for **avascular necrosis** due to its precarious blood supply, especially after trauma (e.g., hip dislocation, femoral neck fracture) or in systemic conditions. - Its blood supply relies heavily on the **medial circumflex femoral artery**, which can be easily disrupted. *The body of talus* - The **talus** is highly susceptible to **avascular necrosis**, particularly after fractures or dislocations, as its blood supply enters through a limited number of soft tissue attachments. - The **body of the talus** receives a significant portion of its blood supply from vessels that can be easily compromised by injury. *Proximal half of scaphoid* - The **proximal pole of the scaphoid** is notoriously prone to **avascular necrosis** following scaphoid fractures because its blood supply enters primarily from the distal pole. - A disruption of blood flow (e.g., via the **dorsal carpal branch** of the radial artery) due to a fracture can lead to **non-union** and AVN of the proximal fragment.
Question 9: Pediatric patient with an upper humerus lytic lesion and cortical thinning, which among the following is not a treatment modality?
- A. Curettage and bone grafting
- B. Steroids
- C. Sclerosant (Correct Answer)
- D. Radiotherapy
Explanation: ***Sclerosant*** - While sclerosants can be used in some vascular lesions or cysts, they are **not a standard or primary treatment modality for an upper humerus lytic lesion** with cortical thinning, which often represents a bone cyst or benign tumor. - Their mechanism of action involves **inducing fibrosis and closing off vascular structures**, which isn't the main goal for common lytic bone lesions in children. *Curettage and bone grafting* - This is a very common and effective treatment for **benign lytic bone lesions** like **unicameral bone cysts (UBCs)** or aneurysmal bone cysts (ABCs). - **Curettage** removes the diseased tissue, and **bone grafting** (autograft or allograft) fills the defect, promoting healing and stability. *Steroids* - **Intralesional steroid injection** is a recognized treatment for **unicameral bone cysts (UBCs)**, especially in actively growing lesions in children. - Steroids help **reduce inflammation and promote resolution** of the cyst lining, often leading to bone healing. *Radiotherapy* - While radiotherapy is used for malignant bone tumors, it is **generally avoided for benign lytic lesions in children** due to concerns about long-term risks like growth disturbance and secondary malignancy. - It might be considered in **recalcitrant or aggressive benign lesions** where other treatments have failed, but it is not a first-line treatment.
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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