Autografts: Harvesting and Applications — MCQs
The graft with the maximum osteogenic potential is:
Which of the following is the POOREST recipient bed for a skin graft?
During reconstruction of an amputated limb which of the following is done first?
What is the most common complication after total hip replacement?
Healing of bone is affected by:
The best material for below-inguinal arterial graft is:
Graft used from an identical twin is called as?
What is the preferred site for a first-order bone graft?
Which site is the most common source for autologous bone grafts?
Clamshell technique is required for which type of bone graft?
Autografts: Harvesting and Applications 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: 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 3: 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 4: What is the most common complication after total hip replacement?
- A. Dislocation
- B. DVT (Correct Answer)
- C. Infection
- D. Aseptic Loosening
Explanation: ***DVT*** - Deep vein thrombosis (DVT) is the **most common overall complication** following total hip replacement, with reported incidences as high as 40-60% without prophylaxis. - The risk of DVT is significant due to **venous stasis during surgery**, immobilization, and the inflammatory response to tissue injury. *Dislocation* - While a serious complication, **dislocation** of the prosthetic hip joint is less common than DVT, occurring in about 1-5% of primary total hip replacements. - It typically results from **improper joint positioning** or patient activities that push the hip beyond its normal range of motion. *Infection* - **Infection** is a severe but relatively rare complication, with rates for periprosthetic joint infection in total hip replacement typically ranging from 0.5% to 2%. - It can lead to significant morbidity and usually requires **further surgical intervention** for eradication. *Aseptic Loosening* - **Aseptic loosening** is a long-term complication, occurring years after the surgery, rather than an immediate post-operative complication. - This complication involves the **failure of the implant-bone interface** without evidence of infection, often due to particle disease or mechanical stress.
Question 5: Healing of bone is affected by:
- A. Hypoxia
- B. Micromovement
- C. Muscle interposition
- D. All of the options (Correct Answer)
Explanation: ***All of the options*** - **Hypoxia**, **micromovement**, and **muscle interposition** are all factors known to impede or negatively affect the normal healing process of a bone fracture. - The successful healing of a bone fracture relies on a series of biological events that can be disrupted by these adverse conditions, leading to delayed union or non-union. *Hypoxia* - **Hypoxia**, or insufficient oxygen supply, impairs the metabolic activity of cells essential for bone healing, such as osteoblasts and chondrocytes. - It interferes with **angiogenesis**, the formation of new blood vessels, which is critical for delivering nutrients and oxygen to the healing bone. *Micromovement* - Excessive **micromovement** at the fracture site prevents the formation of a stable callus and can stimulate the development of fibrous tissue or cartilage instead of bone. - While some motion is beneficial, uncontrolled or excessive micromotion can lead to a **non-union** or pseudarthrosis, as it constantly disrupts the delicate tissue bridges attempting to form. *Muscle interposition* - **Muscle interposition** refers to muscle tissue becoming trapped between the bone fragments, physically separating them and preventing direct bone-to-bone contact. - This physical barrier inhibits the formation of the **fracture hematoma** and subsequent callus, thus mechanically hindering the healing process.
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: Graft used from an identical twin is called as?
- A. Allograft
- B. Isograft (Correct Answer)
- C. Autograft
- D. Xenograft
Explanation: ***Isograft*** - An **isograft**, also known as a **syngeneic graft**, involves tissue transfer between **genetically identical** individuals, such as monozygotic (identical) twins. - Due to identical genetic makeup, there is **minimal to no immune rejection**, making it the most successful type of transplant. *Allograft* - An **allograft** involves tissue transfer between **genetically non-identical individuals** of the **same species**. - While common, allografts carry a significant risk of **immune rejection** and require **immunosuppressive therapy**. *Autograft* - An **autograft** is a transplant where tissue is taken from **one part of the patient's own body** and transferred to another part. - Since the tissue is from the same individual, there is **no risk of immune rejection**. *Xenograft* - A **xenograft** involves tissue transfer between **different species**, such as from a pig to a human. - Xenografts face the **highest risk of hyperacute immune rejection** due to significant genetic differences.
Question 8: What is the preferred site for a first-order bone graft?
- A. Pelvis (Correct Answer)
- B. Tibial metaphysis
- C. Medial malleolus
- D. Femoral condyle
Explanation: The **Pelvis (specifically the Iliac Crest)** is the gold standard and preferred site for a first-order bone graft because it provides the highest concentration of **cancellous bone**. Cancellous bone is superior for grafting because it is highly vascularized and contains a large population of osteoblasts and mesenchymal stem cells, facilitating rapid **osteogenesis, osteoconduction, and osteoinduction**. ### Evaluation of Options: * **A. Pelvis (Correct):** The iliac crest (anterior or posterior) is the most common site for autologous bone grafting. It offers a large volume of high-quality marrow and trabecular bone with minimal structural morbidity. * **B. Tibial metaphysis:** While used for smaller grafts (e.g., in foot and ankle surgery), it provides a significantly lower volume of cancellous bone compared to the pelvis. * **C. Medial malleolus:** This is a site for very small, localized bone grafts. It lacks the volume and cellular density required for major reconstructive procedures. * **D. Femoral condyle:** Though it contains cancellous bone, the surgical morbidity of entering a major weight-bearing joint makes it a secondary choice compared to the iliac crest. ### High-Yield Clinical Pearls for NEET-PG: * **Gold Standard:** Autologous bone graft (Autograft) remains the gold standard because it possesses all three properties: **Osteogenesis** (living cells), **Osteoinduction** (growth factors like BMP), and **Osteoconduction** (scaffold). * **Posterior vs. Anterior Iliac Crest:** The posterior iliac crest yields a higher volume of bone graft than the anterior crest. * **Cortical vs. Cancellous:** Cortical grafts (e.g., Fibula) provide immediate **structural support** but have poor osteogenic potential. Cancellous grafts (e.g., Pelvis) provide **rapid revascularization** and healing but no structural strength. * **Creeping Substitution:** The process by which the host replaces the grafted bone with new living bone.
Question 9: Which site is the most common source for autologous bone grafts?
- A. Iliac crest (Correct Answer)
- B. Tibial tuberosity
- C. Greater trochanter
- D. Fibula
Explanation: **Explanation:** The **Iliac Crest** is the "gold standard" and most common donor site for autologous bone grafting. This is because it provides a rich supply of both **corticocancellous bone** and osteoprogenitor cells. The posterior iliac crest is preferred when a large volume of bone is needed, while the anterior crest is used for smaller grafts due to easier surgical access. **Why the other options are incorrect:** * **Tibial tuberosity:** While it can be used for small amounts of cancellous bone (e.g., in foot and ankle surgeries), the volume available is significantly less than the ilium, and there is a risk of weakening the extensor mechanism. * **Greater trochanter:** This site provides a limited amount of cancellous bone. It is rarely the primary choice unless the surgery is already being performed in the hip region. * **Fibula:** The fibula is the most common source for **vascularized cortical bone grafts**. It is used for structural support (e.g., bridging large bony defects) rather than as a general source of cancellous bone. **High-Yield Clinical Pearls for NEET-PG:** * **Osteogenesis, Osteoinduction, and Osteoconduction:** Autografts are unique because they possess all three properties. * **Complications:** The most common complication of iliac crest harvesting is **chronic donor site pain**. Injury to the lateral femoral cutaneous nerve (Meralgia paresthetica) can occur during anterior harvesting. * **Bone Morphogenetic Proteins (BMPs):** These are the most potent osteoinductive growth factors found within the bone matrix.
Question 10: Clamshell technique is required for which type of bone graft?
- A. Ilio-cortical graft
- B. Ilio-cancellous graft (Correct Answer)
- C. Posterior iliac graft
- D. Anterior iliac graft
Explanation: **Explanation:** The **Clamshell technique** (also known as the Trapdoor or Tessier technique) is a specific surgical approach used to harvest large amounts of **ilio-cancellous bone graft** from the iliac crest while preserving the overall shape and structural integrity of the pelvis. **1. Why the Correct Answer is Right:** In this technique, the iliac crest is split longitudinally along its superior border. The inner and outer tables of the ilium are then pried apart like a "clamshell" or "trapdoor." This provides direct access to the rich **cancellous bone** (medulla) located between the cortical plates. After the cancellous bone is scooped out, the cortical plates are repositioned and sutured back together. This minimizes donor site morbidity and maintains the aesthetic contour of the hip. **2. Why Other Options are Wrong:** * **Ilio-cortical graft:** These grafts involve taking the full thickness of the bone (cortex). The clamshell technique specifically aims to *spare* the cortex while harvesting the marrow. * **Posterior/Anterior iliac graft:** These refer to the *anatomical site* of harvest rather than the *technique* used to extract the bone. While the clamshell technique can be performed on either the anterior or posterior crest, it specifically describes the method of accessing cancellous bone, not the location. **3. High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard:** Autologous cancellous bone graft is the gold standard for promoting osteogenesis, osteoinduction, and osteoconduction. * **Donor Site:** The **Posterior Iliac Crest** is the richest source of cancellous bone in the body (provides more volume than the anterior crest). * **Complication:** The most common complication of iliac crest harvest is **chronic donor site pain** and injury to the **lateral femoral cutaneous nerve** (in anterior approaches). * **Creeping Substitution:** This is the process by which the host bone replaces the graft with new bone.
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