Tissue Engineering in Orthopaedics — MCQs
Which of the following is the POOREST recipient bed for a skin graft?
Which type of collagen is most abundant in hyaline cartilage?
All of the following factors affect osseointegration EXCEPT:
Functional matrix theory suggests that the primary determinants of growth of skeletal tissues reside in:
Which of the following has the greatest concentration of osteogenic cells?
During reconstruction of an amputated limb which of the following is done first?
Primary osteoarthritis affects all except:
Which of the following is the commonest material used to make an orthopedic implant?
Healing of bone is affected by:
In articular cartilage, most active chondrocytes are seen in ?
Tissue Engineering in Orthopaedics Indian Medical PG Practice Questions and MCQs
Question 1: 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 2: Which type of collagen is most abundant in hyaline cartilage?
- A. Type I
- B. Type II (Correct Answer)
- C. Type III
- D. Type IV
Explanation: ***Type II*** - **Type II collagen** is the predominant type found in **hyaline cartilage**, providing tensile strength and elasticity [1]. - It is crucial for the **structural integrity** and functionality of cartilage in articular surfaces [1]. *Type I* - Predominantly found in **bone**, tendons, and skin, contributing to tensile strength but not a major component of hyaline cartilage [2]. - It forms the structure of **fibrocartilage**, such as in the **intervertebral discs**. *Type IV* - Mainly located in **basement membranes** and plays a role in filtration and structural support of epithelial cells, not in hyaline cartilage. - It is critical in the formation of structures like **glomeruli** in kidneys, differing from cartilage's needs. *Type III* - Found in **reticular fibers** and supporting tissues throughout the body, important for organ structure but not prominent in hyaline cartilage. - Often associated with **vascular structures** and is not involved in the composition of cartilage.
Question 3: 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 4: Functional matrix theory suggests that the primary determinants of growth of skeletal tissues reside in:
- A. Cartilages
- B. Sutures
- C. Skeletal
- D. Non-skeletal tissues (Correct Answer)
Explanation: ***Non-skeletal tissues*** - The **functional matrix theory** posits that the growth and development of skeletal tissues, particularly in the craniofacial region, are primarily determined by the surrounding soft tissues and their functions. [1] - These **non-skeletal tissues**, such as muscles, nerves, blood vessels, and fat, exert forces and provide stimuli that dictate the growth and remodeling of adjacent bones. *Cartilages* - While **cartilage** (e.g., condylar cartilage of the mandible) is a significant growth center, the functional matrix theory suggests its growth is still influenced by surrounding functional demands, not solely intrinsic factors. - Cartilage growth alone does not entirely explain the comprehensive craniofacial growth patterns according to this theory. *Sutures* - **Sutures** are important growth sites in the cranium and maxilla, contributing to bone apposition and separation. [1] - However, the functional matrix theory views sutural growth as a secondary event, responding to the expansive forces generated by the growth of underlying soft tissues and functional spaces. *Skeletal* - The functional matrix theory explicitly argues against the idea that **skeletal tissues** themselves (bones and cartilage) are the primary determinants of their own growth. - Instead, it emphasizes that skeletal growth is adaptive and reactive to the influences of the associated non-skeletal tissues and their functions.
Question 5: Which of the following has the greatest concentration of osteogenic cells?
- A. Marrow- cancellous graft. (Correct Answer)
- B. Marrow- cortical graft.
- C. Costochondral graft.
- D. Cortical graft
Explanation: ***Marrow- cancellous graft*** - **Cancellous bone** contains a high concentration of **bone marrow**, which is rich in **osteogenic stem cells** and growth factors essential for bone formation. - These cells contribute significantly to **osteogenesis**, making cancellous grafts potent for bone healing and fusion. *Marrow- cortical graft* - While cortical grafts provide structural support, the **bone marrow** within them is less abundant and less readily accessible compared to cancellous grafts. - The primary contribution of a cortical graft with marrow is **mechanical strength**, with less emphasis on osteogenic cell concentration. *Costochondral graft* - A costochondral graft includes both **cartilage** and bone, making it useful for specific reconstructions, such as mandibular condyle regeneration. - However, its primary osteogenic potential comes from the osseous component, which typically has a lower concentration of osteogenic cells compared to a cancellous bone graft. *Cortical graft* - **Cortical bone** is dense and provides significant **structural support**, but it contains very few **osteogenic cells** and has limited intrinsic capacity for new bone formation. - Its main roles are providing **load-bearing strength** and acting as a scaffold, rather than contributing a high concentration of osteogenic cells.
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: Primary osteoarthritis affects all except:
- A. Metacarpophalangeal joint (Correct Answer)
- B. Hip Joint
- C. Distal interphalangeal joint
- D. Knee joint
Explanation: ***Metacarpophalangeal joint*** - The **metacarpophalangeal (MCP) joints** are typically spared in primary osteoarthritis, making their involvement a less common presentation. - Involvement of the MCP joints, particularly with significant inflammation, might suggest other conditions like **rheumatoid arthritis**. *Hip Joint* - The hip joint is a common site for primary osteoarthritis due to its **weight-bearing function** and susceptibility to mechanical stress. - Patients often experience **groin pain** and reduced range of motion, particularly internal rotation. *Distal interphalangeal joint* - The **distal interphalangeal (DIP) joints** are very commonly affected in primary osteoarthritis, leading to the formation of **Heberden's nodes**. - These nodes are bony enlargements that indicate osteophyte formation and cartilage loss. *Knee joint* - The knee joint is another frequently affected large joint in primary osteoarthritis, often presenting with **pain**, **stiffness**, and **crepitus**. - Its **weight-bearing role** contributes significantly to its vulnerability to degenerative changes.
Question 8: Which of the following is the commonest material used to make an orthopedic implant?
- A. Methyl-methacrylate
- B. Polyethylene (UHMWPE)
- C. Titanium (Correct Answer)
- D. Stainless steel
Explanation: ***Titanium*** - **Titanium** and its alloys (e.g., Ti-6Al-4V) are widely favored for orthopedic implants due to their **excellent biocompatibility**, high strength-to-weight ratio, and corrosion resistance. - Its **osseointegrative properties** allow bone to grow directly onto the implant surface, providing stable fixation without an intervening fibrous layer. *Methyl-methacrylate* - **Methyl-methacrylate** is primarily used as a **bone cement** (PMMA) to fix implants to bone, rather than as the primary material for the implant itself. - It provides immediate mechanical stability but does not integrate with bone. *Polyethylene (UHMWPE)* - **Ultra-high molecular weight polyethylene (UHMWPE)** is commonly used as a bearing surface in joint replacements (e.g., acetabular liner in hip replacements) for its **low friction** and good wear resistance. - It is not typically used for the structural components of the implant that bear the primary load. *Stainless steel* - **Stainless steel** (e.g., 316L) was historically a common implant material, particularly for temporary fixation devices like plates and screws. - While it has good strength and corrosion resistance, it generally has a **lower biocompatibility** and more elastic modulus mismatch with bone compared to titanium, making it less preferred for permanent, load-bearing implants.
Question 9: 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 10: In articular cartilage, most active chondrocytes are seen in ?
- A. Zone 1
- B. Zone 4
- C. Zone 2 (Correct Answer)
- D. Zone 3
Explanation: ***Zone 2*** - The **transitional zone (Zone 2)** contains chondrocytes that are more metabolically active and contribute significantly to **collagen and proteoglycan synthesis**. [1] - These chondrocytes are typically **larger and more rounded** than those in the superficial layer and are organized in columns. *Zone 1* - **Zone 1 (superficial or tangential zone)** consists of **flattened chondrocytes** that are metabolically less active. - Its primary role is to resist **shear forces** and reduce friction. [1] *Zone 4* - **Zone 4 (calcified zone)** is the deepest layer of articular cartilage, characterized by **chondrocytes embedded in a calcified matrix**. - This zone anchors the cartilage to the subchondral bone and has **minimal metabolic activity**. *Zone 3* - **Zone 3 (deep or radial zone)** has chondrocytes arranged in **columns perpendicular to the articular surface**. [1] - While active in matrix production, their activity is generally **less pronounced** compared to the transitional zone.
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