Principles of Internal Fixation — MCQs
All of the following factors affect osseointegration EXCEPT:
Identify the implant shown in the image:
Which of the following is false regarding clavicle?
Healing by Haversian remodeling is a type of:
In hand injury, the first structure to be repaired should be?
What is the biomechanical principle involved in symphyseal fracture with lag screw fixation?
All of the following are indications for open reduction and internal fixation (ORIF) of fractures EXCEPT:
Following a road traffic accident, a patient develops type IIIa compound tibial fracture. Arrange the following external fixators in decreasing order of their stability (highest to lowest) 1. Ilizarov fixator 2. Uniplanar with a single rod 3. Uniplanar with double rod 4. Biplanar frame/Ring with a cylindrical rod
What is the best treatment for a 60-year-old man with intracapsular femoral neck fracture?
Which one of the following is the most ideal treatment for a displaced fracture of the lateral condyle of the humerus in a 7-year-old child?
Principles of Internal Fixation Indian Medical PG Practice Questions and MCQs
Question 1: 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 2: Identify the implant shown in the image:
- A. Dynamic hip screw (Correct Answer)
- B. Cannulated hip screw
- C. Condylar hip screw
- D. Intramedullary nail
Explanation: ***Dynamic hip screw*** - The image shows a **lag screw** inserted into the femoral neck and head, which slides within a **side plate** attached to the femoral shaft with cortical screws. - This construct allows for controlled **dynamic collapse** and impaction at the fracture site, promoting healing and providing stable fixation for **extracapsular hip fractures**. *Cannulated hip screw* - Cannulated screws are typically used in a **parallel configuration** or as a single large screw for hip fractures, particularly **femoral neck fractures**. - They do not feature a **side plate** that extends down the femoral shaft for additional fixation. *Condylar hip screw* - A condylar hip screw (DCS) is used for **distal femur fractures**, often extending into the **condyles**. - It involves a different angulation and design compared to the proximal femoral implant seen, which is fixed to the femoral shaft. *Intramedullary nail* - An intramedullary nail is inserted into the **medullary canal** of the bone, running through its center. - While some hip nails (e.g., trochanteric nails) have a cephalic screw component, they primarily stabilize the shaft from within, unlike the **extracortical side plate** seen here.
Question 3: Which of the following is false regarding clavicle?
- A. First bone to ossify
- B. Membranous ossification
- C. Fracture can be treated with figure of 8 bandage
- D. Non-union is the commonest complication of clavicle fractures (Correct Answer)
Explanation: ***Non-union is the commonest complication of clavicle fractures*** - While clavicle fractures are relatively common, **malunion** (healing in an imperfect position) is more frequent than non-union. - **Non-union** typically occurs in less than 5% of all clavicle fractures, making it a rare complication rather than the commonest. *First bone to ossify* - The clavicle is indeed the **first bone to ossify** in the human embryo, beginning around the 5th to 6th week of gestation. - This characteristic highlights its unique developmental pathway compared to most other bones. *Membranous ossification* - The clavicle develops primarily through **intramembranous ossification**, which involves direct ossification of mesenchymal tissue without a cartilaginous precursor. - It's one of the few bones in the body, along with some bones of the skull, that ossifies this way. *Fracture can be treated with figure of 8 bandage* - A **figure-of-eight bandage** was historically used for clavicle fractures to provide reduction and immobilization. - However, current evidence suggests that a **simple sling** is equally effective and often more comfortable, with less risk of complications like neurovascular compression.
Question 4: Healing by Haversian remodeling is a type of:
- A. Tertiary healing.
- B. Secondary healing.
- C. Primary healing. (Correct Answer)
- D. Intermediate healing.
Explanation: ***Primary healing*** - This term refers to **direct healing**, where bone fragments are in contact and movement is minimized, leading to direct bone formation without significant callus. - **Haversian remodeling**, common in rigid internal fixation, is the hallmark of primary bone healing, involving direct osteon formation across the fracture site. *Tertiary healing* - This is **not a recognized term** in the classification of bone healing processes. - Bone healing is generally categorized as primary (direct) or secondary (indirect). *Secondary healing* - This involves the formation of a **soft and then hard callus** in cases of unreduced or mobile fractures. - It is characterized by three overlapping phases: **inflammation, repair**, and **remodeling**, and does not primarily rely on Haversian remodeling. *Intermediate healing* - This is **not a formal classification** of bone healing. - Bone healing is typically dichotomized into primary and secondary healing, depending on the stability and reduction of the fracture.
Question 5: 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 6: What is the biomechanical principle involved in symphyseal fracture with lag screw fixation?
- A. Load bearing
- B. Load sharing (Correct Answer)
- C. Compression osteosynthesis
- D. Adaptation osteosynthesis
Explanation: **Load sharing** - Lag screw fixation allows for **interfragmentary compression** while still permitting some load to be borne by the surrounding bone and soft tissues, promoting a more physiological healing response. - This method provides a **stable environment** for bone healing by distributing forces across both the implant and the bone fragments. *Load bearing* - This principle implies that the **implant alone carries the majority of the load**, effectively shielding the fracture site from stress. - While a lag screw provides stability, it is not designed to be the sole load bearer; rather, it facilitates the bone's ability to bear load as it heals. *Compression osteosynthesis* - Although lag screws achieve compression, the term **compression osteosynthesis** is a broader concept that can include techniques like tension banding or plates, with the primary goal of creating stability through direct compression. - While **interfragmentary compression** is a part of lag screw fixation, "load sharing" more accurately describes the overall biomechanical outcome in symphyseal fractures where some physiological stress is beneficial for healing. *Adaptation osteosynthesis* - This refers to fixation designed primarily to **adapt or hold fragments in place** without providing significant compressive forces or the ability to share physiological loads directly with the bone during healing. - It’s typically used for non-weight-bearing fractures or where minimal stress is anticipated, which is not the case for symphyseal fractures.
Question 7: All of the following are indications for open reduction and internal fixation (ORIF) of fractures EXCEPT:
- A. Multiple trauma
- B. Stable closed fracture (Correct Answer)
- C. Compound fracture
- D. Intra-articular fracture
Explanation: ***Stable closed fracture*** - A **stable closed fracture** typically does not require surgical intervention with ORIF as it can usually be managed non-surgically with casting or bracing. - The goal of ORIF is to achieve **anatomic reduction and rigid fixation**, which is not necessary for stable fractures that maintain alignment. *Multiple trauma* - In patients with **multiple trauma**, early stabilization of long bone fractures using ORIF can help reduce pain, prevent further injury, and facilitate patient mobilization. - This approach aims to reduce the risk of complications such as **ARDS (acute respiratory distress syndrome)** and fat embolism for critically ill patients. *Compound fracture* - **Compound (open) fractures** involve a break in the skin, exposing the bone to the external environment, and are a classic indication for surgical management. - ORIF in these cases helps to achieve **stabilization** after debridement, crucial for preventing infection and promoting bone healing. *Intra-articular fracture* - **Intra-articular fractures** involve the joint surface, and accurate anatomical reduction is critical to prevent post-traumatic arthritis and preserve joint function. - ORIF provides the precise reduction and stable fixation needed to restore the **joint congruity**.
Question 8: Following a road traffic accident, a patient develops type IIIa compound tibial fracture. Arrange the following external fixators in decreasing order of their stability (highest to lowest) 1. Ilizarov fixator 2. Uniplanar with a single rod 3. Uniplanar with double rod 4. Biplanar frame/Ring with a cylindrical rod
- A. 1>4>3>2 (Correct Answer)
- B. 2>4>3>1
- C. 1>2>3>4
- D. 2>3>1>4
Explanation: ***1>4>3>2*** - **Ilizarov fixator** utilizes multiple wires **under tension** and rings, providing the most **biologically stable** and rigid fixation due to its distributed force across the bone. - **Biplanar frames/Rings with a cylindrical rod** offer high stability by providing pin fixation in **two different planes**, significantly resisting bending and torsional forces. - **Uniplanar with double rod** provides better stability than a single rod by increasing the **moment of inertia** and reducing deflection under axial and bending loads. - **Uniplanar with a single rod** is the least stable due to its limited resistance to **torsional** and **bending forces** as pin placement is restricted to a single plane.
Question 9: What is the best treatment for a 60-year-old man with intracapsular femoral neck fracture?
- A. Hemiarthroplasty (Correct Answer)
- B. Total hip replacement
- C. Internal fixation
- D. Casting
Explanation: **Hemiarthroplasty** * **Hemiarthroplasty** is generally preferred in older patients with **displaced intracapsular femoral neck fractures** due to the high risk of **avascular necrosis** and non-union with internal fixation. * In a 60-year-old, a hemiarthroplasty provides a good balance between **mobility** and avoiding the complexities of a total hip replacement, especially if the patient has lower functional demands or comorbidities. *Total hip replacement* * **Total hip replacement** might be considered for younger, more active patients with minimal comorbidities, or older patients with pre-existing **hip arthritis**, as it offers better long-term function and pain relief. * However, it's a more extensive procedure with a higher risk of complications like **dislocation** and necessitates careful selection based on the patient's physiological age and functional expectations. *Internal fixation* * **Internal fixation** is primarily used for **non-displaced** or minimally displaced intracapsular femoral neck fractures in active patients, or displaced fractures in younger patients (usually <60 years old) to preserve their native femoral head. * In a 60-year-old with a displaced fracture, the risk of **avascular necrosis** of the femoral head and **non-union** is significantly higher with internal fixation, making it a less preferred option. *Casting* * **Casting** is not an appropriate treatment for a femoral neck fracture. * Femoral neck fractures are **intra-articular** and require surgical stabilization to achieve stability and allow for early mobilization.
Question 10: Which one of the following is the most ideal treatment for a displaced fracture of the lateral condyle of the humerus in a 7-year-old child?
- A. Open reduction and internal fixation (Correct Answer)
- B. Open reduction with plaster immobilization
- C. Closed reduction with plaster immobilization
- D. All of the above
Explanation: ***Open reduction and internal fixation*** - **Displaced lateral condyle fractures** in children require **anatomical reduction** and stable fixation to prevent complications like **non-union** and **cubitus valgus deformity**. - **Internal fixation** provides the necessary stability for healing and allows for earlier mobilization, which is crucial for elbow joint function. *Open reduction with plaster immobilization* - While it achieves open reduction, relying solely on **plaster immobilization** after reducing a displaced fracture of the lateral humeral condyle in a child often leads to **loss of reduction**. - This method does not provide adequate stability for this type of fracture, increasing the risk of **displacement** and **malunion**. *Closed reduction with plaster immobilization* - **Closed reduction** is typically attempted only for **minimally displaced** or **undisplaced fractures** of the lateral condyle. - Given that the fracture is described as **displaced**, closed reduction is unlikely to achieve and maintain an adequate anatomical alignment.
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