Orthopaedic Techniques — MCQs

Orthopaedic Techniques Indian Medical PG Practice Questions and MCQs

Question 91: Which of the following methods is used for titanium investment casting?

A. Casting under air pressure in a nitrogen atmosphere
B. Using aluminum vanadium crucibles for casting
C. Using CAD-CAM for design
D. Casting under vacuum in an argon atmosphere (Correct Answer)

Explanation: ***Casting under vacuum in an argon atmosphere*** - **Titanium** is highly reactive at casting temperatures and will readily oxidize in the presence of oxygen or nitrogen, hence why it must be cast in a **vacuum** or an **inert atmosphere** like argon. - The vacuum environment prevents oxidation, while the argon atmosphere further ensures an inert environment, protecting the molten titanium from atmospheric contaminants. *Casting under air pressure in a nitrogen atmosphere* - **Nitrogen** reacts with molten titanium to form titanium nitride, which is a brittle compound, compromising the mechanical properties of the cast. - Casting under **air pressure** would introduce oxygen, leading to significant oxidation and degradation of the titanium. *Using aluminum vanadium crucibles for casting* - **Aluminum vanadium** is an alloy often used with titanium, but it is not suitable as a crucible material because molten titanium would react with and dissolve the crucible. - Crucibles for titanium casting must generally be made of non-reactive materials like **graphite** or specialized ceramic crucibles. *Using CAD-CAM for design* - **CAD-CAM** (Computer-Aided Design/Computer-Aided Manufacturing) is a design and manufacturing tool used to create patterns and molds, but it is not a method for the actual casting process itself. - While CAD-CAM is often employed in the preparation of titanium prostheses, it pertains to the **design and fabrication of the mold**, not the environment of the molten metal during casting.

Question 92: 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 93: Treatment of choice for a non-united fracture of the lower 1/4th of the tibia, characterized by multiple discharging sinuses and various puckered scars, with a 4cm shortening of the leg?

A. External fixator
B. Plating
C. Intramedullary nail
D. Ilizarov's fixator (Correct Answer)

Explanation: ***Ilizarov's fixator*** - The presence of **multiple discharging sinuses** and **puckered scars** indicates chronic osteomyelitis, making bone transport and compression-distraction osteogenesis with an Ilizarov frame ideal. - The **4cm shortening** of the leg can be simultaneously corrected by limb lengthening through distraction osteogenesis using the Ilizarov technique. *External fixator* - While an external fixator can provide stability, a standard external fixator does not offer the same capabilities for **bone transport** or precise **limb lengthening** needed to address osteomyelitis and 4cm shortening simultaneously. - It would be less effective in managing the **infected non-union** and leg length discrepancy compared to an Ilizarov. *Plating* - **Plating** is generally contraindicated in cases of **active infection** (indicated by discharging sinuses) due to the high risk of further bacterial colonization of the implant and implant failure. - It would not address the **bone defect** or the **4cm shortening** effectively in an infected context. *Intramedullary nail* - **Intramedullary nailing** is absolutely contraindicated in the presence of **active infection** and discharging sinuses, as it would spread the infection throughout the medullary canal. - It also does not allow for **segmental bone resection** and subsequent limb lengthening to address both the infection and shortening.

Question 94: What is the primary mechanism of fixation provided by an intramedullary K nail (Kirschner wire) in orthopedic surgery?

A. Two-point fixation
B. Three-point fixation (Correct Answer)
C. Compression
D. Weight concentration

Explanation: ***Three-point fixation*** - Intramedullary K nails utilize **three-point fixation** by engaging two points of contact in the wider metaphyseal bone and one point at the apex of the fracture. - This mechanism allows the nail to be inserted into the medullary canal and act as an internal splint, providing stability against bending and shear forces. *Two-point fixation* - **Two-point fixation** is generally insufficient for long-bone fractures, as it only resists bending in one plane and offers limited rotational stability. - While intramedullary nails have two main points of contact at the ends, the additional contact at the fracture site creates a three-point system for enhanced stability. *Compression* - While some intramedullary nails can provide **compression** through dynamization or specific locking mechanisms, this is not their primary or inherent mechanism of fixation as a simple K nail. - Compression is more typically achieved with plates, screws, or external fixators directly apposing fracture fragments. *Weight concentration* - **Weight concentration** is not a biomechanical principle of fracture fixation; rather, it refers to the distribution of forces over a surface. - Intramedullary nails aim to redistribute forces and provide structural support, but not primarily by "weight concentration."

Question 95: Patellar tendon-bearing P.O.P. cast is indicated in the following fracture:

A. Fracture of the tibia (Correct Answer)
B. Fracture of the patella
C. Fracture of the femur
D. Fracture of the medial malleolus

Explanation: ***Fracture of the tibia*** - A **patellar tendon-bearing (PTB) cast** is specifically designed to bypass the knee joint and transfer weight from the patellar tendon to the cast, offloading the tibia. - This design is particularly useful for **stable, distal tibia fractures** where partial weight-bearing is desired to promote healing. *Fracture of the patella* - A PTB cast would place direct pressure on the **patella**, which is contraindicated in a patellar fracture. - Patellar fractures often require a **cylinder cast** or surgical fixation to immobilize the knee. *Fracture of the femur* - Femoral fractures are typically **more proximal** and require **traction**, **internal fixation**, or a **spica cast** for stabilization. - A PTB cast would not provide adequate immobilization or weight-bearing relief for a femoral fracture due to its design. *Fracture of the medial malleolus* - Medial malleolus fractures involve the **ankle joint**, which is distal to the area covered by a PTB cast. - These fractures typically require a **short leg cast** or surgical repair, focusing on ankle stabilization.

Question 96: Which of the following does not affect the setting time of the material?

A. Tap water
B. Temperature of the water
C. Hot weather
D. Insufficient mixing (Correct Answer)

Explanation: ***Insufficient mixing*** - **Insufficient mixing** of the material primarily affects the **homogeneity** and **strength** of the final product, potentially leading to a weaker or improperly set material, but it does not directly alter the chemical reaction rate that dictates setting time. - While it can result in areas that are not properly set, the actual chemical setting process, once initiated, proceeds at its inherent rate dictated by other factors. *Tap water* - **Ions** and impurities present in tap water can act as **accelerators** or **retarders** for the setting reaction of many dental materials, altering the setting time. - For example, **calcium sulfate dihydrate** (gypsum) setting can be accelerated by some salts found in tap water. *Temperature of the water* - An **increase in the temperature of the water** used for mixing generally **accelerates** the chemical reactions, leading to a shorter setting time for most dental materials. - Conversely, colder water will typically **retard** the setting reaction, increasing the setting time. *Hot weather* - **Hot weather** can indirectly affect the setting time by increasing the **ambient temperature** of the water and the materials themselves. - Elevated ambient temperatures will cause the material to reach its setting point faster due to **accelerated chemical reactions**.

Question 97: Trendelenburg's test is positive in all except which of the following conditions?

A. Poliomyelitis affecting hip abductor muscles
B. Femoral neck fracture
C. Tuberculosis of hip joint (Correct Answer)
D. Posterior dislocation of the hip

Explanation: ***Tuberculosis of hip joint*** - While **tuberculosis of the hip joint** can cause pain and limping, a positive Trendelenburg's test is not a direct or consistent finding. The test primarily indicates weakness of the **hip abductor muscles** or an unstable hip joint, which is not the primary presentation in hip TB unless there's associated muscle atrophy or severe joint destruction. - The characteristic signs of hip tuberculosis often include **night cries**, muscle spasm, and joint stiffness rather than gluteal muscle weakness. *Poliomyelitis affecting hip abductor muscles* - **Poliomyelitis** can cause **flaccid paralysis** and weakness of muscles, including the hip abductors. - Weakness of the **gluteus medius** and **minimus** muscles directly leads to a positive Trendelenburg's sign. *Femoral neck fracture* - A **femoral neck fracture** often leads to an **unstable hip joint** and pain, making it difficult for the patient to bear weight on the affected side. - The pain and instability inhibit the effective action of the hip abductors, resulting in a positive **Trendelenburg's test**. *Posterior dislocation of the hip* - A **posterior dislocation of the hip** disrupts the normal anatomical relationship of the femoral head and acetabulum, leading to mechanical instability. - This instability prevents the hip abductors from effectively stabilizing the pelvis during single-limb stance, thus causing a positive **Trendelenburg's sign**.

Question 98: In Wits' appraisal, the AO and BO measurements represent the relationship between which of the following?

A. Maxillary apical base to mandibular apical base (Correct Answer)
B. Maxilla to cranium
C. Mandible to cranium
D. Cranial base to maxilla

Explanation: ***Maxillary apical base to mandibular apical base*** - Wits' appraisal uses the projection of points A (maxillary apical base) and B (mandibular apical base) onto the **occlusal plane** to assess the anteroposterior relationship between the maxilla and mandible. - The distance between these projected points, **AO and BO**, indicates the sagittal skeletal discrepancy. *Maxilla to cranium* - Measurements like **SNA (sella-nasion-A point)** are used to assess the anteroposterior position of the maxilla relative to the cranial base, not directly by Wits' appraisal. - While cranial reference points are used in cephalometrics, Wits' directly compares the **apical bases** to each other. *Mandible to cranium* - Measurements such as **SNB (sella-nasion-B point)** evaluate the anteroposterior position of the mandible relative to the cranial base. - Wits' specifically focuses on the inter-jaw relationship, rather than each jaw's individual relationship to the skull. *Cranial base to maxilla* - This relationship is assessed by angles like **SNA**, providing information on maxillary protrusion or retrusion in relation to the cranium. - Wits' appraisal eliminates the influence of cranial base variations by comparing the projected points directly on the **occlusal plane**.

Question 99: Pioneer of distraction osteogenesis is:

A. Codivilla
B. Snyder
C. Ilizarov (Correct Answer)
D. Alexander

Explanation: ***Ilizarov*** - **Gavriil Abramovich Ilizarov** is widely recognized as the pioneer of **distraction osteogenesis**, developing the biological principles and surgical techniques in the 1950s. - His method involved gradually separating a corticotomy site to stimulate new bone formation, a technique now fundamental in limb lengthening and reconstructive surgery. *Codivilla* - **Alessandro Codivilla** was an Italian surgeon who performed limb lengthening in the early 20th century, but his method involved acute distraction, which often led to complications like joint subluxation and non-union. - His work predated Ilizarov's systematic approach to gradual distraction and neo-osteogenesis. *Snyder* - **Snyder** is not specifically recognized as a pioneer in the early development of distraction osteogenesis in the same historical context as Ilizarov or Codivilla. - His contributions, if any, are not central to the fundamental principles or widespread adoption of the technique. *Alexander* - The name **Alexander** is not directly associated with the pioneering work or development of distraction osteogenesis in orthopedic surgery. - While many surgeons have contributed to advancements in the field, Alexander is not credited with its fundamental principles.

Practice by Chapter

Principles of Internal Fixation

Practice Questions

External Fixation

Practice Questions

Intramedullary Nailing

Practice Questions

Plate Osteosynthesis

Practice Questions

Tension Band Wiring

Practice Questions

Minimally Invasive Orthopaedic Surgery

Practice Questions

Arthroscopic Techniques

Practice Questions

Suture Techniques in Orthopaedics

Practice Questions

Navigation and Robotics

Practice Questions

3D Printing Applications

Practice Questions

Bone Grafting Techniques

Practice Questions

Local Flaps and Soft Tissue Coverage

Practice Questions

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