Orthopaedic Techniques Practice Questions

Q: What is the latency period in distraction osteogenesis?

4-7 days. **Distraction Osteogenesis** is a biological process of regenerating bone by mechanical stretching of a vascularized bone callus. This technique, popularized by **Gavriil Ilizarov**, follows a specific chronological sequence: ### 1. Why 4-7 days is correct? The **Latency Period** is the duration between the performance of the corticotomy (surgical bone cut) and the commencement of active traction (distraction). * **Purpose:** This period allows for the formation of a soft tissue bridge and an initial **reparative callus** (pro-callus). * **Duration:** In humans, this typically lasts **5 to 7 days** (accepted range 4–10 days). Starting too early prevents callus formation, while starting too late leads to premature consolidation (bone healing before lengthening is complete). ### 2. Analysis of Incorrect Options * **B & D (4 weeks / 1 month):** These durations are far too long. By 4 weeks, the bone ends would have undergone significant ossification, making it impossible to distract the bone without re-fracturing it. * **C (15 days):** While some specific craniofacial protocols might vary, 15 days is generally considered too long for long-bone lengthening, as the osteogenic bridge becomes too rigid to stretch effectively. ### 3. High-Yield Clinical Pearls for NEET-PG * **The Ilizarov Principle (Law of Tension-Stress):** Gradual traction on living tissues creates a metabolic signal that stimulates the regeneration of bone and soft tissues. * **Rate of Distraction:** The standard rate is **1 mm per day**. * **Rhythm of Distraction:** Usually divided into **0.25 mm four times a day** (frequent small increments are more osteogenic than one large increment). * **Phases:** 1. **Latency:** 5–7 days. 2. **Distraction:** 1 mm/day. 3. **Consolidation:** The period where the new bone (regenerate) mineralizes (usually takes twice as long as the distraction phase).

Q: Glass holding cast is also known as:

Scaphoid cast. **Explanation:** The **Scaphoid cast** is famously referred to as the **"Glass holding cast"** because the position of the hand during application mimics the posture of holding a glass of water. **Why it is the correct answer:** The scaphoid cast is used for fractures of the scaphoid bone. To stabilize this fracture, the wrist is placed in slight radial deviation and dorsiflexion (extension), with the thumb maintained in a "functional" or "opposed" position (abducted and extended). This specific orientation—holding the thumb out as if gripping a cylinder—is why it is called the glass holding position. The cast typically extends from the upper forearm to the distal palmar crease and includes the thumb up to the interphalangeal joint (thumb spica). **Analysis of incorrect options:** * **Colles’ cast:** Used for distal radius fractures with dorsal displacement. It is a below-elbow cast applied with the wrist in slight palmar flexion and ulnar deviation (Charnley’s position). * **Smith’s cast:** Used for distal radius fractures with volar displacement (reverse Colles'). The wrist is immobilized in slight extension (dorsiflexion). * **Sarmiento cast:** This is a **Patellar Tendon Bearing (PTB) cast** used for fractures of the tibia. It allows for knee movement while stabilizing the fracture through hydrostatic pressure and loading the patellar tendon. **High-Yield Clinical Pearls for NEET-PG:** * **Scaphoid Fracture:** The most common carpal bone fracture; risk of **Avascular Necrosis (AVN)** is high due to retrograde blood supply. * **Tenderness:** Specifically located in the **Anatomical Snuffbox**. * **Cast Duration:** Often requires prolonged immobilization (6–12 weeks) due to the poor blood supply of the proximal pole.

Q: Which of the following is NOT used for skeletal traction?

Pavlik harness. **Explanation:** The core concept here is the distinction between **Skeletal Traction** and **Orthotic/Skin devices**. **Why Pavlik Harness is the correct answer:** The **Pavlik harness** is a functional dynamic **orthosis**, not a traction device. It is the gold standard treatment for Developmental Dysplasia of the Hip (DDH) in infants under 6 months. It works by maintaining the hips in "human position" (flexion and abduction) to allow the acetabulum to deepen. It does not involve the insertion of pins into bone or the application of a pulling force via weights. **Analysis of Incorrect Options:** * **Steinmann’s Pin:** A rigid, stainless steel pin (3-6 mm diameter) used for heavy skeletal traction in large bones like the femur or tibia. * **Denham Pin:** Similar to a Steinmann pin but features a **threaded central portion**. This threading provides a better grip in the bone, preventing the pin from sliding, making it ideal for use in osteoporotic bone. * **K-wire (Kirschner wire):** Thin, sharp wires used for skeletal traction in smaller bones (e.g., calcaneal traction) or in pediatric patients where larger pins might damage the physis. **High-Yield NEET-PG Pearls:** * **Common sites for Skeletal Traction:** Supracondylar (femur), Proximal Tibia (most common), and Calcaneum. * **Complication:** The most common complication of skeletal traction is **Pin Tract Infection**. * **Denham vs. Steinmann:** Remember, "Denham has a Thread" (D and T) to prevent side-to-side slipping. * **Pavlik Harness Contraindication:** It should not be used if the hip is stiff or in cases of teratologic dislocation. Over-flexion in a Pavlik harness can lead to **Femoral Nerve Palsy**.

Q: What is the correct direction for the bevel of a chisel when cutting bone?

Towards the bone to be sacrificed. **Explanation:** In orthopaedic surgery, understanding the geometry of cutting instruments is vital for precision. A **chisel** is a tool with a single beveled edge (unlike an osteotome, which is beveled on both sides). **1. Why the correct answer is B:** When using a chisel, the flat surface remains in contact with the bone you wish to preserve, while the **bevel faces the bone to be sacrificed**. As the chisel is driven forward, the wedge shape of the bevel naturally forces the blade to deviate away from the flat side. By placing the bevel towards the waste bone, the cutting edge "bites" into the unwanted portion, ensuring that the remaining bone surface is straight, smooth, and not inadvertently gouged or weakened. **2. Why other options are incorrect:** * **Option A:** If the bevel is away from the sacrificed bone (facing the preserved bone), the chisel will tend to dive deeper into the healthy bone, leading to an uneven cut or accidental fracture of the part you intend to keep. * **Option C:** The direction is never independent; surgical precision depends on the predictable "drift" caused by the bevel. * **Option D:** While stress lines (Wolff’s Law) are important for long-term healing, the immediate mechanical direction of a cut is determined by the instrument's bevel, not the stress lines. **High-Yield Clinical Pearls for NEET-PG:** * **Chisel vs. Osteotome:** A **Chisel** is beveled on **one side** (used for shaving/contouring). An **Osteotome** is beveled on **both sides** (used for splitting or deep bone cuts). * **Gouge:** A half-round chisel used for harvesting bone grafts or creating grooves. * **Directionality:** Always remember—**Flat side to the "Keep," Bevel side to the "Heap"** (the bone to be discarded).

Q: What is the rate of distraction beyond which soft tissue limits the distraction?

1.5 mm to 2.0 mm per day. ### Explanation The question pertains to the principles of **Distraction Osteogenesis**, a biological process popularized by **Gavriil Ilizarov**. This technique relies on the "Tension-Stress Effect," where slow, steady traction on living tissues stimulates the regeneration of both bone and soft tissues. **Why 1.5 mm to 2.0 mm per day is the limit:** The standard, ideal rate for bone distraction is **1.0 mm per day** (usually divided into four increments of 0.25 mm). At this rate, bone and soft tissues (muscles, nerves, and vessels) regenerate synchronously. However, research and clinical practice show that when the rate exceeds **1.5 mm to 2.0 mm per day**, the soft tissues cannot keep pace with the bone distraction. This leads to complications such as muscle contractures, nerve palsies, and vascular compromise. Therefore, 1.5–2.0 mm/day is considered the threshold beyond which soft tissue becomes the limiting factor. **Analysis of Incorrect Options:** * **A (0.5 mm to 1.0 mm/day):** This is considered the "safe zone." Rates below 0.5 mm/day often lead to **premature consolidation** (the bone heals too quickly, preventing further lengthening). * **B (1.0 mm to 1.5 mm/day):** While slightly faster than the ideal, soft tissues generally tolerate this range without significant failure. * **D (2.0 mm to 2.5 mm/day):** At this excessive rate, not only do soft tissues fail, but the bone itself fails to form, resulting in **non-union** or a "fibrous gap." **High-Yield Clinical Pearls for NEET-PG:** * **Ideal Rate:** 1 mm/day. * **Ideal Rhythm:** 0.25 mm four times a day (frequent small increments are more biological than one large daily stretch). * **Latency Period:** The waiting period between corticotomy and the start of distraction, typically **5 to 7 days**. * **Limiting Factor:** In limb lengthening, the **soft tissue** (specifically the nerves and muscles) is always the primary limiting factor, not the bone.

Q: Osteotomes differ from chisels in that they are

Bi-bevelled. **Explanation:** The fundamental difference between an osteotome and a chisel lies in the configuration of the cutting edge (the bevel). * **Osteotome (Bi-beveled):** An osteotome is tapered on **both sides** to form a central cutting edge. This design allows it to cut through bone in a straight line, as the equal pressure from both beveled surfaces prevents the tool from veering. It is primarily used for cutting or dividing bone (e.g., in corrective osteotomies). * **Chisel (Uni-beveled):** A chisel is beveled on only **one side**, while the other side remains flat. This design causes the tool to naturally "drift" or curve toward the flat side during use. It is primarily used for shaving, contouring, or harvesting bone grafts. **Analysis of Options:** * **A. Sharp:** Both instruments must be sharp to function effectively; this is not a distinguishing feature. * **B. Slightly curved:** While some specialized osteotomies (like the Lambotte) can be curved, "curved" refers to the longitudinal shape, not the cutting edge configuration. * **C. Non-beveled:** Both instruments require a bevel to create a cutting wedge; a non-beveled tool would be a blunt impactor. * **D. Bi-beveled (Correct):** This is the defining anatomical characteristic of an osteotome. **High-Yield Clinical Pearls for NEET-PG:** * **Gouge:** A specialized chisel with a **curved/U-shaped cross-section**, used for scooping out cancellous bone or creating troughs. * **Curette:** A spoon-shaped instrument used for scraping or debriding bone (e.g., in curettage of a Giant Cell Tumor). * **Periosteal Elevator:** Used to strip the periosteum from the bone; the most common eponymous version is the **Farabeuf** or **Langenbeck**.

Q: What is the recommended rate of distraction for small bone segments?

0.5 to 0.7 mm/day. **Explanation:** The question pertains to **Distraction Osteogenesis**, a biological process of new bone formation between two bone segments that are gradually separated by controlled traction. This technique is most commonly associated with the **Ilizarov method**. **1. Why 0.5 to 0.7 mm/day is correct:** The rate of distraction is critical for successful bone formation. For **small bone segments** (such as the metacarpals, metatarsals, or phalanges), the surface area of the bone ends is smaller, and the blood supply is more delicate compared to long bones. A rate of **0.5 to 0.7 mm/day** (usually divided into 2–4 increments) is recommended to allow the regenerate (new bone) to form without outstripping the local microvasculature. **2. Analysis of Incorrect Options:** * **A (0.3 to 0.5 mm/day):** This rate is generally too slow. Slow distraction can lead to **premature consolidation**, where the bone heals across the gap before the desired length is achieved, halting the process. * **C & D (0.7 to 1.0 mm/day):** While **1.0 mm/day** is the standard "gold vertical" rate for **large long bones** (like the femur or tibia), it is too aggressive for small bones. Distracting small bones at 1.0 mm/day often leads to **non-union** or poor-quality regenerate because the soft tissues and blood vessels cannot adapt quickly enough. **High-Yield Clinical Pearls for NEET-PG:** * **Standard Rate:** 1 mm/day (for long bones). * **Rhythm:** The frequency of distraction. 0.25 mm four times a day is superior to 1 mm once a day (promotes better osteogenesis). * **Latency Period:** The waiting period between corticotomy and the start of distraction, typically **5 to 7 days**. * **Stages of Ilizarov:** Corticotomy → Latency → Distraction phase → Consolidation phase (usually twice as long as the distraction phase).

Question 1

What is the latency period in distraction osteogenesis?

Accepted Answer

4-7 days

Answer

4 weeks

Answer

15 days

Answer

1 month

Question 2

Glass holding cast is also known as:

Accepted Answer

Scaphoid cast

Answer

Colles' cast

Answer

Smith's cast

Answer

Sarmento cast

Question 3

What is the recommended rhythm of distraction osteogenesis as advised by Ilizarov?

Accepted Answer

0.25 mm four times a day

Answer

Continuous

Answer

0.33 mm three times a day

Answer

1.0 mm four times a day

Question 4

Which type of distraction osteogenesis does not involve a transport disc?

Accepted Answer

Unifocal

Answer

Bifocal

Answer

Trifocal

Answer

Alveolar Distraction

Question 5

What is the recommended pressure used in a pneumatic tourniquet for the upper limb?

Accepted Answer

Systolic Blood Pressure + 75 mmHg

Answer

Systolic Blood Pressure + 50 mmHg

Answer

Systolic Blood Pressure + 100 mmHg

Answer

None of the above

Question 6

Which of the following is NOT used for skeletal traction?

Accepted Answer

Pavlik harness

Answer

K-wire

Answer

Denham pin

Answer

Steinmann's pin

Question 7

What is the correct direction for the bevel of a chisel when cutting bone?

Accepted Answer

Towards the bone to be sacrificed

Answer

Away from the bone to be sacrificed

Answer

Independent of the bone to be sacrificed

Answer

Parallel to stress lines

Question 8

What is the rate of distraction beyond which soft tissue limits the distraction?

Accepted Answer

1.5 mm to 2.0 mm per day

Answer

0.5 mm to 1.0 mm per day

Answer

1.0 mm to 1.5 mm per day

Answer

2.0 mm to 2.5 mm per day

Question 9

Osteotomes differ from chisels in that they are

Accepted Answer

Bi-bevelled

Answer

Sharp

Answer

Slightly curved

Answer

Non beveled

Question 10

What is the recommended rate of distraction for small bone segments?

Accepted Answer

0.5 to 0.7 mm/day

Answer

0.3 to 0.5 mm/day

Answer

0.7 to 0.9 mm/day

Answer

1.0 mm/day

Orthopaedic Techniques — MCQs

Orthopaedic Techniques — MCQs

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