Orthopaedic Techniques — MCQs

Orthopaedic Techniques Indian Medical PG Practice Questions and MCQs

Question 21: For which of the following conditions is a wedging technique used?

A. Internal fixation with plates
B. Internal fixation with a nail
C. Plaster of Paris cast (Correct Answer)
D. Plaster of Paris slab

Explanation: ### Explanation **Concept of Wedging** Wedging is a specialized technique used to correct a **residual angular deformity** in a fracture that has already been immobilized in a complete, circumferential **Plaster of Paris (POP) cast**. It is a non-invasive method to improve alignment without removing the entire cast. The process involves making a linear cut (opening) in the cast at the level of the fracture. There are two types: 1. **Closing wedge:** A segment of the cast is removed on the convex side of the deformity, and the gap is closed. 2. **Opening wedge:** The cast is cut on the concave side, the gap is pried open to straighten the bone, and the resulting space is packed with wood or cork before being overwrapped with fresh plaster. **Analysis of Options** * **Option C (Correct):** Wedging is exclusively performed on circumferential **casts**. It relies on the rigid, 360-degree structural integrity of the cast to act as a lever to manipulate the bone fragments. * **Option D (Incorrect):** A **slab** is a partial, non-circumferential splint. Since it does not encircle the limb, it cannot provide the necessary leverage for wedging; if the alignment is poor in a slab, the slab is simply removed and reapplied. * **Options A & B (Incorrect):** Internal fixation (plates or nails) involves surgical stabilization. If alignment is unsatisfactory post-operatively, it requires surgical revision (re-operation), not a manual cast technique. **High-Yield Clinical Pearls for NEET-PG** * **Timing:** Wedging is typically done 7–10 days after the initial cast application, once the initial swelling has subsided. * **Indication:** It is most commonly used for fractures of the **tibia and forearm** where minor angulation persists on follow-up X-rays. * **Precaution:** Always perform a follow-up X-ray immediately after wedging to confirm the correction and ensure no new pressure points were created.

Question 22: What is the optimum rate of bone movement during distraction osteogenesis?

A. 1 mm per day (Correct Answer)
B. 5 mm per day
C. 1 cm per week
D. 5 cm per week

Explanation: **Explanation:** Distraction osteogenesis is a biological process of regenerating new bone by progressive distraction (pulling apart) of a fracture or osteotomy site. This technique, popularized by **Gavriil Ilizarov**, relies on the "tension-stress effect" to stimulate bone formation. **Why 1 mm per day is correct:** The optimum rate of distraction is **1 mm per day**, typically divided into four increments of **0.25 mm every 6 hours** (rhythm). This rate is physiological; it allows the soft tissues and blood vessels to adapt while stimulating osteoblasts to lay down new bone (osteoid) in the gap. **Analysis of Incorrect Options:** * **B & D (5 mm per day / 5 cm per week):** These rates are too rapid. Fast distraction leads to "non-union" or "fibrous union" because the blood vessels and osteoblasts cannot bridge the gap quickly enough, resulting in a failure of bone formation. * **C (1 cm per week):** This equates to approximately 1.4 mm per day. While closer to the correct value, it is still slightly too fast and increases the risk of nerve stretch injuries and poor regenerate quality. Conversely, a rate slower than 0.5 mm/day leads to "premature consolidation," where the bone heals too quickly and prevents further lengthening. **High-Yield Clinical Pearls for NEET-PG:** 1. **Latency Period:** After the initial corticotomy, a waiting period of **5–7 days** is required before starting distraction to allow for callus formation. 2. **Consolidation Phase:** Once the desired length is achieved, the fixator remains in place for roughly **twice the duration** of the distraction phase to allow the new bone to mineralize. 3. **The Ilizarov Principle:** Success depends on three factors: stable fixation, a latency period, and the correct rate/rhythm of distraction (1 mm/day).

Question 23: What is the maximum weight typically allowed in skeletal traction?

A. 5 kg
B. 10 kg
C. 20 kg (Correct Answer)
D. 30 kg

Explanation: **Explanation:** **Skeletal traction** involves the insertion of a metal pin (e.g., Steinman pin or Denham pin) directly into the bone, allowing for the application of significant force to overcome muscle spasms and maintain fracture alignment. **1. Why 20 kg is correct:** The maximum weight typically allowed in skeletal traction is **20 kg (or approximately 1/7th to 1/10th of the patient's body weight)**. This limit is established because skeletal traction bypasses the skin, applying force directly to the skeleton. While it can tolerate much higher loads than skin traction, weights exceeding 20 kg increase the risk of "pin tract" complications, such as pin loosening, bone necrosis, or cutting through the bone (cheese-wiring effect), and can lead to over-distraction of the fracture site. **2. Analysis of incorrect options:** * **5 kg (Option A):** This is the typical maximum limit for **Skin Traction**. Applying more than 5 kg to the skin leads to blistering, excoriation, and potential compartment syndrome. * **10 kg (Option B):** While commonly used for femur fractures, this is not the upper limit. Skeletal traction is designed to handle more weight than this to overcome the powerful thigh musculature. * **30 kg (Option C):** This weight is excessive and clinically dangerous. It would likely cause neurovascular stretching and significant damage to the bone-pin interface. **High-Yield Clinical Pearls for NEET-PG:** * **Skin Traction:** Max weight 5 kg (1/10th of body weight). * **Skeletal Traction:** Max weight 20 kg (1/7th of body weight). * **Common Sites:** Upper tibial tubercle (most common for femur fractures), calcaneum, and distal femur. * **Complication:** The most common complication of skeletal traction is **Pin Tract Infection**. * **Contraindication:** Never place a skeletal pin through an open growth plate (epiphysis) in children.

Question 24: Which test is used to detect a flexion deformity?

A. Trendelenburg test
B. Thomas test (Correct Answer)
C. FABER test
D. Stinchfield test

Explanation: The **Thomas test** is the gold standard clinical examination used to detect and quantify a **fixed flexion deformity (FFD) of the hip**. ### Why Thomas Test is Correct In a normal hip, the lumbar spine compensates for a flexion deformity by increasing its lordosis (arching), which allows the leg to lie flat on the table, masking the deformity. * **Mechanism:** The clinician flexes the contralateral (normal) hip until the lumbar spine is flattened against the examination table (obliterating lumbar lordosis). * **Result:** If an FFD is present in the test hip, the thigh will spontaneously lift off the table. The angle between the thigh and the table represents the degree of the fixed flexion deformity. ### Explanation of Incorrect Options * **A. Trendelenburg Test:** Used to assess the stability of the hip and the strength of the **hip abductors** (Gluteus medius and minimus). A positive test indicates abductor paralysis, hip dislocation, or Coxa vara. * **C. FABER Test (Patrick’s Test):** Stands for Flexion, Abduction, and External Rotation. It is primarily used to identify **Sacroiliac (SI) joint involvement** or intra-articular hip pathology. * **D. Stinchfield Test:** Used to detect **intra-articular hip pathology** (like labral tears or arthritis). The patient performs a resisted straight leg raise; pain in the groin indicates a positive result. ### NEET-PG Clinical Pearls * **Psoas Abscess:** A common cause of a positive Thomas test in the Indian context (due to psoas irritation). * **The "Rule of 3":** To ensure lumbar flattening during the Thomas test, the clinician should be able to pass their hand under the lumbar spine initially and feel it tighten against the hand as the opposite hip is flexed. * **Modified Thomas Test:** Used to assess tightness of the Rectus Femoris (if the knee fails to flex to 90° while the hip is extended).

Question 25: What is the latency period in distraction osteogenesis?

A. 4-7 days (Correct Answer)
B. 4 weeks
C. 15 days
D. 1 month

Explanation: **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).

Question 26: What is an emergency screw?

A. A screw that is used in cases of emergency fracture management for direct application across bone segments, like fracture during third molar extraction
B. The next largest outer thread diameter screw, that is used when the hole is drilled too large for the chosen screw (Correct Answer)
C. A compression screw that is used with a dynamic compression plate when one or more screws are not available
D. A long, wide screw that can be used in any circumstance, regardless of type or location of fracture

Explanation: In orthopaedic surgery, achieving "stable internal fixation" depends on the **purchase** (grip) of the screw threads within the bone. ### **Explanation of the Correct Answer** An **emergency screw** (also known as an "oversize screw" or "rescue screw") is used when the initial screw fails to tighten because the pilot hole was drilled too large or the bone threads have "stripped" (lost their grip). The underlying concept is based on **thread diameter**. An emergency screw has a **larger outer (thread) diameter** but the **same core diameter** as the original screw. This allows the larger threads to bite into the fresh bone surrounding the failed hole without requiring additional drilling or changing the plate. For example, if a 3.5 mm cortical screw strips, a 4.0 mm emergency screw is used. ### **Analysis of Incorrect Options** * **Option A:** While fractures during dental extractions are emergencies, the term "emergency screw" is a specific technical nomenclature in hardware design, not a description of the clinical urgency. * **Option C:** A screw used when others are unavailable is simply a substitute. It does not address the mechanical failure of the bone-screw interface. * **Option D:** No single screw is universal. Screws must be matched to the specific bone (cortical vs. cancellous) and the plate hole size. ### **NEET-PG High-Yield Pearls** * **Pitch:** The distance between two adjacent threads. * **Core Diameter:** Determines the strength of the screw and the size of the drill bit required. * **Outer Diameter:** Determines the "pull-out strength." * **Cortical vs. Cancellous:** Cortical screws have a smaller pitch (finer threads); cancellous screws have a larger pitch (deeper threads) to grip porous bone.

Question 27: Chemically, what is Plaster of Paris (POP)?

A. Calcium carbonate
B. Calcium sulfate
C. Anhydrous calcium sulfate
D. Hemihydrous calcium sulfate (Correct Answer)

Explanation: **Explanation:** Plaster of Paris (POP) is the most commonly used material for immobilization in orthopaedics. It is derived from **Gypsum**, which is naturally occurring Calcium sulfate dihydrate ($CaSO_4 \cdot 2H_2O$). When gypsum is heated to approximately 120°C (250°F), it loses three-quarters of its water of crystallization through a process called calcination, resulting in **Calcium sulfate hemihydrate** ($(CaSO_4)_2 \cdot H_2O$ or $CaSO_4 \cdot 0.5H_2O$). This hemihydrate form is what we call Plaster of Paris. **Analysis of Options:** * **Option D (Correct):** Hemihydrous calcium sulfate is the chemical name for POP. When water is added back to this powder, an **exothermic reaction** occurs, reverting it to the hard crystalline dihydrate (Gypsum). * **Option A:** Calcium carbonate is the primary component of eggshells and chalk; it has no role in orthopaedic casting. * **Option B:** Calcium sulfate is a general term, but it lacks the specific hydration state (hemihydrate) required for the setting properties of POP. * **Option C:** Anhydrous calcium sulfate (Dead burnt plaster) is formed if gypsum is overheated (>200°C). It loses all water and will not set when mixed with water, making it useless for clinical casting. **High-Yield Clinical Pearls for NEET-PG:** 1. **Exothermic Reaction:** The setting of POP releases heat. Excessive layers or using hot water can cause skin burns. 2. **Setting Time:** Controlled by additives. **Salt (NaCl)** or warm water accelerates setting, while **Borax** or cold water acts as a retarder. 3. **Strength:** A POP cast takes about 48–72 hours to reach its maximum strength (completely dry). 4. **Green Strength:** The initial strength of the cast when it is still damp.

Question 28: Glass holding cast is also known as:

A. Colles' cast
B. Smith's cast
C. Sarmento cast
D. Scaphoid cast (Correct Answer)

Explanation: **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.

Question 29: Knuckle bender splint is used for which of the following conditions?

A. Ulnar nerve palsy (Correct Answer)
B. Radial nerve palsy
C. Median nerve palsy
D. Axillary nerve palsy

Explanation: **Explanation:** The **Knuckle Bender Splint** (also known as the Bunnell Splint) is primarily used to correct the **claw hand deformity** seen in **Ulnar Nerve Palsy**. **1. Why Ulnar Nerve Palsy is Correct:** In ulnar nerve palsy, there is paralysis of the lumbricals (specifically the 3rd and 4th). Since lumbricals normally flex the metacarpophalangeal (MCP) joints and extend the interphalangeal (IP) joints, their loss leads to the opposite: hyperextension at the MCP joints and flexion at the IP joints (Clawing). The Knuckle Bender splint uses a mechanical three-point pressure system to force the **MCP joints into flexion**, thereby counteracting the deformity and preventing joint contractures. **2. Why other options are incorrect:** * **Radial Nerve Palsy:** Characterized by "Wrist Drop." The treatment of choice is a **Cock-up splint** or a **Dynamic Radial Nerve Splint** (to assist wrist and finger extension). * **Median Nerve Palsy:** Characterized by "Ape Thumb Deformity" (loss of opposition). The specific splint used is the **Opponens Splint**. * **Axillary Nerve Palsy:** Results in deltoid paralysis and loss of shoulder abduction. Splinting is rarely the primary focus, though an **Aeroplane Splint** may be used in certain brachial plexus injuries to maintain abduction. **High-Yield Clinical Pearls for NEET-PG:** * **Reverse Knuckle Bender:** Used to treat extension contractures by forcing the MCP joints into extension. * **Ulnar Paradox:** The higher the lesion (at the elbow), the less obvious the clawing; the lower the lesion (at the wrist), the more severe the clawing. * **Thomas Splint:** Used for immobilization of femur fractures. * **Bohler-Braun Splint:** A hardware frame used for skeletal traction in lower limb fractures.

Question 30: What is the recommended rhythm of distraction osteogenesis as advised by Ilizarov?

A. Continuous
B. 0.25 mm four times a day (Correct Answer)
C. 0.33 mm three times a day
D. 1.0 mm four times a day

Explanation: **Explanation:** The concept of **Distraction Osteogenesis**, pioneered by Gavriil Ilizarov, relies on the "Law of Tension-Stress." This principle states that gradual, controlled traction on living tissues creates a biological stimulus that activates regenerative processes in both bone and soft tissues. **Why Option B is Correct:** Ilizarov determined that the optimal rate of distraction for bone regeneration is **1.0 mm per day**. However, the **rhythm** (frequency) of distraction is equally critical. Dividing the 1.0 mm daily rate into smaller, frequent increments—specifically **0.25 mm four times a day**—minimizes trauma to the regenerate (the new bone forming in the gap) and the surrounding soft tissues. This frequency maintains a constant state of tension that promotes osteogenesis and angiogenesis without disrupting the delicate capillary network. **Analysis of Incorrect Options:** * **Option A (Continuous):** While theoretically ideal (using automated pumps), it is clinically impractical for most patients using manual circular fixators. * **Option C (0.33 mm three times a day):** This rhythm is less biological than the four-step division. Larger gaps between distractions can lead to "jerky" movements that may damage the forming callus. * **Option D (1.0 mm four times a day):** This would result in a total distraction of 4.0 mm/day. This is too rapid and leads to "non-union" or the formation of poor-quality fibrous tissue instead of bone. **High-Yield Clinical Pearls for NEET-PG:** * **Latency Period:** The time between corticotomy and the start of distraction (usually **5–7 days**). * **Consolidation Phase:** The period where the fixator remains in situ to allow the regenerate to mineralize (usually twice as long as the distraction time). * **Rate Complications:** If distraction is too slow (<1 mm/day), premature consolidation (early bone healing) occurs. If too fast (>1 mm/day), it leads to nerve palsies and fibrous non-union.

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

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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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