Orthopaedic Techniques Practice Questions

Q: Which of the following statements is true regarding lag screw fixation?

Any threaded screw can be used in a lag screw fashion.. ### Explanation **1. Why Option A is Correct:** The term "lagging" refers to a **technique**, not necessarily a specific type of screw. Any screw (cortical or cancellous) can function as a lag screw if it achieves interfragmentary compression. This is done by ensuring the threads only engage the **distal fragment**, while the proximal fragment contains a "gliding hole" (where the screw slides through without gripping). When the screw head tightens against the near cortex, it pulls the distal fragment toward the proximal one, creating compression. **2. Why the Other Options are Incorrect:** * **Option B & C:** These are reversed. In lag screw technique, the **proximal segment** (near the screw head) must have the **gliding hole** (drilled to the same diameter as the screw's outer threads). The **distal segment** (far fragment) must have the **threaded hole** (drilled to the diameter of the screw's core/inner diameter) to allow the threads to "bite" and pull the fragment. * **Option D:** Lag screws should ideally be placed **perpendicular to the fracture line**, not the bone segments. Placing a screw perpendicular to the fracture ensures maximum interfragmentary compression and prevents shear forces that could cause the fracture to displace. **3. High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard:** Lag screw fixation is the most effective method for achieving **interfragmentary compression**. * **Partially Threaded Screws:** These act as "inherent" lag screws because the smooth shank automatically creates a gliding effect in the proximal fragment. * **Fully Threaded Screws:** To use these in a lag fashion, the surgeon must manually over-drill the proximal cortex to create a gliding hole. * **Sequence of Drilling:** Gliding hole (near cortex) → Drill sleeve insertion → Pilot hole (far cortex) → Countersinking → Measuring → Tapping → Screw insertion.

Q: Immobilization of the cervical spine with a plaster jacket is known as?

Minerva jacket.. **Explanation:** The **Minerva jacket** (or Minerva cast) is a specialized orthopedic plaster or fiberglass cast used to immobilize the **cervical and upper thoracic spine**. It typically extends from the head (incorporating the forehead or chin) down to the rib cage or waist. By stabilizing the head, neck, and trunk as a single unit, it prevents flexion, extension, and rotation of the cervical vertebrae. It is clinically indicated for stable cervical fractures, ligamentous injuries, or post-operative stabilization when a halo vest is not used. **Analysis of Options:** * **Minerva jacket (Correct):** Named after the Roman goddess of wisdom (often depicted wearing a helmet), this cast provides rigid immobilization of the neck and upper back. * **Maneuver jacket (Incorrect):** This is a distractor term. While "maneuvers" are common in orthopedics (e.g., Kocher’s maneuver for shoulder dislocation), there is no standard orthopedic cast known as a "Maneuver jacket." * **Sistrunk’s jacket (Incorrect):** This is a distractor. Sistrunk is a name associated with a surgical procedure for a **thyroglossal cyst** (Sistrunk’s operation), not an orthopedic immobilization technique. **High-Yield Clinical Pearls for NEET-PG:** * **Risser’s Cast:** Used for the treatment of Scoliosis (incorporates a localizer to apply pressure). * **Turnbuckle Cast:** Used for correcting lateral curvatures (Scoliosis). * **Hip Spica:** Used for pediatric femoral shaft fractures or Developmental Dysplasia of the Hip (DDH). * **Halo Vest:** The most rigid form of cervical immobilization, utilizing pins fixed into the skull; it is superior to the Minerva jacket for unstable fractures.

Q: What is the probable diagnosis in a patient presenting with bilious vomiting while wearing a spinal POP cast?

Duodenal obstruction. ### Explanation The correct diagnosis is **Duodenal Obstruction**, specifically a condition known as **Cast Syndrome** (also called Superior Mesenteric Artery Syndrome). **1. Why Duodenal Obstruction is Correct:** When a patient is in a tight spinal POP cast (especially in hyperextension), the third part of the duodenum can become compressed between the **Superior Mesenteric Artery (SMA)** anteriorly and the **Aorta/Vertebral column** posteriorly. This mechanical compression leads to high intestinal obstruction, manifesting as **bilious vomiting**, abdominal distension, and pain. It is a recognized complication of scoliosis surgery and body casting. **2. Why Incorrect Options are Wrong:** * **Acute Dilation of the Stomach (Option A):** While this can occur secondary to duodenal obstruction, the primary pathology triggered by the cast itself is the vascular compression of the duodenum. * **Peritonitis (Option C):** This presents with guarding, rigidity, and rebound tenderness, usually due to a perforated viscus or infection. It is not a direct complication of spinal casting. * **Acute Pancreatitis (Option D):** While it causes vomiting and epigastric pain, it is not etiologically linked to the mechanical pressure of a spinal cast. **3. NEET-PG High-Yield Pearls:** * **Cast Syndrome:** Also known as Wilkie’s syndrome or SMA syndrome. * **Clinical Presentation:** Persistent bilious vomiting after application of a hip spica or body cast. * **Immediate Management:** The first step is to **remove or bivalve the cast** to relieve pressure. Keep the patient NPO (nothing by mouth) and insert a nasogastric tube for decompression. * **Positioning:** Placing the patient in the **prone position** or **left lateral decubitus** can sometimes relieve the SMA compression.

Q: The Trendelenburg test is performed to assess the function of which muscles?

Gluteus medius and minimus. ### Explanation **1. Why Gluteus Medius and Minimus are correct:** The Trendelenburg test assesses the **abductor mechanism** of the hip. The primary hip abductors are the **Gluteus medius** (the main abductor) and the **Gluteus minimus**, both of which are innervated by the **Superior Gluteal Nerve**. When a person stands on one leg (the "stance leg"), these muscles must contract to stabilize the pelvis and prevent the opposite side (the "swing leg") from sagging. If these muscles are weak or paralyzed, or if the fulcrum (hip joint) is unstable, the pelvis drops on the unsupported side. This is a **Positive Trendelenburg Sign**, indicating abductor insufficiency on the **weight-bearing side**. **2. Why the other options are incorrect:** * **Gluteus Maximus (Options B, C, D):** This is the primary **extensor** of the hip and is innervated by the Inferior Gluteal Nerve. While it is vital for climbing stairs and rising from a seated position, it does not play a primary role in lateral pelvic stabilization during the Trendelenburg test. Including it in the answer is a common distractor. **3. High-Yield Clinical Pearls for NEET-PG:** * **The "Sound-Side" Drop:** In a positive test, the pelvis drops toward the **normal/healthy** side when standing on the **affected** side. * **Causes of Positive Trendelenburg:** 1. **Neuromuscular:** Superior gluteal nerve palsy, Polio. 2. **Muscular:** Myopathy, Gluteus medius tear. 3. **Structural (Lever arm issues):** Congenital Dislocation of the Hip (CDH/DDH), Coxa Vara, Slipped Capital Femoral Epiphysis (SCFE). 4. **Pain:** Antalgic gait due to osteoarthritis. * **Trendelenburg Gait:** Also known as a "lurching gait." If bilateral, it is called a **Waddling gait**.

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

Plaster of Paris cast. ### 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.

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

1 mm per day. **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).

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

20 kg. **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.

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).

Question 1

Which of the following statements is true regarding lag screw fixation?

Accepted Answer

Any threaded screw can be used in a lag screw fashion.

Answer

The proximal bone segment has the threaded hole.

Answer

The distal bone segment has the gliding hole.

Answer

Lag screws are placed perpendicular to the bone segments that they fix.

Question 2

Immobilization of the cervical spine with a plaster jacket is known as?

Accepted Answer

Minerva jacket.

Answer

Maneuver jacket.

Answer

Sistrunk's jacket.

Answer

All of the above.

Question 3

What is the action of an intramedullary 'K' nail?

Accepted Answer

Three-point fixation

Answer

Two-point fixation

Answer

Compression

Answer

Weight concentration

Question 4

What is the probable diagnosis in a patient presenting with bilious vomiting while wearing a spinal POP cast?

Accepted Answer

Duodenal obstruction

Answer

Acute dilation of the stomach

Answer

Peritonitis

Answer

Acute pancreatitis

Question 5

Which of the following statements is NOT true?

Accepted Answer

Crutchfield traction for lumbar spine injuries

Answer

Cock-up splint for radial nerve palsy

Answer

Russel traction for trochanteric fractures

Answer

Boston Brace for scoliosis

Question 6

The Trendelenburg test is performed to assess the function of which muscles?

Accepted Answer

Gluteus medius and minimus

Answer

Gluteus maximus and minimus

Answer

Gluteus maximus and medius

Answer

Gluteus maximus, medius, and minimus

Question 7

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

Accepted Answer

Plaster of Paris cast

Answer

Internal fixation with plates

Answer

Internal fixation with a nail

Answer

Plaster of Paris slab

Question 8

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

Accepted Answer

1 mm per day

Answer

5 mm per day

Answer

1 cm per week

Answer

5 cm per week

Question 9

What is the maximum weight typically allowed in skeletal traction?

Accepted Answer

20 kg

Answer

5 kg

Answer

10 kg

Answer

30 kg

Question 10

What is the latency period in distraction osteogenesis?

Accepted Answer

4-7 days

Answer

4 weeks

Answer

15 days

Answer

1 month

Orthopaedic Techniques — MCQs

Orthopaedic Techniques — MCQs

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