Basic Science in Orthopaedics Practice Questions

Q: "Marble Bone" appearance is seen in:

Osteopetrosis. **Explanation:** **Osteopetrosis** (also known as Albers-Schönberg disease) is the correct answer. The hallmark of this condition is a functional defect in **osteoclasts**, which fail to resorb bone. This leads to an imbalance where bone formation continues but remodeling is absent, resulting in excessively dense, thick, and opaque bones. On X-ray, this manifests as a **"Marble Bone"** appearance because the bones look stark white and lose their normal medullary cavity. Despite the increased density, the bone is structurally weak and brittle, making it prone to "chalk-stick" fractures. **Why the other options are incorrect:** * **Osteomalacia & Rickets:** These are characterized by a defect in mineralization (usually due to Vitamin D deficiency). On X-ray, they show **decreased** bone density (osteopenia) and features like Looser’s zones or fraying/cupping of the metaphysis—the opposite of the "marble" look. * **Osteoporosis:** This involves a decrease in total bone mass with normal mineralization. Radiographically, it presents as increased radiolucency (darker bones) and cortical thinning, not increased density. **NEET-PG High-Yield Pearls:** * **Erlenmeyer Flask Deformity:** Seen in the distal femur due to defective remodeling. * **Bone-within-a-bone appearance:** Another classic radiological sign of osteopetrosis. * **Rugger-Jersey Spine:** Characterized by dense bands at the superior and inferior endplates (also seen in Renal Osteodystrophy). * **Clinical Complication:** Pancytopenia (due to marrow space obliteration) and cranial nerve palsies (due to narrowing of the neural foramina).

Q: Which of the following is NOT a type of healthy bone healing?

Fibrous healing. **Explanation:** In orthopaedics, healthy bone healing is categorized into **Primary (Direct)** and **Secondary (Indirect)** healing. The goal of both is the restoration of bony continuity through mineralized tissue. **Why Fibrous Healing is the correct answer:** **Fibrous healing** (or fibrous union) is considered a form of **impaired healing** or non-union. Instead of forming a bony bridge, the fracture gap is filled with dense fibrous connective tissue. This results in a lack of structural stability and clinical "false motion" at the fracture site. It is not a healthy physiological end-point of bone repair. **Analysis of Incorrect Options:** * **A. Contact Healing:** A type of **Primary Healing**. It occurs when there is absolute stability (compression plating) and the gap is <0.01 mm. Osteoclasts create "cutting cones" that cross the fracture line, followed by osteoblasts laying down lamellar bone immediately. There is no callus formation. * **B. Gap Healing:** Also a type of **Primary Healing**. It occurs when the gap is small (<1 mm) and stable. The gap is first filled by woven bone, which is later remodeled into lamellar bone. Like contact healing, this occurs without external callus. * **C. Healing with Callus Formation:** This is **Secondary Healing**, the most common type of natural bone healing. It occurs in the presence of relative micromotion (e.g., casts, intramedullary nails). It involves a sequential process: Hematoma → Soft Callus (cartilage) → Hard Callus (woven bone) → Remodeling. **NEET-PG High-Yield Pearls:** * **Absolute Stability** (Plating) → Primary Healing → **No Callus.** * **Relative Stability** (Nailing/Casting) → Secondary Healing → **Callus present.** * **Cutting Cones** are the hallmark of primary bone healing. * **Strain Theory (Perren):** Bone formation requires low strain (<2%). If strain is too high, fibrous tissue forms instead of bone.

Q: Short metacarpals are not seen in which of the following conditions?

Down's syndrome. Shortening of the metacarpals (specifically the 4th and 5th) is a distinct clinical sign known as **Archibald’s sign**. This occurs due to premature epiphyseal closure or congenital hypoplasia of the metacarpal bones. ### **Why Down’s Syndrome is the Correct Answer** In **Down’s Syndrome (Trisomy 21)**, the characteristic hand finding is **clinodactyly** (incurving of the 5th finger) due to a hypoplastic or rudimentary **middle phalanx**, not a short metacarpal. Other hand features include a single palmar (simian) crease and a wide gap between the first and second toes (sandal gap). ### **Analysis of Incorrect Options** * **Turner’s Syndrome (45, XO):** This is a classic cause of short 4th metacarpals. When a patient makes a fist, the knuckle of the 4th metacarpal is absent (Archibald’s sign/Positive metacarpal sign). * **Pseudohypoparathyroidism (Albright’s Hereditary Osteodystrophy):** This condition is characterized by end-organ resistance to PTH. It classically presents with short 4th and 5th metacarpals, short stature, and round facies. * **Post-trauma:** Any trauma involving the growth plate (physeal injury) of the metacarpal during childhood can lead to premature fusion and subsequent shortening of the bone. ### **High-Yield Clinical Pearls for NEET-PG** * **Archibald’s Sign:** A positive sign is when a line drawn tangential to the heads of the 4th and 5th metacarpals passes through the head of the 3rd metacarpal (normally it passes distal to it). * **Differential Diagnosis for Short Metacarpals:** 1. Turner’s Syndrome 2. Pseudohypoparathyroidism & Pseudo-pseudohypoparathyroidism 3. Hereditary Multiple Exostosis 4. Post-infective (e.g., Osteomyelitis) or Post-traumatic physeal arrest 5. Homocystinuria

Q: Trauma to a nerve resulting in paresthesia is termed as:

Neuropraxia. This question tests your knowledge of the **Seddon Classification** of nerve injuries, which is a high-yield topic for NEET-PG. ### **Explanation of the Correct Answer** **Neuropraxia** is the mildest form of nerve injury. It involves a physiological block of nerve conduction (usually due to focal ischemia or compression) without any anatomical disruption of the axon or the connective tissue sheath. * **Mechanism:** There is localized demyelination, but the axon remains intact. * **Clinical Presentation:** It manifests as temporary motor weakness or sensory changes like **paresthesia** (numbness/tingling). * **Recovery:** Since there is no Wallerian degeneration, recovery is spontaneous and complete, usually within days to a few weeks. ### **Analysis of Incorrect Options** * **B. Axonotmesis:** This involves the disruption of the **axon**, but the supporting connective tissue (endoneurium, perineurium, and epineurium) remains intact. It leads to Wallerian degeneration distal to the injury. Recovery is possible but slow (1 mm/day) as the axon must regrow. * **C. Neurotmesis:** This is the most severe grade, where the **entire nerve trunk** (axon and all connective tissue sheaths) is completely severed. Spontaneous recovery is impossible; surgical intervention is required. ### **NEET-PG High-Yield Pearls** 1. **Wallerian Degeneration:** Occurs in Axonotmesis and Neurotmesis, but **NOT** in Neuropraxia. 2. **Tinel’s Sign:** It is **absent** in Neuropraxia (because the axon is intact) but becomes **positive** in Axonotmesis as the nerve regenerates. 3. **Sunderland Classification:** An expansion of Seddon’s. * Grade 1 = Neuropraxia * Grade 2 = Axonotmesis * Grade 3-5 = Varying degrees of Neurotmesis (Grade 5 is complete transection). 4. **Common Example:** "Saturday Night Palsy" (Radial nerve compression) is a classic clinical example of Neuropraxia.

Q: Which of the following statements about RANK-Ligand is FALSE?

RANK-L inhibits osteoclasts and inhibits osteoporosis.. ### Explanation **Why Option D is the correct answer:** The statement is false because **RANK-Ligand (RANK-L) is a potent activator of osteoclasts**, not an inhibitor. RANK-L binds to the RANK receptor on osteoclast precursors, leading to their differentiation, activation, and survival. This process increases bone resorption. Therefore, RANK-L **promotes osteoporosis** rather than inhibiting it. **Analysis of other options:** * **Option A:** Correct statement. RANK-L is primarily secreted by **osteoblasts** and marrow stromal cells in response to various stimuli (like PTH), facilitating the "coupling" of bone formation and resorption. * **Option B:** Correct statement. The **RANK receptor** is located on the surface of osteoclast precursors and mature osteoclasts. The RANK-L/RANK interaction is the final common pathway for osteoclastogenesis. * **Option C:** Correct statement. **Denosumab** is a human monoclonal antibody that mimics the action of Osteoprotegerin (OPG). It binds to RANK-L, preventing it from activating the RANK receptor, thereby reducing bone resorption. **High-Yield Clinical Pearls for NEET-PG:** * **Osteoprotegerin (OPG):** This is a "decoy receptor" produced by osteoblasts that binds to RANK-L, preventing it from binding to RANK. It acts as a natural inhibitor of bone resorption. * **The Ratio:** The balance of bone remodeling depends on the **RANK-L/OPG ratio**. An increase in this ratio leads to bone loss (e.g., in postmenopausal osteoporosis or Paget's disease). * **Denosumab Indications:** Used in Osteoporosis, Giant Cell Tumor of Bone (GCT), and bone metastases. * **PTH Action:** Parathyroid hormone stimulates osteoblasts to increase RANK-L expression and decrease OPG expression, indirectly increasing osteoclast activity.

Q: Hoffman Tinel sign is seen in?

Nerve regeneration. **Explanation:** The **Hoffman-Tinel sign** (commonly referred to simply as the Tinel sign) is a clinical indicator of **nerve regeneration**. It is elicited by percussing or tapping over the course of a regenerating nerve. **Why it occurs:** When a peripheral nerve is injured and begins to heal, the regenerating axonal sprouts are "naked" (unmyelinated) and highly sensitive to mechanical stimulation. Tapping over these young axons triggers an electric-shock-like sensation or "pins and needles" (paresthesia) in the distal distribution of the nerve. As regeneration progresses, the point where the sign is elicited moves distally (at a rate of approximately 1 mm/day), allowing clinicians to track the progress of nerve recovery. **Analysis of Incorrect Options:** * **A & C (DVT and Pulmonary Embolism):** These are vascular/thromboembolic conditions. DVT is associated with **Homans' sign** (pain on dorsiflexion of the foot), not Tinel's sign. * **D (Upper Motor Neuron Lesion):** UMN lesions are characterized by spasticity, hyperreflexia, and the **Babinski sign**. The **Hoffmann sign** (flicking the nail of the middle finger causing flexion of the thumb/index finger) is seen in UMN lesions (cervical myelopathy), which is often confused with the Hoffman-Tinel sign due to the similar name. **High-Yield Clinical Pearls for NEET-PG:** * **Rate of Nerve Growth:** Approximately 1 mm per day or 1 inch per month. * **Order of Recovery:** Following a nerve injury, autonomic function returns first, followed by pain, touch, and finally motor function. * **Tinel Sign in Entrapment:** It is also used to diagnose nerve entrapment syndromes, most notably **Carpal Tunnel Syndrome** (tapping over the median nerve at the wrist). * **Prognostic Value:** A "distally advancing" Tinel sign is a positive prognostic indicator of recovery.

Q: Tinel's sign is positive in which of the following conditions?

Peripheral nerve regeneration. **Explanation:** **Tinel’s sign** is a clinical indicator of **peripheral nerve regeneration**. It is elicited by percussing along the course of a damaged nerve. A positive sign is characterized by a "pins and needles" or tingling sensation (paresthesia) felt in the distal distribution of the nerve. 1. **Why Option A is correct:** When a peripheral nerve undergoes regeneration after injury, the newly formed, unmyelinated axonal sprouts are highly sensitive to mechanical stimulation. Tapping over these regenerating fibers triggers an electrical discharge. As the nerve heals, the point where the tingling is elicited moves distally (towards the periphery), allowing clinicians to track the rate of nerve recovery (typically **1 mm/day**). 2. **Why other options are incorrect:** * **Tendon injury & Tenosynovitis:** These involve musculoskeletal structures, not neural tissue. While they cause localized pain or "triggering," they do not produce the distal paresthesia characteristic of Tinel's sign. * **Rheumatoid arthritis:** This is an inflammatory systemic joint disease. While RA can lead to nerve compression (like Carpal Tunnel Syndrome), the sign itself specifically denotes nerve irritability or regeneration, not the underlying arthritic process. **High-Yield Clinical Pearls for NEET-PG:** * **Hoffmann-Tinel Sign:** Another name for Tinel's sign. * **Carpal Tunnel Syndrome (CTS):** A positive Tinel’s sign at the wrist indicates median nerve compression. * **Prognostic Value:** A "distally progressing" Tinel’s sign is a good prognostic indicator of recovery. If the sign remains fixed at the site of injury, it suggests a **neuroma** or lack of regeneration. * **Order of Recovery:** In nerve healing, **Pain** (Sympathetic) recovers first, followed by **Tinel's sign**, then **Touch**, and finally **Motor function**.

Q: What is the most common cause of tendon rupture?

Overuse. **Explanation:** The most common cause of tendon rupture is **overuse**, specifically leading to **tendinosis** (chronic degeneration). While an acute event often triggers the final break, the underlying pathology is usually repetitive microtrauma that exceeds the tendon's reparative capacity. This leads to a breakdown of collagen fibers, mucoid degeneration, and a weakened structural matrix. Spontaneous ruptures rarely occur in healthy tendons; they typically happen in "pre-conditioned" tendons where chronic overuse has compromised tensile strength. **Analysis of Options:** * **A. Overuse (Correct):** Repetitive mechanical loading causes micro-tears and degenerative changes (tendinosis), making the tendon susceptible to rupture even during normal physiological loads. * **B. Trauma:** While acute macrotrauma can cause ruptures, it is statistically less common than rupture secondary to chronic degenerative changes. * **C. Congenital defect:** These are rare causes and usually present as functional deficits or contractures rather than spontaneous ruptures in adulthood. * **D. Fall from height:** This mechanism is more characteristically associated with bony fractures (e.g., calcaneal or vertebral fractures) rather than isolated tendon ruptures. **Clinical Pearls for NEET-PG:** * **Most common site:** The **Achilles tendon** is the most frequently ruptured tendon in the body, typically occurring 2–6 cm proximal to its insertion (the "watershed zone" with poor blood supply). * **Risk Factors:** Fluoroquinolone use (e.g., Ciprofloxacin), local corticosteroid injections, and systemic diseases like Rheumatoid Arthritis or SLE. * **Simmonds/Thompson Test:** The gold standard clinical test for diagnosing Achilles tendon rupture. * **Age Group:** Most common in "weekend warriors" (middle-aged individuals performing intermittent high-intensity exercise).

Question 1

"Marble Bone" appearance is seen in:

Accepted Answer

Osteopetrosis

Answer

Osteomalacia

Answer

Rickets

Answer

Osteoporosis

Question 2

Which of the following is NOT a type of healthy bone healing?

Accepted Answer

Fibrous healing

Answer

Contact healing

Answer

Gap healing

Answer

Healing with callus formation

Question 3

Short metacarpals are not seen in which of the following conditions?

Accepted Answer

Down's syndrome

Answer

Turner's syndrome

Answer

Pseudohypoparathyroidism

Answer

Post-trauma

Question 4

Trauma to a nerve resulting in paresthesia is termed as:

Accepted Answer

Neuropraxia

Answer

Axonotmesis

Answer

Neurotmesis

Answer

None of the above

Question 5

Which of the following statements about RANK-Ligand is FALSE?

Accepted Answer

RANK-L inhibits osteoclasts and inhibits osteoporosis.

Answer

It is secreted from osteoblasts.

Answer

It acts on the RANK receptor present on osteoclasts.

Answer

Denosumab is a monoclonal antibody that inhibits RANK-Ligand.

Question 6

Hoffman Tinel sign is seen in?

Accepted Answer

Nerve regeneration

Answer

Deep Vein Thrombosis

Answer

Pulmonary embolism

Answer

Upper motor neuron lesion

Question 7

The Trendelenburg test is negative in which of the following conditions?

Accepted Answer

Inferior Gluteal nerve palsy

Answer

Polio myelitis

Answer

Superior Gluteal nerve palsy

Answer

Posterior dislocation of the hip

Question 8

Which of the following is not a cause of a positive Trendelenburg sign?

Accepted Answer

Paralysis of the gluteus maximus

Answer

Congenital dislocation of the hip

Answer

Un-united fracture of the femoral neck

Answer

Coxa vara

Question 9

Tinel's sign is positive in which of the following conditions?

Accepted Answer

Peripheral nerve regeneration

Answer

Tendon injury

Answer

Tenosynovitis

Answer

Rheumatoid arthritis

Question 10

What is the most common cause of tendon rupture?

Accepted Answer

Overuse

Answer

Trauma

Answer

Congenital defect

Answer

Fall from height

Basic Science in Orthopaedics — MCQs

Basic Science in Orthopaedics — MCQs

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