Basic Science in Orthopaedics Practice Questions

Q: Which of the following diagnostic studies is NOT useful in the evaluation of upper-extremity pain?

Adson's test. **Explanation:** The correct answer is **Adson’s test**. While it is a classic physical examination maneuver used to assess for Thoracic Outlet Syndrome (TOS), it is **not a diagnostic study** (imaging or electrodiagnostic test). Furthermore, in modern clinical practice, Adson’s test is considered unreliable due to a high rate of false positives (up to 25% in healthy individuals), making it "not useful" as a definitive diagnostic tool compared to objective studies. **Analysis of Options:** * **Cervical spine X-ray:** Essential to rule out cervical spondylosis or a herniated disc, which frequently cause referred pain to the upper extremity (cervical radiculopathy). * **Chest X-ray:** Crucial for identifying a **cervical rib** or a **Pancoast tumor** (at the lung apex), both of which can compress the brachial plexus and cause radiating arm pain. * **Neural conduction studies (NCS):** These are objective electrodiagnostic tests used to confirm focal neuropathies, such as Carpal Tunnel Syndrome (median nerve compression), a common cause of upper limb pain. **Clinical Pearls for NEET-PG:** * **Adson’s Test:** Performed by extending the patient's neck and rotating the head toward the affected side while taking a deep breath. A positive result is the disappearance of the radial pulse. * **Thoracic Outlet Syndrome (TOS):** Most commonly caused by a cervical rib (C7) or tight scalene muscles. * **High-Yield Fact:** For upper extremity pain radiating from the neck, the **Spurling test** (foraminal compression) is more specific for cervical radiculopathy than Adson’s is for TOS.

Q: What is the most important factor in fracture healing?

Immobilization. **Explanation:** The primary requirement for fracture healing is **Immobilization**. For a fracture to heal, the "callus" (the bridge of new bone) must form across the gap. Excessive movement at the fracture site creates shear forces that disrupt the delicate capillary ingrowth and the formation of the fibrocartilaginous bridge. If the fracture site is not sufficiently immobilized, the body may form a "non-union" or a "pseudoarthrosis" (false joint) instead of solid bone. **Analysis of Options:** * **A. Good alignment:** While alignment is important for functional recovery and preventing deformity (malunion), a fracture can still heal (unite) even if it is poorly aligned. * **B. Organization of blood clot:** While the hematoma is the first stage of fracture healing and provides a fibrin scaffold, it is not the *most* important factor. Healing can still occur in the absence of a significant clot (e.g., in primary bone healing via internal fixation). * **C. Accurate reduction and 100% apposition:** This is a common misconception. While 100% apposition is ideal, many fractures (like the clavicle or ribs) heal perfectly well with minimal contact or significant displacement, provided they are kept still. **High-Yield Clinical Pearls for NEET-PG:** * **Primary Bone Healing:** Occurs with absolute stability (e.g., compression plating). There is **no callus formation**. * **Secondary Bone Healing:** Occurs with relative stability (e.g., POP cast, intramedullary nailing). This involves the classic stages: Hematoma → Inflammation → Soft Callus → Hard Callus → Remodeling. * **The "Rule of Two":** For adequate immobilization, a cast should generally include the joint above and the joint below the fracture site. * **Most common cause of Non-union:** Inadequate immobilization or poor blood supply.

Q: What is Neurapraxia?

Reversible physiological nerve conduction block. **Explanation:** **Neurapraxia** is the mildest form of nerve injury according to the **Seddon Classification**. It is characterized by a **reversible physiological conduction block** without any anatomical disruption of the axon or its connective tissue coverings (endoneurium, perineurium, or epineurium). 1. **Why Option D is Correct:** The underlying mechanism is typically focal demyelination or local ischemia caused by mild compression or traction. Since the axon remains intact, there is no Wallerian degeneration. Once the pressure is relieved or the myelin is repaired, nerve conduction is fully restored. 2. **Why Other Options are Incorrect:** * **Option A (Complete division):** This describes **Neurotmesis**, the most severe form of injury where the entire nerve trunk is severed. Recovery is impossible without surgical intervention. * **Option B (Axonal interruption):** This describes **Axonotmesis**. Here, the axon is damaged, leading to Wallerian degeneration, but the supporting connective tissue framework remains intact, allowing for guided regeneration. * **Option C (Irreversible injury):** Neurapraxia is inherently **reversible**. Recovery is usually spontaneous and rapid, occurring within days to a few weeks (typically 3–6 weeks). **High-Yield Clinical Pearls for NEET-PG:** * **Wallerian Degeneration:** Absent in Neurapraxia; present in Axonotmesis and Neurotmesis. * **Tinel’s Sign:** Negative in Neurapraxia (as there is no regenerating axonal bud); Positive in Axonotmesis. * **Common Example:** "Saturday Night Palsy" (radial nerve compression) is a classic clinical presentation of neurapraxia. * **EMG/NCV:** In neurapraxia, there is a conduction block at the site of injury, but distal stimulation remains normal.

Q: What is the latent period in distraction osteogenesis?

5-7 days. **Explanation:** **Distraction Osteogenesis** (Ilizarov technique) is a process of growing new bone by mechanically stretching a vascularized callus. The procedure follows a specific chronological sequence: 1. **Latent Period (The Correct Answer):** This is the duration between the corticotomy (surgical bone cut) and the commencement of distraction. It typically lasts **5–7 days**. This period allows for the inflammatory phase of bone healing to occur and for the initial soft tissue/callus bridge to form. Starting distraction too early (before 5 days) can lead to poor callus formation, while starting too late (after 10–14 days) may result in premature consolidation (early fusion). 2. **Distraction Phase:** The bone is stretched at a rate of **1 mm per day**, usually divided into four increments (0.25 mm every 6 hours). 3. **Consolidation Phase:** The period where the newly formed "regenerate" bone mineralizes and hardens. **Analysis of Incorrect Options:** * **A (4-6 weeks):** This is the typical time for clinical union in simple fractures, not the latent period for distraction. * **C & D (6-8 months / 4 months):** These timeframes are more representative of the total duration an Ilizarov fixator might remain on a limb for complex lengthening or non-union treatments. **High-Yield Clinical Pearls for NEET-PG:** * **The Law of Tension-Stress:** Proposed by Ilizarov, stating that gradual traction on living tissues stimulates and maintains the regeneration and growth of those tissues. * **Rate of Distraction:** 1 mm/day is the gold standard. 2 mm/day leads to non-union and nerve damage. * **Most common complication:** Pin tract infection. * **Best site for corticotomy:** Metaphysis (due to superior vascularity and osteogenic potential).

Q: Disruption of the myelin sheath without interruption in the axons is called:

Neuropraxia. ### Explanation This question refers to the **Seddon Classification of Nerve Injury**, which categorizes nerve damage based on the severity of structural disruption. **1. Why Neuropraxia is correct:** Neuropraxia is the mildest form of nerve injury. It is characterized by a **localized conduction block** due to focal demyelination (disruption of the myelin sheath). Crucially, the **axon and the connective tissue sheaths (endoneurium, perineurium, and epineurium) remain intact**. Because the axon is not severed, Wallerian degeneration does not occur, and recovery is typically complete within days to weeks once the myelin repairs. **2. Why the other options are incorrect:** * **Axonotmesis:** This involves the **disruption of the axon** and its myelin sheath, but the supporting connective tissue framework (endoneurium) remains intact. Wallerian degeneration occurs distal to the injury. * **Neurotmesis:** This is the most severe grade, involving **complete transection** of both the axon and all surrounding connective tissue layers. Spontaneous recovery is impossible without surgical intervention. * **Transient ischemia:** While ischemia can cause temporary numbness (e.g., "Saturday Night Palsy"), it is a mechanism of injury rather than a structural classification of nerve damage. **3. High-Yield Clinical Pearls for NEET-PG:** * **Wallerian Degeneration:** Occurs in Axonotmesis and Neurotmesis, but **NOT** in Neuropraxia. * **Recovery Sequence:** Neuropraxia (Fastest/Complete) > Axonotmesis (Slow/Partial) > Neurotmesis (Requires Surgery). * **Tinel’s Sign:** Usually **absent** in Neuropraxia (since the axon is intact) but **present** in Axonotmesis as regenerating axonal sprouts advance. * **Sunderland Classification:** An expansion of Seddon’s; Neuropraxia corresponds to **Grade 1**, Axonotmesis to **Grades 2-4**, and Neurotmesis to **Grade 5**.

Q: Pseudarthrosis may be seen in all of the following conditions except?

Osteomyelitis. **Explanation:** **Pseudarthrosis** (literally "false joint") refers to a permanent failure of bone healing where the fracture site remains mobile, and the medullary canal is sealed by cortical bone, often with a synovial-like membrane forming between the fragments. **Why Osteomyelitis is the correct answer:** Osteomyelitis is an infection of the bone. While chronic osteomyelitis can lead to **Non-union** (specifically infected non-union), it does not typically result in a "Pseudarthrosis." In osteomyelitis, the hallmark pathological features are the **Sequestrum** (dead bone) and **Involucrum** (new bone formation). While the bone may fail to unite, the specific pathological entity of a "false joint" with a fluid-filled cavity is not a characteristic feature of the infection itself. **Analysis of other options:** * **Fracture:** This is the most common cause of acquired pseudarthrosis. If a fracture is inadequately immobilized or has poor blood supply (e.g., scaphoid or neck of femur), the body may form a fibrocartilaginous "false joint" instead of a bony union. * **Idiopathic:** Congenital pseudarthrosis can occur without a known cause, most commonly affecting the tibia in infants. * **Neurofibromatosis (Type 1):** This is a classic association for **Congenital Pseudarthrosis of the Tibia (CPT)**. Approximately 50% of children with CPT have NF-1. It occurs due to a defect in the periosteum, leading to bowing and subsequent fracture that fails to heal. **NEET-PG High-Yield Pearls:** * **Most common site for Congenital Pseudarthrosis:** Distal third of the Tibia. * **Radiological sign of Pseudarthrosis:** Sclerosis of bone ends with closure of the medullary canal (unlike simple non-union where the canal may remain open). * **Treatment:** Usually requires surgical intervention (Ilizarov technique or vascularized fibular graft) as these do not heal spontaneously.

Question 1

A 9-month-old girl is brought by her mother who noticed asymmetric skin folds on the thighs and difficulty abducting the left hip during diaper changes. She was a firstborn, delivered in breech presentation. Examination reveals limited abduction of the left hip to 30 degrees. The pelvis radiograph is shown (Image 1). Which of the following is the most appropriate next step in management?

Accepted Answer

B. Closed reduction under general anaesthesia followed by hip spica casting

Answer

A. Pavlik harness application with ultrasound follow-up at 6 weeks

Answer

C. Open reduction with pelvic osteotomy as primary intervention

Answer

D. Observation and repeat radiograph at 12 months of age

Question 2

A 16-year-old boy presents with a 6-week history of progressively worsening pain and swelling around the right knee. He denies any trauma. On examination there is a firm, tender, warm swelling over the distal femur. Serum alkaline phosphatase is markedly elevated. The plain radiograph is shown in Image 1. Which of the following is the most appropriate next step in management?

Accepted Answer

A. Urgent referral to a sarcoma centre for coordinated biopsy and staging MRI of the limb plus CT chest before definitive treatment

Answer

B. Immediate wide surgical resection without prior tissue diagnosis

Answer

C. Intralesional curettage with bone grafting and adjuvant phenol

Answer

D. En bloc excision with endoprosthetic reconstruction without staging

Question 3

Which of the following diagnostic studies is NOT useful in the evaluation of upper-extremity pain?

Accepted Answer

Adson's test

Answer

Cervical spine x-ray

Answer

Chest X-ray

Answer

Neural conduction studies of the median nerve

Question 4

What is the most important factor in fracture healing?

Accepted Answer

Immobilization

Answer

Good alignment

Answer

Organization of blood clot

Answer

Accurate reduction and 100% apposition of fractured fragments

Question 5

A patient operated for a forearm fracture under general anesthesia with a tourniquet was unable to move his fingers and had sensory loss over the entire hand postoperatively. What is the most common type of nerve injury in this scenario?

Accepted Answer

Neuropraxia

Answer

Axonotmesis

Answer

Neurotmesis

Answer

None of the above

Question 6

What is Neurapraxia?

Accepted Answer

Reversible physiological nerve conduction block

Answer

Complete division of nerve

Answer

Loss of conduction due to axonal interruption

Answer

Irreversible injury

Question 7

Tinel sign is indicative of?

Accepted Answer

Axon degeneration

Answer

Axonal conduction

Answer

Diffuse axonal injury

Answer

Muscle ischemia

Question 8

What is the latent period in distraction osteogenesis?

Accepted Answer

5-7 days

Answer

4-6 weeks

Answer

6-8 months

Answer

4 months

Question 9

Disruption of the myelin sheath without interruption in the axons is called:

Accepted Answer

Neuropraxia

Answer

Axonotmesis

Answer

Neurotmesis

Answer

Transient ischemia

Question 10

Pseudarthrosis may be seen in all of the following conditions except?

Accepted Answer

Osteomyelitis

Answer

Fracture

Answer

Idiopathic

Answer

Neurofibromatosis

Basic Science in Orthopaedics — MCQs

Basic Science in Orthopaedics — MCQs

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