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1. General Principles & Basic Science MCQs

Practice Set 637 of 789

This practice set contains high-yield board review questions covering key concepts in 1. General Principles & Basic Science. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 12721

Topic: 1. General Principles & Basic Science

When asked about the latest advancements in a particular orthopedic field (e.g., cartilage repair), what approach would yield the highest marks?

. Dismissing all new techniques as unproven.
. Listing several new techniques without describing their principles or evidence.
. Discussing the principles behind new techniques, citing key evidence (advantages/disadvantages), and explaining their current role and limitations in clinical practice.
. Focusing exclusively on the most expensive new technology.
. Stating that traditional methods are always superior.

Correct Answer & Explanation

. Discussing the principles behind new techniques, citing key evidence (advantages/disadvantages), and explaining their current role and limitations in clinical practice.

Explanation

Examiners expect candidates to be up-to-date with current orthopedic trends. A high-scoring answer would not just list new techniques but would delve into their underlying principles, discuss the supporting evidence (including strengths and weaknesses), and critically evaluate their current place and limitations within the clinical algorithm. This demonstrates critical appraisal and a balanced perspective on innovation.

Question 12722

Topic: Biology, Genetics & Bone Healing

When explaining the pathophysiology of avascular necrosis (AVN) of the femoral head, what component is most critical to articulate for a detailed understanding?

. The exact date of its first description.
. Only listing known risk factors.
. Describing the interruption of blood supply leading to osteocyte death, subsequent subchondral collapse, and eventual secondary osteoarthritis, often linking it to specific risk factors.
. Stating that it causes hip pain.
. Focusing solely on the genetic predisposition.

Correct Answer & Explanation

. Describing the interruption of blood supply leading to osteocyte death, subsequent subchondral collapse, and eventual secondary osteoarthritis, often linking it to specific risk factors.

Explanation

To demonstrate a detailed understanding of AVN, the explanation must go beyond just listing risk factors. It requires describing the core pathophysiological process: the compromised blood supply to the femoral head, leading to osteocyte death, weakening of the subchondral bone, eventual collapse of the articular surface, and progressive osteoarthritis. Linking this process to common risk factors further enhances the explanation and scores highly.

Question 12723

Topic: Infection, Pharmacology & VTE

During a viva, you are asked about complications of anterior cruciate ligament (ACL) reconstruction. Beyond the standard surgical risks, what advanced complication should you proactively mention to demonstrate comprehensive knowledge?

. Bleeding.
. Infection.
. Graft failure/re-rupture, arthrofibrosis, persistent instability, saphenous nerve injury (for patellar tendon graft harvest), and anterior knee pain.
. DVT.
. Numbness around the incision.

Correct Answer & Explanation

. Graft failure/re-rupture, arthrofibrosis, persistent instability, saphenous nerve injury (for patellar tendon graft harvest), and anterior knee pain.

Explanation

While basic surgical complications (infection, bleeding, DVT) are expected, a high-scoring candidate will delve into ACL-specific complications. These include graft failure (re-rupture), arthrofibrosis (stiffness), persistent instability, specific nerve injuries related to graft harvest (e.g., saphenous nerve with patellar tendon or hamstring), and anterior knee pain. Discussing these specific issues demonstrates an in-depth understanding of the procedure's unique challenges.

Question 12724

Topic: 1. General Principles & Basic Science

In an orthopedic exam, when you are asked about the management of a complex regional pain syndrome (CRPS) type I, what aspect of treatment should you emphasize to demonstrate optimal understanding?

. Solely aggressive surgical intervention.
. Prolonged immobilization of the affected limb.
. Early multidisciplinary approach emphasizing physiotherapy, occupational therapy, pain management (pharmacological, interventional), and psychological support, with sympathetic blockade often considered.
. Only prescribing strong opioids for pain relief.
. Ignoring the psychological component of the condition.

Correct Answer & Explanation

. Early multidisciplinary approach emphasizing physiotherapy, occupational therapy, pain management (pharmacological, interventional), and psychological support, with sympathetic blockade often considered.

Explanation

CRPS Type I is a complex, multifactorial condition. A high-scoring answer will emphasize an early, aggressive, and multidisciplinary approach involving physiotherapy (graded motor imagery, desensitization), occupational therapy, pain specialists (pharmacological management, nerve blocks), and psychological support. The focus is on early mobilization and reducing pain to enable function. Ignoring any of these components or recommending aggressive surgery/immobilization would be suboptimal.

Question 12725

Topic: Biology, Genetics & Bone Healing

In a discussion about the management of a stress fracture (e.g., tibia), what is the most critical factor to identify and address for prevention of recurrence and optimal outcomes?

. The specific bone involved.
. Patient's age.
. Identifying and modifying underlying causative factors such as training errors (sudden increase in intensity/duration), nutritional deficiencies (e.g., Vitamin D, calcium), inadequate footwear, or biomechanical abnormalities.
. Only immobilizing the limb.
. Recommending immediate return to high-impact activities after pain subsides.

Correct Answer & Explanation

. Identifying and modifying underlying causative factors such as training errors (sudden increase in intensity/duration), nutritional deficiencies (e.g., Vitamin D, calcium), inadequate footwear, or biomechanical abnormalities.

Explanation

While identifying the stress fracture and providing initial treatment (rest, immobilization) is important, a high-scoring answer will emphasize identifying and modifying the underlying causative factors. These commonly include training errors, nutritional deficits, improper footwear, or biomechanical issues. Addressing these factors is crucial for preventing recurrence and achieving long-term optimal outcomes, demonstrating a comprehensive preventative approach.

Question 12726

Topic: Infection, Pharmacology & VTE

You are discussing the assessment of a child with a limp. What critical 'must-not-miss' diagnosis should you always consider and actively rule out to demonstrate a safe and thorough approach?

. Osgood-Schlatter disease.
. Sever's disease.
. Septic arthritis or osteomyelitis, given their potential for rapid joint destruction or systemic compromise.
. Transient synovitis.
. Flat feet.

Correct Answer & Explanation

. Septic arthritis or osteomyelitis, given their potential for rapid joint destruction or systemic compromise.

Explanation

In a child with a limp, septic arthritis and osteomyelitis are critical 'must-not-miss' diagnoses due to their potential for rapid joint destruction, systemic sepsis, and long-term morbidity if not promptly diagnosed and treated. While other conditions like transient synovitis are more common, demonstrating vigilance for these severe infections showcases a safe and thorough clinical approach, crucial for high exam marks.

Question 12727

Topic: Infection, Pharmacology & VTE

When discussing the importance of post-operative pain management for an orthopedic patient, what key benefit should be highlighted to an examiner, beyond patient comfort?

. It makes the patient like the surgeon more.
. It's a low priority compared to wound care.
. Effective pain management facilitates early mobilization, reduces the risk of complications (e.g., DVT, pneumonia), improves patient satisfaction, and optimizes rehabilitation outcomes.
. It allows the patient to return to work immediately.
. Only strong opioids are effective.

Correct Answer & Explanation

. Effective pain management facilitates early mobilization, reduces the risk of complications (e.g., DVT, pneumonia), improves patient satisfaction, and optimizes rehabilitation outcomes.

Explanation

Effective post-operative pain management is crucial not just for patient comfort but for achieving optimal functional outcomes. A high-scoring answer will articulate how good pain control facilitates early mobilization, which in turn reduces major complications like DVT, pulmonary embolism, and pneumonia, and significantly enhances rehabilitation success. It demonstrates an understanding of the systemic implications of pain and its management.

Question 12728

Topic: Infection, Pharmacology & VTE

A candidate is discussing surgical consent for an elective total knee arthroplasty. The examiner asks, 'How do you ensure truly informed consent, especially regarding less common but significant risks, without unduly alarming the patient?' Which approach is most ethically sound and practically effective?

. List every conceivable complication from a comprehensive checklist, irrespective of individual patient relevance.
. Focus primarily on the most common risks, briefly mentioning others only if the patient specifically asks.
. Discuss common and relevant patient-specific risks in detail, then group less common but serious risks (e.g., DVT/PE, infection, nerve injury) and explain their potential impact, ensuring the patient understands they are rare but possible.
. Have the patient sign a generic consent form and assume they have read and understood the small print.
. Delegate the discussion of all surgical risks to a junior resident to save time.

Correct Answer & Explanation

. Discuss common and relevant patient-specific risks in detail, then group less common but serious risks (e.g., DVT/PE, infection, nerve injury) and explain their potential impact, ensuring the patient understands they are rare but possible.

Explanation

Truly informed consent involves more than just a checklist. It requires a tailored discussion focusing on risks relevant to the specific patient and procedure. Grouping less common but serious risks allows for efficient communication without overwhelming the patient, while still fulfilling ethical and legal obligations. Option A can cause undue anxiety. Option B is inadequate for informed consent. Option D is legally and ethically unsound. Option E is a delegation of a core responsibility and inappropriate.

Question 12729

Topic: Infection, Pharmacology & VTE

In a discussion about the management of osteomyelitis, the examiner asks, 'When considering surgical debridement for chronic osteomyelitis, what is the 'surgical goal' and why is it so critical?'

. The surgical goal is primarily to achieve perfect anatomical reduction of any associated fracture to optimize healing.
. The surgical goal is to remove all devitalized, infected, and foreign material, creating a viable, well-vascularized bed for subsequent bone healing and antibiotic penetration. This is critical because antibiotics alone cannot sterilize necrotic tissue.
. The surgical goal is to simply drain any obvious abscess and apply a local antibiotic bead pouch.
. The surgical goal is to stabilize the bone with external fixation to prevent pathological fracture.
. The surgical goal is to obtain cultures for targeted antibiotic therapy, making extensive debridement unnecessary until results are known.

Correct Answer & Explanation

. The surgical goal is to remove all devitalized, infected, and foreign material, creating a viable, well-vascularized bed for subsequent bone healing and antibiotic penetration. This is critical because antibiotics alone cannot sterilize necrotic tissue.

Explanation

The cornerstone of chronic osteomyelitis management is aggressive surgical debridement. The goal is to remove all non-viable, infected bone and soft tissue, foreign bodies (implants if infected), and any sequestra or involucrum, creating a clean, well-vascularized environment. This is critical because necrotic bone acts as a sanctuary for bacteria, impenetrable to systemic antibiotics and host immune defenses. Antibiotic penetration and immune cell access are only effective in viable tissue. Options A, C, D, and E represent incomplete or incorrect surgical goals for chronic osteomyelitis.

Question 12730

Topic: Infection, Pharmacology & VTE

In a discussion about post-operative rehabilitation following knee surgery, the examiner asks, 'What is the primary rationale for early weight-bearing and mobilization protocols after many lower extremity orthopedic procedures, especially those involving articular cartilage?'

. To prevent deep vein thrombosis (DVT) and pulmonary embolism (PE).
. To accelerate bone healing and consolidate fixation.
. To promote synovial fluid circulation, enhance cartilage nutrition, and prevent joint stiffness and adhesions.
. To reduce patient dependence on caregivers and facilitate early discharge.
. To minimize post-operative pain and reliance on analgesics.

Correct Answer & Explanation

. To promote synovial fluid circulation, enhance cartilage nutrition, and prevent joint stiffness and adhesions.

Explanation

The primary rationale for early weight-bearing and mobilization, particularly after procedures involving articular cartilage (e.g., microfracture, cartilage repair, meniscal repair, even arthroplasty), is to promote chondrocyte health through cyclical loading, enhance synovial fluid circulation for cartilage nutrition, and prevent deleterious effects like joint stiffness, adhesions, and disuse atrophy. While DVT prevention (A) is a benefit, it's not the primary rationale forarticular cartilagehealth. Accelerating bone healing (B) is true for some fractures but not the universal primary reason across all lower extremity procedures involving cartilage. Reducing dependence (D) and pain (E) are secondary benefits.

Question 12731

Topic: 1. General Principles & Basic Science

You are asked about the non-operative management of osteoarthritis of the knee. After outlining initial steps, the examiner asks, 'What is the evidence-based role of intra-articular corticosteroid injections in the long-term management of knee OA?'

. Intra-articular corticosteroids provide significant long-term structural modification and halt cartilage degeneration.
. Intra-articular corticosteroids offer consistent, durable pain relief for many years and should be repeated monthly.
. Intra-articular corticosteroids provide short-to-medium term pain relief (weeks to a few months) and can be useful as an adjunct in a comprehensive management plan, but they do not alter disease progression and should be used judiciously due to potential risks with frequent injections.
. Intra-articular corticosteroids are contraindicated in knee OA due to their catabolic effects on cartilage.
. Intra-articular corticosteroids are primarily used for inflammatory arthritides and have no role in OA.

Correct Answer & Explanation

. Intra-articular corticosteroids provide short-to-medium term pain relief (weeks to a few months) and can be useful as an adjunct in a comprehensive management plan, but they do not alter disease progression and should be used judiciously due to potential risks with frequent injections.

Explanation

Intra-articular corticosteroid injections can provide effective short-to-medium term pain relief (typically weeks to a few months) by reducing inflammation in an osteoarthritic joint. They can be a valuable adjunct in a comprehensive management plan, especially to bridge a patient to other interventions or alleviate acute flares. However, they do not alter the underlying disease progression or provide long-term structural modification. Frequent injections carry risks (e.g., infection, cartilage damage, systemic effects), thus judicious use is recommended. Options A, B, D, and E are incorrect or overstate/understate their role.

Question 12732

Topic: 1. General Principles & Basic Science

In an orthopedic viva, you are discussing a case of suspected septic arthritis of the knee. You correctly identify the need for aspiration. The examiner then asks, 'What is the MOST critical test to send from the aspirated synovial fluid for rapid diagnosis and initial management guidance?'

. Gram stain and urgent cell count with differential.
. Aerobic and anaerobic cultures.
. Glucose and protein levels.
. Lactate dehydrogenase (LDH) level.
. Crystal analysis for gout or pseudogout.

Correct Answer & Explanation

. Gram stain and urgent cell count with differential.

Explanation

While all listed tests can be helpful, the Gram stain and urgent cell count with differential are the MOST critical for rapid diagnosis and initial management guidance in suspected septic arthritis. The cell count (specifically polymorphonuclear cell count) helps confirm inflammation and likelihood of infection, while the Gram stain can rapidly identify the causative organism (Gram-positive cocci vs. Gram-negative rods), allowing for initiation of appropriate empiric antibiotic therapy before culture results are available. Cultures (B) are essential for definitive diagnosis and sensitivity, but take longer. Glucose/protein (C) and LDH (D) are less specific. Crystal analysis (E) is important to rule out inflammatory arthropathy, but septic arthritis remains the priority until ruled out.

Question 12733

Topic: Infection, Pharmacology & VTE

You are asked to describe the initial management of a suspected acute deep vein thrombosis (DVT) in a post-operative orthopedic patient. The examiner focuses on diagnostics. What is the MOST appropriate first-line diagnostic investigation?

. MRI venography of the affected limb.
. Computed tomography pulmonary angiogram (CTPA) to rule out pulmonary embolism.
. Doppler ultrasound of the affected limb.
. D-dimer blood test, followed by ultrasound only if D-dimer is elevated.
. Ascending venography as the gold standard.

Correct Answer & Explanation

. Doppler ultrasound of the affected limb.

Explanation

The most appropriate first-line diagnostic investigation for suspected acute DVT is a Doppler ultrasound of the affected limb. It is non-invasive, widely available, and highly sensitive and specific for proximal DVT. While a D-dimer test (D) can be used torule outDVT in low-probability patients, it is not sufficiently specific in post-operative orthopedic patients (who often have elevated D-dimer due to surgery itself) to be themost appropriate first-line diagnosticwhen DVT is suspected. CTPA (B) is for suspected PE. MRI venography (A) and ascending venography (E) are more invasive or costly and typically reserved for complex cases or when ultrasound is inconclusive.

Question 12734

Topic: Infection, Pharmacology & VTE

You are discussing the non-operative management of a stable intertrochanteric hip fracture in a very frail, non-ambulatory patient. The examiner asks, 'What is the MOST critical aspect of their management plan to prevent significant morbidity and mortality?'

. Strict bed rest to prevent any weight-bearing on the affected hip.
. Aggressive pain management, early mobilization out of bed to a chair, pressure ulcer prevention, and nutritional support.
. Immediate placement in a spica cast to immobilize the fracture.
. Long-term antibiotic prophylaxis to prevent infection.
. Minimizing all movement to promote fracture healing.

Correct Answer & Explanation

. Aggressive pain management, early mobilization out of bed to a chair, pressure ulcer prevention, and nutritional support.

Explanation

For a very frail, non-ambulatory patient with a stable intertrochanteric hip fracture managed non-operatively, the MOST critical aspect is to focus on comfort and preventing the devastating complications of immobility. This includes aggressive pain management to facilitate movement, early mobilization out of bed to a chair (even if not weight-bearing on the limb), meticulous skin care for pressure ulcer prevention, and adequate nutritional support. Strict bed rest (A, E) significantly increases the risk of pneumonia, DVT/PE, pressure ulcers, and functional decline. Spica cast (C) is inappropriate for intertrochanteric fractures in this demographic. Antibiotic prophylaxis (D) is not indicated.

Question 12735

Topic: 1. General Principles & Basic Science

In a viva, you are asked about the ethical considerations in treating a Jehovah's Witness patient who requires urgent surgical intervention for a major orthopedic trauma but refuses blood transfusion. How would you proceed?

. Refuse to operate due to the high risk of mortality without transfusion.
. Proceed with surgery and transfuse blood if clinically necessary, overriding the patient's wishes for life-saving treatment.
. Respect the patient's autonomy and religious beliefs. Explore all blood conservation strategies (e.g., cell salvage, synthetic blood products, tranexamic acid, permissive hypotension) with the patient and involve an ethics committee if time permits, while making it clear the risks of non-transfusion.
. Delay surgery until the patient or their family consents to transfusion.
. Transfer the patient to another facility that specializes in treating Jehovah's Witnesses.

Correct Answer & Explanation

. Respect the patient's autonomy and religious beliefs. Explore all blood conservation strategies (e.g., cell salvage, synthetic blood products, tranexamic acid, permissive hypotension) with the patient and involve an ethics committee if time permits, while making it clear the risks of non-transfusion.

Explanation

This is a common and critical ethical scenario. The most appropriate approach is to respect the patient's autonomy and religious beliefs while providing the best possible care within those constraints. This involves a thorough discussion with the patient about the risks, exploring all blood conservation strategies, and involving an ethics committee for guidance if the situation allows. Overriding patient wishes (B) is ethically problematic, and refusing to operate (A) or delaying surgery (D) can lead to worse outcomes. Transferring (E) might be an option if specialist facilities exist, but the initial local management should follow option C.

Question 12736

Topic: Biology, Genetics & Bone Healing

In a viva, the examiner observes you are using jargon. They interrupt and ask, 'If you were explaining 'avascular necrosis of the femoral head' to an educated but non-medical patient and their family, how would you describe it simply but accurately?'

. It's when the blood supply to the top of your thigh bone (femoral head) gets interrupted, causing the bone cells to die. This can lead to the bone collapsing and severe arthritis.
. It's a rare bone infection that affects the hip joint and needs strong antibiotics.
. It's similar to osteoporosis, where the bone becomes weak and brittle, leading to fractures.
. It's a fancy term for early-onset osteoarthritis of the hip.
. It means the femoral head is slowly dissolving due to an autoimmune condition.

Correct Answer & Explanation

. It's when the blood supply to the top of your thigh bone (femoral head) gets interrupted, causing the bone cells to die. This can lead to the bone collapsing and severe arthritis.

Explanation

Effective communication with patients involves using clear, understandable language. Option A accurately describes avascular necrosis by explaining the core pathology (interrupted blood supply, bone cell death) and its consequence (bone collapse, arthritis) in simple terms. Options B, C, D, and E are inaccurate or misleading explanations for a non-medical audience, confusing AVN with infection, osteoporosis, osteoarthritis, or autoimmune conditions.

Question 12737

Topic: Surgical Anatomy & Approaches

In a viva, you've explained your reasoning for using a particular surgical approach. The examiner challenges, 'But why would you choose that approach when XYZ approach has a demonstrably lower infection rate in some series?' What is the BEST way to respond to this challenge?

. Admit that you might be wrong and retract your initial choice.
. Defensively state that your chosen approach is what you were taught and are most comfortable with.
. Acknowledge the examiner's point about infection rates, then articulate specific patient-related factors, anatomical considerations, or biomechanical advantages that, inthis specific case, led you to favor your chosen approach, while briefly addressing how you mitigate the stated risk.
. Change the topic to another aspect of the case, avoiding the direct challenge.
. State that your institution's data shows no difference in infection rates, without further elaboration.

Correct Answer & Explanation

. Acknowledge the examiner's point about infection rates, then articulate specific patient-related factors, anatomical considerations, or biomechanical advantages that, inthis specific case, led you to favor your chosen approach, while briefly addressing how you mitigate the stated risk.

Explanation

When challenged, a confident and knowledgeable candidate acknowledges the validity of the examiner's point (if appropriate) but then provides a reasoned, case-specific justification for their decision. This demonstrates critical thinking, awareness of controversies, and the ability to apply evidence to individual patients. Avoiding defensiveness (B) or immediate retraction (A) is crucial. Changing the topic (D) is a significant viva error. Simply quoting institutional data (E) without explanation is insufficient.

Question 12738

Topic: 1. General Principles & Basic Science

In a viva, an examiner states, 'You've just explained the indications for surgical intervention. Now, tell me, how do you manage a patient who, despite meeting all your surgical indications, steadfastly refuses surgery?'

. Inform the patient that they are making a poor decision and refuse to continue care.
. Document the refusal, re-educate the patient on the risks of non-operative management and benefits of surgery, explore their reasons for refusal, offer alternatives (e.g., second opinion), continue to offer conservative management if appropriate, and maintain an open dialogue for future reconsideration.
. Immediately refer them to another surgeon who might convince them.
. Discharge them from your care, as they are not compliant.
. Force the issue by emphasizing the negative consequences without further discussion.

Correct Answer & Explanation

. Document the refusal, re-educate the patient on the risks of non-operative management and benefits of surgery, explore their reasons for refusal, offer alternatives (e.g., second opinion), continue to offer conservative management if appropriate, and maintain an open dialogue for future reconsideration.

Explanation

Patient autonomy is a fundamental ethical principle. When a patient refuses indicated surgery, even if it seems suboptimal, the appropriate response is to respect their decision. This involves thorough documentation, re-education on risks/benefits in a non-coercive manner, actively listening to understand their concerns, offering alternatives like a second opinion, and continuing to provide appropriate conservative care while maintaining an open-door policy for future discussions. Refusing care (A, D), forcing the issue (E), or immediate referral (C) are inappropriate and breach ethical principles.

Question 12739

Topic: 1. General Principles & Basic Science

In a viva, an examiner challenges your initial diagnosis, stating, 'Are you absolutely sure about that diagnosis? Have you considered alternative explanations for the patient's symptoms?' What is the MOST appropriate response?

. Become defensive and reiterate your diagnosis with increasing conviction.
. Admit uncertainty and state you need more time to think, without offering alternatives.
. Acknowledge the examiner's valid point, briefly state the differential diagnoses you considered (or would consider), and explain why you favored your primary diagnosis based on the available information, demonstrating critical thinking and a structured approach.
. Change your diagnosis immediately to appease the examiner.
. Ask the examiner what diagnosis they think is more likely.

Correct Answer & Explanation

. Acknowledge the examiner's valid point, briefly state the differential diagnoses you considered (or would consider), and explain why you favored your primary diagnosis based on the available information, demonstrating critical thinking and a structured approach.

Explanation

This is a common viva technique to test confidence and critical thinking. The most appropriate response is to acknowledge the examiner's point, demonstrate that you have considered (or are capable of considering) a differential diagnosis, and then justify your primary diagnosis based on the clinical evidence. This shows a structured approach to problem-solving and the ability to critically evaluate information, rather than being rigid, defensive, or easily swayed. Changing your diagnosis immediately (D) or asking the examiner for their opinion (E) shows a lack of confidence and independent thought.

Question 12740

Topic: Biology, Genetics & Bone Healing

You are asked about the management of a non-union of the tibia. The examiner asks, 'What is the fundamental biological principle underlying successful treatment of a hypertrophic non-union versus an atrophic non-union?'

. Hypertrophic non-union requires biological stimulation (e.g., bone grafting), while atrophic non-union requires only mechanical stability.
. Atrophic non-union requires aggressive debridement to remove excess callus, while hypertrophic non-union requires minimal intervention.
. Hypertrophic non-union indicates adequate biological response but insufficient mechanical stability, thus requiring robust fixation. Atrophic non-union indicates poor biological potential, requiring both mechanical stability and biological stimulation (e.g., bone grafting or growth factors).
. Both hypertrophic and atrophic non-unions require the same treatment: external fixation with bone transport.
. Hypertrophic non-union requires antibiotics, while atrophic non-union requires vascularized free flap.

Correct Answer & Explanation

. Hypertrophic non-union indicates adequate biological response but insufficient mechanical stability, thus requiring robust fixation. Atrophic non-union indicates poor biological potential, requiring both mechanical stability and biological stimulation (e.g., bone grafting or growth factors).

Explanation

The fundamental difference in treating non-unions lies in their biological activity. A hypertrophic non-union demonstrates a robust biological response (visible callus formation) but lacks sufficient mechanical stability (e.g., due to inadequate fixation or excessive motion at the fracture site). Treatment focuses on achieving rigid mechanical stability. An atrophic non-union, however, lacks both biological potential (no visible callus, often 'elephant's foot' or 'horse's hoof' appearance) and stability, often due to devascularization or infection. Treatment requires both mechanical stability and biological stimulation (e.g., bone grafting, debridement, growth factors). Options A, B, D, and E either reverse the principles, oversimplify, or suggest incorrect generalized treatments.

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