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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 229 of 326

This practice set contains high-yield board review questions covering key concepts in 3. Adult Reconstruction (Hip & Knee). Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 4561

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old male with a history of hypertension, coronary artery disease, and well-controlled diabetes is scheduled for an elective total hip arthroplasty. His pre-operative blood pressure is 135/80 mmHg. Which of the following pre-operative medications should generally be held on the morning of surgery due to its potential to cause refractory hypotension?

. Metformin
. Amlodipine
. Aspirin
. Valsartan
. Metoprolol

Correct Answer & Explanation

. Valsartan

Explanation

Angiotensin Receptor Blockers (ARBs), such as Valsartan, and ACE inhibitors (like Lisinopril) are generally held on the morning of surgery due to their potential to cause severe and refractory hypotension during anesthesia. Metformin is typically held to prevent lactic acidosis in case of perioperative renal dysfunction. Amlodipine (calcium channel blocker) and Metoprolol (beta-blocker) are usually continued to control hypertension and prevent cardiac events. Aspirin is typically managed based on bleeding risk vs. thrombotic risk, but its primary effect is antiplatelet, not direct anesthetic-related hypotension.

Question 4562

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old male with a history of COPD and hypertension is scheduled for elective total hip arthroplasty. Pre-operatively, his sodium is 132 mEq/L. He takes a thiazide diuretic for hypertension. Which mechanism best explains his mild hyponatremia?

. Increased ADH secretion due to pain
. Syndrome of Inappropriate ADH (SIADH)
. Increased sodium excretion and impaired free water excretion by thiazides
. Cerebral salt wasting
. Primary polydipsia

Correct Answer & Explanation

. Increased sodium excretion and impaired free water excretion by thiazides

Explanation

Thiazide diuretics are a common cause of hyponatremia, particularly in elderly patients. They impair the kidney's ability to excrete free water while simultaneously increasing sodium excretion, leading to a dilutional hyponatremia. The mechanism is partly through inhibition of Na+/Cl- cotransporter in the distal convoluted tubule and partly by increasing ADH sensitivity. The other options are less likely as primary causes in this specific context: SIADH is more common post-operatively or with specific underlying conditions, not typically from chronic thiazide use alone. Cerebral salt wasting is associated with intracranial pathology and hypovolemia. Primary polydipsia would be more extreme and less common in this patient group.

Question 4563

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient is undergoing a total hip arthroplasty. To minimize blood loss, a hypotensive epidural technique is employed, maintaining a mean arterial pressure (MAP) around 60 mmHg. The patient has a history of well-controlled hypertension. What is the primary risk associated with this technique in a patient with chronic hypertension?

. Increased risk of deep vein thrombosis
. Paradoxical increase in cerebral blood flow
. Compromised cerebral autoregulation leading to brain ischemia
. Increased risk of surgical site infection
. Development of post-operative urinary retention

Correct Answer & Explanation

. Compromised cerebral autoregulation leading to brain ischemia

Explanation

Patients with chronic hypertension often have a rightward shift in their cerebral autoregulation curve. This means their brains are accustomed to higher perfusion pressures, and their lower limit of autoregulation (below which cerebral blood flow becomes pressure-dependent) is higher than in normotensive individuals. Maintaining a MAP of 60 mmHg (which might be tolerated by a normotensive patient) can therefore lead to cerebral hypoperfusion and ischemia in a chronically hypertensive patient. DVT, surgical site infection, and urinary retention are general post-operative risks but not directly linked to hypotensive anesthesia's specific neurological risks. Paradoxical increase in cerebral blood flow is incorrect.

Question 4564

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male undergoing a complex revision total knee arthroplasty receives a significant volume of irrigation fluid during the procedure. Post-operatively, he becomes agitated, confused, and his serum sodium drops from 138 mEq/L to 125 mEq/L. What is the most likely cause of his hyponatremia?

. Syndrome of inappropriate antidiuretic hormone (SIADH)
. Transurethral resection of prostate (TURP) syndrome
. Dilutional hyponatremia from absorption of hypotonic irrigation fluid
. Cerebral salt wasting
. Factitious hyponatremia

Correct Answer & Explanation

. Dilutional hyponatremia from absorption of hypotonic irrigation fluid

Explanation

During complex arthroplasty (especially knees, hips, or shoulders with extensive irrigation), absorption of large volumes of hypotonic irrigation fluid (e.g., sterile water, glycine solution, or even dilute saline) can lead to significant dilutional hyponatremia. This phenomenon is analogous to TURP syndrome, which occurs during prostate surgery. The agitation and confusion are neurological symptoms of acute hyponatremia. SIADH is less likely to cause such a rapid and dramatic drop from irrigation. Cerebral salt wasting leads to hypovolemia. Factitious hyponatremia is rare. The direct absorption of hypotonic fluid is the key mechanism here.

Question 4565

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old male with a history of heart failure with reduced ejection fraction (HFrEF) is undergoing a total knee arthroplasty. He is on a beta-blocker and ACE inhibitor. What is the most crucial aspect of intraoperative fluid management for this patient?

. Aggressive crystalloid administration to maintain high urine output
. Fluid restriction to avoid volume overload
. Use of hypertonic saline to draw fluid from interstitial space
. Continuous infusion of colloids to maintain oncotic pressure
. Administration of D5W to prevent hyponatremia

Correct Answer & Explanation

. Fluid restriction to avoid volume overload

Explanation

Patients with HFrEF have a limited ability to tolerate increased intravascular volume. Aggressive fluid administration can quickly lead to pulmonary edema and decompensated heart failure. Therefore, careful fluid restriction and meticulous hemodynamic monitoring are crucial to avoid volume overload. While some fluid is necessary, the goal is euvolemia, not overhydration. Aggressive crystalloid administration is contraindicated. Hypertonic saline or colloids have specific indications and are not general strategies for HFrEF patients. D5W is typically avoided in large volumes as it is hypotonic and can worsen hyponatremia if ADH is elevated.

Question 4566

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old male with chronic hypertension is undergoing a total hip arthroplasty. During the procedure, his blood pressure acutely drops to 70/40 mmHg. Which of the following interventions, if chosen, requires careful consideration of the patient's history of chronic hypertension?

. Administer a bolus of phenylephrine
. Administer a bolus of crystalloid solution
. Increase the oxygen concentration
. Elevate the patient's legs
. Administer atropine for bradycardia

Correct Answer & Explanation

. Administer a bolus of crystalloid solution

Explanation

Patients with chronic hypertension have a rightward shift in their autoregulation curve. While a vasopressor like phenylephrine is often necessary for acute hypotension, careful titration is required. Rapid and excessive vasoconstriction can lead to a sudden and significant increase in afterload, which a chronically hypertensive heart (often with left ventricular hypertrophy) may not tolerate well, potentially leading to myocardial ischemia or even acute heart failure. The goal is to restore adequate perfusion pressure without overshooting or compromising cardiac function. Crystalloid bolus, oxygen, leg elevation, and atropine (if bradycardic) are generally safer interventions for initial management of hypotension in this context, but phenylephrine requires more judicious use.

Question 4567

Topic: 3. Adult Reconstruction (Hip & Knee)

A 75-year-old male undergoes a total hip arthroplasty. On post-operative day 1, his blood pressure is 185/98 mmHg. He is alert and denies any symptoms. What is the primary rationale for treating this asymptomatic hypertension?

. To prevent post-operative delirium
. To reduce the risk of surgical site infection
. To prevent stroke, myocardial infarction, or surgical hematoma
. To improve patient comfort
. To reduce the need for further medication

Correct Answer & Explanation

. To prevent stroke, myocardial infarction, or surgical hematoma

Explanation

Uncontrolled post-operative hypertension, even if asymptomatic, carries significant risks in surgical patients, particularly the elderly. The primary rationale for treatment is to prevent serious complications such as stroke (intracerebral hemorrhage), myocardial infarction (due to increased myocardial oxygen demand), and bleeding at the surgical site (hematoma formation), which can necessitate reoperation or prolong recovery. While it may indirectly affect other outcomes, these cardiovascular and surgical complications are the most direct and serious concerns.

Question 4568

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old male with a baseline serum sodium of 129 mEq/L (due to SIADH) is scheduled for an elective total shoulder arthroplasty. What is the most appropriate pre-operative strategy for his chronic hyponatremia?

. Administer 3% hypertonic saline to normalize sodium before surgery
. Initiate aggressive fluid restriction and consider a V2 receptor antagonist
. Administer 0.9% Normal Saline bolus pre-operatively
. Delay surgery indefinitely until sodium is >135 mEq/L
. No specific treatment needed for mild, chronic hyponatremia

Correct Answer & Explanation

. Initiate aggressive fluid restriction and consider a V2 receptor antagonist

Explanation

For elective surgery, chronic, asymptomatic, mild-to-moderate hyponatremia (e.g., 125-130 mEq/L) should ideally be corrected or significantly improved to minimize perioperative risks. The underlying SIADH should be managed with fluid restriction. A V2 receptor antagonist (vasopressin receptor antagonist like tolvaptan) can be considered to promote free water excretion. Rapid correction with 3% hypertonic saline is reserved for severe, symptomatic hyponatremia. Administering 0.9% Normal Saline to a patient with SIADH can paradoxically worsen hyponatremia due to retention of free water. Delaying surgery indefinitely is often impractical. While mild hyponatremia might sometimes be tolerated, optimizing it pre-operatively is best practice.

Question 4569

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male with a history of essential hypertension (well-controlled on Ramipril) undergoes an elective total knee arthroplasty. On post-operative day 0, his blood pressure drops to 85/45 mmHg. His heart rate is 60 bpm. He is pale and clammy. His pain is well-controlled. What is the most likely cause of his hypotension?

. Acute myocardial infarction
. Sepsis
. Relative hypovolemia due to sympathetic blockade from regional anesthesia
. Allergic reaction to an antibiotic
. Pulmonary embolism

Correct Answer & Explanation

. Relative hypovolemia due to sympathetic blockade from regional anesthesia

Explanation

The patient's presentation with hypotension (85/45 mmHg) and bradycardia (HR 60 bpm) after a total knee arthroplasty, especially with a history of ACE inhibitor use (Ramipril) and often regional anesthesia (spinal or epidural), is highly suggestive of relative hypovolemia due to sympathetic blockade. Regional anesthesia causes vasodilation, which can lead to pooling of blood in the lower extremities and reduced venous return, manifesting as hypotension and often bradycardia. ACE inhibitors can potentiate this effect. Acute MI and PE typically cause tachycardia. Sepsis would involve fever and other signs of infection, and an allergic reaction would have other systemic features like rash or bronchospasm.

Question 4570

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old male undergoes a total knee arthroplasty. On post-operative day 2, his serum sodium is 150 mEq/L. He is confused and has dry mucous membranes. His fluid intake has been limited due to nausea. What is the appropriate management?

. Administer 3% hypertonic saline
. Administer 0.45% Normal Saline at a calculated rate to correct free water deficit
. Restrict fluid intake further
. Administer oral sodium tablets
. Administer a loop diuretic

Correct Answer & Explanation

. Administer 0.45% Normal Saline at a calculated rate to correct free water deficit

Explanation

The patient has hypernatremia (150 mEq/L) with signs of dehydration (dry mucous membranes, confusion). This is indicative of a free water deficit. The most appropriate management is to administer 0.45% Normal Saline (half-normal saline) intravenously. This solution provides free water (as it is hypotonic to plasma) while also contributing some sodium to expand the extracellular volume. The rate should be calculated to correct the deficit gradually (e.g., 10-12 mEq/L/24 hours) to prevent cerebral edema. 3% hypertonic saline would worsen hypernatremia. Further fluid restriction is contraindicated. Oral sodium tablets or loop diuretics are inappropriate.

Question 4571

Topic: 3. Adult Reconstruction (Hip & Knee)

During cementation of a femoral component in a total hip arthroplasty, the patient's blood pressure drops, and there's a transient decrease in oxygen saturation. The anesthesiologist notes a sudden increase in pulmonary artery pressure. What is the underlying pathophysiological mechanism?

. Vasodilation due to anesthetic agents
. Direct myocardial depression from cement constituents
. Microembolization to the pulmonary circulation
. Hypovolemia from surgical bleeding
. Hypervolemia from fluid overload

Correct Answer & Explanation

. Microembolization to the pulmonary circulation

Explanation

This scenario describes Bone Cement Implantation Syndrome (BMIS). The acute increase in pulmonary artery pressure, along with hypotension and desaturation during cementation, is primarily due to microembolization. Microemboli (fat, air, marrow, and possibly cement particles) enter the venous circulation and travel to the lungs, causing pulmonary vascular obstruction and acute pulmonary hypertension. This leads to right ventricular strain, decreased cardiac output, and hypoxemia. While direct myocardial depression from cement constituents and vasodilation are also proposed mechanisms, microembolization to the pulmonary circulation is the central pathophysiological event leading to the acute pulmonary hypertension and subsequent cardiovascular collapse.

Question 4572

Topic: 3. Adult Reconstruction (Hip & Knee)

A 50-year-old male with a history of poorly controlled diabetes and hypertension undergoes an elective total knee arthroplasty. On post-operative day 1, his BP is 190/110 mmHg. He is asymptomatic. What is the most appropriate initial pharmacological treatment?

. Oral Nifedipine extended-release 30 mg
. IV Hydralazine 10 mg
. IV Labetalol 20 mg
. Oral Captopril 25 mg
. IV Furosemide 20 mg

Correct Answer & Explanation

. IV Labetalol 20 mg

Explanation

For acute, severe post-operative hypertension (>180/110 mmHg or symptomatic >160/90 mmHg), intravenous agents are preferred for rapid and titratable control. Labetalol (mixed alpha/beta blocker) is an excellent first-line choice, as it can be given as a bolus and/or infusion to effectively lower blood pressure. Hydralazine is another option but can cause reflex tachycardia. Oral Nifedipine extended-release is for less acute management. Oral Captopril would have a slower onset and greater potential for hypotension. Furosemide is a diuretic and not a primary agent for acute hypertension unless fluid overload is the cause.

Question 4573

Topic: 3. Adult Reconstruction (Hip & Knee)

A 78-year-old male is undergoing an elective total hip arthroplasty. He is on a beta-blocker (Metoprolol) for hypertension. During induction, his blood pressure drops from 140/80 mmHg to 90/50 mmHg. What is the most appropriate initial management of his hypotension?

. Administer IV Epinephrine
. Administer IV Phenylephrine
. Administer IV Atropine
. Increase infusion of Dextrose 5% in Water (D5W)
. Discontinue Metoprolol

Correct Answer & Explanation

. Administer IV Phenylephrine

Explanation

The patient is likely experiencing hypotension due to vasodilation associated with anesthetic induction. In a patient on a beta-blocker, the heart rate may not increase appropriately to compensate for vasodilation. Phenylephrine, a pure alpha-1 adrenergic agonist, is the preferred first-line agent to increase systemic vascular resistance and blood pressure without significantly affecting heart rate (which is already blunted by the beta-blocker). Epinephrine is too potent for initial management unless severe shock. Atropine is for severe bradycardia, not primary hypotension from vasodilation. D5W is not an effective volume expander. Discontinuing Metoprolol acutely is not the immediate solution to acute hypotension and can cause rebound effects.

Question 4574

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old male with a history of COPD is undergoing an elective total knee arthroplasty. On post-operative day 2, he develops dyspnea, hypoxemia, and his serum sodium is 120 mEq/L. His urine osmolality is 250 mOsm/kg. He is clinically euvolemic. What is the most appropriate immediate diagnostic test?

. Thyroid function tests
. Adrenal function tests
. Arterial blood gas (ABG)
. Chest X-ray (CXR)
. Serum cortisol level

Correct Answer & Explanation

. Chest X-ray (CXR)

Explanation

This patient presents with hyponatremia and new-onset dyspnea/hypoxemia. While the hyponatremia itself (with euvolemia and inappropriate urine osmolality) might suggest SIADH or other endocrine causes, the acute respiratory symptoms (dyspnea, hypoxemia) demand immediate investigation of the pulmonary system. A chest X-ray (CXR) is the most appropriate immediate diagnostic test to rule out acute pulmonary edema (a cause of dyspnea and possible hyponatremia if hypervolemic), atelectasis, pneumonia, or pleural effusion, which are common post-operative respiratory complications. Thyroid and adrenal function tests are for the hyponatremia workup but are not the immediate priority for acute respiratory distress. An ABG helps characterize hypoxemia but doesn't provide etiology like a CXR.

Question 4575

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male with a history of peripheral arterial disease (PAD) and hypertension is scheduled for a total hip arthroplasty. His pre-operative blood pressure is 150/85 mmHg. During surgery, what is the most important hemodynamic goal related to his PAD?

. Maintain a high heart rate to increase cardiac output
. Strictly avoid any episodes of hypotension
. Induce mild hypothermia to reduce metabolic demand
. Allow brief periods of systolic blood pressure <80 mmHg to reduce bleeding
. Keep mean arterial pressure (MAP) above 100 mmHg

Correct Answer & Explanation

. Strictly avoid any episodes of hypotension

Explanation

Patients with peripheral arterial disease (PAD) and hypertension have compromised arterial flow and often impaired autoregulation in distal vascular beds. They are particularly susceptible to ischemic complications from hypotension, as their already narrowed arteries cannot adequately compensate for reduced perfusion pressure. Therefore, strictly avoiding any episodes of hypotension is crucial to prevent exacerbation of PAD symptoms, limb ischemia, and other end-organ damage (e.g., renal, cerebral). Maintaining a high heart rate can increase myocardial oxygen demand and is not a primary goal. Hypothermia is not indicated. Allowing brief periods of severe hypotension is dangerous. Keeping MAP above 100 mmHg may be excessively high and risks hypertension complications.

Question 4576

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following is the most sensitive imaging modality for detecting early avascular necrosis (AVN) of the femoral head?

. Plain radiograph (AP pelvis and frog-leg lateral).
. Computed tomography (CT) scan.
. Magnetic resonance imaging (MRI).
. Bone scintigraphy (bone scan).
. Ultrasound.

Correct Answer & Explanation

. Magnetic resonance imaging (MRI).

Explanation

Magnetic resonance imaging (MRI) is the most sensitive and specific imaging modality for detecting early avascular necrosis (AVN) of the femoral head. It can demonstrate changes in bone marrow signal before any changes are visible on plain radiographs or CT scans. Plain radiographs are typically normal in the early stages. CT scans are good for bone detail but less sensitive for early marrow changes. Bone scintigraphy can show areas of decreased uptake, but MRI is superior for specific diagnosis and staging. Ultrasound has no role in diagnosing AVN of the femoral head.

Question 4577

Topic: 3. Adult Reconstruction (Hip & Knee)

In total hip arthroplasty, what is the primary purpose of using highly cross-linked polyethylene?

. To improve initial fixation of the acetabular component.
. To reduce the risk of dislocation.
. To enhance osseointegration of the implant.
. To decrease polyethylene wear and osteolysis.
. To increase the implant's resistance to infection.

Correct Answer & Explanation

. To decrease polyethylene wear and osteolysis.

Explanation

Highly cross-linked polyethylene is primarily used in total hip arthroplasty to significantly reduce polyethylene wear. The cross-linking process modifies the molecular structure of polyethylene, making it more resistant to abrasion and oxidative degradation. This reduction in wear debris is crucial because polyethylene wear particles are the main cause of periprosthetic osteolysis, which can lead to aseptic loosening and the need for revision surgery. It does not directly improve initial fixation, reduce dislocation risk (though larger heads made possible by thinner liners can help), enhance osseointegration, or increase infection resistance.

Question 4578

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following is an absolute contraindication to performing a knee arthroplasty?

. Patient age greater than 80 years.
. Obesity (BMI > 40).
. Active infection in the knee joint.
. Severe osteoporosis.
. History of deep vein thrombosis (DVT).

Correct Answer & Explanation

. Active infection in the knee joint.

Explanation

Active infection in the knee joint is an absolute contraindication to knee arthroplasty. Proceeding with arthroplasty in an infected joint significantly increases the risk of periprosthetic joint infection, which is a devastating complication often requiring multiple surgeries and prolonged antibiotic treatment. Age, obesity, severe osteoporosis, and history of DVT are relative contraindications or risk factors that need to be managed and discussed, but they do not absolutely preclude surgery. Active infection must be eradicated before arthroplasty can be considered.

Question 4579

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following describes a 'stress-shielding' phenomenon in the context of orthopedic implants?

. Increased bone density around a prosthetic implant due to enhanced load transfer.
. Resorption of bone due to reduced mechanical stress in areas protected by a stiff implant.
. The body's immune response to foreign material causing osteolysis.
. The protective effect of soft tissue surrounding an implant preventing fracture.
. Overgrowth of callus around a fracture site due to excessive motion.

Correct Answer & Explanation

. Resorption of bone due to reduced mechanical stress in areas protected by a stiff implant.

Explanation

Stress shielding is the phenomenon where bone resorbs due to a reduction in mechanical stress, as described by Wolff's Law. In the context of orthopedic implants, a stiff implant (e.g., a femoral stem in total hip arthroplasty) can bear a significant portion of the load, 'shielding' the adjacent bone from normal physiological stresses. This leads to a reduction in bone density (osteopenia or bone loss) in the shielded areas, which can potentially weaken the bone and lead to complications like periprosthetic fracture or aseptic loosening. It's distinct from osteolysis due to wear particles or infection.

Question 4580

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following describes a key advantage of dual-mobility articulations in total hip arthroplasty?

. Elimination of wear particle generation.
. Reduced risk of dislocation.
. Improved bone ingrowth to the acetabular component.
. Enhanced pain relief compared to traditional designs.
. Simpler surgical technique.

Correct Answer & Explanation

. Reduced risk of dislocation.

Explanation

Dual-mobility articulations in total hip arthroplasty are designed to reduce the risk of dislocation. They feature a small femoral head articulating within a larger polyethylene liner, which in turn articulates within a polished metal acetabular shell. This 'ball-within-a-ball' design provides a larger jump distance before dislocation, offering greater stability, especially in patients at high risk for dislocation (e.g., those with neuromuscular disorders, revision cases, or previous dislocations). It does not eliminate wear (though wear characteristics can differ), improve bone ingrowth directly, or necessarily provide enhanced pain relief compared to other stable designs. The surgical technique is generally more involved than traditional designs.

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