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1. General Principles & Basic Science MCQs

Practice Set 325 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 6481

Topic: 1. General Principles & Basic Science

In a patient presenting with an obturator-type anterior hip dislocation, what is the classic resting position of the affected lower extremity?

. Flexed, internally rotated, and adducted
. Extended, internally rotated, and abducted
. Flexed, externally rotated, and abducted
. Extended, externally rotated, and adducted
. Flexed, neutral rotation, and adducted

Correct Answer & Explanation

. Flexed, internally rotated, and adducted

Explanation

Anterior hip dislocations present with the hip externally rotated and abducted. If it is an inferior (obturator) anterior dislocation, the hip will be fixed in significant flexion, whereas a superior (pubic) anterior dislocation presents with the hip in extension.

Question 6482

Topic: Biology, Genetics & Bone Healing

A 68-year-old woman with a 10-year history of daily alendronate use presents with progressive, severe right thigh pain with weight-bearing. Radiographs demonstrate focal lateral cortical thickening (beaking) and a transverse radiolucent line involving 60% of the lateral cortex in the subtrochanteric region. What is the most appropriate management?

. Discontinue alendronate and observe with protected weight-bearing
. Core decompression of the proximal femur
. Prophylactic cephalomedullary nailing of the right femur
. Sliding hip screw fixation
. Prescribe teriparatide and restrict weight-bearing indefinitely

Correct Answer & Explanation

. Discontinue alendronate and observe with protected weight-bearing

Explanation

This patient has a symptomatic, incomplete atypical femur fracture due to prolonged bisphosphonate use. Because she has prodromal pain and the radiolucency involves a significant portion of the cortex, prophylactic intramedullary nailing is indicated to prevent completion of the fracture.

Question 6483

Topic: 1. General Principles & Basic Science

An 82-year-old woman with osteoporosis sustains a displaced femoral neck fracture. The surgeon elects to perform a hemiarthroplasty. Compared to an uncemented stem, what is a well-documented advantage of using a cemented femoral stem in this patient?

. Lower intraoperative mortality risk due to bone cement implantation syndrome
. Lower risk of postoperative periprosthetic fracture
. Shorter total operative time
. Reduced intraoperative blood loss
. Lower risk of postoperative deep vein thrombosis

Correct Answer & Explanation

. Lower intraoperative mortality risk due to bone cement implantation syndrome

Explanation

In elderly patients with osteoporosis, cemented hemiarthroplasty significantly reduces the risk of postoperative periprosthetic femoral fractures compared to uncemented stems. However, cemented stems carry a small risk of bone cement implantation syndrome (BCIS), which can increase perioperative mortality.

Question 6484

Topic: 1. General Principles & Basic Science

A 24-year-old man is brought to the OR with an irreducible posterior hip dislocation after closed reduction attempts in the emergency department and under general anesthesia fail. What is the most common anatomic structure preventing closed reduction in this scenario?

. Incarcerated piriformis tendon
. Buttonholing of the femoral head through the capsule
. Interposition of the ligamentum teres
. Avulsed anterosuperior labrum
. Massive osteochondral loose body from the acetabular dome

Correct Answer & Explanation

. Incarcerated piriformis tendon

Explanation

The most common block to closed reduction of a posterior hip dislocation is the buttonholing of the femoral head through a rent in the posterior hip capsule. Other potential but less common blocks include the piriformis tendon, obturator internus, or osteochondral fragments.

Question 6485

Topic: 1. General Principles & Basic Science

A 22-year-old skier crashes and sustains an inferior anterior hip dislocation. On physical examination in the emergency department, his affected lower extremity is classically positioned in:

. Flexion, adduction, and internal rotation
. Extension, adduction, and internal rotation
. Flexion, abduction, and external rotation
. Extension, abduction, and external rotation
. Flexion, abduction, and internal rotation

Correct Answer & Explanation

. Flexion, adduction, and internal rotation

Explanation

Anterior hip dislocations present with the affected limb abducted and externally rotated. Inferior anterior (obturator) dislocations present with concurrent hip flexion, whereas superior anterior (pubic) dislocations present with hip extension.

Question 6486

Topic: Biology, Genetics & Bone Healing

A 68-year-old woman on long-term bisphosphonate therapy presents with weeks of vague anterior thigh pain, followed by an acute inability to bear weight. Radiographs show a transverse subtrochanteric fracture with lateral cortical thickening. What is the underlying mechanism of this atypical fracture?

. Overactivation of osteoclasts leading to focal osteolysis
. Severe vitamin D deficiency impairing mineralization
. Suppression of targeted bone remodeling and accumulation of microdamage
. Reduced osteoblast differentiation from marrow stromal cells
. Increased inflammatory cytokines promoting rapid bone turnover

Correct Answer & Explanation

. Overactivation of osteoclasts leading to focal osteolysis

Explanation

Long-term bisphosphonate use heavily suppresses osteoclast-mediated targeted bone remodeling. This suppression prevents the repair of physiologic wear and tear, leading to an accumulation of microdamage, brittle bone, and atypical subtrochanteric or diaphyseal fractures.

Question 6487

Topic: Biomechanics & Biomaterials

During the cementation and pressurization phase of a cemented hemiarthroplasty for a femoral neck fracture, the patient's blood pressure drops acutely to 70/40 mmHg, accompanied by severe hypoxia. What is the primary pathophysiologic mechanism of this event?

. Anaphylactic reaction to polymethylmethacrylate (PMMA)
. Acute hypovolemic shock secondary to unrecognized intraoperative bleeding
. Embolization of marrow contents and fat during cement pressurization
. Toxic systemic reaction to unpolymerized liquid monomer
. Myocardial infarction triggered by surgical stress

Correct Answer & Explanation

. Anaphylactic reaction to polymethylmethacrylate (PMMA)

Explanation

Bone cement implantation syndrome (BCIS) presents with hypoxia, hypotension, and arrhythmias during cementation. It is primarily caused by the embolization of marrow, fat, and air into the pulmonary venous circulation during medullary pressurization.

Question 6488

Topic: Biomechanics & Biomaterials

During the insertion of cemented hemiarthroplasty for a femoral neck fracture, the patient's blood pressure drops acutely and oxygen saturation falls. Bone cement implantation syndrome (BCIS) is suspected. The primary hemodynamic derangement in severe BCIS is characterized by:

. Left ventricular failure secondary to severe systemic hypertension
. Right ventricular failure and acute pulmonary hypertension
. Acute hypovolemic shock from vasodilation
. Anaphylactic shock mediated by IgE
. Pulmonary venous hypertension

Correct Answer & Explanation

. Left ventricular failure secondary to severe systemic hypertension

Explanation

BCIS is triggered by the embolization of marrow fat and debris during cement pressurization, leading to acute pulmonary hypertension, hypoxia, right ventricular strain, and subsequent right heart failure with hypotension.

Question 6489

Topic: Surgical Anatomy & Approaches

When performing a total hip arthroplasty via the direct anterior approach, the internervous plane utilized is between muscles innervated by which of the following nerves?

. Superior gluteal nerve and femoral nerve
. Superior gluteal nerve and inferior gluteal nerve
. Femoral nerve and obturator nerve
. Sciatic nerve and superior gluteal nerve
. Obturator nerve and inferior gluteal nerve

Correct Answer & Explanation

. Superior gluteal nerve and femoral nerve

Explanation

The direct anterior approach exploits the internervous plane between the tensor fasciae latae (superior gluteal nerve) and the sartorius/rectus femoris (femoral nerve). This allows exposure of the hip joint without detaching muscle insertions.

Question 6490

Topic: Biomechanics & Biomaterials

A 68-year-old man undergoes a cemented unipolar hemiarthroplasty for a displaced femoral neck fracture. During cement pressurization and stem insertion, the patient experiences sudden profound hypotension and hypoxia. What is the primary pathophysiologic mechanism of this complication?

. Fat and marrow embolization to the pulmonary vasculature
. Anaphylactic reaction to polymethylmethacrylate (PMMA)
. Acute myocardial infarction secondary to hypovolemia
. Thermal necrosis of the femoral canal leading to bleeding
. Vagal reflex from endosteal stretch

Correct Answer & Explanation

. Fat and marrow embolization to the pulmonary vasculature

Explanation

Bone cement implantation syndrome (BCIS) is primarily caused by the embolization of fat, marrow, and air into the pulmonary circulation during cement pressurization. It presents with hypoxia, hypotension, and potentially cardiac arrest.

Question 6491

Topic: Surgical Anatomy & Approaches

During a direct anterior approach for total hip arthroplasty, the internervous plane is developed between muscles supplied by which of the following nerves?

. Superior gluteal and femoral nerves
. Inferior gluteal and superior gluteal nerves
. Femoral and obturator nerves
. Femoral and sciatic nerves
. Superior gluteal and obturator nerves

Correct Answer & Explanation

. Superior gluteal and femoral nerves

Explanation

The direct anterior approach (Smith-Petersen) utilizes the true internervous plane between the tensor fasciae latae (innervated by the superior gluteal nerve) and the sartorius and rectus femoris (innervated by the femoral nerve).

Question 6492

Topic: 1. General Principles & Basic Science

A 75-year-old nursing home resident sustains a displaced femoral neck fracture. A cemented bipolar hemiarthroplasty is planned. During cement pressurization, the patient's blood pressure drops precipitously and end-tidal CO2 decreases. Which of the following is the most important prophylactic measure to prevent this?

. Administration of prophylactic antibiotics 1 hour prior to incision
. Venting of the femoral canal and thorough pulsatile lavage prior to cementation
. Using a tourniquet during the procedure
. Decreasing the cement mixing time
. Inserting the cement in an early, liquid state

Correct Answer & Explanation

. Administration of prophylactic antibiotics 1 hour prior to incision

Explanation

Bone cement implantation syndrome (BCIS) is characterized by hypoxia, hypotension, and cardiovascular collapse. Thorough lavage and venting of the femoral canal reduce intramedullary pressure and the risk of marrow embolization.

Question 6493

Topic: Surgical Anatomy & Approaches

During a direct anterior approach to the hip for total hip arthroplasty, the ascending branch of the lateral femoral circumflex artery is typically ligated. In what intermuscular interval is this approach performed?

. Tensor fasciae latae and sartorius
. Gluteus medius and tensor fasciae latae
. Rectus femoris and vastus lateralis
. Sartorius and rectus femoris
. Gluteus maximus and medius

Correct Answer & Explanation

. Tensor fasciae latae and sartorius

Explanation

The direct anterior approach (Smith-Petersen interval) utilizes the true internervous plane between the tensor fasciae latae (superior gluteal nerve) and the sartorius (femoral nerve). The ascending branch of the lateral femoral circumflex artery crosses this interval and must be ligated for exposure.

Question 6494

Topic: Biomechanics & Biomaterials

An 81-year-old woman with a displaced femoral neck fracture is undergoing a cemented bipolar hemiarthroplasty. During the pressurization of the cement and insertion of the femoral stem, she experiences sudden hypoxia, hypotension, and right heart failure. What is the primary pathophysiologic mechanism of this complication?

. Anaphylactic reaction to polymethylmethacrylate
. Embolization of marrow fat and surgical debris
. Exothermic thermal necrosis of the endosteum
. Vagal reflex from femoral canal distension
. Hemorrhagic shock from unnoticed vessel injury

Correct Answer & Explanation

. Anaphylactic reaction to polymethylmethacrylate

Explanation

Bone cement implantation syndrome (BCIS) is characterized by hypoxia and hypotension during cementation. It is primarily caused by the embolization of marrow fat, air, and bone debris into the pulmonary circulation due to high intramedullary pressures during cement pressurization and stem insertion.

Question 6495

Topic: Surgical Anatomy & Approaches

Which of the following nerves is at greatest risk of injury during a direct lateral (Hardinge) approach to the hip?

. Sciatic nerve
. Femoral nerve
. Superior gluteal nerve
. Inferior gluteal nerve
. Lateral femoral cutaneous nerve

Correct Answer & Explanation

. Sciatic nerve

Explanation

The superior gluteal nerve innervates the gluteus medius, minimus, and tensor fasciae latae. Proximal splitting of the gluteus medius during the direct lateral approach beyond 3 to 5 cm from the greater trochanter places this nerve at significant risk for denervation.

Question 6496

Topic: Infection, Pharmacology & VTE

According to the AAOS clinical practice guidelines on venous thromboembolic disease prophylaxis after elective total hip arthroplasty, which of the following regimens is recommended for patients with standard risk profiles?

. Aspirin alone
. Low molecular weight heparin (LMWH) for 14 days
. Warfarin with an INR goal of 2.5 to 3.5
. Aspirin combined with mechanical compression devices
. Unfractionated heparin for 5 days

Correct Answer & Explanation

. Aspirin alone

Explanation

Current AAOS guidelines support the use of pharmacologic agents, such as aspirin, combined with mechanical compressive devices for VTE prophylaxis in standard-risk patients undergoing elective THA. This balances efficacy in preventing DVT/PE with a lower risk of bleeding complications.

Question 6497

Topic: Surgical Anatomy & Approaches

During a direct anterior approach for a total hip arthroplasty, the surgeon dissects between the tensor fasciae latae and the sartorius. Which of the following nerves is at greatest risk of injury during this superficial dissection?

. Femoral nerve
. Sciatic nerve
. Lateral femoral cutaneous nerve
. Superior gluteal nerve
. Obturator nerve

Correct Answer & Explanation

. Femoral nerve

Explanation

The lateral femoral cutaneous nerve courses anteriorly over the sartorius and is at significant risk of injury during the superficial internervous plane of the direct anterior approach (Smith-Petersen). Injury can lead to meralgia paresthetica.

Question 6498

Topic: 1. General Principles & Basic Science

An 80-year-old woman with a history of severe osteoporosis undergoes a cemented total hip arthroplasty. During cement pressurization and stem insertion, her blood pressure drops precipitously. What is the primary pathophysiologic mechanism for bone cement implantation syndrome (BCIS)?

. Anaphylaxis to polymethylmethacrylate (PMMA) monomer
. Acute myocardial infarction from blood loss
. Fat and marrow embolization to the lungs
. Hypovolemic shock secondary to vasodilation
. Parasympathetic overdrive

Correct Answer & Explanation

. Anaphylaxis to polymethylmethacrylate (PMMA) monomer

Explanation

Bone cement implantation syndrome is primarily caused by fat, marrow, and air embolization to the pulmonary circulation during intramedullary pressurization. This shower of emboli leads to increased pulmonary vascular resistance and subsequent right ventricular failure.

Question 6499

Topic: Infection, Pharmacology & VTE

A 65-year-old man is scheduled for primary total hip arthroplasty. He is healthy with no history of prior DVT, pulmonary embolism, or bleeding disorders. According to the latest AAOS guidelines, what is the most appropriate routine venous thromboembolism (VTE) prophylaxis postoperatively?

. Aspirin
. Warfarin
. Low-molecular-weight heparin (LMWH)
. Unfractionated heparin
. Mechanical compression alone

Correct Answer & Explanation

. Aspirin

Explanation

Recent AAOS guidelines and consensus statements support the use of Aspirin for routine VTE prophylaxis in standard-risk patients undergoing elective total joint arthroplasty. It is highly effective and significantly reduces the risk of major bleeding compared to stronger anticoagulants.

Question 6500

Topic: Surgical Anatomy & Approaches

In a direct anterior approach for total hip arthroplasty, the superficial internervous plane is utilized. Which two nerves supply the muscles defining this plane?

. Superior gluteal nerve and inferior gluteal nerve
. Femoral nerve and obturator nerve
. Femoral nerve and superior gluteal nerve
. Sciatic nerve and femoral nerve
. Femoral nerve and lateral femoral cutaneous nerve

Correct Answer & Explanation

. Superior gluteal nerve and inferior gluteal nerve

Explanation

The direct anterior (Smith-Petersen) approach exploits the internervous plane between the sartorius (femoral nerve) and the tensor fasciae latae (superior gluteal nerve).

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