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1. General Principles & Basic Science MCQs

Practice Set 566 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 11301

Topic: Surgical Anatomy & Approaches

A 50-year-old male is undergoing open reduction and internal fixation of an anterior column acetabular fracture via the ilioinguinal approach.

During dissection over the superior pubic ramus, the surgeon encounters significant bleeding. Which of the following vascular anastomoses (often termed the 'Corona Mortis') is classically located in this region and at risk of iatrogenic injury?

. Anastomosis between the external iliac and internal iliac vascular systems
. Anastomosis between the femoral and obturator arteries
. Anastomosis between the superior gluteal and inferior gluteal arteries
. Anastomosis between the deep circumflex iliac and inferior epigastric arteries
. Anastomosis between the pudendal and obturator arteries

Correct Answer & Explanation

. Anastomosis between the external iliac and internal iliac vascular systems

Explanation

The Corona Mortis ('crown of death') is a vascular anastomosis between the obturator vessels (which are part of the internal iliac system) and the external iliac or inferior epigastric vessels. It crosses the superior pubic ramus. Iatrogenic injury during the ilioinguinal or Stoppa approach can cause massive, difficult-to-control hemorrhage.

Question 11302

Topic: Biology, Genetics & Bone Healing

A 68-year-old female on alendronate for 12 years presents with a low-energy transverse subtrochanteric fracture of the right femur with lateral cortical "beaking." She complains of 3 months of aching pain in her left thigh as well. Radiographs of the left femur show lateral cortical thickening but no complete fracture. What is the recommended management for the left femur?

. Immediate cessation of bisphosphonates and close observation
. Prophylactic intramedullary nailing of the left femur
. Application of a custom functional hip brace
. Initiation of teriparatide without surgical intervention
. Core decompression of the left proximal femur

Correct Answer & Explanation

. Immediate cessation of bisphosphonates and close observation

Explanation

This patient has an atypical femur fracture associated with long-term bisphosphonate use. The presence of prodromal pain and radiographic lateral cortical thickening on the contralateral side indicates an impending fracture, necessitating prophylactic intramedullary nailing.

Question 11303

Topic: Surgical Anatomy & Approaches

A 45-year-old female presents with an acetabular fracture after a motor vehicle collision. Computed tomography imaging reveals a fracture extending through the anterior column and the posterior hemitransverse. What is the classic surgical approach for this specific Letournel pattern?

. Kocher-Langenbeck approach
. Ilioinguinal approach
. Extended iliofemoral approach
. Posterior approach alone
. Trans-symphyseal approach

Correct Answer & Explanation

. Kocher-Langenbeck approach

Explanation

Anterior column and posterior hemitransverse fractures are typically addressed via an anterior approach (Ilioinguinal or Stoppa). The primary displacement is anterior, and the posterior component can usually be manipulated indirectly from the anterior window.

Question 11304

Topic: Surgical Anatomy & Approaches

A 7-year-old girl sustains an extension-type supracondylar fracture of the humerus that is posteromedially displaced. Which nerve is at the highest risk of injury in this specific displacement pattern?

. Median nerve
. Ulnar nerve
. Radial nerve
. Musculocutaneous nerve
. Axillary nerve

Correct Answer & Explanation

. Median nerve

Explanation

In extension-type supracondylar fractures with posteromedial displacement, the proximal fragment is driven anterolaterally, putting the radial nerve at the highest risk of injury. Posterolateral displacement endangers the median nerve and brachial artery.

Question 11305

Topic: 1. General Principles & Basic Science

A 45-year-old male presents with a deep laceration over the 3rd metacarpophalangeal joint sustained during a fistfight (human bite/clenched fist injury). He presents 24 hours later with erythema and purulent drainage. Which organism is most specifically associated with this injury type, and what is the appropriate empiric antibiotic therapy?

. Pasteurella multocida; Amoxicillin-clavulanate
. Eikenella corrodens; Amoxicillin-clavulanate
. Capnocytophaga canimorsus; Penicillin G
. Bartonella henselae; Azithromycin
. Staphylococcus aureus; Cephalexin

Correct Answer & Explanation

. Pasteurella multocida; Amoxicillin-clavulanate

Explanation

Human bite wounds (clenched fist injuries) are characteristically associated with Eikenella corrodens, along with staph and strep species. The empiric oral antibiotic of choice is Amoxicillin-clavulanate. Pasteurella multocida is associated with dog and cat bites.

Question 11306

Topic: 1. General Principles & Basic Science

During a traumatic below-knee amputation, the surgeon is isolating the superficial peroneal nerve. To prevent the formation of a symptomatic stump neuroma, what is the widely recommended surgical technique for managing the nerve?

. Ligate the nerve with non-absorbable suture and leave it directly at the fascial incision line
. Cauterize the nerve ending and wrap it in a local skin flap
. Apply gentle distal traction, transect the nerve sharply, and allow it to retract deep into healthy soft tissues
. Inject the nerve stump with a heavy concentration of phenol
. Anastomose the distal end of the nerve to a nearby small vein

Correct Answer & Explanation

. Ligate the nerve with non-absorbable suture and leave it directly at the fascial incision line

Explanation

To prevent a symptomatic stump neuroma in amputations, the standard technique is traction neurectomy. This involves applying gentle distal traction to the nerve, transecting it sharply, and allowing the proximal stump to retract deep into a healthy, well-cushioned muscle belly away from the scar, incision line, and weight-bearing areas.

Question 11307

Topic: 1. General Principles & Basic Science

Deflation of a pneumatic tourniquet after 2 hours of inflation during a complex lower extremity reconstruction is most likely to cause which of the following acute physiological changes?

. Increase in core body temperature
. Increase in systemic vascular resistance
. Decrease in end-tidal carbon dioxide (ETCO2)
. Transient decrease in systemic blood pressure
. Decrease in serum potassium levels

Correct Answer & Explanation

. Increase in core body temperature

Explanation

Upon tourniquet deflation, the sudden release of ischemic, acidotic blood containing vasoactive metabolites back into systemic circulation causes a transient decrease in systemic vascular resistance and blood pressure. It also causes a surge in end-tidal CO2 (due to metabolic acidosis) and a decrease in core body temperature.

Question 11308

Topic: Biology, Genetics & Bone Healing

Secondary bone healing (healing by callus formation) is characterized by a sequential progression of tissue types following a fracture. What is the correct order of the predominant tissue types bridging the fracture gap during this physiological process?

. Hematoma -> Woven bone -> Cartilage -> Lamellar bone
. Hematoma -> Granulation tissue -> Cartilage -> Woven bone -> Lamellar bone
. Granulation tissue -> Hematoma -> Woven bone -> Cartilage -> Lamellar bone
. Hematoma -> Cartilage -> Granulation tissue -> Lamellar bone -> Woven bone
. Woven bone -> Hematoma -> Granulation tissue -> Cartilage -> Lamellar bone

Correct Answer & Explanation

. Hematoma -> Woven bone -> Cartilage -> Lamellar bone

Explanation

Secondary fracture healing progresses sequentially through distinct phases: Inflammation (Hematoma followed by Granulation tissue), Soft Callus formation (predominantly Cartilage), Hard Callus formation (calcification into Woven bone), and finally Remodeling (replacement of woven bone with mature Lamellar bone along lines of stress).

Question 11309

Topic: Surgical Anatomy & Approaches

During an anterior intrapelvic (modified Stoppa) approach for the fixation of an anterior column acetabular fracture, massive hemorrhage occurs while dissecting over the superior pubic ramus. Which anatomical vascular anastomosis has likely been disrupted?

. Anastomosis between the obturator vessels and the external iliac or inferior epigastric vessels
. Anastomosis between the internal pudendal and the inferior gluteal vessels
. Anastomosis between the deep circumflex iliac and the ascending branch of the lateral femoral circumflex artery
. Anastomosis between the internal iliac and the median sacral vessels
. Anastomosis between the superior gluteal artery and the medial femoral circumflex artery

Correct Answer & Explanation

. Anastomosis between the obturator vessels and the external iliac or inferior epigastric vessels

Explanation

The "corona mortis" (crown of death) is a significant vascular anastomosis between the obturator vessels (from the internal iliac system) and the external iliac or inferior epigastric vessels. It crosses the superior pubic ramus at an average distance of 5-6 cm from the symphysis pubis and is at high risk of iatrogenic injury during anterior intrapelvic exposures.

Question 11310

Topic: Surgical Anatomy & Approaches

Following a high-energy dashboard injury, a patient is diagnosed with a posterior wall acetabular fracture and posterior hip dislocation. Post-reduction, the patient exhibits a foot drop and is unable to dorsiflex the toes. Which neural structure is most characteristically injured in this trauma mechanism?

. Tibial division of the sciatic nerve
. Peroneal (fibular) division of the sciatic nerve
. Femoral nerve
. Sural nerve
. Superior gluteal nerve

Correct Answer & Explanation

. Tibial division of the sciatic nerve

Explanation

The sciatic nerve is at high risk during posterior hip dislocations and posterior wall acetabular fractures. The peroneal (fibular) division is disproportionately affected compared to the tibial division due to its lateral and more fixed anatomical position, tethering it as the femoral head displaces posteriorly.

Question 11311

Topic: Infection, Pharmacology & VTE

An 82-year-old female with a history of atrial fibrillation presents with a displaced femoral neck fracture. She is taking Apixaban (a direct factor Xa inhibitor). What is the optimal timing for surgery to minimize mortality and bleeding risk?

. Delay surgery for 5 days to allow complete washout of Apixaban
. Proceed with surgery within 48 hours; consider holding Apixaban for 24-48 hours depending on renal function
. Administer Vitamin K and Fresh Frozen Plasma, then proceed to surgery immediately
. Administer Protamine sulfate and proceed to surgery immediately
. Perform non-operative management only

Correct Answer & Explanation

. Delay surgery for 5 days to allow complete washout of Apixaban

Explanation

Current guidelines advocate surgery within 48 hours for geriatric hip fractures. For patients on direct oral anticoagulants like Apixaban, surgery can typically be safely performed after holding the medication for 24-48 hours. Vitamin K and FFP do not reverse DOACs.

Question 11312

Topic: 1. General Principles & Basic Science

The Mangled Extremity Severity Score (MESS) was developed to help surgeons objectively differentiate between limbs that are salvageable and those that require primary amputation. Which of the following variables is NOT a component of the MESS evaluation?

. Skeletal and soft-tissue injury extent
. Limb ischemia duration and severity
. Patient age
. Presence of a severe head injury (GCS < 8)
. Systemic hypotension (Shock)

Correct Answer & Explanation

. Skeletal and soft-tissue injury extent

Explanation

The Mangled Extremity Severity Score (MESS) comprises four distinct categories: 1) Skeletal / Soft-tissue injury (energy level), 2) Limb ischemia, 3) Shock (systemic hemodynamics), and 4) Patient age. A score of 7 or higher historically suggested amputation, though modern limb salvage techniques have altered its predictive value. The presence of an isolated severe head injury or Glasgow Coma Scale (GCS) is not a component of the MESS.

Question 11313

Topic: Infection, Pharmacology & VTE

An 82-year-old female sustains an open distal femur fracture. Her medical history includes atrial fibrillation, for which she takes rivaroxaban (a direct Factor Xa inhibitor). She requires urgent surgical debridement and stabilization. If she experiences severe, life-threatening hemorrhage during surgery, what is the most specific and appropriate reversal agent?

. Idarucizumab
. Andexanet alfa
. Protamine sulfate
. Vitamin K and Fresh Frozen Plasma
. Desmopressin (DDAVP)

Correct Answer & Explanation

. Idarucizumab

Explanation

Rivaroxaban (Xarelto) and apixaban (Eliquis) are direct Factor Xa inhibitors. The specific reversal agent for life-threatening bleeding in patients taking these medications is Andexanet alfa, a recombinant modified human Factor Xa decoy protein. Idarucizumab is the specific reversal agent for dabigatran (a direct thrombin inhibitor). Protamine sulfate reverses heparin, and Vitamin K/FFP (or Prothrombin Complex Concentrate) is used for warfarin reversal.

Question 11314

Topic: 1. General Principles & Basic Science

Based on the landmark CRASH-2 trial, what is the optimal dosing regimen and timing for the administration of Tranexamic Acid (TXA) to confer a survival benefit in bleeding trauma patients?

. 1g loading dose over 10 minutes followed by 1g infusion over 8 hours, administered within 3 hours of injury
. 1g loading dose followed by 1g infusion over 8 hours, administered within 6 hours of injury
. 2g IV push upon arrival, regardless of time from injury
. 1g loading dose followed by 2g infusion over 24 hours, administered within 3 hours of injury
. 1g given only if Thromboelastography (TEG) demonstrates evidence of hyperfibrinolysis

Correct Answer & Explanation

. 1g loading dose over 10 minutes followed by 1g infusion over 8 hours, administered within 3 hours of injury

Explanation

The CRASH-2 (Clinical Randomisation of an Antifibrinolytic in Significant Haemorrhage) trial demonstrated that TXA significantly reduces overall mortality and death due to bleeding in trauma patients if administered within 3 hours of the injury. The protocol-defined dosing regimen is a 1g loading dose infused over 10 minutes, followed by an intravenous infusion of 1g over 8 hours. Administration after 3 hours was associated with an increased risk of death due to bleeding.

Question 11315

Topic: 1. General Principles & Basic Science

A 22-year-old collegiate wrestler presents to the emergency room with severe neck pain and a radicular pain shooting down his right arm after being taken down on his head.

Lateral cervical radiographs reveal approximately 25% anterior subluxation of the C5 vertebral body over C6. What is the classic mechanism of injury for a unilateral facet dislocation?

. Flexion and rotation
. Extension and axial load
. Pure hyperflexion
. Extension and rotation
. Axial distraction

Correct Answer & Explanation

. Flexion and rotation

Explanation

A unilateral facet dislocation occurs due to a flexion-rotation mechanism. This typically results in less than 50% anterior translation (subluxation) of the superior vertebral body on the inferior one. In contrast, bilateral facet dislocations result from pure hyperflexion forces and typically cause greater than 50% anterior translation.

Question 11316

Topic: Physiology & Rehabilitation
A 28-year-old male presents with a spinal cord injury following a knife wound to the right side of his mid-thoracic back. Neurological examination reveals complete loss of motor function and proprioception in his right lower extremity, and a loss of pain and temperature sensation in his left lower extremity. Which spinal cord syndrome describes this pattern?
. Anterior cord syndrome
. Central cord syndrome
. Posterior cord syndrome
. Brown-Séquard syndrome
. Conus medullaris syndrome

Correct Answer & Explanation

. Brown-Séquard syndrome

Explanation

Brown-Séquard syndrome results from a functional hemisection of the spinal cord. It presents with ipsilateral loss of motor function (corticospinal tract) and proprioception/vibratory sense (dorsal columns), and contralateral loss of pain and temperature sensation (spinothalamic tract), typically starting a few levels below the lesion.

Question 11317

Topic: Biology, Genetics & Bone Healing
A 75-year-old female with severe osteoporosis complains of unremitting back pain 6 months after a minor fall. Her pain worsens significantly when standing and improves when supine. A lateral radiograph demonstrates an intravertebral vacuum cleft sign within a severely compressed T12 vertebral body. What is the eponymous name of this condition?
. Pott's disease
. Kümmell disease
. Baastrup's disease
. Calvé's disease
. Scheuermann's disease

Correct Answer & Explanation

. Kümmell disease

Explanation

Kümmell disease is delayed post-traumatic avascular necrosis of a vertebral body. It presents as a progressive vertebral collapse following a minor injury, often after an asymptomatic period. The hallmark radiographic finding is the intravertebral vacuum cleft sign on extension films, representing nitrogen gas filling the necrotic cavity.

Question 11318

Topic: Surgical Anatomy & Approaches

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

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

Correct Answer & Explanation

. Superior gluteal nerve

Explanation

The direct anterior approach utilizes the Hueter interval, an internervous plane between the tensor fasciae latae (superior gluteal nerve) and the sartorius (femoral nerve). The lateral femoral cutaneous nerve crosses the superficial aspect of this operative field and is at highest risk of neuropraxia or transection, which results in lateral thigh numbness (meralgia paresthetica).

Question 11319

Topic: Biomechanics & Biomaterials
Which of the following manufacturing processes is essential in creating highly cross-linked polyethylene (HXLPE) to significantly reduce wear in total hip arthroplasty?
. Gamma irradiation followed by melting or annealing
. Addition of high-dose vitamin C
. Cold drawing of the polymer chains under tension
. Decreasing the molecular weight of the polyethylene base resin
. Introduction of calcium phosphate into the polymer matrix

Correct Answer & Explanation

. Gamma irradiation followed by melting or annealing

Explanation

Highly cross-linked polyethylene is manufactured by exposing ultra-high molecular weight polyethylene (UHMWPE) to gamma or electron beam irradiation. This creates free radicals that bond to form cross-links, drastically increasing wear resistance. To prevent long-term oxidative degradation from residual free radicals, the material is subsequently either melted or annealed. Modern alternatives include doping with Vitamin E.

Question 11320

Topic: Biology, Genetics & Bone Healing

A 68-year-old male presents with progressive thigh pain 15 years after an uncemented THA. Radiographs reveal extensive endosteal scalloping and localized bone loss around the proximal femur. The stem appears to have subsided 4 mm. What is the primary biological mediator responsible for the activation of osteoclasts in this disease process?

. Interleukin-10 (IL-10)
. Transforming growth factor beta (TGF-b)
. Receptor activator of nuclear factor kappa-B ligand (RANKL)
. Bone morphogenetic protein-2 (BMP-2)
. Interferon gamma (IFN-y)

Correct Answer & Explanation

. Interleukin-10 (IL-10)

Explanation

Particle disease (aseptic loosening) is driven by macrophage phagocytosis of wear debris. This triggers the release of pro-inflammatory cytokines, which ultimately stimulate the production of RANKL, the primary mediator of osteoclast activation.

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