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1. General Principles & Basic Science MCQs

Practice Set 265 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 5281

Topic: Infection, Pharmacology & VTE

A 42-year-old patient sustains a high-energy bicondylar tibial plateau fracture. Computed tomography reveals a large, vertically oriented, displaced posteromedial shear fragment. The surgical plan includes anti-glide buttress plating of this specific fragment. Which surgical interval provides the most direct and appropriate access?

. Between the rectus femoris and vastus lateralis
. Between the semimembranosus and popliteal artery
. Between the medial head of the gastrocnemius and the pes anserinus
. Between the lateral head of the gastrocnemius and the soleus
. Through a direct medial approach splitting the medial collateral ligament

Correct Answer & Explanation

. Between the medial head of the gastrocnemius and the pes anserinus

Explanation

The posteromedial approach to the tibial plateau utilizes the interval between the medial head of the gastrocnemius and the pes anserinus tendons. Retracting the medial gastrocnemius laterally protects the neurovascular bundle in the popliteal fossa, while the pes anserinus is retracted medially or distally. This provides direct visualization of the posteromedial cortex, allowing for the application of an anti-glide buttress plate for posteromedial shear fragments.

Question 5282

Topic: Biology, Genetics & Bone Healing

A 30-year-old patient undergoes an antegrade reamed intramedullary nailing of a diaphyseal femur fracture utilizing dynamic locking holes. This mechanical construct permits controlled axial micromotion. This relative stability primarily promotes fracture healing through which of the following biological processes?

. Primary bone healing via cutting cones
. Intramembranous ossification exclusively
. Endochondral ossification
. Creeping substitution
. Direct osteoblastic apposition without an intermediate cartilage phase

Correct Answer & Explanation

. Endochondral ossification

Explanation

Constructs that provide relative stability (such as intramedullary nails, bridge plates, and external fixators) permit micromotion at the fracture site. This strain environment stimulates secondary bone healing, which occurs primarily via endochondral ossification. This process involves the formation of a hematoma, followed by a fibrocartilaginous soft callus, which is subsequently calcified into a hard woven bone callus and eventually remodeled. Primary bone healing (via Haversian remodeling/cutting cones) requires absolute stability and direct bone-to-bone contact.

Question 5283

Topic: 1. General Principles & Basic Science

A 21-year-old man sustains multiple gunshot wounds to his right upper extremity. He can not extend his digits or his thumb but can extend and radially deviate his wrist. An injury to the radial nerve or one of its branches has most likely occurred at which of the following locations?

Orthopedic Surgery Board Review 2026 | High-Yield MCQs - Set 2 - Figure 36

. Spiral groove of the humerus
. Midshaft of the radius
. Radial neck
. Anatomic neck of the humerus
. Surgical neck of the humerus

Correct Answer & Explanation

. Radial neck

Explanation

In this patient, the radial nerve is most likely injured at the level of the radial neck. The radial nerve emerges from the posterior cord of the brachial plexus and travels along the spiral groove of the humerus. At the level of the lateral humeral condyle, the radial nerve branches into the posterior interosseous nerve after giving off two cutaneous branches, the superficial radial and the posterior cutaneous. The posterior interosseous nerve travels through the supinator muscle and winds around the radial neck. At this level, the posterior interosseous nerve is vulnerable to injury, particularly following fracture or penetrating trauma. Netter F: The Ciba Collection of Medical Illustrations: The Musculoskeletal System, Part 1: Anatomy, Physiology and Metabolic Disorders. West Caldwell, NJ, Ciba-Geigy Corporation, 1987, vol 8, p 53.

Question 5284

Topic: 1. General Principles & Basic Science

Which of the following accurately describes the biosynthetic materials tricalcium phosphate (TCP) and hydroxyapatite?

. The osteoblast is the cell responsible for resorption of hydroxyapatite.
. Once in the body, TCP is partially converted to hydroxyapatite.
. TCP undergoes biologic resorption at a rate 10 times slower than hydroxyapatite.
. TCP is much stronger biomechanically in compression than hydroxyapatite.
. Optimal pore size for both materials appears to be less than 150 um.

Correct Answer & Explanation

. Once in the body, TCP is partially converted to hydroxyapatite.

Explanation

TCP is resorbed more rapidly, at a rate of 10 to 20 times faster than hydroxyapatite, partially because its larger pore size makes it a weaker substance. It provides significantly less compressive strength than hydroxyapatite. It does partially convert to hydroxyapatite, thus slowing its resorption rate. The absorbing cell of hydroxyapatite is the foreign body giant cell, not the osteoclast. Optimum pore size appears to be between 150 and 500 um. Lane JM, Bostrom MP: Bone grafting and new composite biosynthetic graft materials. Instr Course Lect 1998;47:525-534.

Question 5285

Topic: 1. General Principles & Basic Science

Figure 9 shows the AP radiograph of a 65-year-old man who has knee pain and swelling. What is the most likely diagnosis?

General Orthopedics Board Review 2026: High-Yield MCQs (Set 18) - Figure 120

. Gout
. Chondrocalcinosis (pseudogout)
. Hemochromatosis
. Rheumatoid arthritis
. Ochronosis

Correct Answer & Explanation

. Chondrocalcinosis (pseudogout)

Explanation

Although all the choices are known causes of joint degeneration (secondary osteoarthritis), only chondrocalcinosis shows distinct linear calcification of the cartilage due to deposition of calcium pyrophosphate crystals. Gout is a recurrent acute arthritis resulting from the deposition of monosodium urate from supersaturated hyperuricemic body fluids. Hemochromotosis is characterized by focal or generalized deposition of iron within body tissues. Arthritis may be present but is less common than other manifestations such as liver cirrhosis, skin pigmentation, diabetes mellitus, and cardiac disease. Rheumatoid arthritis is a nonspecific, usually symmetric inflammation of peripheral joints resulting in destruction of articular and periarticular structures. Ochronosis is a hereditary enzyme deficiency (homogentisic acid oxidase) resulting in deposition of homogentisic acid polymers in articular cartilage. Barrack RL, Booth RE Jr, Lonner JH, et al (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction 3. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2006, p 188.

Question 5286

Topic: 1. General Principles & Basic Science

Following a vertebroplasty of L2, cement is noted to protrude directly anterior to the L2 vertebral body. The cement is closest to which of the following structures?

General Orthopedics Board Review 2026: High-Yield MCQs (Set 18) - Figure 127

. Inferior vena cava
. Pancreas
. Duodenum
. Left lobe of the liver
. Descending aorta

Correct Answer & Explanation

. Descending aorta

Explanation

At the level of L2, the liver and the vena cava lie to the right. The pancreas and duodenum are anterior to the aorta. The aorta lies in the midline just in front of the vertebral body. Clement CD: Anatomy: A Regional Atlas of Human Anatomy, ed 3. Baltimore, MD, Munich, Germany, Urban and Schwarzberg, 1987, Figure 331.

Question 5287

Topic: Infection, Pharmacology & VTE

Acetaminophen is an antipyretic medication. It exerts its pharmacologic effects by inhibiting which of the following enzymes?

. Cyclooxygenase-2 (COX-2)
. Interleukin-1 beta (IL-1 B)
. Tumor necrosis factor alpha (TNF-A)
. 5-Hydroxytryptamine (5-HT)
. Metalloproteinases (MMPs)

Correct Answer & Explanation

. Interleukin-1 beta (IL-1 B)

Explanation

Acetaminophen inhibits prostaglandin E2 production via IL-1 B, without affecting cyclooxygenase-2 enzymatic activity. The therapeutic concentrations of acetaminophen induce an inhibition of IL-1 B-dependent NF-kappa B nuclear translocation. The selectivity of this effect suggests the existence of an acetaminophen-specific activity at the transcriptional level that may be one of the mechanisms through which the drug exerts its pharmacologic effects. Acetaminophen does not affect any of the other enzymes named above.

Question 5288

Topic: Surgical Anatomy & Approaches

A 38-year-old woman fell from a ladder onto her right hip. The radiographs and CT scan are shown in Figures 52a through 52d. What is the best surgical approach for this fracture?

. Kocher-Langenbeck
. Iliofemoral
. Ilioinguinal
. Extended iliofemoral
. Triradiate approach

Correct Answer & Explanation

. Ilioinguinal

Explanation

The fracture is an associated both column fracture. The best approach for this fracture is the ilioinguinal. The Kocher-Langenbeck is best for posterior injuries to the acetabulum and some transverse fractures. The iliofemoral alone is limited to high anterior column injuries. The extended iliofemoral and triradiate approaches although useful for this fracture, have a higher rate of complications. Letournel E: The treatment of acetabular fractures through the ilioinguinal approach. Clin Orthop Relat Res 1993;292:62-76.

Question 5289

Topic: Surgical Anatomy & Approaches

A 45-year-old man sustains an unstable anteroposterior compression (APC-II) pelvic ring injury requiring anterior symphyseal plating. During exposure via a Pfannenstiel approach, brisk arterial bleeding is encountered on the posterior aspect of the superior pubic ramus. Which of the following is the most likely source of this bleeding?

. External iliac artery
. Internal pudendal artery
. Anastomosis between the obturator and external iliac/inferior epigastric vessels
. Inferior epigastric artery
. Superior gluteal artery

Correct Answer & Explanation

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

Explanation

The 'corona mortis' (crown of death) is an important vascular anastomosis between the external iliac or inferior epigastric system and the obturator system. It courses over the posterior aspect of the superior pubic ramus. Iatrogenic injury during a Pfannenstiel or ilioinguinal exposure can lead to significant hemorrhage that is difficult to control.

Question 5290

Topic: Biology, Genetics & Bone Healing

A 72-year-old woman presents with a 3-month history of vague, progressively worsening thigh pain. She denies any recent trauma but has been taking alendronate for the last 8 years. Radiographs reveal cortical thickening of the lateral femoral shaft with a transverse radiolucent line. What is the most appropriate next step in management?

. Discontinue alendronate and prescribe teriparatide exclusively without surgery
. Core decompression of the lateral cortex
. Prophylactic cephalomedullary nailing of the affected femur
. Open reduction and internal fixation with a dynamic compression plate
. Continue alendronate and recommend protected weight-bearing

Correct Answer & Explanation

. Prophylactic cephalomedullary nailing of the affected femur

Explanation

Atypical femur fractures (AFFs) are associated with prolonged bisphosphonate use. Patients presenting with prodromal pain and radiographic signs of an impending fracture, such as lateral cortical thickening and a transverse stress line (the "dreaded black line"), are at a high risk of progression to a complete fracture. The standard of care for an impending atypical femur fracture is prophylactic intramedullary nailing. Bisphosphonates should also be discontinued, and anabolic agents like teriparatide can be considered, but surgical stabilization is the primary orthopedic intervention.

Question 5291

Topic: Surgical Anatomy & Approaches

A 25-year-old unrestrained driver is involved in a head-on motor vehicle collision. He presents to the trauma bay with a shortened, internally rotated, and adducted left lower extremity. A radiograph confirms a posterior hip dislocation. Which of the following nerve injuries is most commonly associated with this injury?

. Femoral nerve
. Sciatic nerve (peroneal division)
. Obturator nerve
. Superior gluteal nerve
. Sciatic nerve (tibial division)

Correct Answer & Explanation

. Sciatic nerve (peroneal division)

Explanation

Posterior hip dislocations are classically associated with injury to the sciatic nerve. Within the sciatic nerve, the peroneal division is significantly more vulnerable to injury than the tibial division because its fibers are located more laterally, have less connective tissue protection, and are more securely tethered distally at the fibular head.

Question 5292

Topic: 1. General Principles & Basic Science

What is the most common cause of errors that harm patients?

. Communication breakdown
. Equipment breakdown
. Nursing competence
. Patient noncompliance
. Physician competence

Correct Answer & Explanation

. Communication breakdown

Explanation

The AMA report identified communication breakdown as the most common cause of errors that harm patients. It is extremely important to learn to communicate effectively with your patients. Understanding cultural and language differences helps avoid communication errors. Jimenez R, Lewis VO (eds): Culturally Competent Care Guidebook. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2007. American Medical Association ethical force program report: "Improving communication - Improving care", 2006

Question 5293

Topic: Surgical Anatomy & Approaches

During the ilioinguinal approach for open reduction and internal fixation of an anterior column acetabular fracture, vigorous arterial bleeding is encountered on the posterior aspect of the superior pubic ramus, approximately 5 cm from the pubic symphysis. Which of the following anatomic structures is the most likely source of this bleeding?

. An anastomosis between the external iliac and obturator vessels
. An anastomosis between the internal pudendal and inferior gluteal vessels
. An aberrant branch of the inferior epigastric artery
. The superior gluteal artery
. The internal pudendal artery

Correct Answer & Explanation

. An anastomosis between the external iliac and obturator vessels

Explanation

The bleeding source is the corona mortis ('crown of death'), which is a critical vascular anastomosis situated on the posterior aspect of the superior pubic ramus. It typically connects the obturator system (internal iliac system) with the external iliac system (via the inferior epigastric vessels). Care must be taken to identify and ligate this structure during the ilioinguinal or modified Stoppa approaches.

Question 5294

Topic: Surgical Anatomy & Approaches

A 40-year-old male motorcyclist experiences a severe lateral traction injury to his right shoulder. He presents with massive shoulder swelling, an absent right radial pulse, and a completely flail right upper extremity. Radiographs reveal a widened scapulothoracic articulation and lateral displacement of the scapula. What is the most likely associated neurologic injury?

. Isolated axillary nerve palsy
. Complete brachial plexus avulsion
. Isolated musculocutaneous nerve transection
. Cervical spinal cord injury at C5-C6
. Ulnar nerve transection at the elbow

Correct Answer & Explanation

. Complete brachial plexus avulsion

Explanation

The clinical scenario describes scapulothoracic dissociation, a highly lethal, high-energy traction injury. It is characterized by complete disruption of the scapulothoracic articulation and is highly associated with catastrophic neurovascular injuries, most notably complete brachial plexus avulsions and subclavian/axillary artery disruptions.

Question 5295

Topic: Surgical Anatomy & Approaches

A 35-year-old male is undergoing open reduction and internal fixation of a transverse posterior wall acetabular fracture via a Kocher-Langenbeck approach. To minimize iatrogenic traction injury to the sciatic nerve during retraction, what is the optimal position of the operative lower extremity?

. Hip flexed and knee extended
. Hip extended and knee flexed
. Hip flexed and knee flexed
. Hip extended and knee extended
. Hip abducted and knee extended

Correct Answer & Explanation

. Hip extended and knee flexed

Explanation

During a Kocher-Langenbeck approach for acetabular fractures, the sciatic nerve is at significant risk of iatrogenic stretch injury from retractors. Keeping the hip extended and the knee flexed introduces maximum slack into the sciatic nerve, thereby minimizing tension and reducing the risk of a post-operative nerve palsy (e.g., foot drop).

Question 5296

Topic: Biology, Genetics & Bone Healing

A 68-year-old woman treated with alendronate for 8 years presents with a 3-month history of an unprovoked dull ache in her right thigh. A radiograph of the femur reveals localized lateral cortical thickening and a transverse radiolucent line in the subtrochanteric region. What is the most appropriate next step in orthopaedic management?

. Discontinue alendronate and prescribe strict bed rest for 6 weeks
. Discontinue alendronate and switch immediately to denosumab
. Discontinue alendronate, initiate protected weight-bearing, and perform prophylactic intramedullary nailing
. Perform an open biopsy of the lesion to rule out metastatic disease
. Recommend extracorporeal shockwave therapy to the lateral thigh

Correct Answer & Explanation

. Discontinue alendronate, initiate protected weight-bearing, and perform prophylactic intramedullary nailing

Explanation

This patient has symptoms and classic radiographic signs (lateral cortical thickening, transverse radiolucent line, 'beaking') of an impending bisphosphonate-related atypical femur fracture. Because the lesion is symptomatic, she is at high risk for completion of the fracture. Prophylactic intramedullary nailing is indicated to prevent complete displacement and associated morbidity.

Question 5297

Topic: Biology, Genetics & Bone Healing

A 50-year-old woman is evaluated for a nonunion of a midshaft humerus fracture 6 months after injury. She was originally treated with a Sarmiento cast brace. Radiographs show atrophic bone ends with no callus formation. Laboratory markers for infection are negative. What is the most reliable surgical treatment?

. Open reduction and internal fixation with compression plating and autologous bone grafting
. Continuation of cast bracing with the addition of a bone stimulator
. Closed reamed intramedullary nailing without bone graft
. Application of a circular external fixator
. Placement of recombinant bone morphogenetic protein (BMP) without rigid fixation

Correct Answer & Explanation

. Open reduction and internal fixation with compression plating and autologous bone grafting

Explanation

Atrophic nonunions occur due to a lack of biology and require both mechanical stability and biological stimulation to heal. For an atrophic humeral shaft nonunion, the gold standard treatment is open reduction and internal fixation (typically using heavy compression plating) combined with autologous bone grafting (e.g., from the iliac crest) to provide the necessary osteoinductive and osteoconductive properties.

Question 5298

Topic: 1. General Principles & Basic Science
According to the Lower Extremity Assessment Project (LEAP) study, which of the following scoring systems most accurately predicts the functional outcome and need for amputation in a patient with a mangled lower extremity?
. Mangled Extremity Severity Score (MESS)
. Limb Salvage Index (LSI)
. Nerve Injury, Ischemia, Soft-Tissue Injury, Skeletal Injury, Shock, and Age of Patient Score (NISSSI)
. Predictive Salvage Index (PSI)
. None of the available scoring systems

Correct Answer & Explanation

. None of the available scoring systems

Explanation

The LEAP study demonstrated that none of the existing limb salvage scoring systems (including MESS, LSI, NISSSI, and PSI) are highly predictive of the ultimate need for amputation or the final functional outcome.

Question 5299

Topic: Biology, Genetics & Bone Healing

A 65-year-old woman on long-term alendronate therapy presents with prodromal thigh pain followed by a low-energy transverse fracture of the femoral shaft. Radiographs show lateral cortical thickening at the fracture site. What is the primary pathophysiologic mechanism leading to this atypical fracture?

. Overactive osteoblast function leading to brittle bone
. Defective Type I collagen synthesis
. Suppression of targeted bone remodeling and accumulation of microdamage
. Increased osteoclastogenesis causing local osteolysis
. Primary hyperparathyroidism

Correct Answer & Explanation

. Suppression of targeted bone remodeling and accumulation of microdamage

Explanation

Long-term bisphosphonate use suppresses targeted osteoclastic bone remodeling. This impairs the normal repair of daily microdamage, leading to an accumulation of microcracks, increased bone brittleness, and eventually an atypical femur fracture.

Question 5300

Topic: 1. General Principles & Basic Science

The CRASH-2 trial demonstrated a significant mortality benefit for the use of tranexamic acid (TXA) in bleeding trauma patients. What is the mechanism of action and the optimal timing of administration for TXA?

. Enhances plasminogen activation; must be given within 6 hours
. Competitive inhibition of plasminogen activation; must be given within 3 hours
. Direct inhibition of Factor Xa; must be given within 3 hours
. Irreversible binding to platelets; must be given within 12 hours
. Activation of the coagulation cascade; must be given within 1 hour

Correct Answer & Explanation

. Competitive inhibition of plasminogen activation; must be given within 3 hours

Explanation

Tranexamic acid (TXA) is an antifibrinolytic that competitively inhibits the activation of plasminogen to plasmin. The CRASH-2 trial showed improved survival in bleeding trauma patients when TXA is administered within 3 hours of injury.

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