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1. General Principles & Basic Science MCQs

Practice Set 733 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 14641

Topic: Biology, Genetics & Bone Healing

What type of bone graft offers osteoinductive, osteoconductive, and osteogenic properties?

. Allograft
. Demineralized bone matrix (DBM)
. Autograft (cancellous)
. Ceramic bone substitutes
. Bone morphogenetic proteins (BMPs)

Correct Answer & Explanation

. Autograft (cancellous)

Explanation

Autograft (cancellous) is considered the 'gold standard' for bone grafting because it possesses all three essential properties: osteoconduction (provides a scaffold for new bone growth), osteoinduction (contains growth factors that stimulate host mesenchymal stem cells to differentiate into osteoblasts), and osteogenesis (contains living osteocytes and osteoblasts from the donor site that can immediately form new bone). Allografts are primarily osteoconductive and osteoinductive but lack viable osteogenic cells. DBM is primarily osteoinductive and osteoconductive. Ceramic bone substitutes are mainly osteoconductive. BMPs are purely osteoinductive.

Question 14642

Topic: 1. General Principles & Basic Science

Which of the following is a classic radiographic finding for chronic osteomyelitis?

. Periosteal elevation (Codman's triangle)
. Sequestrum and involucrum
. Soft tissue swelling and joint effusion
. Widening of the growth plate
. Punctate calcifications within soft tissue

Correct Answer & Explanation

. Sequestrum and involucrum

Explanation

Sequestrum and involucrum are classic radiographic findings for chronic osteomyelitis. A sequestrum is a piece of dead, devascularized bone that has become separated from the living bone during the process of necrosis. An involucrum is a sheath of new bone that forms around a sequestrum. These findings indicate a chronic, established infection. Codman's triangle is typically seen in aggressive bone tumors or acute osteomyelitis. Soft tissue swelling and joint effusion are more indicative of acute infection or inflammatory processes. Widening of the growth plate is associated with rickets or SCFE. Punctate calcifications are non-specific and can be seen in various soft tissue lesions.

Question 14643

Topic: Infection, Pharmacology & VTE

A 65-year-old male undergoes total knee arthroplasty. On postoperative day 2, he develops acute shortness of breath, pleuritic chest pain, and hypoxemia. What is the most likely diagnosis?

. Pneumonia
. Acute myocardial infarction
. Pulmonary embolism
. Fat embolism syndrome
. Atelectasis

Correct Answer & Explanation

. Pulmonary embolism

Explanation

Acute shortness of breath, pleuritic chest pain, and hypoxemia occurring post-total knee arthroplasty are classic symptoms of a pulmonary embolism (PE). Deep vein thrombosis (DVT) and subsequent PE are serious and relatively common complications of major orthopedic surgery. While atelectasis is common post-operatively, it usually presents with more subtle symptoms. Pneumonia and myocardial infarction are possibilities but less likely to manifest with pleuritic pain so acutely after TKA. Fat embolism syndrome usually occurs earlier (within 24-48 hours), often after long bone fractures, and includes petechial rash and neurological changes, which are not mentioned here.

Question 14644

Topic: Infection, Pharmacology & VTE

A 50-year-old male with a history of chronic alcoholism presents with pain and swelling in his left great toe. On examination, the joint is warm, erythematous, and exquisitely tender to touch. Serum uric acid level is elevated. What is the most appropriate acute management?

. Initiate allopurinol immediately.
. Prescribe indomethacin or colchicine.
. Aspirate the joint and inject corticosteroids.
. Start long-term urate-lowering therapy.
. Refer for surgical fusion of the MTP joint.

Correct Answer & Explanation

. Prescribe indomethacin or colchicine.

Explanation

The presentation is classic for an acute gouty arthritis attack (podagra). The most appropriate acute management is to prescribe non-steroidal anti-inflammatory drugs (NSAIDs) like indomethacin, or colchicine. Oral corticosteroids can also be used if NSAIDs are contraindicated or ineffective. Allopurinol is a urate-lowering therapy and should not be initiated during an acute attack, as it can worsen symptoms by mobilizing uric acid crystals; it is for long-term management once the acute attack has subsided. Joint aspiration and corticosteroid injection are options if only one or two joints are involved and diagnosis is confirmed. Surgical fusion is for end-stage arthritis, not acute management.

Question 14645

Topic: Biology, Genetics & Bone Healing

What is the most common cause of osteonecrosis of the jaw (ONJ) in orthopedic patients?

. Corticosteroid use
. Radiation therapy to the head and neck
. Bisphosphonate therapy
. Infection
. Trauma to the jaw

Correct Answer & Explanation

. Bisphosphonate therapy

Explanation

In orthopedic patients, bisphosphonate therapy is the most common cause of osteonecrosis of the jaw (ONJ), often referred to as bisphosphonate-related osteonecrosis of the jaw (BRONJ). Bisphosphonates, especially IV forms used in metastatic bone disease or osteoporosis, inhibit osteoclast activity, which can impair bone remodeling and healing in the jaw, particularly after dental procedures or trauma. While radiation and infection can cause ONJ, bisphosphonate use is a specific and significant risk factor in the orthopedic population. Corticosteroids and trauma are less commonly implicated as primary causes compared to bisphosphonates.

Question 14646

Topic: Biology, Genetics & Bone Healing

What is the primary mechanism of action of parathyroid hormone (PTH) in bone metabolism?

. Directly stimulates osteoblasts to form new bone.
. Inhibits osteoclast activity, leading to decreased bone resorption.
. Increases serum calcium by promoting bone resorption and renal reabsorption.
. Decreases serum calcium by promoting calcium excretion.
. Promotes calcium absorption from the intestines by inhibiting vitamin D.

Correct Answer & Explanation

. Increases serum calcium by promoting bone resorption and renal reabsorption.

Explanation

Parathyroid hormone (PTH) plays a crucial role in calcium homeostasis. Its primary mechanism of action related to bone metabolism is to increase serum calcium levels. It achieves this by stimulating osteoclasts (indirectly, via osteoblasts) to resorb bone, releasing calcium into the bloodstream. It also increases calcium reabsorption in the renal tubules and stimulates the synthesis of calcitriol (active vitamin D), which in turn enhances intestinal calcium absorption. PTH does not directly stimulate osteoblasts for net new bone formation in a sustained manner, nor does it inhibit osteoclasts or decrease serum calcium.

Question 14647

Topic: Infection, Pharmacology & VTE

What is the most common causative organism for septic arthritis in a healthy adult?

. Staphylococcus aureus
. Streptococcus pyogenes
. Neisseria gonorrhoeae
. Escherichia coli
. Pseudomonas aeruginosa

Correct Answer & Explanation

. Staphylococcus aureus

Explanation

Staphylococcus aureus is the most common causative organism for septic arthritis in healthy adults, accounting for over 80% of cases. Streptococcus pyogenes is also a significant pathogen but less common than S. aureus. Neisseria gonorrhoeae is a common cause in young, sexually active individuals but not the overall most common. E. coli and Pseudomonas aeruginosa are typically seen in immunocompromised patients, those with urinary tract infections, or intravenous drug users.

Question 14648

Topic: Infection, Pharmacology & VTE

A 4-year-old child presents with a high fever, refusal to bear weight, and exquisite pain on passive range of motion of the right hip. Laboratory tests show elevated white blood cell count, ESR, and CRP. Plain radiographs of the hip are normal. What is the most appropriate immediate diagnostic and therapeutic step?

. Administer oral antibiotics and observe.
. Obtain an MRI of the hip.
. Perform a CT scan of the hip.
. Aspirate the hip joint.
. Prescribe NSAIDs and bed rest for transient synovitis.

Correct Answer & Explanation

. Aspirate the hip joint.

Explanation

The clinical presentation (fever, refusal to bear weight, exquisite pain on passive hip ROM, elevated inflammatory markers, normal radiographs) is highly suggestive of septic arthritis of the hip, an orthopedic emergency in children. The most appropriate immediate step is to aspirate the hip joint. This allows for definitive diagnosis (cell count, Gram stain, culture) and therapeutic decompression of the joint. Delay in diagnosis and treatment can lead to rapid cartilage destruction and long-term joint damage. Oral antibiotics are inadequate. MRI and CT can confirm effusions but aspiration is critical for diagnosis and treatment. NSAIDs and bed rest are for transient synovitis, which has lower inflammatory markers and less severe pain on ROM.

Question 14649

Topic: Biology, Genetics & Bone Healing

A 23-year-old man presents with right posterolateral knee pain, worse at night and relieved by NSAIDs. Imaging and histology are shown. The histologic specimen demonstrates a cellular, vascular stroma with plump osteoblasts producing immature woven bone. What is the currently preferred minimally invasive treatment for this lesion?

. Intralesional injection of corticosteroids
. Percutaneous radiofrequency ablation
. En bloc resection with wide margins
. Radiation therapy
. Systemic chemotherapy

Correct Answer & Explanation

. Percutaneous radiofrequency ablation

Explanation

Correct Answer: BThe clinical presentation, imaging (cortically based lytic lesion with surrounding sclerosis/edema), and histology (vascular stroma with osteoblasts and woven bone) are classic for an osteoid osteoma. Percutaneous radiofrequency ablation (RFA), typically under CT guidance, has become the preferred treatment method, offering high success rates with minimal morbidity compared to open surgical excision.

Question 14650

Topic: Biology, Genetics & Bone Healing

A 23-year-old man presents with right posterolateral knee pain that is worse at night and dramatically relieved by NSAIDs. Imaging reveals a well-circumscribed, cortically based lytic lesion in the proximal fibula with surrounding edema. Histology demonstrates a cellular stroma with plump osteoblasts producing immature woven bone. What is the preferred definitive treatment for this condition?

. Wide surgical resection
. Percutaneous radiofrequency ablation
. Intralesional curettage and bone grafting
. Neoadjuvant chemotherapy followed by resection
. Radiation therapy

Correct Answer & Explanation

. Percutaneous radiofrequency ablation

Explanation

Correct Answer: Percutaneous radiofrequency ablationThe clinical presentation (night pain relieved by NSAIDs), radiographic appearance (cortically based lytic lesion with surrounding sclerosis/edema), and histology (plump osteoblasts producing woven bone in a vascular stroma) are classic for an osteoid osteoma. Percutaneous radiofrequency ablation (RFA), typically performed under CT guidance, has become the preferred, minimally invasive treatment of choice for most osteoid osteomas, offering high success rates and low morbidity compared to open surgical resection or curettage.

Question 14651

Topic: Biology, Genetics & Bone Healing

A 23-year-old man presents with right posterolateral knee pain that is worse at night and relieved by NSAIDs. Imaging and histology are provided. The histologic specimen is most likely to demonstrate which of the following?

. Sheets of small round blue cells
. A cellular stroma with plump osteoblasts producing immature woven bone
. Atypical chondrocytes in a lobular pattern
. Multinucleated giant cells in a background of mononuclear stromal cells
. Dead bone with abundant acute inflammatory cells

Correct Answer & Explanation

. A cellular stroma with plump osteoblasts producing immature woven bone

Explanation

Correct Answer: A cellular stroma with plump osteoblasts producing immature woven boneThe clinical presentation, imaging (cortically based lytic lesion with surrounding edema), and histology are diagnostic of an osteoid osteoma. Histologically, it consists of a highly vascularized nidus of interlacing trabeculae of osteoid and woven bone lined by plump, benign osteoblasts.

Question 14652

Topic: Biology, Genetics & Bone Healing

A 23-year-old man complains of right posterolateral knee pain that is worse at night and relieved by NSAIDs. Imaging and histology are shown. The histology demonstrates a cellular, vascular stroma with plump osteoblasts producing immature woven bone. What is the preferred modern treatment modality for this lesion?

. En bloc resection with wide margins
. Percutaneous radiofrequency ablation
. Intralesional curettage and bone grafting
. Neoadjuvant chemotherapy followed by resection
. Radiation therapy

Correct Answer & Explanation

. Percutaneous radiofrequency ablation

Explanation

Correct Answer: BThe clinical presentation (night pain relieved by NSAIDs), radiographic appearance (cortically based lytic lesion with surrounding sclerosis), and histology (vascular stroma with osteoblasts and woven bone) are diagnostic of an osteoid osteoma. The preferred modern treatment for most osteoid osteomas is CT-guided percutaneous radiofrequency ablation, which is minimally invasive and highly effective. En bloc resection is rarely required today.

Question 14653

Topic: Infection, Pharmacology & VTE

A 3-year-old boy presents with a limp and refusal to bear weight on the right leg. He is afebrile but has limited internal rotation. An AP pelvis radiograph is shown. The right teardrop distance measures 11 mm, while the left measures 8 mm. What is the most definitive next step in management to determine the etiology?

. MRI of the pelvis with contrast
. Ultrasound-guided hip aspiration
. Technetium Tc 99m bone scan
. Closed reduction and spica casting
. Intravenous antibiotics and observation

Correct Answer & Explanation

. Ultrasound-guided hip aspiration

Explanation

Correct Answer: BThe widened teardrop distance (a difference of >2 mm compared to the contralateral side) indicates a significant joint effusion. In a child presenting with refusal to bear weight and limited motion, septic arthritis must be urgently ruled out. Hip aspiration is the most definitive test to differentiate septic arthritis from transient synovitis by obtaining fluid for cell count, Gram stain, and culture.

Question 14654

Topic: Biomechanics & Biomaterials

A 19-year-old female collegiate soccer player sustains a noncontact twisting injury to her knee, resulting in an ACL tear. Which of the following factors is considered the most significant modifiable contributor to the higher incidence of ACL tears in female athletes compared to males?

. Intercondylar notch width
. Hormonal fluctuations during the menstrual cycle
. Increased Q-angle and valgus alignment
. Neuromuscular control and landing biomechanics
. Generalized ligamentous laxity

Correct Answer & Explanation

. Neuromuscular control and landing biomechanics

Explanation

Correct Answer: DWhile anatomic (notch width, Q-angle) and hormonal factors have been implicated in the higher rate of ACL tears in females, neuromuscular factors (such as landing biomechanics, decreased hamstring-to-quadriceps strength ratio, and altered muscle activation patterns) are considered the most significant and, importantly, modifiable risk factors. Neuromuscular training programs have been shown to effectively reduce the incidence of ACL tears in female athletes.

Question 14655

Topic: Biology, Genetics & Bone Healing

Bone morphogenetic proteins (BMP-2 and BMP-7) are utilized clinically to promote bone healing and fusion. Upon binding to their respective transmembrane receptors, which intracellular signaling molecules are directly phosphorylated to translocate to the nucleus and induce osteogenic gene expression?

. Wnt and beta-catenin
. Smad 1, 5, and 8
. ERK and MAPK
. RANK and TRAF6
. JAK and STAT

Correct Answer & Explanation

. Smad 1, 5, and 8

Explanation

BMPs exert their osteoinductive effects primarily through the canonical Smad pathway. Binding to serine/threonine kinase receptors leads to the phosphorylation of Smad 1, 5, and 8, which then complex with Smad 4 to regulate target gene transcription.

Question 14656

Topic: Biology, Genetics & Bone Healing

A 40-year-old male sustains a diaphyseal radius and ulna fracture, treated with open reduction and internal fixation using dynamic compression plates to achieve absolute stability. Which primary mode of bone healing is expected to occur in this mechanically rigid environment?

. Endochondral ossification
. Intramembranous ossification
. Primary bone healing via Haversian cutting cones
. Secondary bone healing via cartilaginous callus formation
. Fibrocartilaginous distraction osteogenesis

Correct Answer & Explanation

. Primary bone healing via Haversian cutting cones

Explanation

Rigid internal fixation with absolute stability eliminates interfragmentary motion, facilitating primary (direct) bone healing. This process occurs via Haversian remodeling driven by osteoclastic cutting cones followed by osteoblastic bone deposition, completely bypassing callus formation.

Question 14657

Topic: 1. General Principles & Basic Science

Which of the following is an expected physical finding in an 18-month-old with an undiagnosed unilateral dislocated hip?

. Absence of a femoral pulse on the affected side
. Positive Ortolani test
. Limited abduction on the affected side
. Hyperextension of the affected hip
. Bilateral asymmetric thigh folds

Correct Answer & Explanation

. Limited abduction on the affected side

Explanation

In an 18-month-old with an undiagnosed unilateral dislocated hip, limited abduction on the affected side is a consistent finding due to soft tissue contractures and the abnormal position of the femoral head. The Ortolani test is typically negative by this age as the hip is no longer reducible due to soft tissue adaptations. A femoral pulse should be present. Hyperextension is unlikely; more often, there is a flexion contracture. Asymmetric thigh folds would be expected, but 'bilateral asymmetric' is confusing; it would be unilateral asymmetry.

Question 14658

Topic: 1. General Principles & Basic Science

In a newborn female with a dislocated left hip, what is the expected finding when comparing her left and right hip abduction range of motion?

. Increased abduction on the left side compared to the right.
. Equal abduction on both sides, suggesting bilateral involvement.
. Limited abduction on the left side compared to the right.
. Limited adduction on the left side compared to the right.
. Hyperextension on the left side.

Correct Answer & Explanation

. Limited abduction on the left side compared to the right.

Explanation

A dislocated hip, especially with subsequent muscle contractures, will typically present with limited abduction on the affected side (left in this case) compared to the unaffected side. The abnormal position of the femoral head and adaptive soft tissue changes restrict outward movement. Limited adduction is not a typical finding for a dislocated hip. Increased abduction, equal abduction, or hyperextension are not characteristic of a unilateral dislocated hip.

Question 14659

Topic: 1. General Principles & Basic Science

When correcting a lower extremity angular deformity, if the osteotomy is performed at a level different from the center of rotation of angulation (CORA) but the hinges of the fixator are placed exactly at the CORA, what secondary effect will occur during correction?

. Angulation without translation
. Translation without angulation
. Simultaneous angulation and translation
. Shortening without translation
. Distraction without angulation

Correct Answer & Explanation

. Simultaneous angulation and translation

Explanation

According to Paley's rules of osteotomy, if the osteotomy is outside the CORA but the hinge is at the CORA, the bone will undergo simultaneous angulation and translation to properly realign the mechanical axis.

Question 14660

Topic: 1. General Principles & Basic Science

When utilizing a hexapod circular fixator (e.g., Taylor Spatial Frame) to correct a complex multi-planar tibial deformity, what parameter is essential for the software to establish the 'origin' from which all corrections are calculated?

. The exact diameter of the diaphysis
. The defined reference fragment
. The distance between the master tab and the CORA
. The initial strut lengths only
. The chronologic age of the patient

Correct Answer & Explanation

. The defined reference fragment

Explanation

The reference fragment (usually the proximal or distal ring) must be clearly defined in the software. It dictates the spatial origin, and the software calculates the movement of the non-reference fragment relative to it.

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