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1. General Principles & Basic Science MCQs

Practice Set 629 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 12561

Topic: Biology, Genetics & Bone Healing

Which type of cells are predominantly found in the histological examination of a Non-Ossifying Fibroma?

. Chondrocytes
. Osteoblasts
. Fibroblasts and histiocytes
. Lipocytes
. Plasma cells

Correct Answer & Explanation

. Fibroblasts and histiocytes

Explanation

Non-ossifying fibromas are characterized by a proliferation of benign spindle cells, which are essentially fibroblasts, along with varying numbers of histiocytes (including foam cells) and multinucleated giant cells. Chondrocytes are seen in cartilaginous lesions, osteoblasts in osteogenic lesions, lipocytes in fatty tumors, and plasma cells in inflammatory or plasma cell dyscrasias.

Question 12562

Topic: 1. General Principles & Basic Science

Which imaging modality is best for assessing the extent of cortical involvement and identifying potential intramedullary extension of a Non-Ossifying Fibroma?

. Plain Radiographs
. Bone Scan
. CT Scan
. MRI
. Ultrasound

Correct Answer & Explanation

. CT Scan

Explanation

While plain radiographs are diagnostic, and MRI can show soft tissue involvement and fluid characteristics, a CT scan provides the most accurate and detailed assessment of cortical involvement, internal architecture, and subtle intramedullary extension of bone lesions. It's superior to X-ray for fine bony detail. MRI is excellent for soft tissue, but CT excels in cortical detail. Bone scan shows metabolic activity, and ultrasound is poor for bone lesions.

Question 12563

Topic: Biology, Genetics & Bone Healing

A 10-year-old girl with a 5 cm NOF of the distal femur is noted to have significant bowing of the femur on standing radiographs. This bowing is most likely a result of:

. Rapid growth of the NOF causing mechanical stress.
. Physiological remodeling of bone in response to stress.
. Pathological weakening of the cortex by the NOF, leading to plastic deformation.
. Associated rickets.
. A primary deformity unrelated to the NOF.

Correct Answer & Explanation

. Pathological weakening of the cortex by the NOF, leading to plastic deformation.

Explanation

A large Non-Ossifying Fibroma that significantly weakens the cortex can lead to plastic deformation or bowing of the bone, especially in weight-bearing long bones of children, due to the reduced structural integrity. It's a pathological consequence of the lesion, not rapid growth or normal remodeling. While rickets causes bowing, it would present with other systemic signs and radiographic features.

Question 12564

Topic: 1. General Principles & Basic Science

What is the characteristic location within the bone for a Non-Ossifying Fibroma?

. Subchondral, immediately beneath the articular cartilage.
. Intracortical, within the bone cortex.
. Medullary cavity, centrally located.
. Periosteal surface, external to the cortex.
. Epiphyseal plate.

Correct Answer & Explanation

. Intracortical, within the bone cortex.

Explanation

NOFs are classically described as intracortical lesions that often expand from the cortex into the medullary cavity. They originate in the cortex, typically near the metaphysis. They are not subchondral, purely medullary (though they can extend there), purely periosteal, or within the epiphyseal plate itself.

Question 12565

Topic: 1. General Principles & Basic Science

What is the primary role of MRI in the evaluation of a Non-Ossifying Fibroma?

. Definitive diagnosis, replacing plain radiographs.
. Assessment of marrow involvement, soft tissue extension, and differentiation from other lesions.
. Quantification of bone mineral density.
. Direct visualization of the growth plate to predict limb length discrepancy.
. Evaluation of vascularity for embolization.

Correct Answer & Explanation

. Assessment of marrow involvement, soft tissue extension, and differentiation from other lesions.

Explanation

While plain radiographs are usually diagnostic, MRI is valuable for a more detailed assessment. Its primary roles include evaluating the extent of marrow involvement, detecting any subtle soft tissue extension (though rare for NOF), and helping differentiate NOF from other lesions, particularly those with fluid components like ABCs or UBCs. It also aids in surgical planning for larger lesions. It does not replace plain radiographs for initial diagnosis, quantify BMD, or primarily visualize growth plate for limb length discrepancy (though can see proximity), nor is vascularity its main role for NOF.

Question 12566

Topic: Biology, Genetics & Bone Healing

Which of the following describes the most common histological variant observed within a Non-Ossifying Fibroma?

. Predominantly cartilaginous cells with hyaline matrix.
. Predominantly osteoblasts forming immature woven bone.
. Predominantly fibrous tissue with spindle cells in a storiform pattern.
. Predominantly adipocytes (fat cells).
. Predominantly hematopoietic cells.

Correct Answer & Explanation

. Predominantly fibrous tissue with spindle cells in a storiform pattern.

Explanation

The hallmark histological feature of a Non-Ossifying Fibroma is the proliferation of benign spindle cells (fibroblasts) arranged in a characteristic storiform (pinwheel or cartwheel) pattern. Other cellular components like multinucleated giant cells and foam cells are admixed, but the fibrous tissue is predominant. Cartilaginous, osteoblastic, fatty, or hematopoietic cells are characteristic of other bone lesions.

Question 12567

Topic: Infection, Pharmacology & VTE

A 14-year-old active boy with a previously managed Non-Ossifying Fibroma in the distal tibia presents with new pain at the site. Radiographs show a healed pathological fracture but also a mild increase in lucency at the periphery of the former lesion. What is the most appropriate next step?

. Immediately schedule for repeat curettage and bone grafting.
. Recommend strict non-weight-bearing for 6 months.
. Obtain an MRI to further characterize the lesion and rule out recurrence or other pathology.
. Initiate systemic NSAID treatment for chronic pain.
. Reassure the patient that this is normal healing and no further action is needed.

Correct Answer & Explanation

. Obtain an MRI to further characterize the lesion and rule out recurrence or other pathology.

Explanation

While NOFs have a low recurrence rate after curettage, new pain combined with a change in radiographic appearance (increased lucency) warrants further investigation. An MRI would be the most appropriate next step to assess for any residual or recurrent fibrous tissue, subtle soft tissue changes, or to differentiate from other potential causes of pain. Immediate repeat surgery is premature without further imaging, non-weight-bearing is not diagnostic, and simple reassurance is insufficient given the new symptoms and radiographic changes.

Question 12568

Topic: 1. General Principles & Basic Science

Which of the following describes the typical signal intensity of the sclerotic rim often seen around a Non-Ossifying Fibroma on all MRI sequences (T1, T2)?

. Bright on T1, dark on T2.
. Bright on T2, dark on T1.
. Dark on both T1 and T2.
. Bright on both T1 and T2.
. Variable, depending on fat content.

Correct Answer & Explanation

. Dark on both T1 and T2.

Explanation

The sclerotic rim surrounding a Non-Ossifying Fibroma is composed of dense cortical bone. Dense cortical bone, due to its low water and high mineral content, typically appears dark (low signal intensity) on all MRI sequences, including T1 and T2-weighted images.

Question 12569

Topic: Surgical Anatomy & Approaches

A patient is undergoing biopsy for a suspected metastatic lesion to the sacrum. Which of the following is a critical anatomical structure to be mindful of during the biopsy of the sacrum?

. Sciatic nerve
. Femoral nerve
. Inferior vena cava
. Sural nerve
. Spinal accessory nerve

Correct Answer & Explanation

. Sciatic nerve

Explanation

The sciatic nerve exits the pelvis through the greater sciatic foramen, immediately anterior to the sacrum, and can be at significant risk during sacral biopsies, especially from a posterior or posterolateral approach. Injury to the sciatic nerve can result in devastating motor and sensory deficits. While the femoral nerve is important, it's more anterior. The inferior vena cava is more anterior and superior in the abdomen. The sural and spinal accessory nerves are not in the vicinity of the sacrum.

Question 12570

Topic: 1. General Principles & Basic Science

Which type of knee dislocation (based on displacement direction) is most commonly associated with a popliteal artery injury?

. Anterior
. Posterior
. Medial
. Lateral
. Rotatory

Correct Answer & Explanation

. Anterior

Explanation

Anterior knee dislocations are most commonly associated with popliteal artery injury. This occurs when the tibia is forced anteriorly on the femur, stretching and potentially lacerating the popliteal artery as it is tethered posteriorly by its branches. While all knee dislocations carry a risk of vascular injury, anterior dislocations have the highest incidence (up to 40%). Posterior dislocations also carry a significant risk, but anterior is statistically higher.

Question 12571

Topic: Surgical Anatomy & Approaches

What is the most common nerve injury associated with proximal fibula fractures, particularly those involving the fibular head?

. Sciatic nerve.
. Femoral nerve.
. Superficial peroneal nerve.
. Deep peroneal nerve.
. Common peroneal nerve.

Correct Answer & Explanation

. Common peroneal nerve.

Explanation

The common peroneal nerve courses around the neck of the fibula, making it highly susceptible to injury with fractures of the fibular head or neck. Injury to the common peroneal nerve typically results in a 'foot drop' due to paralysis of the ankle dorsiflexors and evertors, along with sensory loss over the dorsum of the foot and lateral leg. The superficial and deep peroneal nerves are branches of the common peroneal nerve, so an injury to the common peroneal nerve would affect both. Sciatic and femoral nerves are anatomically more proximal.

Question 12572

Topic: Infection, Pharmacology & VTE

Which of the following factors is most strongly associated with an increased risk of DVT/PE in a patient with a lower extremity fracture?

. Younger age (<30 years).
. Early ambulation.
. Presence of an epidural catheter for pain control.
. Traumatic brain injury.
. Prolonged immobilization.

Correct Answer & Explanation

. Prolonged immobilization.

Explanation

Prolonged immobilization, especially of the lower extremity, is a well-established major risk factor for deep vein thrombosis (DVT) and pulmonary embolism (PE) due to venous stasis. Other risk factors include advanced age, malignancy, obesity, history of DVT/PE, and specific fracture types (pelvis, hip). While traumatic brain injury can be associated with hypercoagulability, prolonged immobilization is a more direct and significant factor for DVT/PE in lower extremity trauma. Early ambulation is protective. Epidural catheters do not directly increase DVT/PE risk. Younger age is generally protective.

Question 12573

Topic: 1. General Principles & Basic Science

What is the characteristic clinical presentation of a patient with a ruptured patellar tendon?

. Ability to actively extend the knee against gravity, but with pain.
. Palpable defect below the patella, high-riding patella, and inability to actively extend the knee.
. Palpable defect above the patella, low-riding patella, and inability to actively extend the knee.
. Gross knee instability in all planes.
. Ecchymosis and swelling localized to the popliteal fossa.

Correct Answer & Explanation

. Palpable defect below the patella, high-riding patella, and inability to actively extend the knee.

Explanation

A ruptured patellar tendon results in a loss of continuity of the extensor mechanism of the knee. Clinically, this manifests as a palpable defectbelowthe patella, and due to the unopposed pull of the quadriceps, the patella will appearhigh-riding(patella alta). Crucially, the patient will be unable to actively extend the knee against gravity. A ruptured quadriceps tendon, in contrast, would result in a defectabovethe patella and a low-riding patella (patella baja).

Question 12574

Topic: Infection, Pharmacology & VTE

What is the most sensitive imaging modality for diagnosing osteomyelitis following an open fracture?

. Plain radiographs.
. CT scan.
. MRI with contrast.
. Bone scan (Technetium-99m).
. Indium-111 labeled leukocyte scan.

Correct Answer & Explanation

. Indium-111 labeled leukocyte scan.

Explanation

While MRI with contrast is highly sensitive for soft tissue and bone marrow edema, making it excellent for early osteomyelitis, an Indium-111 labeled leukocyte scan (or combined WBC/bone scan) is often considered the most specific and sensitive imaging modality for diagnosing active infection (osteomyelitis), especially in the presence of hardware or previous surgery, as it specifically targets actively inflamed leukocytes. Plain radiographs are insensitive in early stages. CT is good for bony detail but less for early infection. Bone scans are sensitive but not very specific for infection in the presence of other bone pathology like fractures or hardware.

Question 12575

Topic: Physiology & Rehabilitation

Which of the following is considered a hallmark clinical feature differentiating an intramedullary spinal tumor from an extradural tumor?

. Radicular pain
. Progressive motor weakness
. Early dissociated sensory loss (loss of pain/temp with preserved touch/proprioception)
. Bowel and bladder dysfunction
. Local back pain

Correct Answer & Explanation

. Early dissociated sensory loss (loss of pain/temp with preserved touch/proprioception)

Explanation

Early dissociated sensory loss (syringomyelic pattern), where pain and temperature sensation are lost while touch and proprioception are preserved, is a hallmark feature of intramedullary lesions, especially those causing a syrinx or affecting the spinothalamic tracts crossing in the central cord. This is due to disruption of the decussating spinothalamic fibers. While other symptoms like motor weakness, pain, and bladder dysfunction can occur with any spinal tumor, this specific sensory pattern points strongly to an intramedullary pathology.

Question 12576

Topic: 1. General Principles & Basic Science

What is the most appropriate initial management for an incidental intraoperative dural tear during lumbar decompression?

. Aborting the surgical procedure immediately.
. Closure of the dural defect primarily with suture and/or patch, and observation for CSF leak.
. Proceeding with the decompression and ignoring the defect.
. Placement of a permanent lumbar drain for several weeks post-op.
. Applying fibrin glue without attempting primary repair.

Correct Answer & Explanation

. Closure of the dural defect primarily with suture and/or patch, and observation for CSF leak.

Explanation

The most appropriate initial management for an incidental intraoperative dural tear is primary repair of the defect with fine sutures, often augmented with a muscle patch, fat graft, or dural sealant/glue. This aims to achieve a watertight closure and prevent postoperative cerebrospinal fluid (CSF) leak, fistula, or pseudomeningocele. Aborting the procedure (Option A) is rarely necessary. Ignoring the defect (Option C) is inappropriate and leads to complications. A lumbar drain (Option D) might be used post-repair in certain high-risk situations but is not the primary repair method. Fibrin glue (Option E) is an adjunct, not a substitute for primary repair when feasible.

Question 12577

Topic: 1. General Principles & Basic Science

What is a key anesthetic consideration for patients undergoing elective lumbar decompression, particularly in the elderly?

. Strict avoidance of general anesthesia.
. Maintaining a high mean arterial pressure (MAP) to improve surgical visualization.
. Positioning to minimize abdominal compression, reduce epidural venous bleeding, and optimize hemodynamics.
. Routine use of systemic corticosteroids preoperatively.
. Prolonged immobilization in the operating room to ensure stability.

Correct Answer & Explanation

. Positioning to minimize abdominal compression, reduce epidural venous bleeding, and optimize hemodynamics.

Explanation

Proper positioning, typically in the prone position with careful padding, is crucial to minimize abdominal compression. Abdominal compression increases intra-abdominal pressure, which in turn increases epidural venous pressure and engorgement, leading to increased intraoperative bleeding, obscured surgical field, and potentially higher risks. Minimizing abdominal compression helps reduce venous bleeding and optimize hemodynamics. Options A, B, D, and E are incorrect or not the most critical consideration. General anesthesia is common. Maintaining alowerMAP is sometimes targeted to reduce bleeding, not higher. Systemic corticosteroids are not routine. Prolonged immobilization is necessary, but proper positioning to prevent complications is key.

Question 12578

Topic: 1. General Principles & Basic Science

In the immediate postoperative period after lumbar decompression, what is a primary rehabilitation goal?

. To encourage prolonged bed rest to allow for tissue healing.
. To immediately resume heavy lifting and strenuous activities.
. To educate the patient on proper body mechanics and initiate progressive ambulation.
. To focus solely on pain medication management.
. To apply ice packs continuously for 24 hours.

Correct Answer & Explanation

. To educate the patient on proper body mechanics and initiate progressive ambulation.

Explanation

In the immediate postoperative period after lumbar decompression, a primary rehabilitation goal is to educate the patient on proper body mechanics (e.g., log-rolling for transfers, avoiding excessive twisting/bending) and to initiate progressive ambulation. Early mobilization helps prevent complications and promotes recovery. Prolonged bed rest (Option A) is detrimental. Immediate resumption of strenuous activities (Option B) is inappropriate. Pain management (Option D) is important but not the sole focus of rehabilitation. Ice packs (Option E) may be used but are not a primary rehabilitation goal.

Question 12579

Topic: Infection, Pharmacology & VTE

A patient with a suspected L3-L4 discitis and adjacent vertebral osteomyelitis has negative blood cultures. What is the most appropriate next step for definitive diagnosis?

. Empiric broad-spectrum antibiotic therapy
. Repeat blood cultures weekly
. CT-guided biopsy of the L3-L4 disc space
. Fluoroscopy-guided lumbar puncture
. Positron Emission Tomography (PET) scan

Correct Answer & Explanation

. CT-guided biopsy of the L3-L4 disc space

Explanation

When blood cultures are negative in suspected spinal infection (discitis/osteomyelitis), obtaining tissue for culture and histology is paramount for definitive diagnosis and targeted antibiotic therapy. A CT-guided biopsy of the affected disc space and/or vertebral body is the most appropriate and minimally invasive method to achieve this. Empiric antibiotics without pathogen identification can delay effective treatment and obscure future culture results. Lumbar puncture is for CSF analysis. PET scan helps localize infection but does not provide microbial diagnosis.

Question 12580

Topic: Infection, Pharmacology & VTE

Which feature is more characteristic of pyogenic spinal osteomyelitis/abscess compared to tuberculous spondylitis (Pott's disease)?

. Involvement of multiple contiguous vertebral bodies
. Large paraspinal cold abscesses
. More rapid onset and progression of symptoms
. Prominent kyphotic deformity
. Preservation of disc space in early stages

Correct Answer & Explanation

. More rapid onset and progression of symptoms

Explanation

Pyogenic spinal osteomyelitis and abscesses typically have a more acute or subacute onset with rapid progression of symptoms (days to weeks), including fever, severe pain, and rapid neurological decline. Tuberculous spondylitis (Pott's disease) is characterized by a more indolent, chronic course (months to years), often with gradual onset of pain, constitutional symptoms (weight loss, night sweats), and slow development of kyphosis or neurological deficit. The other options are more characteristic of tuberculous spondylitis.

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