Question 1

When an osteoblastoma occurs in the spine, it can involve all of the following except:

Explanation

When an osteoblastoma occurs in the spine, involvement of the posterior elements of the vertebra is typical and includes: Lamina Pedicles Transverse processes Facets Rib heads adjacent to thoracic vertebrae

Question 2

The proper treatment of a vertebral osteoblastoma includes:

Explanation

Treatment of spinal osteoblastomas usually consists of marginal excision or curettage of the tumor. Local recurrence rates of up to 10% have been observed from some osteoblastomas, however, malignant degeneration is rare. There is no role for radiation or chemotherapy. Radiofrequency ablation has been used successfully for the treatment of osteoid osteomas, but not osteoblastomas.C orrect Answer: Marginal excision/curettage of the tumor

Question 3

Typical histologic features of an osteoblastoma include all of the following except:

Explanation

Histologically osteoblastoma is similar to an osteoid osteoma; its features include: Irregular osteoid arranged haphazardly with rimming by round osteoblasts Loose fibrovascular connective tissue between trabeculae Osteoblasts rimming the trabeculae Vascularized spindle cell stroma Areas of aneurysmal bone cyst formation can be seen

Question 4

What percentage of osteoblastomas occur in the spine:

Explanation

Osteoblastomas are: Osteoblastic bone-forming lesions measuring more than 2 cm in size characterized by marked growth potential Similar in histology and presentation to osteoid osteoma with the main difference being the size of the tumor Most common in the 2nd and 3rd decades of life Twice as common in men than in women Common in the spine: Spinal osteoblastomas account for 40% to 45% of all osteoblastomas Over half of spinal osteoblastomas occur in the lumbar spine

Question 5

Primary spinal tumors account for:

Explanation

Neoplasms of the spine can be broadly categorized into metastatic tumors and primary tumors. Primary spinal tumors are rare and account for 0.04% of all tumors and 10% of all bone tumors.

Question 6

Pain is the most common complaint in patients presenting with a primary spine tumor and is present in which percentage of patients:

Explanation

I. Pain is the most common complaint in patients presenting with a primary spine tumor A. Present in up to 85% of patients B. Typically localized to the site of lesion but can be radicular C . C haracterized as: 1. Progressive 2. Gradual in onset 3. Worse at night 4. Non-mechanical D. Loosely associated with trauma II. Weakness can be seen in up to 42% of patients III. Mass is evident in up to 16% of patients IV. Three percent of patients are asymptomatic V. Other symptoms can include: A. Sensory loss B. Loss of sphincter control

Question 7

Patients presenting with a primary spine tumor most often characterize their pain as:

Explanation

I. Pain is the most common complaint in patients presenting with a primary spine tumor A. Present in up to 85% of patients B. Typically localized to the site of lesion but can be radicular C . Characterized as: 1. Progressive 2. Gradual in onset 3. Worse at night 4. Non-mechanical a. Loosely associated with trauma D. Weakness can be seen in up to 42% of patients E. Mass is evident in up to 16% of patients F. Three percent of patients are asymptomatic G. Other symptoms can include: 1. Sensory loss 2. Loss of sphincter control

Question 8

What percentage of trabecular bone must be destroyed before changes can be seen on plain radiographs:

Explanation

I. Imaging studies used most frequently in the diagnosis of primary spine tumors include: A. Plain radiographs 1. Initial imaging study 2. Recommended for any patient with prolonged back pain (>6 weeks) 3. Identify 30% to 70% of spine tumors at presentation 4. Early lesions difficult to detect because 30% to 50% of trabecular bone must be destroyed before changes can be seen 5. Absence of the pedicle is usually the earliest radiographic sign of vertebral 6. Cortical bone loss easier to detect than destruction of trabecular bone 7. "Winking owl" sign 8. Disk space generally preserved 9. Geographic lesions with well-circumscribed borders suggest a benign tumor 10. Permeative lesions suggest a malignant tumor B. Bone scan 1. Technetium (Tc)-99m 2. C an identify lesions 3 to 18 months before plain radiographs 3. Sensitivity 74%, specificity 81% 4. False negative in up to 60% of patients with multiple myeloma 5. Single photon emission computerized tomography scan can improve both sensitivity (87%) and specificity (91%) 6. When used in combination with gallium scanning, Tc-99 bone scan can help to differentiate between tumors and infections C . Computed tomography/myelography 1. Best test to determine extent of bony destruction 2. Important in surgical planning 3. Myelography usually used only when magnetic resonance imaging (MRI) not possible (danger of complete myelographic block) D. MRI 1. Modality of choice in evaluating tumors of the spine 2. Noninvasive 3. Allows direct visualization of entire spinal cord 4. Visualization of soft tissues 5. Sensitivity 92%, specificity 90% 6. Additional lesions in 20% to 24%, and 10% will have multiple levels of cord compression

Question 9

Which of the following is considered to be a malignant primary spine tumor:

Explanation

I. Primary benign tumors of the spine are: A. Slow-growing B. Well-circumscribed C . Usually occur in patients younger than 21 years of age D. Involve the vertebral body and posterior elements of the spine 1. Overall slight predilection for the posterior elements 2. Location of tumor is an important factor in determining the type of tumor E. Examples include: 1. Osteochondroma 2. Osteoid osteoma 3. Osteoblastoma 4. Aneurysmal bone cyst 5. Giant cell tumor 6. Eosinophilic granuloma II. Primary malignant tumors of the spine are: A. Fast-growing B. Permeative C . Usually occur in patients older than 21 years of age D. Examples include: 1. Multiple myeloma/solitary plasmacytoma 2. Osteosarcoma 3. C hondrosarcoma 4. Ewing's sarcoma/primitive neuroectodermal tumor 5. Chordoma 6. Lymphoma

Question 10

Which of the following tumors is considered to be a benign primary spine tumor:

Explanation

I. Primary benign tumors of the spine are: A. Slow-growing B. Well-circumscribed C . Usually occur in patients younger than 21 years of age D. Involve the vertebral body and posterior elements of the spine 1. Overall slight predilection for the posterior elements 2. Location of tumor is an important factor in determining the type of tumor E. Examples include: 1. Osteochondroma 2. Osteoid osteoma 3. Osteoblastoma 4. Aneurysmal bone cyst 5. Giant cell tumor 6. Eosinophilic granuloma II. Primary malignant tumors of the spine are: A. Fast-growing B. Permeative C . Usually occur in patients older than 21 years of age D. Examples include: 1. Multiple myeloma/solitary plasmacytoma 2. Osteosarcoma 3. C hondrosarcoma 4. Ewing's sarcoma/primitive neuroectodermal tumor 5. Chordoma 6. Lymphoma

Question 11

Primary malignant tumors of the spine have which of the following characteristics:

Explanation

I. Primary benign tumors of the spine are: A. Slow-growing B. Well-circumscribed C . Usually occur in patients younger than 21 years of age D. Involve the vertebral body and posterior elements of the spine 1. Overall slight predilection for the posterior elements 2. Location of tumor is an important factor in determining the type of tumor E. Examples include: 1. Osteochondroma 2. Osteoid osteoma 3. Osteoblastoma 4. Aneurysmal bone cyst 5. Giant cell tumor 6. Eosinophilic granuloma II. Primary malignant tumors of the spine are: A. Fast-growing B. Permeative C . Usually occur in patients older than 21 years of age D. Examples include: 1. Multiple myeloma/solitary plasmacytoma 2. Osteosarcoma 3. C hondrosarcoma 4. Ewing's sarcoma/primitive neuroectodermal tumor 5. C hordoma 6. Lymphoma

Question 12

All of the following are elements of the lateral mass of cervical spinal segments except:

Explanation

The lateral mass of the cervical spinal segments includes the inferior and superior articulating processes, the transverse foramen, and the transverse process. The spinous process is not an element of the lateral mass.C orrect Answer: Spinous process

Question 13

Advantages of minimally invasive lumbar interbody fusion over traditional open interbody fusion include:

Explanation

Minimally invasive lumbar interbody fusion involves less muscle dissection and trauma than traditional open approaches. The surgical exposure is more limited, though, and there is no evidence to date of minimally invasive techniques providing better fusion rates or lowered risk of nerve root injury.

Question 14

Which of the following statements is true regarding minimally invasive posterior lumbar interbody fusion:

Explanation

Intraoperative fluoroscopy or radiography is vital for the proper identification of lumbar level and vertebral structures in minimally invasive posterior lumbar interbody fusions. While endoscopic assistance has been well described as a method of minimally invasive fusion, it is not vital to this technique. There is no evidence of increased risk of nerve root injury with minimally invasive techniques, and it is possible to internally fixate the lumbar segment with pedicle screws through minimally invasive techniques.

Question 15

A 21-year-old man presented to the emergency department after sustaining a low-velocity gunshot wound to his midback resulting in grade 0 (out of 5) weakness in his quadriceps and tibialis anterior muscles. His extensor hallucis longus and gastrocnemius/soleus muscles were grade 3 (out of 5) bilaterally. His sensation remained intact. An intradural bullet fragment was seen at T12. No fracture was seen on computed tomography (C T) scan. Management should consist of:

Explanation

In complete and incomplete lesions from T12 to L4, removal of the bullet fragment from the canal has been associated with significant motor recovery. This improvement is not seen in other regions of the spine. High-dose steroids have not been shown to offer improvement in patients with spinal cord injury after a gunshot wound, and the complications of high-dose steroids have been documented in this population. The majority of gunshot wounds to the spine are stable injuries. This patientâ s C T scan does not demonstrate any instability. Therefore, neither nonoperative (eg, TLSO bracing) nor operative (instrumented fusion) stabilization is indicated. While infection after transalimentary bullet wounds to the spine is a well-documented complication, this patientâ s injury was sustained from the back, thereby avoiding the alimentary canal and obviating the need for intravenous antibiotics.

Question 16

In relation to the lumbar pedicle, the exiting nerve root is found:

Explanation

The exiting nerve root is found traversing immediately inferior to the pedicle.

Question 17

Regarding the anatomy of the lumbar pedicle, which of the following statements is true:

Explanation

The lumbar pedicle is the bony bridge that connects the posterior vertebral elements to the anterior body. The pedicle is located at the base of the superior facet, at the origin of the transverse process. The exiting nerve root traverses immediately inferior to the superior segment pedicle, and the pedicle joins the vertebral body at its superior half.

Question 18

Which of the following serves as the best landmark for proper screw entry into the lumbar pedicle:

Explanation

The junction of the transverse process and the inferior facet represents the most appropriate entry point of the pedicle screw. This junction directly overlies the pedicle and ensures safe placement through the pedicle and into the vertebral body.

Question 19

A potential major complication of lumbar pedicle screws is:

Explanation

The exiting nerve root traverses immediately medial then caudal to the lumbar pedicle. Therefore, a screw that breaks out medially or inferiorly from the pedicle is a potential risk to the nerve root.

Question 20

Common indications for lumbar pedicle screw fixation include:

Explanation

after trauma to the lumbar spine Common indications for pedicle screw fixation include rigid stabilization for patients undergoing arthrodesis or interbody fusion, correction of deformity, and stabilization after trauma.

Question 21

A 22-year-old male presents with chronic, dull back pain that is not relieved by NSAIDs. Imaging reveals a 3.5 cm expansile radiolucent lesion in the posterior elements of L3. What is the most likely diagnosis?

Explanation

Osteoblastomas are typically larger than 2 cm and usually occur in the posterior elements of the spine. Unlike osteoid osteomas, the pain is less likely to be strictly nocturnal and is poorly relieved by NSAIDs.

Question 22

Aggressive osteoblastomas are distinguished from conventional osteoblastomas primarily by which histologic feature?

Explanation

Aggressive osteoblastomas are characterized by the presence of plump, epithelioid osteoblasts. Despite their aggressive local behavior, they lack the atypical mitoses and destructive permeation seen in osteosarcoma.

Question 23

Secondary aneurysmal bone cysts (ABCs) are most frequently associated with which of the following underlying primary bone tumors?

Explanation

Secondary ABCs can develop in the setting of other primary bone tumors, most notably giant cell tumors, chondroblastomas, and osteoblastomas. Identifying the underlying precursor lesion is critical for appropriate surgical management.

Question 24

A 16-year-old boy presents with a painful, rigid thoracic scoliosis. Imaging confirms an osteoid osteoma in the T8 vertebra. Which of the following best describes the typical curve pattern in relation to the lesion?

Explanation

In spinal osteoid osteomas, muscle spasm typically causes the spine to curve away from the lesion, placing the tumor on the concavity of the scoliotic curve. Excision of the nidus usually leads to resolution of the scoliosis if treated within 15 months of onset.

Question 25

Unlike osteoblastoma, which prefers the posterior elements, Giant Cell Tumor (GCT) of the spine most commonly originates in which anatomic location?

Explanation

Giant Cell Tumors of the spine predominantly affect the vertebral body, often in the sacral region. This contrasts with osteoid osteomas, osteoblastomas, and ABCs, which typically arise in the posterior elements.

Question 26

A 35-year-old female presents with an unresectable giant cell tumor of the sacrum. Which targeted pharmacologic therapy is most appropriate to induce tumor consolidation?

Explanation

Denosumab is a monoclonal antibody against RANKL, which is overexpressed by the neoplastic stromal cells of GCT. It prevents osteoclast-like giant cell formation and induces profound tumor bone consolidation.

Question 27

A 55-year-old male presents with bowel and bladder dysfunction. MRI shows a destructive midline mass in the sacrum. Biopsy reveals cells with abundant bubbly, vacuolated cytoplasm. What is the diagnosis?

Explanation

Chordomas are locally aggressive malignant tumors arising from notochordal remnants, most commonly in the sacrum and clivus. Histology classically shows physaliferous cells with bubbly, vacuolated cytoplasm.

Question 28

A 6-year-old boy presents with back pain. Radiographs demonstrate a symmetrically flattened vertebral body (vertebra plana) at T10 with preserved adjacent disc spaces. What is the most likely diagnosis?

Explanation

Langerhans cell histiocytosis (eosinophilic granuloma) is the classic cause of vertebra plana in young children. The adjacent disc spaces are characteristically preserved, unlike in infectious disciitis.

Question 29

An asymptomatic 50-year-old woman undergoes a lumbar spine X-ray revealing prominent vertical trabeculae in the L2 vertebral body. Axial CT shows a 'polka-dot' appearance. What is the recommended management?

Explanation

The classic 'corduroy cloth' (vertical striations) on X-ray and 'polka-dot' sign on CT are pathognomonic for a vertebral hemangioma. Most are benign, completely asymptomatic, and require only observation.

Question 30

Which of the following scoring systems is specifically designed to estimate survival in patients with spinal metastatic disease to guide surgical decision-making?

Explanation

The Tokuhashi score estimates life expectancy in patients with spinal metastases based on performance status, primary tumor site, and other metastases. The SINS system evaluates mechanical stability, not primarily survival.

Question 31

A 65-year-old male presents with a pathologic compression fracture of L4. Laboratory tests show a monoclonal gammopathy. Which imaging modality is least likely to show increased uptake in the affected vertebra?

Explanation

Multiple myeloma and solitary plasmacytoma are characterized by purely osteolytic lesions with minimal reactive bone formation. Consequently, a standard Technetium-99m bone scan is often falsely negative (cold).

Question 32

When an osteoid osteoma is situated in the lumbar pedicle near the neural foramen, what is a common initial misdiagnosis due to its clinical presentation?

Explanation

Osteoid osteomas in the lumbar spine can cause severe localized inflammation, leading to adjacent nerve root irritation. This often presents as referred pain down the leg, clinically mimicking sciatica from a disc herniation.

Question 33

According to Enneking's principles of tumor resection, what is the most appropriate surgical treatment for an aggressive (Enneking Stage 3) osteoblastoma of the spine?

Explanation

Aggressive osteoblastomas (Stage 3) have a high rate of local recurrence and can behave unpredictably. En bloc resection with marginal or wide margins is recommended to minimize recurrence, provided neurologic morbidity is acceptable.

Question 34

A 72-year-old male with a long history of Paget's disease develops worsening pain and a rapidly enlarging mass in his pelvis. What is the most likely malignant transformation?

Explanation

Paget's disease carries an approximately 1% risk of malignant transformation. Secondary osteosarcoma is the most common malignancy and carries a significantly worse prognosis than primary osteosarcoma in younger patients.

Question 35

Primary aneurysmal bone cysts (ABCs) are neoplastic lesions driven by a specific genetic translocation. Which of the following genes is typically rearranged in primary ABCs?

Explanation

Primary ABCs are characterized by a t(16;17) translocation that causes upregulation of the USP6 gene. This true neoplastic nature distinguishes them from secondary ABCs, which lack this mutation.

Question 36

Which of the following factors contributes the highest number of points to the Spine Instability Neoplastic Score (SINS)?

Explanation

In the SINS criteria, radiographic alignment showing subluxation or translation contributes 4 points, which is the highest single scoring category. A total score of 13-18 indicates instability warranting surgical consultation.

Question 37

What is the most critical factor in preventing local recurrence of a sacral chordoma following surgical management?

Explanation

Chordomas are notoriously chemoresistant and radioresistant. Complete en bloc excision with wide, negative margins is the most important factor in preventing local recurrence and achieving long-term survival.

Question 38

Which of the following histologic features is most reliable for differentiating an aggressive osteoblastoma from a well-differentiated osteosarcoma?

Explanation

Osteosarcomas classically demonstrate a destructive, permeative growth pattern invading the surrounding host trabeculae. In contrast, even aggressive osteoblastomas tend to have a distinct border and push rather than permeate host bone.

Question 39

A 14-year-old girl has a large, expansile aneurysmal bone cyst in the posterior elements of C5 causing neck pain but no neurologic deficit. What is the most appropriate initial surgical management?

Explanation

Preoperative embolization significantly reduces intraoperative blood loss for spinal ABCs. Extended intralesional curettage with high-speed burring and bone grafting achieves a low recurrence rate while preserving spinal stability.

Question 40

A 12-year-old boy presents with progressive back pain and fever. MRI shows a destructive mass in the L2 vertebral body with a large paraspinal soft tissue component. Biopsy shows small round blue cells expressing CD99. What is the most common initial treatment?

Explanation

Ewing sarcoma is a highly chemosensitive, systemic disease. The standard of care begins with neoadjuvant multi-agent chemotherapy, followed by local control (surgery or radiation), and subsequent adjuvant chemotherapy.

Question 41

A 22-year-old male presents with dull, aching back pain that is not completely relieved by NSAIDs. Imaging reveals an expansile, radiolucent lesion measuring 3.5 cm in the posterior elements of L3. Histology shows disorganized osteoid surrounded by plump osteoblasts. Which of the following differentiates this lesion from an osteoid osteoma?

Explanation

Osteoblastoma and osteoid osteoma share similar histologic features, including vascular connective tissue and woven bone lined by osteoblasts. They are primarily distinguished by size, with osteoblastoma defined as being larger than 2 cm.

Question 42

A 16-year-old boy presents with right thigh pain that is worse at night and dramatically relieved by ibuprofen. Plain radiographs show a dense cortical sclerosis with a 7-mm central radiolucent nidus. The intense pain associated with this lesion is primarily mediated by local production of which of the following?

Explanation

Osteoid osteomas produce high levels of prostaglandins, specifically Prostaglandin E2, which is responsible for the characteristic severe, nocturnal pain. NSAIDs provide dramatic relief by inhibiting cyclooxygenase and subsequent prostaglandin synthesis.

Question 43

A 14-year-old female presents with an expansile, eccentric lytic lesion in the distal femur metaphysis. MRI shows multiple fluid-fluid levels. Biopsy confirms an aneurysmal bone cyst (ABC). Primary ABCs are characterized by a genetic rearrangement involving which of the following genes?

Explanation

Primary aneurysmal bone cysts frequently demonstrate rearrangements of the USP6 gene on chromosome 17p13. This genetic marker helps differentiate primary ABCs from secondary ABCs or other lytic bone lesions.

Question 44

An 18-year-old female presents with a rigid, painful thoracic scoliosis. An osteoid osteoma is identified in the spine. Which of the following best describes the typical relationship between the lesion and the scoliotic curve?

Explanation

Spinal osteoid osteomas typically present with a painful, rigid scoliosis. The lesion is almost always located in the posterior elements on the concave side of the apex of the curve due to asymmetric muscle spasms.

Question 45

A 32-year-old female undergoes curettage of an epiphyseal lytic lesion in the proximal tibia. Histology shows numerous multinucleated giant cells in a background of mononuclear stromal cells. If systemic therapy is required for unresectable disease, which cell surface receptor is targeted by the most appropriate pharmacological agent?

Explanation

The diagnosis is a giant cell tumor of bone. Denosumab, a monoclonal antibody, targets RANKL expressed by the neoplastic mononuclear stromal cells, preventing the recruitment and activation of osteoclast-like giant cells.

Question 46

A 15-year-old male presents with chronic knee pain. Radiographs reveal a well-circumscribed, 1.5 cm radiolucent lesion in the epiphysis of the proximal tibia with a thin sclerotic rim. Histological examination reveals chondroblasts and "chicken-wire" calcification. What is the most appropriate definitive management?

Explanation

Chondroblastoma is a benign cartilage tumor characteristically located in the epiphysis of skeletally immature patients. The standard treatment is extended intralesional curettage, burring, and bone grafting, which provides excellent local control.

Question 47

A 9-year-old girl is evaluated for a shepherd's crook deformity of the proximal femur, multiple cafe-au-lait spots with irregular borders, and precocious puberty. Which of the following mutations is responsible for this condition?

Explanation

The patient has McCune-Albright syndrome, characterized by polyostotic fibrous dysplasia, cafe-au-lait macules, and endocrine abnormalities. It is caused by a somatic, post-zygotic activating mutation in the GNAS1 gene leading to increased intracellular cAMP.

Question 48

A 5-year-old boy presents with anterior bowing of his tibia. Radiographs demonstrate a multilocular, lucent lesion within the anterior cortex of the tibial diaphysis. Biopsy shows fibrous tissue with spicules of woven bone lined by osteoblasts. Which of the following malignant tumors is most closely associated with this condition and must be ruled out?

Explanation

Osteofibrous dysplasia (Campanacci disease) typically affects the anterior tibial cortex in children under 10. It is histologically and clinically linked to adamantinoma, a low-grade malignant bone tumor that must be excluded via biopsy.

Question 49

A 45-year-old male undergoes MRI of the shoulder for rotator cuff pathology, which incidentally reveals a 4 cm cartilage-type lesion in the proximal humerus. Which of the following radiographic features is most suggestive of a low-grade chondrosarcoma rather than a benign enchondroma?

Explanation

Differentiating benign enchondromas from low-grade chondrosarcomas is challenging. Pain, cortical thickening, periosteal reaction, and deep endosteal scalloping (greater than two-thirds of the cortex) strongly favor chondrosarcoma.

Question 50

A 7-year-old boy presents with localized pain and swelling over the clavicle. Radiographs show a lytic, poorly marginated lesion with periosteal reaction. Biopsy reveals Langerhans cells admixed with eosinophils. Electron microscopy of the diagnostic cells would most likely demonstrate which of the following?

Explanation

Eosinophilic granuloma is a localized form of Langerhans cell histiocytosis. Diagnosis is confirmed by the presence of S-100 and CD1a positive Langerhans cells, which uniquely contain tennis-racket shaped Birbeck granules on electron microscopy.

Question 51

A 12-year-old boy has an incidental finding of an eccentric, multiloculated, radiolucent lesion with a sclerotic rim in the distal femoral metaphysis following minor trauma. He is asymptomatic. Which of the following is the most appropriate management?

Explanation

The radiographic findings are classic for a non-ossifying fibroma (NOF), a benign, self-limiting fibro-osseous defect. Because it is asymptomatic and an incidental finding, reassurance and observation are indicated as these lesions typically ossify and resolve after skeletal maturity.

Question 52

A secondary aneurysmal bone cyst (ABC) is most commonly found in association with which of the following primary benign bone tumors?

Explanation

Secondary ABCs account for up to 30% of all ABCs and are engrafted on a preexisting bone lesion. They are most frequently associated with giant cell tumors, chondroblastomas, and osteoblastomas.

Question 53

A 9-year-old boy presents with arm pain after throwing a baseball. Radiographs reveal a pathologic fracture through a centrally located, completely lytic lesion in the proximal humerus metaphysis. A "fallen leaf" sign is noted. What is the most appropriate initial management for this patient?

Explanation

The patient has a unicameral bone cyst (UBC) complicated by a pathologic fracture, evidenced by the pathognomonic "fallen leaf" sign. Initial management is immobilization to allow fracture healing, which may occasionally lead to spontaneous obliteration of the cyst.

Question 54

A 24-year-old male requires surgical excision of an aggressive spinal osteoblastoma involving the C4 lamina and pedicle. Which of the following represents the most significant surgical challenge and typical reason for recurrence in these lesions?

Explanation

Spinal osteoblastomas are highly vascular and expand into the epidural space, making complete excision technically challenging due to profuse bleeding and proximity to the spinal cord or nerve roots. Incomplete resection is the primary cause of local recurrence.

Question 55

Which of the following benign bone lesions carries the highest inherent risk of malignant transformation without any prior history of radiation therapy?

Explanation

Multiple hereditary exostoses (MHE) is characterized by numerous osteochondromas. Depending on the phenotype, the lifetime risk of malignant transformation to secondary chondrosarcoma is approximately 1-5%, which is significantly higher than the other listed benign lesions.

Question 56

Radiofrequency ablation (RFA) is the treatment of choice for most osteoid osteomas. In which of the following anatomical locations is RFA generally considered contraindicated or highest risk, frequently necessitating open surgical resection?

Explanation

RFA relies on thermal necrosis to destroy the nidus. It is generally contraindicated or highly hazardous if the lesion is within 1 cm of critical structures like the spinal cord or major motor nerves, due to the high risk of thermal neural injury.

Question 57

A 60-year-old male presents with a large destructive mass in the sacrum. Biopsy reveals cells with abundant bubbly, vacuolated cytoplasm arranged in cords. What is the most likely diagnosis?

Explanation

Chordomas are locally aggressive malignant tumors arising from notochord remnants, classically found in the sacrum or clivus. The hallmark histologic finding is physaliferous cells, which have abundant bubbly, vacuolated cytoplasm.

Question 58

A 14-year-old female presents with back pain and a lytic lesion involving the posterior elements of L3. An MRI shows multiple fluid-fluid levels. What is the most appropriate initial surgical management for a symptomatic, locally aggressive lesion?

Explanation

Aneurysmal bone cysts (ABCs) in the spine typically involve the posterior elements and show fluid-fluid levels on MRI. Due to their high vascularity, preoperative embolization followed by aggressive intralesional curettage is the standard treatment to minimize blood loss.

Question 59

A 12-year-old boy presents with painful thoracic scoliosis. Imaging reveals a 1.2 cm radiolucent nidus surrounded by reactive sclerosis in the right T8 pedicle. Which of the following best describes the relationship of the lesion to the spinal curve?

Explanation

In osteoid osteoma of the spine, asymmetric muscle spasms cause a functional scoliosis. The lesion is characteristically located at the apex of the curve on the concave side.

Question 60

A 55-year-old male is diagnosed with a primary conventional chondrosarcoma of the T10 vertebral body. What is the most appropriate definitive management?

Explanation

Conventional chondrosarcoma is highly resistant to both chemotherapy and radiation therapy. The only potential for cure or long-term disease-free survival is en bloc wide surgical resection with negative margins.

Question 61

A 65-year-old man with a history of renal cell carcinoma presents with acute myelopathy due to a pathologic fracture of L2. Decompression and stabilization are planned. Which preoperative intervention is most critical?

Explanation

Renal cell carcinoma and thyroid carcinoma metastases are notoriously hypervascular. Preoperative selective arterial embolization is highly recommended to significantly reduce intraoperative blood loss during surgical decompression.

Question 62

A 6-year-old child presents with mid-back pain. Radiographs reveal a uniform collapse of the T7 vertebral body (vertebra plana) with adjacent disc spaces preserved. What is the most likely diagnosis?

Explanation

Eosinophilic granuloma (Langerhans cell histiocytosis) classically presents in children as vertebra plana, where the vertebral body collapses completely but the adjacent intervertebral disc spaces are notably preserved.

Question 63

A 35-year-old woman presents with a destructive lytic lesion in the sacrum. Biopsy reveals multinucleated giant cells intermixed with mononuclear stromal cells. The stromal cells are positive for H3F3A mutation. What is the most effective medical adjunct to surgery?

Explanation

The diagnosis is a Giant Cell Tumor (GCT) of bone, confirmed by the H3F3A mutation in the neoplastic stromal cells. Denosumab, a RANKL inhibitor, is highly effective in downregulating the osteoclast-like giant cells and creating a calcified rim, aiding in surgical resection.

Question 64

A 68-year-old male presents with generalized bone pain and a lytic lesion in the L4 vertebral body. Laboratory testing reveals hypercalcemia, anemia, and renal insufficiency. Serum protein electrophoresis shows an M-spike. Which of the following is most likely to be elevated in the patient's urine?

Explanation

The patient's presentation (CRAB symptoms: hyperCalcemia, Renal insufficiency, Anemia, Bone lesions) is classic for multiple myeloma. Bence Jones proteins (free light chains) are typically elevated and found in the urine of these patients.

Question 65

Which of the following characteristics best differentiates an osteoblastoma from an osteoid osteoma?

Explanation

Osteoblastoma and osteoid osteoma share similar histology. However, osteoblastomas are distinguished by being larger than 2 cm, having progressive rather than self-limiting growth, and typically exhibiting pain that is less responsive to NSAIDs.

Question 66

An incidental finding on a lumbar radiograph of a 50-year-old female shows coarse vertical trabeculations in the L3 vertebral body, giving a 'corduroy' appearance. Axial CT shows a 'polka dot' pattern. What is the recommended management?

Explanation

The imaging findings of a 'corduroy' sign on plain radiographs and a 'polka dot' sign on axial CT are pathognomonic for a vertebral hemangioma. Since it is an asymptomatic incidental finding without aggressive features, observation is the only required management.

Question 67

A 10-year-old boy presents with progressive back pain, fever, and a sacral mass. Biopsy reveals sheets of uniform small round blue cells. Immunohistochemistry is strongly positive for CD99 and genetic testing shows a t(11;22) translocation. What is the primary treatment modality?

Explanation

The diagnosis is Ewing sarcoma, indicated by the small round blue cells, CD99 positivity, and t(11;22) translocation. It is a systemic disease requiring neoadjuvant multi-agent chemotherapy followed by local control with surgery and/or radiation.

Question 68

A 75-year-old male with long-standing Paget's disease of bone develops acute, severe back pain and a rapidly enlarging mass in the lumbar spine. Serum alkaline phosphatase is markedly elevated. Biopsy confirms malignancy. What is the most likely diagnosis?

Explanation

Malignant transformation in Paget's disease occurs in about 1% of cases, typically presenting with new, severe pain and a rapidly growing mass. Secondary osteosarcoma is the most common pathology and carries a very poor prognosis.

Question 69

Which of the following is NOT a component of the Spinal Instability Neoplastic Score (SINS) used to evaluate metastatic spinal lesions?

Explanation

The SINS score evaluates mechanical instability using six criteria: location, pain, bone lesion quality, radiographic spinal alignment, degree of vertebral body collapse, and posterolateral involvement. Patient life expectancy is part of the Tokuhashi or Tomita scores, not SINS.

Question 70

A 50-year-old male presents with a solitary lytic lesion in the T11 vertebral body. Biopsy confirms a monoclonal proliferation of plasma cells. Bone marrow biopsy is negative elsewhere, and skeletal survey shows no other lesions. What is the standard definitive treatment for this isolated lesion?

Explanation

A solitary bone plasmacytoma is a localized proliferation of malignant plasma cells without systemic myeloma. The treatment of choice is local definitive radiation therapy, to which the tumor is highly sensitive.

Question 71

A 60-year-old woman presents with a solitary metastatic spine lesion from follicular thyroid carcinoma at L1, causing mechanical instability but no neurological deficit. She has a life expectancy of >5 years. What is the most appropriate surgical strategy?

Explanation

In a patient with a long life expectancy, an isolated spinal metastasis from a relatively radioresistant tumor (like thyroid or renal cell carcinoma), and mechanical instability, en bloc resection is indicated. This provides the best chance for local disease control and prolonged survival.

Question 72

A 20-year-old male with multiple hereditary exostoses (MHE) presents with slowly progressive myelopathy. MRI shows a bony outcropping from the C2 lamina compressing the spinal cord. The cartilage cap thickness is 0.5 cm. What is the most likely diagnosis and appropriate management?

Explanation

Spinal osteochondromas can cause compressive myelopathy, especially in patients with MHE. A cartilage cap thickness of <1.5-2.0 cm in an adult suggests a benign lesion, and simple excision with decompression is the standard treatment.

Question 73

A 58-year-old female with metastatic breast cancer to the thoracic spine presents with confusion, abdominal pain, and polyuria. Laboratory tests show a serum calcium of 13.5 mg/dL. What is the primary mediator of this paraneoplastic syndrome?

Explanation

Hypercalcemia of malignancy in solid tumors (like breast and lung cancer) is most commonly mediated by the secretion of parathyroid hormone-related protein (PTHrP). PTHrP mimics PTH, leading to increased bone resorption and renal calcium reabsorption.

Question 74

A 45-year-old male presents with back pain and B symptoms. MRI of the lumbar spine shows extensive marrow replacement of L3 with a large, bulky paraspinal soft tissue mass, but minimal cortical bone destruction. What is the most likely diagnosis?

Explanation

Primary lymphoma of bone characteristically presents with a large soft-tissue mass out of proportion to the degree of cortical bone destruction. It permeates the marrow space through Haversian canals without extensively destroying the cortex.

Question 75

A 16-year-old male presents with a dull ache in his posterior neck. Radiographs show a 2.5 cm radiolucent lesion with a sclerotic rim in the C4 lamina. Histology shows interlacing woven bone trabeculae lined by a single layer of plump osteoblasts. What is the most likely diagnosis?

Explanation

The clinical presentation, size (>2 cm), location in the posterior elements of the spine, and histology are characteristic of an osteoblastoma. Osteoid osteomas are histologically identical but are typically less than 1.5 to 2 cm in diameter.

Question 76

Which of the following is a key clinical differentiating factor between an osteoid osteoma and an osteoblastoma?

Explanation

Unlike osteoid osteomas, the pain associated with osteoblastoma is usually a dull ache that is not classically relieved by NSAIDs. Osteoblastomas also tend to be larger, occur more frequently in the spine, and are more likely to cause neurologic deficits.

Question 77

A secondary aneurysmal bone cyst (ABC) is most commonly associated with which of the following underlying benign bone tumors?

Explanation

Approximately 30% of aneurysmal bone cysts are secondary lesions. The most common underlying precursor lesions are giant cell tumors, osteoblastomas, and chondroblastomas.

Question 78

A 30-year-old female presents with a sacral mass causing bowel dysfunction. Biopsy reveals multinucleated giant cells and mononuclear stromal cells. If surgical resection carries unacceptable morbidity, which targeted medical therapy is most appropriate?

Explanation

Denosumab is a monoclonal antibody against RANKL, which is heavily expressed by the neoplastic mononuclear stromal cells in giant cell tumors. It prevents the activation of osteoclast-like giant cells and is FDA-approved for unresectable GCTs.

Question 79

A 9-year-old boy presents with back pain. Radiographs reveal a completely collapsed vertebral body (vertebra plana) at T8 with preserved adjacent disc spaces. Laboratory tests are normal. What is the most likely diagnosis?

Explanation

Vertebra plana (a uniformly collapsed vertebral body) in a child is a classic radiographic hallmark of eosinophilic granuloma (Langerhans cell histiocytosis). The intervertebral disc spaces are characteristically preserved.

Question 80

Radiofrequency ablation (RFA) is considered the treatment of choice for most osteoid osteomas. What is the generally accepted minimum safe distance from the spinal cord or nerve roots to prevent thermal injury during RFA?

Explanation

To safely perform RFA for spinal osteoid osteomas without damaging neural elements, the lesion should generally be at least 10 mm away from the spinal cord and nerve roots. Closer proximity significantly increases the risk of thermal neuropraxia or permanent damage.

Question 81

Which of the following histologic features is pathognomonic for a chordoma?

Explanation

Chordomas are malignant tumors arising from notochordal remnants, most commonly found in the sacrum and clivus. They are histologically characterized by physaliferous cells, which are large cells with vacuolated, bubbly cytoplasm.

Question 82

A 65-year-old man with known Paget's disease presents with new, severe, unrelenting thigh pain. Radiographs show a destructive, permeative lesion in the femoral diaphysis. What is the most likely diagnosis?

Explanation

New-onset severe pain or swelling in a bone affected by Paget's disease should raise high suspicion for malignant transformation. Secondary osteosarcoma is the most common and carries a very poor prognosis.

Question 83

What is the primary pathophysiologic mechanism of pain generated by an osteoid osteoma?

Explanation

The nidus of an osteoid osteoma produces high levels of Prostaglandin E2 (PGE2), which causes severe, deep, aching pain. This is the physiologic basis for why NSAIDs and aspirin are highly effective at relieving the pain.

Question 84

A 45-year-old male presents with an incidental finding of a heavily calcified cartilage tumor within the proximal femur. He is asymptomatic. Imaging shows endosteal scalloping of less than one-third of the cortical thickness. What is the most appropriate management?

Explanation

This presentation is typical for a benign enchondroma, given the lack of pain and minimal endosteal scalloping. Asymptomatic enchondromas do not require surgical intervention and should be managed with observation.

Question 85

An aggressive variant of osteoblastoma, which is locally destructive and often confused with osteosarcoma, typically exhibits which of the following histologic characteristics?

Explanation

Aggressive (or epithelioid) osteoblastoma is characterized by large, plump, epithelioid osteoblasts with prominent nucleoli. Despite its atypical appearance and locally aggressive behavior, it lacks the direct tumor bone formation by malignant cells seen in osteosarcoma.

Question 86

A 55-year-old female presents with severe back pain. MRI shows multiple vertebral lesions. A bone scan is notably "cold" (negative) in these areas. Serum electrophoresis demonstrates an M-spike. What is the most likely diagnosis?

Explanation

Multiple myeloma characteristically presents with lytic bone lesions that do not provoke reactive bone formation, resulting in a "cold" or false-negative technetium bone scan. The presence of an M-spike on SPEP confirms the monoclonal gammopathy.

Question 87

When evaluating a patient with a suspected aneurysmal bone cyst (ABC), which of the following MRI findings is highly characteristic, though not entirely specific?

Explanation

Fluid-fluid levels on T2-weighted MRI represent blood products of varying ages settling within the cystic spaces of an ABC. While characteristic of ABCs, they can also be seen in telangiectatic osteosarcoma and giant cell tumors.

Question 88

A 25-year-old male has an expansile, lytic lesion in the posterior elements of L3 causing progressive lower extremity weakness. Biopsy confirms osteoblastoma. What is the most appropriate definitive surgical management?

Explanation

Surgical resection (intralesional curettage or en bloc depending on staging/morbidity) is the treatment of choice for spinal osteoblastomas causing neurologic deficit. Because of the size and destruction, spinal stabilization is often required.

Question 89

Which of the following primary malignancies most frequently metastasizes to the spine and predominantly presents with osteoblastic (sclerotic) lesions?

Explanation

Prostate cancer uniquely stimulates osteoblast activity, resulting in characteristically osteoblastic (sclerotic) metastatic lesions in the spine and pelvis. Lung, renal, and thyroid cancers typically produce osteolytic lesions.

Question 90

In the Enneking staging system for benign musculoskeletal tumors, an active benign tumor (Stage 2) is best described by which of the following?

Explanation

Enneking Stage 2 (active) benign tumors grow progressively and can thin or expand the cortex, but remain contained within natural barriers (capsule/periosteum). Stage 1 is latent, and Stage 3 is aggressive (breaking through barriers).

Question 91

A biopsy of a lytic bone lesion reveals blood-filled vascular spaces lacking an endothelial lining, surrounded by fibrous septae containing giant cells and woven bone. What is the diagnosis?

Explanation

The histologic hallmark of an aneurysmal bone cyst is the presence of cavernous, blood-filled spaces that lack true endothelial linings, separated by cellular fibrous septae containing giant cells.

Question 92

Which of the following targeted treatments is correctly paired with its mechanism of action for managing unresectable giant cell tumors of bone?

Explanation

Denosumab binds to RANKL, preventing it from binding to RANK on the surface of osteoclast precursors. This inhibits the formation and activity of the osteoclast-like giant cells responsible for the severe osteolysis in GCT.

Question 93

A 21-year-old female presents with a destructive, eccentric, lytic lesion in the distal femur epiphysis. Chest CT reveals asymptomatic small pulmonary nodules. Biopsy of the femoral lesion confirms Giant Cell Tumor (GCT). How should the pulmonary nodules be managed?

Explanation

Approximately 2-3% of giant cell tumors produce "benign pulmonary implants." These are histologically identical to the primary tumor and are not considered true malignant metastases; they are often managed with observation or surgical wedge resection.

Question 94

Which of the following statements is true regarding the risk of malignant transformation in patients with osteoblastoma?

Explanation

While osteoblastomas are benign, rare cases of malignant transformation into osteosarcoma have been documented, particularly in recurrent or aggressive variants. This contrasts with osteoid osteomas, which have virtually zero malignant potential.

Orthopedic Prometric MCQs - Chapter 3 Part 1

Orthopedic Prometric MCQs - Chapter 3 Part 34

Orthopedic Prometric MCQs - Chapter 3 Part 34

Chapter Index