ABOS Part I & AAOS OITE Orthopedic Surgery Review: Trauma & Oncology MCQs | Part 22297

Correct Answer: C

For isolated posterior wall acetabular fractures that are congruent and stable after closed reduction of a hip dislocation, non-operative management with protected weight-bearing and restricted range of motion is a recognized option. Instability is typically assessed with stress radiographs or dynamic fluoroscopy after reduction. If stable, close monitoring for secondary displacement or late instability is crucial. Surgical indications usually include persistent instability, incarcerated fragments, or significant displacement. Immediate ORIF is typically reserved for unstable fractures or those with incarcerated fragments. Skeletal traction is less commonly used for these stable fracture patterns. Hip arthroplasty is not indicated primarily for this injury pattern without pre-existing arthritis or severe head damage. A CT scan is usually performed initially to assess the fracture pattern and rule out incarcerated fragments, but repeating it in 24 hours without clinical change is not the primary management.

Correct Answer: D

The tension band wiring technique converts the tensile forces on the patella during knee flexion and active extension into compression forces at the fracture site. Active knee extension against resistance, particularly against gravity (e.g., straight leg raises), places significant tensile stress across the anterior aspect of the patella and can lead to immediate failure of the tension band construct. Early motion, especially passive flexion, is often encouraged to prevent stiffness, but active extension needs to be limited or avoided in the early post-operative period. Weight bearing is usually determined by pain tolerance and often progresses from touch-down to full, but it's less critical for the construct integrity than active extension. Restricting flexion too much can lead to stiffness, and unrestricted CPM may also put undue stress on the repair if active extension is performed.

Correct Answer: B

Displaced intertrochanteric hip fractures in elderly patients are typically managed surgically. A dynamic hip screw (DHS) is the gold standard for stable and reducible intertrochanteric fractures, providing controlled collapse at the fracture site which promotes impaction and healing. While intramedullary nailing (IMN) is often preferred for unstable intertrochanteric fractures (e.g., reverse obliquity, comminuted), a DHS remains a very viable option for many stable patterns, especially in the context of osteoporosis where load sharing is beneficial. Non-operative management is associated with high mortality and morbidity in this patient population. THA or hemiarthroplasty are generally reserved for displaced femoral neck fractures or failed previous fixation, not primarily for intertrochanteric fractures. External fixation is rarely used for these fractures due to high rates of complications and poor stability.

Correct Answer: C

Gustilo Type IIIB open tibia fractures involve extensive soft tissue damage and often require specialized soft tissue coverage. The 'golden period' for these injuries extends beyond primary closure, which is typically reserved for clean, smaller wounds without significant contamination or tissue loss. For Type IIIB injuries, early and definitive soft tissue coverage, usually within 72 hours of injury, is critical to reduce infection rates and promote fracture healing. This often involves local rotational flaps or free tissue transfer, depending on the size and location of the defect. Delayed primary closure is not appropriate for large defects with exposed bone. Split-thickness skin grafts require a well-vascularized bed and are usually insufficient to cover exposed bone or deep structures. Leaving the wound open for weeks increases infection risk and prolongs hospitalization.

Correct Answer: E

Salter-Harris Type V fractures, which involve a crush injury to the growth plate, have the highest risk of growth arrest due to direct damage to the germinal cells. While relatively rare, the prognosis for future growth is poor. Type IV fractures (fracture through metaphysis, physis, and epiphysis) also carry a high risk if not anatomically reduced, as a cartilaginous bridge can form across the physis. Type I (separation of physis) and Type II (physis and metaphysis) generally have good prognoses if reduced. Type III (physis and epiphysis) have a better prognosis than Type IV or V but still require anatomical reduction, especially if intra-articular.

Correct Answer: B

Subtrochanteric femur fractures are highly load-bearing and are subject to significant deforming forces (pull of gluteus medius/minimus on the proximal fragment, adductors on the distal fragment). Intramedullary nailing (IMN) is considered the gold standard for subtrochanteric femur fractures due to its load-sharing nature, biomechanical advantages, and typically less soft tissue stripping compared to plating. A DHS is primarily designed for intertrochanteric fractures and is less stable for subtrochanteric patterns, particularly comminuted ones. Plating can be an option but often requires more extensive exposure and is more prone to failure in comminuted or osteoporotic bone. Non-operative management is generally associated with poor outcomes. Hemiarthroplasty is not indicated for subtrochanteric fractures unless there's a concomitant femoral neck fracture or pre-existing hip pathology requiring replacement.

Correct Answer: C

A Maisonneuve fracture is a specific type of ankle injury characterized by a fracture of the proximal fibula, rupture of the syndesmosis (anterior inferior tibiofibular ligament, posterior inferior tibiofibular ligament, interosseous membrane), and often a deltoid ligament rupture or medial malleolus fracture. The key to diagnosis is recognizing the proximal fibula fracture in the context of an ankle injury, which often appears innocuous on standard ankle views. The critical aspect for management is assessing and restoring syndesmotic integrity, as disruption of the syndesmosis leads to ankle instability. Fixation of the medial malleolus is only done if it is fractured and significantly displaced. Calcaneal fractures are not directly associated. Vascular injury is rare unless there's a significant open injury or dislocation. Non-weight bearing cast immobilization alone is insufficient if the syndesmosis is unstable, which it typically is.

Correct Answer: E

While all listed options are potential signs of compartment syndrome, 'pain with passive stretching of the toes' (for the deep posterior and anterior compartments) and 'severe pain unresponsive to increasing doses of opioids' (pain out of proportion to injury) are considered the most sensitive and earliest signs of evolving compartment syndrome. Paresthesia can be an early sign but may also indicate nerve injury unrelated to compartment syndrome. Diminished pulses and pallor are late signs, often indicating irreversible muscle ischemia and nerve damage, and are less reliable early indicators because compartment pressure often exceeds venous pressure long before arterial flow is compromised.

Correct Answer: C

The Lisfranc ligament connects the medial cuneiform to the base of the second metatarsal. Diastasis (widening) between the base of the first and second metatarsals on weight-bearing AP radiographs is the most reliable radiographic sign of a Lisfranc injury, indicating disruption of the Lisfranc ligament complex and instability of the midfoot. A fleck sign (small avulsion fracture off the base of the second metatarsal or medial cuneiform) is also highly indicative. Fractures of the 5th metatarsal base or navicular/cuboid can occur but are not primary indicators of a Lisfranc injury. Talonavicular subluxation indicates a different midfoot or hindfoot pathology.

Correct Answer: B

Pilon fractures are high-energy injuries often associated with severe soft tissue damage. Significant swelling and blistering indicate compromised soft tissue envelope, making immediate ORIF risky due to high rates of wound complications and infection. The preferred initial management is to apply a spanning external fixator across the ankle to restore length, alignment, and indirectly reduce the fracture, which allows the soft tissues to recover. Definitive ORIF is then performed in a delayed fashion (often 7-14 days) once the swelling has subsided, and the skin wrinkles ('wrinkle sign'). A cast is insufficient to stabilize such a complex fracture. Percutaneous screws alone are usually inadequate. Amputation is a last resort.

Correct Answer: D

For displaced femoral neck fractures in elderly patients, surgical intervention is typically recommended within 24-48 hours. Patients on warfarin require rapid reversal of anticoagulation to minimize perioperative bleeding risks. The most effective and rapid reversal for significant bleeding risk is a combination of Vitamin K (for sustained effect) and Prothrombin Complex Concentrate (PCC) for immediate effect, allowing surgery once the INR is acceptable (typically <1.5). Factor Xa inhibitor reversal agents are for direct oral anticoagulants, not warfarin. Holding warfarin without rapid reversal delays surgery unnecessarily and increases DVT risk. Bridging therapy with heparin is not appropriate prior to emergency surgery for hip fracture due to bleeding risk.

Correct Answer: B

The clinical presentation of a tense leg, exquisite pain to passive stretch, and paresthesia, especially after a high-energy tibial plateau fracture, is highly suspicious for acute compartment syndrome, even with a palpable dorsalis pedis pulse. This is a surgical emergency. An emergent four-compartment fasciotomy is the most critical immediate step to prevent irreversible neuromuscular damage. A CT scan is for definitive surgical planning of the fracture but should not delay fasciotomy if compartment syndrome is suspected. Elevating the limb can actually worsen compartment syndrome by reducing perfusion pressure. ABI and doppler are for vascular injury assessment, which is different from compartment syndrome although both can coexist.

Correct Answer: D

For Gustilo-Anderson Type IIIA open fractures, there is significant soft tissue damage requiring thorough debridement. The wound should be left open for serial debridement to remove all devitalized tissue and prevent infection. Definitive soft tissue coverage, often requiring local or free flaps for Type IIIA and IIIB injuries, is typically performed in a delayed fashion, usually within 72 hours, once the wound is clean and healthy. Immediate primary closure in Type IIIA carries a high risk of infection. Delayed primary closure might be considered for less severe wounds but not for a Type IIIA. VAC is a dressing option, but immediate skin grafting is usually not feasible or appropriate for an initially contaminated wound of this severity.

Correct Answer: B

In a hemodynamically unstable patient with a pelvic fracture, control of hemorrhage is paramount. Application of a pelvic binder (or sheet) provides immediate temporary stabilization of the fracture and reduces pelvic volume, which can help tamponade venous bleeding. If instability persists despite initial binder application and fluid resuscitation, angioembolization is the next step to control arterial bleeding, which accounts for 10-20% of pelvic hemorrhage but is often more challenging to control. External fixation provides definitive mechanical stability but might not be fast enough to control active arterial hemorrhage. CT angiography is useful for identifying the source but treatment takes precedence. Chest tube for pneumothorax addresses a different injury. Vasopressors address the symptom, not the underlying cause of hypovolemic shock.

Correct Answer: C

Posterior hip dislocations are frequently associated with sciatic nerve injuries, particularly the common peroneal (fibular) division. This division supplies the muscles responsible for ankle dorsiflexion (e.g., tibialis anterior) and eversion (e.g., peroneus longus and brevis) and provides sensation to the dorsum of the foot. The tibial division of the sciatic nerve primarily supplies plantarflexors and foot intrinsics, and sensation to the sole. Femoral and obturator nerves are typically spared in posterior dislocations. Gluteal nerves supply gluteal muscles.

Correct Answer: D

Knee dislocations have a high rate of associated popliteal artery injury (up to 40%). Even with palpable pulses, intimal tears can lead to delayed thrombosis and limb loss. Therefore, a vascular assessment is critical. Ankle-brachial index (ABI) is a rapid and reliable screening tool. An ABI <0.9 is highly suspicious for vascular injury and warrants further imaging like CT angiography or conventional arteriography. While X-rays confirm dislocation and rule out fracture, and MRI details ligamentous injuries, these are not the most immediate concern for limb viability. Arteriography is usually reserved for a compromised ABI or strong clinical suspicion after ABI.

Correct Answer: C

Falls from a height that result in calcaneus fractures (known as 'lover's fractures' or 'don Juan' fractures) often transmit axial load up the kinetic chain. Therefore, it is crucial to screen for associated injuries, especially lumbar spine compression fractures (up to 10% of cases) and, less commonly, hip or tibial plateau fractures. While an Achilles rupture can occur with trauma, it's not a direct 'axial load' associated injury. Talus and patellar fractures are less common systemic associations with this mechanism.

Correct Answer: C

The presentation (widening between 1st/2nd metatarsal bases, fleck sign, inability to bear weight) is highly consistent with a Lisfranc (tarsometatarsal) joint injury. Displaced or unstable Lisfranc injuries require urgent surgical stabilization with ORIF (or primary arthrodesis in some cases) to restore anatomic alignment. Non-operative management or delayed treatment of unstable injuries leads to poor outcomes, including painful arthritis, arch collapse, and chronic pain. Immediate weight bearing or simple immobilization in a boot is insufficient for displaced/unstable injuries.

Correct Answer: C

Hawkins Type II talus neck fractures involve a displaced talus neck fracture with subtalar dislocation but an intact ankle joint. The blood supply to the talar body is tenuous and primarily enters through the talar neck. Displacement of the neck fracture and subtalar dislocation significantly disrupts this blood supply, placing the talar body at high risk (20-50%) for avascular necrosis (AVN). While nonunion and post-traumatic arthritis are also potential complications, AVN of the talar body is a hallmark and often devastating complication specifically associated with displaced talus neck fractures, increasing with higher Hawkins types. Post-traumatic arthritis is common regardless of AVN due to articular damage.

Correct Answer: B

For most displaced distal femoral fractures, particularly in osteopenic elderly patients, retrograde intramedullary nailing is often preferred. It offers a load-sharing construct, minimally invasive approach, and allows for earlier weight-bearing and mobilization compared to plate fixation. While plate fixation (especially locking plates) can be effective, nailing often has advantages in osteoporotic bone due to its load-sharing nature. External fixation is generally reserved for open fractures with significant soft tissue compromise or as a temporizing measure. Dual plating can be an option for highly comminuted fractures but is more invasive. Long-leg casting is typically not sufficient for displaced fractures in the elderly due to nonunion risk and difficulty with mobilization.

Correct Answer: A

Ewing's Sarcoma is characterized by specific chromosomal translocations involving the EWSR1 gene on chromosome 22, most commonly fused with the FLI1 gene on chromosome 11, resulting in the t(11;22)(q24;q12) EWS-FLI1 fusion protein. This fusion acts as an aberrant transcription factor crucial for oncogenesis and is the defining molecular hallmark of the Ewing Sarcoma Family of Tumors (ESFT).

Incorrect Options:

• B. t(X;18)(p11.2;q11.2) SYT-SSX1/2: This translocation is characteristic of Synovial Sarcoma.
• C. t(12;16)(q13;p11) FUS-DDIT3: This translocation is associated with Myxoid Liposarcoma.
• D. t(2;13)(q35;q14) PAX3-FKHR: This translocation is found in Alveolar Rhabdomyosarcoma.
• E. t(9;22)(q34;q11) BCR-ABL: This is the Philadelphia chromosome, characteristic of Chronic Myeloid Leukemia (CML).

Correct Answer: C

Ewing's Sarcoma can clinically (pain, fever, elevated inflammatory markers like ESR) and radiographically (lytic lesion, periosteal reaction) mimic osteomyelitis, making differentiation crucial. The most important initial step is to perform an MRI to better characterize the lesion's extent, soft tissue component, and relationship to neurovascular structures. This should be followed by a core needle biopsy to obtain tissue for definitive diagnosis, which includes histology, immunohistochemistry (e.g., CD99), and molecular genetics (e.g., FISH for EWSR1 rearrangement). Delaying diagnosis and treatment of Ewing's Sarcoma can have severe consequences.

Incorrect Options:

• A. Start empiric antibiotics for suspected osteomyelitis: While osteomyelitis is in the differential, starting empiric antibiotics without a definitive diagnosis risks delaying appropriate cancer treatment if it is Ewing's Sarcoma.
• B. Perform an open biopsy immediately: A core needle biopsy is generally preferred as the initial biopsy method for suspected bone tumors, as it is less invasive, allows for appropriate tissue acquisition, and minimizes contamination of tissue planes, which is important for subsequent limb salvage surgery. Open biopsy is reserved for cases where core biopsy is non-diagnostic.
• D. Monitor symptoms and repeat X-rays in 4-6 weeks: This approach is inappropriate for a potentially aggressive malignancy like Ewing's Sarcoma, which requires urgent diagnosis and treatment.
• E. Order a white blood cell count and C-reactive protein only: While these are useful inflammatory markers, they are non-specific and cannot differentiate between infection and malignancy. Definitive tissue diagnosis is required.

Correct Answer: D

Magnetic Resonance Imaging (MRI) of the entire involved bone, extending from joint to joint and including the adjacent joints, is the gold standard for local staging of bone and soft tissue tumors like Ewing's Sarcoma. It provides superior soft tissue resolution, allowing accurate assessment of intramedullary and extraosseous tumor extent, involvement of neurovascular bundles, joint invasion, and crucially, the detection of 'skip lesions' (discontinuous tumor foci within the same bone). This detailed information is paramount for surgical planning and determining resectability, especially in limb salvage procedures.

Incorrect Options:

• A. Plain X-ray: X-rays are initial screening tools but lack the soft tissue and marrow detail needed to assess the full extent of the tumor or detect skip lesions.
• B. CT scan of the primary site: CT provides excellent bony detail but is inferior to MRI for evaluating intramedullary extent, soft tissue involvement, and skip lesions.
• C. Bone scintigraphy (bone scan): Bone scans (Technetium-99m) are highly sensitive for detecting increased metabolic activity in bone, making them useful for screening for skeletal metastases, but they lack the anatomical resolution to precisely define the local tumor extent or skip lesions for surgical planning.
• E. Ultrasound: Ultrasound is useful for evaluating superficial soft tissue masses and guiding biopsies but has limited utility for assessing intraosseous tumor extent or skip lesions in long bones.

Correct Answer: C

Ewing's Sarcoma is classically described as a 'small round blue cell tumor.' Histologically, it consists of sheets of relatively uniform, small, round cells with scant, clear cytoplasm (due to high glycogen content, which can be demonstrated by PAS staining) and ill-defined cell borders. The nuclei are typically round to oval with fine chromatin and inconspicuous nucleoli. This characteristic appearance, along with positive immunohistochemical staining for CD99 and specific genetic translocations, confirms the diagnosis.

Incorrect Options:

• A. Abundant osteoid production with spindle cells: This is the hallmark histological feature of osteosarcoma.
• B. Large pleomorphic cells with prominent nucleoli arranged in a herringbone pattern: This description is more typical of a high-grade spindle cell sarcoma, such as an undifferentiated pleomorphic sarcoma or fibrosarcoma.
• D. Chondroid matrix with entrapped lacunae: This describes a cartilaginous tumor, such as chondrosarcoma or enchondroma.
• E. Multinucleated giant cells and mononuclear stromal cells: This is the characteristic histological appearance of a Giant Cell Tumor of Bone.

Correct Answer: D

The presence of metastatic disease at diagnosis is the single most important negative prognostic factor in Ewing's Sarcoma. Patients with metastatic disease have significantly worse survival rates compared to those with localized disease, even with aggressive multimodal therapy. Common sites of metastasis include the lungs, bone, and bone marrow.

Incorrect Options:

• A. Age greater than 10 years: While very young age (e.g., <5 years) can sometimes be associated with a slightly better prognosis, age greater than 10 years is not considered a primary negative prognostic factor; the peak incidence is in adolescence.
• B. Tumor size less than 8 cm: Larger tumor size (typically >8 cm or >200 ml) is generally associated with a poorer prognosis, so a tumor size less than 8 cm would be a relatively more favorable factor, not a negative one.
• C. Primary tumor site in the distal extremity: Distal extremity tumors generally have a more favorable prognosis compared to central axial sites (e.g., pelvis, spine) due to easier resectability and lower rates of local recurrence.
• E. Elevated LDH: Elevated serum lactate dehydrogenase (LDH) is a non-specific marker that often correlates with higher tumor burden and more aggressive disease, and it is considered a poor prognostic indicator. However, it is secondary to the presence of overt metastatic disease in terms of prognostic impact.

Correct Answer: C

The primary goals of neoadjuvant (pre-operative) chemotherapy in Ewing's Sarcoma are multifaceted:

• Reduce tumor size (debulking): This can make a previously unresectable tumor resectable, facilitate limb-sparing surgery, and improve the chances of achieving wide, tumor-free surgical margins.
• Treat micrometastatic disease: Ewing's Sarcoma has a high propensity for micrometastasis, and systemic chemotherapy addresses these distant foci early, even if not detectable on initial staging.
• Assess tumor response: The histological response to neoadjuvant chemotherapy (percentage of tumor necrosis) is a significant prognostic indicator. A good response (typically >90% necrosis) correlates with better outcomes.

This 'chemoprimary' approach is standard for Ewing's Sarcoma.

Incorrect Options:

• A. To avoid the need for surgery completely: While chemotherapy can achieve significant tumor regression, it rarely eliminates the need for local control (surgery or radiation) for the primary tumor.
• B. To improve patient nutrition before surgery: While supportive care is important, improving nutrition is not the primary oncologic goal of neoadjuvant chemotherapy.
• D. To definitively cure the local tumor without any further treatment: Chemotherapy alone is generally insufficient for definitive local control of the primary tumor; it must be followed by surgery and/or radiation.
• E. To induce a pathological fracture for easier tumor removal: Inducing a pathological fracture is not a therapeutic goal; it is a complication that can occur due to tumor weakening of the bone and can complicate surgical planning.

Correct Answer: C

Radiation therapy is a critical component of multimodal treatment for Ewing's Sarcoma. Its primary indications are to improve local control in cases where surgical margins are positive (R1 or R2 resection) or close (as anticipated in this pelvic case), or when the tumor is unresectable. In the pelvis, achieving wide, tumor-free margins can be challenging without causing significant morbidity, making adjuvant radiation a common and important strategy to reduce the risk of local recurrence.

Incorrect Options:

• A. As a substitute for systemic chemotherapy: Radiation therapy is a local treatment modality and cannot substitute for systemic chemotherapy, which is essential for treating micrometastatic disease.
• B. To prevent limb length discrepancy in children: Radiation therapy, especially in growing children, can damage growth plates and actually cause limb length discrepancy and skeletal deformities, rather than preventing them.
• D. To increase bone density in the treated area: Radiation therapy does not increase bone density; it can lead to osteopenia or osteonecrosis in the long term.
• E. To induce a pathologic fracture for easier resection: Inducing a pathological fracture is not a therapeutic goal of radiation; it is a potential complication of tumor progression or bone weakening.

Correct Answer: B

In growing children undergoing limb salvage surgery, particularly around long bones like the distal femur where a significant portion of the growth plate is removed or damaged (e.g., by radiation), the most significant long-term concern is the development of a substantial limb length discrepancy. This occurs because the treated limb's growth is arrested or severely impaired, while the contralateral limb continues to grow normally. This requires careful planning, often using expandable prostheses or subsequent lengthening procedures, to manage the discrepancy as the child grows.

Incorrect Options:

• A. Increased risk of deep vein thrombosis: DVT is an acute or subacute surgical complication, not a primary long-term growth-related concern.
• C. Accelerated growth of the contralateral limb: While the contralateral limb continues to grow, it does not accelerate its growth; rather, the treated limb's growth is stunted, creating the discrepancy.
• D. Premature fusion of all growth plates: Radiation or surgery typically affects only the treated growth plate(s), not all growth plates in the body.
• E. Development of Charcot arthropathy: Charcot arthropathy is a neuropathic joint condition, typically seen in patients with severe peripheral neuropathy (e.g., from diabetes or certain chemotherapy agents), and is not a direct consequence of limb salvage surgery for Ewing's Sarcoma.

Correct Answer: A

The classic radiographic appearance of Ewing's Sarcoma is a lamellated or 'onion-skin' periosteal reaction, which results from layers of reactive bone formation due to the tumor's rapid, infiltrative growth. In contrast, osteosarcoma frequently demonstrates a 'sunburst' periosteal reaction (spicules of bone perpendicular to the cortex) or a Codman's triangle (a triangular elevation of the periosteum at the tumor margin). These distinct periosteal reactions are key differentiating features on plain radiographs.

Incorrect Options:

• B. Ewing's is usually a purely sclerotic lesion, while osteosarcoma is purely lytic: Ewing's Sarcoma is typically a lytic lesion, often with ill-defined margins. Osteosarcoma can be lytic, sclerotic, or mixed (osteoblastic, osteolytic, or chondroblastic).
• C. Ewing's primarily affects the epiphysis, whereas osteosarcoma affects the diaphysis: Ewing's Sarcoma typically affects the diaphysis or metadiaphysis of long bones and flat bones. Osteosarcoma most commonly affects the metaphysis of long bones. Epiphyseal lesions are more characteristic of chondroblastoma.
• D. Ewing's lesions typically have sharp, well-defined margins, unlike osteosarcoma: Both Ewing's Sarcoma and osteosarcoma are aggressive malignancies and typically present with ill-defined, permeative margins, indicating their invasive nature.
• E. Osteosarcoma rarely has a soft tissue mass, while Ewing's always does: Both Ewing's Sarcoma and osteosarcoma frequently present with a significant soft tissue mass, often larger than the intraosseous component, due to cortical breach and extraosseous extension.

Correct Answer: C

Ifosfamide is an alkylating agent commonly used in the treatment of Ewing's Sarcoma. Its most characteristic and serious toxicity is hemorrhagic cystitis, which is caused by the urotoxic metabolite acrolein. Symptoms include dysuria, frequency, and hematuria. This complication is typically prevented by co-administering Mesna (2-mercaptoethane sulfonate sodium), which inactivates acrolein in the bladder, and ensuring adequate hydration.

Incorrect Options:

• A. Cardiotoxicity (dose-dependent): Cardiotoxicity, particularly dilated cardiomyopathy, is a well-known dose-dependent complication of anthracyclines like Doxorubicin, another agent used in Ewing's regimens, but not primarily Ifosfamide.
• B. Peripheral neuropathy: Peripheral neuropathy is a common side effect of vinca alkaloids, such as Vincristine, which is also part of Ewing's Sarcoma chemotherapy regimens.
• D. Ototoxicity: Ototoxicity (hearing loss, tinnitus) is a significant side effect associated with platinum-based agents like Cisplatin, which is not a standard first-line agent for Ewing's Sarcoma.
• E. Pulmonary fibrosis: Pulmonary fibrosis is a rare but severe complication associated with certain chemotherapy agents like Bleomycin or Busulfan, which are not typically used in standard Ewing's Sarcoma regimens.

Correct Answer: D

Academic Rationale:

For any suspicious soft tissue mass, especially one that is deep-seated, firm, enlarging, and shows concerning features on MRI (thick enhancing septa, non-fatty nodules), a pre-operative tissue diagnosis is crucial to guide definitive treatment. Ultrasound-guided core needle biopsy is the most appropriate next step. It provides sufficient tissue for histological diagnosis and ancillary studies (e.g., molecular genetics) while minimizing contamination of tissue planes, which is vital for subsequent oncologic resection. Fine needle aspiration (FNA) often yields insufficient tissue for definitive diagnosis and grading of sarcomas. Immediate wide local excision without a biopsy is inappropriate as it risks inadequate margins if the tumor is malignant, or overtreatment if it is benign. Observation is not warranted for a suspicious, enlarging mass. Intralesional injections are not a diagnostic or therapeutic option for suspected sarcomas.

Correct Answer: D

Academic Rationale:

Dedifferentiated liposarcoma (DDLPS) is characterized by the coexistence of a well-differentiated liposarcoma (WDLPS) component (which appears as a fatty mass on MRI) with a distinct, non-lipogenic, high-grade sarcomatous component (which appears as a solid, enhancing nodule). This bimodal appearance on imaging, with both fatty and solid enhancing components, is highly specific for DDLPS. Myxoid liposarcoma typically presents with a prominent myxoid matrix and a plexiform vascular pattern, while pleomorphic liposarcoma is a high-grade, non-lipogenic sarcoma with pleomorphic cells. Well-differentiated liposarcoma would primarily show fatty signal with potentially thin septa but no distinct solid non-lipomatous nodule. Lipoma with myxoid degeneration is a benign entity and would not exhibit a high-grade solid enhancing component.

Correct Answer: C

Academic Rationale:

The description of a prominent myxoid matrix, a distinctive delicate plexiform capillary network (often described as curvilinear vessels), and a proliferation of small, primitive round and spindle cells, along with the presence of lipoblasts, are the classic histological hallmarks of myxoid liposarcoma. Well-differentiated liposarcoma consists primarily of mature adipocytes with atypical stromal cells. Dedifferentiated liposarcoma has a high-grade non-lipogenic component. Pleomorphic liposarcoma is characterized by marked cellular pleomorphism and bizarre giant cells. Spindle cell lipoma is a benign entity with mature adipocytes and uniform spindle cells, lacking the myxoid stroma and plexiform vascularity of myxoid liposarcoma.

Correct Answer: C

Academic Rationale:

The characteristic genetic alteration found in myxoid liposarcoma is the FUS-DDIT3 fusion gene, resulting from a reciprocal translocation between chromosomes 12 and 16, denoted as t(12;16)(q13;p11). This fusion gene is a key diagnostic marker. The t(X;18) translocation is characteristic of Synovial Sarcoma. MDM2 and CDK4 gene amplification is the hallmark of well-differentiated liposarcoma/atypical lipomatous tumor. EWSR1-FLI1 translocation is associated with Ewing sarcoma. BRAF V600E mutation is seen in melanoma and other cancers, but not typically liposarcoma.

Correct Answer: D

Academic Rationale:

For soft tissue sarcomas, including liposarcomas, the margin status of excision is consistently the most critical factor influencing local recurrence rates. Achieving negative surgical margins (R0 resection) is paramount for local disease control. While tumor size, histological subtype (especially higher grade), and patient age can influence overall prognosis and risk of recurrence, the adequacy of surgical excision, as reflected by the margin status, is the primary determinant of local control. Close or positive margins significantly increase the risk of local recurrence, often necessitating adjuvant radiotherapy.

Correct Answer: C

Academic Rationale:

Well-differentiated liposarcomas (ALT) located in the extremities or trunk wall (like the anterior abdominal wall in this case), when adequately excised with wide negative margins, have an excellent prognosis. These tumors are locally aggressive but do not metastasize unless they dedifferentiate, which is a rare event in extremity/trunk wall ALTs compared to retroperitoneal lesions. The primary risk is local recurrence if margins are inadequate, but with wide negative margins, this risk is significantly minimized. Therefore, the patient has a very good prognosis with a low risk of local recurrence and no metastatic potential. Adjuvant chemotherapy is not indicated, and while radiotherapy can be considered for close margins, it's not universally required for wide negative margins in this specific location and grade.

Correct Answer: D

Academic Rationale:

Angiolipomas are benign lipomatous tumors characterized by a prominent vascular component (mature capillary-sized vessels) within the adipose tissue. A distinguishing clinical feature of angiolipomas, unlike conventional lipomas, is that they frequently present as painful or tender nodules. Conventional lipomas are typically painless. Hibernomas arise from brown fat. Spindle cell lipomas contain mature adipocytes and uniform spindle cells. Pleomorphic lipomas contain characteristic floret-type giant cells. The combination of a fatty lesion, prominent vascularity, and tenderness strongly points to angiolipoma.

Correct Answer: D

Academic Rationale:

High-grade soft tissue sarcomas, including pleomorphic liposarcoma, have a significant risk of distant metastasis. The most common site of distant metastasis for these tumors is the lungs. Therefore, a Computed Tomography (CT) scan of the chest is crucial for detecting pulmonary metastases. Depending on the primary site and specific metastatic patterns, a CT of the abdomen and pelvis may also be included to screen for other common metastatic sites. MRI of the surgical bed is essential for local staging and detecting local recurrence, but not for distant metastasis screening. Plain radiography and ultrasound of lymph nodes are generally not sufficient for comprehensive distant staging of high-grade sarcomas. Bone scans are reserved for suspected bone involvement.

Correct Answer: C

Academic Rationale:

Myxoid liposarcoma is uniquely recognized among soft tissue sarcomas for its relative sensitivity to both chemotherapy and, more notably, radiation therapy. This characteristic makes radiotherapy a crucial component of its management, often utilized in neoadjuvant (pre-operative) or adjuvant (post-operative) settings to improve local control and facilitate limb salvage. While radiation therapy is used for other high-grade sarcomas, myxoid liposarcoma shows a particularly favorable response. Well-differentiated liposarcoma is less radiosensitive, and while dedifferentiated and pleomorphic liposarcomas are high-grade, myxoid liposarcoma stands out for its specific radiosensitivity.

Correct Answer: C

Academic Rationale:

Gardner Syndrome is an autosomal dominant disorder, a variant of Familial Adenomatous Polyposis (FAP), characterized by intestinal polyps with a high risk of malignant transformation to colorectal cancer. Its extracolonic manifestations are key to its diagnosis and include multiple osteomas (especially of the mandible and skull), epidermoid cysts, desmoid tumors (aggressive fibromatosis), and various soft tissue tumors, including lipomas and fibromas. Neurofibromatosis Type 1 is associated with neurofibromas and café-au-lait spots. Li-Fraumeni Syndrome is a cancer predisposition syndrome. Multiple Endocrine Neoplasia Type 2A involves endocrine tumors. Von Hippel-Lindau Disease is associated with hemangioblastomas and renal cell carcinoma.

In a hemodynamically unstable patient with a mechanically unstable pelvic ring injury and a negative FAST exam, the source of bleeding is presumed to be the pelvis. The standard of care after mechanical stabilization (pelvic binder) is preperitoneal pelvic packing and/or angiography to control venous and arterial hemorrhage.

The clinical presentation and histology are classic for Ewing sarcoma. The t(11;22) translocation, resulting in the EWS-FLI1 fusion protein, is present in over 85% of Ewing sarcoma cases.

A posteromedial approach is required to properly reduce and apply a buttress plate to the displaced posteromedial fragment in a Schatzker IV (medial plateau) fracture. An anterolateral approach cannot adequately address the posteromedial shear component.

The most significant prognostic factor in conventional high-grade osteosarcoma is the histologic response to neoadjuvant chemotherapy. Greater than 90% tumor necrosis is considered a good response and correlates with improved long-term survival.

A Hawkins III fracture involves dislocation of both the subtalar and tibiotalar joints, disrupting all three major blood supplies to the talar body. These include the artery of the tarsal canal, the artery of the sinus tarsi, and the superior neck branches.

Conventional chondrosarcoma is notably resistant to both chemotherapy and radiation therapy. The mainstay of treatment for intermediate to high-grade lesions is wide surgical resection with negative margins.

Pauwels Type III fractures are highly vertical and subjected to significant shear forces. A fixed-angle device, such as a sliding hip screw combined with a derotation screw, provides superior biomechanical stability compared to parallel cannulated screws.

Mirels' scoring system evaluates Site, Nature, Size, and Pain on a 1 to 3 scale. A peritrochanteric location is considered the highest risk for fracture in the Site category and is awarded 3 points.

Acute compartment syndrome is generally diagnosed when the delta pressure (diastolic blood pressure minus intracompartmental pressure) is less than 30 mmHg. Relying on an absolute pressure threshold is less accurate due to variations in patient hemodynamics.

The diagnosis is Giant Cell Tumor of bone, driven by the overexpression of RANKL by the neoplastic mononuclear cells. Denosumab is a monoclonal antibody against RANKL and is highly effective for unresectable or recurrent disease.

Multiple studies and guidelines have demonstrated that the time from injury to the initial administration of intravenous antibiotics is the most critical factor in reducing infection rates in open fractures. Delaying antibiotics significantly increases infection risk.

The clinical picture describes Multiple Myeloma, which is characterized by the CRAB criteria (Calcium elevation, Renal failure, Anemia, Bone lesions). The underlying pathology is a malignant proliferation of monoclonal plasma cells in the bone marrow.

A primary radial nerve palsy associated with a closed humeral shaft fracture does not routinely require immediate surgical exploration. The standard of care is functional bracing and observation, as over 70% of these palsies will spontaneously recover.

The presentation is classic for an osteoid osteoma (nidus <1.5 cm, nocturnal pain relieved by NSAIDs). If medical management fails or the patient prefers definitive treatment, CT-guided radiofrequency ablation is the gold standard minimally invasive treatment.

The extensile lateral approach to the calcaneus involves creating a full-thickness flap. The sural nerve courses posterior to the lateral malleolus and along the lateral aspect of the foot, placing it at high risk during the vertical and horizontal limbs of the incision.

The dependent cortical fragment is the fallen leaf sign, pathognomonic for a Unicameral Bone Cyst (UBC). Aspiration of a UBC typically yields clear or slightly serosanguinous fluid, distinguishing it from an aneurysmal bone cyst (ABC) which yields unclotting blood.

A volar Barton's fracture involves an unstable volar shear fragment that allows the carpus to subluxate volarly. A volar plate applied in a buttress mode best neutralizes these shear forces and maintains joint congruity.

Synovial sarcoma is characterized by the t(X;18)(p11;q11) chromosomal translocation. This creates the pathognomonic SYT-SSX fusion gene. Despite its name, it rarely arises directly from within the intra-articular synovium.

Elevated serum lactate (>2.5 to 4.0 mmol/L) or a base deficit greater than 6 mEq/L indicates ongoing hypoperfusion and a state of shock. These borderline or unstable patients should undergo Damage Control Orthopedics to minimize the physiologic hit of prolonged surgery.

The clinical presentation and midline sacral location are typical for a Chordoma. Histologically, chordomas are characterized by the presence of physaliferous cells, which have abundant bubbly, vacuolated cytoplasm containing mucin.

High-grade osteosarcoma is treated with neoadjuvant chemotherapy, followed by wide surgical resection and adjuvant chemotherapy. This approach allows for the assessment of tumor necrosis, which is a critical prognostic indicator.

A delta pressure (diastolic blood pressure minus compartment pressure) of less than 30 mmHg is an absolute indication for immediate fasciotomy. This patient's delta pressure is 25 mmHg, diagnosing acute compartment syndrome.

Intermediate to high-grade chondrosarcomas are relatively chemoresistant and radioresistant. The treatment of choice is wide surgical resection to minimize local recurrence.

A sliding hip screw (dynamic hip screw) combined with a derotational screw provides superior biomechanical stability against vertical shear forces. This makes it superior to parallel cancellous screws for highly vertical Pauwels type III fractures.

Denosumab is a monoclonal antibody against RANKL used for Giant Cell Tumors of bone. It inhibits osteoclast-like giant cells, leading to tumor consolidation and facilitating subsequent surgical curettage.

In an APC II pelvic ring injury, the anterior sacroiliac, sacrotuberous, and sacrospinous ligaments are disrupted, causing rotational instability. The posterior sacroiliac ligaments remain intact, preserving vertical stability.

Ewing sarcoma is classically characterized by the t(11;22)(q24;q12) translocation. This translocation results in the EWS-FLI1 fusion protein, a key molecular diagnostic marker.

Extensor pollicis longus (EPL) tendon rupture is a known complication of distal radius fractures and their fixation. It is often caused by prominent dorsal screw penetration or regional ischemia, presenting as a sudden loss of active thumb IP extension.

Metastatic prostate cancer typically produces osteoblastic bone lesions, which lead to an elevation in alkaline phosphatase. Prostate-specific antigen (PSA) will also be elevated given his primary diagnosis.

Soft tissue coverage of Type IIIB open tibia fractures should optimally be performed within 3 to 7 days. Delaying coverage beyond 7 days significantly increases the risk of deep infection and flap failure.

The clinical and radiographic presentation is classic for an osteoid osteoma. Radiofrequency ablation is the gold standard minimally invasive definitive treatment, offering high success rates with low morbidity.

A Hawkins Type III talar neck fracture involves displacement of the talar body with dislocation of the subtalar, tibiotalar, and talonavicular joints. This injury carries a very high risk of avascular necrosis approaching 100%.

The presentation is classic for multiple myeloma (hypercalcemia, renal failure, anemia, and bone lesions). Serum and urine protein electrophoresis identifying a monoclonal spike (M-protein) is essential for diagnosis.

The patient is exhibiting classic signs of fat embolism syndrome. The mainstay of treatment is supportive care, primarily consisting of aggressive respiratory support and maintaining adequate oxygenation.

A wide margin is defined by an intact cuff of normal tissue surrounding the entire tumor. When a robust anatomical barrier like intact deep fascia is present, even a physically narrow margin is considered oncologically wide.

The scaphoid is supplied primarily by the dorsal carpal branch of the radial artery, which enters the distal pole and flows retrogradely. This retrograde supply explains the high rate of nonunion and AVN in proximal pole fractures.

The diagnosis is desmoid fibromatosis, frequently associated with pregnancy or trauma and characterized by beta-catenin mutations. Active surveillance is the current first-line management, as many tumors spontaneously arrest or regress.

The anterior interosseous nerve (AIN) is the most commonly injured nerve in extension-type pediatric supracondylar humerus fractures. Injury results in weakness of the flexor pollicis longus, presenting as an inability to form the "OK" sign.

The clinical picture and biphasic histology are diagnostic of synovial sarcoma. This tumor is classically associated with the t(X;18)(p11;q11) chromosomal translocation, resulting in the SYT-SSX fusion gene.

The extensile lateral approach to the calcaneus involves creating a full-thickness fasciocutaneous flap dependent on the lateral calcaneal artery. The most feared complication is wound edge necrosis leading to deep infection.

The presence of distant metastasis at the time of diagnosis is the most critical prognostic factor for overall survival in osteosarcoma. Without metastasis, 5-year survival is 60-70%, dropping to less than 20% if metastasis is initially present.

An APC II injury involves disruption of the pubic symphysis, anterior SI, sacrotuberous, and sacrospinous ligaments. An APC III injury implies complete hemipelvis instability, necessitating the additional disruption of the strong posterior SI ligaments.

Denosumab is highly effective for Giant Cell Tumor of bone and acts as a monoclonal antibody that inhibits RANKL. This prevents osteoclast-like giant cell formation, thereby reducing tumor-associated bone resorption.

The artery of the tarsal canal, a branch of the posterior tibial artery, provides the dominant blood supply to the talar body. It is typically completely disrupted in displaced talar neck fractures, leading to avascular necrosis.

Ewing sarcoma is classically associated with the t(11;22) translocation, which fuses the EWS gene on chromosome 22 with the FLI1 gene on chromosome 11. This specific translocation is found in approximately 85% of Ewing sarcoma cases.

Posterior-to-anterior (PA) lag screw placement is biomechanically superior to anterior-to-posterior placement for Hoffa fractures. PA screws better resist primary deforming forces and secure the dense posterior cortical bone against the anterior fragment.

Synovial sarcoma often presents in young adults as a slow-growing mass in the extremities (especially the foot and ankle) with punctate calcifications on radiographs. The biphasic histology and t(X;18) translocation are diagnostic hallmarks.

Compartment syndrome is most accurately diagnosed using the delta pressure, calculated as diastolic blood pressure minus compartment pressure. A delta pressure of less than 30 mmHg is the accepted and most reliable threshold indicating the need for emergent fasciotomy.

Metastatic renal cell carcinoma and thyroid carcinoma lesions are notoriously hypervascular and carry a severe risk of massive intraoperative hemorrhage. Preoperative selective arterial embolization 24-48 hours before surgery is critically indicated.

The standard posteromedial approach to the tibial plateau utilizes the interval between the medial head of the gastrocnemius (retracted laterally) and the pes anserinus (retracted medially). This provides direct, safe access to the posteromedial articular fragment.

Mirels' criteria scores location, pain, lesion size, and radiographic appearance on a scale from 1 to 3. Severe pain, a strictly osteolytic nature, lower extremity/peritrochanteric location, and a size > 2/3 of cortical diameter each score the maximum of 3 points.

The extensile lateral flap for calcaneus fractures relies entirely on the lateral calcaneal artery, a terminal branch of the peroneal artery. Creating a subperiosteal, "no-touch" full-thickness flap is critical to preserve this fragile blood supply.

The clinical presentation is classic for a primary conventional high-grade chondrosarcoma, indicated by the rings/arcs calcification and deep endosteal scalloping. Because conventional chondrosarcoma is resistant to both chemotherapy and radiation, wide surgical resection is the standard of care.