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1. General Principles & Basic Science MCQs

Practice Set 628 of 789

This practice set contains high-yield board review questions covering key concepts in 1. General Principles & Basic Science. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 12541

Topic: 1. General Principles & Basic Science

A 20-year-old male sustains a traumatic guillotine amputation of his left leg at the mid-tibial level in an industrial accident. He is hemodynamically stable. What is the immediate priority for limb care in the pre-hospital or emergency department setting for potential replantation?

. Place the amputated part directly on ice.
. Wrap the amputated part in a saline-moistened gauze, seal in a plastic bag, and place on ice.
. Submerge the amputated part in sterile water.
. Freeze the amputated part to preserve tissues.
. Perform immediate wound closure of the stump.

Correct Answer & Explanation

. Wrap the amputated part in a saline-moistened gauze, seal in a plastic bag, and place on ice.

Explanation

The proper handling of an amputated limb for potential replantation is critical to maximize viability. The amputated part should be gently cleaned of gross contamination, wrapped in saline-moistened sterile gauze, placed in a sealed plastic bag, and then placed in a second bag or container with ice water (not direct ice, which can cause frostbite). This 'cool ischemia' slows metabolic processes, extending the time window for successful replantation. Placing directly on ice can cause frostbite. Submerging in water can cause tissue maceration. Freezing destroys cells. Immediate wound closure of the stump is not the priority over preserving the amputated part and can compromise future replantation efforts.

Question 12542

Topic: Infection, Pharmacology & VTE

A 60-year-old female with diabetes and peripheral neuropathy sustains a comminuted fracture of the cuboid bone in her midfoot. The fracture is displaced, but she has palpable pulses and intact motor function. What is the most critical concern regarding wound healing and infection in her management?

. Avascular necrosis of the cuboid.
. Compartment syndrome.
. Deep vein thrombosis (DVT).
. Diabetic foot ulcers and osteomyelitis.
. Complex regional pain syndrome (CRPS).

Correct Answer & Explanation

. Diabetic foot ulcers and osteomyelitis.

Explanation

Patients with diabetes, especially those with peripheral neuropathy, are at significantly increased risk for developing diabetic foot ulcers, delayed wound healing, and subsequent osteomyelitis following any foot trauma or surgery. Impaired sensation, poor circulation, and compromised immune function create a high-risk environment. Therefore, careful wound management, diligent glycemic control, and vigilance for signs of infection are paramount. While AVN, compartment syndrome, DVT, and CRPS are potential complications, the combination of diabetes and foot trauma makes ulcers and osteomyelitis a very pressing and common concern. This requires a multidisciplinary approach.

Question 12543

Topic: 1. General Principles & Basic Science

A 25-year-old male sustains a direct blow to the lateral aspect of his knee, resulting in a knee dislocation. After emergent closed reduction, he has palpable pulses, but an ABI of 0.8 on the affected side. What is the most appropriate next step in management?

. Discharge with knee immobilizer and close follow-up.
. Immediate surgical repair of the knee ligaments.
. Admission for observation and serial vascular exams.
. Emergent CT angiogram (CTA) of the lower extremity.
. Application of a long leg cast.

Correct Answer & Explanation

. Emergent CT angiogram (CTA) of the lower extremity.

Explanation

Even after successful reduction of a knee dislocation, a multi-ligamentous injury puts the popliteal artery at high risk. An ABI of 0.8 is a 'soft sign' of vascular injury (ABI < 0.9 is abnormal) and mandates further investigation. While observation and serial exams might be considered in some scenarios, an abnormal ABI following knee dislocation requires definitive vascular imaging to rule out an intimal tear or spasm that could lead to delayed thrombosis and limb loss. An emergent CT angiogram (CTA) is the gold standard for this assessment. Discharging the patient or proceeding directly to ligament repair without clearing the vascular status would be negligent. A long leg cast would prevent regular vascular assessment.

Question 12544

Topic: Infection, Pharmacology & VTE

A 68-year-old male undergoes open reduction and internal fixation of a distal femur fracture. Postoperatively, he develops sudden onset dyspnea, pleuritic chest pain, and hypoxemia. What is the most important initial diagnostic test to confirm the suspected diagnosis?

. Electrocardiogram (ECG).
. Chest X-ray.
. D-dimer assay.
. Computed tomography pulmonary angiogram (CTPA).
. Lower extremity venous duplex ultrasound.

Correct Answer & Explanation

. Computed tomography pulmonary angiogram (CTPA).

Explanation

The patient's symptoms (sudden dyspnea, pleuritic chest pain, hypoxemia) following a major lower limb orthopedic surgery are highly suggestive of a pulmonary embolism (PE). The most important initial diagnostic test to confirm a PE is a computed tomography pulmonary angiogram (CTPA). This imaging modality directly visualizes emboli in the pulmonary arteries. While D-dimer assay is a good screening test, a positive result requires further imaging for confirmation, especially in high-risk patients. ECG and chest X-ray might show non-specific changes but are not diagnostic for PE. Lower extremity venous duplex ultrasound can identify the source DVT but does not confirm the PE itself.

Question 12545

Topic: Infection, Pharmacology & VTE

A 50-year-old obese male suffers a low-energy fall, sustaining an unstable intertrochanteric hip fracture. He has multiple medical comorbidities. What is the primary benefit of early surgical fixation (within 24-48 hours) for this patient?

. Reduced risk of avascular necrosis of the femoral head.
. Reduced incidence of nonunion.
. Decreased time to ambulation and reduced medical complications.
. Elimination of the need for DVT prophylaxis.
. Improved cosmetic outcome.

Correct Answer & Explanation

. Decreased time to ambulation and reduced medical complications.

Explanation

For elderly patients with hip fractures, early surgical fixation (ideally within 24-48 hours, 'hip fracture in 24-48') is crucial. The primary benefit is a significantly decreased time to ambulation and reduced incidence of medical complications such as pneumonia, pressure ulcers, DVT/PE, and overall mortality. Prolonged bed rest in this population leads to increased morbidity and mortality. While surgical fixation does improve union rates, the immediate benefit for an unstable intertrochanteric fracture is the ability to mobilize the patient. AVN is not a primary concern with intertrochanteric fractures, unlike femoral neck fractures. DVT prophylaxis is still needed. Cosmetic outcome is not a primary driver for urgency.

Question 12546

Topic: Biology, Genetics & Bone Healing

Which type of cells found in the fibrous septa of an Aneurysmal Bone Cyst are responsible for the local bone resorption and contribute to the lesion's expansile nature?

. Osteocytes
. Chondrocytes
. Osteoblasts
. Osteoclast-like giant cells
. Adipocytes

Correct Answer & Explanation

. Osteoclast-like giant cells

Explanation

The fibrous septa of an Aneurysmal Bone Cyst contain numerous multinucleated osteoclast-like giant cells, which are responsible for the significant local bone resorption seen in these lesions. These cells, along with mononuclear stromal cells, contribute to the rapid expansion and lytic destruction of the surrounding bone. Osteoblasts are bone-forming cells, chondrocytes are cartilage cells, osteocytes are mature bone cells, and adipocytes are fat cells.

Question 12547

Topic: 1. General Principles & Basic Science

Which type of adjuvant therapy used with curettage of an ABC works by desiccating and coagulating residual cells through direct application, without significant thermal injury to surrounding tissues beyond the immediate contact?

. Cryotherapy (liquid nitrogen)
. Phenol
. Argon beam coagulation
. Hydrogen peroxide
. Electrocautery

Correct Answer & Explanation

. Argon beam coagulation

Explanation

Argon beam coagulation (ABC) uses a jet of argon gas to deliver electrical current to the tissue, causing desiccation and coagulation of cells. It allows for broad, superficial treatment of the cyst wall with minimal depth of penetration, thus minimizing damage to underlying vital structures, which can be an advantage over cryotherapy or phenol in certain locations. Cryotherapy works by freezing/thawing. Phenol is a chemical cauterant. Hydrogen peroxide is a mild antiseptic. Electrocautery is more localized and generates more heat.

Question 12548

Topic: 1. General Principles & Basic Science

A 9-year-old male has an ABC in the proximal tibia extending to the subchondral bone of the knee joint. Surgical planning must carefully consider preserving the articular cartilage. What specific intraoperative technique can help minimize damage to the articular cartilage during curettage?

. Using a larger curette to remove more bone rapidly.
. Performing a wide en bloc resection.
. Creating a cortical window away from the articular surface and curetting from within.
. Aggressively using a high-speed burr on the articular surface.
. Employing strong traction across the joint.

Correct Answer & Explanation

. Creating a cortical window away from the articular surface and curetting from within.

Explanation

When an ABC extends to the subchondral bone, preserving the articular cartilage is paramount to prevent early degenerative changes. A common strategy is to create a cortical window (corticotomy) at a safe distance from the articular surface, then perform curettage of the cyst from within this window, avoiding direct disruption of the articular cartilage. Aggressive burring on the articular surface or using larger curettes directly under it would cause damage. En bloc resection is typically avoided for joint-preserving procedures. Strong traction alone does not protect cartilage from direct instrument damage.

Question 12549

Topic: 1. General Principles & Basic Science

What is the typical age range for the diagnosis of Hereditary Multiple Exostoses (HME)?

. Usually detected at birth
. Typically diagnosed in infancy (0-2 years)
. Most commonly diagnosed in early childhood (2-10 years)
. Primarily diagnosed in adolescence (10-18 years)
. Usually after skeletal maturity (post-18 years)

Correct Answer & Explanation

. Most commonly diagnosed in early childhood (2-10 years)

Explanation

Hereditary Multiple Exostoses (HME) is most commonly diagnosed in early childhood (typically between 2 and 10 years of age) when the lesions become large enough to be palpable or cause symptoms. While some lesions might be detected earlier or later, early childhood is the peak diagnostic period. They are rarely apparent at birth.

Question 12550

Topic: Surgical Anatomy & Approaches

When performing limb salvage for a proximal humeral osteosarcoma, which nerve is at greatest risk of injury during the surgical approach and dissection around the axilla?

. Radial nerve
. Ulnar nerve
. Median nerve
. Axillary nerve
. Musculocutaneous nerve

Correct Answer & Explanation

. Axillary nerve

Explanation

During surgery for proximal humeral tumors, especially involving the deltoid and surgical neck, the axillary nerve is at the greatest risk of injury. It courses around the surgical neck of the humerus, innervating the deltoid and teres minor. Damage to this nerve results in deltoid paralysis and significant shoulder dysfunction. The radial, ulnar, and median nerves are typically more distal or protected within the neurovascular bundle, though they are always at risk in extensive resections.

Question 12551

Topic: Infection, Pharmacology & VTE

What is the most common immediate post-operative complication following endoprosthetic reconstruction for distal femoral osteosarcoma?

. Deep vein thrombosis
. Periprosthetic fracture
. Infection
. Nerve injury
. Pulmonary embolism

Correct Answer & Explanation

. Infection

Explanation

Infection is the most common and devastating complication following endoprosthetic reconstruction for tumor resection, particularly in osteosarcoma patients who are often immunocompromised from chemotherapy. The incidence can range from 5-20%. While DVT, PE, periprosthetic fracture, and nerve injury can occur, infection remains the most frequent major complication. Mechanical loosening and aseptic failure are also long-term issues.

Question 12552

Topic: Biomechanics & Biomaterials

In the context of limb salvage surgery for osteosarcoma, what is the main purpose of cement augmentation or polymethylmethacrylate (PMMA) during prosthetic fixation?

. To provide an osteoinductive surface for bone ingrowth.
. To act as a heat sink, preventing thermal injury to surrounding tissues.
. To provide immediate rigid fixation and potentially local chemotherapy delivery.
. To reduce the risk of infection by releasing antibiotics.
. To stimulate bone remodeling and healing around the implant.

Correct Answer & Explanation

. To provide immediate rigid fixation and potentially local chemotherapy delivery.

Explanation

PMMA (bone cement) is primarily used in prosthetic reconstruction to provide immediate, rigid fixation of the implant to the bone. Its rapid polymerization and mechanical interlock create a strong interface. Additionally, antibiotics (e.g., gentamicin, vancomycin) can be mixed into the cement, providing local antibiotic delivery and reducing the risk of infection, which is a major concern in these complex surgeries. It does not provide osteoinduction, act as a heat sink (it produces heat during polymerization), or primarily stimulate bone remodeling.

Question 12553

Topic: Surgical Anatomy & Approaches

A patient undergoes curettage for a presumed enchondroma. Intraoperatively, the lesion appears more aggressive than expected. What is the most crucial step regarding the excised tissue?

. Discard the tissue if it looks benign
. Send for immediate frozen section analysis by a musculoskeletal pathologist
. Send only a small fragment for routine pathology
. Preserve in saline for later analysis
. Send for genetic testing only

Correct Answer & Explanation

. Send for immediate frozen section analysis by a musculoskeletal pathologist

Explanation

If the intraoperative appearance of a lesion suggests malignancy despite a preoperative diagnosis of enchondroma, an immediate frozen section analysis by an experienced musculoskeletal pathologist is crucial. This rapid assessment can guide the surgeon in extending resection margins or changing the surgical approach during the same procedure, optimizing patient outcomes. Discarding tissue or sending only small fragments would be inappropriate.

Question 12554

Topic: 1. General Principles & Basic Science

Why are plain radiographs often sufficient for follow-up of stable, asymptomatic enchondromas?

. They are more sensitive than MRI for small changes
. They are excellent for soft tissue characterization
. They effectively demonstrate calcification patterns and cortical changes
. They involve no radiation exposure
. They are superior for detecting subtle marrow edema

Correct Answer & Explanation

. They effectively demonstrate calcification patterns and cortical changes

Explanation

Plain radiographs are cost-effective, readily available, and provide good visualization of the key features relevant to enchondroma follow-up, such as the pattern of matrix calcifications, cortical integrity (e.g., thinning, scalloping), and overall size/stability of the lesion. While not as sensitive for soft tissue or marrow changes as MRI, these are typically not concerns for a stable, asymptomatic enchondroma. They do involve radiation, unlike MRI or ultrasound.

Question 12555

Topic: Surgical Anatomy & Approaches

Regarding the surgical approach for a posterior wall acetabular fracture, what is a critical consideration to prevent iatrogenic sciatic nerve injury?

. Limiting hip flexion during exposure
. Avoiding release of the piriformis muscle
. Minimizing traction on the inferior gluteal artery
. Placing retractors deep to the short external rotators but superficial to the nerve
. Utilizing a modified Stoppa approach

Correct Answer & Explanation

. Placing retractors deep to the short external rotators but superficial to the nerve

Explanation

When using the Kocher-Langenbeck approach for posterior wall acetabular fractures, the sciatic nerve lies deep to the short external rotators (gemelli, obturator internus, quadratus femoris). Careful placement of retractors superficial to the sciatic nerve but deep to these muscles is crucial to avoid direct nerve compression or stretching, which can lead to iatrogenic injury. Limiting hip flexion helps prevent excessive tension on the nerve. The Stoppa approach is an anterior approach and not relevant to a posterior wall fracture. Avoiding piriformis release is not a primary factor in sciatic nerve protection specific to retractors.

Question 12556

Topic: Surgical Anatomy & Approaches

Which of the following describes a key risk of the anterior approach (ilioinguinal) for acetabular fracture fixation?

. Sciatic nerve injury
. Superior gluteal artery injury
. Lateral femoral cutaneous nerve injury
. Posterior femoral cutaneous nerve injury
. Common peroneal nerve injury

Correct Answer & Explanation

. Lateral femoral cutaneous nerve injury

Explanation

The lateral femoral cutaneous nerve (LFCN) is particularly vulnerable during the ilioinguinal approach for acetabular fractures as it crosses the iliac crest and passes through or under the inguinal ligament. Injury can lead to meralgia paresthetica (pain, numbness, or burning sensation on the lateral thigh). Sciatic nerve injury is a risk with posterior approaches. Superior gluteal artery injury is a risk with iliosacral screw placement. Posterior femoral cutaneous and common peroneal nerves are not typically at risk with an anterior ilioinguinal approach.

Question 12557

Topic: 1. General Principles & Basic Science

A 25-year-old male sustains a knee dislocation with immediate severe swelling and loss of distal pulses. After successful reduction in the emergency department, what is the next most appropriate step in management?

. MRI of the knee to assess ligamentous injury
. Immediate operative exploration of the popliteal artery
. CT angiogram of the lower extremity
. Begin passive range of motion exercises
. Long leg cast immobilization and observation

Correct Answer & Explanation

. Immediate operative exploration of the popliteal artery

Explanation

Any knee dislocation, particularly with a hard sign of vascular injury (loss of pulses), constitutes a limb-threatening emergency. After reduction, the immediate priority is to assess and restore vascular integrity. Persistent absent pulses despite reduction mandate immediate operative exploration of the popliteal artery, as delaying revascularization can lead to limb ischemia and amputation. While a CT angiogram can localize injury, operative exploration should not be delayed if pulses are absent after reduction. MRI and physiotherapy are for later ligamentous assessment and rehabilitation, respectively. Immobilization alone is insufficient.

Question 12558

Topic: Infection, Pharmacology & VTE

A 60-year-old male with multiple comorbidities sustains a stable, non-displaced minimally comminuted subtrochanteric fracture. He is deemed a very poor surgical candidate. What non-operative management strategy could be considered?

. Immediate weight-bearing as tolerated in a brace
. Short leg cast immobilization
. Bed rest and skeletal traction for 12 weeks
. Dynamic hip screw (DHS) in traction
. Spica cast

Correct Answer & Explanation

. Spica cast

Explanation

For extremely frail or medically unstable patients who cannot tolerate surgery for even stable subtrochanteric fractures, prolonged bed rest with skeletal traction can be a salvage non-operative option. This aims to maintain alignment and reduce pain, though it carries significant risks of complications associated with prolonged recumbency (e.g., pressure sores, DVT/PE, pneumonia). It is a measure of last resort. Immediate weight-bearing, short leg casts, or spica casts are inappropriate for subtrochanteric fractures. DHS is a surgical option.

Question 12559

Topic: Surgical Anatomy & Approaches

Which surgical approach for acetabular fractures offers the best visualization of the anterior column, posterior column, and quadrilateral surface simultaneously?

. Kocher-Langenbeck approach
. Ilioinguinal approach
. Modified Stoppa approach (pararectus or infrapectineal)
. Extended iliofemoral approach
. Anterior approach (Smith-Petersen)

Correct Answer & Explanation

. Modified Stoppa approach (pararectus or infrapectineal)

Explanation

The modified Stoppa approach (pararectus or infrapectineal approach) combined with a limited ilioinguinal approach or alone, offers excellent direct visualization of the anterior column, posterior column (from the inside of the pelvis via the quadrilateral surface), and the quadrilateral surface. This approach has gained popularity for its ability to address both columns through a single incision in many complex fracture patterns. The Kocher-Langenbeck is posterior. Ilioinguinal provides anterior and middle window access. The extended iliofemoral is a massive approach with significant morbidity. The Smith-Petersen is less extensive and generally for hip arthroplasty.

Question 12560

Topic: 1. General Principles & Basic Science

Which of the following age groups is most commonly affected by Non-Ossifying Fibroma (NOF)?

. Infancy (0-2 years)
. Early childhood (2-6 years)
. Late childhood and adolescence (5-15 years)
. Young adulthood (20-30 years)
. Elderly (>60 years)

Correct Answer & Explanation

. Late childhood and adolescence (5-15 years)

Explanation

Non-ossifying fibromas are most commonly found in children and adolescents, typically between the ages of 5 and 15 years. They are rare in infancy and adulthood, often resolving by skeletal maturity.

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