- The patient's post-reduction findings are most likely due to an injury to which of the following nerves?
Answer: Axillary nerve
The most common type of shoulder dislocation is anterior, which can stretch or damage the axillary nerve as it wraps around the surgical neck of the humerus. Axillary nerve injury results in paralysis of the deltoid muscle (inability to abduct the arm) and teres minor, as well as loss of sensation over the lateral shoulder, an area known as the 'regimental badge' area.
- A 29-year-old skier falls, resulting in acute right knee pain and hemarthrosis. Lachman test is positive; tibial plateau tenderness is absent. What additional finding is most likely on physical examination?
Answer: Anterior drawer of >6 mm at 90° flexion indicating anterior cruciate ligament rupture
When you encounter an acute knee injury with hemarthrosis (blood in the joint) and a positive Lachman test, you're dealing with an ACL tear. The key is understanding that ACL injuries rarely occur in isolation—they often involve additional structures due to the mechanism of injury.
The positive Lachman test already confirms ACL rupture by demonstrating anterior tibial translation relative to the femur. The anterior drawer test at 90° flexion (choice A) is another way to assess ACL integrity and would logically be positive in this scenario, showing >6 mm of anterior displacement. Both tests evaluate the same structure but at different knee flexion angles—Lachman at 20-30° and anterior drawer at 90°.
Choice B describes McMurray's test findings for meniscal tears. While meniscal injuries can accompany ACL tears, the question stem doesn't provide information suggesting meniscal involvement.
Choice C indicates MCL injury through valgus stress testing. Though MCL tears often occur with ACL injuries (part of the "unhappy triad"), excessive valgus opening isn't the most likely additional finding given the clinical presentation.
Choice D describes PCL injury via the posterior sag sign. PCL tears typically result from posterior-directed forces (dashboard injuries) rather than the anterior-directed mechanisms that cause ACL tears in skiing accidents.
Study tip: Remember that multiple ACL tests exist (Lachman, anterior drawer, pivot shift), and a positive result on one strongly predicts positive results on the others. Focus on understanding the mechanism of injury to predict associated structures involved.
- A 25-year-old man is stabbed in the right thigh. Bedside Doppler confirms biphasic dorsalis pedis and posterior tibial signals. CT angiography shows a 2 mm intimal flap of the superficial femoral artery without flow limitation. Optimal management?
Answer: Observation with serial ankle-brachial indices and antiplatelet therapy
When you encounter vascular trauma with minimal injury on imaging, the key decision point is whether the injury requires immediate intervention or can be managed conservatively. Small intimal flaps without hemodynamic compromise often heal spontaneously.
This patient has preserved distal perfusion evidenced by biphasic Doppler signals at both the dorsalis pedis and posterior tibial arteries, indicating adequate collateral circulation. The 2mm intimal flap without flow limitation represents a minor arterial injury that doesn't compromise limb viability. Conservative management with observation is appropriate here, using serial ankle-brachial indices (ABIs) to monitor for any deterioration in distal perfusion, while antiplatelet therapy helps prevent thrombosis at the injury site.
Choice B (open repair with vein grafting) is unnecessarily invasive for such a minor injury and carries surgical risks that outweigh benefits when perfusion is maintained. Choice C (fasciotomy) addresses compartment syndrome, which isn't indicated here since there's no evidence of tissue ischemia or elevated compartment pressures. Choice D (endovascular stenting) is reserved for more significant arterial injuries with flow compromise or when conservative management fails.
The correct answer is A because this represents appropriate conservative management for a hemodynamically insignificant arterial injury with preserved distal perfusion.
Remember this pattern: in vascular trauma, if distal pulses are present and imaging shows minimal injury without flow limitation, start with observation and serial monitoring. Reserve invasive interventions for cases with compromised perfusion, expanding hematomas, or failed conservative management.
- Which of the following is the most critical diagnostic procedure to perform?
Answer: Arthrocentesis with synovial fluid analysis
The presentation of a single, hot, swollen, and painful joint (monoarticular arthritis) with systemic fever is highly concerning for septic arthritis, which is an orthopedic emergency. However, it can also be mimicked by a crystal arthropathy like gout or pseudogout. The only definitive way to distinguish between these possibilities is to perform an arthrocentesis (joint aspiration) and analyze the synovial fluid for cell count with differential, Gram stain, culture, and crystal analysis. A white blood cell count >50,000/microL in synovial fluid is highly suggestive of septic arthritis.
- While awaiting the MRI results, which of the following interventions should be administered immediately?
Answer: High-dose intravenous corticosteroids
This patient's presentation is highly concerning for metastatic spinal cord compression, a neurologic emergency. The combination of cancer history, worsening back pain (especially at night), and new neurologic deficits (weakness, incontinence) warrants immediate action. High-dose intravenous corticosteroids (e.g., dexamethasone) should be administered immediately, even before definitive imaging is completed, to reduce vasogenic edema around the spinal cord and potentially alleviate cord compression, preserving neurologic function.
- Which of the following is the most likely diagnosis?
Answer: Vertebral compression fracture
The acute onset of severe, localized back pain after a minimal trauma event (like sneezing or coughing) in an elderly patient with osteoporosis is the classic presentation of a vertebral compression fracture. The localized point tenderness over the affected vertebra is a key physical finding. The absence of neurologic deficits makes other causes like a large disc herniation or severe stenosis less likely.
- A 42-year-old warehouse employee complains of posterior heel pain after feeling a "pop" while jumping. Exam shows a palpable gap 5 cm proximal to the calcaneal insertion and inability to plantarflex against resistance. What factor most strongly predicts poor functional outcome after surgical repair?
Answer: Delay of more than 6 weeks between injury and operative repair
This clinical scenario describes a classic Achilles tendon rupture. When you encounter questions about surgical outcomes for tendon injuries, timing of repair is almost always the critical factor that determines functional recovery.
The correct answer is A because delayed surgical repair beyond 6 weeks dramatically worsens outcomes. After this timeframe, the tendon ends retract significantly, muscle atrophy progresses, and scar tissue formation makes primary repair technically challenging or impossible. Studies consistently show that patients with delayed repair have reduced strength, decreased range of motion, and higher complication rates. The "golden period" for optimal Achilles repair is within the first 2-3 weeks, with acceptable results possible up to 6 weeks.
Option B is incorrect because age over 40, while associated with higher injury risk, doesn't strongly predict poor surgical outcomes when repair is performed promptly. Option C represents a smoking history that, while potentially affecting wound healing, is moderate and doesn't override the importance of surgical timing. Many smokers achieve good functional outcomes with timely repair. Option D describes Class I obesity (BMI 30-34.9), which may complicate surgery but again doesn't predict poor outcomes as strongly as surgical delay.
For USMLE Step 2, remember that orthopedic outcome questions frequently test your knowledge of surgical timing. Whether it's Achilles ruptures, rotator cuff tears, or fractures, delayed intervention typically trumps patient factors like age, smoking, or weight as the primary predictor of poor outcomes. Focus on learning the critical time windows for common orthopedic procedures.
- Which of the following is the most definitive step to diagnose the suspected condition?
Answer: Measurement of intracompartmental pressures
The clinical picture strongly suggests acute compartment syndrome of the forearm. The classic 'P's are present: Pain out of proportion, Pain with passive stretch, Paresthesias, and a tense compartment (Palpation). While the clinical diagnosis is often sufficient to proceed to surgery, the most definitive and objective diagnostic test is the direct measurement of intracompartmental pressures using a pressure monitor. A pressure >30 mmHg or a diastolic delta pressure <30 mmHg confirms the diagnosis and is an indication for emergent fasciotomy.
- Based on this presentation, which of the following is the most appropriate next step?
Answer: Provide conservative management with rest, ice, compression, and elevation (RICE).
This patient's presentation meets the criteria for low risk according to the Ottawa ankle rules, which are used to determine the need for radiography in acute ankle injuries. The rules state that imaging is not required if there is no bony tenderness in the specified malleolar or midfoot zones AND the patient is able to bear weight (take 4 steps) both immediately after the injury and in the emergency department/clinic. Since she meets these criteria, radiographs are unnecessary, and conservative management for a likely ankle sprain is appropriate.
- Which of the following is the most important next step in management?
Answer: Perform emergent surgical exploration and debridement.
This patient's presentation, with pain out of proportion, rapidly progressing cellulitis, bullae, systemic signs of toxicity (sepsis), and crepitus (suggesting gas-producing organisms), is highly suggestive of necrotizing fasciitis. This is a life-threatening surgical emergency. While broad-spectrum antibiotics are crucial and should be started immediately, the definitive and most critical step is emergent surgical debridement of all necrotic tissue. Delaying surgery for imaging or culture results significantly increases mortality.
- This physical examination finding is most consistent with an injury to which of the following structures?
Answer: Anterior cruciate ligament
The clinical scenario describes a classic mechanism for an anterior cruciate ligament (ACL) tear: a non-contact, pivoting injury associated with a 'pop,' rapid hemarthrosis (swelling), and instability. The described physical examination finding is a positive Lachman test, which is the most sensitive test for an ACL tear. It assesses for anterior translation of the tibia relative to the femur.
- A 35-year-old construction worker is brought to the ED after a steel beam crushes his left leg for 45 minutes. Examination shows swollen tense calf compartments, pain out of proportion to exam, and pain with passive dorsiflexion. Distal pulses are palpable. What is the best next step?
Answer: Measure intracompartmental pressures and perform emergent fasciotomy if >30 mm Hg
When you encounter a trauma case with swollen, tense compartments and pain out of proportion to examination findings, think compartment syndrome. This is a surgical emergency where increased pressure within fascial compartments compromises circulation and threatens tissue viability.
The classic presentation includes the "5 P's": Pain (especially with passive stretch), Pressure (tense compartments), Paresthesias, Pallor, and Pulselessness. Critically, distal pulses can remain palpable even with compartment syndrome because arterial pressure typically exceeds compartmental pressure. Loss of pulses is actually a late finding indicating irreversible damage.
Choice A is correct because compartment syndrome is primarily a clinical diagnosis, but measuring intracompartmental pressures can confirm your suspicion when the diagnosis is uncertain. Normal compartment pressure is <10 mm Hg; pressures >30 mm Hg (or within 30 mm Hg of diastolic blood pressure) indicate compartment syndrome requiring immediate fasciotomy to prevent permanent nerve and muscle damage.
Choice B delays necessary treatment. While vascular injury is possible, the clinical picture screams compartment syndrome, which takes priority. Choice C represents dangerous conservative management - elevation can actually worsen compartment syndrome by decreasing arterial inflow, and mannitol won't address the underlying problem. Choice D completely misses the diagnosis and could worsen the condition by external compression.
Remember: compartment syndrome is a "can't miss" diagnosis on Step 2. When you see trauma + tense compartments + pain with passive stretch, think emergency fasciotomy regardless of pulse status. Time is muscle and nerve.
- Which of the following is the most appropriate next step in management?
Answer: Perform an emergent MRI of the lumbosacral spine.
This patient's presentation of saddle anesthesia, bilateral lower extremity weakness, and bowel/bladder dysfunction is classic for cauda equina syndrome, a neurosurgical emergency. The most critical next step is to obtain an emergent MRI of the lumbosacral spine to confirm the diagnosis and identify the level of compression, which will guide immediate surgical decompression. Delay in diagnosis and treatment can lead to permanent neurologic deficits.
- Which of the following diagnostic studies is most appropriate to confirm the suspected diagnosis?
Answer: MRI of the knee
The patient's history of a twisting injury followed by mechanical symptoms like locking and catching, along with joint line tenderness and a positive McMurray test (as described), is highly suggestive of a meniscal tear. MRI is the non-invasive imaging modality of choice for diagnosing meniscal and other soft-tissue injuries of the knee. Plain radiographs are typically normal but may be done to rule out fracture or arthritis. Arthrocentesis would be indicated for a large, acute effusion to rule out infection or gout.
- During a soccer game, a 16-year-old girl collides with another player and develops immediate knee swelling. X-ray is normal. After aspiration yields fat-stained bloody fluid, what is the next best step?
Answer: Order MRI of the knee to identify an occult tibial plateau fracture and plan management
When you encounter a knee injury with immediate swelling and bloody synovial fluid containing fat globules, you're dealing with a classic presentation that demands systematic thinking about occult fractures.
The presence of fat-stained (lipohemarthrosis) fluid is pathognomonic for an intraarticular fracture, even when initial X-rays appear normal. Fat globules enter the joint space from exposed bone marrow when fracture occurs. In young athletes with knee trauma, tibial plateau fractures are common but can be subtle on plain radiographs, especially nondisplaced or compression-type fractures.
Option A is correct because MRI is the gold standard for detecting occult fractures that X-rays miss. The fat-stained fluid makes fracture virtually certain, and you must identify the specific location and extent to plan appropriate management, as tibial plateau fractures often require surgical intervention.
Option B is dangerous because allowing weight bearing on an undiagnosed fracture could cause displacement and worsen the injury. The lipohemarthrosis already confirms fracture presence.
Option C focuses on soft tissue pathology, but arthroscopy won't adequately evaluate bony structures. While meniscal tears can cause bloody fluid, they don't produce fat globules.
Option D assumes a ligamentous injury and recommends aggressive therapy, which could be catastrophic if an unstable fracture is present.
Remember this key principle: lipohemarthrosis (fat in bloody joint fluid) equals fracture until proven otherwise. Always pursue advanced imaging to locate the fracture before making any treatment decisions, regardless of normal X-rays.
- This physical examination finding is pathognomonic for which of the following injuries?
Answer: Achilles tendon rupture
The clinical presentation and physical examination findings are classic for an Achilles tendon rupture. The described maneuver, squeezing the calf muscle to elicit plantarflexion, is the Thompson test. An absence of plantarflexion during this test indicates a complete rupture of the Achilles tendon.
- A 46-year-old man fractures his humeral shaft in a fall. Examination reveals wrist drop and numbness over the dorsal hand. Radial pulses are normal. What management step is indicated now?
Answer: Apply a functional brace and schedule follow-up; the neuropraxia usually recovers
When you encounter a humeral shaft fracture with radial nerve injury, you need to understand the anatomy and natural history of radial neuropathy. The radial nerve travels in the spiral groove of the mid-humerus, making it vulnerable to injury in shaft fractures. However, most radial nerve injuries associated with closed humeral fractures are neuropraxias (temporary conduction blocks) rather than complete nerve transections.
The correct approach is A) Apply a functional brace and schedule follow-up; the neuropraxia usually recovers. Studies show that 70-90% of radial nerve palsies associated with humeral shaft fractures recover spontaneously within 3-6 months. Since the radial pulse is normal (indicating no vascular compromise) and this is likely a closed fracture, conservative management with observation is appropriate. The functional brace allows fracture healing while maintaining some mobility.
B) Proceed to emergent surgical exploration is incorrect because immediate surgery isn't indicated for closed fractures with radial nerve palsy. Surgery is reserved for open fractures, vascular compromise, or cases where nerve recovery doesn't occur after 3-4 months of observation.
C) Order urgent electromyography is wrong because EMG changes don't appear until 2-3 weeks after nerve injury, making urgent testing useless for acute management decisions.
D) Administer high-dose corticosteroids is incorrect as there's no evidence supporting steroid use for traumatic peripheral nerve injuries, unlike some central nervous system injuries.
Key takeaway: For closed humeral shaft fractures with radial nerve palsy, "wait and watch" is the standard approach. Most recover spontaneously, and early surgery doesn't improve outcomes.
- Which of the following is the most appropriate next step in management?
Answer: Bivalve the cast and measure intracompartmental pressures.
This patient has classic signs and symptoms of acute compartment syndrome: pain out of proportion to the injury, pain with passive stretch, paresthesias, and a tense compartment. The presence of a pulse does not rule out this diagnosis. The immediate first step is to relieve all external pressure, which includes bivalving (cutting) the cast and any underlying padding down to the skin. The definitive diagnosis is then confirmed by measuring intracompartmental pressures. If pressures are elevated (typically >30 mmHg or a delta pressure <30 mmHg), an emergent fasciotomy is required.
- Given the 'red flag' symptoms in this patient, which of the following is the most appropriate initial step in her evaluation?
Answer: Plain radiographs of the lumbar spine and measurement of ESR/CRP.
This patient presents with multiple 'red flags' for a serious underlying cause of back pain, such as malignancy or infection. These flags include age >50, significant smoking history (risk factor for lung cancer with potential spinal metastases), unintentional weight loss, and night pain not relieved by rest. In a patient with red flags but no neurologic deficits, the appropriate initial workup includes plain radiographs to look for obvious bony lesions and inflammatory markers (ESR, CRP) to screen for an inflammatory or infectious process. While plain films may be normal early in metastatic disease, they are the appropriate initial imaging. An emergent MRI is reserved for patients with suspected cauda equina syndrome, spinal cord compression, or when initial workup suggests malignancy.
- Despite the benign initial appearance, which of the following is the most appropriate management for this injury?
Answer: Arrange for urgent surgical exploration and debridement.
High-pressure injection injuries are surgical emergencies. The injected material can travel far along fascial planes and tendon sheaths, causing extensive tissue damage, ischemia, and inflammation, which may not be apparent on initial examination. The seemingly benign entry wound belies the severe internal injury. Urgent surgical exploration, debridement of foreign material and necrotic tissue, and broad-spectrum antibiotics are required to prevent devastating complications such as compartment syndrome, infection, and amputation.
