A 21-year-old man presents to the emergency department after sustaining a stab wound to the neck at a local farmer's market. The patient is otherwise healthy and is complaining of pain. The patient is able to offer the history himself. His temperature is 97.6°F (36.4°C), blood pressure is 120/84 mmHg, pulse is 90/min, respirations are 15/min, and oxygen saturation is 98% on room air. Physical exam demonstrates a 3 cm laceration 1 cm inferior to the mastoid process on the right side. The patient's breath sounds are clear and he is protecting his airway. No stridor or difficulty breathing is noted. Which of the following is the most appropriate next step in the management of this patient?

Observation and blood pressure monitoring

A 22-year-old man presents to the emergency department after being tackled in a game of football. The patient was hit from behind and fell to the ground. After the event, he complained of severe pain in his knee. The patient has a past medical history of anabolic steroid use. His current medications include whey protein supplements, multivitamins, and fish oil. His temperature is 99.5°F (37.5°C), blood pressure is 137/68 mmHg, pulse is 100/min, respirations are 17/min, and oxygen saturation is 98% on room air. On physical exam, you see a muscular young man clutching his knee in pain. The knee is inflamed and erythematous. When valgus stress is applied to the leg, there is some laxity when compared to the contralateral leg. The patient is requesting surgery for his injury. Arthrocentesis is performed and demonstrates no abnormalities of the synovial fluid. Which of the following physical exam findings is most likely to be seen in this patient?

A palpable click with passive motion of the knee

Anterior displacement of the femur relative to the tibia

Severe pain with compression of the patella

Anterior displacement of the tibia relative to the femur

A 50-year-old man presents to the emergency department with pain and swelling of his right leg for the past 2 days. Three days ago he collapsed on his leg after tripping on a rug. It was a hard fall and left him with bruising of his leg. Since then the pain and swelling of his leg have been gradually increasing. Past medical history is noncontributory. He lives a rather sedentary life and smokes two packs of cigarettes per day. The vital signs include heart rate 98/min, respiratory rate 15/min, temperature 37.8°C (100.1°F), and blood pressure 100/60 mm Hg. On physical examination, his right leg is visibly swollen up to the mid-calf with pitting edema and moderate erythema. Peripheral pulses in the right leg are weak and the leg is tender. Manipulation of the right leg is negative for Homan’s sign. What is the next best step in the management of this patient?

Send the patient to surgery for an emergency fasciotomy

Start intravenous heparin therapy immediately

Make a diagnosis of deep vein thrombosis based on history and physical

Perform intravenous venography within 24 hours

A 19-year-old man comes to the emergency department for right wrist pain and swelling 2 hours after falling on an outstretched hand while playing softball. The pain worsened when he attempted to pitch after the fall. He has eczema and type 1 diabetes mellitus. Current medications include insulin and topical clobetasol. He appears uncomfortable. Examination shows multiple lichenified lesions over his forearms. The right wrist is swollen and tender; range of motion is limited by pain. There is tenderness to palpation in the area between the tendons of the abductor pollicis longus, extensor pollicis brevis, and extensor pollicis longus muscle. The thumb can be opposed actively towards the other fingers. Muscle strength of the right hand is decreased. Which of the following is the most likely diagnosis?

Transscaphoid perilunate dislocation

A crying 4-year-old child is brought to the emergency department with a red, swollen knee. He was in his usual state of health until yesterday, when he sustained a fall in the sandbox at the local park. His mother saw it happen; she says he was walking through the sandbox, fell gently onto his right knee, did not cry or seem alarmed, and returned to playing without a problem. However, later that night, his knee became red and swollen. It is now painful and difficult to move. The child’s medical history is notable for frequent bruising and prolonged bleeding after circumcision. On physical exam, his knee is erythematous, tender, and swollen, with a limited range of motion. Arthrocentesis aspirates frank blood from the joint. Which of the following single tests is most likely to be abnormal in this patient?

Partial thromboplastin time (PTT)

A 35-year-old male is brought into the emergency department for a trauma emergency. The emergency medical services states that the patient was wounded with a knife on his upper left thigh near the inguinal ligament. Upon examination in the trauma bay, the patient is awake and alert. His physical exam and FAST exam is normal other than the knife wound. Large bore intravenous lines are inserted into the patient for access and fluids are being administered. Pressure on the knife wound is being held by one of the physicians with adequate control of the bleeding, but the physician notices the blood was previously extravasating in a pulsatile manner. His vitals are BP 100/50, HR 110, T 97.8, RR 22. What is the next best step for this patient?

Coagulation studies and blood typing/crossmatch

Tourniquet of proximal lower extremity

Extremity trauma and vascular injuries for USMLE Step 1: High-Yield Surgery Lessons

Initial Assessment - First Look & Fix

Exsanguinating Hemorrhage: Control immediately with direct pressure or tourniquet.
Vascular Exam: Assess for hard & soft signs of vascular injury.
- Hard Signs: Pulsatile bleeding, expanding hematoma, audible bruit, palpable thrill, absent distal pulses.
- Soft Signs: History of hemorrhage, diminished pulses, adjacent nerve injury.
📌 6 P's of Ischemia: Pain, Pallor, Pulselessness, Paresthesia, Paralysis, Poikilothermia.

Algorithm for vascular injury assessment

⭐ A normal pulse exam does not rule out a clinically significant vascular injury. Up to 20% of patients with arterial injuries can have palpable distal pulses.

Vascular Injuries - Red Flags & Reroutes

Hard Signs (Red Flags) → Straight to OR
- Pulsatile bleeding, expanding hematoma
- Audible bruit, palpable thrill
- Signs of distal ischemia (6 P's)
- Absent distal pulses
Soft Signs → Further Investigation
- History of major bleeding
- Diminished pulses
- Associated nerve deficit
- Significant bony injury (e.g., knee dislocation)

⭐ Following a knee dislocation, a normal distal pulse does NOT rule out a popliteal artery injury. Perform an Ankle-Brachial Index (ABI); if < 0.9, a CTA is mandatory due to high risk of intimal tear and delayed thrombosis.

Knee dislocation with popliteal artery transection

Fractures & Dislocations - Snaps, Cracks & Pops

General: Open (skin breach) vs. Closed. Simple (2 fragments) vs. Comminuted (>2 fragments).
Specific Injuries:
- Colles' Fx: Distal radius, dorsal displacement ("dinner fork"). Common with FOOSH.
- Scaphoid Fx: Anatomical snuffbox tenderness. High risk of avascular necrosis (AVN).
- Hip Fx: Leg shortened & externally rotated. High mortality in elderly.
- Shoulder Dislocation: Anterior is most common; risk of axillary nerve injury.
Complications:
- Compartment Syndrome: ⚠️ Pain out of proportion. 📌 6 P's: Pain, Paresthesia, Pallor, Pulselessness, Poikilothermia, Paralysis.
- Fat Embolism: From long bone fx. Triad: neurologic changes, respiratory distress, petechial rash.

⭐ Scaphoid fractures can be occult on initial X-ray. If snuffbox tenderness is present, immobilize in a thumb spica cast and repeat imaging in 1-2 weeks to prevent AVN.

$Lateral X-ray of Colles fracture with dorsal displacement$

Compartment Syndrome - The Pressure Cooker

Pathophysiology: Increased pressure within a closed fascial compartment, leading to compromised blood flow and tissue necrosis.
Causes: Primarily long bone fractures (e.g., tibia, supracondylar), crush injuries, reperfusion swelling.
Clinical Signs (The 6 P's): 📌 Pain out of proportion to injury, Paresthesias, Pallor, Paralysis, Pulselessness, and Poikilothermia (coldness).
Diagnosis: Primarily clinical. Compartment pressure > 30-45 mmHg warrants fasciotomy. Consider if $P_{diastolic} - P_{compartment} < 20-30$ mmHg.

⭐ Pain on passive stretch of the affected muscles is the most sensitive early sign.

Lower Leg Compartment Syndrome Pathophysiology

High‑Yield Points - ⚡ Biggest Takeaways

Hard signs of vascular injury (e.g., pulsatile bleeding, expanding hematoma, bruit/thrill) mandate immediate surgical exploration.

Soft signs (e.g., diminished pulses, non-expanding hematoma) warrant an Ankle-Brachial Index (ABI); if < 0.9, proceed to CTA.

Compartment syndrome's earliest sign is pain out of proportion; pulselessness is a late finding. Treatment is emergent fasciotomy.

Knee dislocations carry a high risk of popliteal artery injury.

Suspect fat embolism syndrome (petechial rash, hypoxemia, neurologic changes) after long bone fractures.

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