A 32-year-old man is evaluated in the surgical intensive care unit for severe right lower … — USMLE Step 2 CK

A $32$ -year-old man is evaluated in the surgical intensive care unit for severe right lower extremity pain. $12$ hours ago, he underwent closed reduction and intramedullary nailing for a comminuted right tibial shaft fracture sustained in a high-speed skiing accident. He reports that the pain has progressively worsened over the last $3$ hours and is now "unbearable," describing it as a deep, burning ache. The pain is completely unresponsive to multiple doses of intravenous morphine. His temperature is $37.4^\circ\text{C}$ ( $99.3^\circ\text{F}$ ), blood pressure is $148/92 \text{ mmHg}$ , pulse is $118/\text{min}$ , and respiratory rate is $22/\text{min}$ . On physical examination, the right leg is tensely swollen, shiny, and exceedingly firm to palpation. Passive plantar flexion of the right ankle and toes elicits excruciating pain. Sensation to light touch is markedly decreased over the first dorsal web space of the right foot. The dorsalis pedis and posterior tibial pulses are palpable and symmetric to the contralateral side. Which of the following is the most appropriate next step in management?

Immediate four-compartment fasciotomy of the right lower legAnswer
B
Transport to the radiology suite for computed tomography angiography of the right lower extremity
C
Initiation of a full septic workup including blood cultures and empiric broad-spectrum antibiotics
D
Administration of intravenous furosemide and elevation of the affected extremity above heart level
E
Postponement of operative intervention until informed consent can be obtained from his next-of-kin

Answer

Immediate four-compartment fasciotomy of the right lower leg

The correct answer is immediate four-compartment fasciotomy. This patient is presenting with acute compartment syndrome (ACS), most commonly seen following long bone fractures of the lower extremity, particularly the tibia. The diagnosis of ACS is primarily clinical. The most sensitive and earliest finding is pain out of proportion to the injury, which is not relieved by escalating doses of analgesics. This is accompanied by severe pain on passive stretch of the muscles in the affected compartment (e.g., passive plantar flexion stretching the anterior compartment). The sensory deficit in the first dorsal web space indicates ischemic injury to the deep peroneal nerve, which runs through the anterior compartment. Crucially, the presence of palpable distal pulses does NOT rule out ACS, as tissue perfusion ceases well before arterial pressure is overcome by compartmental pressure. Because the clinical diagnosis is unequivocal, the immediate next step is surgical decompression via a four-compartment fasciotomy. Delaying surgery for pressure measurements or imaging in a clinically obvious case risks irreversible neuromuscular necrosis, which can begin within 4 to 6 hours.

Step-by-Step Solution

Analyze the patient's history and risk factors.

The patient is 12 hours post-operative from intramedullary nailing of a comminuted tibial shaft fracture, placing him at exceptionally high risk for elevated intra-compartmental pressures.

Tibial fractures, especially those treated with intramedullary nailing, are the most common cause of acute compartment syndrome.

Interpret the specific physical exam findings.

The patient has pain out of proportion to the injury, severe pain on passive stretch (plantar flexion stretching the anterior compartment), and a specific sensory deficit (deep peroneal nerve distribution at the first dorsal web space). Pulses remain palpable.

These are the classic 'Ps' of compartment syndrome (Pain, Paresthesia). Pulselessness is an extremely late and unreliable finding.

Formulate the definitive diagnosis.

The diagnosis is clinically confirmed acute anterior compartment syndrome.

When classic clinical signs are clearly present, the diagnosis is made clinically without the absolute need for compartment pressure monitoring.

Determine the most appropriate next step in management.

Proceed immediately to the operating room for a four-compartment fasciotomy.

Time is tissue; irreversible muscle and nerve necrosis begins within 4 to 6 hours of ischemia. Delaying for imaging or attempting medical management will result in permanent limb dysfunction.

Key Concept

Diagnosis and acute management of compartment syndrome

Estimated Time:1m 30s

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