Approach

The diagnosis of acute compartment syndrome (ACS) remains a controversial area. Historically, it was regarded as a clinical diagnosis, with compartment pressure measurement reserved for cases in which the diagnosis remained unclear after clinical examination.[8] However, several studies have cast doubt on the reliability of diagnosing ACS on clinical signs alone.[8]​ To recognise extremity compartment syndrome in a timely fashion, it is important to maintain a high index of suspicion and serially examine patients at risk to document changes over time. 

Pain out of proportion to the injury or clinical situation is often reported as being the earliest sign of developing ACS.[8] Pain that does not improve with adequate analgesia may also indicate a diagnosis of ACS.[17] The classic clinical diagnosis is based on the following six Ps: pain, pressure, pulselessness, paralysis, paraesthesia, and pallor (uncommon).[21] However, the loss of a pulse, paralysis, pallor, and decreased temperature are more often signs of arterial ischaemia than acute extremity compartment syndrome.[8] If the examination is equivocal or diagnosis is unclear, then there is a role for pressure measurement. Diagnosis in patients with altered mental status and children may be occasionally challenging due to the inability to document physical findings accurately.

Historical factors

Patients with ACS may present with severe extremity pain and tightness after trauma. Pain out of proportion to the injury that is aggravated by passive stretching of the muscle groups contained in the involved compartment is one of the earliest and most sensitive clinical features.[8][17]​​[18]​​​​​ Pain that does not improve with adequate analgesia may also indicate a diagnosis of compartment syndrome.[17]​ The absence of pain can be secondary to altered mental status or a central-peripheral neural deficit but can also be a late finding of compartment syndrome. Paraesthesia is an early indicator of hypoxia to nerve tissue within a compartment.[17][18]​​

The types of traumatic injury with high risk of causing compartment syndrome include extremity fracture, soft-tissue trauma (with or without fracture), reperfusion injury, thermal injury, and/or penetrating trauma.[18] History of bleeding disorder, compression support, venous obstruction, extravasation of intravenous infusion, and aggressive fluid resuscitation can also predispose to ACS. Sports-related ACS is less common. Exercise-induced rhabdomyolysis may progress to compartment syndrome.[13][14][15]

Patients with chronic exertional compartment syndrome may present with symptoms including exercise-induced pain that usually resolves after rest and ceasing exercise. This is most frequently encountered among long-distance runners and other sports with intense muscular activity.

Physical examination

Early diagnosis is essential and should be driven by a high index of suspicion based on the clinical history.[6]​ However, the sensitivity of physical signs is suboptimal, as they can be missed or attributed to other aspects of injury.[6]

Presence of tightness in the compartment is the earliest objective finding of ACS. However, manual palpation to detect compartment firmness - a direct manifestation of increased intracompartmental pressure - shows low sensitivity.[22]​ Pain is commonly elicited with passive stretching of the muscles in the involved compartment. The loss of a pulse, paralysis, pallor, and decreased temperature are more often signs of arterial ischaemia than acute extremity compartment syndrome. If they occur in compartment syndrome, they are late signs, indicating significant disruption to the vascularity and viability of the affected limb.[8][17]​​ Paralysis is caused by prolonged nerve compression and ischaemia, or irreversible muscle damage.[18] Paralysis is a late sign of compartment syndrome.[8]

Limited evidence supports using serial clinical examination findings to assist in ruling in ACS.[6]

Compartment pressure measurement

Early diagnosis is essential and should be driven by a high index of suspicion based on the clinical history.[6]​ Compartment pressure measurement is indicated whenever the clinical examination is equivocal or the diagnosis is uncertain in a patient at risk.[8]​

Intracompartmental pressure monitoring may assist in diagnosing ACS but supporting studies show variability in the thresholds for fasciotomy, timing, and method of pressure monitoring.[6]​ Single pressure values alone are not reliable for diagnosing compartment syndrome and may result in the diagnosis being missed.[6]​ Relying on pressure-based thresholds alone (without consideration of clinical suspicion and clinical examination findings) for diagnosing acute extremity compartment syndrome may result in overtreatment with fasciotomy.[6][23]​ In one study of 64 patients, using a compartment pressure value of 30 mmHg as a threshold for fasciotomy led to a rate of fasciotomy of 29% after tibial surgery.[8][24]​​ It is often helpful to obtain a baseline intracompartmental pressure in compartments that may be at risk, especially in a patient who cannot be examined in regular time intervals. Without a dependable clinical examination (e.g., in the obtunded patient), repeated or continuous intracompartmental pressure measurements may be useful until ACS is diagnosed or ruled out.[6]​​ All muscular compartments should be measured, not only the compartment thought to be at highest risk.[7]​ Below the knee, all four compartments should be checked, even though the anterior compartment has the highest risk of compartment syndrome.[7]​ Compartment pressure monitoring does not appear to provide useful information to guide decision making when considering fasciotomy in adults with evidence of irreversible intracompartmental (neuromuscular/vascular) damage.[6]

Several pressure measurement devices are available for determining intracompartmental pressure: for example, traditional needle manometry, arterial line transducer systems with side-port needles, slit catheters, and self-contained measuring systems.[8]​ For patients with suspected chronic exertional compartment syndrome, pressure should be measured after an episode of exertion. If specialised equipment is unavailable, a 16-gauge intravenous cannula connected to an arterial blood pressure (BP) transducer and monitor via saline-filled arterial line tubing can be used to measure compartment pressures.[25]​ An 18-gauge needle may overestimate compartment pressure by up to 18 mmHg when compared with a slit catheter or side-ported needle.[8][26]

The differential pressure (i.e., the difference between diastolic BP and measured compartment pressure: diastolic BP minus compartment pressure) may also be measured.[27]​ A threshold of diastolic BP minus intracompartmental pressure >30 mmHg (delta pressure) may assist in ruling out ACS.[6][27][28]​ Differential pressure within 20-30 mmHg of the diastolic pressure (delta pressure) is considered a strong indicator for fasciotomy.[18] However, care should be taken when using this criterion for patients who are receiving vasodilatory medications whose diastolic BP is low.

Laboratory testing

Limited evidence supports the use of myoglobinuria and serum troponin in diagnosing ACS in patients with traumatic lower extremity injury.[6]​ Muscle cell lysis and muscle necrosis may cause these to be elevated.[18]​ In patients with acute vascular ischaemia caused by femoral artery embolism, femoral vein lactate concentration sampled during surgical embolectomy may assist in the diagnosis of ACS.[6][29]​ In the absence of reliable evidence, serum biomarkers do not provide useful information to guide decision making when considering fasciotomy for a presumed late presentation or missed ACS.[6]

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