Diagnosing Acute Compartment Syndrome

Are Current Textbooks Misleading?

Amir Oron, MD; Niv Netzer, MD; Philip Rosinsky, MD; Danielle Elmaliache; Peleg Ben-Galim, MD


Curr Orthop Pract. 2018;29(6):527-529. 

In This Article


This study is the first to demonstrate that in clinical practice the critical diagnosis of ACS may be missed due to the misconception in the diagnostic guidelines that are taught to medical students and memorized by attending physicians. Unfortunately most classic medical school textbooks do not mention ACS diagnosis at all. Medical textbooks that do mention ACS and the "5 P" signs as diagnostic indicators do not point out that signs such as pulselessness and paresthesia will typically occur at such a late stage when tissue damage is already irreversible. As demonstrated by the results of the questionnaire in this study, it is our natural tendency to favor easily recallable signs and mnemonics. Therefore, most physicians recite the "5 P"s signs and tend to remember pulselessness and paresthesias as signs for the diagnosis of ACS. The classic "5 P" signs are wrongfully associated with ACS because they are signs of acute major occlusion. Conceptually differing from acute major arterial occlusion, the hallmark of the pathophysiology of ACS that affects the microcirculation of the limb is small-vessel disease in which end arterioles and small capillaries, veins, and lymphatic vessels are compressed and jeopardized by the rising intracompartmental pressure. It evolves gradually when intercompartmental pressure (typically in the range of 30–50 mm/Hg) compresses and jeopardizes the microvasculature, causing end-target ischemia of muscles and soft tissues.[7] These pressure ranges are not enough to cause occlusion of major arteries. The pulse continues to be palpable in the ankle where normal systolic blood pressure is much higher (normal range 140–160 mm/Hg), and no loss of sensation or pallor is expected during the hours when diagnosing ACS is critical. To the contrary, pulse in the dorsalis pedis continues to be palpable for hours in ACS despite ongoing damage to the muscles and soft tissues in the affected limb.[5]

Clinically, the hallmark of initial muscle and fascia ischemia adjacent to the end arterioles is pain that is progressive and persistent. This pain is often termed "pain out of proportion to injury" as it is extreme and typically does not respond to regular pain medications. This pain is also accentuated by passive muscle-tendon stretching, which is a reliable clinical test for diagnosing ACS.[9] PPS can easily be performed by a resident, physician, or nurse by extending and flexing, for instance, the patient's toes in lower extremity ACS. Typically, this will not cause much pain to patients whose limbs have been put in casts after a fracture. In contrast, it can also stretch the ischemic fascial layers and cause severe pain in cases of ACS or in the initial stages of leg ischemia, experienced as "pain out of proportion," a clear-cut clinical indicator of ACS.

It is concerning that a critical diagnosis such as ACS in which the patients' limb and life are dependent upon early recognition and prompt surgical fasciotomy and decompression is not even mentioned in most classic medical school textbooks at all. The few medical textbooks that do mention ACS typically mention the classic five signs while pointing out that there are signs that appear earlier than others; however, since it is our natural tendency to favor easily recallable signs and mnemonics, most physicians recite the "5 P" signs and tend to wrongly remember pulselessness and paresthesias as part of the diagnosis.

Timely diagnosis of ACS is of utmost importance because the devastating late consequences are preventable. It is imperative that clinicians in multiple disciplines be made aware that diagnosis and treatment of ACS is not necessarily associated with the classic "5 P" signs and in particular that pulselessness is not a sign for which they should wait.