Modern approach to an old technique: Narrative revision of techniques used to locate the epidural space

Since the first description of the epidural technique during the 1920s, the continuous progress of knowledge of the anatomy and physiology of the epidural space has allowed the development of different techniques to locate this space while increasing both the safety and efficacy of the procedure. The most common techniques used today are based on the two main characteristics of the epidural space: the difference in distensibility between the ligamentum flavum and the epidural space, and the existence of negative pressure within the epidural space. However, over recent years, technological advances have allowed the development of new techniques to locate the epidural space based on other physical properties of tissues. Some are still in the experimental phase, but others, like ultrasound-location have reached a clinical phase and are being used increasingly in daily practice.