IMPROVED METHODS, TOOLS AND DEVICES FOR PERCUTANEOUS ACCESS IN MINIMALLY INVASIVE SPINAL SURGERIES

摘要

A cannula assembly for providing percutaneous access in minimally invasive spinal surgeries, includes an outer cannula, a nerve probe dilator and a multistage dilator system comprising a first dilator, a second dilator, a third dilator and a fourth dilator. The outer cannula and the dilators are slidable relative to each other and are arranged sequentially so that the fourth dilator surrounds the nerve probe dilator, the third dilator slides over a surface of the fourth dilator, the second dilator slides over a surface of the third dilator, the first dilator slides over a surface of the second dilator, and the outer cannula surrounds the first dilator.