Evolution of endoscopic transforaminal lumbar approach for degenerative lumbar disease.

Endoscopic spine surgery has evolved dramatically in last 30 years; with the development of new improved endoscopic optics and instrumentation limitation of endoscopic spine surgery has significantly reduced. The transforaminal approach has been limited in its indications due to its optimized approach and obstacles of bony or neural structures. As the initial transforaminal approach is based on the inside out technique, there were many limitations on the indications. Outside-in approach has been developed to address these limitations. However, the outside-in approach was not free from anatomical obstacles. The mobile outside-in approach technique has advantage of both inside-out and outside-in technique. It is equally safe as inside-out technique and provides an easy handling of structures, while it is equally versatile as outside-in technique in managing different types of disc prolapse such as central, paracentral, foraminal, far lateral, and up and down migration, and in high-canal compromise cases. The mobile outside in technique, however, demands a longer learning curve and beginners need to be patient while learning the technique.