Extraforaminal lumbar herniation: "far lateral" microinvasive approach retrospective study

The first anatomic description of extraforaminal herniation found in the literature was published in 1944. This was followed by several definitions regarding the anatomic site of this pathology. We consider correct the definition of lumbar extraforaminal herniation concerning the anatomic site of the herniated fragment. This fragment compresses the nervous root after its exit from the foramen, thus causing the compression of the spinal ganglion against the strong intertransverse ligament. The incidence of the pathology shifts from 1% to 12% and in our study was 4.2%. Over these years, the surgical approach has changed mainly because of two requirements: good exposition both of the foramen and of the herniation and the necessity of preserving stability of the spinal column as much as possible. In the last 30 years, less invasive approaches, paramedian, para- and transmuscular, lateral, and tangential, have been preferred to an interlaminar medial approach with a subtotal and/or complete facetectomy. In the last 4 years, 46 patients presenting with pure extraforaminal herniation have been treated in our institute through a far lateral microsurgical approach, avoiding resection of bone and reducing to the minimum the muscular retraction and the closure of blood vessels. We advocate a far lateral microsurgical approach, with no resection of bone and with highest respect for the osseous articular and muscular structures.