Extraforaminal lumbar disc herniations: microsurgical anatomy and surgical approach

Abstract

INCE Mixter and Barr 21 first described herniated lumbar intervertebral disc-induced nerve root compression, numerous operative approaches have been used for treatment. Neural compromise caused by a herniated disc outside the confines of the spinal canal is more readily recognized by using computerized tomography and magnetic resonance imaging. Such herniations have been characterized as foraminal, 8 extraforaminal, 15 extreme-lateral, 1,23 far-lateral, 19 and extracanalicular 25 disc prolapse. We prefer the term "extraforaminal" because the boundaries of the neural foramen can be readily identified on computerized tomography and magnetic resonance images, and because extraforaminal lesions are distinct from intraspinal-foraminal, foraminal, and foraminal-extraforaminal lesions.The clinical and radiological characteristics of extraforaminal lesions have been reported. 1,8,10,14,23 Currently two surgical approaches commonly used for the treatment of this type of disc herniation are 1) a conventional approach via a midline laminotomy/fenestration, or one of its modifications, and 2) a paramedian approach. Removal of a truly extraforaminal herniated disc via the midline approach necessitates sacrificing a significant portion, if not all, of the facet joint. The paramedian approach, however, which is performed at the level of the facet joint, provides a more direct route to this lesion. Although several Materials and Methods Anatomical StudiesTwenty-four lumbar extraforaminal disc spaces were studied in three human cadavers. In one cadaver predissection, the arteries and Object. Familiarity with the microsurgical anatomy of the far-lateral compartment is essential for operating in patients with far-lateral discs. In this report the authors address the microsurgical anatomy studied in 24 extraforaminal lumbar disc spaces in three cadavers.Methods. Cadaveric dissections confirmed the authors' operative experience in which they found an arterial arcade to be associated with the nerve trunk. The main trunk of the lumbar artery was located lateral to the exiting nerve root in the region of intervertebral foramen. The trunk of the lumbar spinal nerve descending from the level above was 7 mm (Ϯ 3 mm [standard deviation]) lateral to the lumbar artery.Conclusions. Clarification of the microsurgical anatomy of the far-lateral compartment confirmed the authors' clinical impression that the optimum approach to far-lateral discs is via the inferomedial quadrant of the extraforaminal compartment. In this quadrant, exposure of the main nerve root can be facilitated by dividing the posterior primary ramus and a newly described arterial arcade that envelops the nerve trunk. Once this arcade is divided, the nerve can be retracted with relative ease and safety, and the disc can be removed more easily. KEY WORDS • spine • lumbar intervertebral disc • microsurgery • anatomical study • surgical approachS

The relation between the lumbar vertebrae and the spinal nerves for far lateral lumbar spinal approaches

“…1,[8][9][10] The surgical treatment of these herniations requires the use of the far lateral paravertebral approaches. Such approaches dictate accurate knowledge of the anatomy of the lumbar nerve roots and their relation with the bony landmarks in the extraforaminal area.…”

“…According to Viswanathan et al 1 inter-transverse muscle spanning the adjacent transverse processes was generally thin and easily removed using pituitary rongeurs; the distal branches of the nerve and arteries were preserved. The exposed inter-transverse ligament was a smooth shiny sheet of tissue.…”

Risk Factor for Unsatisfactory Outcome After Lumbar Foraminal and Far Lateral Microdecompression

“…1,4 -6 A microdecompression technique through the lateral approach, which was introduced by Reulen et al 6 in 1987 and Wiltse and Spencer 7 in 1988, and modified later by many surgeons, 8 -18 permits the direct access to far lateral lesions, minimizing violation of the facet joint and postoperative back pain, although the anatomy related to this approach is not familiar to spine surgeons. 13 The reported success rate following microdecompression of foraminal and far lateral lesions reaches 68% to 80%, 3,4,10 -12,15-17 but many patients have postoperative leg pain, which is the main cause of unfavorable outcomes. 4,10,11,15,17 Manipulation of the dorsal root ganglion is thought to cause transient dysesthesia, 10,11 but there have been no detailed analysis on postoperative persistent or recurrent radicular pain.…”

Three-Years Outcome of Microdiscectomy via Paramedian Approach for Lumbar Foraminal or Extraforaminal Disc Herniations in Elderly Patients over 65 Years Old

“…Various surgical procedures can be used to treat these lesions, from microdiscectomy via various approaches to fusion with or without total facetectomy4). The microdiscectomy via paramedian approach technique permits direct access and minimizes violation of the facet joint36).…”