A new classification of lumbar motion segments for microdiscotomy.

Planning and performing lumbar microdiscotomy--with or without a microscope--requires a three-dimensional understanding of the spinal canal and its surrounding structures. A new disc-related classification is helpful. Lumbar motion segments are divided into disc, infradiscal and supradiscal levels in the craniocaudal plane and into medial, paramedial and lateral zones in the horizontal plane. Traversing roots, with or without a nerve root sheath, and exiting roots have specific locations to the levels and zones. A comparative study of conservatively and surgically treated patients showed that not only the size of the disc herniation but also the direction of migration of the extruded disc material has a bearing on the form of treatment that is indicated.