1	Endoscopic Surgical Anatomy and Patho-Anatomy of Lumbar Neuro-foramen John C. Chiu, M.D., FRCS (US), D.Sc. Chief, Neurospine Surgery California Spine Institute Thousand Oaks, California, USA President, ISMISS/SICOT
2	Introduction: MISS is to avoid morbidity associated with open lumbar spinal surgery MISS can be performed in IV conscious state Posterior lateral transforaminal technique can visualize and treat extra foraminal, foraminal, and lateral recess pathology, causing back and radicular pain A steep learning curve is required to interpret endoscopic findings of foraminal surgical anatomy and to avoid trauma to the dorsal root ganglion (causing severe intraticable burning pain and dysesthesia)
3	Neuro-foraminal Surgical Anatomy: It is a tubular 3D structure Four zones: lateral recess (osteum internum), the pedicle zone (mid- zone), exit zone (osteum externum) and far lateral zone Internal zone of the foramen: the superior notch, inferior notch and sub-articular zone (bonded by disc and facet joint) Success or failure for endoscopic surgical procedure depends on the dynamics on the foraminal size, shape and contents7
4	Neuro-foraminal Surgical Anatomy: The pedicles, facet joints, intravertebral disc, and the vertebra These border the foramen which is endoscopically divided into three zones: Superior notch (from the junction of proximal tip of superior facet to the posterior margin of vertebral body of superior vertebra) Sub-articular zone (ventral to the facet joint and disc) Inferior notch (caudal to an imaginary line projecting posteriorly from the superior margin of the inferior vertebral body to the ascending articular process
5	Neuro-foraminal Surgical Anatomy: Intervertebral disc with degenerative changes and reduction in height and secondary disc bulge or protrusion Spinal ligaments Ligamentum flavum Joint capsule Posterior longitunal ligamen Pathophysiology of hypertrophic ligaments
6	Neuro-foraminal Surgical Anatomy: Intraspinal neuro structures – lig attachments: Midline ligament (Hofmann) Lateral ligament (Hofmann) Lateral root ligament Neural attachments The lateral root ligament Foraminal complex Transforaminal ligaments (superior, intermedial, inferior types) and the corporotransverse ligaments (seldom recognized endoscopically) Patho genesis of hypertrophic ligaments with secondary structural compression
7	Neuro-foraminal Surgical Anatomy: Anterior intervertebral venous plexus (AIVVP) which receive basi vertebral veins, avoiding the disc and also runs in the lateral gutter of the spinal canal Posterior internal vertebral venous plexus (PIVVP) in the epidural space posteriorly and traversing adjacent segments, reaching out through the foramen into external venous plexus and lateral longitudinal intravertebral venous plexus The segmental artery supplies anterior longitudinal arterial system of the epidural space anterior to PLL Connected to posterior longitudinal arterial system
8	Neuro-foraminal Surgical Anatomy: Three types of arterial supply to the spinal nerves: Radiculomedullary a. Radicular arteries T-shape branches of articular artery
9	Neuro-foraminal Surgical Anatomy: Segmental nerve supply to the spine – ascending facet branch, ascending sinu vertebral (SV), SV branch of facet, descending facet branch, branch to disc, gray ramus, and branches to all, and posterior primary ramus Autonomic nervous system – sympathetic chain, related to sympathetic back pain Lumbar dura – by sympathetic system
10	Neuro-foraminal Surgical Anatomy: Dorsal root ganglion in the superior notch – substance P. L4 and L5 DRG locates intra foraminally, while L1 to L3 , and S1 DRG intraspinally Spinal content Several membranes have been identified Internal vertebral nerve supplies Recurrent meningeal nerve Communicating filaments Sacral Iliac Joints Nerve supplies from L4-S3 inclusive
11	Neuro-foraminal Surgical Anatomy: Degenerative spondylolisthesis may compromise the foramen causing compression of exit nerve root Bony overgrowth may occur: Diffuse idiopathic skeletal hyperostosis (Dish) Paget's disease Ankylosing spondylosis Acromegaly Hyperparathyroidism Fluorosis
12	Neuro-foraminal Surgical Anatomy: Foraminal and lateral recess stenosis may result from foraminal narrowing caused by: Disc herniation Dish Synovial cyst or tumor Spondylolisthesis Subarticular lateral recess stenosis due to facet hypotrophy, Dish, and Paget’s disease
13	Neuro-foraminal Surgical Anatomy: From any bony margins of spinal foramen and spinal canal Endoscopically the lesions and deviation of exiting nerve are visualized Shoulder osteophytes often displace the nerve medially or laterally and the nerve is often found adherent to them Facet and lamina hypertrophy causing spinal stenosis Transforaminal ligament of Hofmann may cause pain Calcified ligaments causing compression of the nerve during spinal movements Superior foraminal ligament, can be classified requiring decompression for foraminoplasty
14	Neuro-foraminal Surgical Anatomy: Spondylolisthesis – anterior or retro Neural anomalies: Conjoined nerve in 14% Claudication: Secondary to spinal stenosis
15	Neuro-foraminal Surgical Anatomy:
16	Neuro-foraminal Surgical Anatomy:
17	Conclusion: The success of endoscopic MISS depends on careful analysis of all factors causing pain Causation (inter related factors) of pain and sciatica are: Mechanical and physical factors Tissue changes – neo-vascularisation and neo-neuralisation Biochemical factors: cytokines, pain mediators, alteration in PH, ionic changes etc… Endoscopic MISS surgeon needs to consider the effect of alteration of the foraminal anatomy with its contents and patho anatomical changes of the tissue around the foramen
18	Hope you enjoyed this presentation!