Vascular structures of epidural and neural tissue play an important role in the patho-physiology of pain that is commonly observed in individuals with symptomatic disc herniation, spinal stenosis, and failed back surgery syndrome. It has been shown that
interference with the normal blood flow of delicate neural and epidural venous systems (Fig. 10) may cause venous stasis edema of the nerve root, neural fibrosis, and chronic pain (4,8). This phenomenon is usually observed in patients presenting with symptomatic disc herniation and spinal stenosis. Segmental arteries, branches from the aorta and the internal iliac artery, provide blood supply to the neural, osseous, and muscular structures of the spinal column. Branches from the lumbar arteries depart from the segmental arteries and enter the intervertebral foramen (radicular artery) with the exiting root to supply the medullary arteries of the spinal cord and the nerve roots.
Segmental arteries distal to L4 originate from the hypogastric arteries that are branches of the internal iliac arteries (10) (Fig. 11). When the posterolateral approach is used for either discectomy or anterior column stabilization and the instruments are directed and properly positioned in the triangular working zone, these segmental arteries are not sub-
ject to insult and injury. However, when the instruments are inserted too far anteriorly (vertically), they may penetrate the iliac artery or vein, causing rapid blood loss requiring immediate emergency exploration and repair of the injured vessels. By contrast, during laparoscopic or open retroperitoneal or transabdominal spinal surgery, the hypogastric and infraaortic arteries as well as sympathetic ganglia are in the path of the inserted instruments and must be protected.
When the instruments are properly lodged in the triangular working zone, the radicular arteries remain protected under the pedicular notch. However, during decompression
of the lateral recess in the treatment of lateral recess stenosis, particularly when a backfiring laser light is being used, great care must be exercised to protect the vascular structures and their accompanying exiting root in the pedicular notch. Only a small portion of the exiting root that is situated between the lateral pedicular line and the superior border of the transverse process is subject to insult during the posterolateral approach for the removal of extraforaminal herniations (7). However, positioning the instruments medial to the lateral pedicular line at the onset of operative procedures will help avoid any complications (see Chapter 4).
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