Abstract

Intervertebral foramen is a door between the spinal cord and periphery. This canal is a unique structure with two different kinds of joints on its borders. Since it is not surrounded by only osseous structures, intervertebral foramen gains a dynamic structure. As a consequence, during movements of the body its shape and diameter has changed. Under normal conditions these changes could be overcame by the neurovascular structures passing through the canal.With a look from the spinal cord, i.e. medial viewpoint, intervertebral foramen is seen as circular, oval or upside-down teardrop shape. From the top to the bottom, postero-inferior edge of the body of upper vertebra, intervebral disc and postero-superior edge of the body of lower vertebra form the basement (anterior border) of the canal, respectively. In addition, lateral extension of posterior longitudinal ligament and anterior longitudinal venous sinus are also located on the anterior border. Free lateral edge of ligamentum flavum and the interarticular part of this bundle together with zygapophysial joint (facet joint) form the roof (posterior border) of the canal. Pedicles of upper and lower vertebrae form the superior and inferior borders, respectively. Spinal nerve canal is a canal beginning from the lateral side of the dural sac and continues with intervertebral foramen. The medial border of this canal is formed by dural sac and the lateral border is formed by fascial sheet on the medial of psoas. Branches of spinal nerve and segmental vascular structures pass through the passages within the bundles of this fascial sheet.There is a pad formed of epidural fatty tissue around the nerve roots in intervertebral foramen. Lumbar nerve roots course close to the groove on the medial side of pedicle, just before entering the intervertebral foramen. This groove more significantly exists on the fifth lumbar vertebra and spinal canal enlarges laterally to this hole. These enlargements, which make the spinal cord seems like a three-leaved clover, are called as “lateral recess”. The narrowness in this area was described as lateral recess stenosis and it was stated that there could be a radicular type pain in the legs of the patients. Spinal nerve leaves the dural sac with a more oblique angle at the lumbar region with respect to the other regions. Because of this oblique pattern, spinal nerve extends from infero-medial side of upper pedicle through supero-lateral side of lower pedicle. The inappropriate infero-medial deviations during transpedicular approaches may cause complications for both spinal nerve and spinal cord.