A PARAMEDIAN TANGENTIAL APPROACH TO LUMBOSACRAL EXTRAFORAMINAL DISC HERNIATIONS

OBJECTIVE: Extraforaminal disc herniations today are operated on via t he so-called lateral approach. Clinical experience has shown that in c ontrast to levels L2/3-L4/5, this approach may become extremely diffic ult at the L5-S1 level. According to new microanatomic studies, the pr evious lateral approaches at this level often do not allow access to t he neuroforamen without partial or total destruction of the L5-S1 face t joint. Postoperatively, this may lead to joint irritation with conse cutive low back and pseudoradicular pain. To preserve the facet joint, a new approach was developed based on an anatomic study. METHODS: The approach was first considered with the help of bone specimens includi ng ilium, vertebra 5, and sacrum. Thereafter, lumbar maceration specim ens were prepared leaving ligaments, intervertebral discs, and joints intact. From these specimens, bony and ligamentous landmarks were dedu ced. Finally, the approach was tested on seven cadavers. Subsequently, the approach was performed on 13 patients and the intraoperative find ings, the clinical feasibility, and the postoperative results were ana lyzed. APPROACH: After a transverse skin incision above the dorsal cur vature of the ilium, the paravertebral muscles are dissected from the ilium medially toward the spinous process. Lateral from the apophyseal joint, a canal is drilled through the spongiosa of the sacrum. Primar ily, a thin layer of inner cortex is spared to protect the content of the neuroforamen. Subsequently, it can easily be removed with the diss ector to enter the extraforaminal space. In the depth of the drilled c anal, the nerve root is found, because it is fixed at the sacrum near the disc space by the anterior lumbosacral ligaments. Riding on the ne rve root, the intertransverse ligament and muscle can be removed with the punch. It is then possible to see the neuroforamen and extraforami nal space in front of the joint, Free fragments and contained discs ca n then easily be found and removed. CONCLUSION: Using this new approac h, the L5-S1 joint remains intact. Space for instrumental manipulation s is created in areas not essential for joint function. For this proce dure, newly defined anatomic landmarks, such as the ileolumbar ligamen t, upper edge of the sacrum, lateral rim of the apophyseal joint, and para-articular notch, guide the operative route. In accordance with th e preliminary anatomic studies, this approach was successfully used in 13 patients, and we think that it is a promising alternative that hel ps to preserve joint function and dorsal root ganglion integrity.