The discectomy membrane (nerve root fibrovascular membrane): its anatomic description and its surgical importance.

The positive identification and protection of the nerve root is crucial prior to addressing the disc during lumbar discectomy. We report here our observation that there exists a membrane which lies immediately posterior to the annulus fibrosus at the level of the disc and connects to the dura of the nerve root at that level. This is a constant anatomic finding during the approach to the disc, and we refer to it as the "discectomy membrane". We found this tissue present at all lumbar levels of five fresh frozen cadaver spines. Its consistency varied from thin wisps of nearly transparent tissue to tissue strong enough to tether the nerve root laterally.