[Angle of needle position for the epidural-perineural injection at the lumbar spine]

The aim of this study was to find the correct angle of the needle position for the epidural perineural injection at the lumbar spine without any help by imaging.

In 11 human cadaver lumbar spines besides dura, nerve roots and bones all soft tissue had been removed to allow us to look into the anterior lateral epidural spaces between L3 and S1 in different angles with an operation microscope. The area between the dura (medial), facet joint (lateral) and the laminae (cranial and caudal) were photographed and planimetrically measured. This area is called the width of the injection canal.

Degenerative lumbar spines show a width of the injection canal of 29.61 mm(2) in L5/S1 with an angle of the needle position of 15 degrees to the midline. The optimal angle position of the needle brought a width of the injection canal in L4/5 only for 7.3 mm(2) and in L3/4 for 3.5 mm(2). In non-degenerative spines the injections canals were much wider.

The epidural-perineural injection into the anterolateral epidural space only makes sense in the segment L5/S1. Here the L5 nerve root is reached as well as the S1 root - the main causes of sciatica. In upper segments the injection canal is far smaller even at optimal injection angles. In case of nerve root compression at L4 and upwards other epidural injection techniques should be used such as the epidural dorsal loss of resistance technique or the transforaminal technique.

With some training it is possible to perform epidural-perineural injection for sciatica without the help of imaging.