A technique for needle localization in paraspinal muscles with cadaveric confirmation

Invasive electromyography (EMG) of the paraspinal muscles is useful in clinical and research settings. No technique for localization of the needle in specific fascicles has been validated. Recent descriptions of the segmented innervation of the multifidus imply that such a technique would add greatly to the EMG determination of root level of a radiculopathy. We have developed a technique for localization which relies on palpation of bony structures and needle insertion at certain angles and depths. The technique was evaluated by injecting latex dye in 199 locations in 13 cadavers. Dissection demonstrated that the technique was accurate in 91 of 112 injections into specific fascicles of the multifidus (originating from different spinous processes), 39 of 43 injections into the longissimus, and 35 of 44 injections into the iliocostalis. Certain types of errors would not have occurred with the aid of EMG in vivo. When these are added to the correct injections, accuracy improves 97%, 93%, and 82%, respectively. The technique described here should be useful for kinesiological studies, biopsies and injections, as well as for the EMG confirmation of a radiculopathy.