Morphometric analysis of the YESS and TESSYS techniques of percutaneous transforaminal endoscopic lumbar discectomy.

Posterior lateral endoscopic nucleotomy is widely accepted as a minimally invasive surgery for lumbar disc herniation, but few studies have compared the transforaminal approach using two different techniques, YESS and TESSYS. One hundred and fifty lumbar IVFs of cadaveric spines were studied. Eighteen-gauge needles were inserted percutaneously toward IVFs into the discs by either YESS or TESSYS. The distances from the needle to the nerve root and from the needle to the spinal dura were measured and compared across different spinal segments. The incidence of nerve roots compression by the operating endoscope was measured. The mean distances from needle to the nerve root and spinal dura in YESS were 3.5 ± 1.4 mm and 6.6 ± 1.9 mm. The respective mean distances in TESSYS were 4.6 ± 1.5 mm and 5.9 ± 1.4 mm. The distance from needle to the nerve root was longer in TESSYS, while the distance from the needle to spinal dura was longer in YESS. The distance from needle to nerve was shorter in proximal segments. The incidence of operating endoscope compression of the nerve root was high in both of techniques. The difference in theory and design between YESS and TESSYS, "intradisc" versus "intracanal", was confirmed by comparison of anatomic distances from the needle to the nerve. Puncture of the annulus in the distal lumbar is safer than proximal puncture. The high incidence of endoscope compression of the nerve root may be related with the transient postoperative dysaesthesia.