The effect of irrigation on peak temperatures in nerve root, dura, and intervertebral disc during laser-assisted foraminoplasty

Background and Objective: The Holmium: YAG (Ho: YAG) laser has been used fo r the ablation of prolapsed discs but alternative techniques are available, and this application remains controversial. It also has potential for the decompression of nerve roots within narrowed foraminae with the technique o f endoscopic laser foraminoplasty. Traditional methods of decompression nec essitate a major surgical procedure with potential destabilisation of the l umbar spinal segment. Nevertheless, minimally invasive techniques are attra ctive only if serious complications can be avoided. This study reports the peak temperatures reached in surrounding tissues with and without saline ir rigation. Study Design/Materials and Methods: Investigation of the hypothesis was car ried out in excised sheep lumbar spines. T-type thermocouples were used for the measurement of tissue temperatures during laser ablation of nerve root foraminae. The temperature was assessed in the nerve root, dura mater, and disc space. Results: The Ho: YAG laser was effective in widening the foraminae by appro ximately 1.5 man with a total energy of 4.60 kJ. This was statistically sig nificant in both vertical and horizontal directions (P < 0.0003 and P < 0.0 0005, respectively). The mean temperature of the nerve root, dura, and disc space during the procedure was 44 +/- 3.1 degreesC, 42.8 +/- 4.7 degreesC, and 41 +/- 3.4 degreesC respectively. There were transient high peaks seen in the temperature profiles. Using saline irrigation at 27 ml/minutes thes e temperatures were reduced to 34.1 +/- 1.8 degreesC (P = 0.0002), 34.9 +/- 1.5 degreesC (P = 0.002), and 37.2 +/- 1.2 degreesC (P < 0.014), for nerve roots, dura, and disc space respectively. Conclusions: Laser ablation of bone and ligament for nerve root decompressi on using the Ho: YAG laser may offer substantial advantages, but the risk o f serious complication may only be avoided if the technique is combined wit h saline irrigation. (C) 2001 Wiley-Liss, Inc.