Holmium : YAG and Neodymium : YAG lasers used in orthopaedic surgery - a critical consideration of indications in an in vitro study

This is an in vitro study of the biophysical effects of holmium:YAG and neo dymium-YAG lasers that was prompted by the poor clinical results obtained w ith lumbar percutaneous laser discus decompression (PLDD). In the absence of adequate cooling, ablation of tissue with the holmium:YAG laser causes thermal damage to the surrounding tissues. Utilizing the imme diate colour-independent laser coupling effect, the holmium:YAG laser remov es soft and hard tissue immediately. The low tissue penetrating power (max. 0.32 mm), together with the use of irrigation, avoids thermal problems, an d this laser type with its high pulse energy and frequency is to be recomme nded for arthroscopic surgery. In contrast, the effects of the neodymium:YA G laser are highly dependent on tissue colour. Using this laser on light-co loured tissue only diffuse warming but no ablation of soft tissue was often seen. The depth of tissue penetration seen in our study was 0.58 mm, but i s greatly dependent on the duration of application, and is much larger with long application times. In conclusion, we believe that the neodymium:YAG laser is more suitable for percutaneous intradiscal procedures than the holmium:YAG laser. For arthro scopic surgery, the holmium:YAG laser will be the better choice. The effect of each type of laser depends not only on its physical properties, but als o on tissue properties (light or dark-coloured, thermal conductivity) and d uration of application.