# Laser Reconstruction of Spinal Discs Experiments and Clinic
### Lasers in Spine Surgery  
Many studies on the use of lasers in orthopedics refers to ablative destructive surgery of the spine. For the first time, percutaneous laser discectomy (PLD) was performed in 1987 using a Nd: YAG laser [26]. With the development of the PLD technique, its clinical success increased to 80% or more [27]. It was found that in the tissues surrounding the ablation zone significant damage is possible due to heating. This can cause complications, often including an infectious lesion of the operated IVD--discitis in the zone of tissue necrosis after laser evaporation of the central part of the NP. There is aseptic discitis, root damage, thermal damage to the EPs of adjacent vertebrae. One year after PLD, necrotic tissues are found in the disc. A decrease in the likelihood of side effects has been achieved through selective ablation of the NP and by reducing the radiation power. Transforminal epiduroscopic laser ablation (TELA) selectively removed the herniated portion of IVD and induced more effective decompression with minimal complications [28]. TELA enhances the resorption of the herniated IVD by drilling a hole in the AF and partially removing the slipped NP with the use of a 1414 nm Nd:YAG laser. Although the clinical success rate was 76.6% at 12 months, it is unclear whether a better outcome can be achieved with direct AF ablation. In [29], a technique for laser irradiation of an IVD with a moderate power--thermodisco plasty (TDP)--is presented, which is based on the effect of collagen compression when heated above 70 \({}^{\circ}\)C. TDP leads to tissue compaction and reduction in its volume without carbonization or significant destruction. The TDP method is used during endoscopic removal of a hernia or disc protrusion, when using an endoscope, it is possible to accurately bring the laser probe into the area of the pain generator, including after mechanical removal of the restrained fragments of the NP. At the same time, in the zone of laser exposure, there was histologically a thickening and homogenization of CFs as well as destruction of most of the cells. Laser radiation made it possible to vaporize the NP of the disc, while simultaneously producing its de-reception. The success rate was 95.2%, and in many cases, the postoperative control MRI showed a decrease in protrusion size. Even though the total energy of laser action on the IVD was significantly lower (2-3 times) than with the accepted puncture laser discectomy, this action nevertheless caused extensive tissue coagulation and, consequently, the destruction of cellular elements. This, unfortunately, significantly worsened the dynamics of reparative processes in the IVD. A fundamentally new approach to the treatment of DDD is based on laser-induced modification of the IVD tissues [30]. Moderate heating and control of thermomechanical stresses in tissues subjected to short-term non-destructive pulse repetitive laser irradiation make it possible to form new cartilaginous tissue of the fibrous-hyaline and hyaline types in the IVD [31]. Activation of reparative regeneration was observed as early as on the 7 th day, and replacement of AF and NP defects with new cartilaginous tissue occurred 2-3 months after laser exposure. The developed technology of laser reconstruction of discs (LRD) makes it possible to treat IVD by replacing disc disrupture and disc fissures with regenerating cartilaginous tissue [32; 33]. This contributes to the reverse development of the degenerative-dystrobic process with stabilization of the dorsal segment due to the replacement of altered IVD tissues with regenerating hyaline and fibro hyaline cartilage [30; 31; 32; 33]. In addition, the formation of a new dense cartilage limits the migration of NP fragments, preventing the recurrence of disc herniation [34]. This is due to the transformation of the NP into hyaline cartilage, which tightly grows together with neighboring tissues and without clear boundaries passes into AF and hyaline EP.