Degenerative Disc Disease; The word Laser is an abbreviation consisting of the initials of the word (Light Amplification by Stimulated Emission of Radiation). It is in our language with the word LASER. According to this angle, which briefly summarizes the generation of energy, laser; It is the light that emerges when the liquid crystal located between two mirrors with full and semi-reflections is exposed to concentrated energy (amplification). The laser type is named after the substance in the liquid crystal.
Degenerative Disc Disease
Laser energy application in the musculoskeletal system was first made by Whipple in 1984 with the use of CO2 laser. The classification of the laser according to its optical parameters (wavelength, power and dose) has been questioned in clinical studies after this date. Laser is known to alter cell proliferation, motility and secretion at different doses. Tissue interaction, on the other hand, may be dose-dependent, in the form of breaking up, liquefying, heating and evaporating. Although the type of laser used in the musculoskeletal system is often the ion resonance type, it can be classified as follows:
UV Laser (Excimer)
Visible Laser (Argon)
IR Laser (Ion Resonance)
n CO2
n YAG: (Yttrium-Aluminum Garnet)
l Neodymium (Figure-2)
l KTP Doubled Neodymium (Potassium-titanyl-Phosphate)
l Holmium
l Erbium
Argon laser is well absorbed by hemoglobin and acts by releasing heat in the tissue. This effect results in apoptosis by activating oxygen in the cell nucleus. This is the basis of photodynamic therapy. Excimer breaks the bonds of molecules without generating heat, which is why it is called cold laser. High power is obtained at low frequencies with CO2, it is absorbed by water. It achieves its superficial effect without penetration. Nd YAG penetration and coagulation effect is high.
Laser energy effect is examined in three stages:
Photo-thermal: coagulation, necrosis and evaporation
Photo-chemical (Argon, Excimer): It is the change in the bond structures as a result of the absorption of energy at the molecular level. It provides an advantage in the treatment of metabolically active tissues (such as tumors).
The photo-mechanical effect is the combination of short wave and low frequencies and the borderline ultraviolet-infrared effect. While the tissue reacts with fast ionization, the "acoustic shock wave" effect occurs. Even cutting-cutting power on bone is provided with this feature.ır.
Radiofrequency energy is short wave sound energy. As in light energy, a physical state change occurs in proportion to the tendency of the substance to become unstable, on which the concentrated short wavelength energy is focused. This change, explained by the conversion to heat energy, is the basis of the cooking feature in microwave ovens.
The thermal effect of radiofrequency energy is frictional. There are two separate effects: ohmic and dielectric. Ohmic effect develops at frequencies below 500 mHz. If the dielectric effect is above 500 mHz, microwave destructive effect occurs. In the musculoskeletal system, the 1-300 mHz ohmic effect of radiofrequency energy is utilized.
With radiofrequency (RF) energy, tissue can be freed from its covalent bonds (relaxation-cutting), completely evaporated or new bonds (wrinkle-pull) can be formed. The ohmic effect achieved by increasing and decreasing the frequency in medical applications allows the clinician to intervene with less complex choices than laser. However, its disintegrating effect is limited in soft tissues.
Knowing which energy will be used, how often and how to use it in the musculoskeletal system is possible by knowing the chemical and physical results of these energies in tissues. Penetration is the leading limiting factor in both energies. Preferring Holmium YAG in laser applications in orthopedic surgery is one of the mechanical advantages it provides despite its low penetration effect.
Degenerative Disc Disease
Although thermal penetration and related necrosis effect decreases with the use of Holmium YAG laser, it can be used with other advantages of energy. In addition to the acoustic shock effect, thermal coagulation, evaporation, wrinkling and bleeding control are achieved by extremely reduced tissue penetration. Its effect is indispensable, especially in minimally invasive endoscopic surgery applications, arthroscopy, tenoscopy and foraminoscopy in areas that cannot be reached with mechanical devices.
Thermal therapy, which has been used since Hippocrates, has been revived with laser and radiofrequency applications. The thermal effect is protein denaturation at 40-70 degrees, coagulation at 70-85 degrees, vacuolization at 85-100, evaporation at 100 degrees, carbonization at 400 degrees. Living tissue begins to die at 45 degrees and 45 degrees is the temperature at which the RF effect has just begun. In order for the radiofrequency thermal effect to end with irreversible tissue contraction, energy must be transferred to create 60-75 degrees of heat. This effect occurs 30% in 5 minutes at 60 degrees, 36% at 62 degrees, and more than 50% after 65 degrees. With the thermal effect, the helix structure turns into a gel form with protein denaturation and reduces its volume, the tissue shortens and gives a morphological response. This effect is called "ablation" for short.
The functional results of the thermal effect on regenerative tissues are close to perfect. While the capsule contributes to the healing process in ligament and tendinous structures, functional expectations during remodeling occur in the area limited by RF. However, cellular necrosis caused by thermal effect in structures such as cartilage and intervertebral disc is irreversible. For this reason, mechanisms that try to create the energy transfer created at high temperatures with monopolar electrocautery tips that provide coagulation and ablation effect together, with bipolar radiofrequency tips at low temperatures have been developed. For example, the ablative effect occurs with a spark, depending on the probe shape. Spatter-free energy transferred at monopolar tip shape or bipolar tips enables nonablative RF energy application. Bipolar effect providing coagulation and plasma forming ablative effect (nonablative) is coagulation + ablation = coblation. The difference of coblation effect from multipolar radiofrequency is that it provides plasma conversion at low temperature. In this way, it can be called cold ablation. Therefore, there are two different applications of radiofrequency:
Monopolar
Bipolar: Coblation-plasma effect-cold ablation
Coblation is a breakthrough in intradiscal pressure reduction and nucleoplasty treatment, but gives good results in selected cases. Today, the effect created by the intradiscal ring in cervical disc protrusion has taken its place in the first place in the practical applications preferred by clinicians. In cervical coblation, vand provides 2 mm cavity formation and 10% volume reduction with an average application of 10 minutes in four directions (Figure-4C).
Coblation-nucleoplasty effect is achieved by opening channels in the lumbar region. Opening an average of 6 channels with coblation may be sufficient to reduce the disc pressure (Figure-4A). The inability to remove the plasma-debris formed in radiofrequency nucleoplasty should be considered as a disadvantage compared to mechanical nucleoplasty, and intradiscal cefazolin should be added to the previous discography. Residual debris can cause discitis.
Intradiscal Treatments:
Laser treatment in protruse discs, which started with Choy and Asher's reduction of disc pressure by vaporization in the nucleus pulposus in 1986, was called “percutaneous laser disc decompression” (PLDD). Complications of endplate thermal necrosis, root injury, and discitis of the laser probe are statistically insignificant in multicenter studies up to a hundred thousand cases. Complications in applications with proper dosage and frequency parallel to the Endplate are almost non-existent in correctly selected cases. However, cases of tetraplegia after cervical application reported by authors such as Martin Knight still brought thermal penetration and radiation safety to the spinal cord into the agenda.
PLDD is the transfer of 400-1000 joule Nd YAG laser energy into the disc in 10-30 minutes. In KTP laser, this time is 1-2 minutes. Using Richley Holmium, he transferred 1200-2000 joules of total energy, reporting 88% success. Neodymium has twice the ablation depth, thermal effect compared to Holmium. Excessive water absorption and removal of water from the environment increases the thermal effect and causes carbonization. The thermal effect, correct frequency selection and intermittent timing (relapse time) can be reduced. These parameters, which vary according to the wavelength, are 10-15 watts in Holmium YAG laser, and the repetition time of 10 hertz is 1200 joules in total. Casper recommends 1200j total energy using 13 Watt, 10 Hertz, 5 minutes of relapse and application time. Table-1 recommends the use of accepted doses after multi-center studies.
Another residual debris disadvantage caused by thermal effect in intradiscal treatment has disappeared with the introduction of Laser Asisted Spine Endoscopy (LASE) (Figure-5). Annuloplasty was achieved with percutaneous intervention, which provided visual and irrigation as well as laser, and it was possible to remove the debris. Although the distance of laser energy to the annular region does not cause a problem during subannular decompression and annuloplasty in the lumbar region, the distance of 10 mm to the posterior longutinal ligament origin in cervical applications is the operation limit. Sang-Ho Lee et al. They suggest 10 watts max, 10-15 hertz max energy in the cervical area. The same safe range should be preferred in the lumbar region. The nonablative limit is the energy transfer that does not exceed 500 joules at a time with a frequency of 10 hz and the application with 5 sec intervals.
Chiu recommends gradual energy application in thoracic disc laser application. It recommends starting with 10 watts in nonablative degrees, decreasing to 5 watts of energy and reducing the transferred power to 300 joules (12 hz). In the first stage, vaporization, in the second stage, only wrinkling and hardening are aimed. Sinovertebral neurolysis and denervation is evidenced by the patient's expression of pain reduction in the second stage. Chiu also recommends mechanically removing the debris and endoscopic control.
Intradiscal applications of radiofrequency energy take its place in the market in a range from monopolar RF IDET energy to coblation probes. While subannular heat up to 85 degrees provides annuloplasty and nucleoplasty in IDET treatment, the thermal effect transferred to the tissue was measured as 55 degrees. At the epidural distance, this temperature reaches 30 degrees. Even if the patient is sclerotomal, the pain should be taken into account during the application and the energy should be cut off (Figure-4D).
Coblation provides a safer nonthermal effect. Cervical application tips are particularly advantageous. The radiation effect of coblation, which works with mechanical-coblative principles by opening a canal in the lumbar region, is in the foreground. Both radiofrequency effects reduce disc pressure.
Spinal Procedure | Wavelength | Energy | Power | Pulse |
PLDD | Ho 2.1 Neodym 1064 | 0.6-1 Joule | 7-10 Watt | 8-12 Hz |
Foraminoskopik | Ho 2.1 | 0.8-1 J | 10-24 W | 10-24 W |
Foraminoplasti | Ho 2.1 | 1.2-1.5 | 12-30 W | 10-24 W |
Open Laser discectomy | Ho 2.1 | 0.8-1 J | 7-10 W | 8-12 Hz |
Periferik ven hemostazı | Ho 2.1 | 0.8-1 J | 10-24 W | 10-24 W |
Table 1: Different doses of laser energy applications according to spinal treatment options
Percutaneous Endoscopic Applications
Endoscopic laser applications that started in parallel with the definition of percutaneous endoscopic surgery by Hijikata and Kambin and continued with Yeung and Knight enabled the definition of the concept of foraminoplasty.
The brutal surgical results of lateral spinal stenosis are inconspicuous in the face of endoscopic detection and elimination of formaninal stenosis. During foraminoplasty, the problem of removing structures such as bone-osteophytes was solved by the shock wave effect of the laser (Figure-7). The destructive effect obtained by the continuous application of 30-40 W 10 Hz energy directly on the bone is not only sufficient to provide decompression, but also eliminates the situations that prevent the appearance such as bleeding-debris formation.
The use of radiofrequency energy in endoscopy provides great convenience in stopping epidural hemorrhages by the excision of the annular fibrils and the release of the nucleus fragment. Therefore, the use of both energies is preferred in endoscopic discectomy (Figure-6).
In spine endoscopic surgery, the choice of laser or radiofrequency energy should be approached selectively.
In intradiscal applications, the coblation method in cervical protrusions is safe and effective, and the same application can be performed, especially in asymmetric localized foraminal lumbar hernias, provided that protrusion is limited. Monopolar IDET application may be preferred in diffuse central and diffuse protrusions. However, laser nucleoplasty can be combined in painful discography. In this application, successful clinical results have been reported by eliminating the annular relaxation and providing pressure reduction with laser plasma effect in the nucleus.
Mechanical nucleoplasty is recommended especially in cases with protrusion and minimal extrusion together with annular tears in the lumbar region. Lee et al. reported that they also removed the pressure secondary to plastic annular deformation by applying subannular LASE annuloplasty after mechanical nucleoplasty. In our country, it will be possible to reduce posterior pressure with LASE and selective annuloplasty in the near future.
In endoscopic spine surgery, the bipolar RF probe provides great benefits in the excision of tissues holding the extrudate disc together with bleeding control. Cutting these tissues with mechanical tools is not preferred because it disrupts the field of vision with bleeding. On the other hand, after the disc is removed, the treatment is riveted by subannular RF application.
During the subannular application of the laser, contralateral protrusion can be intervened as well as annuloplasty, but LASE should be preferred for its safety. In addition, LASE can be a serious alternative to mechanical nucleoplasty, as it allows debris to be removed. In foraminoplasty, the superiority of laser is indisputable in the decompression stage performed by removing osteophytes and cutting the foraminal ligament. Considering that foraminoscopic shaver tips offer limited options and cause bleeding, it is clear that laser application will continue to be an integral part of foraminoplasty.
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