Surgical treatment of the herniated lumbar disc is one of the most common neurosurgical procedures. In the last few decades there has been a vast improvement in neurosurgical treatment of the lumbar disc herniation, and a lot of new treatment options have been devel-oped. There has been an expansion of endoscopic procedures like percutaneous endoscopic discectomy, laparoscopic discectomy, stereotactic guided discectomy, and an endoscope as-sisted discectomy, all of which are often used in our Department.
The idea of using an ultrasonic aspirator for emulsification and aspiration of the lumbar and cervical intervertebral disc is not new. Current experiences in high energy ultrasound application yielded good results in neurosurgery, but so far only its application on the brain tissue was analyzed. The application of the high energy ultrasound on intervertebral disc tis-sue remains to be explored.
The aim of this research is to display the effect of the high energy ultrasound application on the intervertebral disc tissue, and to analyze its application in lumbar disc herniation treatment.
The final ultrasonic effect depends on the shape and intensity of the ultrasonic field, du-ration of its application and the amount of the ultrasonic energy as well as the characteristics of the tissue on which the ultrasound is applied.
This research initially determined the acoustic characteristics of the contact ultrasound probe during its application on the intervertebral disc tissue. The acoustic power output measurement was analyzed using three types of experiments: calorimetric measurements, acoustic power deployment in the free acoustic field, and tip-displacement amplitude of the probe.
The mechanism of high-intensity ultrasound effects on the tissue is still poorly under-stood, but the potential mechanisms include acoustic cavitation, shock-wave induced stress-es, acoustic microstreaming, direct jackhammer effect, and thermal lesion. All results meas-ured in free acoustic field are expected to vary in real situations.
Acoustic parameters like the acoustic power and the acoustic cavitation shape are modi-fied during ultrasound application because of the damaging cavitational effects upon the flat surface of the contact probe tip.
The investigation was carried out on 189 intervertebral discs extracted during autopsy on 63 cadavers. An ultrasonic contact probe with 2.2 mm diameter was used to perform point lesions in the disc tissue with modifying the electric power of the ultrasonic generator (The tuning button of the generator was 50%, 75% and 100% of the electric power level respec-tively) with the insonification duration of 20 seconds.
The results showed that the size of necrotic area depends on the level of the acoustic power and intensity. The higher the acoustic power the wider the area of the necrotic nucleus pulposus tissue.
The difference in the level of destruction between discs in younger cadavers (younger than 55 years) and in older ones was observed which was attributed to different amount of water in the tissue.
Finally the efficacy of the tissue fragmentation caused by high energy ultrasound is higher in calcified tissue comparing to cartilage tissue
