title: A biophysical explanation for Nd:YAG percutaneous laser disc decompression success.
abstract: OBJECTIVE
  To use pre- and postoperative CT density measurements to demonstrate changes achieved by Nd:YAG laser (1,064 nm) in protruded or extruded discs.
  
  
  BACKGROUND
  Nonendoscopic percutaneous laser disc decompression and nucleotomy (PLDN) with the Nd:YAG laser is an established minimal invasive treatment of discogenic pain syndromes in patients with bulging, protruded, or extruded intravertebral discs. Extremely high success rates involving improvement in the flow of cerebrospinal fluid in the dural sac and enhanced venous flow by MRI myelography are 80% lumbar, 86.5% cervical, and 98% thoracic spine. However, verification of reduced intradisc and intraspinal pressure by imaging procedures is difficult.
  
  
  METHODS
  Twenty-one patients, four women and 17 men, with an average age of 43.67 (range, 24-59) were selected. The patients showed lumbar radicular pain syndromes with monosegmental disc protrusion or extrusion, and monoradicular clinical symptoms. Measurements were performed preoperatively and on postoperative day 1.
  
  
  RESULTS
  The preoperative density measurements averaged 83.43, in agreement with the Houndsfield units (HU) described in the literature. Postoperatively, the reduction down to 66.33 HU had a statistical significance of p = 0.001 verified in the t test. Standardizing the measurements prior to laser irradiation to 100% produced an average 20% postoperative density reduction.
  
  
  CONCLUSIONS
  PLDN with the Nd:YAG laser (1,064 nm) markedly reduces the postoperative density in protrusion and extrusion of intravertebral discs. The excellent therapeutic results achieved with this method in discogenic pain syndromes can be verified by imaging procedures.
authors.affiliation: Facharzt fur Orthopedie-Rheumatologie, Facharzt fur Physikalische und Rehabilitative Medizin, Munich, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Hellinger
authors.forename: R
authors.initials: R
authors.lastname: Linke
authors.forename: H
authors.initials: H
authors.lastname: Heller
mesh_terms: D000328:Adult; D055592:Biophysical Phenomena; D001703:Biophysics; D019299:Decompression, Surgical / Q000379:methods*; D005260:Female; D006801:Humans; D007405:Intervertebral Disc Displacement / Q000601:surgery*; D053685:Laser Therapy; D008297:Male; D008875:Middle Aged; D014057:Tomography, X-Ray Computed