Biomedical subjects
Publications and source records attributed to D S Choy.
Percutaneous laser disc decompression (PLDD) was pioneered by Dr. Peter Ascher and myself in 1986. This report describes patient selection, operative technique, laser dosimetry, and results in 352 cases with an 8 1/2-year follow-up. The conclusion is that PLDD is relatively non-invasive, safe, simple and effective.
The great importance of correct needle placement with appropriate radiologic monitoring is emphasized. The needle tip must be just past the annulus, and the needle itself must be parallel to the disc axis, and preferably halfway between the superior and inferior end-plates. Dosimetry is described. A novel (extrathecal) approach to the L5-S1 disc when this cannot be entered from a dorsolateral angle is described. Our technique for cervical disc PLDD is briefly described.
From 1986 to the present, a period of 9 years, our group has performed 389 PLDD procedures in 322 patients with an overall success rate according the MacNab criteria of 75% and a complication rate of 1%. This compares to the 2.4% of traditional open surgery. Of our patients 33 required subsequent surgery, an incidence of approximately 10%.
The author describes a posterior, extrathecal approach to the L5-S1 disc for percutaneous laser disc decompression that is safe, simple, and without neurologic sequelae. The conclusion is that the extrathecal approach is safe and preferable to repeated unsuccessful attempts to enter the L5-S1 disc with a curved needle.
This discussion is an update on the U.S. advances in percutaneous laser disc decompression (PLDD). This report summarizes the knowledge that has been gained about the procedure, advances in technique, and increased information about the three lasers currently in use for PLDD: KTP, Nd:YAG, and holmium. A new surgical approach to the L5-S1 disc is described. It is concluded that PLDD has become an established procedure that will be more widely used because it is simple, effective, and reasonably safe.
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Percutaneous laser disc decompression (PLDD) is being performed in multiple centers in the United States, Germany, Austria, France, and Switzerland with the Nd:YAG having the longest follow up at more than 75 months. The experience with this procedure, in both humans and animals, carried out over the past decade is presented along with a detailed discussion of the surgical procedure. Conditions that favor such surgery and contraindications to the procedure are also presented. There are a number of important advantages to PLDD that make it a procedure that merits continued investigation. Because PLDD is relatively noninvasive, it can be repeated. Because there is no cutting, there is no perispinal scar formation, with possible future pain secondary to entrapment of nerves by scar. Because of its effectiveness for treatment, the laser, in this application, should prove to be an important addition to the spinal surgeon's armamentarium.
In vitro and in vivo measurements of intradiscal pressure under load and without load, respectively, before and after laser ablation of small volumes of nucleus pulposus revealed significant falls of intradiscal pressure. This is the basic principle underlying percutaneous laser disc decompression (PLDD).
The authors present a new advance in the treatment of herniated disc disease using percutaneous Nd:YAG laser to vaporize a small portion of nucleus pulposus, thereby decompressing the disc. In vitro and in vivo animal data are presented. Three hundred seventy-seven magnetic resonance imaging or computed tomography scan-documented, herniated, nonsequestered lumbar intervertebral discs with corresponding clinical findings in 333 patients were so treated in an outpatient setting. The longest follow-up was 62 months, with a mean of 26 months. According to the Macnab criteria, there was a good to fair response in 261 patients (78.4%), and a poor response in 72 (21.6%); 166 patients experienced relief of pain during the procedure. One-third of repeat magnetic resonance imaging scans at 4-6 months postlaser treatment showed modest to moderate decrease of disc herniation.
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The interaction of laser radiation with the nucleus pulposus from autopsy specimens of human intervertebral disks was evaluated at different wavelengths (193 nm, 488 nm & 514 nm, 1064 nm, 1318 nm, 2150 nm, 2940 nm, and 10600 nm). A significant correlation of linear least squares fit of the mass ablated as a function of incident energy was found for all lasers used except the Excimer at 193 nm. The 2940-nm Erbium:YAG laser was most efficient in terms of mass of disk ablated per joule in the limited lower range where this wavelength was observed. At higher energy levels, the CO2 laser in the pulsed mode was most efficient. However, the Nd:YAG 1064-nm and 1318-nm lasers are currently best suited for percutaneous laser disk decompression because of the availability of usable waveguides. Carbonization of tissue with the more penetrating Nd:YAG 1064-nm laser increases the efficiency of tissue ablation and makes it comparable to the Nd:YAG 1318-nm laser.
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While the history of laser begins in 1951, the first medical application is reported by Goldman in 1962. In cardiovascular surgery McGuff first used a Ruby-Laser in 1963 for the experimental ablation of atherosclerotic plaques. After a long time of investigations and new developments in laser technology first clinical applications were performed by Choy and Ginsburg in 1983. Since that time the effectiveness of laser angioplasty in coronary and peripheral vessel is investigated in several clinical trials and first results are encouraging, so that laser is about to find its place in the treatment of cardiovascular diseases too.
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The difficulty of removing intramedullary methylmethacrylate (MM) in revision of hip prostheses is considerable. To facilitate its removal from bone, Nd:YAG laser energy was delivered to a bovine anatomic specimen of the femur with the medullary canal filled with MM. Through an endoscope the laser was observed to soften and ablate the methyl methacrylate. The vapors generated by this process were analyzed by mass spectrometry. The two chief components were hydrogen and carbon monoxide, followed by carbon dioxide, methane, acetylene, and C3 unsaturated hydrocarbons. A high capacity smoke evacuator must be used in conjunction with laser vaporization of methylmethacrylate. The method should be evaluated under in vivo conditions in dogs before it is attempted in patients.