Laser Discectomy Technique

Updated: Aug 30, 2017
  • Author: Jasvinder Chawla, MD, MBA; Chief Editor: Erik D Schraga, MD  more...
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Technique

Laser Discectomy

Needle placement

After sterile skin preparation, as for any surgical procedure, drape the area.

Identify the disc space with the help of a C-arm fluoroscope. Disc margins are made clear by craniocaudal movement of the fluoro tube. At this time, rotate the fluoro tube obliquely to bring the superior articular process to the midline.

Introduce an 18-gauge 7-in. needle immediately anterior to the superior articular process and superior to the transverse process via a triangular safe zone. Advance the needle in 1- to 2-cm increments in a "stop and look and go" process, so that the needle's course can readily be changed if it is found not to be directed properly.

View the progress of needle advancement in anteroposterior and lateral projections with the C-arm fluoroscope, which must be of sufficient strength and quality to give a clear view of the area. Upon completion, the needle tip should be at the center of the disc. In most patients, the entry points in the skin for treating either the L4-L5 or the L5-S1 disc space are at the level of the iliac crest (very close to each other). The rubbery texture of the annulus is easily felt with the tip of the 18-gauge needle.

Fluoroscopy precautions include the wearing of lead aprons by all personnel in the procedure and operating rooms. Wearing lead gloves and avoiding exposing the operator's hands also reduces radiation exposure.

Despite proper precautions, the use of fluoroscopy during minimally invasive laser microdiscectomy exposes the operator to significantly higher levels of radiation than open microdiscectomy does. [27]

Laser application

Once the needle has reached the annulus, advance it through the annulus and into the nucleus pulposus for a distance of approximately 1 cm. Then mark the fiber to prevent penetration of the tip more than 1 cm beyond the end of the needle.

Owing to differences in absorption, energy requirements and rates of application also differ among lasers, as illustrated by the following examples:

  • Choy and Ascher reported using a neodymium (Nd):yttrium-aluminum-garnet (YAG) laser as 20 W of continuous energy delivered in 1-second pulses with 1-second pauses until 1000-1850 J was delivered [13]
  • Davis used a potassium titanyl phosphate (KTP) laser as 10-15 W of continuous energy in 0.5-second pulses with 0.5-second pauses for a few minutes [15] ; the commercial KTP laser is designed to deliver up to 1250 J before it shuts down automatically, and it allows another 300 J to be administered before it issues a warning
  • Sherk et al used the holmium (Ho):YAG laser in the pulsed mode at 10 Hz [17, 18]

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 must be parallel to the disc axis, preferably halfway between the superior and inferior endplates.

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Complications

Discitis is the only documented complication of laser discectomy. In 1993, Choy's group tabulated the world experience with laser discectomy, reporting two cases of discitis.

Subchondral marrow abnormalities may occur in the vertebral endplates after Ho:YAG laser discectomy. Possible causative mechanisms include thermal injury and photoacoustic shock. However, these changes probably do not affect surgical outcomes and appear to resolve over time.

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