Laser Diskectomy
Needle placement
After sterile skin preparation, as for any surgical procedure, drape the area.
Identify the disk space with the help of a C-arm fluoroscope. Disk 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 disk. In most patients, the entry points in the skin for treating either the L4-L5 or the L5-S1 disk space are at the level of the iliac crest (very close to each other). The rubbery texture of the anulus 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.
Even with proper precautions, the use of fluoroscopy during minimally invasive laser microdiskectomy exposes the operator to significantly higher levels of radiation than open microdiskectomy does. [35]
Ultrasonography (US) has also been used to guide needle placement in laser diskectomy for cervical disk herniation and pain. [8, 9]
Laser application
Once the needle has reached the anulus, advance it through the anulus 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:
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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 [20]
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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 [22] ; 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
The great importance of correct needle placement with appropriate radiologic monitoring is emphasized. The needle tip must be just past the anulus, and the needle must be parallel to the disk axis, preferably halfway between the superior and inferior endplates.
Complications
In 1993, Choy's group tabulated the world experience with laser diskectomy up to that point, reporting two cases of diskitis.
Subchondral marrow abnormalities may occur in the vertebral endplates after Ho:YAG laser diskectomy. Possible causative mechanisms include thermal injury and photoacoustic shock. However, these changes probably do not affect surgical outcomes and appear to resolve over time.
In a study evaluating the effects of Ho:YAG laser ablation on postoperative low back pain and functional status after transforaminal endoscopic lumbar diskectomy, Li et al found that the only complication related to laser use was a burning sensation in the ipsilateral lower limb during the thermal procedure. [36]
A network meta-analysis by Wei et al compared the complications of the following eight surgical interventions for lumbar disk herniation [37] :
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Automated percutaneous lumbar diskectomy (APLD)
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Chemonucleolysis (CN)
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Microdiskectomy (MD)
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Microendoscopic diskectomy (MED)
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Open diskectomy (OD)
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Percutaneous endoscopic lumbar diskectomy (PELD)
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Percutaneous laser disk decompression (PLDD)
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Tubular diskectomy (TD)
In terms of complications, reoperation, operation time, and blood loss, the safest procedures for lumbar disk herniation were TD, PELD, PLDD, and MED. [37] PELD was associated with lower intraoperative complication rates, and PLDD as associated with lower postoperative complication rates.
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Disk herniation classification. (A) Normal disk anatomy demonstrating nucleus pulposus (NP) and anular margin (AM). (B) Disk protrusion, with NP penetrating asymmetrically through annular fibers but confined within AM. (C) Disk extrusion with NP extending beyond AM. (D) Disk sequestration, with nuclear fragment separated from extruded disk.
