Percutaneous Laser Disk Decompression A
Sciatica, which is usually caused by herniation of an intervertebral disk, is a common problem with an annual incidence of 5 per 1000.1,2 In 60%–80% of patients experiencing their first episode of radicular pain, the symptoms recede to a nondisabling level within a period of 6 weeks.2 The remaining group of patients qualifies for (surgical) intervention.3-5 Because of the considerable morbidity and convalescence period inherent to conventional lumbar disk surgery, there has been an ongoing search for less-invasive methods of treatment.
Percutaneous laser disk decompression (PLDD) is one of the so-called "minimally invasive" treatment modalities for contained lumbar disk herniation. The treatment is performed percutaneously, so morbidity is expected to be lower and convalescence period is postulated to be shorter than for conventional surgery. Because of the minimally invasive nature and the fact that return to work is usually possible within a few days after treatment, PLDD appears to be an interesting alternative to conventional surgery; however, considerable skepticism still greets PLDD. Opponents usually dismiss PLDD as being an experimental treatment with unproven efficacy, whereas those advocating the use of PLDD tend to present it as some kind of miracle treatment. In this review, we try to establish a balanced view on the current position of PLDD in the range of treatment modalities for lumbar disk herniation.
The idea of using laser in the treatment of lumbar disk herniations arose in the early 1980s. After a series of in vitro experiments Choy and colleagues performed the first PLDD on a human patient in February 1986.6 The US Food and Drug Administration approved PLDD in 1991. By 2002, some 35,000 PLDDs had been performed worldwide.7
Treatment Principle of PLDD
The treatment principle of PLDD is based on the concept of the intervertebral disk being a closed hydraulic system. This system consists of the nucleus pulposus, containing a large amount of water, surrounded by the inelastic annulus fibrosus. An increase in water content of the nucleus pulposus leads to a disproportional increase of intradiskal pressure. In vitro experiments have shown that an increase of intradiskal volume of only 1.0 mL causes the intradiskal pressure to rise by as much as 312 kPa (2340 mmHg).6 On the other hand a decrease of intradiskal volume causes a disproportionally large decrease in intradiskal pressure. The radicular pain that characteristically accompanies lumbar disk herniation is the result of nerve root compression by the herniated portion of nucleus pulposus. A reduction of intradiskal pressure causes the herniated disk material to recede toward the center of the disk, thus leading to reduction of nerve root compression and relief of radicular pain. In PLDD, this mechanism is exploited by application of laser energy to evaporate water in the nucleus pulposus. Laser energy is delivered by a laser fiber through a hollow needle placed into the nucleus pulposus. The needle is placed into the intervertebral disk under local anesthesia. Apart from evaporation of water, the increase in temperature also causes protein denaturation and subsequent renaturation. This causes a structural change of the nucleus pulposus, limiting its capability to attract water and therefore leading to a permanent reduction of intradiskal pressure by ≤57%.