A recent study that tracked the one year follow-up results of patients with lumbar spinal stenosis demonstrated that the Minimally Invasive Lumbar Decompression (MILD) procedure, an alternative to open laminectomy, reduces pain and morbidity with no serious adverse events. This is one of the first research studies demonstrating the effectiveness and safety of the MILD procedure, which is a budding alternative to traditional, open laminectomy. Findings presented at a session of the American Academy of Pain Medicine earlier this week assessed the results of the MILD procedure in 58 patients, representing 170 procedures, 1 year after surgery. The average patient age was 70 and most of the procedures were performed bilaterally, at 1 or 2 affected spine levels. The researchers used four metrics, namely the Visual Analog Scale (VAS), Oswestry Disability Index (ODI), Zurich Claudication Questionnaire (ZCQ), and the 12-item Short-Form Health Survey (SF-12v2), to track outcomes in the 58 patients.
At one-year follow-up, patients' pain scores fell by 40 percent. VAS scores went from a mean of 7.4 to 4.5, representing 79 percent improvement. ODI scores improved for 71 percent of the subjects, from a mean of 48.6 to 36.7 at one year post surgery. The ZCQ and SF-12v2 scores also improved, signifying decreased pain and enhanced physical function. The principle researcher, Dr. Deer, noted that while open surgery is associated with 20 percent adverse events, the MILD procedure in this study did not lead to hematoma, dural tears, nerve root damage, or need for blood transfusions.
The MILD procedure, marketed by Vertos, is a minimally invasive technique for treating lumbar spinal stenosis in patients who have failed conservative therapy but who have not undergone open surgery. MILD received 510(k) approval in 2006. During this outpatient procedure, access to the spinal canal is achieved percutaneously with the aid of fluoroscopy. Once the guidance needle reaches the interlaminar space, a cutting device is used to remove tissue and bone in order to decompress the part of the lamina where the disc collapsed. The surgeon then inserts a proprietary sculpting tool to reduce the size of the expanded ligament, which caused the nerve compression and pain. In traditional, open laminectomy, the entire ligament and bone causing the nerve compression is removed, whereas MILD only targets the portion of the tissue that is causing the compression. Medtronic's X-STOP interspinous process spacer also positions itself as a less invasive alternative to laminectomy due to its preservation of bony tissue; however, the X-STOP is an implantation, whereas MILD does not require any implant.
This study has key strengths in research design. Since the study was performed prospectively, metrics were measured in real-time, which removed any recall biases or other issues associated with retrospective data collection. Additionally, unlike many other studies, this research followed 4 metrics, thereby measuring several factors such as pain improvement, adverse events, and physical function. One major caveat to this study is that it does not compare MILD to open, traditional laminectomy. Therefore, while MILD has been shown to be safe and effective in reducing pain and improving physical activity, these results do not indicate that MILD is more effective than laminectomy. Additional studies should be performed, where MILD and traditional laminectomy are directly compared, to investigate whether one method is more effective.