A 2009 systematic review of surgery for back pain, commissioned by the American Pain Society (APS), was conducted by the Oregon Health Sciences University Evidence-Based Practice Center (Chou, 2009). Four higher quality randomized trials were reviewed that compared surgery to nonsurgical therapy for spinal stenosis, including 2 studies from the multicenter Spine Patient Outcomes Research Trial (SPORT) evaluating laminectomy for spinal stenosis (specifically with or without degenerative spondylolisthesis) (Weinstein, 2007) (Weinstein, 2008).  Baseline pain scores averaged 31 to 32 on the SF-36 bodily pain score or 7 on a 0 to 10 pain scale. Two trials permitted enrollment of patients with >12 weeks of symptoms, however, symptoms were present for more than 6 months in the majority of patients in all trials. All 4 trials found that initial decompressive surgery (laminectomy) was slightly to moderately superior to initial nonsurgical therapy (e.g., average 8 to 18 point difference on the SF-36 and Oswestry Disability Index). Although differences were decreased at longer follow-up, interpretation of results was complicated by the large proportion of patients in the nonsurgical therapy group who crossed over to surgery before the final follow-up. Dural tears were the most common complication of laminectomy, occurring in 7% to 11% of patients. There was insufficient evidence to determine the optimal adjunctive surgical methods for laminectomy (i.e., with or without fusion, and instrumented vs. non-instrumented fusion) in patients with or without degenerative spondylolisthesis.

 

A 2005 study randomized 120 patients with lumbar stenosis to bilateral laminotomy, unilateral laminotomy or laminectomy (Thome, 2005).  Patients were refractory to at least 3 months of conservative therapy, with neurogenic claudication or radiculopathy, imaging evidence of degenerative lumbar stenosis, and absence of herniation or instability. Three patients were excluded due to discectomies during surgery; follow-up of at least 1 year was obtained in 110 patients (94% of the cohort of 117 and 97% of surviving patients). The average visual analog score (VAS) for overall pain at baseline was 7.5, improving to 2.3 for bilateral laminotomy, 3.6 for unilateral laminotomy, and 4 for laminectomy. Neurogenic claudication improved in 92% of patients with bilateral laminotomy, compared with 74% treated with unilateral laminotomy and 68% of patients who had laminectomy. Similar improvements were obtained for the SF-36 (post-op bodily pain scores of 61, 47, 45, respectively), Roland-Morris scale (8, 8.5, and 11 post-operatively), and patient satisfaction scores (97%, 74%, and 74% satisfied). The perioperative morbidity rate was lower with bilateral laminotomy (5%) than unilateral laminotomy (17.5%) or laminectomy (22.5%), due primarily to the incidence of dural tears with the 3 procedures. Blinding of patients to the procedure to which they were randomized was not described; the potential for bias is unknown.

 

A 2008 quasi-randomized study from Asia compared laminoforaminotomy with laminectomy in 152 consecutive patients (Fu, 2008). Inclusion criteria required that each patient have 1) neurogenic claudication as defined by leg pain limiting standing, ambulation, or both; 2) a history of exercise intolerance; 3) magnetic resonance imaging (MRI), myelogram, or computed tomography (CT) confirmation of compressive central stenosis (central sagittal diameter less than 10 mm) with or without lateral recess stenosis (lateral recess diameter less than 3 mm); and 4) failure of conservative therapy after an adequate trial (not defined). Patients were excluded from the study if they had 1) previous surgery at the same level, 2) isthmic spondylolisthesis, 3) congenital spinal stenosis less than 8 mm caused by short pedicles, 4) dynamic instability, 5) cauda equine syndrome, 6) worker’s compensation claim or other litigation, 7) dying of other disease or otherwise lost to follow-up. At an average 40 months after surgery, the Oswestry Disability Index and VAS for back and leg pain and were low (e.g., < 1 on VAS) for both groups, and significantly lower for laminotomy. The proportion of patients with good to excellent results (absent or occasional mild back and leg pain and the ability to ambulate more than 1 mile or 20 minutes) was 89% for patients treated with laminotomy and 63% for patients treated with laminectomy. Seven percent of patients treated with laminectomy had poor results at the final interview (range of 27-58 months), compared with none in the laminotomy group. The study is limited by the lack of information about the number of patients lost to follow-up and the lack of blinding.

 

No comparative trials with MEDL were identified. In 2009, Castro-Menendez et al. reported 4-year outcomes (from a prospectively maintained institutional database) of 50 patients with LSS who were treated by single level microendoscopic decompression. Twenty of the patients received microendoscopic discectomy at the same time, which may be considered a part of the endoscopic procedure that can be performed when needed (Castro-Menendez, 2009). Inclusion criteria for the study were 1) low back pain and/or radicular pain (70%), 2) neurogenic claudication (58%), 3) personal history of exercise intolerance, 4) radiological/neuroimaging evidence of degenerative lumbar stenosis, 5) clinical-radiological concordance, 6) failure of conservative management after at least 6 months of therapy. Excluded from the study were patients with 1) nonclinical-nonradiological correlation, 2) congenital stenosis, 3) previous lumbar spinal surgery, 4) higher than grade I degenerative spondylolisthesis, 5) spondylolisthesis with spondylolysis, 6) preoperative instability, 7) more than 1 level clinically affected, 8) associated degenerative scoliosis of more than 20 degrees, and 9) the presence of an associated pathology such as acute inflammation, tumor, or cauda equine syndrome. The mean postoperative hospital stay was 3.2 days. The Oswestry Disability Index decreased by 30 (65.2 preoperatively), leg pain VAS by 6.02 (8.3 preoperatively) and lumbar pain VAS by 0.84 (5.3 preoperatively) at an average 4 year follow-up (range 24-72 months). Of the 29 patients (58%) with neurogenic claudication, 21 (72%) reported improvement in the ability to walk (> 1 mile) at the end of the study. Dural tears occurred in 5 patients (10%), all in the first 25 interventions. One patient (2%) had epidural hematoma causing cauda equine syndrome. Although the study may be relatively representative of outcomes during the learning curve for this highly selected population, the report is limited by the restricted selection criteria, retrospective review, and lack of blinding.

 

A 2010 publication describes a chart review of 90 consecutive patients treated in the U.S. (14 physicians in 12 facilities) with mild® devices under fluoroscopic guidance (Deer, 2010). No efficacy data were reported. No major adverse events (dural puncture or tear, blood transfusion, nerve injury, epidural bleeding, or hematoma) were found in the chart review. The authors state that prospective randomized studies have been initiated to evaluate the efficacy of this new procedure.

 

A search of ClinicalTrials.gov in February 2010 found several ongoing trials on IG-MILD by Vertos Medical. Two studies are open label (NCT00749073, NCT00956631), the third (NCT00995371) is a randomized trial comparing minimally invasive lumbar decompression with epidural steroid injection. The study has an estimated enrollment of 40 patients with symptomatic LSS primarily caused by dorsal element hypertrophy. The estimated study completion date (26-week follow-up) is estimated for June 2010.

 

Posterior decompression for lumbar spinal stenosis has been evolving towards increasingly minimally invasive procedures in an attempt to minimize post-operative morbidity and spinal instability. In general, the literature comparing surgical procedures is limited. The evidence available suggests that less-invasive surgical decompression may reduce perioperative morbidity without impairing long-term outcomes when performed in appropriately selected patients. In contrast to surgical decompression, the mild® procedure is a percutaneous decompressive procedure performed solely under fluoroscopic guidance (e.g., without endoscopic or microscopic visualization of the work area). This procedure is indicated for central stenosis only, without the capability of addressing nerve root compression or disc herniation, should it be required. Due to the unknown impact of these limitations on health outcomes, randomized controlled studies in appropriate patients are needed to compare this novel procedure with the established alternatives. Although studies have been initiated, no evidence is available at this time to evaluate the efficacy of image-guided percutaneous lumbar decompression.