A study from Weill Cornell Medical College (New York City, USA) has found that, in patients with lumbar spinal stenosis associated with degenerative lumbar spondylolisthesis, minimally invasive decompression may offer a better approach than open laminectomy.
The research team, led by Karsten Schöller, found lower rates of reoperation and secondary fusion surgery, less slip progression and greater satisfaction with the minimally invasive procedure.
The gold standard in surgical treatment for patients with degenerative spondylolisthesis is decompression via laminectomy with additional instrumented fusion.
Satisfactory outcomes for open laminectomy have been reported in certain lumbar spinal stenosis and low grade spondylolisthesis patients, however, the approach can involve extensive tissue damage, and may result in secondary instability.
Minimally invasive surgery may offer means to combat these iatrogenic effects.
The authors argued, that “the minimally invasive unilateral laminotomy (MIL) technique with ‘over the top’ decompression is particularly attractive because it limits trauma to the paravertebral muscles and facet joints and, on the same hand, permits sufficient and clinically effective bilateral neural compression.”
Does MIS decompression reduce the rate of secondary fusion?
To investigate the potential benefits of this procedure over open laminectomy, the research team performed a literature review. Their primary research question was “whether the minimally invasive decompression technique reduces the secondary fusion rate.”
Using the MEDLINE database, the team found 589 results searching for “lumbar spondylolisthesis” and “decompression surgery” with no search limits. Articles were excluded for duplication, insufficient description of technique, as well as studies including patients with certain clinical variables.
Thirty-seven articles survived the selection process, and the team extracted information including the decompression technique, the study type, and details about the patient cohort.
“Meta-analyses for (1) secondary fusion proportion, (2) overall reoperation proportion, and (3) satisfactory outcome proportion” were performed using StatsDirect software. Data were stratified according to procedure type. The researchers set significance at p= ≤0.2.
The total cohort of the 37 studies—published between 1983 and 2015—was 1,156 patients. Eighteen papers reported outcome after MIL, and 19 reported outcome following open laminectomy.
Two randomised controlled trials were included: “one comparing microsurgical unilateral laminotomy with unilateral laminectomy” and one “comparing open laminectomy with instrumented and with noninstrumented fusion.”
In addition, 32 cohort studies and case series were included (eight prospective, 24 retrospective). The study design of two papers was unclear.
Authors noted results and differences in the reporting of complications, reoperations with and without fusions, postoperative progression of spondylolisthesis and clinical outcome. The team’s analysis revealed improvements in reoperation and fusion rates, slip progression and patient satisfaction for MIL in patients with lumbar spinal stenosis associated with degenerative lumbar spondylolisthesis.
“MIL is not only a good alternative to laminectomy,” the authors added, “In selected patients, it may even be a more cost-effective alternative to fusion surgery with a lower complication rate.”
Limited by current evidence base
The researchers were limited by a lack of randomised controlled trial directly comparing open laminectomy and MIL in degenerative spondylolisthesis patients.
In addition, diversity within the analysed studies hindered its scope. For example, the definitions of preoperative spondylolisthesis and postoperative slip were heterogeneous among the included studies.
Looking to the future, the team argued that “better quality studies that compare open with minimally invasive decompression” and “studies that compare MIL with fusion in lumbar spinal stenosis and degenerative lumbar spondylolisthesis patients” are needed to better evaluate the benefits of each procedure.
“Radiological predictors for a good outcome after MIL”, in addition, should be defined.
The paper—which was selected as the Neurosurgery Top Spine & Peripheral Nerve Paper of the Year— is to be presented at the annual 2017 Congress of Neurological Surgeons Annual Meeting (CNS: 7–11 October 2017, Boston, USA).