A trial comparing minimally invasive spinal surgery with open spinal surgery to treat narrowing of the spinal canal

Surgical decompression of the lumbar canal in patients with significant symptoms of claudication or radicular pain and a radiological diagnosis of canal stenosis is both efficacious and well tolerated, with sustained long term benefits. Historically, lumbar canal stenosis was treated with complete laminectomy but recognition that the pathology is largely at the level of the disc and interlaminar space has led to less destructive approaches such as interlaminar decompression or laminotomy. Despite this, all published series report some morbidity and complications from surgery in what is typically an elderly population, such as dural tear, infection, persistent back pain and the need for blood transfusion or further surgical intervention. One concern is that of post-operative spondylolisthesis, which is thought to occur from disruption of the spinous processes and interspinous ligament, observed in up to 30% in some series. Minimally invasive techniques for decompression of the lumbar canal using a micro-endoscopic approach have been described and are growing in popularity. Instead of a midline posterior approach to the spinal canal, where the muscles are dissected bilaterally and the posterior spinal structures removed, a minimally invasive technique uses a unilateral, paramedian approach where the muscles are preserved and surgery is carried out through an 18mm diameter working tube. The surgical field is illuminated and magnified under the operating microscope and custom designed bayoneted instruments are employed to avoid obscuring vision. The spinal canal is decompressed in the same way as one would using an open approach but the posterior spinal structures are largely preserved, which offers a biomechanical advantage with the potential to reduce late spondylolisthesis. The less destructive approach should also reduce early post-operative back pain, promote more rapid mobilisation, and consequently reduce the number of inpatient hospital days. There is a growing body of evidence supporting the efficacy of this technique for treating patients with lumbar canal stenosis though there are concerns over the adequacy of decompression through a small operating tube and the learning curve associated with the adoption of this less invasive but potentially more restricted technique. Thus far, a number of observational studies have implied early advantages to patients offered minimally invasive over open lumbar canal decompression, there has yet to be a properly conducted and appropriately powered randomised controlled trial to confirm that the techniques are similarly effective in terms of medium to long-term functional outcome. A phase III non-inferiority trial design, i.e., to show that minimally invasive lumbar canal decompression is not inferior to standard open lumbar decompression, is considered to be the most stringent and statistically appropriate trial design to answer this important question. Trial participants will be recruited from patients undergoing elective open or minimally invasive decompressive lumbar laminectomy for degenerative lumbar canal stenosis at the Mater Misericordiae Private Hospital. After obtaining consent for the patients’ participation in the trial, they will undergo pre-operative clinical and radiological assessment by their consultant surgeon, including MRI and X-ray lumbar spine, in the usual way. Baseline questionnaires will be obtained pre-operatively. After randomisation to either surgical arm, open or minimally invasive lumbar decompression surgery will proceed in the usual way. There will be no changes to the usual surgical management of the patient resulting from the trial. Post operative management will proceed in the usual way, with no changes to normal post operative surgical management. Patients will complete outcome questionnaires prior to discharge. Patients will be assessed for discharge by a physiotherapist and their surgeon, and discharged at a clinically appropriate time in the usual way. Patients will be followed up at their routine appointment with the consultant surgeon. Outcome questionnaires will be completed at periods up to 24 months post operatively, and a follow up X-ray and MRI lumbar spine will be obtained. Data obtained will allow comparison of the outcomes of the two surgical procedures, including patient outcome measures, morbidity and adverse events, and radiological outcomes including extent of decompression and development of late spondylolisthesis.