Scientific Basis of Minimally Invasive Spine Surgery

In Brief Study Design. Literature review. Objective. To describe the scientific basis of minimally invasive spine surgery as it relates to posterior lumbar surgery. Summary of Background Data. Minimally invasive spine (MIS) surgery is predicated on several basic principles: (1) avoid muscle crush injury by self-retaining retractors; (2) do not disrupt tendon attachment sites of key muscles, particularly the origin of the multifidus muscle at the spinous process; (3) use known anatomic neurovascular and muscle compartment planes; and (4) minimize collateral soft tissue injury by limiting the width of the surgical corridor. Methods. Literature review. Results. The conventional midline posterior approach for lumbar decompression and fusion violates these key principles of MIS surgery. The tendon origin of the multifidus muscle is detached, the surgical corridor is exceedingly wide, and significant muscle crush injury occurs through the use of powerful self-retaining retractors. The combination of these events leads to well-described changes in muscle physiology and function. MIS surgery is performed using table-mounted tubular retractors that focus the surgical dissection to a narrow corridor directly over the surgical target site. The path of the surgical corridor is selected on the basis of anatomic planes, specifically avoiding injury to the musculotendinous complex and the neurovascular bundle. Conclusion. With these relatively simple modifications to surgical technique, significant improvements in intraoperative blood loss, postoperative pain, surgical morbidity, return of function, among others, have been achieved. However, MIS techniques remain technically demanding and a significant complication rate has been observed during the initial learning curve of the procedures. The key concepts in minimally invasive spine surgery are as follows: (1) avoid muscle crush injury; (2) protect the multifidus muscle tendon origin; (3) use known anatomic planes; and (4) minimize the surgical corridor. The use of table-mounted tubular retractor systems keeps retraction pressures low. The use of multiple smaller incisions through known surgical planes.