Microdiscectomy, Minimally Invasive
"Discectomy" refers to removing disc. This procedure is usually done when a piece of disc is bulging out or has broken off and is touching or compressing a nerve. Removing the disc does not involve fusing the spine.
The "micro" part of the procedure name refers to the fact that the microscope is used for magnification.
In this case, the MRI presented here with a side (or lateral) view shows the bones, which are one shade of gray, with the discs acting a cushions between each level. At the lowest level, L5-S1, there is a large piece of disc which has been extruded backward toward the nerves.
This patient had some back pain, but the majority of symptoms involved pain down the leg, often referred to as sciatica.
By using a minimally invasive approach, the dissection of the covering soft tissues can be minimized, leaving more blood supply to the surrounding tissues with at least a theoretic potential for a quicker recovery.
Similar to the lumbar fusion, fluoroscopic X-ray in the operating room can be used to verify that the entrance is at the correct level.
The needle is used to localize the level, a small incision is made, and the tubular retractors are inserted. 
A working portal is created.
The operating microscope can be used for greater magnification to perform this surgery with less effect on surrounding tissues.
Using the tubular retractor system, a path can be created by spreading the muscles instead of cauterizing them off the bone, so the back of the spine can be reached.
A small hole is drilled in the back of the spine bone called the lamina. Since this part of the procedure involved making an opening or hole in the lamina, it is referred to as laminotomy.
Through this opening, the herniated disc can be safely removed, as the nerves are retracted to the side. This procedure can be done through the tube, even though this illustration shows regular retractors.
By removing the compression on the involved nerves, the patient will usually wake up in the recovery room with their leg pain being gone.
Link to Risks of Surgery.