Laminectomy

This operation is also called a diskectomy, but the entire disk is not removed.  Only the herniating portion of the disk is removed, which is mostly nucleus pulposus, thus the abbreviated term for any disc protrusion is HNP, herniated nucleus pulposus.  The surgical approach to an HNP is through a midline incision followed by retraction of the paraspinal muscle (not cutting it), on the side of the HNP. Then only part of the underlying lamina is removed.  Laminectomy is often used for this procedure but only part of the lamina on one side is removed and the lamina bears no weight, so the spine isn’t weakened.

The nerve root is found and carefully retracted to expose the herniated fragments of disc compressing it.  After they are removed most surgeons then use a small spoon-like instrument on a long stem called a curette to scrape off any remnants of loose cartilage inside the disc (nucleus pulposus) in order to reduce the rate of recurrence. Then a little blood is allowed to ooze into the disc space cavity and clot.   With time this clot is replaced with what is called fibrocartilage, tough tissue similar to a scar on the skin. A fusion isn’t needed in most cases. The recurrence rate is only about 5% over 5 years and 10% overall.

Studies have show that the success rate is not improved by adding a fusion, which prolongs the operation, requires more time, a larger exposure and increases the risk of infection; the fusion doesn’t always “take” and even after a successful fusion, the space above or below has an increased risk of getting an HNP (see Disk and Posterior Fusion).

Laminectomy & Posterior Fusion (Disk and Fusion, D&F)

In some cases, say, with unstable spondylolysthesis, a fusion is done in addition to simple HNP removal.  That requires stripping and retraction of muscles on both sides of the spine, drilling off bone surfaces on both sides to expose bone marrow, then placement of bone grafts across the disc space to heal (fuse) like as bone fracture does.

It’s hard to stabilize the lower spine. Too much motion across the grafts will keep them from healing. The grafts must come from the patient, usually the rim of the pelvis (“the hip”) or from bone bank (cadaver bone). To stabilize the spine internally, screws can be placed in the bone on each side of the graft and connected with rods.  They are usually left in place but can be removed later if needed (see pedicle screws).

Percutaneous Disk Operations

Percutaneous (across the skin) indicates some kind of needle procedure.  It was hoped years ago that injecting chymopapain (the digestive enzyme in Adolf’s Meat Tenderizer) into a herniated disk would allow the HNP to resolve, but the results weren’t very good and severe allergic reactions in random patients killed that procedure.  Needles have also been used to deliver heat to the interior of disks with the purpose of shrinking them like frying bacon. Radiofrequency generators or lasers have been and still are used to deliver the heat. That may help a bulging disc but if a fragment has herniated, shrinking the interior of the disk doesn’t seem likely to help.

So far, I don’t know of any randomized, controlled trials (RCT) that have shown a benefit. I am concerned about the use of lasers for disk surgery. I taught Laser Neurosurgery for several years and found it detrimental in disk surgery because of the heat generated in the disk tissue. Several patients woke up with severe back pain that was hard to control even with morphine, something I hadn’t experienced before.  Furthermore, a laser beam won’t go around corners and often in disk surgery you need to use a blunt hook or an angled forceps to tease out disk fragments from beneath a nerve root that can’t be retracted.