Failed Back Surgery Syndrome
Failed back surgery syndrome (FBSS) is when back pain and/ or leg pain recurs or persists
following an otherwise successful back surgery. The goal of back surgery is to relieve pain by correcting the cause of the pain, such as relieving the pressure on a nerve root or stabilizing a damaged joint or disk. Surgery rather than medical therapy is used when there is a specific target that is not only felt to be causing the pain, but is correctable with surgery. Prior to surgery, there are generally years of progressive damage to the nerves in the area that more conservative therapy has not helped. Following surgery there is the development of scar tissue and no assurance the damage to the nerve will resolve. Most physicians view surgery as a last ditch effort to relieve long standing back pain. While the goal is to relieve the pain, a significant number of people undergoing back surgery get only marginally better and some may actually get worse.
Some surgeries are more successful than others
Surgeons do not operate on ‘pain’. They simply ‘correct anatomy’ and operate on the concept that if there is an anatomical ‘lesion’ such as a ruptured disk that presses on a nerve, and the patient experience pain that can be traced back to that nerve, correcting the disk should relieve the pressure and in turn the pain. This can help, or the nerve can be so damaged by the long term pressure that it continues to hurt after the pressure is relieved. According to sources, certain conditions have a better chance of relieving pain compared to others. For example.
1/ Disk compression of a nerve with referred pain to the distribution of that nerve. A classic case is sciatica caused by a lumber disk herniation can be effectively treated by surgery. Surgery for ‘low back pain’ and a herniated disk without sciatica (radicular pain) is less effective.
2/ Spinal fusion for a damaged spinal joint (spondylolisthesis where a vertebral joint fracture causes one vertebrae to ‘slide’ backwards over another) responds better to back surgery than multilevel degeneration of the joints due to arthritis and wear.
The key is to clearly identify a target and relate it directly to the pain, and to have a specific lesion that has responded well to surgery in other patients. The overall condition of the spine, quality of the bone, and muscular support of the spinal column also play a role in the decision for surgery. Smoking has also been shown to decrease the success of lumbar spinal surgery and patients are encouraged to stop prior to surgical intervention. Post operative rehab is also helpful. So are reasonable expectations- a 50 year old with chronic back pain will never get the back of a 15 year old through surgery, but may obtain relieve of part of their chronic pain and get increased function.
Specific Types of Failed Back Surgery
For more in depth discussion of specific types of failed back surgery we can look at several common procedures- what they are and why they fail.
When two or more vertebral levels are unstable and lose their connections and alignment, a possible surgical solution involved ‘fusing’ the levels together by inserting a bone graft (generally obtained from the patient’s own hip) in the joint space between the vertebrae. An internal ‘splint’ in the form of screws and plates/rods holds the joint still as the bones grow into each other and form a single, long vertebrae where two separated by a disk were originally. In a best case scenario, this fusion takes at least a year to develop, prior to that the joint is held together by metal.
Metal can weaken with repeated bending, twist and even break, causing the splint to fail or come out of alignment. The bone can refuse to heal and fuse together- continuing the instability of the joint.
Another weakness of this procedure is that the spine has joints between each vertebrae and is meant to move using these joints. This is the basic flexibility and ‘springiness’ of the spine needed for us to move normally. It also functions as a shock absorber as we walk. Fusing a joint removes the contribution of the joint to the overall function of the spine, and transfers the load normally handled by that joint to the joint above and below. It is not uncommon for a failed joint to be fused and repaired, only to have the joint above it fail later from the increased strain. To continue the process from tailbone to the base of the skull would mimic a very disabling condition known as Ankylosing Spondylitis.
Lumbar Laminectomy or Decompression
Lumbar decompression surgery is used to remove a fragment of disk or bone that is pressing on a nerve. The goal is to remove the entire source of irritation to the nerve, with a hope of decreasing pain and increasing function. Following the surgery, it will take at least 3 months for the damaged nerve to heal. If there is an improvement in the leg pain of sciatica by three months after lumbar decompression, it should continue to heal, with maximum improvement about a year after the surgery. If there is no improvement by three months, the surgery may not have worked and other options may need to be considered.
Even after a successful surgery, a disk can herniate and press on the nerves again. The bone as it heals can create spurs and press on the nerves again. Both situations can result in the return of the original pain or new pain as the spine adjusts to a new dynamic following the surgery.
Another issue is that due to technical issues with the evaluation the scans and other workup could suggest the surgery be done at one level, but the actual cause of the pain is hidden at another level. While pain in the specific distribution of a spinal nerve can provide strong evidence of the lesion being at that level, every body is slightly different and a specific spinal nerve can have input from adjacent levels. In the setting of low back pain without a specific nerve distribution, the precision of the level is in more doubt, with a poorer outcome of surgery in terms of symptom relief and function. Small fragments of bone and disk material can be missed at surgery, and the nerve itself may be damaged by the procedure.
Scar Tissue as a cause of Failed Back Surgery
Any surgical procedure can result in scar tissue due to the healing process. Back Surgery is no exception, and when the scar tissue presses on nerves or reduces the stability of the joint not only can the old problems return, but new ones can start. While this is common sense, it does not always clarify the cause of continued pain as well as physicians would like it to.
A patient having the same pain after the surgery as before should attribute that pain to the original issue rather than ‘scar tissue’. A patient that did well following surgery, then experienced a sudden increase in pain more than likely has re-herniated. Following a laminectomy if there is a gradual increase in pain 8-12 weeks post operative a case can be made that it is the result of scar tissue proliferating and putting increasing pressure on the nerves. The character, onset and intensity of the post operative pain can provide valuable clues to the cause.