Many patients who have persistent pain after back surgery often undergo additional surgeries within five years of the original surgery. However, success rates diminish after each additional surgery. The term failed back surgery syndrome has been used to describe continued or persistent pain after previous back surgeries. For many patients failed back surgery leads to a condition of severe pain and markedly diminished quality of life. After previous surgery, patients with persistent pain may feel hopeless and wonder if anything else can be done.
However, all is not lost because careful evaluation can often pinpoint the causes of persistent pain and new diagnostic and treatment strategies are now available for patients with failed back surgery syndrome.
We present here a framework for understanding some of the most common causes of persistent pain after previous spine surgery and highlight some recent management strategies. We introduce nine types of problems as a useful guide in understanding the most common causes of failed back surgery syndrome.
- Problems due to surgery that was performed for the wrong reason or diagnosis or that did not adequately address all levels of pathology.
These problems are characterized by the fact that some or all of the pain generators or pathology remain unaddressed. This can usually be accurately diagnosed by reviewing all imaging and medical records before and after previous surgeries. If it becomes clear this the reason for persistent pain, then the correct surgical treatment may be prescribed taking into account the history of the previous surgery.
- Problems resulting from recurrent diagnoses or problems related to the previous surgery at the same level e.g. recurrent disc herniation, recurrent nerve compression.
For example, up to 15 percent of patients who undergo microdiscectomy for disc herniation may require surgery for recurrent disc herniation. Problems may occur even though the correct diagnosis was made the first time around and surgery was properly done.
- Issues relate to problems after spinal fusion.
Many types of spinal pathology require spinal fusion and instrumentation. There are some risks associated with placement of spinal instrumentation such as malposition, loosening or migration of the instrumentation.
A small number of patients may have allergy to the metal in the instrumentation. Well known problems after spinal fusion include failure of the bone healing, a condition called pseudarthrosis. Pseudarthrosis may lead to spinal instability with broken screws, rods, or vertebral fractures.
It is important when evaluating pseudarthrosis problems to identify and correct risk factors e.g. osteoporosis, diabetes, smoking, prolonged steroid use that affect bone thickness, strength and bone healing.
Fusion immobilizes the spinal segments fused and therefore increases stress. Increased stress and motion at the adjacent levels may cause bone spurs and ligamentous hypertrophy with spinal canal narrowing and nerve above or below the level of fusion called adjacent segment disease.
Symptomatic adjacent segment disease is one of the most common reasons for repeat spine surgery years after the original surgery. Problems such as adjacent segment stenosis, pseudarthrosis, broken screws etc. are readily diagnosed using standard imaging-such as X-rays and MRI. In patients who have had instrumentation often special tests such as CT myelogram which involves injection of dye into the spinal canal prior to CT scan may be required.
- Problems result from problems with the spinal alignment after surgery.
Alignment problems may take the form of scoliosis (abnormal curvature of the spine), kyphosis (abnormal forward bending or angulation of the spine). The term flat back syndrome is used when the lumbar spine (lower back) loses its normal curvature leading to straightening of the spine and an abnormal relationship between the spine and pelvis called spinopelvic imbalance. Normal spinopelvic balance parameters have become clear only in the last five years or so. Many spine surgeries performed more than five years ago paid inadequate attention to maintaining or restoring normal spinopelvic parameters. It is now clear that careful assessment of spinopelvic parameters specific for a patients age is important in the evaluation of patients with failed back surgery syndrome. The right amount of lumbar spine curvature must be calculated for each type of pelvic parameters. If the patient is not in spinopelvic balance the exact amount of lumbar curvature must be introduced intraoperatively to correct the imbalance. Failure to do will result in persistent pain or progressive imbalance and need for further surgery.
- Problems relate to spinal instability between vertebrae and abnormal or excessive movement of the vertebrae on flexion and extension X-rays.
This condition called spondylolisthesis can be present on standard X-rays or a MRI but often are only evident on upright flexion (forward bending) and extension (backward bending) X-rays of the spine are obtained. Spondylolisthesis after previous surgery may be caused by excessive bone removal and/or incompetency of the residual facet joints. It may also be caused by failure to recognize milder instability preoperatively (as in not checking flexion/extension films before surgery). It is important to identify patients at risk for instability such as patients who had extensive bone spurs and undergo excessive bony decompression.
- Problems occur when there is persistent compression in the lateral gutters of the spine, in the foraminal or extraforaminal areas of the spine-these areas are often difficult to reach and decompress using traditional approaches.
New surgical techniques such as endoscopic decompression with foraminoplasty (removal of bone spurs around the nerve canal) may be the best way to decompress these harder to reach bone spurs that remain after central canal spinal decompression but not all surgeons are trained in these techniques and may be helpful to consult a revision spine surgeon who specializes in these techniques.
- Refers to pain in the SI joints after fusion.
The SI joint pain has been noted to be present in up to 40 percent of patients with persistent pain after spinal fusion. The SI joint is the joint between the sacral spine and the ilium bones of the pelvis. There is one joint on each side. SI joint pain can be missed if there is not a high clinical index of suspicion to check for it. SI joint pain diagnosis involves use of confirmatory maneuvers that elicit SI joint pain and use of diagnostic injection of anesthetic into the joint. The diagnosis is confirmed if the anesthetic injection reduces pain by 75 percent or more. Treatment of SI joint pain includes specialized physical therapy to improve joint alignment; adjunctive such as SI joint belt can be helpful. In severely refractory cases a new minimally invasive one hour SI joint fusion procedure was recently approved by the FDA and can be helpful in patients with intractable SI joint pain. Consultation with a surgeon trained in this new surgical approach is necessary for patients who have this type of problem.
- Problems describe subset of patients for whom there are no clear imaging or other explanation for pain-no clear SI joint problems, adjacent segment problems, spondylolisthesis, severe compressive discs or bone spurs or spinal alignment or spinopelvic imbalance.
This is one of the most difficult to treat and differs from previous group due to lack of clear radiological correlates of pain—imaging may show scarring, sometimes, arachnoiditis or clumping of nerve roots due to previous surgeries with or without multiple degenerative discs-this group often have a different type of pain called neuropathic pain that is more constant, burning in nature may or may not affect the legs-For this group, recent studies suggest that additional another fusion or decompression of scarred areas are futile. Instead, spinal cord stimulation may be best option-Recent technological advantages in stimulator design and stimulation paradigms have resulted in significant success in treating many patients with this type of problem.
- Problem describes patients with combination of above types-this is the most challenging problem to treat and really needs consultation with an expert revision spine surgeon to assess which problems are primary factors and which are secondary and compensatory and the right sequence of diagnostic or treatment strategies.
Let’s say the patient underwent fusion for spondylolisthesis and comes back with persistent pain a year later. Imaging shows adjacent level stenosis at level above and lateral extraforaminal stenosis at same level single level and physical exam is positive for SI joint pain. If the patient undergoes additional decompression with extension of fusion to adjacent level it is unlikely to be successful because there are other important aspects of the problems that remain unaddressed: This patient in fact has a type 9 problem: in addition to having a type 3 problem (adjacent segment disease) the patient also also had a type 6 (extraforaminal compression) and type 7 (SI joint) problem and did not undergo any evaluation for a type 4 (spino pelvic alignment). It is easy to see why a patient such as this may end requiring multiple spine surgeries if not properly evaluated.
We have reviewed above nine of the most common reasons for persistent pain after a previous spine surgery, and some patients may have a combination of these problems. An experienced spine surgeon who specializes in revision spine surgery can often sort through these problem types to design effective strategies.
While a cure is not possible in many instances, the appropriate treatment can significantly alleviate pain and suffering, and improve quality of life for the long-term. It is important however also to realize that medical conditions such as depression, obesity, anxiety may impact the severity and perception of back pain and response to treatment so it is best to have persistent pain evaluated in a multidisciplinary team that includes potential treatment of any accompanying conditions that exacerbate back pain.
Don’t lose hope
There is hope for a number of patients suffering from persistent pain despite previous back surgeries. A consultation with an experienced spine team who specializes in revision spinal surgery is necessary. It is important to gather and obtain previous preoperative imaging, medical records and operative reports and all postoperative imaging prior to consultation.
The evaluation should include a review of these records, new imaging to assess for compressive pathology, spondylolisthesis, spinal alignment, stability, spino-pelvic balance and pain generators such as SI joints should be ruled out. Particular attention should be placed on any residual compression in the lateral recess, foraminal and extraforaminal compartments of the spine. Newer spinal cord stimulation technologies and stimulation paradigms increasing able to significantly improve pain in the most intractable circumstances.