Spinal Cord Stimulation for Failed Back Surgery Syndrome -- Patient Selection Considerations.

BACKGROUND: Failed back surgery syndrome (FBSS) refers to the condition where persistent pain is experienced by patients following back surgery. This condition is historically difficult to treat. Spinal cord stimulation (SCS) and its recent technical advances have opened the door to a promising treatment option for FBSS. However, critical appraisal of supporting and refuting data is necessary to identify the best patient population for this treatment modality.
METHODS: In this systematic review, we review randomized controlled studies and cohort studies with matched controls to synthesize the data on the overall efficacy of spinal cord stimulation for FBSS. We further identify available data on outcome measurements based on working status, psychological status, smoking, sex, and race to provide insight on patient selection and identify needs for further research.
RESULTS: The literature search identified 34 publications, of which 23 were excluded due to duplication and inclusion/ exclusion criteria, yielding a total of 11 publications for review. Seven out of eleven studies reviewed had sources of potential funding or affiliation bias. Three out of 4 studies with radiating leg pain relief as their primary outcome showed statistically significant improvement with SCS treatment, while 2 out of 5 studies with mixed radiating leg pain and axial back pain as the primary outcome showed statistically significant improvement with SCS. All randomized controlled trials that included functional status and quality of life outcome measures showed improvement after SCS, though scales utilized in each study varied. Six studies included work status as a patient descriptor with only three reporting inclusion of workers' compensation patients. There was limited data on the effect of psychological status, smoking, sex or race on SCS outcomes based on the studies reviewed.
CONCLUSIONS: Evidence for the efficacy of SCS in FBSS is accumulating, with most studies demonstrating its efficacy especially for those patients with leg pain as the predominant symptom. However, a significant weakness in the current data includes potential bias based on the funding source for most studies. Additionally, it is clear that SCS provides short-term benefit, yet there is no solid evidence that SCS provides any benefit beyond two years of implantation. Another major concern is the significant placebo effect, which makes the true therapeutic response difficult to judge. Further, it is increasingly important to focus future studies on refining patient populations to those that may best respond to both SCS therapy in general, as well as specific stimulation techniques.