Can quantitative sensory tests predict failed back surgery?: A prospective cohort study.

Background: Failed back surgery syndrome (FBSS) is a pain condition refractory to therapy, and is characterised by persistent low back pain after spinal surgery. FBSS is associated with severe disability, low quality of life and high unemployment. We are currently unable to identify patients who are at risk of developing FBSS. Patients with chronic low back pain may display signs of central hypersensitivity as assessed by quantitative sensory tests (QST). This can contribute to the risk of developing persistent pain after surgery.

Objective: We tested the hypothesis that central hypersensitivity as assessed by QST predicts FBSS.

Design: Prospective cohort study.

Setting: Three tertiary care centres.

Patients: 141 patients scheduled for up to three segment spinal surgery for chronic low back pain (defined as at least 3 on a numerical rating scale on most days during the week and with a minimum duration of 3 months) due to degenerative changes.

Outcomes: We defined FBSS as persistent pain, persistent disability or a composite outcome defined as either persistent pain or disability. The primary outcome was persistent pain 12 months after surgery. We applied 14 QST using electrical, pressure and temperature stimulation to predict FBSS and assessed the association of QST with FBSS in multivariable analyses adjusted for sociodemographic, psychological and clinical and surgery-related characteristics.

Results: None of the investigated 14 QST predicted FBSS, with 95% confidence intervals of crude and adjusted associations of all QST including one as a measure of no association. Results remained robust in all sensitivity and secondary analyses.

Conclusion: The study indicates that assessment of altered central pain processing using current QST is unlikely to identify patients at risk of FBSS and is therefore unlikely to inform clinical decisions.