Interspinous spacers for lumbar foraminal stenosis: formal trials are justified

To determine whether preliminary evidence supports X-STOP implants as an effective treatment for lumbar radiculopathy secondary to foraminal stenosis, and if larger formal trials are warranted.

Participants had a clinical diagnosis of lumbar radiculopathy supported by MRI findings of foraminal stenosis and relevant nerve root compression. Self-reported disability and pain were measured pre-operation, early and late post-operation using the widely used Oswestry Disablity Index (ODI) and the bodily pain scale of the Medical Outcomes Study 36-item Short Form Health Survey (SF-36BP). The statistical significance (paired samples t test; Wilcoxon signed ranks test), and clinical significance (Cohen's effect size; Standardised response means) of change scores was determined.

Fifteen people had X-STOP implants. Data pre- early- and late post-operation were available for ten. Self-reported disability and pain improved substantially by the early post operative measurement. Mean change scores (ODI = 29; SF-36BP = -45), significant at the p < 0.05 but not significant at the p < 0.001, were very large and effect sizes exceeded notably criteria for large clinical improvements (>0.80). Improvements were maintained at 2-3 years. Both scales had floor and ceiling effects implying changes may be underestimated. There were no surgical complications.

In this small study, X-STOP appeared safe and effective. It is less invasive than other established surgical procedures, but does not jeopardise other options in the event of failure. Large scale clinical trials are justified but floor and ceiling effects suggest that the ODI and SF-36 may not be the best choice of outcome measures for those studies.