Abstract
Introduction: Intradiscal electrothermal therapy (IDET) is a novel minimally invasive treatment for discogenic back pain. It involves inserting a catheter into discs which are suspected of being symptomatic in order to heat certain regions of the disc matrix and thereby influence the pain process. The clinical efficacy of IDET appears to be variable, and the scientific evidence suggests that the heating effect on disc tissues is very local to the catheter. We test the hypothesis that IDET can affect the internal mechanical functioning of lumbar intervertebral discs.
Methods: Eighteen cadaveric lumbar “motion segments” (aged 64–97 yrs) were used, 16 of which had degenerated intervertebral discs. Following incubation at 37°C, a miniature pressure transducer, side mounted in a 1.3mm diameter needle, was used to measure the distribution of compressive “stress” along the mid-sagittal diameter of each disc while it was compressed at 1.5 kN. Measurements were repeated in three simulated postures. IDET was then performed, using biplanar radiography to confirm placement of the heating element, and an independent thermocouple to measure temperature in the inner lateral annulus. Stress profilometry was repeated immediately after IDET.
Results: Peak temperatures in the inner lateral annulus during IDET averaged 40°C (STD 2.3°). Differences between stress measurements repeated before IDET never exceeded 8% (NS), and a sham IDET procedure produced no consistent changes. After IDET, pressure in the nucleus fell significantly by 6–13%, and stress peaks in the annulus were reduced (P< 0.008). In 12/18 specimens, annulus stress peaks were reduced by more than 8%, and in these “responders”, the mean reduction was 78%. Stress concentrations were increased by more than 8% in two specimens.
Conclusion: IDET has a significant but inconsistent affect on compressive stresses within intervertebral discs. These results may partly explain the variable clinical success of IDET.
The abstracts were prepared by Editorial Secretary, Dr Charles Pither. Correspondence should be addressed to SBPR at the Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PN
