Abstract
Introduction: Intradiscal electrothermal therapy (IDET) is a novel treatment for discogenic back pain. A heating element is inserted percutaneously into a disc in order to denature the collagen of the posterior annulus. Clinical success is claimed, although laboratory studies indicate that temperature increases may be insufficient to cause widespread collagen denaturation, or denervation, and that IDET has little effect on gross mechanical properties. We report on changes in internal disc mechanics following IDET.
Methods: Ten cadaveric lumbar ‘motion segments’ (aged 72–79 yrs) were stored at −17°C. Subsequently, each was equilibrated at 37°C. A miniature pressure transducer was used to measure the distribution of compressive stress along the mid-sagittal diameter of each disc while it was compressed at 1.5kN. IDET was performed, using bi-planar radiography to confirm placement of the heating element, and an independent thermocouple to measure temperature in the inner lateral annulus. Stress profilometry was repeated irnmediately after IDET.
Results: Before IDET, all discs exhibited stress concentrations typical of mild degeneration. Accurate placement of the element was confirmed in all discs. Temperatures in the inner lateral annulus during IDET reached only 40.9°C (STD 2.3°C). Differences between stress measurements repeated before IDET never exceeded 8% (NS). After IDET, peak stresses (above nucleus pressure) were reduced by more than 8% in 6/10 specimens (mean reduction 55%), increased in 2/10, and were unchanged in 2/10. Nucleus pressure fell by 13% (n=10 0, P=0.05).
Discussion: IDET had a variable effect on these 10 degenerated discs. In six of them, stress concentrations in the annulus were reduced, suggesting that IDET can cause disc material to resist compression in a more coherent fashion, possibly by ‘bonding’ fragmented tissue together, and thereby distributing load more evenly across the endplate. Reduction in nucleus pressure following IDET suggests load transfer to the neural arch, although this could not be confirmed. Reducing annulus stress concentrations could conceivably reduce pain in some individuals.
Abstracts prepared by Mr. A. J. Stirling, FRCS, and Miss A. Weaver. Correspondence should be addressed to Miss A. Weaver at the Research and Teaching Centre, Royal Orthopaedic Hospital, Northfield, Birmingham, B31 2AP, UK
BritSpine 2002, the second combined meeting of the British Association of Spinal Surgeons, the British Cervical Spine Society, The British Scoliosis Society and the Society for Back Pain Research, took place at the International Convention Centre in Birmingham UK between 27th February and 1st March 2002. The following presentations and posters were given and displayed.
