• Phill Pollintine, Gordon Findlay, and Michael A Adams.
• Department of Anatomy, University of Bristol, Bristol, United Kingdom.
• Spine. 2005 Mar 15; 30 (6): E134-9.

Study DesignMechanical testing of cadaveric motion segments.ObjectivesTo test the hypothesis that intradiscal electrothermal therapy (IDET) can affect the internal mechanical functioning of lumbar discs.Summary Of Background DataThe clinical efficacy of IDET is variable, and its mode of action uncertain.MethodsEighteen lumbar motion segments (64-97 years old) were incubated at 37 degrees C. A miniature pressure transducer, side mounted in a 1.3-mm diameter needle, was used to measure the distribution of compressive "stress" along the midsagittal diameter of each disc while it was compressed at 1.5 kN. Measurements were repeated in 3 simulated postures. Standard IDET was performed using biplanar radiography to confirm the placement of the heating element and an independent thermocouple to measure temperature in the inner lateral anulus. Stress profilometry was repeated immediately after IDET.ResultsPeak temperatures in the inner lateral anulus during IDET averaged 40.0 degrees C (standard deviation [STD] 2.3). Stress measurements repeated before IDET differed by less than 8%, and a sham IDET procedure produced no consistent changes. After IDET, pressure in the nucleus decreased by 6% to 13% (P < 0.05), and stress concentrations in the anulus were reduced by an average 0.28 MPa (P < 0.004). In 12 of the 18 specimens, anulus stress concentrations were reduced by more than 8%, and in these "responders," mean reduction was 78%. Stress concentrations were increased by more than 8% in 2 specimens.ConclusionsIDET has a significant but inconsistent effect on compressive stresses within intervertebral discs. These results may partly explain the variable clinical success of IDET.

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