A Prospective Randomized Controlled study of VAX-D and TENS for the
Treatment of Chronic Low Back Pain
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No patients were withdrawn by the investigator. Patients 018 and 034 both randomised to VAX-D, did not comply with the study criteria and are therefore excluded from the efficacy-evaluable population. They both had a baseline VAS score less than 2 but this error of inclusion was not picked up until the completion of the trial. The efficacy-evaluable population therefore comprised of 40 patients: 19 patients randomised to VAX-D, 21 randomised to TENS.

Table 1: Demographic data

In the efficacy-evaluable population the proportion of successfully treated patients was 13 out of 19 patients (68.4%) for the VAX-D treatment group compared to zero out of 21 (0%) for the TENS treatment group. There was a high statistically significant treatment group comparison p-value of <0.001. The 95% confidence interval for the difference in proportions of successfully treated patients, comparing VAX-D with TENS was 47.5% to 89.3%.

In the VAX-D group all patients recorded some improvement in their pain levels whereas in the TENS group 13/ 21 recorded an increase in pain.

At six-month follow-up, of the 13 successful cases, 2 have been lost to follow-up, 1 case suffered a significant other injury and of the remaining 10, seven have shown sustained success (ie. they still meet the criteria for successful outcome).

The results reported for the TENS group were less that that expected for a placebo control. The negative outcomes may have been due to the fact that the TENS patients (and the VAX-D patients) had to travel to and attend a medical clinic five days per week for four weeks, and one day per week for four weeks. This fact that both treatment groups had to travel to, and attend the clinic, was necessary to ensure that the only variable between the two groups was in the type of treatment that they received. The benefits of treatment in the VAX-D group clearly outweighed the negative effects of travelling, which became evident in the placebo group.

DISCUSSION

Disc stresses coupled with ongoing increased intradiscal pressures from mechanical loading may lead to failures in the normal biomechanics of the disc and progress to degeneration, posterior displacement of the nuclear material, annular disruptions and herniations. Other causative factors in the course of disc degeneration are negative diffusion gradients, reduction of the fluid content of the nucleus pulposus, and abnormal disc metabolism. With positive disc pressures throughout the day that are above diastolic pressure, the metabolism of the disc becomes anaerobic thus impeding the normal reparative healing abilities.

Proteolytic enzymes (matrix metalloproteinases) reside in the disc and have been implicated in disc degeneration. (15) The matrix metalloproteinases are regulated by specific inhibitors (TIMPS), cytokines (Interleukin-1) and growth factors. (16) Spinal loading may interfere with diffusion into the disc by reducing the gradient across the vertebral endplate. As disc metabolism becomes anaerobic, there is an accumulation of lactic acid, fall in pH, loss of chondrocyte and fibroblast function, and activation of the metalloproteinases.

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