Pressure-controlled lumbar discography in volunteers without low back symptoms

Abstract

Background. For lack of a criterion standard for lumbar discogenic pain, the validity of lumbar discography cannot be determined directly. The false-positive rate of discography, however, can be inferred from the prevalence of positive responses in asymptomatic volunteers. Responses in normal volunteers have been reported in only three studies, and the prevalence of positive responses has been "occasionally, zero, and 10%." None of these studies, however, controlled for both pressure of injection and intensity of response. Purpose. To determine the prevalence of positive responses to lumbar discography in asymptomatic volunteers, controlled for pressure of injection and intensity of response. Stidy Design/Setting. Prospective, observational study, conducted in a private spine center. Patient Sample. Four lay persons and nine physicians underwent lumbar discography, with manometry. Outcome Measures. The prevalence of painful responses were tabulated in terms of the intensity of response, the pressure of injection, the segment stimulated, disc morphology, and past history of low back pain. Results. Some 56% of discs were not painful, despite maximum pressurization. The remaining 44% of discs were painful, to various degrees, at various pressures. Most discs required high pressures of injection to be painful but even so, were only mildly painful. A receiver-operator curve was derived to demonstrate combinations of pain intensity and pressure below which the probability of a response was zero or less than 10%. Conclusions. Lumbar discs in asymptomatic volunteers can be made painful, but as a rule, the pain is mild and requires high pressures of injection. If attention is paid to pressure of injection and intensity of response, operational criteria can be defined that provide lumbar discography with a potential false-positive rate of zero or less than 10%.