Quantitative discomanometry is a technique which might have predictive value for discogenic pain evaluation. Alexis Kelekis and Dimitrios Filippiadis, Greece, have carried out a study which finds that it might serve as useful tool for patient selection in choosing the appropriate percutaneous therapy. Spinal News International finds out more…
What is quantitative discomanometry—why is it important?
Filippiadis: Provocative discography seems to be the only diagnostic test used for the evaluation of discogenic pain that directly correlates the internal morphology of the disc (with or without derangement) to the patient’s usual painful symptom. Quantitative discomanometry is a variant of this technique. Under fluoroscopy the intervertebral disc of interest is punctured as in discography. Once inside the disc by means of the discmonitor, a mixture of contrast medium and normal saline is injected at a constant rate. At the same time, intradiscal pressure and volume measurements are performed in order to create a pressure-volume curve.
Kelekis: With quantitative discomanometry we try to correlate the disc’s morphology to patient’s painful stimulus. Furthermore, the pressure and volume measurements provide us with very important information. Thus, we are able to quantify pressure and volume measurements and try to correlate them to the imaging aspect of the intervertebral disc-vertebral endplate complex. These biomechanical parameters may help significantly the proper patient selection for any kind of intervertebral disc therapies (minimally invasive or surgical ones).
What was the background and rationale for your study?
Filippiadis: Our purpose was to illustrate the diagnostic efficacy as well as the predictive character of quantitative discomanometry concerning the evaluation of discogenic pain.
During the last three years, we have enroled 36 symptomatic patients suffering from intervertebral disc hernias. These patients underwent percutaneous quantitative discomanometry just prior to a percutaneous intervertebral disc (ablative or decompressive) therapeutic technique. During discomanometry, we recorded the disc’s initial pressure (i.e. pressure required for the first drop of mixture to be fluoroscopically seen inside the disc), the pressure at maximum pain, and the injected volume. Post the disc’s therapy we evaluated patients’ pain reduction by clinical evaluation and by means of NVS questionnaires at three, 12 and 24 months. We searched for bilateral statistical significance during the correlation of intradiscal pressure (Po, Pmax and Pmax-Po cutoff values) and injected volume obtained via discomanometry to various significant (>4NVS units) pain reduction cutoff points achieved by means of percutaneous disc techniques.
What does your study show?
Kelekis: We were able to show correlation between quantitative discomanometry results and the treatment. To be more specific we were able to associate specific pressure and volume thresholds to the end result of the treatment. Patients with positive pain response of under 65psi (47psi pressure difference) and/or under 2.4ml of injected volume, were the ones who responded best to percutaneous treatments in a statistically significant way.
What are some of the limitations of the study?
Filippiadis: The small number of patients included in our study is one major limitation. In order to achieve a negative or positive predictive value with corresponding Receiver Operating Curves, an increase in the number of patients is necessary. Another limitation is the fact that only pathologic intervertebral discs were included in our study. However, do not forget that this kind of disc is usually symptomatic and requires therapy. In any case, the presence of a control group consisting of healthy volunteers and the comparison of the intradiscal pressure measurements would provide a very interesting substrate.
Based on the results of your study, what do you recommend to other spine specialists?
Kelekis: Quantitative discomanometry does not replace imaging studies. It is a useful tool in ambiguous cases, where standard MRI cannot clearly correlate imaging to symptoms. It somewhat bridges the gap between imaging morphology and actual disc response to stimulus. Moreover it can provide us with specific, repeatable measurements and volume/pressure relations. Interestingly, it seems to be a statistical significant correlation between the results of quantitative discomanometry and clinical effectiveness of percutaneous treatment, thus helping patient selection for percutaneous treatments. Whether there is a predictive value is still to be determined in future investigations.