Bo Nystrom, Adam Taube, Eliza Leja and Birgitta Schillberg
Background: In patients with chronic low back pain (CLBP) who undergo fusion surgery, selecting the level to fuse has been based on radiological findings, the pain reaction at discography, disc-block and temporal external fixation, tests all found to be unreliable. An alternative would be to rely on spatial discrimination. Our objective was therefore to test if healthy volunteers are able to discriminate between lumbar vertebrae bordering one another (adjacent) and those that are one or two vertebrae apart (separated).
Methods and findings: Eighteen volunteers participated in the study. Short injection needles were introduced into the top of the spinous processes of the L3, L4, L5 and S1 vertebrae. One vertebra was tapped in the pair being tested and immediately thereafter the other vertebra was tapped. The subject then had to decide whether the two tapped vertebrae were adjacent to one another or separated. Outcome was measured as the number of correctly specified pairs, out of the 12 alternatives, obtained for each test subject.
Results: For all 18 volunteers there were altogether 87 correct classifications among the adjacent pairs of vertebrae giving a mean of 0.805, 99% CI (0.69; 0.89) bootstrap. This was regarded as the sensitivity. In the same manner the number of 96 correctly classified separate pairs gives a specificity of 0.89, 99% CI (0.70; 0.95) bootstrap.
Conclusion: We found our test useful in discriminating deep structures of the spine lying only 2-3 cm apart. It might therefore be useful when searching for a possibly painful segment in patients with CLBP.