The feasibility of vibration as a tool to assess spinal integrity

As the majority of back pain is thought to be mechanical in origin, quantitative tests designed to assess spinal mechanics may provide information about its etiology and treatment. This paper describes the application of structural vibration testing in the spine, its reliability and ability to discriminate between different structural states. In each of five cadaveric pigs, tri-axial accelerometers were fixed to the spinouses of L1–5 and short-duration vibrations (0–2000 Hz) were applied to the L3 spinous exclusively. The frequency response function (FRF) of each sensor axis was calculated and the process repeated. Additional FRF data were obtained after the creation of multiple structural alterations including joining of adjacent vertebrae and scalpel transections of each lumbar disc. To assess the reliability of structural vibration testing, the intra-class correlation coefficient was calculated for FRFs obtained from each structural state in each specimen. To determine if structural vibration testing could distinguish between different structural states, correlation coefficients were calculated between FRFs from each structural state and a baseline condition. Most intra-class correlation coefficients (3740) were in the excellent range (>0.75), while FRF data from each structural state were found to be significantly different from that of the baseline state (p<0.05). These results indicate that structural vibration testing can be used to obtain reliable FRFs that are sensitive to alterations in the spine's structure. In the future, we hope to refine this technique to obtain specific diagnoses of, and/or assess therapies for, common spinal disorders.