Abstract
Background: Intervertebral motion is often assumed to be altered with back pain, however, the patterns are inaccessible to measurement in live subjects. A method for digitally tracking and analysing fluoroscopic images of the vertebrae of subjects who are undergoing standardised passive motion has recently been brought into clinical use for the assessment of surgical fusions. We have studied the differences between the behaviour of spinal linkages in subjects who are asymptomatic, and those who have had fusion operations. This paper describes the reliability, ranges and qualitative features of intervertebral motion patterns in 27 asymptomatic subjects and 3 fusion patients.
Methods and results: Thirty asymptomatic male volunteer subjects aged 19–40, underwent 2 –20 second sessions of fluoroscopic screening during 80 degrees of lumbar spine bending within 20 minutes of each other. Intervertebral sidebending motion from L2–5 was measured in 27 subjects whose images were judged suitable for tracking. Approximately 120 digitised images throughout each motion sequence were analysed 5 times by 2 blinded observers for intervertebral range and each result averaged. The intra-subject biological error (RMS), for range of intervertebral motion was 2.75° for Observer1 and 2.91° for Observer 2. The interobserver error for tracking the same screenings was 1.86° (RMS). At almost all levels, these motion patterns were remarkably regular.
Four male patients aged 33, 44, 45 and 52 years, who had undergone different spinal stabilisation procedures consisting of flexible stabilisation (DNESYS), posterior instrumented fusion, and anterior interbody fusion with facet fixation were investigated. Images were acquired and analysed in the same way except that a larger number of images (500 per screening) was utilised in each case. Four operated levels and 2 adjacent levels were analysed. All motion patterns were easily distinguishable from those of the normal subjects. The PLIF and DYNESYS stabilisations demonstrated no motion at the instrumented levels. The anterior inter-body fusion-transfacet fixation patient was shown to have developed a pseudarthrosis.
Conclusions: Detailed lumbar intervertebral bending patterns in asymptomatic subjects were distinguishable from the fused and adjacent-to fused segments in operated patients. Results suggest that there is sufficient reliability in the method to evaluate lumbar intersegmental ranges and motion patterns for fusion assessment.
The abstracts were prepared by Editorial Secretary, Dr Charles Pither. Correspondence should be addressed to SBPR at the Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PN
