Efficiencies in Imaging Diagnostics of the Lumbar Spine. (September 2014) - Wade, Chip
While low back pain is one of the most prevalent, if not the most prevalent reasons for visits to physicians, a majority of patients with low back pain cannot be given a definitive diagnosis. The current standard of care for function assessment of the lumbar spine focuses on uncontrolled patient directed motion which results in increased inter-patient variability and diagnostic misclassifications. The purpose of the current paper is to compare the measurement variability of lumbar spine motion when diagnosed using measurements of intervertebral motion taken from standard flexion extension bending radiographs (FE) between uncontrolled and controlled motion and to assess the rate of diagnostic misclassification errors (false positives and false negatives) in the detection of lumbar instability. 109 patients (57 asymptomatic, 52 symptomatic) were consented in the prospective investigation. The research was designed to compare studies involving FE to controlled motion bending radiographs (CCBR) using the Vertebral Motion Analysis (VMA) within the same patient. Measurement variability was determined by the mean and standard deviation of intervertebral rotation when evaluated by 9 independent observers evaluating each of the 109 patients FE and CCBR. The resulting standard deviation of the intervertebral rotation determinations was used as the measure of variability. Sensitivity (true positive rate) and specificity (true negative rate), were constructed using asymptomatic individuals and symptomatic patients in order to determine true positive (TP) and true negative (TN) appointments. The analysis was compared to known threshold of 25° (IVR) to determine the rates of false negatives (FN) and false positive (FP) rates. Sensitivity and specificity were calculated as TP/(TP/FN) and TN/(FP+TN), respectively. There was statistical greater measurement variability in intervertebral rotation in FE when compared to CCBR (both standing and lying). When comparing measurement variability between FE and CCBR, results indicate between a 26% to 46% decrease in measurement variability under CCBR compared to FE. These findings are consistent across asymptomatic and symptomatic patients. Sensitivity measures were 6.2% (VMA 12.6%, FE 6.4%) greater in the VMA test compared to the FE. Specificity measures were 8.4% (VMA 99.1%, FE 90.7%) greater in the VMA test compared to the FE. The current standard of care for functional testing of the lumbar spine utilizes uncontrolled FE with a manual data evaluation process. Recent developments in using computerized imaging processes has improved, however there remains variability in patient bending due to the self-selected rate and position of the bending. CCBR results in a significant reduction in measurement variability of intervertebral rotation measurements. Reducing measurement variability would be expected to improve the efficacy rates of surgeries indicated for these conditions.