Comparison of Daily Motion of the Cervical and Lumbar Spine to ASTM F2423-11 and ISO 18192-1.2011 Standard Testing

Background–The purpose of this investigation is to measure the normal neck and trunk motion of daily living and to compare this to annualized movements as defined by the ASTM F2423-11 and ISO 18192-1:2011 standards. Methods–Ten volunteers wore a custom sensor system that monitored their upper and lower spine motion. The system allows continuous measurement of the frequency and magnitude of spinal motion about all three axes. The angular motion can then be determined for the upper and lower spinal segments. The results were extrapolated to yield the yearly frequency and magnitudes of movements. The data were compared to ASTM and International Organization for Standardization (ISO) standards. Results–The median magnitude of neck motion was 14.3°, 13.8°, and 21.6°, and the mean annual frequency of cervical motion was 10.6 × 10⁶, 8.5 × 10⁶, and 5.6 × 10⁶ movements in flexion-extension, lateral bending, and axial rotation, respectively. The observed-to-standard (ASTM) ratio of annual cervical excursion was 1.22, 1.09, and 0.69, and for ISO the ratios were 1.22, 1.09, and 1.04 in flexion-extension, lateral bending, and axial rotation, respectively. The median range of motion for the thorax relative to the iliac crest (lumbar) was 11.2°, 10.3°, and 12.5°, and the estimated number of annual movements was 6.8 × 10⁶, 5.2 × 10⁶, and 3.8 × 10⁶ in flexion-extension, lateral bending, and rotation. The observed-to-standard ratios from ASTM were 0.63, 0.56 and 1.6, and for ISO they were 1.5, 1.68, and 1.59, in flexion-extension, lateral bending, and rotation respectively. Discussion–Neck and lumbar movements in healthy young adults aremore frequent that 1 × 10⁶ times per annum. The amplitude is smaller than specified in current standards. Overall, the total annual angular excursions specified by ASTM correlated well with results, whereas the ISO specified smaller ranges of motion for the lumbar spine, and therefore the observed angular motions were greater than specified. New testing standards should consider using more physiologic movement patterns.