A DATABASE FOR ESTIMATING NORMAL SPINAL MOTION DERIVED FROM NONINVASIVE MEASUREMENTS

Study Design. A database for estimated normal spinal motion was derived using a noninvasive, high-resolution, computer-aided system, which tracks the motion of skin markers strategically placed on the spine. Forty normal subjects, selected from hundreds of possible subjects according to rigorous inclusion/exclusion criteria, were tested on the system. Objectives. Patterns of estimated spinal motion were analyzed as a function of load, age, and sex, confirming a correlation between the movement of spinal segments and the motion of skin markers. Summary of Background Data. The Workers Compensation Board of Quebec funded and supervised the experiments necessary to establish a normative reference database for a high-resolution motion analysis system that permits a noninvasive assessment of spinal function. A previous study examined the correlation between the movements of the skin markers and the underlying bony structures for trunk flexion. Skin movement cannot be random and contains information characterizing both the spine and its surrounding soft tissues. Methods. A noninvasive dynamic imaging system was used to measure normal spinal function under free movement. A high-resolution three-dimensional camera system collected basic kinematic data from strategically placed skin markers over the lumbar spine while the activity of paraspinal muscles was being recorded with surface electromyography. The measurements were analyzed for consistent, specific patterns recognizable as normal lumbar spine skin motion and reflecting normal lumbar spine function. A comparison was made with previous radiographic studies to confirm the correlation between the motion of skin markers and lumbar spine function. Results. Lumbar skin marker motion patterns in normal subjects were consistent and varied little with load; gender had no effect except in the initial phase of a movement. There was less mobility but similar coordination in alder subjects. No inconsistencies with previous radiologic investigations were found for sagittal and lateral plane movement. Conclusions. Consistent patterns were found and measurements compare favorably with previous radiographic data. Results show that it is possible to estimate spinal function from the data collected from the motion of skin markers.