A comprehensive knowledge of the spinal kinematics is important for the understanding of the clinical analysis and management of spinal problems. Measurement of the range of spinal motion is valuable for evaluation of disability and therapeutic effect associated with spinal disorders. But it is difficult to measure precisely the range of spinal mot ion which is complex as a functional spinal unit.

The purposes of this study were to measure the range of spinal motion using 2-dimensional motion analysis system and to identify clinical applicability of this method compared to that of spinal motion using inclinometer.

Ten healthy males volunteered for this study(mean age 22.5 years, range 20-32 years).

We measured the range of spinal motions in flexion, extension, lateral flexion and rotation using two methods of electrodigital inclinometer(EDI 320) and 2-dimensional motion analysis system. And we also measured the range of segmental motions in thoracic, lumbar spines and hip joint, and calculated the proportions of the range of segmental motions to gross motions.

The results were as follows:

1) In the method of 2 dimensional motion analysis system, the average range of motion of flexion was 26.2±4.7° in thoracic segment, 50.8±5.3° in lumbar segment, and 63.5±10.4° in hip joint, respectively. The range of motion of extension was 13.9±3.3° in thoracic segment, 26.7±5.8° in lumbar segment, and 4.1±1.5° in hip joint, respectively. The range of motion of lateral flexion was 31.7±4.4° in thoracic segment, and 14.2±2.8° in lumbar segment, respectively. The range of motion of rotation was 37.7±3.8° in thoracic segment, and 11.4±1.8 in lumbar segment, respectively.

2) The proportions of each segmental range of motion to gross motion were thoracic 19%, lumbar 36%, hip 45% in flexion, and thoracic 32%, lumbar 59%, hip 9% in extension, and thoracic 69%, lumbar 31% in lateral flexion, and thoracic 77%, lumbar 23% in rotation.

3) There was no statistically significant difference between electrodigital inclinometer and 2-dimensional motion analysis system in flexion, lateral flexion and rotaion. But in 2-dimensional motion analysis system, the average range of motions of hip extension and gross extension were significantly less than those in electrodigital inclinometer.

We concluded that 2-dimensional motion analysis system as well as electrodigital inclinometer were highly applicable for measurement of the range of spinal motion in clinical setting.