Background and Objectives:

Knowledge of spine  segment motion patterns or “kinematics” is of interest to understanding  the time-dependent or viscoelastic behavior of the spine, postural  kinematics, vibration response of the spine, and response of the spine  to chiropractic manipulations. The ability to quantify in vivo spine  segment “kinematics” is clinically significant in terms of both the  diagnosis and treatment of spinal disorders and LBP. The objectives of  this study were to a) study the relative motions of the normal and  abnormal lumbar spine in response to transverse (postero-anterior)  manipulative thrusts, and b) mathematically model the dynamic  viscoelastic behavior of the spine.


An intervertebral motion measuring device (IMD) was  used to quantify the in vivo Interspinous kinematic behavior of the  normal (1 volunteer) and unstable (2 patients with abnormal lumbar discs  consulting for spine surgery) human lumbar spine. The IMD is a spatial  linkage system capable of measurement of motion in the sagittal plane,  and was rigidly attached to the L2-L3 and L3-L4 spinous processes using  2.4 mm Steinmann pins. Rotation, translation and shear of the lumbar  vertebrae were obtained in response to transverse impulses from an  Activator adjusting instrument (AAI) applied to the spinous process of  adjacent segments of the thoraco-lumbar spine with the patients lying  prone. Impulse force and acceleration in transverse plane were measured  using a uniaxial load cell and accelerometer.


The impulses (= 100N peak, < 100 msec duration)  produced exponentially damped oscillations in the lumbar motion segment  with displacement amplitude peaks (axial=0.5-1.0 mm, shear = 0.1-0.3 mm,  rotation=0.5-1 degrees) located at frequencies ranging from 10-15 Hz.  Alterations in the propagation of the impulse stimulus were observed in  the two patients with disc pathology. The kinematic data is currently  being analyzed using a dynamic, three-parameter linear solid  viscoelastic model to obtain intrinsic properties of the: ‘spine (moduli  or stiffness and viscosity).


Although this study was conducted using  only a few human subjects, the preliminary results suggest that one may  be able to discriminate between normal and abnormal kinematic behavior  by measuring and analyzing the impulse response. of the spine in viva.  Such measurements may be used to evaluate the mechanical effectiveness  of various manipulative, surgical and rehabilitative procedures of the  spine.

Reference: T. Keller, PhD, M. Nathan, MS, and A. Kaigle,  MS Dept. of Mechanical Engr. University of Vermont. Burlington, VT and  Depts. of Orthopedics (Occupational Unit), Sahlgren Hospital, Goteborg,  Sweden. Proceedings of the FCER’s 1993 International Conference on Spinal  Manipulation. Montreal, Quebec, Canada, April 30-May 1: pp. 51-5.