To date, the diagnosis of whiplash injuries has been very difficult and largely based on subjective, clinical assessment. The work by Winters and Peles Multiple Muscle Systems–Biomechanics and Movement Organization. Springer, New York (1990) suggests that the use of finite helical axes (FHAs) in the neck may provide an objective assessment tool for neck mobility. Thus, the position of FHA describing head-trunk motion may allow discrimination between normal and pathological cases such as decreased mobility in particular cervical joints. For noisy, unsmoothed data, the FHAs must be taken over rather than large angular intervals if the FHAs are to be reconstructed with sufficient accuracy; in the Winters and Peles study, these intervals were approximately 10 degrees.
In order to study the movements’ microstructure, the present investigation uses instantaneous helical axes (IHAs) estimated from low-pass smoothed video data. Here, the small-step noise sensitivity of the FHA no longer applies, and proper low-pass filtering allows estimation of the IHA even small rotation velocity omega of the moving neck. For marker clusters mounted on the head and trunk, technical system validation showed that the IHAs direction dispersions were on the order of one degree, while their position dispersions were on the order of 1 mm, for low-pass cut-off frequencies of a few Hz (the dispersions were calculated from omega-weighted errors, in order to account for the adverse effects of vanishing omega).
Various simple, planar models relating the instantaneous, 2-D centre of rotation with the geometry and kinematics of a multi-joint neck model are derived, in order to gauge the utility of the FHA and IHA approaches.
Some preliminary results on asymptomatic and pathological subjects are provided, in terms of the ‘ruled surface’ formed by sampled IHAs and of their piercing points through the mid-sagittal plane during a prescribed flexion-extension movement of the neck.
J Biomechanics. 1994; 27(12):1415-32.
Author information: Woltring HJ, Long K, Osterbauer PJ, Fuhr AW. Whiplash Analysis, Inc. Phoenix, AZ.
BACKGROUND AND OBJECTIVE
The prone comparison of changes in leg alignment is commonly used to identify musculoskeletal dysfunction by chiropractors. Despite its widespread use as a diagnostic tool, confusion exists about the reliability of these measures. A possible problem is this methods dependence upon the clinician to accurately assess leg length asymmetries by visual inspection. The purpose of this investigation was to utilize a precise optoelectric device to determine 1) Leg length asymmetries prior to and after a random series of isolation tests, and 2) Heel trajectories during the performance of these isolation tests.
-Four subjects were tested in the Motor Control Laboratory at ASU. During each testing Session the subjects lay prone on a portable adjusting table with infrared light emitting diodes affixed with adhesive to their posterior heels, and posterior occiput. Additional markers were placed on a moveable reference bar placed near the subject’s feet. The reference bar was aligned to be perpendicular to the body, and was independent of the adjusting table. Prior to any data ‘Collection, each patient was assessed visually by a chiropractor for the incidence of any leg length inequality, which was recorded for later use. After the visual assessment, the reference bar was placed at its permanent location, and a second leg length measurement was made by a second investigator by measuring marker location of each heel from the bar with a scale marked in millimeters. Each measurement (visual and from the bar) were kept blind from the other respective investigator. Data collection then proceeded with the optoelectric device. Data were collected for 8 seconds at 50 Hz during the following conditions: no movement, head-up, chin-tuck, pressure test right transverse process of C-1, or pressure test left transverse process of C-1, The initial 5 trials were in the order mentioned in the prior sentence; 5 trials of each condition were then collected in a randomized order for a total of 30 trials. After all data were collected, leg length assessments were carried out by the two investigators as was completed prior to data collection. After data collection was complete, digital data were filtered at 2 Hz and 0′ rotated mathematically into a local reference frame within which the bar represented one axis in a 3-D frame. This allowed measurements to be examined along an axis perpendicular to the bar, the expected axis of lengthening or shortening of each leg. Two types of analyses were completed for each subject. Leg length difference analysis consisted of examining the heel positions at the; beginning and end of the entire testing session and comparing the data to the investigator’s manually measured reports.
Reference: John K. DeWitt, B.Sc.E., Paul J. Osterbauer. D.C., George E. Stelmach, Ed.D. & Arlan W. Fuhr. D.C.; Optoelectric Measurement of Leg Length Inequalities Before, During, and After Isolation Tests; Proceedings of the 1994 International Conference on Spinal Manipulation. Palm Spring, CA, June 10-11, 1994, p. 24-25.
Exercise and Sport Research Institute, Arizona State University Tempe, AZ 85287-0404 +Activator Methods. Inc. 3714 E. Indian School Road, Phoenix. AZ.
Activator Methods Chiropractic Technique (AMCT) was developed by Warren Lee, DC and Arlan Fuhr, DC. In the evolution of AMCT, Lee and Fuhr drew on elements of several other techniques, including Logan Basic, Van Rumpt, Truscott and Derefield, and developed innovation equipment, such as the Activator adjusting instrument (AAI) and an adjusting table designed specifically for AMCT. Based on oral history interviews, this paper records the early lives of Lee and Fuhr, their entries into chiropractic, influences on their personalities, the development of their technique and the seminars which presented it to the chiropractic profession.
Chiropr J Aust. Mar 1994 (Mar); 24(1): pp.28-32.
Author information: Richards DM.
The purpose of this study was to investigate the relation between preload and peak forces during Spinal Manipulative Therapy (SMT). Forces during clinical trials of SMT were measured on the sacroiliac joint, the thoracic spine, and the cervical spine using a thin, flexible pressure pad (EMED Inc.). Preload forces were found to correlate well with peak forces during SMT, suggesting that the force required to move the joint of interest to the end range of passive motion (i.e., the preload force required) influences the magnitude of the treatment thrust. Furthermore, the change in force from preload to peak (∆F) also correlated well with peak thrusting forces for all SMTs tested, suggesting that the stiffness of the joint of interest at the limit of passive range of motion may be related to peak thrusting forces. Preload and corresponding (∆F) forces were not correlated highly.
Journal of the Neuromusculoskeletal System. 1993; 1(2): 52-8.
Author information: Herzog W, Kawchuk GN, Conway PJ. Human Performance Laboratory, Faculty of Physical Education, The University of Calgary, Calgary, Alberta, Canada.
Changes in apparent leg length”(leg retraction) have been used by many as a means of locating subluxation in various Joints. The leg assessment is based on the assumption that unequal muscular contraction (e.g. hyper irritable muscles) about the spine and pelvis have the ability to retract one leg relative to the other. Despite Claims of usefulness, many problems are inherent in the prone leg assessment such as: a) measurement error; b) subject positioning by the examiner (expectancy bias) and; c) interference with die surface of the examining table. There have been prior attempts to quantify the amount of leg length changes that occur during a treatment session, but most have suffered due to the lack of a measurement technique which provides the necessary accuracy in the recording of slight changes in heel position. The purpose of this study was to quantify involuntary, movements that result from neck flexion and extension maneuvers. Five subjects exhibiting involuntary leg reactions were tested using an optoelectric motion analysis system. During each testing session, the subject lay prone on an adjusting table while infrared light emitting diodes (IREDs) were affixed to the heels of fracture boots. In the rest position, the neck was in neutral flexion so the face rested on the surface of the table. Prior to testing, the examination area was in neutral flexion so the face rested on the surface of the table. Prior to testing, the examination area was calibrated resulting in RMS errors of less than 0.3 mm. Data were collected for ten seconds by three cameras positioned to record movement of the IREDs. During each testing session, each subject preformed two movements; a head-up movement, during which the subject extended the neck and then returned to a resting position, and a chin-tuck movement, in which the subject flexed the neck and then returned to a resting position. A testing session consisted of three no-movement baseline trials, followed by three head-up trials and three chin-tuck trials. Examination of output displacement histories showed that during all trials, movement occurred at the heels in the direction of the subject’s longitudinal axis. During the head-up trials, a majority of cases showed a net shortening in heel position during head movement.
Reference: John K. Dewitt. B.Sc.E, Paul J. Osterbauer, D.C., George E. Stelmach, Ed.D., & Arlan W. Fuhr. D.C.; Optoelectric Measurement of Leg Length Changes During Isolation Tests; Proceedings of the CCR’s 8th Annual Conference on Chiropractic Science in Health Policy and Research, Monterey, CA, June 18-20, 1993, pp. 156-7.
Affiliation: Arizona State University, Phoenix. Arizona and National Institute for Chiropractic Research, Phoenix, AZ.
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.
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.