Archive for category Conference Presentation

Abstract

The stress-strain relationships of human spinal ligaments and  muscles indicate that the spinal musculature play a major role in spine  stability (1, 2). Low-loading rate, quasi-static assessments of  posteroanterior (PA) spinal stiffness have correlated increased PA spine  stiffness to voluntary contracture of the lumbar extensor muscles (3,  4), No study, however, has examined the contributions of lumbar extensor  muscle and high-loading rate dynamic PA spinal stiffness. The objective  of this study was to quantify PA dynamic spinal stiffness at rest and  during maximal voluntary contraction (MVC) efforts in patients with LBP.  Twenty-two consecutive patients with LBP underwent dynamic spinal  stiffness assessment in the prone resting position and during lumbar  extensor muscle MVC, A hand-held Activator Adjusting Instrument equipped  with an impedance head was used to deliver high-loading rate( < 0,1  msec) PA manipulative thrusts (450 N) to the L3 spinous process for  spinal stiffness assessment using a previously validated technique (5).  Surface, linear enveloped, electromyographic (sEMG) recordings were  obtained during the thrusts from electrodes (8 leads) located over the  L3 and L5 erector spinae and data was normalized to subject individual  MVC’s. The accelerance (peak acceleration/peak force, kg-1) or stiffness  index was calculated for each of the thrusts and compared for the  resting and active MVC trials using a 2-tailed, paired t-test. A  significantly increased spine stiffness index (8.36%) (P=0.012) was  found upon MVC trials compared to prone resting stiffness indices.  Lumbar spine extensor MVC contributes to increased PA lumbar spine  stiffness. These findings corroborate the findings of others and add  support to the significance of the trunk musculature in providing spinal  stability.


Reference: Christopher J. Colloca, D.C.1, Tony S. Keller, Ph.D. 2 Daryn E. Seltzer, D.C.3, Arlan w. Fuhr, D.C.1;  Muscular and Soft-Tissue Contributions of Dynamic Posteroanterior  Spinal Stiffness; Proceedings of the International Conference on Spinal Manipulation,  Bloomington, MN September 21-23,2000.


1 Postdoctoral & Related Professional Education  Department Faculty, Logan College of Chiropractic, St. Louis, MO, USA;  National Institute of Chiropractic Research, Phoenix, AZ, USA; Private  Practice of Chiropractic, Phoenix, AZ, USA. 2 Professor, Department of Mechanical Engineering  & Department of Orthopedics and Rehabilitation, The University of  Vermont, Burlington, VT, USA. 3 National Institute of Chiropractic Research, Phoenix, AZ, USA; Private Practice of Chiropractic, Phoenix, AZ, USA.

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ABSTRACT

The purpose of this study was to determine the neuromuscular  reflex responses of the erector spinae musculature to spinal  manipulative thrusts (SMTs) in patients with LBP. 20 (10 male/10 female,  mean age = 43 yrs.) consecutive LBP patients received MFMA SMTs  delivered to the transverse and spinous processes of T8, T12, L2, L4,  L5, and the sacral base and PSIS by means of an Activator Adjusting  Instrument (AAI) equipped with an impedance head. Surface, linear  enveloped, electromyographic (sEMG) recordings were obtained from  electrodes located bilaterally over the L5 and L3 erector spinae muscles  during each of the thrusts. Repeated pre. post isometric extension  strength tests were performed to normalize reflex data. 1600 sEMG  recordings were analyzed from 20 SMT treatments and comparisons were  made between segmental level, segmental contact point (spinous vs.  tranverse processes), and magnitude of the sEMG reflex response. SEMG  threshold was further assessed for correlation of patient self. reported  pain and disability, Consistent, but relatively localized sEMG reflex  responses occurred in response to the MFMA SMTs. 95 % of patients showed  a positive sEMG response to MFMA SMT, Patients with frequent to  constant LBP symptoms tended to have a more marked sEMG response in  comparison to patients with occasional to intermittent LBP. This is the  first study demonstrating neuromuscular reflex responses associated with  MFMA SMT in patients with LBP.


Reference: Christopher J. Colloca, D.C.1, Tony S. Keller, Ph.D. 2, Daryn E. Seltzer, D.C.3, Arlan W. Fuhr, D.C.1;  Lumbar Erector Spinae Reflex Responses to Mechanical Force, Manually-  Assisted Thoracolumbar and Sacroiliac Joint Manipulation in Patients  with Low Back Pain; Proceedings of the 2000 International Conference on Spinal  Manipulation, Bloomington, MN September 21-23,2000.


1 Postdoctoral & Related Professional Education  Department Faculty, Logan College of Chiropractic, St, Louis, MO, USA;  National Institute of Chiropractic Research, Phoenix, AZ, USA; Private  Practice of Chiropractic, Phoenix, AZ, USA. 2 Professor, Department of Mechanical Engineering  & Department of Orthopedics and Rehabilitation, The University of  Vermont, Burlington, VT, USA. 3 National Institute of Chiropractic Research, Phoenix, AZ, USA; Private Practice of Chiropractic, Phoenix, AZ, USA.

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Abstract

Assessments of spinal stiffness are becoming more  popular in recent years as a objective biomechanical means to evaluate  the human frame. Studies investigating posteroanterior (PA) forces in  spinal stiffness assessment have shown relationships to spinal level,  body type, and lumbar extensor muscle activity. Such measures may be  important determinants to discriminate between patients with low back  pain and asymptomatic subjects. However, little objective evidence is  available discerning variations in PA stiffness and its clinical  significance. No study has investigated the relationships of invivo PA  spinal stiffness to radiographic images. L5-S1 disc to body height  ratios were calculated from digitized plane film lateral radiographs of  eighteen symptomatic LBP patients (8 females and 10 males, 15-69 years,  mean 44.3 SD 15.4 years). Posterior disc height ratio (PDR) and anterior  disc height ratio (ADR) were compared to the L5 posterior-anterior  dynamic effective stiffness determined using a validated in vivo  mechanical impedance assessment procedure [1]. Dynamic effective  stiffness (N/m) was calculated from the impedance-frequency response  spectrum as the dynamic mechanical impedance (Force/Velocity, Ns/m) x  circular frequency (rad/sec). Dynamic effective stiffness (minl) at the  first resonance frequency (fminl)is reported. No correlation was noted  between minl and ADR at L5. However, minl was positively correlated to  the PDR at L5 {minl=232 x PDR + 32 (R=0.76)}. Dynamic spinal stiffness  assessments may provide additional biomechanical data that may be prove  to be of use to clinicians in the diagnosis of lumbar spinal disorders.


Reference: Christopher J. Colloca,DC; Tony S. Keller,PhD; Terry  K. Peterson,DC; Daryn E. Seltzer,DC; Arlan W. Fuhr,DC. Proceedings of the International  Conference on Spinal Manipulation , Sept 21-23,2000.

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Introduction:

A biomechanical analysis of the spine is  important for understanding its response to different loading  environments. Although substantial information exists on the dynamic  response of the spine in the axial direction, little is known about the  dynamic response to externally applied, posterior-anterior (PA) directed  forces Such as chiropractic manipulations, in this paper, a  5-degree-of-freedom (DOF), lumped equivalent model the lumbar spine is  developed. Model results are compared to quasi-static, oscillatory and  impulsive force measurements of vertebral motion associated with  mobilization [1], manual manipulation [2] and mechanical force,  manually-assisted (MFMA) adjustments [3].

 

Material and methods:

Five Degree-of Freedom Model A 5-DOF mass, massless-spring and damper model of the lumbar  spine is shown in Fig. 1. This model differs from that of a single-DOF  system in that it has 5 natural frequencies.

Modeling of this multi-DOF structure necessitates one governing  equation of motion for each DOF; in matrix form: [M]d2x/dt2+ [C]dx/dt +  [K]x = [F] (1) where [M] is the mass matrix, [C] is the damping matrix,  [K] is the stiffness matrix, [F] is the PA excitation force matrix, and  x = x(t) is the resulting displacement vector. Here we assume that the  system has zero mass coupling, in which case [M] is diagonal. [K] is  written in terms of the stiffness influence coefficients and is a band  matrix along the diagonal. The equations of motion are solved in modal  space using the eigensolution (i.e. the modal properties) of the  homogeneous equation of motion (free vibration without damping). The  eigenvectors (mode shapes) are then assembled into a mode shape matrix such that[M]= [I] and [K] =[frequencies 2], where {tr} denotes the transpose, [I] is the diagonal identity matrix. Given modal damping ratios for each mode shape i, the 5×5 damping

Using Matlab, the motion response of the spine was studied in  response to a 100 N static load, 100 N sinusoidal oscillation, and 100 N  impulsive force applied to each of the vertebral segments. The  following coefficients were used for the mass matrix (kg) and stiffness  (kN/m) matrix [3]: ml=m2=0.170, m3=m4=m5=0.114; kl=50, k2=40, k3=k4=30, k5=45; l,…5= 0.25 (25% of critical) resulting in damping coefficients CIJ ranging from 40-60 Ns/m.

Results:

The PA damped and undamped natural frequencies predicted by the model  were 44.6 Hz and 46. 1 Hz, respectively. Steady State Response The  steady state response to a PA sinusoidal oscillation, f= Foe is given by  the frequency response function; H(oo)=[K oo2M + iooC] (3)For PA  sinusoidal loading, the model-predicted natural frequency ranged from  39-47 Hz (Fig. 2). At resonance, segmental and inter-segmental P A  displacements were 7.1 mm and 1.7 mm, respectively, for PA thrusts on  L3. PA spine mobilization [1] and manual manipulation [2]  correspond to an oscillatory frequency of ~2 Hz. At 2 Hz segmental and  Inter-segmental displacements were predicted to be 4.0 mm (L3) and 1.5  mm (L3-L4), respectively.

 

Impulsive Force Response: The response to an initial displacement [X0] and velocity [V0] was derived by assuming a solution x = UeM for eq. (1): PA MFMA adjustments produce a damped sinusoidal-like  oscillation With a duration of ~5 ms (impulsive force). Hence, we used  the impulse-momentum principle to estimate V0 (1.84 m/s) for a damped  MFMA oscillation f=466e-1000sin(200(3.14)t). Model predicted L3 and  L3.L4 displacements were 1.25 mm and 0.89 mm, respectively, for PA  impulsive forces at L3.

 

Discussion and Conclusions:

The model predicted PA  oscillatory and impulsive resonant frequency of the lumbar spine Is  consistent with previous experimental findings [3]. Segmental  displacements were over 3-fold greater for manual and mobilization  therapies in comparison to MFMA therapy, but differences in  inter-segmental displacements were less remarkable for these three types  of spinal manipulation.

 


Reference: T.S. Keller and C. J. Colloca; Dynamic  Response of the Human Lumbar Spine: A 5 DOF Lumped Parameter Time and  Frequency Domain Model; Proceeding of the 2000 Meeting of the European Society of  Biomechanics, Dublin, Ireland, August 10-14.

References: [1] M. Lee and N.L. Svensson (1993) JMPT 16:  439-446. [2] I. Gal et al. (1997) JMPT 20: 30.40. [3] T.S. Keller, C.I.  Colloca, and A. W. Fuhr(1999) JMPT 22: 75-86.

Acknowledgements: National Institute of Chiropractic Research; Foundation for the Advancement of Chiropractic Education.

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ABSTRACT

Objective:

The objective of this study was to determine if  mechanical force, manually-assisted (MFMA) spinal manipulative therapy  (SMT) affects paraspinal muscle strength assessed using surface  electromyography (sEMG).

Summary of Background Data:

A disorder in the  neuromusculoskeletal system may result in excessive load sharing of the  passive system that can cause abnormal motion and increased deformation  of its highly innervated structures resulting in LBP. SMT has been found  associated with reflex responses in the back musculature, however the  clinical relevance of such findings are not understood. The role of  rehabilitation programs of improving objective outcomes including  increases in trunk muscle strength are important goals of patient care.

Design:

This study is a prospective controlled clinical trial  comparing sEMG output in an active treatment group and two control  groups.

Methods:

Twenty consecutive LBP patients (SMT treatment group)  performed maximum voluntary contraction (MVC) isometric trunk extensions  while lying prone on a treatment table. Surface, linear enveloped sEMG  was recorded from the erector spinae musculature at L3 and L5 during the  trunk extension procedure. Subjects were then assessed using the  Activator Methods Chiropractic Technique (AMCT) protocol, during which  time they were treated using MFMA SMT. The MFMA SMT treatment was  followed by a dynamic stiffness and algometry assessment, after which a  second or post MVC isometric trunk extension and sEMG assessment was  performed. Another twenty subjects were randomized into two control  groups, a sham-SMT group, and a control group. The sham-SMT group  underwent the same experimental protocol with the exception that the  subjects received a sham-MFMA SMT and dynamic stiffness assessment. The  control group received no SMT treatment, stiffness assessment, or  algometry assessment intervention. Within group (pre-SMT vs. post-SMT  sEMG output) and across group analysis of sEMG output from MVC (pre/post  sEMG ratio) was performed using a paired observations t-test (POTT) and  analysis of variance (ANOVA), respectively.

Setting:

Outpatient chiropractic clinic, Phoenix, AZ, USA. Subjects: Forty total subjects participated in the study.  Twenty LBP patients (9 females and 11 males, 35 years and 51 years,  respectively) and twenty age and gender matched sham-SMT/control LBP  patients (10 females and 10 males, 40 years and 52 years, respectively)  were assessed.

Main Outcome Measures:

Surface electromyographic recordings  during isometric maximum voluntary contraction trunk extension were used  as the primary outcome measure.

Results:

Nineteen of the 20 patients in the SMT  treatment group showed a positive increase in sEMG output during MVC  (range -9.7% to 66.8%) following the active MFMA SMT treatment and  stiffness assessment. The SMT treatment group showed a significant  (POTT, P<<0.001) increase in erector spinae muscle sEMG output  (21% increase compared to pre-SMT levels) during MVC isometric trunk  extension trials. There were no significant changes in pre vs. post- SMT  MVC sEMG output for the sham-SMT (5.8% increase) or control (3.9%  increase) groups.


Reference: Tony S. Keller, Ph.D. and Christopher J.  Colloca, D.C.; Mechanical Force Spinal Manipulation Increases Trunk  Muscle Strength Assessed By Electromyography: A Comparative Controlled  Clinical Trial; Proceeding of the 27th Annual Meeting of the International Society for the Study of the Lumbar Spine, Adelaide, Australia, April 9-13, 2000.

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Introduction:

Lumbar spinal disorders including radial  tears, disc degeneration, segmental instability and segmental  dysfunction have been considered common causes of persistent back pain  and sciatica. Such disorders may be characterized as exhibiting  alterations in the mechanical behavior to loading, notably, changes in  spinal stiffness. Studies investigating posteroanterior (PA) forces in  spinal stiffness assessment have shown relationships to spinal level,  body type, and lumbar extensor muscle activity. Such measures may be  important determinants to discriminate between patients with low back  pain and asymptomatic subjects. However, little objective evidence is  available discerning variations in PA stiffness, a more complete  assessment based upon dynamic stiffness measurements (driving-point  impedance) and concomitant neuromuscular response may offer more  information concerning mechanical properties of the low back, Thus, the  aim of the current study was to determine the stiffness and  neuromuscular characteristics of the asymptomatic and symptomatic low  back,

Methods:

This study is a prospective clinical study  investigating the mechanical and muscular behavior of lumbar spinal  segments to high loading rate PA forces, 22 subjects (12 male & 10  female, mean age of 42.8+ or – 17.5 years, range 15-73 years) underwent a  comprehensive physical examination consisting of history,  orthopedic/neurologic examination, lumbar range of motion, pressure  algometry and plain film radiographic exanimation of the lumbar spine. A  visual analog score (VAS), Oswestry Low Back Disability Index, and  Health Status Questionnaire (SF-36) were obtained for all subjects and  categorization was made on the basis of symptom frequency, as well as  positive vs. negative orthopedic exam, acute vs. chronic (>12 weeks)  low back pain (LBP) history and electromyography (EMG) response to PA  mechanical stimulation. Each subject was placed in the prone position by  use of a motorized vertical/horizontal table. Surface, linear  enveloped, EMG recordings were obtained from electrodes (8 lead s)  located over the L3 and L5 paraspinal musculature to monitor the  bilateral neuromuscular activity of the erector spinae group during the  PA stiffness measurement protocol, Prior to and immediately following  the PA mechanical stimulation, each subject performed three consecutive  maximal effort isometric trunk extensions to normalize EMG data. A  hand-held Activator II Adjusting Instrument equipped with a load cell  and accelerometer was used to deliver high rate (<0.1 msec ) PA  mechanical stimulation (450 N) to several common spinal landmarks  including the PSIS, sacral base and L5, L4, L2, T12, T8 spinous and  transverse processes. Driving point impedance (Z, Ns/m) was calculated  for each of the thrusts, from which the effective dynamic stiffness (Z x  2(3.21)f) was determined.

Results:

Two of the subjects were asymptomatic (no prior history of LBP), 6 had occasional LBP symptoms, 4 intermittent, and 10 had chronic symptoms of LBP. Subjects with chronic symptoms were characterized by higher effective dynamic stiffness at all levels and had a 2.5-fold higher Oswestry index and VAS score in comparison to the other subjects. Ten of the subjects had an abnormal orthopedic examination and were characterized by a significantly higher dynamic stiffness at all levels. These ten subjects also had over a 2.5-fold greater Oswestry index and VAS score in comparison to the subjects with a normal exam. LBP chronicity was also associated with a 2.5-fold and 3~fold greater Oswestry and VAS score, respectively, in comparison to acute pain sufferers. no differences in dynamic stiffness were observed between these subject groups, however. Of interest was our finding that 16 of the subjects exhibited a hyper-neuromuscular response in response to the PA mechanical stimulation. A hyper-neuromuscular response was characterized as a prominent EMG response (≥ 10% of the isometric extension EMG response) in 10% or more of the EMG recordings (80 total/subject). In this group of subjects the Oswestry index and VAS score were nearly 3-fold and 6-fold greater, respectively, in comparison to subjects which showed little or no mechanically-activated EMG response. Also noteworthy, was the finding that, while lumbar level PA stiffness measurements were similar for these two groups, the thoracic level PA stiffness values were significantly greater in the hyper-neuromuscular group.

Discussion:

The results of this preliminary study provide additional support for clinical assessment strategies that utilize a non-invasive dynamic stiffness measurement system to probe and quantify the mechanical characteristics of the spine. It was noted that subjects with hyper-neuromuscular responses presented with more severe disability outcome scores and a positive orthopedic exam. Further measurements of the dynamic stiffness and neuromuscular characteristics of the symptomatic and asymptomatic LBP population are required to clarify the significance of this observation. Such diagnostic measurements, when combined with conservative manipulative care of the back may prove to be a particularly effective means to diagnostically probe and treat lower back disorders.


Reference: Christopher J. Colloca, D.C., Tony S. Keller,  Ph.D. , Arlan W. Fuhr, D.C.; Muscular And Mechanical Behavior Of The  Lumbar Spine In Response To Dynamic Posteroanterior Forces; Proceedings  of the 26th Annual Meeting of the International Society for the Study of  the Lumbar Spine, Kona, Hawaii. Toronto: ISSLS, 1999: 136A.

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ABSTRACT

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.

METHOD

-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.

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ABSTRACT

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.

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Abstract:

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.

Method:

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.

Results:

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).

Conclusions:

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.

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Abstract:

Background and Objectives:

Little is known  about the dynamics of spinal manipulation and mechanical force manually  assisted short lever adjustments in particular. The purpose of this  study is to quantify the biomechanical response to impulsive loads  applied over the cervical spine. A previous study had enabled us to  quantify the response for the lumbar spine. This would enable the  estimation of the internal motion and loading that occurs due to the  instrument delivered short lever chiropractic adjustment.

Method:

An anthropomorphic model of the human  body has been constructed for this study. The Activator Adjusting  Instrument, a product of Activator Methods Inc, (Phoenix, AZ), is used  to produce the impulsive loads. The elements of the model involve bones,  ligaments, intervertebral discs and muscles which are constructed from  composite materials that closely mimic the passive properties of the  physiological systems. The instrumentation includes displacement,  acceleration and pressure transducers. The sampling rate of the data was  1,o00 Hz and filtering of the data is done using software.

Results:

The anthropomorphic model has been  used in a previous study to study the dynamics of spinal manipulation in  the lumbar spine. It has been found to be a reasonable substitute for  the human spine, in terms of the mechanical responses to forces and/or  torques. The present study involved data collection in the cervical  spine at the levels of C1, C2, C5 and C6. Preliminary data analysis has  been done and the movement response to applied thrusts on the spine has  been done qualitatively and a quantitative analysis is expected to be  done on data in the near future.

Conclusions:

Anthropomorphic modeling may prove useful  in understanding the dynamics of spinal manipulation, particularly when  integrated with computer modeling and in vivo studies. Acknowledgement: This study was funded by the National Institute of Chiropractic Research.


Reference: Sridhar Venkataraman, BS, Gary T. Yamaguchi,  PhD, Paul J. Osterbauer, OG, and Arlan W. Fuhr .DC, Arizona State  University, Tempe. AZ, The National Institute of Chiropractic Research,  Phoenix. AZ; Evaluating Mechanical Force Manually Assisted Short Lever  adjusting using an Anthropomorphic model; In: The proceedings of the  FCER’s 1993 International Conference on Spinal Manipulation, Montreal,  Quebec, Canada, April 30-May 1, Page 13.

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