Archive for category Research

Abstract

STUDY DESIGN:

Surface electromyographic reflex responses associated with mechanical force, manually assisted (MFMA) spinal manipulative therapy were analyzed in this prospective clinical investigation of 20 consecutive patients with low back pain.

OBJECTIVES:

To characterize and determine the magnitude of electromyographic reflex responses in human paraspinal muscles during high loading rate mechanical force, manually assisted spinal manipulative therapy of the thoracolumbar spine and sacroiliac joints.

SUMMARY OF BACKGROUND DATA:

Spinal manipulative therapy has been investigated for its effectiveness in the treatment of patients with low back pain, but its physiologic mechanisms are not well understood. Noteworthy is the fact that spinal manipulative therapy has been demonstrated to produce consistent reflex responses in the back musculature; however, no study has examined the extent of reflex responses in patients with low back pain.

METHODS:

Twenty patients (10 male and 10 female, mean age 43.0 years) underwent standard physical examination on presentation to an outpatient chiropractic clinic. After repeated isometric trunk extension strength tests, short duration (<5 msec), localized posteroanterior manipulative thrusts were delivered to the sacroiliac joints, and L5, L4, L2, T12, and T8 spinous processes and transverse processes. Surface, linear-enveloped electromyographic (sEMG) recordings were obtained from electrodes located bilaterally over the L5 and L3 erector spinae musculature. Force-time and sEMG time histories were recorded simultaneously to quantify the association between spinal manipulative therapy mechanical and electromyographic response. A total of 1600 sEMG recordings were analyzed from 20 spinal manipulative therapy treatments, and comparisons were made between segmental level, segmental contact point (spinous vs. transverse processes), and magnitude of the reflex response (peak-peak [p-p] ratio and relative mean sEMG). Positive sEMG responses were defined as >2.5 p-p baseline sEMG output (>3.5% relative mean sEMG output). SEMG threshold was further assessed for correlation of patient self-reported pain and disability.

RESULTS:

Consistent, but relatively localized, reflex responses occurred in response to the localized, brief duration MFMA thrusts delivered to the thoracolumbar spine and SI joints. The time to peak tension (sEMG magnitude) ranged from 50 to 200 msec, and the reflex response times ranged from 2 to 4 msec, the latter consistent with intraspinal conduction times. Overall, the 20 treatments produced systematic and significantly different L5 and L3 sEMG responses, particularly for thrusts delivered to the lumbosacral spine. Thrusts applied over the transverse processes produced more positive sEMG responses (25.4%) in comparison with thrusts applied over the spinous processes (20.6%). Left side thrusts and right side thrusts over the transverse processes elicited positive contralateral L5 and L3 sEMG responses. When the data were examined across both treatment level and electrode site (L5 or L3, L or R), 95% of patients showed positive sEMG response to MFMA thrusts. Patients with frequent to constant low back pain symptoms tended to have a more marked sEMG response in comparison with patients with occasional to intermittent low back pain.

CONCLUSIONS:

This is the first study demonstrating neuromuscular reflex responses associated with MFMA spinal manipulative therapy in patients with low back pain. Noteworthy was the finding that such mechanical stimulation of both the paraspinal musculature (transverse processes) and spinous processes produced consistent, generally localized sEMG responses. Identification of neuromuscular characteristics, together with a comprehensive assessment of patient clinical status, may provide for clarification of the significance of spinal manipulative therapy in eliciting putative conservative therapeutic benefits in patients with pain of musculoskeletal origin.


 

Spine (Phila Pa 1976). 2001 May 15;26(10):1117-24. [PMID: 11413422]

Author information: Colloca CJ. Postdoctoral & Related Professional Education Department, Logan College of Chiropractic, St Louis, Missouri, USA.

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Abstract:

OBJECTIVE:

To characterize patients aged 55 years and older and features of chiropractic care provided to them.
DESIGN: Observational, practice-based research study.
SETTING: Chiropractic offices in the United States and Canada, 1997-1998.

PARTICIPANTS:

Chiropractors in 96 practices in 32 states and two Canadian provinces collected data on 805 eligible patients aged 55 years and older during a 12-week study period.

MEASUREMENTS:

In addition to questionnaires on practice characteristics, patient demographics, chief complaints, and health habits, two standardized instruments were administered: for general health status, the Medical Outcomes Study 12-Item Short-Form Health Survey (SF-12); and for disability related to chronic pain, the Pain Disability Index (PDI)

RESULTS:

Of 805 study patients, 60.1% were women and 94.7% were white. Overweight patients comprised 38.6% and obese 20.6% (n = 656) of the total; 9.7% of patients were hypertensive (n = 5.90). Smoking was reported by 12.7% and 50.2% reported regular exercise. The Physical Component Summary scores of the SF-12 seemed somewhat lower than population norms, where as the Mental Component Summary scores differed very little from norms. Chief complaints were predominantly pain-related (72.3%), most commonly back pain (32.9%). The PDI mean baseline score for chronic patients was 16.3 (scale, 0-70), and 40.6% of study patients reported using at least one pain medication (prescription or nonprescription) more than three times per week. More than half of complaints (54.9%) had onsets more than 6 weeks before the baseline visit. For 66.6% of subjects, a chiropractor was the only provider for their current complaint. In addition to manipulation, most common features of care were recommendations on exercise (41.0%), heat or cold applications (40.8%), and food supplements (24.5%). At 4 weeks, 19.6% were discharged, 58.8% continued treatment, and 20.1% had discontinued care (self-discharged). For these three groups, those with higher PDI mean baseline scores showed more change at 4 weeks. For patients who were discharged by the doctor, the proportion of reported pain medication use decreased 7.3% from baseline to 4 weeks, increased for patients who discontinued care, and remained about the same for those continuing care.

CONCLUSIONS:

Further investigation of the PDI and a decrease in pain medication use as outcome measures seems warranted. The descriptive information in this study may assist providers of care to older adults to better understand their patients’ use of chiropractic care.


J Am Geriatr Soc. 2000 May;48(5):534-45.  [PMID:10811547]

Author information: Hawk C, Long CR, Boulanger KT, Morschhauser E, Fuhr AW. Palmer Center for Chiropractic Research, Davenport, Iowa 52803, USA.

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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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Abstract

BACKGROUND:

Previous studies have demonstrated the existence era reflex response, measurable by surface electromyography (sEMG), after manually delivered spinal manipulative therapy (SMT). This reflex response has been characterized as consistent, reproducible within individual subjects, and nonlocal because it extends beyond the site of manipulation. However, the nature and magnitude of possible reflex responses in the paraspinal and proximal limb muscles elicited by nonmanual SMT, such as with an adjusting instrument, remain unknown.

OBJECTIVE:

To characterize the reflex responses associated with SMT by using sEMG to record the responses of 16 muscles before, during, and after treatment.

STUDY DESIGN:

The eleetromyographic responses of 16 para-spinal and proximal limb muscles in 9 healthy, asymptomatic male volunteers were measured simultaneously by sEMG before, during, and after chiropractic SMT.

METHODS:

SMT thrusts were delivered to 9 asymptomatic volunteers at 6 bilateral sites (C3/4, T2/3, T6/8, T11/12, L2-4, and s1). Reflex responses were measured from 16 muscles with bipolar sEMG electrodes and collected at 2000 Hz per channel with data acquisition software.

RESULTS:

Approximately 68% of the SMT thrusts resulted in a detectable reflex response. The cervical spine resulted in a detectable response of 50%, thoracic spine 59%, lumbar spine 83%, and sacroiliac joints 94%. Treatments delivered to the thoracic spine elicited the largest peak-to-peak amplitude sEMG responses, whereas the lumbar spine demonstrated the most heterogeneous responses. When a reflex response was observed, it always occurred close to the treatment site ipsilaterally and was detected in muscles that had either their origin or insertion at the vertebral level that was adjusted.

CONCLUSIONS:

Based on the local nature, magnitude, and characteristic shape of all reflex responses observed, we hypothesized that they were likely generated by a single proprioceptor. Furthermore, the temporal properties of this reflex response suggest that they originated from the muscle spindles. In contrast to previous observations on reflex responses after manual SMT, these treatments elicited reflex responses that varied between subjects but were consistent within an individual and were local in nature. We conclude that SMT delivered in this manner results in a reflex response that is both quantitatively and qualitatively different from a manual SMT.


J Manipulative Physiol Ther. 2000 Mar-Apr;23(3):155-9. [PMID:10771499]

Author information: Symons BP, Herzog W, Leonard T, Nguyen H. Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.

 

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Abstract

OBJECT:

Develop an analytical theory describing the dynamics of small impulses applied to vertebrae, such as in chiropractic adjustments or spinal manipulative therapy.

DESIGN:

Data were compared with damped harmonic oscillator models of vertebrae.

BACKGROUND:

Evidence accumulates that chiropractic adjustments are effective in addressing a variety of health problems. However, the biomechanics characterizing spinal manipulation is largely unknown. Recently, relative separations of the L2-L3 vertebrae subsequent to activator adjusting instrument thrusts were measured in vivo at 2048 Hz.

RESULTS:

Nine-parameter models for axial, shear and angular motions were fit to sets of 350 data points. They required frequencies of 5, 8 and 11 Hz, corresponding to well-known spinal resonances. The fits are excellent, with 0.75 < corrected R(2) < 0.96. Stiffnesses are calculated to be less than 10% of elastic zone values. Viscosities of the paravertebral medium are predicted to be between 6 and 30 poise, comparable to synovial fluids.

CONCLUSIONS:

This model ties together vertebral responses to small impulses with spinal resonances and other spinal/vertebral characteristics. Stiffness dominates damping resistance except in angular motions. Coupling appears unimportant in adjacent vertebral responses to small impulses. Further research is needed to clarify this issue.

RELEVANCE:

This study indicates how both force (determining amplitude) and thrust speed or duration (determining frequencies excited) may enter in terms of optimizing the efficacy of chiropractic adjustments. If stimulation of specific spinal frequencies, say as central nervous input, were most essential, then many chiropractic thrusts could be clinically similar. This may explain how over 90 chiropractic techniques can co-exist.


Clin Biomech (Bristol, Avon). 2000 Feb;15(2):87-94. [PMID:10627324]

Author information: Research Department, Life Chiropractic College West, 22336 Main St., Hayward, CA 94541, USA.

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2251. COVERAGE OF CHIROPRACTIC SERVICES

2251.1 Manual Manipulation.–Coverage of chiropractic service is specifically limited to treatment by means of manual manipulation, i.e., by use of hands. Additionally, manual devices (i.e., those that are hand-held with the thrust of the force of the device being controlled manually) may be used by chiropractors in performing manual manipulation of the spine. However, no additional payment is available for use of the device, nor does Medicare recognize an extra charge for the device itself.

No other diagnostic or therapeutic service furnished by a chiropractor or under his or her order is covered. This means that if a chiropractor orders, takes, or interprets an x-ray, or any other diagnostic test, the x-ray or other diagnostic test, can be used for claims processing purposes (see §4118.C.2(d)), but Medicare coverage and payment are not available for those services. (Of course, this prohibition does not affect the coverage of x-rays or other diagnostic tests furnished by other practitioners under the program. For example, an x-ray or any diagnostic test taken for the purpose of determining or demonstrating the existence of a subluxation of the spine is a diagnostic test covered under §1861(s)(3) of the Act if ordered, taken, and interpreted by a physician who is a doctor of medicine or osteopathy.)

Effective for claims with dates of service on or after January 1, 2000, an x-ray is not required to demonstrate the subluxation. However, an x-ray may be used for this purpose if the chiropractor so chooses.

The word “correction” may be used in lieu of “treatment.” Also, a number of different terms composed of the following words may be used to describe manual manipulation as defined above:

  • Spine or spinal adjustment by manual means;
  • Spine or spinal manipulation;
  • Manual adjustment; and
  • Vertebral manipulation or adjustment.

Rev. 1656/Page 2-101

 

Letter from Department of Health & Human Services stating Activator is a manual adjustment that is included in Medicare Coverage.

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Abstract

OBJECTIVE:

To investigate the interexaminer reliability of the prone extended relative leg-length check as described by Activator Methods, Inc.

SUBJECTS:

Thirty-four subjects were selected from a pool of 52 consecutive patients visiting a private chiropractic office.

METHODS:

Exclusion criteria included congenital or acquired conditions known to affect lower extremity length and inability to lie prone for a 10-minute period. Two experienced chiropractors who specialize in Activator Methods and are “advanced-proficiency rated” by Activator Methods, Inc. assessed each patient in random order for leg length inequality. Findings were recorded as left short leg, equal leg length, or right short leg.

RESULTS:

The data for 34 subjects were organized in a 3 x 3 contingency table. Total agreement was 85%. A simple, unweighted kappa value yielded kappa = 0.66. A disproportionately greater number of right short leg findings than left short leg findings were observed by both examiners. In only 2 instances were equal leg lengths observed, and both were detected by the same examiner. Because examiners found only 2 of 34 subjects with equal leg lengths, several secondary analyses involving data reductions were conducted. The resulting kappa values were similar to the 3 x 3 analysis.

CONCLUSION:

There was good reproducibility between 2 examiners by using the Activator Method to detect leg length inequality in the prone extended position. This study does not address the validity or clinical significance of the measurement method. Future studies should include larger numbers, a wider variety of subjects, and a diversity of examiners.


J Manipulative Physiol Ther. 1999 Nov-Dec;22(9):565-9. [PMID:10626698]

Author information: Nguyen HT, Resnick DN, Caldwell SG, Elston EW Jr, Bishop BB, Steinhouser JB, Gimmillaro TJ, Keating JC Jr. Los Angeles College of Chiropractic, Whittier, Calif, USA.

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Abstract

OBJECTIVE:

To discuss a case of coccygodynia that responded favorably to conservative chiropractic adjusting procedures with the Activator Methods Chiropractic Technique (AMCT) and the Activator II Adjusting Instrument (AAI II).

CLINICAL FEATURES:

A 29-year-old woman had unremitting coccygeal pain of 3 weeks’ duration. The problem began after she had moved heavy boxes while at work. The pain was characterized by a continual dull ache in the coccygeal region, accompanied by intermittent sharp pain, particularly upon sitting or rising from a seated position. She had been taking self-prescribed over-the-counter analgesics (aspirin and ibuprofen) for 3 weeks without obtaining relief.

INTERVENTION AND OUTCOME:

Treatment consisted of mechanical force, manually assisted, short-lever (MFMA) chiropractic adjusting procedures to the coccygeal area, primarily the sacrococcygeal ligament. The AAI II was used to deliver the adjustment according to diagnostic and treatment protocol specified for AMCT. The patient experienced first treatment.

CONCLUSION:

Chiropractic coccygeal manipulation may be effectively delivered via instrumental adjustment in certain cases of coccygodynia. The use of an AAI II in administering the coccygeal adjustment has the benefit of being a gentle, noninvasive procedure, as well as being comfortably tolerated by the patient. This method of coccygeal adjustment may bear consideration in certain cases of coccygodynia.


J Manipulative Physiol Ther. 1999 Jul-Aug;22(6):411-6. [PMID:10478774]

Author information: Polkinghorn BS, Colloca CJ. Postdoctoral and Related Professional Education Department Faculty, Logan College of Chiropractic, Phoenix, Arizona, USA.

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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

OBJECTIVE:

To determine the dynamic force-time and force-frequency characteristics of the Activator Adjusting Instrument and to validate its effectiveness as a mechanical impedance measurement device; in addition, to refine or optimize the force-frequency characteristics of the Activator Adjusting Instrument to provide enhanced dynamic structural measurement reliability and accuracy.

METHODS:

An idealized test structure consisting of a rectangular steel beam with a static stiffness similar to that of the human thoracolumbar spine was used for validation of a method to determine the dynamic mechanical response of the spine. The Activator Adjusting Instrument equipped with a load cell and accelerometer was used to measure forces and accelerations during mechanical excitation of the steel beam. Driving point and transfer mechanical impedance and resonant frequency of the beam were determined by use of a frequency spectrum analysis for different force settings, stylus masses, and stylus tips. Results were compared with beam theory and transfer impedance measurements obtained by use of a commercial electronic PCB impact hammer.

RESULTS:

The Activator Adjusting Instrument imparted a very complex dynamic impact comprising an initial high force (116 to 140 N), short duration pulse (<0.1 ms) followed by several lower force (30 to 100 N), longer duration impulses (1 to 5 ms). The force profile was highly reproducible in terms of the peak impulse forces delivered to the beam structure (<8% variance). Spectrum analysis of the Activator Adjusting Instrument impulse indicated that the Activator Adjusting Instrument has a variable force spectrum and delivers its peak energy at a frequency of 20 Hz. Added masses and different durometer stylus tips had very little influence on the Activator Adjusting Instrument force spectrum. The resonant frequency of the beam was accurately predicted by both the Activator Adjusting Instrument and electronic PCB impact hammer, but variations in the magnitude of the driving point impedance at the resonant frequency were high (67%) compared with the transfer impedance measurements obtained with the electronic PCB impact hammer, which had a more uniform force spectrum and was more repeatable (<10% variation). The addition of a preload-control frame to the Activator Adjusting Instrument improved the characteristics of the force frequency spectrum and repeatability of the driving point impedance measurements.

CONCLUSION:

These findings indicate that the Activator Adjusting Instrument combined with an integral load cell and accelerometer was able to obtain an accurate description of a steel beam with readily identifiable geometric and dynamic mechanical properties. These findings support the rationale for using the device to assess the dynamic mechanical behavior of the vertebral column. Such information would be useful for SMT and may ultimately be used to evaluate the [corrected] biomechanical effectiveness of various manipulative, surgical, and rehabilitative spinal procedures.


J Manipulative Physiol Ther. 1999 Feb;22(2):75-86. [PMID:10073622]

Author information: Keller TS, Colloca CJ, Fuhr AW. Department of Mechanical Engineering, University of Vermont, Burlington, USA.

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