In vivo transient vibration assessment of the normal human thoracolumbar spine.

OBJECTIVE: The objective of this study was to quantify the mobility characteristics (dynamic stiffness and mechanical impedance) of the normal human thoracolumbar spine with a transient vibration analysis technique. DESIGN: This study is a prospective clinical investigation to obtain normative biomechanical data from the human male and female spine in vivo. SETTING: Musculoskeletal research laboratory, university setting. SUBJECTS: Twenty asymptomatic subjects (age range, 20-60 years) with no recent history of musculoskeletal complaints. MAIN OUTCOME MEASURES: Mechanical impedance, effective stiffness, and resonant frequency analyses were used to quantify the dynamic stiffness of the thoracolumbar spine in this subject population. Data were obtained from posteroanterior mechanical thrusts delivered with an activator adjusting instrument equipped with a load cell and accelerometer by means of a portable computer. RESULTS: In response to the activator adjusting instrument thrusts, the thoracolumbar spine typically exhibited an impedance minimum at frequencies ranging between 30 and 50 Hz. The maximum posteroanterior impedance and corresponding maximum effective stiffness of the thoracolumbar spine and sacrum was roughly 2 to 8 times greater than the magnitude of the impedance minimum. Statistically significant differences in mobility between male and female subjects were noted, particularly for frequencies corresponding to the maximum mobility (40 Hz) and minimum mobility (10-20 Hz, 70-80 Hz). For most subjects (both male and female), the lumbar region exhibited a higher impedance and stiffness (less mobility) when compared with the thoracic region. CONCLUSIONS: The posteroanterior mechanical behavior of the human thoracolumbar spine was found to be sensitive to mechanical stimulus frequency and showed significant region-specific and gender differences. In the frequency range of 30 to 50 Hz, the lumbar spine of this subject population is the least stiff and therefore has the greatest mobility. From a biomechanical point-of-view, the results of this study indicate that dynamic spinal manipulative therapy procedures will produce more spinal motion for a given force, particularly when the posteroanterior manipulative thrust is delivered in frequency ranges at or near the resonant frequency. In this regard, spinal manipulative therapy procedures designed to target the resonant frequency of the spine require less force application. Both magnitude and frequency content of manual and mechanical thrusting manipulations may be critical elements for therapeutic outcome.

Neurophysiologic response to intraoperative lumbosacral spinal manipulation.

BACKGROUND: Although the mechanisms of spinal manipulation are poorly understood, the clinical effects are thought to be related to mechanical, neurophysiologic, and reflexogenic processes. Animal studies have identified mechanosensitive afferents in animals, and clinical studies in human beings have measured neuromuscular responses to spinal manipulation. Few, if any, studies have identified the basic neurophysiologic mechanisms of spinal manipulation in human beings or animals. OBJECTIVES: The purpose of this clinical investigation was to determine the feasibility of obtaining intraoperative neurophysiologic recordings and to quantify mixed-nerve root action potentials in response to lumbosacral spinal manipulation in a human subject undergoing lumbar spinal surgery. METHODS: An L4-L5 laminectomy was performed in a 62-year-old man. Short-duration (<0.1 ms) mechanical force, manually assisted spinal manipulative thrusts (150 N) were delivered to the lumbosacral spine with an Activator II Adjusting Instrument. With the spine exposed, spinal manipulative thrusts were delivered internally to the L5 mammillary process, L5-S1 joint, and the sacral base with various force vectors. This protocol was repeated by contacting the skin overlying respective anatomic landmarks. Mixed-nerve root recordings were obtained from gas-sterilized platinum bipolar hooked electrodes attached to the S1 nerve root at the level of the dorsal root ganglion during the spinal manipulative thrusts and during a 30-second baseline period during which no spinal manipulative thrusts were applied. RESULTS: During the active trials, mixed-nerve root action potentials were observed in response to both internal and external spinal manipulative thrusts. Differences in the amplitude and discharge frequency were noted in response to varying segmental contact points and force vectors, and similarities were noted for internally and externally applied spinal manipulative thrusts. Amplitudes of mixed-nerve root action potentials ranged from 200 to 2600 mV for internal thrusts and 800 to 3500 mV for external thrusts. CONCLUSIONS: Monitoring mixed-nerve root discharges in response to spinal manipulative thrusts in vivo in human subjects undergoing lumbar surgery is feasible. Neurophysiologic responses appeared sensitive to the contact point and applied force vector of the spinal manipulative thrust. Further study of the neurophysiologic mechanisms of spinal manipulation in humans and animals is needed to more precisely identify the mechanisms and neural pathways involved.

Chiropractic care for patients aged 55 years and older: report from a practice-based research program.

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 = 590). 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, whereas 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.

Validation of the force and frequency characteristics of the activator adjusting instrument: effectiveness as a mechanical impedance measurement tool.

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.

Neuro-optometric facilitation of vision recovery after acquired brain injury.

Visual field loss following brain injury often impairs the individual's rehabilitation, function and safety. Such impairments prevent individuals from returning to productive lifestyles. A previous article documents outcomes that measure increased awareness for patients suffering visual field loss. This research investigates and reports on increasing visual recovery, as well as functional and emotional rehabilitation outcomes, using the Visual Field Awareness System™ and treatment strategies. The three case studies represent issues including age, visual field loss, vision recovery as a dynamic process, and functional outcome measures. Measures of increased awareness, recovery of vision, relative visual field sensitivity, continued recovery even after completion of treatment, and improved emotional status with gained independence were among the positive outcome results of this research.

Three-dimensional head kinematics and cervical range of motion in the diagnosis of patients with neck trauma.

OBJECTIVE: To create a statistical model using three-dimensional (3D) head kinematics and range of motion (ROM) to distinguish between people with whiplash syndrome and asymptomatic controls. STUDY DESIGN: Cross-sectional study to estimate validity of diagnostic measures. METHODS: Fifty-one asymptomatic controls (most of whom were women), 18-35 yr old and 30 matched whiplash trauma patients seeking care from suburban outpatient clinics were sought. 3D kinematic parameters of head motion were obtained during tracking tasks (e.g., flexion, extension, etc.) and cervical ROM was measured via a head mounted inclinometer. Their level of pain and disability was assessed via a self-administered neck disability index questionnaire and visual analog pain scale (VAS). RESULTS: A scoring system of biomechanical abnormalities derived from the vertical piercing point, its second derivative and symmetry during oblique tasks. The scores ranged from a minimum of 0 to a maximum of 3. A cutoff of > or = 0.5 correctly identified the greatest number of subjects and minimized false positives (sensitivity 77%, specificity 82%, likelihood ratio 4.5). ROM performed similarly well at a cutoff of 1 SD below the normative mean (sensitivity 77%, specificity 84%, likelihood ratio 3.9). CONCLUSIONS: There is potential for biomechanical analysis to objectively detect abnormalities. The statistical model yielded moderate to high sensitivity and specificity using 3D helical-axis parameters of the head and standard ROM. The model development will continue via this process in future studies. These data could be a first step toward the creation of useful, noninvasive protocols for the diagnosis and management of soft tissue trauma of the neck.

Instantaneous helical axis estimation from 3-D video data in neck kinematics for whiplash diagnostics.

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 the 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 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 for 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.

Optoelectric measurement of changes in leg length inequality resulting from isolation tests.

OBJECTIVE: a) Establish a precise, standardized method to assess prone leg alignment changes (functional "leg length inequality"), which have, until now, been reported clinically to occur as a result putative chiropractic subluxation isolation tests [neck flexion (C5) and extension (C1)]; and b) describe differences in leg alignment changes in a group of healthy subjects and patients with chronic spinal complaints. DESIGN: Two group, two isolation tests, descriptive, repeated measure analysis of variance. SETTING: Exercise and Sport Research Institute, Arizona State University. PARTICIPANTS: Eight healthy controls, eight patients with a history of chronic spinal complaints and observable leg alignment reactivity. INTERVENTIONS: Active cervical flexion/extension maneuvers. OUTCOME MEASURES: Optoelectric markers affixed to heels and occiput, as subjects lay prone. Marker locations sampled at 100 Hz for 10 sec during: a) three no movement trials, b) three cervical extension and c) three flexion trials. Data transformed to local reference frame approximately each subject's longitudinal axis prior to analysis. RESULTS: Heel position movement occurred during trials and were highly individualistic. Patients exhibited more asymmetrical movements than the controls during the head-up trials. No differences existed between controls and patients for range of heel displacement or net displacement. CONCLUSIONS: The results of this study allow the following to be concluded: 1) small leg displacements (< 1 mm) were recorded by the optoelectric measurement system; 2) heel position changes during isolation tests were identifiable; 3) as a result of head-up maneuvers, patients exhibited more asymmetrical heel movement than controls (t = 8.743, p < .01); 4) The heel range of motion was not different between the groups; and 5) The net change in heel position was not different between the groups. Patients exhibited more asymmetrical heel motion during head-up isolation tests, suggesting that some phenomena may separate these two groups, warranting future study.

Three-dimensional head axis of rotation during tracking movements. A tool for assessing neck neuromechanical function.

The purpose of this article is to report normal variation in the screw (helical) axis of rotation of the head during various types of natural tracking movements. Nine normal subjects and eighteen subjects with neck injury faced a grid of targets separated by 10-degree intervals, and were instructed to use a head pointer (laser) to track whatever target was lit. Various horizontal, vertical, and oblique target sequences were employed. The normal subjects exhibited several consistent trends in finite screw axis parameter variation: vertical movements have a laterally-directed axis whose midsagittal plane crossing position is a function of the head orientation (typical range C3-T1); oblique movements have a diagonally-directed axis and an even greater orientation-specific range (C1-T1); and horizontal movements have a vertical axis that is modified near horizontal orientation extremes and is asymmetrically influenced by upward and downward bias orientations. Subjects with neck injury were seen to exhibit a variety of abnormal screw axis patterns.

Treatment and biomechanical assessment of patients with chronic sacroiliac joint syndrome.

OBJECTIVE: To evaluate diagnostic and biomechanical correlates and treatment outcomes of manipulative/adjustive care in patients highly selected for sacroiliac joint syndrome (SIJS). DESIGN: Descriptive case series, 1 wk baseline, 1 yr follow-up. SETTING: Private chiropractic practice. PATIENTS: Ten out of 153 consecutive new patients (4 male and 6 female) with "primary," chronic, uncomplicated SIJS were selected over an 11-mo period on the basis of painful SIJ and provocation tests. MAIN OUTCOME MEASURES: Back pain (visual analogue scale), Oswestry disability index, lumbar provocation tests and biomechanical measures of gait and postural sway. INTERVENTION: Six-wk regimen of mechanical force, manually assisted, short lever adjustments (MFMA) with an Activator instrument. RESULTS: Pain decreased significantly from a mean baseline value of 25 to 12 (t = 2.28; p < .05). Likewise, the average disability scores diminished from 28 to 13% (t = 2.3; p < .05), and a reduction in the number of positive provocation tests was noted (Fisher Exact Probability range Z = 0.025-0.045). Gait and sway parameters were indistinguishable from normals, before or after treatment. Response to the 1-yr follow-up questionnaire (6/10) revealed stability of symptoms at a low level. CONCLUSIONS: While the majority of subjects recorded some degree of positive outcome, we conclude that: a) discrete SIJS remains difficult to diagnose, but may be possible by judicious choice of screening tests; b) MFMA may benefit some patients with chronic SIJ pain; and c) gait and sway measurement yielded no correlation with clinical conditions.

Treatment of Bell's palsy by mechanical force, manually assisted chiropractic adjusting and high-voltage electrotherapy.

Bell's palsy is a relatively common, painful, unilateral facial paralysis of unknown etiology. While often claimed to be successfully treated by chiropractic methods, no standard treatment approach is generally recognized within the profession, nor has any report of chiropractic treatment of this condition been reported in the literature. This article discusses two cases of Bell's palsy successfully treated by mechanical force, manually assisted chiropractic adjusting technique combined with high-voltage electrotherapy. While these two cases do not necessarily represent any rule for the chiropractic treatment of Bell's palsy by the methods used, or for other chiropractic methods that may be used, they do represent an initial time/treatment "baseline" by which future inter- and intratechnique comparisons may be made for the determination of relative effectiveness.

Three-dimensional head kinematics and clinical outcome of patients with neck injury treated with spinal manipulative therapy: a pilot study.

OBJECTIVE: Finite helical axis parameters (FHAP) of the cervical spine and clinical measures were obtained to evaluate neck function and the clinical effects of spinal manipulative therapy in patients with "whiplash" (WL) type neck injury. DESIGN: Descriptive case series, 1 yr follow-up. SETTING: Three private chiropractic practices. SUBJECTS: Ten consecutive new patients with a history of neck injury, nine asymptomatic, volunteer controls. INTERVENTIONS: A 6-wk regimen of short lever manually assisted adjustments with an Activator Instrument, while acute, four patients received interferential electrotherapy. MAIN OUTCOME MEASURES: Cervical FHAP during normal movements, neck pain (visual analogue scale), active cervical range of motion and follow-up questionnaire. RESULTS: Based on six patients, the FHAPs appeared to mirror the clinical condition, being markedly deviant from the patterns observed in the control group for at least one or more of the tracking tasks for all but one of the patients. Mean pain scores decreased from 44.1 to 10.5 (t = 4.93; p < .0001) and mean total range of motion increased from 234 to 297 degrees (t = 5.68; p < .0001). At 1 yr, seven respondents noted stability of their symptoms at or near the level reported immediately after the 6-wk treatment period. CONCLUSIONS: Based on these preliminary data: a) FHAPs may aid in diagnosing and monitoring treatment of neck dysfunction, b) spinal manipulative therapy may be beneficial to some patients with neck injury and future study is warranted as a means to promote recovery of patients with neck injuries.

Mechanical force, manually assisted short lever chiropractic adjustment.

OBJECTIVES: Chiropractic mechanical force, manually assisted short lever adjusting is a spinoff of the specific toggle recoil adjusting techniques, which were based on the original chiropractic subluxation theory propounded by Daniel David Palmer in 1895. This article reviews: a) the principles of the chiropractic subluxation complex from the standpoint of its historical origin and present-day scientific status; b) the purpose and objectives of specific spinal manipulative techniques; c) the use of mechanical adjusting instruments to effect a velocity/direction controlled adjustive thrust; and d) an assessment of scientific and clinical data relating to the biomechanical and neurological aspects of mechanical force, manually assisted short lever adjusting. DATA SOURCES: Prime sources were from the National Library of Medicine's on-line Index Medicus database, the Chirolars Research Resource Retrieval database, the Chiropractic Research Abstract Collection and the Chiropractic Library Consortium's reference works. Direct search of other nonindexed chiropractic sources was limited to those available in the collection of the National Institute of Chiropractic Research. Early information never documented by publication was obtained by written personal communication. STUDY SELECTION: The principal author selected articles reporting data (as opposed to anecdotal reports) from conference proceedings and peer-reviewed journals. DATA EXTRACTION: Data quality was assessed based on experimental conditions such as sample size, study design and statistical analysis. DATA SYNTHESIS: While mechanical force, manually assisted short lever adjusting seemingly is capable of beneficially altering the cause/effect relationship of spinal subluxations, more research in the nature of controlled clinical trials is needed to ascertain its benefits in the chiropractic treatment of specific conditions. CONCLUSIONS: Basic research is needed in order to establish the scientific basis for the chiropractic subluxation syndrome regardless of the technique employed.

Interexaminer reliability of an isolation test for the identification of cervical subluxation.

A reliability study was conducted to determine whether prone leg length analysis in association with an isolation test maneuver was reproducible. Seventy-two subjects were evaluated by two examiners on separate occasions for the presence of C1 subluxation. Concordance was assessed by the Kappa statistic, and interexaminer percentage of agreement was compared. Agreement beyond chance for the two groups was K = 0.52, p less than 0.01 and 0.55, p less than 0.001, respectively. The results indicate good reliability using this method of analysis for putative upper cervical subluxation in this patient population. Further investigation is necessary to correlate this method of analysis with the empirical evidence of manipulable lesions or subluxations.

Skin accelerometer displacement and relative bone movement of adjacent vertebrae in response to chiropractic percussion thrusts.

The authors studied relative bone movements in response to manipulative light taps to the spine. Piezoelectric accelerometers attached to bone of an anesthetized dog measured transverse, X-Z plane, movements of L2-L3 adjacent vertebrae while percussion thrusts of an instrument used for manipulation made inputs three vertebrae above and five vertebrae below the L2-L3 joint interface. Small, relative 1-mm translations and 0.5 degree rotations occurred during the first 19 msec. When one set of accelerometers were stabilized on the skin surface, half of the skin-bone translation maxima erred less than 2%. However, skin translations averaged 77% (SD = 2%) of bone translations and skin rotations averaged 95% (SD = 26%) of bone rotations. The results suggest the possibility that, with further development, piezoelectric accelerometers can be a noninvasive tool to study dynamic, relative, bone movement.

Accuracy of piezoelectric accelerometers measuring displacement of a spinal adjusting instrument.

The accuracy and reproducibility of an electronic system to measure the displacement of a spring-loaded chiropractic adjusting instrument was examined. The electronic system included a piezoelectric force transducer, piezoelectric accelerometer transducers and a digital oscilloscope. Accuracy was studied by comparing electronic measurements with the expansion allowed by the mechanically limiting expansion-control knob of the instrument. The results suggested improvements for future accuracy verification checks and detected accuracy within about 10% of the expansion of the commonly used expansion-control-knob revolutions. Preliminary experiments are presented to show application of the system to studies on thrusts into the spine. The impedance-head-equipped spring-loaded Activator chiropractic adjusting instrument had a low velocity when used on the patient and appeared to cause bone movement and a measurable EMG response.