Relationships between joint motion and facet joint capsule strain during cat and human lumbar spinal motions.

OBJECTIVE: The lumbar facet joint capsule (FJC) is innervated with mechanically sensitive neurons and is thought to contribute to proprioception and pain. Biomechanical investigations of the FJC have commonly used human cadaveric spines, whereas combined biomechanical and neurophysiological studies have typically used nonhuman animal models. The purpose of this study was to develop mathematical relationships describing vertebral kinematics and FJC strain in cat and human lumbar spine specimens during physiological spinal motions to facilitate future efforts at understanding the mechanosensory role of the FJC. METHODS: Cat lumbar spine specimens were tested during extension, flexion, and lateral bending. Joint kinematics and FJC principal strain were measured optically. Facet joint capsule strain-intervertebral angle (IVA) regression relationships were established for the 3 most caudal lumbar joints using cat (current study) and human (prior study) data. The FJC strain-IVA relationships were used to estimate cat and human spine kinematics that corresponded to published sensory neuron response thresholds (5% and 10% strain) for low-threshold mechanoreceptors. RESULTS: Significant linear relationships between IVA and strain were observed for both human and cat during motions that produced tension in the FJCs (P < .01). During motions that produced tension in the FJCs, the models predicted that FJC strain magnitudes corresponding to published sensory neuron response thresholds would be produced by IVA magnitudes within the physiological range of lumbar motion. CONCLUSIONS: Data from the current study support the proprioceptive role of lumbar spine FJC and low-threshold mechanoreceptive afferents and can be used in interpreting combined neurophysiological and biomechanical studies of cat lumbar spines.

Validation of the cat as a model for the human lumbar spine during simulated high-velocity, low-amplitude spinal manipulation.

High-velocity, low-amplitude spinal manipulation (HVLA-SM) is an efficacious treatment for low back pain, although the physiological mechanisms underlying its effects remain elusive. The lumbar facet joint capsule (FJC) is innervated with mechanically sensitive neurons and it has been theorized that the neurophysiological benefits of HVLA-SM are partially induced by stimulation of FJC neurons. Biomechanical aspects of this theory have been investigated in humans while neurophysiological aspects have been investigated using cat models. The purpose of this study was to determine the relationship between human and cat lumbar spines during HVLA-SM. Cat lumbar spine specimens were mechanically tested, using a displacement-controlled apparatus, during simulated HVLA-SM applied at L5, L6, and L7 that produced preload forces of approximately 25% bodyweight for 0.5 s and peak forces that rose to 50-100% bodyweight within approximately 125 ms, similar to that delivered clinically. Joint kinematics and FJC strain were measured optically. Human FJC strain and kinematics data were taken from a prior study. Regression models were established for FJC strain magnitudes as functions of factors species, manipulation site, and interactions thereof. During simulated HVLA-SM, joint kinematics in cat spines were greater in magnitude compared with humans. Similar to human spines, site-specific HVLA-SM produced regional cat FJC strains at distant motion segments. Joint motions and FJC strain magnitudes for cat spines were larger than those for human spine specimens. Regression relationships demonstrated that species, HVLA-SM site, and interactions thereof were significantly and moderately well correlated for HVLA-SM that generated tensile strain in the FJC. The relationships established in the current study can be used in future neurophysiological studies conducted in cats to extrapolate how human FJC afferents might respond to HVLA-SM. The data from the current study warrant further investigation into the clinical relevance of site targeted HVLA-SM.

AAPT Diagnostic Criteria for Chronic Low Back Pain.

Chronic low back pain (CLBP) conditions are highly prevalent and constitute the leading cause of disability worldwide. The Analgesic, Anesthetic, and Addiction Clinical Trial Translations Innovations Opportunities and Networks (ACTTION) public-private partnership with the US Food and Drug Administration and the American Pain Society (APS), have combined to create the ACTTION-APS Pain Taxonomy (AAPT). The AAPT initiative convened a working group to develop diagnostic criteria for CLBP. The working group identified 3 distinct low back pain conditions which result in a vast public health burden across the lifespan. This article focuses on: 1) the axial predominant syndrome of chronic musculoskeletal low back pain, 2) the lateralized, distally-radiating syndrome of chronic lumbosacral radicular pain 3) and neurogenic claudication associated with lumbar spinal stenosis. This classification of CLBP is organized according to the AAPT multidimensional framework, specifically 1) core diagnostic criteria; 2) common features; 3) common medical and psychiatric comorbidities; 4) neurobiological, psychosocial, and functional consequences; and 5) putative neurobiological and psychosocial mechanisms, risk factors, and protective factors. PERSPECTIVE: An evidence-based classification of CLBP conditions was constructed for the AAPT initiative. This multidimensional diagnostic framework includes: 1) core diagnostic criteria; 2) common features; 3) medical and psychiatric comorbidities; 4) neurobiological, psychosocial, and functional consequences; and 5) putative neurobiological and psychosocial mechanisms, risk factors, and protective factors.

Comparing recruitment strategies in a study of acupuncture for chronic back pain.

BACKGROUND: Meeting recruitment goals is challenging for many clinical trials conducted in primary care populations. Little is known about how the use of different recruitment strategies affects the types of individuals choosing to participate or the conclusions of the study. METHODS: A secondary analysis was performed using data from participants recruited to a clinical trial evaluating acupuncture for chronic back pain among primary care patients in a large integrated health care organization. We used two recruitment methods: mailed letters of invitation and an advertisement in the health plan's magazine. For these two recruitment methods, we compared recruitment success (% randomized, treatment completers, drop outs and losses to follow-up), participant characteristics, and primary clinical outcomes. A linear regression model was used to test for interaction between treatment group and recruitment method. RESULTS: Participants recruited via mailed letters closely resembled those responding to the advertisement in terms of demographic characteristics, most aspects of their back pain history and current episode and beliefs and expectations about acupuncture. No interaction between method of recruitment and treatment group was seen, suggesting that study outcomes were not affected by recruitment strategy. CONCLUSION: In this trial, the two recruitment strategies yielded similar estimates of treatment effectiveness. However, because this finding may not apply to other recruitment strategies or trial circumstances, trials employing multiple recruitment strategies should evaluate the effect of recruitment strategy on outcome. TRIAL REGISTRATION: Clinical Trials.gov NCT00065585.

Dynamic responsiveness of lumbar paraspinal muscle spindles during vertebral movement in the cat.

Muscle spindles provide essential information for appropriate motor control. In appendicular muscles, much is known about their position and movement sensitivities, but little is known about the axial muscles of the low back. We investigated the dynamic responsiveness of lumbar paraspinal muscle spindle afferents from L(6) dorsal root filaments during constant velocity movement of the L(6) vertebra (the feline has seven lumbar vertebrae) in Nembutal-anesthetized cats. Actuations of 1 mm applied at the L(6) spinous process were delivered at 0.5, 1.0 and 2.0 mm/s. The slow velocity component was measured as the slope of the relationship between displacement during the constant velocity ramp and instantaneous discharge frequency. The quick velocity component was the slope's intercept at zero displacement. The peak component was determined as the highest discharge rates occurring near the end of the ramp compared with control. The slow velocity component over the three increasing velocities was 23.9 (9.9), 21.6 (9.6) and 20.5 (9.5) imp/(s mm) [mean (SD)], respectively. The quick velocity component was 28.4 (8.6), 31.4 (9.8) and 35.8 (10.6) imp/s, respectively. These measures of dynamic responsiveness were at least 5-10 times higher compared with values reported for appendicular muscle spindles. The peak component's velocity sensitivity was 2.9 (imp/s)/(mm/s) [0.2, 5.5, lower, upper 95% confidence interval] similar to that for cervical paraspinal muscles as well as appendicular muscles. Increased dynamic responsiveness of lumbar paraspinal muscle spindles may insure central driving to insure control of intervertebral motion during changes in spinal orientation. It may also contribute to large, rapid and potentially injurious increases in paraspinal muscle activity during sudden and unexpected muscle stretch.

Characteristics of patients with chronic back pain who benefit from acupuncture.

BACKGROUND: Although many clinicians believe there are clinically important subgroups of persons with "non-specific" low back pain, such subgroups have not yet been clearly identified. As part of a large trial evaluating acupuncture for chronic low back pain, we sought to identify subgroups of participants that were particularly responsive to acupuncture. METHODS: We performed a secondary analysis of data for the 638 participants in our clinical trial comparing different types of acupuncture to usual care to identify baseline characteristics that predicted responses to individualized, standardized, or simulated acupuncture treatments. After identifying factors that predicted improvements in back-related function or symptoms, we determined if these factors were more likely to predict improvement for those receiving the acupuncture treatments than for those receiving usual care. This was accomplished by testing for an interaction between the prognostic factors and treatment group in four models: functional outcomes (measured by the Roland-Morris Disability Scale) at 8 and 52 weeks post-randomization and symptom outcomes (measured with a numerical rating scale) at 8 and 52 weeks. RESULTS: Overall, the strongest predictors of improvement in back function and symptoms were higher baseline levels of these measures, receipt of an acupuncture treatment, and non-use of narcotic analgesics. Benefit from acupuncture compared to usual care was greater with worse pre-treatment levels of back dysfunction (interaction p < 0.004 for the functional outcome, Roland Morris Disability Scale at 8 weeks). No other consistent interactions were observed. CONCLUSION: This secondary analysis found little evidence for the existence of subgroups of patients with chronic back pain that would be especially likely to benefit from acupuncture. However, persons with chronic low back pain who had more severe baseline dysfunction had the most short-term benefit from acupuncture.

Financial support for research training and career development in complementary and alternative medicine from the National Institutes of Health.

Research careers are a relatively new reality for complementary and alternative medicine (CAM) practitioners (eg, chiropractors, naturopaths, doctors of oriental medicine, etc). Before the establishment in 1998 of the National Center for Complementary and Alternative Medicine (NCCAM) as part of the National Institutes of Health (NIH), there were few funding resources available for those interested in a CAM research career and fewer still feasible paths. Now, however, NCCAM provides a broad array of research training and career development awards for those seeking a long-term career in CAM research. These awards include predoctoral and postdoctoral fellowships, individual career development awards, and institutional training awards. The goal of this article is to provide information about current research training funding opportunities from NCCAM and NIH as a whole that are available to CAM practitioners in the context of the historical challenges of transitioning from a clinical career in CAM practice to a CAM research career.

Biomechanical evaluation of surgical constructs for stabilization of cervical teardrop fractures.

BACKGROUND CONTEXT: Cervical flexion teardrop fractures (CFTF) are highly unstable injuries, and the optimal internal fixation construct is not always clearly indicated. PURPOSE: The purpose of the current study was to determine whether the type of fixation construct (anterior, posterior, or combined) or number of joint levels involved in fixation (one or two) affected the relative stability of a CFTF injury at C5-C6. STUDY DESIGN/SETTING: Human cadaveric cervical spine specimens were mechanically tested under displacement control in the intact state and after creation of CFTF at C5-C6 with stabilization using five different instrumentation constructs. Joint stiffness and intervertebral translation of the constructs were compared with the intact state and normalized (instrumented/intact) to assess relative differences across the five constructs. METHODS: Spine specimens were mechanically tested in the intact state during flexion, extension, lateral bending, and axial rotation. CFTF was created at C5-C6 by creating an osteotomy at C5 and transecting the posterior ligaments and intervertebral disc. Specimens were tested with anterior, posterior, and combined single-level constructs (C5-C6). Then, a corpectomy was performed at C5, and specimens were retested with the two-level constructs (C4-C6; anterior and anterior-posterior). Joint stiffness and intervertebral translations were computed. RESULTS: All five fixation constructs resulted in joint stability that was as good as or better than that of the intact specimens. Relative stiffness of the constructs differed depending upon the motion type considered, though the two-level anterior-posterior construct typically provided the greatest stability. Intervertebral translation along the major axis was reduced the most for both of the combined instrumentation systems, although there were few changes in total intervertebral translation across the five constructs. CONCLUSIONS: All five constructs restored stability comparable to that of the intact specimens. The significance of the relative differences in constructs for the in vivo spine is unclear and warrants further clinical investigation.

The 2005 conference on the biology of manual therapies.

A historic and critically important scientific workshop for all professions involved with manual therapies was held at the National Institutes of Health (NIH) on June 9 and 10, 2005. The conference was jointly sponsored and organized by the NIH and the Canadian Institutes of Health Research and was the first ever national or international research conference to focus on the biologic mechanisms that underlie a broad range of interventions, which can be described as "manual therapies." Leading scientific experts from North America and Europe presented their latest findings and theories related to 5 different areas of science relevant to manual therapies: neuroscience, biomechanics, endocrinology, imaging, and immunology. During the conference, breakout groups composed of scientists, physicians and therapists, and patient advocates were formed in the relevant disciplines. These groups developed consensus statements on key unanswered research questions, which were then submitted back to the conference for comment and approval. The outcomes of this workshop have subsequently been incorporated into a new initiative by the NIH and Canadian Institutes of Health Research for funding research on the biology of manual therapies. This editorial includes presentation summaries and 13 key consensus recommendations relating to mechanisms of action for manual therapies.

Evidence-Based Evaluation of Complementary Health Approaches for Pain Management in the United States.

Although most pain is acute and resolves within a few days or weeks, millions of Americans have persistent or recurring pain that may become chronic and debilitating. Medications may provide only partial relief from this chronic pain and can be associated with unwanted effects. As a result, many individuals turn to complementary health approaches as part of their pain management strategy. This article examines the clinical trial evidence for the efficacy and safety of several specific approaches-acupuncture, manipulation, massage therapy, relaxation techniques including meditation, selected natural product supplements (chondroitin, glucosamine, methylsulfonylmethane, S-adenosylmethionine), tai chi, and yoga-as used to manage chronic pain and related disability associated with back pain, fibromyalgia, osteoarthritis, neck pain, and severe headaches or migraines.

Neural coding of the location and direction of a moving object by a spatially distributed population of mechanoreceptors.

A neural code for the location and direction of an object moving over the fingerpad was constructed from the responses of a population of rapidly adapting type I (RAs) and slowly adapting type I (SAs) mechanoreceptive nerve fibers. The object was either a sphere with a radius of 5 mm or a toroid with radii of 5 mm on the major axis and either 1 or 3 mm on the minor axis. The object was stroked under constant velocity and contact force along eight different linear trajectories. The spatial locations of the centers of activity of the population responses (PLs) were determined from nonsimultaneously recorded responses of 99 RAs and 97 SAs with receptive fields spatially distributed over the fingerpad of the anesthetized monkey. The PL at each moment during each stroke was used as a neural code of object location. The angle between the direction of the trajectory of the PL and mediolateral axis was used to represent the direction of motion of the object. The location of contact between the object and skin was better represented in SA than in RA PLs, regardless of stroke direction or object curvature. The PL representation of stroke direction was linearly related to the actual direction of the object for both RAs and SAs but was less variable for SAs than for RAs. Both the SA and RA populations coded spatial position and direction of motion at acuities similar to those obtained in psychophysical studies in humans.

Comparison of human lumbar facet joint capsule strains during simulated high-velocity, low-amplitude spinal manipulation versus physiological motions.

BACKGROUND CONTEXT: Spinal manipulation (SM) is an effective treatment for low back pain (LBP), and it has been theorized that SM induces a beneficial neurophysiological effect by stimulating mechanically sensitive neurons in the lumbar facet joint capsule (FJC). PURPOSE: The purpose of this study was to determine whether human lumbar FJC strains during simulated SM were different from those that occur during physiological motions. STUDY DESIGN/SETTING: Lumbar FJC strains were measured in human cadaveric spine specimens during physiological motions and simulated SM in a laboratory setting. METHODS: Specimens were tested during displacement-controlled physiological motions of flexion, extension, lateral bending, and axial rotations. SM was simulated using combinations of manipulation site (L3, L4, and L5), impulse speed (5, 20, and 50 mm/s), and pre-torque magnitude (applied at T12 to simulate patient position; 0, 5, 10 Nm). FJC strains and vertebral motions (using six degrees of freedom) were measured during both loading protocols. RESULTS: During SM, the applied loads were within the range measured during SM in vivo. Vertebral translations occurred primarily in the direction of the applied load, and were similar in magnitude regardless of manipulation site. Vertebral rotations and FJC strain magnitudes during SM were within the range that occurred during physiological motions. At a given FJC, manipulations delivered distally induced capsule strains similar in magnitude to those that occurred when the manipulation was applied proximally. CONCLUSIONS: FJC strain magnitudes during SM were within the physiological range, suggesting that SM is biomechanically safe. Successful treatment of patients with LBP using SM may not require precise segmental specificity, because the strain magnitudes at a given FJC during SM do not depend upon manipulation site.

High loading rate during spinal manipulation produces unique facet joint capsule strain patterns compared with axial rotations.

PURPOSE: Lumbar spinal manipulation (SM) is a popular, effective treatment for low back pain but the physiological mechanisms remain elusive. During SM, mechanoreceptors innervating the facet joint capsule (FJC) may receive a novel stimulus, contributing to the neurophysiological benefits of SM. The biomechanics of SM and physiological axial rotations were compared to determine whether speed or loading site affected FJC strain magnitudes or patterns. METHODS: Human lumbar spine specimens were tested during physiological rotations and simulated SM while measuring applied torque, vertebral motion, and FJC strain. During physiological rotations, specimens were actuated at T12 to 20 degrees left and right axial rotation at 2 degrees to 125 degrees per second. During SM simulations, a 7-mm impulse displacement was applied to L3, L4, or L5 at 5 to 50 mm per second. RESULTS: Physiological rotations. Increasing displacement rate resulted in significantly larger torque magnitudes (P < .001), whereas vertebral kinematics and FJC strain magnitudes were unchanged (P > .05). Physiological rotations vs SM. Applied torque and vertebral rotation magnitudes were similar across speed and vertebral level. Total vertebral translations were slightly larger during physiological rotations vs SM at a given loading rate (P < .05). Patterns of vertebral motions and FJC strain during SM and physiological rotations varied significantly with loading rate (P < .05) but not with actuation site (P > .15). CONCLUSIONS: The similar patterns observed in vertebral motion and FJC strain across actuation sites during SM and physiological rotations suggest that site specificity of SM may have minimal clinical relevance. High loading rates during lumbar SM resulted in unique patterns in FJC strain, which may result in unique patterns of FJC mechanoreceptor response.

Biomechanics of musculoskeletal pain: dynamics of the neuromatrix.

Pain, due to mechanical stimuli, is a normal, indeed healthy, response of animals to potential or actual damage to tissues. Mammals in general, and humans in particular, have evolved a highly sophisticated system of pain perception, which is characterized in humans by complementary but distinct neural processing of the intensity and location of a noxious stimulus, and a motivational/emotional or affective response to the stimulus. The peripheral and central neurons that comprise this system, which has been called the 'neuromatrix', dynamically (temporally) respond and adapt to noxious biomechanical stimuli. However, phenotypic variability of the neuromatrix can be large, which can result in a host of musculoskeletal conditions that are characterized by altered pain perception, which can and often does alter the course of the condition. This neural plasticity has been well recognized in the central nervous system, but it has only more recently become known that peripheral nociceptors also adapt to their altered extracellular matrix environment. This work reviews the biomechanics of pain focusing on the relevant stimulus that initiates responses by nociceptors to the cognitive perception of pain.

Human lumbar facet joint capsule strains: I. During physiological motions.

BACKGROUND CONTEXT: The lumbar facet joint capsule is innervated with nociceptors and mechanoreceptors, and is thought to play a role in low back pain as well as to function proprioceptively. PURPOSE: In order to examine the facet capsule's potential proprioceptive role, relationships between intracapsular strain and relative spine position were examined. STUDY DESIGN/SETTING: Lumbar facet joint capsule strains were measured in human cadaveric specimens during displacement-controlled motions. METHODS: Ligamentous lumbar spine specimens (n=7) were potted and actuated without inducing a moment at the point of application. Spines were tested during physiological motions of extension, flexion, left and right lateral bending. Intervertebral angulations (IVA) were measured using biaxial inclinometers mounted on adjacent vertebrae. Joint moments were determined from the applied load at T12 and the respective moment arms. Capsule plane strains were measured by optically tracking the displacements of infrared reflective markers glued to capsule surfaces. Statistical differences (p<.05) in moment, IVA and strain were assessed across facet joint levels using analysis of variance and comparison of linear regressions. RESULTS: The developed moments and IVAs increased monotonically with increasing displacements; the relationships were highly correlated for all four motion types. Although highly variable among specimens, principal strains also increased monotonically in magnitude with increasing displacements during extension and flexion, but were more complex during lateral bending. At a given joint level, the absolute magnitudes of principal strains and IVA were largest during the same motion type. CONCLUSIONS: Distinct patterns in principal strains and IVA were identified during physiological motions, lending biomechanical support to the theory that lumbar facet joint capsules could function proprioceptively.

Human lumbar facet joint capsule strains: II. Alteration of strains subsequent to anterior interbody fixation.

BACKGROUND CONTEXT: In cases of low back pain associated with biomechanical lumbar instability, anterior interbody fixation can be used as a surgical treatment, but its affect on facet joint capsule strains is unknown. PURPOSE: To determine the effect of a single-level anterolateral interbody fixation, the changes in lumbar facet joint capsule strains at the level of and adjacent to the fixation were evaluated. STUDY DESIGN/SETTING: Human cadaveric lumbar spine specimens were tested under displacement control before and after the addition of a single anterior thoracolumbar plate (ATLP) on the L4-L5 motion body. METHODS: Ligamentous lumbar spine specimens (n=7) were potted and actuated before and after fixation of the L4-L5 motion segment with an ATLP in motions of extension, flexion, left and right bending. Joint moments were calculated from the applied load and respective moment arms. Intervertebral angulation was measured using biaxial inclinometers mounted onto adjacent vertebrae. Plane strains of the capsules were measured by optically tracking the displacements of small, infrared reflective markers glued to capsule surfaces. Statistical differences (p<.05) in moment, intervertebral angle and capsular strain were assessed using analysis of variance and comparison of linear regression lines. RESULTS: Fixation resulted in an increase in moment at the three vertebral levels for all motions. There was also an increase in intervertebral angle at L3-L4 and L5-S1, and a decrease in intervertebral angle at L4-L5 for all motions. Plane strains in the L3-L4 and L5-S1 facet capsules increased as a result of the fixation. L4-L5 facet capsules experienced decreased and increased strains ipsilateral and contralateral, respectively, to the instrumentation. CONCLUSION: Restriction of a vertebral motion segment using a single ATLP increased adjacent capsular strains, which if suprathreshold for capsule nociceptors, could play a role in low back pain.

Advances in geroscience: impact on healthspan and chronic disease.

Population aging is unprecedented, without parallel in human history, and the 21st century will witness even more rapid aging than did the century just past. Improvements in public health and medicine are having a profound effect on population demographics worldwide. By 2017, there will be more people over the age of 65 than under age 5, and by 2050, two billion of the estimated nine billion people on Earth will be older than 60 (http://unfpa.org/ageingreport/). Although we can reasonably expect to live longer today than past generations did, the age-related disease burden we will have to confront has not changed. With the proportion of older people among the global population being now higher than at any time in history and still expanding, maintaining health into old age (or healthspan) has become a new and urgent frontier for modern medicine. Geroscience is a cross-disciplinary field focused on understanding the relationships between the processes of aging and age-related chronic diseases. On October 30-31, 2013, the trans-National Institutes of Health GeroScience Interest Group hosted a Summit to promote collaborations between the aging and chronic disease research communities with the goal of developing innovative strategies to improve healthspan and reduce the burden of chronic disease.

Comparison of yoga versus stretching for chronic low back pain: protocol for the Yoga Exercise Self-care (YES) trial.

BACKGROUND: Back pain, one of the most prevalent conditions afflicting American adults, is the leading reason for using complementary and alternative medicine (CAM) therapies. Yoga is an increasingly popular "mind-body" CAM therapy often used for relieving back pain and several small studies have found yoga effective for this condition. This study will assess whether yoga is effective for treating chronic low back pain compared with self care and exercise and will explore the mechanisms responsible for any observed benefits. METHODS/DESIGN: A total of 210 participants with low back pain lasting at least 3 months will be recruited from primary care clinics of a large healthcare system based in Seattle. They will be randomized in a 2:2:1 ratio to receive 12 weekly yoga classes, 12 weekly conventional therapeutic exercise classes of comparable physical exertion, or a self-care book. Interviewers masked to participants' treatment group will assess outcomes at baseline and 6, 12 and 26 weeks after randomization. Primary outcomes will be back-related dysfunction and symptom bothersomeness. In addition, data will be collected on physical measurements (e.g., flexion) at baseline and 12 weeks and saliva samples will be obtained at baseline, 6 and 12 weeks. Information will be collected on specific physical, psychological, and physiological factors to allow exploration of possible mechanisms of action through which yoga could relieve back pain and dysfunction. The effectiveness of yoga will be assessed using analysis of covariance (using general estimating equations - GEE) within an intention-to-treat context. If yoga is found effective, further analyses will explore whether yoga's benefits are attributable to physical, psychological and/or physiological factors. CONCLUSIONS: This study will provide the clearest evidence to date about the value of yoga as a therapeutic option for treating chronic back pain, and if the results are positive, will help focus future, more in-depth, research on the most promising potential mechanisms of action identified by this study.

Treatment expectations and preferences as predictors of outcome of acupuncture for chronic back pain.

STUDY DESIGN: Preplanned secondary analysis of data from participants receiving acupuncture in a randomized clinical trial. OBJECTIVE: To determine whether patients' expectations of and preferences for acupuncture predict short and long-term treatment outcomes for persons with chronic back pain. SUMMARY OF BACKGROUND DATA: Although accumulating evidence suggests that patient expectations and treatment preferences may predict treatment outcomes, few studies have examined this relationship for acupuncture. METHODS: Four hundred seventy-seven acupuncture-naïve participants with chronic low back pain who were randomized to 1 of 3 acupuncture or simulated acupuncture treatments were the focus of this analysis. Ten treatments were provided during a 7-week period, and participants were masked to treatment assignment. Before randomization, participants provided expectations regarding treatment success, impressions, and knowledge about acupuncture and treatment preferences. Outcomes of interest were functional status (Roland score) and symptom bothersomeness at 8 and 52 weeks postrandomization, obtained by telephone interviewers masked to treatment assignment. RESULTS: Persons with high pretreatment expectations for the success of acupuncture were more likely to report greater general expectations for improvement, a preference for acupuncture, having heard acupuncture was a very effective treatment and having a very or moderately positive impression of acupuncture. However, none of these variables was a significant predictor of improvement in back-related symptoms or function at 8 or 52 weeks. After 1 treatment, participants' revised expectations of treatment success were only associated with back-symptoms at the end of treatment. After 5 treatments, revised expectation of success was predictive of both symptoms and function at 8 and 52 weeks. CONCLUSION: Pretreatment expectations and preferences for acupuncture were not found predictive of treatment outcomes for patients with chronic back pain. These results differ from previous studies evaluating acupuncture for chronic back pain. These inconsistent results suggest that the relationship between expectations and outcomes may be more complex than previously believed.

Determination of torque-limits for human and cat lumbar spine specimens during displacement-controlled physiological motions.

BACKGROUND CONTEXT: Quadruped animal models have been validated and used as biomechanical models for the lumbar spine. The biomechanics of the cat lumbar spine has not been well characterized, even though it is a common model used in neuromechanical studies. PURPOSE: Compare the physiological ranges of motion and determine torque-limits for cat and human lumbar spine specimens during physiological motions. STUDY DESIGN/SETTING: Biomechanics study. PATIENT SAMPLE: Cat and human lumbar spine specimens. OUTCOME MEASURES: Intervertebral angle (IVA), joint moment, yield point, torque-limit, and correlation coefficients. METHODS: Cat (L2-sacrum) and human (T12-sacrum) lumbar spine specimens were mechanically tested to failure during displacement-controlled extension (E), lateral bending (LB), and axial rotation (AR). Single trials consisted of 10 cycles (10mm/s or 5 degrees /s) to a target displacement where the magnitude of the target displacement was increased for subsequent trials until failure occurred. Whole-lumbar stiffness, torque at yield point, and joint stiffness were determined. Scaling relationships were established using equations analogous to those that describe the load response of elliptically shaped beams. RESULTS: IVA magnitudes for cat and human lumbar spines were similar during physiological motions. Human whole-lumbar and joint stiffness magnitudes were significantly greater than those for cat spine specimens (p<.05). Torque-limits were also greater for humans compared with cats. Scaling relationships with high correlation (R(2) greater than 0.77) were established during later LB and AR. CONCLUSIONS: The current study defined "physiological ranges of movement" for human and cat lumbar spine specimens during displacement-controlled testing, and should be observed in future biomechanical studies conducted under displacement control.