Cerebrospinal fluid and plasma oxytocin concentrations are positively correlated and negatively predict anxiety in children.

The neuropeptide oxytocin (OXT) exerts anxiolytic and prosocial effects in the central nervous system of rodents. A number of recent studies have attempted to translate these findings by investigating the relationships between peripheral (e.g., blood, urinary and salivary) OXT concentrations and behavioral functioning in humans. Although peripheral samples are easy to obtain in humans, whether peripheral OXT measures are functionally related to central OXT activity remains unclear. To investigate a possible relationship, we quantified OXT concentrations in concomitantly collected cerebrospinal fluid (CSF) and blood samples from child and adult patients undergoing clinically indicated lumbar punctures or other CSF-related procedures. Anxiety scores were obtained in a subset of child participants whose parents completed psychometric assessments. Findings from this study indicate that plasma OXT concentrations significantly and positively predict CSF OXT concentrations (r=0.56, P=0.0064, N=27). Moreover, both plasma (r=-0.92, P=0.0262, N=10) and CSF (r=-0.91, P=0.0335, N=10) OXT concentrations significantly and negatively predicted trait anxiety scores, consistent with the preclinical literature. Importantly, plasma OXT concentrations significantly and positively (r=0.96, P=0.0115, N=10) predicted CSF OXT concentrations in the subset of child participants who provided behavioral data. This study provides the first empirical support for the use of blood measures of OXT as a surrogate for central OXT activity, validated in the context of behavioral functioning. These preliminary findings also suggest that impaired OXT signaling may be a biomarker of anxiety in humans, and a potential target for therapeutic development in individuals with anxiety disorders.

Bilateral Upper-Extremity Acute Exertional Compartment Syndrome: A Case Report.

Introduction: Acute exertional compartment syndrome (AECS) is a condition with the potential for devastating outcomes if not promptly treated. Physicians must maintain a high index of suspicion when evaluating patients presenting with pain, swelling, decreased range of motion, and numbness within a muscle compartment. However, AECS is frequently misdiagnosed due to a multitude of factors, leading to a delay in treatment. In this case report, we would like to shed light on a rare case of bilateral upper-extremity AECS and suggest the treatment paradigm we believe will help prevent negative outcomes. Case Report: A previously healthy 33-year-old male presented with bilateral weakness, tingling, tenderness, swelling, and pain upon movement in the trapezius and deltoid muscles. The symptoms started after he performed "burpees" for 18 h following a 12-h forest-fire firefighting shift. The patient's rapidly developing clinical presentation warranted compartmental pressure checks for suspicion of AECS. Being able to quickly determine the elevated trapezius, deltoid, and supraspinatus compartmental pressures allowed us to perform immediate bilateral fasciotomies with delayed primary closure to relieve compartment pressure. Conclusion: The delay in treatment for patients presenting with AECS is multifactorial and may lead to devastating outcomes if not promptly addressed. The lack of literature regarding bilateral upper-extremity AECS makes the treatment for this condition even more difficult. For our patient, having a proper criterion for performing compartmental pressure checks played a vital role in ensuring an accurate diagnosis and timely medical intervention.

Prognostic role for diffusion-weighted imaging of pediatric optic pathway glioma.

Optic pathway glioma (OPG) has an unpredictable course, with poor correlation between conventional imaging features and tumor progression. We investigated whether diffusion-weighted MRI (DWI) predicts the clinical behavior of these tumors. Twelve children with OPG (median age 2.7 years; range 0.4-6.2 years) were followed for a median 4.4 years with DWI. Progression-free survival (time to requiring therapy) was compared between tumors stratified by apparent diffusion coefficient (ADC) from initial pre-treatment scans. Tumors with baseline ADC greater than 1,400 × 10(-6) mm(2)/s required treatment earlier than those with lower ADC (log-rank p = 0.002). In some cases, ADC increased leading up to treatment, and declined following treatment with surgery, chemotherapy, or radiation. Baseline ADC was higher in tumors that eventually required treatment (1,562 ± 192 × 10(-6) mm(2)/s), compared with those conservatively managed (1,123 ± 114 × 10(-6) mm(2)/s) (Kruskal-Wallis test p = 0.013). Higher ADC predicted earlier tumor progression in this cohort and in some cases declined after therapy. Evaluation of OPG with DWI may therefore be useful for predicting tumor behavior and assessing treatment response.

A Resident-Driven Mobile Evaluation System Can Be Used to Augment Traditional Surgery Rotation Evaluations.

BACKGROUND: The Accreditation Council for Graduate Medical Education requires residents to receive milestone-based evaluations in key areas. Shortcomings of the traditional evaluation system (TES) are a low completion rate and delay in completion. We hypothesized that adoption of a mobile evaluation system (MES) would increase the number of evaluations completed and improve their timeliness. METHODS: Traditional evaluations for a general surgery residency program were converted into a web-based form via a widely available, free, and secure application and implemented in August 2017. After 8 months, MES data were analyzed and compared to that of our TES. RESULTS: 122 mobile evaluations were completed; 20% were solicited by residents. Introduction of the MES resulted in an increased number of evaluations per resident (P = .0028) and proportion of faculty completing evaluations (P = .0220). Timeliness also improved, with 71% of evaluations being completed during one's clinical rotation. CONCLUSIONS: A resident-driven MES is an inexpensive and effective method to augment traditional end-of-rotation evaluations.

Resident Endoscopy Experience Correlates Poorly with Performance on a Virtual Reality Simulator.

Background Endoscopy training has become increasingly emphasized during general surgery residency as reflected by introduction of the Fundamentals of Endoscopic Surgery (FES) examination, which includes testing of skills on virtual reality (VR) simulators. Although studies exist to assess the ability of the simulator to differentiate between novices and experienced endoscopists, it is not well understood how simulators can differentiate skills among resident cohort. Objective To assess the utility of the VR simulator, we evaluated the correlation between resident endoscopy experience and performance on two VR simulator colonoscopy modules on the GI-BRONCH Mentor (Simbionix Ltd, Airport City, Israel). Methods Postgraduate years 2 to 5 residents completed "easy" and "difficult" VR colonoscopies, and performance metrics were recorded from October 2017 to February 2018 at Rutgers' two general surgery residency programs. Resident endoscopy experience was obtained through Accreditation Council for Graduate Medical Education case logs. Correlations between resident endoscopy experience and VR colonoscopy performance metrics were assessed using Spearman's rho (ρ) correlation statistic and bivariate logistic regression. Results Fifty-five residents out of 65 (84.6%) eligible participants completed the study. There were limited correlations found between resident endoscopy experience and FES performance metrics and no correlations were found between resident endoscopy experience and binary metrics of colonoscopy-ability to complete colonoscopy, ability to retroflex, and withdrawal time of less than 6 minutes. Conclusion The VR simulator may have a limited ability to discriminate between experience levels among resident cohort. Future studies are needed to further understand how well the VR simulator metrics correlate with resident endoscopy experience.

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.