Data-driven identification of distinct pain drawing patterns and their association with clinical and psychological factors: a study of 21,123 patients with spinal pain.

ABSTRACT: The variability in pain drawing styles and analysis methods has raised concerns about the reliability of pain drawings as a screening tool for nonpain symptoms. In this study, a data-driven approach to pain drawing analysis has been used to enhance the reliability. The aim was to identify distinct clusters of pain patterns by using latent class analysis (LCA) on 46 predefined anatomical areas of a freehand digital pain drawing. Clusters were described in the clinical domains of activity limitation, pain intensity, and psychological factors. A total of 21,123 individuals were included from 2 subgroups by primary pain complaint (low back pain (LBP) [n = 15,465]) or midback/neck pain (MBPNP) [n = 5658]). Five clusters were identified for the LBP subgroup: LBP and radiating pain (19.9%), radiating pain (25.8%), local LBP (24.8%), LBP and whole leg pain (18.7%), and widespread pain (10.8%). Four clusters were identified for the MBPNP subgroup: MBPNP bilateral posterior (19.9%), MBPNP unilateral posterior + anterior (23.6%), MBPNP unilateral posterior (45.4%), and widespread pain (11.1%). The clusters derived by LCA corresponded to common, specific, and recognizable clinical presentations. Statistically significant differences were found between these clusters in every self-reported health domain. Similarly, for both LBP and MBPNP, pain drawings involving more extensive pain areas were associated with higher activity limitation, more intense pain, and more psychological distress. This study presents a versatile data-driven approach for analyzing pain drawings to assist in managing spinal pain.

Patient satisfaction with clinical services provided by chiropractic students under supervision compared to licensed chiropractors: An observational study.

OBJECTIVE: This study investigated patient satisfaction with care provided by chiropractic students under supervision vs supervisors in a Danish hospital setting. METHODS: A cross-sectional observational study of patient satisfaction was conducted at the Spine Center of Southern Denmark, where chiropractic students from the University of Southern Denmark complete an 8-week internship in their final year of pregraduate training. Patients were assigned to students or supervisors based on administrative convenience (ie, natural allocation). Blinded from the aim of the study, all patients seen by a chiropractor (with or without a student) were invited to answer a questionnaire rating satisfaction with the clinical encounter. Results were analyzed using ordinal logistic regression with group allocation blinded by the investigators. RESULTS: Results from 438 participants (response rate = 88%) showed no significant difference in patient satisfaction between the student and supervisor groups. Although a small difference favored the supervisor group, the student group had a higher proportion of high and very high satisfaction combined. CONCLUSION: Satisfaction differed minimally whether patient care was administered by students under the supervision of a licensed chiropractor or by licensed chiropractors alone. Our findings suggest that patients do not negatively view student involvement in clinical consultations at a Danish hospital.

A new role for spinal manual therapy and for chiropractic? Part II: strengths and opportunities.

In a previous paper, we presented some important weaknesses of and threats to the chiropractic profession as we see them. We further argued that the chiropractic profession's relationship with its principal clinical tool (spinal manual therapy) is at the core of the ideological divide that fractures the profession and prevents professional development towards greater integration in the healthcare landscape. In this manuscript, we shall argue that the historical predilection for spinal manipulation also gifts the profession with some obvious strengths and opportunities, and that these are inextricably linked to the management of musculoskeletal disorders. The onus is now on the chiropractic profession itself to redefine its raison d'être in a way that plays to those strengths and delivers in terms of the needs of patients and the wider healthcare system/market. We suggest chiropractors embrace and cultivate a role as coordinators of long-term and broad-focused management of musculoskeletal disorders. We make specific recommendations about how the profession, from individual clinicians to political organizations, can promote such a development.

Walking performance in individuals with lumbar spinal stenosis- possible outcome measures and assessment of known-group validity.

BACKGROUND CONTEXT: One of the primary goals of treatments received by individuals with lumbar spinal stenosis with neurogenic claudication is to improve walking ability. Thus, a thorough and valid assessment of walking ability in patients with lumbar spinal stenosis is needed. Duration of continuous walking and steps per day could be relevant when evaluating walking ability in daily living. PURPOSE: To describe and evaluate a method for estimating continuous walking periods in daily living and to evaluate the known-group validity of steps per day in individuals with lumbar spinal stenosis. STUDY DESIGN: This is a cross-sectional observational study. PATIENT SAMPLE: The study contains three study groups: individuals with lumbar spinal stenosis, individuals with low back pain, and a background population from the Lolland-Falster Health Study (LOFUS). OUTCOME MEASURES: Participants in all three study groups wore an accelerometer on the thigh for seven days. METHODS: Accelerometer data were processed to summarize the continuous walking periods according to their length: the number of short (4-9 seconds), moderate (10-89 seconds), and extended (≥90 seconds) continuous walking periods per day, and the number of steps per day. Results from the three groups were compared using negative binomial regression with lumbar spinal stenosis as the reference level. RESULTS: Continuous walking periods of moderate length were observed 1.48 (95% CI 1.27, 1.72) times more often in individuals from the background population than in individuals with LSS. Continuous walking periods of extended length were observed 1.53 (95% CI 1.13, 2.06) times more often by individuals with low back pain and 1.60 (95% CI 1.29, 1.99) times more often by individuals from the background population. The number of steps per day was 1.22 (95% CI 1.03, 1.46) times larger in individuals with LBP and 1.35 (95% CI 1.20, 1.53) times larger in individuals from background population. CONCLUSIONS: The impact of neurogenic claudication on walking ability in daily living seems possible to describe by continuous walking periods along with steps per day. The results support known-group validity of steps per day. This is the next step toward a clinically relevant and comprehensive assessment of walking in daily living in individuals with lumbar spinal stenosis.

A new role for spinal manual therapy and for chiropractic? Part I: weaknesses and threats.

Spinal manual therapy is central to chiropractic history, clinical practice, and professional identity. That chiropractors have developed an expertise in this domain has provided some considerable advantages. However, we contend it is also at the crux of the ideological schism that fractures the chiropractic profession. In this article, which is the first in a series of two, we discuss chiropractors' understanding and use of spinal manual therapy and do so with particular emphasis on what we see as weaknesses it creates and threats it gives rise to. These are of particular importance, as we believe they have limited the chiropractic profession's development. As we shall argue, we believe that these threats have become existential in nature, and we are convinced that they call for a resolute and unified response by the profession. Subsequently, in part II, we discuss various strengths that the chiropractic profession possesses and the opportunities that await, provided that the profession is ready to rise to the challenge.

Validation of a spring loaded probe for single and repeat pressure pain testing, including public domain specifications for design and manufacture.

Temporal summation of pressure pain is technically more challenging than simple pressure pain thresholds. The current study describes the design, manufacture and validation of a simple mechanical test apparatus to assess the temporal summation of deep pressure pain. We release design details into the public domain with the intention of providing free access for researchers especially in low income countries. Utility and validity of the probes were assessed by pressure application in three different experimental setups: A. Identifying potential issues which needed to be addressed to ensure a reliable test procedure (189 tests with 24 testers using four different probes). B. Selecting the most reliable target force curve (one tester conducted 20 tests). C. Estimating classic inter and intra-examiner reliability and comparing probe measures to other QST measures (repeated measures study with counterbalancing). We make recommendations on best use of the probes. Pressure pain thresholds assessed using probes were affected by anatomical test site and testing tool, but not by tester, day or session. Temporal summation of pressure pain was significantly greater than that of a single pressure application. We found no correlation between temporal summation using the probes on the Infra-Spinatus muscle and temporal summation using a pneumatic cuff on the lower leg. The probe was a useful tool for assessing pain intensity and temporal summation of pressure pain intensity, but not for pain thresholds. A number of caveats need to be considered when using the probe, including but not limited to audio cues and target ideal wave function.

Testing walking performance in patients with low back pain: will two minutes do instead of six minutes?

PURPOSE: The six-minute walk test (6MWT) can assess walking function but is time-consuming. We investigate the correlation of performance over the first two minutes of the 6MWT (2MWT#) and the 6MWT. We also evaluate the 2MWT#'s ability to predict 6MWT results, assess correlations to secondary explanatory outcomes, and assess the ability to discriminate between clinical subgroups. MATERIAL AND METHODS: A cross-sectional study of 124 participants with LBP. Correlations between the 2MWT# and 6MWT and secondary outcomes were evaluated using the Pearson product-moment correlation coefficient. The predictive ability of the 2MWT# was defined as the residual distance between the observed 6MWT and three times the 2MWT#. Differences between clinical subgroups were evaluated using the Wilcoxon rank test. RESULTS: The 2MWT# and 6MWT correlated highly (r = 83, 95% CI 0.76 - 0.87). The 2MWT# overestimated 6MWT results with 46.8 meters (SD 67.0). Both tests correlated with secondary outcomes and discriminated similarly between clinical subgroups. CONCLUSIONS: The 2MWT# correlates highly with 6MWT but overestimates the observed 6MWT by 9%. Because it is shorter, possibly less burdensome, and with little or no loss of discriminatory ability, we consider it a legitimate alternative to the 6MWT in patients with LBP.Implications for rehabilitationWalking function is often affected in patients with low back pain (LBP).The six-minute walk test (6MWT) is frequently used to assess walking function but is time-consuming.A shorter two-minute walk test is a legitimate alternative in patients with LBP as it correlates highly with the 6MWT and has little or no loss of discriminatory ability between clinical subgroups.

Multidisciplinary team-based management approach for secondary-care patients with severe and persistent low back pain: A mixed-method feasibility trial.

BACKGROUND: Persistent and severe low back pain is challenging to treat. Multidisciplinary care with systematic follow-up may be more effective than usual care. However, such a model has yet to be developed and tested. OBJECTIVE: Our objectives were to develop and test the feasibility of a three-month multidisciplinary intervention with systematic follow-up in a specialized hospital spine center for patients with severe and persistent low back pain. METHODS: Using the Medical Research Council and National Institute for Health and Care Research framework for the development and testing of complex interventions, we developed a multidisciplinary intervention with systematic follow-up and tested its feasibility, using a-priori-determined outcomes during three months for 24 patients seen at a regional diagnostic spine center unit. As part of the evaluation, we conducted semi-structured interviews with participants and a focus-group interview with clinicians. RESULTS: Of the 24 patients included, only 17 completed the course of care and provided complete data for feasibility assessment. We failed to reach our a-priori feasibility outcomes, had difficulty with inclusion, and participants did not find the intervention effective or satisfactory. CONCLUSIONS: The intervention was not feasible as barriers existed on multiple levels (e.g., clinical, administrative, and patient). Excessive study moderations must be made before the intervention is feasible in a randomized trial.

No effect of social interaction on experimental pain sensitivity: a randomized experimental study.

ABSTRACT: Quantitative sensory testing (QST) is a commonly applied paradigm to investigate pain, which is a subjective experience influenced by a myriad of social and contextual factors. Therefore, it is important to consider the potential sensitivity of QST to the test setting and the social interaction that naturally is a part of it. This may particularly be the case in clinical settings where patients have something at stake. Therefore, we investigated differences in pain responses using QST in different test setups with varying degrees of human interaction. In a parallel three-armed randomized experimental study, we included 92 participants with low back pain and 87 healthy volunteers allocated to 1 of the 3 QST setups: 1 setup with manual tests performed by a human tester, 1 setup with automated tests performed by a robot and orally guided by a human tester, and 1 setup with automated tests performed solely by a robot without social interaction with a human tester. All 3 setups consisted of the same pain tests in the same order, including pressure pain threshold and cold pressor tests. We found no statistically significant differences between setups on the primary outcome of conditioned pain modulation nor any secondary QST outcomes. While this study is not without limitations, the results indicate that QST procedures are robust enough not to be influenced by social interaction to an appreciable degree.

Temporal stability and responsiveness of a conditioned pain modulation test.

OBJECTIVES: Conditioned pain modulation is a commonly used quantitative sensory test, measuring endogenous pain control. The temporal stability of the test is questioned, and there is a lack of agreement on the effect of different pain conditions on the conditioned pain modulation response. Thus, an investigation of the temporal stability of a conditioned pain modulation test among patients suffering from persistent or recurrent neck pain is warranted. Further, an investigation into the difference between patients experiencing a clinically important improvement in pain and those not experiencing such an improvement will aid the understanding between changes in pain and the stability of the conditioned pain modulation test. METHODS: This study is based on a randomized controlled trial investigating the effect of home stretching exercises and spinal manipulative therapy vs. home stretching exercises alone. As no difference was found between the interventions, all participants were studied as a prospective cohort in this study, investigating the temporal stability of a conditioned pain modulation test. The cohort was also divided into responders with a minimally clinically important improvement in pain and those not experiencing such an improvement. RESULTS: Stable measurements of conditioned pain modulation were observed for all independent variables, with a mean change in individual CPM responses of 0.22 from baseline to one week with a standard deviation of 1.34, and -0.15 from the first to the second week with a standard deviation of 1.23. An Intraclass Correlation Coefficient (ICC3 - single, fixed rater) for CPM across the three time points yielded a coefficient of 0.54 (p<0.001). CONCLUSIONS: Patients with persistent or recurrent neck pain had stable CPM responses over a 2 week course of treatment irrespective of clinical response.

A simple, bed-side tool to assess evoked pressure pain intensity.

OBJECTIVES: Existing equipment for quantitative sensory testing is generally expensive and not easily applicable in a clinical setting thus simple bed-side devices are warranted. Pressure hyperalgesia is a common finding in patients with musculoskeletal pain and an experimental model is delayed-onset muscle soreness (DOMS). DOMS is characterised by muscle hyperalgesia and some studies report facilitation of temporal summation of pain. This study aimed to detect DOMS induced muscle hyperalgesia and temporal summation of pain using a newly developed bed-side quantitative sensory testing device to deliver standardised pressure. METHODS: Twenty-two healthy participants participated in two sessions with the second session approximately 48 h after baseline. Pressure pain intensities were assessed from the gastrocnemius muscle with four probes calibrated to apply 2, 4, 6 and 8 kg, respectively. Temporal summation of pain (10 stimuli delivered at 0.5 Hz using the 6 kg probe) intensities were assessed from the same location. DOMS was evoked in the gastrocnemius muscle by an eccentric exercise. Sleepiness and physical activity were measured with the Epworth Sleepiness Scale and the Global Physical Activity Questionnaire to investigate if they were associated with the quantitative sensory testing measures. RESULTS: Pressure pain intensity was significantly increased 48 h after induction of DOMS when compared to baseline for all four probes (p<0.05). Temporal summation of pain was not statistically significant affected by DOMS and sleep quality and physical activity did not associate with any of the measures. CONCLUSIONS: This study introduces a simple, bed-side assessment tool for the assessment of pressure pain intensity and hence hyperalgesia and temporal summation of pain.

Are changes in pain associated with changes in heart rate variability in patients treated for recurrent or persistent neck pain?

BACKGROUND: Persistent or recurrent neck pain is associated with perturbations in the autonomic nervous system balance, and nociceptive stimulation has been seen to influence this balance. However, very few prospective studies have addressed the extent to which changes in pain associate with changes in autonomic cardiac regulation. Therefore, we investigated if changes in pain vary with changes in heart rate variability in a cohort of patients treated for persistent or recurrent neck pain. METHOD: This analysis is based on data from a randomized controlled trial in which participants were given home stretching exercises with or without spinal manipulative therapy for two weeks. As the effectiveness of the intervention (home stretching exercises and spinal manipulative therapy) was found to be equal to the control (home stretching exercises alone), all 127 participants were studied as one cohort in this analysis. During the intervention, pain levels were recorded using daily text messages, and heart rate variability was measured in the clinics three times over two weeks. Two approaches were used to classify patients based on changes in pain intensity: 1) Clinically important changes in pain were categorized as either "improved" or "not improved" and, 2) Pain development was measured using pain trajectories, constructed in a data driven approach. The association of pain categories and trajectories with changes in heart rate variability indices over time were then analysed using linear mixed models. RESULTS: Heart rate variability did not differ significantly between improved and not-improved patients, nor were there any associations with the different pain trajectories. CONCLUSIONS: In conclusion, changes in pain after home stretching exercises with or without spinal manipulative therapy over two weeks were not significantly associated with changes in heart rate variability for patients with persistent or recurrent neck pain. Future studies should rely on more frequent measurements of HRV during longer treatment periods. TRIAL REGISTRATION: The trial was registered at ClinicalTrials.gov, registration number: NCT03576846.

Pressure pain thresholds in a real-world chiropractic setting: topography, changes after treatment, and clinical relevance?

BACKGROUND: Changes in pain sensitivity are a commonly suggested mechanism for the clinical effect of spinal manipulative therapy (SMT). Most research has examined pressure pain thresholds (PPT) and has primarily been conducted in controlled experimental setups and on asymptomatic populations. Many important factors are likely to differ between research and clinical settings, which may affect PPT changes following SMT. Therefore, we planned to investigate PPT before and after clinical chiropractic care and investigate relationships with various potentially clinically-relevant factors. METHODS: We recruited participants from four Danish chiropractic clinics between May and August 2021. A total of 129 participants (72% of the invited) were included. We measured PPT at eight pre-determined test sites (six spinal and two extra-spinal) immediately before (pre-session) and immediately after (post-session) the chiropractic consultation. We used regression analyses to investigate PPT changes, including the following factors: (i) vertebral distance to the nearest SMT site, (ii) rapid clinical response, (iii) baseline PPT, (iv) number of SMTs performed, (v) at the region of clinical pain compared to other regions, and (vi) if other non-SMT treatment was provided. We also performed topographic mapping of pre-session PPTs. RESULTS: After the consultation, there was a non-significant mean increase in PPT of 0.14 kg (95% CIs = - 0.01 to 0.29 kg). No significant associations were found with the distance between the PPT test site and nearest SMT site, the clinical response of participants to treatment, the pre-session PPT, the total number of SMTs performed, or the region/s of clinical pain. A small increase was observed if myofascial treatment was also provided. Topographic mapping found greater pre-session PPTs in a caudal direction, not affected by the region/s of clinical pain. CONCLUSIONS: This study of real-world chiropractic patients failed to demonstrate a substantial local or generalized increase in PPT following a clinical encounter that included SMT. This runs counter to prior laboratory research and questions the generalizability of highly experimental setups investigating the effect of SMT on PPT to clinical practice.

"Convergent validity of the central sensitization inventory and experimental testing of pain sensitivity".

OBJECTIVES: The aim of the current study was to examine the convergent validity of the Central Sensitization Inventory by quantifying the correlation with experimental measures of pain sensitivity and self-reported psycho-social questionnaires, in a low back pain population. METHODS: All participants were recruited from an outpatient hospital spine care clinic (Spine Centre of Southern Denmark). Participants underwent a standardized experimental pain test protocol and completed the Central Sensitization Inventory (CSI) along with additional self-reported questionnaires to assess psycho-social constructs across different domains. The association between the CSI, experimental pain measures and other self-reported psycho-social questionnaires were analyzed using correlation and contingency tests. ROC-curve analysis was used to determine sensitivity and specificity for CSI. RESULTS: One hundred sixty-eight (168) participants were included. The CSI was weakly correlated with nine out of 20 variables in the experimental pain test protocol (rho range -0.37 to 0.22). The CSI was more closely correlated with psycho-social factors such as work ability, disability, and symptoms of exhaustion disorder. ROC-analysis identified an optimal cut-point of 44 on CSI (Sn=39.1% Sp=87.4%). The CSI had an area under the ROC curve of 0.656. Fisher's exact test demonstrated a statistically significant association between participants scoring ≥40 on CSI and participants categorized as sensitized by experimental pain tests (p-value=0.03). CONCLUSIONS: Our findings are consistent with previous studies, indicating that the CSI is related to psycho-social constructs. However, the convergent validity with experimental pain measures is small and probably not clinically meaningful.

The importance of selecting the correct site to apply spinal manipulation when treating spinal pain: Myth or reality? A systematic review.

The concept that spinal manipulation therapy (SMT) outcomes are optimized when the treatment is aimed at a clinically relevant joint is commonly assumed and central to teaching and clinical use (candidate sites). This systematic review investigated whether clinical effects are superior when this is the case compared to SMT applied elsewhere (non-candidate sites). Eligible study designs were randomized controlled trials that investigated the effect of spinal manipulation applied to candidate versus non-candidate sites for spinal pain. We obtained data from four different databases. Risk of bias was assessed using an adjusted Cochrane risk of bias tool, adding four items for study quality. We extracted between-group differences for any reported outcome or, when not reported, calculated effect sizes from the within-group changes. We compared outcomes for SMT applied at a 'relevant' site to SMT applied elsewhere. We prioritized methodologically robust studies when interpreting results. Ten studies, all of acceptable quality, were included that reported 33 between-group differences-five compared treatments within the same spinal region and five at different spinal regions. None of the nine studies with low or moderate risk of bias reported statistically significant between-group differences for any outcome. The tenth study reported a small effect on pain (1.2/10, 95%CI - 1.9 to - 0.5) but had a high risk of bias. None of the nine articles of low or moderate risk of bias and acceptable quality reported that "clinically-relevant" SMT has a superior outcome on any outcome compared to "not clinically-relevant" SMT. This finding contrasts with ideas held in educational programs and clinical practice that emphasize the importance of joint-specific application of SMT.

Digging deeper: exploring chiropractors online claims about non-musculoskeletal disorders.

BACKGROUND: Some chiropractors suggest that chiropractic treatment is appropriate for health issues other than musculoskeletal problems. The prevalence of such claims on individual clinic websites has previously been reported as approximately one-in-four in Denmark. The underlying rationales for such claims may reflect convictions about traditional chiropractic subluxations paradigms, but are not self-evident and has not previously been studied. METHODS: An exploratory qualitative case interview study of Danish chiropractors with websites which contain claims about chiropractic efficacy in the treatment of non-musculoskeletal disorders. Websites were identified from a nation wide random sample (57%) of all chiropractic clinic websites. RESULTS: Of the original 139 websites, 36 were identified as mentioning non-MSK conditions. When revisited, 19 of those clinic websites still mentioned non-MSK disorders and were contacted. Eleven (11) declined our invitation to participate. Interviews were conducted with the responsible chiropractor from each of the remaining 8 clinics. Five distinct themes were identified in the rationales for treating non-musculoskeletal disorders: 'Positive side-effects,' 'Experience,' 'Web page,' 'Communication' and 'Conviction.' CONCLUSIONS: A minority of Danish chiropractic websites suggest that non-musculoskeletal disorders are within the chiropractic scope of practice. Those that do, do so for varying reasons-poor communication and website maintenance were commonly cited problems. An explicitly stated adherence to traditional chiropractic subluxations concepts was uncommon. By contrast, a more tempered rationale that suggested a potential beneficial side-effect of chiropractic on non-musculoskeletal health issues were more common and was typically presented in softer-language and/or with some reservations.

The effect of two weeks of spinal manipulative therapy and home stretching exercises on pain and disability in patients with persistent or recurrent neck pain; a randomized controlled trial.

BACKGROUND: Recurrent or persistent neck pain affects a vast number of people globally, leading to reduced quality of life and high societal costs. Clinically, it is a difficult condition to manage, and treatment effect sizes are often moderate at best. Activity and manual therapy are first-line treatment options in current guidelines. We aimed to investigate the combination of home stretching exercises and spinal manipulative therapy in a multicentre randomized controlled clinical trial, carried out in multidiscipline ary primary care clinics. METHODS: The treatment modalities utilized were spinal manipulative therapy and home stretching exercises compared to home stretching exercises alone. Both groups received 4 treatments for 2 weeks. The primary outcome was pain, where the subjective pain experience was investigated by assessing pain intensity (NRS - 11) and the quality of pain (McGill Pain Questionnaire). Neck disability and health status were secondary outcomes, measured using the Neck Disability Indexthe EQ-5D, respectively. One hundred thirty-one adult subjects were randomized to one of the two treatment groups. All subjects had experienced persistent or recurrent neck pain the previous 6 months and were blinded to the other group intervention. The clinicians provided treatment for subjects in both group and could not be blinded. The researchers collecting data were blinded to treatment allocation, as was the statistician performing data analyses. An intention-to-treat analysis was used. RESULTS: Sixty-six subjects were randomized to the intervention group, and sixty-five to the control group. For NRS - 11, a B-coefficient of - 0,01 was seen, indication a 0,01 improvement for the intervention group in relation to the control group at each time point with a p-value of 0,305. There were no statistically significant differences between groups for any of the outcome measures. CONCLUSION: Based on the current findings, there is no additional treatment effect from adding spinal manipulative therapy to neck stretching exercises over 2 weeks for patients with persistent or recurrent neck pain. TRIAL REGISTRATION: The trial was registered 03/07/2018 at ClinicalTrials.gov , registration number: NCT03576846.

A cross-sectional analysis of persistent low back pain, using correlations between lumbar stiffness, pressure pain threshold, and heat pain threshold.

INTRODUCTION: Little is known about the underlying biomechanical cause of low back pain (LBP). Recently, technological advances have made it possible to quantify biomechanical and neurophysiological measurements, potentially relevant factors in understanding LBP etiology. However, few studies have explored the relation between these factors. This study aims to quantify the correlation between biomechanical and neurophysiological outcomes in non-specific LBP and examine whether these correlations differ when considered regionally vs. segmentally. METHODS: This is a secondary cross-sectional analysis of 132 participants with persistent non-specific LBP. Biomechanical data included spinal stiffness (global stiffness) measured by a rolling indenter. Neurophysiological data included pain sensitivity (pressure pain threshold and heat pain threshold) measured by a pressure algometer and a thermode. Correlations were tested using Pearson's product-moment correlation or Spearman's rank correlation as appropriate. The association between these outcomes and the segmental level was tested using ANOVA with post-hoc Tukey corrected comparisons. RESULTS: A moderate positive correlation was found between spinal stiffness and pressure pain threshold, i.e., high degrees of stiffness were associated with high pressure pain thresholds. The correlation between spinal stiffness and heat pain threshold was poor and not statistically significant. Aside from a statistically significant minor association between the lower and the upper lumbar segments and stiffness, no other segmental relation was shown. CONCLUSIONS: The moderate correlation between spinal stiffness and mechanical pain sensitivity was the opposite of expected, meaning higher degrees of stiffness was associated with higher pressure pain thresholds. No clinically relevant segmental association existed.

Posterior to anterior spinal stiffness measured in a sample of 127 secondary care low back pain patients.

BACKGROUND: The sensation of spinal stiffness is a commonly reported symptom among back pain patients, with the clinical assessment of spinal stiffness usually being part of the decision-making process when deciding on providing manual treatment of low back pain. While any relationship between spinal stiffness and low back pain is likely to be multifactorial, prior exploration of this relationship has been overly simplistic (e.g., univariate regression analyses). The purpose of this study was to address this gap by taking a broader approach to compare instrumented measures of spinal stiffness to demographic characteristics, pain phenotypes, psychometrics, and spine-related disability in a sample of secondary care low back pain patients using multivariate regression analysis. METHODS: Instrumented spinal stiffness measures from 127 patients in secondary care were used to calculate terminal and global spinal stiffness scores. A best subset analysis was used to find the subsets of 14 independent variables that most accurately predicted stiffness based on the evaluation of the adjusted R-square, Akaike Information Criteria, and the Bayesian Information Criteria. FINDINGS: In the resulting multivariate models, sex (p < 0.001) and age (p < 0.001) were the primary determinants of terminal stiffness, while global stiffness was primarily determined by age (p = 0.003) and disability (p = 0.024). INTERPRETATION: Instrumented measures of spinal stiffness are multifactorial in nature, and future research into this area should make use of multivariate analyses.