IS DISTRIBUTION OF PAIN RELATED WITH CENTRAL SENSITIZATION IN PATIENTS WITH LOWER LIMB OSTEOARTHRITIS?

Design: Cross-sectional study. Background: Osteoarthritis is one of the most common conditions in our society. A growing number of studies suggest the existence of central sensitization (CS) in a subgroup of osteoarthritic patients. One of the criteria included for the classification of CS pain is the expanded distribution of pain. As this criterion is a well-recognized sign of CS, a digital pain drawing (DPD) analysis would be useful to easily identify possible extended areas of pain distribution (PD) in patients with OA. Objective: To study the relationship between the percentage of distribution of pain in the lower limb for both knee and hip, in patients before hip or knee arthroplasty, and the Central Sensitization Inventory Questionnaire. Methods: Twenty women (mean [Formula: see text] years) with diagnosed chronic (over 3 months) knee ([Formula: see text]) and hip ([Formula: see text]) OA participated in the study, with intensity of pain from mild to severe, meaning pain [Formula: see text]/10 using the Numeric Pain Rating Scale (NPRS). The PD was analyzed via software created for this research, called “Pain Distribution Application”. Results: A statistically significant positive correlation between CSI and PD to the lower extremity OA (hip and knee) ([Formula: see text], [Formula: see text]) was found. The distribution of pain has a linear correlation with the results in CSI, of patients who tested positive for CS, i.e. with a score of [Formula: see text]. Conclusions: As the distribution of pain on the surface of the body (diffusion) increases, so does the score of people who test positive for CSI. Our results showed that calculating the distribution of pain with our application may have a utility as a CS screening tool. The PD threshold of 10% of the body area is an index for CS for chronic pain lower limb OA patients.

Hierarchical clustering by patient-reported pain distribution alone identifies distinct chronic pain subgroups differing by pain intensity, quality, and clinical outcomes

Background In clinical practice, the bodily distribution of chronic pain is often used in conjunction with other signs and symptoms to support a diagnosis or treatment plan. For example, the diagnosis of fibromyalgia involves tallying the areas of pain that a patient reports using a drawn body map. It remains unclear whether patterns of pain distribution independently inform aspects of the pain experience and influence patient outcomes. The objective of the current study was to evaluate the clinical relevance of patterns of pain distribution using an algorithmic approach agnostic to diagnosis or patient-reported facets of the pain experience. Methods and findings A large cohort of patients (N = 21,658) completed pain body maps and a multi-dimensional pain assessment. Using hierarchical clustering of patients by body map selection alone, nine distinct subgroups emerged with different patterns of body region selection. Clinician review of cluster body maps recapitulated some clinically-relevant patterns of pain distribution, such as low back pain with radiation below the knee and widespread pain, as well as some unique patterns. Demographic and medical characteristics, pain intensity, pain impact, and neuropathic pain quality all varied significantly across cluster subgroups. Multivariate modeling demonstrated that cluster membership independently predicted pain intensity and neuropathic pain quality. In a subset of patients who completed 3-month follow-up questionnaires (N = 7,138), cluster membership independently predicted the likelihood of improvement in pain, physical function, and a positive overall impression of change related to multidisciplinary pain care. Conclusions This study reports a novel method of grouping patients by pain distribution using an algorithmic approach. Pain distribution subgroup was significantly associated with differences in pain intensity, impact, and clinically relevant outcomes. In the future, algorithmic clustering by pain distribution may be an important facet in chronic pain biosignatures developed for the personalization of pain management.

Spatiotemporal patterns of pain distribution and recall accuracy: a dose-response study

Objectives Clinical decisions rely on a patient’s ability to recall and report their pain experience. Monitoring pain in real-time (momentary pain) may reduce recall errors and optimize the clinical decision-making process. Tracking momentary pain can provide insights into detailed changes in pain intensity and distribution (area and location) over time. The primary aims of this study were (i) to measure the temporal changes of pain intensity, area, and location in a dose-response fashion and (ii) to assess recall accuracy of the peak pain intensity and distribution seven days later, using a digital pain mapping application. The secondary aims were to (i) evaluate the influence of repeated momentary pain drawings on pain recall accuracy and (ii) explore the associations among momentary and recall pain with psychological variables (pain catastrophizing and perceived stress). Methods Healthy participants (N=57) received a low (0.5 ml) or a high (1.0 ml) dose of hypertonic saline (5.8%) injection into the right gluteus medius muscle and, subsequently, were randomized into a non-drawing or a drawing group. The non-drawing groups reported momentary pain intensity every 30-s. Whereas the drawing groups reported momentary pain intensity and distribution on a digital body chart every 30-s. The pain intensity, area (pixels), and distribution metrics (compound area, location, radiating extent) were compared at peak pain and over time to explore dose-response differences and spatiotemporal patterns. All participants recalled the peak pain intensity and the peak (most extensive) distribution seven days later. The peak pain intensity and area recall error was calculated. Pain distribution similarity was determined using a Jaccard index which compares pain drawings representing peak distribution at baseline and recall. The relationships were explored among peak intensity and area at baseline and recall, catastrophizing, and perceived stress. Results The pain intensity, area, distribution metrics, and the duration of pain were lower for the 0.5 mL than the 1.0 mL dose over time (p<0.05). However, the pain intensity and area were similar between doses at peak pain (p>0.05). The pain area and distribution between momentary and recall pain drawings were similar (p>0.05), as reflected in the Jaccard index. Additionally, peak pain intensity did not correlate with the peak pain area. Further, peak pain intensity, but not area, was correlated with catastrophizing (p<0.01). Conclusions This study showed differences in spatiotemporal patterns of pain intensity and distribution in a dose-response fashion to experimental acute low back pain. Unlike pain intensity, pain distribution and area may be less susceptible in an experimental setting. Higher intensities of momentary pain do not appear to influence the ability to recall the pain intensity or distribution in healthy participants. Implications The recall of pain distribution in experimental settings does not appear to be influenced by the intensity despite differences in the pain experience. Pain distribution may add additional value to mechanism-based studies as the distribution reports do not vary with pain catastrophizing. REC# N-20150052

Healthy Pain-Free Individuals with a History of Distal Radius Fracture Demonstrate an Expanded Distribution of Experimental Referred Pain Toward the Wrist

Objective Nociception caused by injuries may sensitize central mechanisms causing expanded pain areas. After recovery, the status of such pain distribution and sensitivity mechanisms is unknown. The present study investigated whether individuals who have fully recovered from a distal radius fracture demonstrate increased pain sensitivity and expanded distribution of pressure-induced pain. Design Cross-sectional single-blinded study. Setting Clinical setting. Subjects Twenty-three pain-free individuals with a history of painful distal radius fracture and 22 nonfractured, age/gender-matched controls participated in two experimental sessions (day 0, day 1) 24 hours apart. Methods Pressure pain thresholds (PPTs) were recorded bilaterally at the extensor carpi radialis longus (ECRL), infraspinatus, and gastrocnemius muscles. Spatial distribution of pain was assessed following 60-second painful pressure stimulation at the ECRL (bilateral) and the infraspinatus muscles on the fractured or dominant side. Participants drew pain areas on a body map. After day 0 assessments, prolonged pain was induced by eccentric exercise of wrist extensors on the fractured/dominant side. Results Compared with controls, pressure-induced ECRL pain in the fracture group referred more frequently toward the distal forearm (P &lt; 0.005) on day 0. Both groups showed larger pain areas on day 1 compared with day 0 (P &lt; 0.005), although the fracture group showed a larger relative change between days (P &lt; 0.005). The fracture group showed larger pain areas on the fracture side compared with the contralateral side on both days (P &lt; 0.005). Conclusions Prolonged pain and recovered prior painful injuries like fractures may sensitize pain mechanisms manifested as expanded pain distribution. Pressure-induced referred pain can be a simple pain biomarker for clinical use.

P269 Longitudinal patterns of pain distribution in axSpA patients: a retrospective cohort study

Background Chronic pain is an important and debilitating symptom experienced by patients with axial Spondyloarthritis (axSpA). The patterns of pain and their associations in this patient group is poorly understood. The overall aim of the study is to investigate patterns of pain distribution in patients with axSpA using Margolis Pain Diagrams, and any associations with clinical and demographic measures. Methods We analysed data collected from individuals attending the axSpA outpatient clinic at the Royal National Hospital for Rheumatic Diseases in Bath. All participants were asked to record their pain on a pre-printed Margolis Pain diagram at each clinical visit. The number and distribution of painful areas were assessed and then categorised into regional or widespread pain, using pre-defined anatomical criteria. Descriptive analyses and any associations between pain distribution and demographic and clinical variables were assessed. Changes in pain distribution over time, using data from up to four clinic visits, were further investigated using a Sankey diagram. Results Of the 187 participants who had a baseline pain assessment, their mean age at diagnosis was 31.6 (11.9) years and 31.6% were female. 89.3% of patients reported pain at baseline, and of these 21.4%, 29.4 % and 38.5% reported pain in 1-2, 3-4, and 5-6 regions respectively. The most common sites of pain are in the Trunk (68.4%), followed by Head and Cervical (65.8%) and Left lower limb regions (58.8%). Univariate analyses did not reveal any significant associations between the presence of widespread pain and age at diagnosis, sex, smoking or HLA-B27 status. Disease activity, measured using Bath Ankylosing Spondylitis Disease Activity Index, was significantly higher in participants with widespread pain compared to those with regional pain OR 1.60 (1.30-1.96), and a trend towards higher sleep disturbance, was demonstrated OR 1.05 (1.00-1.10). Longitudinal analyses demonstrated considerable flux over time in the number and distribution of pain reported. Conclusion The Margolis Pain diagram is a practical instrument for assessing pain in axSpA patients. Several pain patterns were noted in patients with axSpA, and future research should focus on the potential impact on quality of life measures, response to treatment, and radiological findings. Disclosures R. Nishtala None. R. Barnett None. T. Chyou None. A. Soni None. R. Sengupta None.

Experimental shoulder pain models do not validly replicate the clinical experience of shoulder pain

Background and aimsPeople with shoulder pain often present with abnormal shoulder muscle function. It is not known whether shoulder pain causes or is the result of muscle dysfunction. If pain leads to muscle dysfunction, therapeutic interventions that produce shoulder pain may be contraindicated. Experimentally induced nociception can be used to investigate a causal relationship between shoulder pain and muscle dysfunction. However, the validity of current experimental shoulder pain protocols has not been established. The aim of this study was to determine whether current experimental shoulder pain protocols validly replicate the clinical experience of shoulder pain with respect to pain distribution, quality and behaviour.MethodsNine pain free participants received two injections of hypertonic saline, one into the subacromial space and one into supraspinatus, in random order, at least 1 week apart. Investigators blind to the injection site assessed pain distribution, pain response to clinical tests which provoke shoulder pain and pain quality assessed using the McGill Pain Questionnaire.ResultsFollowing hypertonic saline injection into both the subacromial space and supraspinatus: pain was most commonly reported in the deltoid region and did not extend beyond the elbow; the most common response to clinical tests which provoke shoulder pain was a decrease in pain; and the highest rating of pain quality was in the sensory domain with very few responses in the affective domain.ConclusionsExperimental shoulder pain induced by injection of hypertonic saline into either the subacromial space or supraspinatus produced a pain distribution similar to that observed in clinical shoulder pain, but neither experimental pain protocol could reproduce the increases in pain intensity following shoulder provocation tests or the emotional distress commonly observed in people with clinical shoulder pain.ImplicationsPain induced by local shoulder nociception produced by hypertonic saline injection into shoulder structures has significant limitations as a model of clinical shoulder pain. While it is perhaps unsurprising that short duration, chemically-induced experimental pain does not replicate the quality of the clinical experience of shoulder pain, the validity of experimental shoulder pain models which produce the opposite response to provocation testing to clinical shoulder pain must be questioned.

CHRONIC PAIN CONTRIBUTES TO INJURIOUS FALLS IN COMMUNITY-DWELLING OLDER ADULTS

Fall injuries are a leading cause of death among older adults, and chronic pain has been identified as a fall risk factor. However, the potential impact of chronic pain on injurious falls is unknown. This prospective study examined the relation between chronic pain and injurious falls in a 4-year follow-up of community-dwelling older adults. The MOBILIZE Boston study recruited 765 older adults aged ≥70y living in the Boston area. Pain characteristics, including pain severity, pain interference, and pain location, were measured at baseline using the Brief Pain Inventory subscales and a joint pain questionnaire. Musculoskeletal pain distribution was categorized as “no pain”, “single site pain”, or “multisite pain”. Injurious falls were ascertained in telephone interviews following reports of falls on the monthly fall calendar postcards. The overall rate of injurious falls was 35/100 person-years. Negative binomial models, adjusting for sociodemographics, BMI, chronic conditions, mobility difficulty, analgesic and psychiatric medications, and depression, showed that pain interference and pain distribution, but not pain severity, independently predicted injurious falls. Participants in the highest third of pain interference scores had a 53% greater risk of injurious falls compared to those in the lowest pain interference group (adj.IRR=1.53, 95% CI: 1.15, 2.05). Older adults with multisite pain had a 50% higher risk of injurious falls than those without pain (adj.IRR=1.50, 95% CI: 1.16, 1.93). Risk of injurious falls related to pain was stronger among women than men. Research is needed to determine effective strategies to prevent fall injuries among older adults with chronic pain.