The journal of pain : official journal of the American Pain Society
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Review Comparative Study
The Rodent Tibia Fracture Model: A Critical Review and Comparison with the Complex Regional Pain Syndrome Literature.
Distal limb fracture is the most common cause of complex regional pain syndrome (CRPS), thus the rodent tibia fracture model (TFM) was developed to study CRPS pathogenesis. This comprehensive review summarizes the published TFM research and compares these experimental results with the CRPS literature. The TFM generated spontaneous and evoked pain behaviors, inflammatory symptoms (edema, warmth), and trophic changes (skin thickening, osteoporosis) resembling symptoms in early CRPS. Neuropeptides, inflammatory cytokines, and nerve growth factor (NGF) have been linked to pain behaviors, inflammation, and trophic changes in the TFM model and proliferating keratinocytes were identified as the primary source of cutaneous cytokines and NGF. Tibia fracture also activated spinal glia and upregulated spinal neuropeptide, cytokine, and NGF expression, and in the brain it changed dendritic architecture. B cell-expressed immunoglobulin M antibodies also contributed to pain behavior, indicating a role for adaptive immunity. These results modeled many findings in early CRPS, but significant differences were also noted. ⋯ Multiple neuroimmune signaling mechanisms contribute to the pain, inflammation, and trophic changes observed in the injured limb of the rodent TFM. This model replicates many of the symptoms, signs, and pathophysiology of early CRPS, but most post-fracture changes resolve within 5 months and may not contribute to perpetuating chronic CRPS.
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Randomized Controlled Trial
Hypnosis Enhances the Effects of Pain Education in Patients With Chronic Nonspecific Low Back Pain: A Randomized Controlled Trial.
The potential benefits of combining pain education (PE) with clinical hypnosis (CH) has not yet been investigated in individuals with chronic pain. A total of 100 patients with chronic nonspecific low back pain were randomized to receive either: 1) PE alone, or 2) PE with CH. Outcomes were collected by a blinded assessor at 2 weeks and 3 months after randomization. ⋯ At 3 months, participants who received PE with CH reported lower worst pain intensity (mean difference = 1.32 points, 95% CI = .29-2.34) and catastrophizing (mean difference = 5.30 points, 95% CI = 1.20-9.41). No adverse effects in either treatment condition were reported. To our knowledge, this is the first trial showing that additional use of hypnosis with PE results in improved outcomes over PE alone in patients with chronic nonspecific low back pain.
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Randomized Controlled Trial
The Opportunity to Avoid Pain May Paradoxically Increase Fear.
Fear-avoidance models propose that pain-related fear may spur avoidance behavior leading to chronic pain disability. Pain-related fear elicits avoidance behavior, which is typically aimed at reducing fear. We hypothesized that engaging in avoidance may (paradoxically) increase rather than decrease pain-related fear (ie, bidirectionality hypothesis). ⋯ Interestingly, in the avoidance group, pain-related fear increased after receiving instructions that avoidance would be possible, even before actually engaging in avoidance behavior. In the control group, no significant change was observed in pain-related fear throughout the experiment. The eyeblink startle measures did not corroborate this data pattern.
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Randomized Controlled Trial
Acceptance and Commitment Therapy for Prevention of Chronic Postsurgical Pain and Opioid Use in At-Risk Veterans: A Pilot Randomized Controlled Study.
High levels of pain, significant anxiety, or depressive symptoms before surgery put patients at elevated risk for chronic pain and prolonged opioid use following surgery. The purpose of this preliminary study was to assess the efficacy of a 1-day Acceptance and Commitment Therapy (ACT) workshop in "at-risk" veterans for the prevention of chronic pain and opioid use following orthopedic surgery. In a randomized controlled trial, 88 at-risk veterans undergoing orthopedic surgery were assigned to treatment as usual (TAU; n = 44) or TAU plus a 1-day ACT workshop (n = 44). Pain levels and opioid use were assessed up to 3 months following surgery. Pain acceptance and values-based behavior were assessed at baseline and 3-month follow-up. Participants who completed the ACT workshop reached pain and opioid cessation sooner than those in TAU. Postoperative complications exhibited a moderating effect on these outcomes, such that the effects of ACT were greater in patients without complications. Increases in pain acceptance and values-based behavior, processes targeted in ACT, were related to better outcomes. These promising results merit further investigation in a larger clinical trial. Providing an intervention before surgery for at-risk veterans has the potential to change clinical practice from a focus on management of postoperative pain to prevention of chronic pain in at-risk individuals. ⋯ This pilot study compared the effects of a 1-day preventive behavioral intervention (ACT) to TAU in at-risk veterans undergoing orthopedic surgery. Three months following the intervention, veterans receiving ACT exhibited quicker cessation of pain and opioid use. Focusing on preoperative pain management may help prevent chronic postsurgical pain.
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This review investigated whether youth exhibit attention or interpretation biases toward pain-related information and whether such biases are more pronounced in youth with chronic pain. Three databases were searched to identify studies that assessed attention or interpretation biases using an accepted experimental paradigm. Ten studies were identified, 8 examining attentional biases and 2 examining interpretation biases. ⋯ However, whether pain affects the subsequent deployment of attention is unclear. There is no evidence for biases toward pain in youth without chronic pain, but evidence suggests that anxiety or catastrophizing and attentional control may moderate pain-related attentional biases. There is also weak evidence of interpretation bias in youth with chronic pain compared with those without.