Chronic Pain Rehabilitation Research Articles

The influence of anxiety reduction on clinical response to pediatric chronic pain rehabilitation.

This study investigates the relationship between anxiety reduction and functional outcomes in children and adolescents receiving intensive interdisciplinary rehabilitation services for chronic pain (CP). Specifically, we evaluated whether: (1) anxiety changes over the course of treatment; (2) anxiety covaries with functional outcomes to rehabilitation; and (3) change in anxiety predicts change in functional outcomes from rehabilitation for CP. Using 3 separate measures assessing anxiety-related constructs, we hypothesized that anxiety would be associated with functioning, both before and following intensive rehabilitation for CP. Further, we hypothesized that a decrease in anxiety-related symptoms following rehabilitation would predict a positive change in functional outcomes. Our sample consisted of 119 children and adolescents treated for CP in an interdisciplinary rehabilitation program between 2007 and 2012. Children completed 3 measures related to anxiety (general anxiety, pain-specific anxiety, pain catastrophizing) and 2 functional outcome measures (eg, Bath Adolescent Pain Questionnaire, PedsQL) as part of clinical care. Measures of anxiety-related constructs were significantly correlated with measures of impairment and functioning, both at admission and at 1-month postdischarge. Regression analyses demonstrated that, after controlling for age, sex, and pain level at admission, a decrease in anxiety significantly predicted between 14% and 40% unique variance in functional outcomes. The findings of this study support existing research on anxiety and CP, specifically the relationship between anxiety and pain-related disability. This study also supports the benefit of intensive interdisciplinary rehabilitation for both reducing anxiety and increasing functional outcomes, suggesting a possible link in children's response to intervention. Study limitations and future directions for related research are discussed.

Theoretical Considerations for Chronic Pain Rehabilitation.

Conventional rehabilitation of patients with chronic pain is often not successful and is frustrating for the treatment team. However, theoretical developments and substantial advances in our understanding of the neurological aspects of chronic pain are changing these experiences. Modern theoretical models of pain consider pain to be a perceptual inference that reflects a "best guess" that protective action is required. This article argues that keen observation and open and respectful clinician-patient and scientist-clinician relationships have been critical for the emergence of effective rehabilitation approaches and will be critical for further improvements. The role in modern pain rehabilitation of reconceptualizing the pain itself-by "Explaining Pain," careful and intentional observation of the person in pain, and the strategic and constant communication of safety-is emphasized. It also is suggested that better understanding of the neural mechanisms underpinning chronic pain has directly informed the development of new therapeutic approaches, which are being further refined and tested. Conventional pain treatment (where the clinician strives to find the pain-relieving medication or exercise) or pain management (where the clinician helps the patient to manage life despite unabating pain) is being replaced by pain rehabilitation, where a truly biopsychosocial approach allows clinicians to provide patients with the knowledge, understanding, and skills to reduce both their pain and disability. A brief overview is provided of the key aspects of modern pain rehabilitation and the considerations that should lead our interaction with patients with chronic pain.

Do additional proprioception exercises to stabilization exercises have more beneficial effects on pain, muscle strength and functionality in chronic low back pain?

Purpose: This study has been carried out to investigate the efficacy of proprioception exercises in addition to stabilization exercises on pain intensity level, muscle strength and functionality in patients with chronic low back pain. Methods: 16 female and 14 male, a total of 30 patients with chronic low back pain have been recruited in this study. They have been divided into two similar groups as Group 1 ( n1 1⁄415) and Group 2 ( n21⁄415). Their mean age was 33.4±13.6 years for Group 1 and 31.3±11.3 years for Group 2. Previous surgery, acute disc diseases, rheumatic diseases, metabolic diseases, spinal stenosis, enfections, vertebral fractures and malignancy were the exclusion criteria. Patients in Group 1 (Stabilization Group) have been treated with stabilization exercises while patients in Group 2 ( Stabilizationþproprioception) have got proprioception exercises in addition to stabilization exercises in their rehabilitation program. Visual Analogue Scale has been used to measure pain intensity level and Oswestry Functional Scale for assessing functional level of the back. Their back and abdominal muscle strength had been analysed with Biodex System Pro 3 Isokinetic System. Treatment period for the both groups was 6 weeks with 3 sessions per week. Results: There was significant pain relief in resting and activity for the both groups after the treatment, but the differences between the groups were not significant. Both groups had obvious improvements in peak torque and average peak torque values of trunk flexors and extansors after the rehabilitation. Peak torque/ body weight both for flexors and extansor have increased in Group 1. Group 2 has showed significant improvement in peak torque / body weight value for the flexors, but not for the extansors. There were no significant differences in various flexor and extensor muscle strength values between the groups. Group 1 and Group 2 have showed singificant improvements in their functional level after the treatment. The functional score was 3.9±2.9 points for the Group 1 (before: 7.7±2.7 points) and, 3±1.3 points for the Group 2 (before: 8.9±3.1 points) after the rehabilitation. However, The groups did not differ significantly for it (p> 0.05). Conclusions: The effects of stabilization exercises and stabilizationþ proprioception exercises have been found similar. Each of them have beneficial effect in rehabilitation of chronic low back pain. Although both exercises can be used to relieve pain, to increase muscle strength and to enhance back functions for the patients with chronic low back pain, the future studies will be needed to clarify the additional effects of proprioception.

(522) The effect of psychiatric comorbidities on treatment outcomes of veterans participating in an interdisciplinary chronic pain rehabilitation program

Psychiatric comorbidities have been shown to adversely affect chronic pain and its treatment, but research is limited regarding its impact on different treatment approaches, particularly interdisciplinary chronic pain rehabilitation. Research on this topic involving veterans is minimal. This study examined the effects of psychiatric comorbidities on veterans’ response to an interdisciplinary outpatient chronic pain rehabilitation program (OCPRP). One hundred patients who completed a VA OCPRP were randomly selected. Participants with psychiatric diagnoses were identified and categorized into one of two groups. Group 1 consisted of 21 patients with no psychiatric diagnoses, and Group 2 included 24 patients with 2 or more psychiatric diagnoses. The 2 groups did not differ on any baseline characteristics, with the exception of non-pain-related psychiatric medications. Patients completed the Pain Outcomes Questionnaire (POQ) and Sleep Problems Questionnaire at intake and discharge, measuring pain intensity, vitality, pain-related negative mood, mobility, pain-related fears, activities of daily living (ADLs), and sleep impairment, with opioid usage also monitored. A MANOVA demonstrated a significant main effect for Time and Group, with a trend effect for the Time x Group interaction (p < .1). Univariate ANOVA’s showed a significant (p < .05) main effect for the Time and Group factors on all POQ and sleep subscale measures except ADLs. Significant Time x Group interactions were also found, with Group 2 patients showing higher pre-and post-treatment scores for negative mood, vitality, and fear, as well as significantly less improvement at discharge in pain, negative mood, and mobility. No significant differences were observed between groups regarding opioid usage. These findings suggest that psychiatric comorbidities have a significant effect on pain rehabilitation treatment outcomes among veterans. Additional research with larger samples, objective measures of functioning, better controls for non-pain psychiatric medications, and longer term follow-up is warranted. Psychiatric comorbidities have been shown to adversely affect chronic pain and its treatment, but research is limited regarding its impact on different treatment approaches, particularly interdisciplinary chronic pain rehabilitation. Research on this topic involving veterans is minimal. This study examined the effects of psychiatric comorbidities on veterans’ response to an interdisciplinary outpatient chronic pain rehabilitation program (OCPRP). One hundred patients who completed a VA OCPRP were randomly selected. Participants with psychiatric diagnoses were identified and categorized into one of two groups. Group 1 consisted of 21 patients with no psychiatric diagnoses, and Group 2 included 24 patients with 2 or more psychiatric diagnoses. The 2 groups did not differ on any baseline characteristics, with the exception of non-pain-related psychiatric medications. Patients completed the Pain Outcomes Questionnaire (POQ) and Sleep Problems Questionnaire at intake and discharge, measuring pain intensity, vitality, pain-related negative mood, mobility, pain-related fears, activities of daily living (ADLs), and sleep impairment, with opioid usage also monitored. A MANOVA demonstrated a significant main effect for Time and Group, with a trend effect for the Time x Group interaction (p < .1). Univariate ANOVA’s showed a significant (p < .05) main effect for the Time and Group factors on all POQ and sleep subscale measures except ADLs. Significant Time x Group interactions were also found, with Group 2 patients showing higher pre-and post-treatment scores for negative mood, vitality, and fear, as well as significantly less improvement at discharge in pain, negative mood, and mobility. No significant differences were observed between groups regarding opioid usage. These findings suggest that psychiatric comorbidities have a significant effect on pain rehabilitation treatment outcomes among veterans. Additional research with larger samples, objective measures of functioning, better controls for non-pain psychiatric medications, and longer term follow-up is warranted.

(472) Adolescents' change in functional abilities after completion of an intensive chronic pain rehabilitation program using subjective measures

(472) Adolescents' change in functional abilities after completion of an intensive chronic pain rehabilitation program using subjective measures

(521) A multilevel path model analysis of the relations between sleep, pain, and pain catastrophizing in chronic pain rehabilitation program patients

(521) A multilevel path model analysis of the relations between sleep, pain, and pain catastrophizing in chronic pain rehabilitation program patients

(525) Efficacy and prediction of pain, mood, and function outcomes upon completion of an interdisciplinary chronic pain rehabilitation program.

Chronic pain renders many individuals incapacitated and increases the risk of opioid dependence throughout the lifetime course of treatment. The efficacy of an intensive non-opioid interdisciplinary chronic pain rehabilitation program (CPRP) was previously established in headache patients1 and was expanded to include a broader range of primary pain conditions in this study. Assessments of pain intensity (0-10), Depression Anxiety Stress Scale (DASS) and Perceived Stress Scale (PSS) scores (measuring mood), Pain Disability Index scores (PDI; measuring function), and coping styles, utilizing the brief COPE questionnaire were compared in 133 patients at admission versus discharge. Statistical and clinically significant improvements, in addition to the predictive potential of patient characteristics and baseline pain, mood, and function, were investigated using repeated measures, paired t-tests, binary logistic regression, and ANOVA. Depression (18.4±11.1 v. 6.8±7.3), anxiety (12.4±9.9 v. 5.9±6.7), disability scores (44.0±1.0 v. 21.3±14.9), and pain (6.8±2.1 v. 3.6±2.5) were significantly reduced over the course of CPRP (p<0.001). Marital status (Wilks’ Lambda= 0.89, F(4,228)=3.407, p=0.010) and primary pain condition (Wilks’ Lambda= 0.83, F(12,228)=1.925, p=0.033) impacted mood with the most significant improvement in depression of single individuals and anxiety of fibromyalgia patients. Clinically significant improvement of at least one level of depression was enhanced by acceptance type coping and was diminished by substance abuse coping, higher disability levels, and post-traumatic stress disorder symptoms at admission (X2(4)=32.6, p<0.001). Older age, single status, and planning style coping at admission predicted clinically lower disability by discharge (X2(4)=15.2, p=0.004). Improvement of pain and anxiety level were negatively impacted by each additional year of chronic pain an individual had already experienced (X2(1)=5.9, p=0.015 and X2(1)=11.0, p=0.001). Taken together, this study indicates the potential pain, mood, and function benefit of an interdisciplinary program and may enable improved risk stratification and personalization of chronic pain treatment. (1. Zheng, Headache, 2013.) Chronic pain renders many individuals incapacitated and increases the risk of opioid dependence throughout the lifetime course of treatment. The efficacy of an intensive non-opioid interdisciplinary chronic pain rehabilitation program (CPRP) was previously established in headache patients1 and was expanded to include a broader range of primary pain conditions in this study. Assessments of pain intensity (0-10), Depression Anxiety Stress Scale (DASS) and Perceived Stress Scale (PSS) scores (measuring mood), Pain Disability Index scores (PDI; measuring function), and coping styles, utilizing the brief COPE questionnaire were compared in 133 patients at admission versus discharge. Statistical and clinically significant improvements, in addition to the predictive potential of patient characteristics and baseline pain, mood, and function, were investigated using repeated measures, paired t-tests, binary logistic regression, and ANOVA. Depression (18.4±11.1 v. 6.8±7.3), anxiety (12.4±9.9 v. 5.9±6.7), disability scores (44.0±1.0 v. 21.3±14.9), and pain (6.8±2.1 v. 3.6±2.5) were significantly reduced over the course of CPRP (p<0.001). Marital status (Wilks’ Lambda= 0.89, F(4,228)=3.407, p=0.010) and primary pain condition (Wilks’ Lambda= 0.83, F(12,228)=1.925, p=0.033) impacted mood with the most significant improvement in depression of single individuals and anxiety of fibromyalgia patients. Clinically significant improvement of at least one level of depression was enhanced by acceptance type coping and was diminished by substance abuse coping, higher disability levels, and post-traumatic stress disorder symptoms at admission (X2(4)=32.6, p<0.001). Older age, single status, and planning style coping at admission predicted clinically lower disability by discharge (X2(4)=15.2, p=0.004). Improvement of pain and anxiety level were negatively impacted by each additional year of chronic pain an individual had already experienced (X2(1)=5.9, p=0.015 and X2(1)=11.0, p=0.001). Taken together, this study indicates the potential pain, mood, and function benefit of an interdisciplinary program and may enable improved risk stratification and personalization of chronic pain treatment. (1. Zheng, Headache, 2013.)

Bariatric Surgery Patients' Response to a Chronic Pain Rehabilitation Program.

Chronic pain (CP) is a prevalent and disabling diagnosis in obese individuals, but how bariatric surgery patients respond to chronic pain rehabilitation treatment programs has not previously been described. The aim of this study was to compare treatment outcomes of a chronic pain rehabilitation program (psychological and pain variables, medication use, treatment completion rates) for post-bariatric surgery patients to those of a non-bariatric surgery control group. Three week outpatient multidisciplinary chronic pain program in an academic medical center. This was a retrospective case-control study. Medical records of patients admitted to the Pain Rehabilitation Center at Mayo Clinic from 2008 to 2012 were reviewed. One hundred six patients with a history of bariatric surgery (cases) were identified and matched to 106 patients without a history of bariatric surgery (controls) on age, gender, and smoking status (n = 202). Matched t tests and McNemar's tests were used for analyses. Mean age was 46 years; 91% were female and 58% were non-smokers. The majority of cases (71%) had undergone Roux-en-Y gastric bypass. Bariatric patients had higher rates of benzodiazepine use at discharge (33 vs. 19%, p = 0.0433) and were less likely to complete treatment (87 vs. 97%, p = 0.007) compared to controls. Morphine equivalent use for cases was 127.3 mg ± 135.4 (n = 62) compared to 88.3 mg ± 95.3 (n = 62), p = 0.12, for controls at admission. These results suggest that bariatric patients may be at risk for treatment non-adherence and have difficulty reducing medication use in the treatment of chronic pain.

Attachment insecurity predicts responses to an interdisciplinary chronic pain rehabilitation program.

The aim of this study was to examine the hypothesis that attachment insecurity is associated with poorer responses to interdisciplinary treatment for chronic pain. Patients (n = 235) admitted to a 4-week interdisciplinary rehabilitation program were recruited. At pre-treatment, participants completed a battery of questionnaires assessing adult attachment styles and dimensions, as well as pain intensity, disability, self-efficacy, pain catastrophizing, and depressive symptoms. The latter measures were completed again at post-treatment. Nearly two-thirds of participants (65.5 %) reported having an insecure attachment style. Attachment insecurity was unrelated to pre- and post-treatment reports of pain intensity and pain-related disability, but was significantly associated with most other clinical variables at both time points. Regression analyses controlling for pre-treatment functioning indicated that attachment insecurity was associated with less improvement in pain catastrophizing, pain self-efficacy, and depressive symptoms. Further research is warranted to investigate the processes by which attachment characteristics influence patients' responses to chronic pain rehabilitation.

Structural integration as an adjunct to outpatient rehabilitation for chronic nonspecific low back pain: a randomized pilot clinical trial.

Structural Integration (SI) is an alternative method of manipulation and movement education. To obtain preliminary data on feasibility, effectiveness, and adverse events (AE), 46 outpatients from Boston area with chronic nonspecific low back pain (CNSLBP) were randomized to parallel treatment groups of SI plus outpatient rehabilitation (OR) versus OR alone. Feasibility data were acceptable except for low compliance with OR and lengthy recruitment time. Intent-to-treat data on effectiveness were analyzed by Wilcoxon rank sum, n = 23 per group. Median reductions in VAS Pain, the primary outcome, of −26 mm in SI + OR versus 0 in OR alone were not significantly different (P = 0.075). Median reductions in RMDQ, the secondary outcome, of −2 points in SI + OR versus 0 in OR alone were significantly different (P = 0.007). Neither the proportions of participants with nor the seriousness of AE were significantly different. SI as an adjunct to OR for CNSLBP is not likely to provide additional reductions in pain but is likely to augment short term improvements in disability with a low additional burden of AE. A more definitive trial is feasible, but OR compliance and recruitment might be challenging. This trial is registered with ClinicalTrials.gov (NCT01322399).

"Change is possible": Patients' experience of a multimodal chronic pain rehabilitation programme.

To explore patients' experiences of activity, participation and quality of life one year after a rehabilitation programme for chronic pain, and to determine the impact of the programme on their current life situation. Qualitative study with emergent design. The 14 informants were patients with chronic pain who had participated in rehabilitation at a pain clinic. Individual semi-structured interviews were analysed with inductive, qualitative content analysis. The core theme "Change is possible" and the themes "A life ruled by pain" (the situation before rehabilitation), "The penny's dropped" (experience during rehabilitation) and "Live a life, not only survive" (the situation at the time of the interviews) emerged from the data. These themes represent a process through which, during and after rehabilitation, the informants integrated earlier disabling symptoms into a functioning lifestyle. Individuals living with disabling chronic pain can create a better life by integrating their illness. A prerequisite is that healthcare professionals empower patients to develop the strength to take responsibility for their daily lives. This process is facilitated by skills to reduce pain and handle life, plus support from significant others.

Ultrasound Elastography: The New Frontier in Direct Measurement of Muscle Stiffness

The use of brightness-mode ultrasound and Doppler ultrasound in physical medicine and rehabilitation has increased dramatically. The continuing evolution of ultrasound technology has also produced ultrasound elastography, a cutting-edge technology that can directly measure the mechanical properties of tissue, including muscle stiffness. Its real-time and direct measurements of muscle stiffness can aid the diagnosis and rehabilitation of acute musculoskeletal injuries and chronic myofascial pain. It can also help monitor outcomes of interventions affecting muscle in neuromuscular and musculoskeletal diseases, and it can better inform the functional prognosis. This technology has implications for even broader use of ultrasound in physical medicine and rehabilitation practice, but more knowledge about its uses and limitations is essential to its appropriate clinical implementation. In this review, we describe different ultrasound elastography techniques for studying muscle stiffness, including strain elastography, acoustic radiation force impulse imaging, and shear-wave elastography. We discuss the basic principles of these techniques, including the strengths and limitations of their measurement capabilities. We review the current muscle research, discuss physiatric clinical applications of these techniques, and note directions for future research.

Multidisciplinary rehabilitation for chronic widespread musculoskeletal pain: results from daily practice.

Evidence for the efficacy of a multi-component approach for chronic widespread musculoskeletal pain (CWP) has been reported, although the effects are overall moderate and this approach has rarely been investigated in real life. The aim of the study was to describe the effects of a 15-week multidisciplinary pain rehabilitation programme on pain, activities and participation in patients with CWP. The current retrospective study used data which were routinely gathered on all consecutive patients with CWP referred to a rehabilitation programme over a 21-month period. The 15-week multidisciplinary rehabilitation programme consisted of cognitive behavioural therapy and exercise, as well as individual and group sessions with additional treatment modalities. Assessments included the Pain Disability Index (PDI), the Pain Catastrophizing Scale (PCS), the Multidimensional Pain Inventory (MPI), numerical scales for pain and fatigue, the Canadian Occupational Performance Measure (COPM), the one-minute stair-climb test and the RAND-36. Paired t-tests and Wilcoxon signed-rank tests were carried out to analyse changes over time. A total of 165 patients were included [mean age 44.1 (standard deviation 12.9) years], 143 (87%) women). Discharge data were available for 154 patients (93%). All outcomes showed statistically significant improvements between admission and discharge (p<0.05), with the largest effect sizes (>1.0) observed for the COPM. A longer duration of complaints was associated with less improvement in the PDI. In daily rehabilitation practice, a 15-week multidisciplinary treatment programme for patients with CWP showed statistically significant improvements in pain, activities and participation over time. Future studies are needed further to substantiate the long-term cost-effectiveness, and to identify the patients who benefit the most.

The systematic implementation of Acceptance & Commitment Therapy (ACT) in Dutch multidisciplinary chronic pain rehabilitation

ObjectiveThis study evaluates the implementation of Acceptance & Commitment Therapy (ACT) in Dutch chronic pain rehabilitation centers. Changes in multidisciplinary professionals’ self-perceived competencies in working with ACT were evaluated and corroborated with patients’ ratings of treatment adherence. To inform subsequent implementation efforts, relevant determinants of implementation success were monitored and the relationship with self-perceived competencies over time was explored. MethodsData was gathered from 111 professionals, 9 managers and 79 patients using questionnaires at the start (T0), halfway (T1) and end (T2) of implementation, and at the end of treatment. ResultsAll professionals adhered to ACT, improved significantly in self-perceived competencies over time and rated competence in working with ACT≥adequate at T2. Determinants of success were evaluated extremely positive by professionals and management. Professionals’ self-perceived competencies at T2 were most strongly related to ratings of more workload (b=−.43), and experienced difficulties in working with ACT (b=−.38) at T0 and T1. ConclusionMultidisciplinary chronic pain rehabilitation professionals rated their improvement in working with ACT positively during the implementation period. Impeding and facilitating factors were explored successfully. Practice implicationsA multi-faceted, long-term, educational, train-the-trainer approach may help to guide systematic changes in multidisciplinary treatment.

SP0077 Identifying Key Elements in the Structure, Process and Outcome of Rehabilitation in Chronic Pain

Chronic pain is a major symptom in most rheumatic and musculoskeletal diseases, both inflammatory and non-inflammatory. When chronic pain leads to problems with coping and functioning in everyday life, rehabilitation...

Variability in the Relationship Between Sleep and Pain in Patients Undergoing Interdisciplinary Rehabilitation for Chronic Pain

Chronic pain and sleep disturbance frequently coexist and often complicate the course of treatment. Despite the well-established comorbidity, there are no studies that have investigated concurrent changes in sleep and pain among patients participating in an interdisciplinary chronic pain rehabilitation program (ICPRP). The goal of this study was to investigate the daily changes in sleep and pain among patients participating in an ICPRP. Multilevel modeling techniques were used to evaluate the daily changes in total sleep time (TST) and pain among a sample of 50 patients with chronic noncancer pain participating in the ICPRP. Increases in TST were predictive of less pain the following treatment day, although daily pain ratings were not predictive of that night's TST. Time in treatment was a significant predictor of both TST and pain reduction, even while controlling for age, gender, anxiety, and depression. Additional analyses revealed significant individual variability in the relationship between TST and next day pain. Individuals with stronger associations between previous night's TST and next day pain were found to experience the greatest treatment benefits overall, in terms of pain reduction and TST. Our results provide compelling support for individual variability of the pain-sleep relationship in patients with intractable pain conditions participating in an ICPRP. Importantly, these findings suggest that when pain and sleep are comorbid, both must be addressed to reap the maximum response to treatment programs such as an ICPRP. This study demonstrates the utility of treating sleep problems in patients participating in an interdisciplinary chronic pain rehabilitation program. Results highlight the benefits of accounting for individual variability in the pain-sleep relationship in a clinical setting and targeting sleep interventions for those individuals whose pain and sleep problems are comorbid.

(556) Chronic pain rehabilitation and alcohol use disorder: promising outcomes in an interdisciplinary treatment program

(556) Chronic pain rehabilitation and alcohol use disorder: promising outcomes in an interdisciplinary treatment program

(553) Treatment outcomes of patients with chronic abdominal pain within an interdisciplinary chronic pain rehabilitation program

Studies examining treatment outcomes among patients with chronic noncancer pain treated in interdisciplinary chronic pain rehabilitation programs (CPRP) are abundant, however outcome studies specific to patients with abdominal pain are virtually non-existent. This retrospective study examined the outcomes of patients with abdominal pain treated in the Cleveland Clinic’s CPRP. Outcomes included pain severity, depression, anxiety and pain related functional impairment and were measured at both admission and discharge.

(563) Treatment success of older adults with chronic pain at an interdisciplinary chronic pain rehabilitation program

(563) Treatment success of older adults with chronic pain at an interdisciplinary chronic pain rehabilitation program

(552) Examining refusal to engage in interdisciplinary chronic pain rehabilitation treatment

(552) Examining refusal to engage in interdisciplinary chronic pain rehabilitation treatment