Associations of pain sensitivity and conditioned pain modulation with physical activity: findings from the Multicenter Osteoarthritis Study (MOST).

OBJECTIVE: Individuals with chronic pain due to knee osteoarthritis (OA) are insufficiently physically active, and alterations of facilitatory and inhibitory nociceptive signaling are common in this population. Our objective was to examine the association of these alterations in nociceptive signaling with objective accelerometer-based measures of physical activity in a large observational cohort. DESIGN: We used data from the Multicenter Osteoarthritis Study. Measures of peripheral and central pain sensitivity included pressure pain threshold at the knee and mechanical temporal summation at the wrist, respectively. The presence of descending pain inhibition was assessed by conditioned pain modulation (CPM). Physical activity was quantitatively assessed over 7 days using a lower back-worn activity monitor. Summary metrics included steps/day, activity intensity, and sedentary time. Linear regression analyses were used to evaluate the association of pain sensitivity and the presence of descending pain inhibition with physical activity measures. RESULTS: Data from 1873 participants was analyzed (55.9% female, age = 62.8 ± 10.0 years). People having greater peripheral and central sensitivity showed lower step counts. CPM was not significantly related to any of the physical activity measures, and none of the exposures were significantly related to sedentary time. CONCLUSIONS: In this cohort, greater peripheral and central sensitivity were associated with reduced levels of objectively-assessed daily step counts. Further research may investigate ways to modify or treat heightened pain sensitivity as a means to increase physical activity in older adults with knee OA.

Delayed timing of physical therapy initiation increases the risk of future opioid use in individuals with knee osteoarthritis: a real-world cohort study.

OBJECTIVE: We assessed whether late versus early initiation of physical therapy (PT) was related to greater risk of future opioid use in people with knee osteoarthritis (OA) who receive PT. METHODS: We used Commercial and Medicare Advantage claims data from 1999 to 2018 from American adults with incident knee OA referred for PT within 1 year of diagnosis. We categorised people as opioid naïve or opioid experienced based on prior prescriptions. We examined the association of timing of PT initiation with any and chronic opioid use over 1 year. RESULTS: Of the 67 245 individuals with incident knee OA, 35 899 were opioid naïve and 31 346 were opioid experienced. In the opioid naïve group, compared with PT within 1 month, PT 1 to <3, 3 to <6, 6 to <9, 9-12 months from diagnosis was associated with adjusted risk ratio (aRR (95% CIs)) for any opioid use of 1.18 (1.10 to 1.28), 1.49 (1.37 to 1.61), 1.73 (1.58 to 1.89) and 1.93 (1.76 to 2.12), respectively; aRRs (95% CIs) for chronic opioid use were 1.25 (1.01 to 1.54), 1.83 (1.48 to 2.26), 2.29 (1.82 to 2.89) and 2.50 (1.96 to 3.19). Results were similar among opioid experienced; aRRs (95% CIs) for any opioid use were 1.19 (1.14 to 1.24), 1.32 (1.26 to 1.37), 1.39 (1.32 to 1.45) and 1.54 (1.46 to 1.61); aRRs (95% CIs) for chronic opioid use were 1.25 (1.17 to1.34), 1.43 (1.33 to 1.54), 1.53 (1.41 to 1.66) and 1.65 (1.51 to 1.80). CONCLUSION: Compared with PT initiation within 1 month, delayed PT initiation was associated with higher risk of opioid use in people with incident knee OA. The longer the delay in PT initiation, the greater was the risk.

Correlation Between Central Sensitization and Remote Muscle Performance in Individuals With Chronic Low Back Pain.

OBJECTIVE: The purpose of this study was to examine associations between the degree of central sensitization (CS) and remote muscle performance in people with chronic low back pain (CLBP). METHODS: The 2011 fibromyalgia (FM) criteria and severity scales (2011 FM survey) were used as a surrogate measure of CS to divide the participants into 2 groups: FM-positive CLBP and FM-negative CLBP. Measures related to central sensitization included the 2011 FM survey and pressure pain threshold of the thumbnail. Measures related to muscle performance included neck flexor muscle strength and endurance and plantar flexor muscle strength. Between-groups and correlation analyses were performed. RESULTS: Sixty people with CLBP were enrolled (30 FM-positive, 30 FM-negative). There was no significant difference between the subgroups in age, sex, or pain duration (P > .05). The FM-positive CLBP group showed poorer neck flexor muscle endurance (P = .01) and plantar flexor muscle strength (P = .002) than the FM-negative CLBP group, whereas neck flexor muscle strength was not different between the groups (P = .175). Scores for FM and values for pressure pain thresholds of the thumbnail were associated with neck flexor muscle strength (respectively, r = -0.320, P = .013, and r = 0.467, P < .001), endurance (r = -0.242, P < .001, and r = 0.335, P = .009), and plantar flexor muscle strength (r = -0.469, P < .001, and r = 0.500, P < .001). CONCLUSION: We found associations between the degree of CS and remote muscle strength and endurance, suggesting that poor remote muscle performance is possibly a clinical sign of CS in people with CLBP.

Association between Opioid Dose, Acute Post-operative Pain and Walking Distance Following Lumbar Spine Surgery.

WHAT IS KNOWN AND OBJECTIVE: The opioid doses on post-operative day 1 (POD1) is a major predictor of recovery in patients following lumbar spine surgery (LSS). However, the opioid doses vary widely in clinical practice. Thus, the objective of this study was to explore the associations between opioid doses on POD1, pain and function during a hospital stay in patients following LSS. METHODS: This study used medical records of patients who underwent LSS between January 2007 and March 2018. The patients were divided into three groups (high, medium and low dose) according to the amount of opioid (oral morphine equivalents; OME) taken on POD1. A propensity score matching across the three groups was performed to account for main confounding factors related to the opioid dose, pain intensity and gait distance, which identified 114 matched patients in each group. The difference of pain intensity and gait distance between the groups on POD1 was analysed. RESULTS: The OME in each group on POD1 was 168.75 ± 69.50 mg (high), 65.92 ± 13.28 mg (medium) and 16.90 ± 9.80 mg (low) (P < .0001). Pain intensity on the postoperative day 2 (POD2) and 3 (POD3) was not different between the groups (P > .05). Gait distance on POD2 and POD3 was different between the groups but did not reach the adjusted statistically significant level of 0.017: high (170.3 ± 152.77 feet) versus medium (247.57 ± 216.65 feet) dose on POD2 (P = .04); high (179.31 ± 135.722 feet) versus low (230.94 ± 145.74 feet) dose on POD3 (P = .03); and medium (196.98 ± 159.42 feet) versus low (261.00 ± 161.03 feet) dose on POD3 (P = .09). WHAT IS NEW AND CONCLUSION: The findings indicated that high dose opioids on POD1 did not translate into better outcomes of pain and gait in patients following LSS. In fact, patients in medium and low dose groups walked a greater distance on POD2 and POD3. Use of a functional outcome such as gait should be considered to optimize opioid dose effects.

Quantifying Lumbar Mobilization With Inertial Measurement Unit.

OBJECTIVE: Lumbar mobilization is a standard intervention for the management of low back pain, yet ways to quantify lumbar mobilization are limited. An inertial measurement unit (IMU) is a small and inexpensive device that can be used to quantify lumbar mobilization. The objective of this study was to determine the validity and reliability of an IMU in measuring the amplitude of displacement of a clinician's hand movement during oscillatory lumbar mobilization. METHODS: An IMU was secured on a clinician's hand during application of mobilization forces at the L4 segment of 16 healthy participants. The validity of the IMU was tested against common laboratory methods of measurements (force plate and motion capture system). The reliability of the IMU measurements was determined between 2 clinicians (inter-rater reliability) and between 2 sessions (intra-rater reliability) by calculating percent error of measurement (%e) and limits of agreement (LOA). The reliability was considered high when |%e| ≤ 10% and |LOA| ≤ 20%; moderate when |%e| 10% to 20% and |LOA| 21% to 40%; and non-acceptable when |%e| > 20% and |LOA| > 40%. RESULTS: The IMU measurements had high correlation with the force plate measurements (rs = 0.94) and high agreement with the motion capture system measurements (%e = 4%, LOA = -11% and 20%). Both the inter-rater reliability (%e = 6%, LOA = -25% and 37%) and the intrarater reliability (%e = -1%, LOA = -29% and 27%) of IMU measurements were moderate. CONCLUSION: The IMU seems to be a valid device to measure the amplitude of a clinician's hand movement. The moderate reliability found in this study may not reflect poor reliability of the IMU as much as inconsistency in reapplication of lumbar mobilization.

Mediating Effect of Pain Sensitization on the Paradoxical Relation of Taking Opioids to Pain Severity in Knee Osteoarthritis: The Multicenter Osteoarthritis Study.

OBJECTIVE: One of the less understood adverse effects while taking opioids is the paradoxical increase in pain, known as opioid-induced hyperalgesia (OIH). We sought to determine whether pain sensitization mediates the relation of taking an opioid to pain severity in people with knee osteoarthritis (OA). METHODS: We included participants in a National Institutes of Health-funded cohort study of people with or at risk of knee OA. Participants were categorized into opioid and nonopioid analgesic groups at baseline. Western Ontario McMaster Universities OA Index (WOMAC) pain two years later was assessed as the outcome. We used causal mediation analysis to assess the mediating role of pain sensitization, quantified by changes in pressure pain threshold (PPT) at the wrist and patella over two years, on the effect of taking an opioid on WOMAC pain two years later. RESULTS: We included 296 participants who took opioids and 1,070 participants who took nonopioid analgesics. Compared with taking nonopioid analgesics, taking opioids was associated with greater pain two years later. This relation was mediated by 0.05- and 0.08-unit changes in wrist PPT (95% confidence interval [CI] 0.01-0.10) and patellar PPT (95% CI 0.02-0.14), respectively. When we assessed any worsening in WOMAC pain score over two years, taking opioids, compared with taking nonopioid analgesics, had 2% and 5% higher odds of experiencing any worsening pain mediated by changes in wrist PPT (95% CI 0.99-1.04) and patellar PPT (95% CI 1.01-1.09), respectively. CONCLUSION: Pain sensitization had small mediating effects on the paradoxical phenomenon of OIH, suggesting that pain sensitization may not play a major role and/or that PPT is an inadequate tool to assess OIH.

Tailored Yoga Intervention for Postlumbar Spine Surgical Pain Management: A Feasibility Study.

Introduction: Severe pain, anxiety, and high opioid use are common following lumbar spine surgery (LSS). Yoga helps to reduce pain and anxiety, but it has not been considered for postsurgical care. The authors developed and tested the feasibility of a tailored yoga program designed for individuals undergoing LSS and explored clinical feasibility of yoga intervention on measures of pain, function, psychological status, and opioid use. Methods: Individuals scheduled for LSS were randomized into yoga versus control groups presurgery. Participants in the yoga group received tailored yoga sessions plus usual care, whereas participants in the control group received usual care only during the hospital stay post-LSS. In-person daily yoga sessions were individually presented and performed in the participant's hospital room. Feasibility was assessed by recruitment and retention rates, rate of yoga session completion, tolerance to yoga intervention, and ability to carry out planned assessment. Exploratory clinical outcomes included pain, psychological measures, Timed-Up-and-Go test, gait distance, and opioid use, during the hospital stay post-LSS. Results: Forty-one participants were enrolled, of which 30 completed. There were no dropouts. Planned assessments were completed within 45 min, suggesting no excessive burden on participants. Baseline variables were similar across both groups. The majority of participants participated in yoga intervention on the day of surgery or one day after surgery with acceptance rate of 100%. Participants showed good tolerance to yoga intervention on 0-4 tolerance scale and by their reports of exploratory clinical outcomes. Conclusion: This study indicates feasibility for a modified yoga program for postoperative care following LSS due to participant tolerance and retention. The results provide preliminary framework for future confirmatory studies that can assess the potential benefits of yoga in reducing pain, catastrophizing behavior, and opioid use and improving function. A modified yoga program focusing on diaphragmatic breathing, relaxation, and core isometric contraction exercises can be an important adjunct intervention for patients undergoing LSS. CTR Number: This trial was registered in UMIN CTR (https://rctportal.niph.go.jp/en/) with registration number: UMIN000032595.

Post-surgical contributors to persistent knee pain following knee replacement: The Multicenter Osteoarthritis Study (MOST).

Objective: Pain persistence following knee replacement (KR) occurs in ∼20-30% of patients. Although several studies have identified preoperative risk factors for persistent post-KR pain, few have focused on post-KR contributing factors. We sought to determine whether altered nociceptive signaling and other peripheral nociceptive drivers present post-operatively contribute to post-KR pain. Design: We included participants from the Multicenter Osteoarthritis Study who were evaluated ∼12 months after KR. We evaluated the relation of measures of pain sensitivity [pressure pain threshold (PPT), temporal summation (TS), and conditioned pain modulation (CPM)] and the number of painful body sites to post-KR WOMAC knee pain, and of the number of painful sites to altered nociceptive signaling using linear or logistic regression models, as appropriate. Results: 171 participants (mean age 69 years, 62% female) were included. TS was associated with worse WOMAC pain post-KR (ߠ​= â€‹0.77 95% CI:0.19-1.35) and reduced odds of achieving patient acceptable symptom state (aOR â€‹= â€‹0.54 95%CI:0.34-0.88). Inefficient CPM was also associated with worse WOMAC pain post-KR (ߠ​= â€‹1.43 95% CI:0.15-2.71). In contrast, PPT was not associated with these outcomes. The number of painful body sites present post-KR was associated with TS (ߠ​= â€‹0.05, 95% CI:0.01, 0.05). Conclusions: Post-KR presence of central sensitization and inefficient descending pain modulation was associated with post-KR pain. We also noted that presence of other painful body sites contributes to altered nociceptive signaling, and this may thus also contribute to the experience of knee pain post-KR. Our findings provide novel insights into central pain mechanisms and other peripheral pain sources contributing to post-KR persistent knee pain.

Sleep quality in individuals with chronic low back pain and central sensitization.

BACKGROUND AND PURPOSE: Sleep problems are common in individuals with chronic low back pain (CLBP). Central sensitization (CS) is present in a subgroup of individuals with CLBP. However, our knowledge about whether sleep quality varies between the subgroups of CLBP is limited. Therefore, we sought to examine whether the subgroup of CLBP with CS has poorer sleep quality than the subgroup without CS. METHODS: 2011 Fibromyalgia Survey (2011 FM survey) was used as a surrogate measure of CS to divide the CLBP participants into two subgroups: CLBP with CS and CLBP without CS. We also created a CS index comprising a set of quantitative sensory testing measures (i.e., pressure pain thresholds, conditioned pain modulation) to evaluate pain sensitivity. Sleep quality was assessed with Pittsburgh Sleep Quality Index (PSQI). Group differences about PSQI and CS index and associations between sleep quality and CS across the groups were analyzed. RESULTS: We included 60 participants with CLBP and 23 healthy controls (HCs). Overall, 80% of the participants with CLBP presented with poor sleep quality. Participants with CLBP with CS showed significantly higher PSQI scores (poorer sleep) than participants with CLBP without CS and HCs (p < 0.05). Both the 2011 FM survey and CS index were significantly correlated with sleep quality (r = 0.5870, p < 0.001 and r = -0.264, p = 0.04). Logistic regression models revealed that the FM status (odds ratio (OR) = 6.00, p = 0.02 [95% confidence interval: 1.31-42.1]), but not the CS index (OR = 1.11, p = 0.79 [95% CI: 0.48-2.71]) was associated with PSQI. After adjusting covariates, the results remained similar but became non-significant for the FM status. DISCUSSION: We found that sleep problems were more common and severe in those who exhibited signs of CS. Thus, clinicians may consider using 2011 FM survey to identify those with CS and co-existing sleep problems.

Association of Physical Therapy Interventions With Long-term Opioid Use After Total Knee Replacement.

Importance: Many individuals who undergo total knee replacement (TKR) become long-term opioid users after TKR. Associations of physical therapy (PT) interventions before or after TKR with long-term use of opioids are not known. Objectives: To evaluate associations of PT interventions before and after TKR with long-term opioid use after TKR. Design, Setting, and Participants: This cohort study used data from the OptumLabs Data Warehouse on 67 322 individuals aged 40 years or older who underwent TKR from January 1, 2001, to December 31, 2016, stratified by history of opioid use. The analyses for the study included data from January 1, 1999, to December 31, 2018. Exposures: Any PT interventions within 90 days before or after TKR, post-TKR PT dose as number of sessions (ie, 1-5, 6-12, and ≥13 sessions), post-TKR PT timing as number of days to initiation of care (ie, <30 days, 31-60 days, or 61-90 days after TKR), and post-TKR PT type (ie, active vs passive). Main Outcomes and Measures: The association of pre- and post-TKR PT with risk of long-term opioid use occurring more than 90 days after TKR was assessed using logistic regression while adjusting for confounders, including age, sex, race and ethnicity (Asian, Black, Hispanic, or White), obesity, type of insurance, geographical location, and physical and mental health comorbidities. Results: A total of 38 408 opioid-naive individuals (21 336 women [55.6%]; mean [SD] age, 66.2 [9.2] years) and 28 914 opioid-experienced individuals (18 426 women [63.7%]; mean [SD] age, 64.4 [9.3] years) were included. Receipt of any PT before TKR was associated with lower odds of long-term opioid use in the opioid-naive (adjusted odds ratio [aOR], 0.75 [95% CI, 0.60-0.95]) and opioid-experienced (aOR, 0.75 [95% CI, 0.70-0.80]) cohorts. Receipt of any post-TKR PT was associated with lower odds of long-term use of opioids in the opioid-experienced cohort (aOR, 0.75 [95% CI, 0.70-0.79]). Compared with 1 to 5 sessions of PT after TKR, 6 to 12 sessions (aOR, 0.82 [95% CI, 0.75-0.90]) and 13 or more sessions (aOR, 0.71 [95% CI, 0.65-0.77) were associated with lower odds in the opioid-experienced cohort. Compared with initiation of PT within 30 days after TKR, initiation 31 to 60 days or 61 to 90 days after TKR were associated with greater odds in the opioid-naive (31-60 days: aOR, 1.45 [95% CI, 1.19-1.77]; 61-90 days: aOR, 2.15 [95% CI, 1.43-3.22]) and opioid-experienced (31-60 days: aOR, 1.10 [95% CI, 1.02-1.18]; 61-90 days: aOR, 1.32 [95% CI, 1.12-1.55]) cohorts. Compared with passive PT, active PT was not associated with long-term opioid use in the opioid-naive (aOR, 1.00 [95% CI, 0.81-1.24]) or opioid-experienced (aOR, 0.99 [95% CI, 0.92-1.07]) cohorts. Conclusions and Relevance: This cohort study suggests that receipt of PT intervention before and after TKR, receipt of 6 or more sessions of PT care after TKR, and initiation of PT care within 30 days after TKR were associated with lower odds of long-term opioid use. These findings suggest that PT may help reduce the risk of long-term opioid use after TKR.

Protocol for Testing Yoga to Reduce Post-Lumbar Spine Surgery Pain: A Methodology Article.

Currently, acute postoperative pain during hospitalization is primarily managed by medications, and patients must adhere to restrictive postoperative precautions for 3 months following lumbar spine surgeries. Yoga can be an alternative approach to assist in acute and subacute postoperative pain management, anxiety, and return to function. The purpose of the present work was to develop and test the feasibility and explore the effectiveness of a tailored yoga program, delivered in-person during the hospital stay and electronically after hospital discharge, as a potential new avenue for postoperative care. This pilot study will use a crossover randomized controlled design. Individuals aged between 40 and 80 years who are scheduled for lumbar laminectomy and/or fusion, and who have not practiced regular yoga within the past 6 months at the time of enrollment, will be recruited and randomized to either a tailored yoga program (intervention group) or usual care (control group) during the hospital stay (phase one). Bearing in mind postoperative precautions, all subjects will be instructed to perform a home-based tailored yoga program delivered electronically via YouTube links for 8 weeks post-hospital discharge (phase two). The primary outcome measures assessing feasibility are adherence/compliance. Secondary outcome measures include pain, anxiety, function, sleep, perceived stress, and pain-catastrophizing behavior. Length of hospital stay and pain medication use, gait distance, and overall physical activity during hospitalization will also be collected. Finally, a qualitative interview will be obtained after completion of the hospital and home-based programs. This study will determine the feasibility of a tailored yoga program for acute and subacute postoperative lumbar spine surgery pain, anxiety, and functional outcomes.

BILATERAL SENSORY DEFICITS AND WIDESPREAD HYPERALGESIA OCCUR FOLLOWING INDUCED DELAYED ONSET MUSCLE SORENESS OF THE QUADRICEPS.

BACKGROUND: Unaccustomed eccentric exercise during sport or training may lead to delayed onset muscle soreness (DOMS), which has been demonstrated to influence postural control, potentially resulting in further injury. Afferent sensory input is critical to effective postural control, but little is known about somatosensory changes at the knee following induction of DOMS of the quadriceps muscle. The 'soreness' or hyperalgesia associated with DOMS has been postulated to occur because of damage to/inflammation of the exercised muscle, however, effects on central nociceptive mechanisms, which are known to induce altered postural responses, have been less studied. PURPOSE/HYPOTHESIS: It was hypothesized that DOMS of the quadriceps muscle would result in widespread hyperalgesia and hypoesthesia at the knee. Therefore, the purpose of this study was to investigate the effects of DOMS on knee somatosensory changes in asymptomatic healthy participants. STUDY DESIGN: Quasi-experimental cohort study. METHODS: Thirty participants (15 males and 15 females) took part in the study. Eccentric exercise consisted of 10 sets of 10 maximum eccentric quadriceps contractions performed with the dominant knee. Outcome measures consisted of pain intensity (Visual Analog Scale), pressure pain threshold (PPT), vibration perception threshold (VPT) and proprioception, measured via threshold to detection of passive motion (TDPM) at the knee, at three different assessment time points: (1) pre-eccentric exercise; (2) immediately and (3) 48 hours post-eccentric exercise. RESULTS: Not surprisingly, pain intensity increased and PPT of the vastus medialis and rectus femoris muscles decreased (hyperalgesia) immediately post-exercise on the exercised limb. However, at 48 hours, hyperalgesia was demonstrated at other lower extremity muscles, including bilaterally at the tibialis anterior muscles, and also at the hand. Evidence of hypoesthesia was also demonstrated. VPT and TDPM increased (worsened) ipsilaterally both immediately and 48 hours after exercise, and TDPM increased bilaterally at 48 hours. Females demonstrated greater impairment in TDPM than males at 48 hours. Expanding distribution of hyperalgesia, ipsilaterally impaired VPT and bilaterally impaired proprioception were demonstrated in the presence of DOMS. DISCUSSION/CONCLUSION: Inflammation from unaccustomed eccentric exercise may induce neuroplastic changes in nociceptive pathways resulting in wider distribution of pain and hypoesthesia. Futures studies examining the effect of DOMS related somatosensory changes on postural control may be warranted. LEVEL OF EVIDENCE: 3.

A Subgroup of Chronic Low Back Pain Patients With Central Sensitization.

BACKGROUND: Our knowledge of central sensitization (CS) in chronic low back pain (CLBP) is limited. 2011 fibromyalgia criteria and severity scales (2011 FM survey) have been used to determine FM positive as a surrogate of CS. The major features of CS including widespread hyperalgesia and dysfunction of the descending inhibitory pathways can be identified by pressure pain threshold (PPT) and conditioned pain modulation (CPM) tests. The purpose of the study was to examine neurophysiological characteristics and psychosocial symptoms in a subgroup of FM-positive CLBP compared with FM-negative CLBP patients. METHODS: A total of 46 participants with CLBP and 22 pain-free controls completed outcome measures of the 2011 FM survey, PPT and CPM tests, and psychosocial questionnaires. Differences between FM-positive and FM-negative CLBP participants on these measures and correlations were analyzed. RESULTS: The 2011 FM survey identified 22 (48%) participants with CLBP as FM positive. FM-positive CLBP participants showed lower PPT values of the thumbnail (P=0.011) and lower back (P=0.003), lower CPM values of the thumbnail (P=0.002), and more severe pain catastrophizing, anxiety, and depression symptoms (P<0.05) than FM-negative CLBP participants. The 2011 FM scores were significantly correlated with the PPT and CPM values of the thumbnail and with psychosocial symptoms (P<0.001). DISCUSSION: Our findings suggest a subgroup of CLBP patients exhibiting with signs and symptoms of CS. Associations between subjective and objective CS measures indicate that the 2011 FM survey can be utilized to identify the presence of CS in CLBP in clinical practice.