Manual Therapy xxx (2014) 1e8
Contents lists available at ScienceDirect
Manual Therapy journal homepage: www.elsevier.com/math
Original article
Sensory characteristics of chronic non-specific low back pain: A subgroup investigationq Peter O’Sullivan*, Robert Waller, Anthony Wright, Joseph Gardner, Richard Johnston, Carly Payne, Aedin Shannon, Brendan Ware, Anne Smith School of Physiotherapy & Exercise Science, Curtin University, GPO Box 1987, Perth, WA 6845, Australia
a r t i c l e i n f o
a b s t r a c t
Article history: Received 22 May 2013 Received in revised form 6 March 2014 Accepted 14 March 2014
It has been proposed that patients with chronic non-specific low back pain (CNSLBP) can be broadly classified based on clinical features that represent either predominantly a mechanical pain (MP) or nonmechanical pain (NMP) profile. The aim of this study was to establish if patients with CNSLBP who report features of NMP demonstrate differences in pain thresholds compared to those who report MP characteristics and pain-free controls. This study was a cross-sectional design investigating whether pressure pain threshold (PPT) and/or cold pain threshold (CPT) at three anatomical locations differed between patients with mechanical CNSLBP (n ¼ 17) versus non-mechanical CNSLBP (n ¼ 19 and healthy controls (n ¼ 19) whilst controlling for confounders. The results of this study provide evidence of increased CPT at the wrist in the NMP profile group compared to both the MP profile and control subjects, when controlling for gender, sleep and depression (NMP versus MP group Odds Ratio (OR): 18.4, 95% confidence interval (CI): 2.5e133.1, p ¼ 0.004). There was no evidence of lowered PPT at any site after adjustment for confounding factors. Those with an MP profile had similar pain thresholds to pain-free controls, whereas the NMP profile group demonstrated elevated CPT’s consistent with central amplification of pain. These findings may represent different pain mechanisms associated with these patient profiles and may have implications for targeted management. Ó 2014 Published by Elsevier Ltd.
Keywords: Pain sensitivity Chronic non-specific low back pain Biopsychosocial Classification
1. Introduction Patients with chronic non-specific low back pain (CNSLBP) pose a complex diagnostic and management challenge. Classification systems (CS) that identify mechanisms that underlie the pain disorder have been advocated in clinical practice in order to better target interventions (O’Sullivan, 2012a, 2005; Woolf, 2011). The Quebec Task Force CS (Spitzer, 1987) whilst differentiating specific pathology and radicular pain from CNSLBP, does not further differentiate subjects with CNSLBP (Dankaerts et al., 2006). A recent review of clinical CS’s for CNSLBP concluded that a limitation of the majority of CS’s is that they do not consider underlying pain mechanisms and focus largely on biomechanical assessment (Karayannis et al., 2012). A multidimensional CS system for LBP has been proposed that at the first level triages people with LBP to identify red flag disorders q Ethical approval for this study was granted by the Curtin University Human Research Ethics Committee (PT0180). * Corresponding author. Tel.: þ61 8 9266 3629; fax: þ61 8 9266 3699. E-mail address: [email protected] (P. O’Sullivan).
and specific pathology from non-specific LBP (Fig. 1). Once identified, CNSLBP disorders are further differentiated on the basis of their pain characteristic’s reflecting a spectrum from either ‘mechanical pain’ (MP) to ‘non-mechanical pain’ (NMP) (Fig. 1). This is based on routine clinical examination of the patient’s reported pain characteristics linked to aggravating and easing factors and pain responses to movement and loading tests (O’Sullivan, 2005, 2012b; Vibe Fersum et al., 2009, 2012). While it is acknowledged that for some patients there may be a mixed pain profile for others the clinical distinction is clear. It is postulated that these groups may have different underlying neurophysiological mechanisms, where pain in the MP group is related to processes of peripheral sensitisation and some degree of activity dependent central sensitisation, whereas pain in the NMP group is related to more extensive changes in central pain processing. Other dimensions such as pain type, psychosocial, lifestyle, and movement related factors as well as pain comorbidities are also considered in the CS (O’Sullivan, 2005, 2012b; Vibe Fersum et al., 2009). Although this CS has previously been shown to have good inter-rater reliability for identification of aspects of the CS related to movement and psychological profiles (Vibe Fersum et al., 2009), no pain sensitivity (PS) testing
http://dx.doi.org/10.1016/j.math.2014.03.006 1356-689X/Ó 2014 Published by Elsevier Ltd.
Please cite this article in press as: O’Sullivan P, et al., Sensory characteristics of chronic non-specific low back pain: A subgroup investigation, Manual Therapy (2014), http://dx.doi.org/10.1016/j.math.2014.03.006
2
P. O’Sullivan et al. / Manual Therapy xxx (2014) 1e8
Fig. 1. Multidimensional classification of LBP disorders adapted from O’Sullivan, 2005, 2012b; Vibe Fersum et al., 2009, 2012.
has been conducted to quantify the sensory profiles associated with these pain characteristic profiles. Both cold hyperalgesia and widespread pressure hyperalgesia are believed to be indicative of central hyperexcitability (Woolf, 2011). Pain Sensitivity testing is used to assess sensory presentations in various pain disorders (Rolke et al., 2006a) however little research has investigated PS in CNSLBP disorders and controversy exists regarding its value in understanding these disorders (Hubsher et al., 2013). A recent narrative review of available literature in CLBP concluded that currently the available research demonstrates mixed results, with some studies documenting reduced pain thresholds suggestive of widespread or extrasegmental hyperalgesia, other studies observe only segmental hyperalgesia and others reporting no hyperalgesia at all (Roussel et al., 2013). Another recent systematic review investigating the relationship between pain thresholds and pain intensity and disability levels in LBP and neck pain patients, concluded that pain thresholds are a poor marker for patients pain and disability levels (Hubsher et al., 2013). The apparent conflict between these findings
may reflect the heterogeneity of subjects in the different studies, with the potential for different pain phenotypes in the CNSCLP population unaccounted for by study design (Giesecke et al., 2004; Roussel et al., 2013). Both sensory perception and sensory testing are potentially influenced by a number of factors other than pain, such as gender, age, genetics, body composition, sleep and psychosocial factors (Dunn, 1997; O’Sullivan et al., 2008; Leboeuf-Yde et al., 2009; Heffner et al., 2011; Woolf, 2011), highlighting the need to consider these factors when conducting research into PS. While there is limited research investigating whether the presence of CNSLBP is associated with PS changes independent of these factors, a recent study reported that pressure pain threshold (PPT) was most predictive of CNSLBP independent of age, gender, body composition and psychological factors (Neziri et al., 2012). Therefore the primary aim of this study was to investigate whether patients with CNSLBP who report features of NMP demonstrate differences in cold pain threshold (CPT) and PPT compared to those who report MP characteristics and pain-free controls.
Please cite this article in press as: O’Sullivan P, et al., Sensory characteristics of chronic non-specific low back pain: A subgroup investigation, Manual Therapy (2014), http://dx.doi.org/10.1016/j.math.2014.03.006
P. O’Sullivan et al. / Manual Therapy xxx (2014) 1e8
3
2. Materials and methods
2.4. Procedures
2.1. Study design
On the day of testing all participants completed two questionnaires, the Pittsburgh Sleep Quality Index (PSQI) and the Depression Anxiety and Stress Scale (DASS 21), which have established reliability and validity (Buysse et al., 1989; Lovibond and Lovibond, 1995) and were used as covariates to control for the potential confounding effect of poor sleep quality and stress on PS. Age, waist and hip girth were also recorded. Upon agreeing to take part in the study, participants were not asked to stop any of their regular medications. A list of current medications taken over the week prior to testing was documented. Participants with NSCLBP were also asked to complete the following to provide a clinical profile. The pain intensity level of their LBP was measured using the VAS (Huskisson, 1974), and pain areas were recorded using a body chart to provide total areas of pain using the Widespread Pain Index (Wolfe et al., 2010). The Roland Morris Disability Questionnaire (RMDQ) was used to assess functional disability levels and is valid and reliable (Roland and Morris, 1983; Roland and Fairbank, 2000). The StarT Back screening tool (SBST) was used to assess risk profile (Hill et al., 2008). The PainDETECT Questionnaire was used as a validated self-report tool to identify neuropathic pain features. It is an established questionnaire with high sensitivity and specificity (Freynhagen et al., 2006).
A cross-sectional study design was used. 2.2. Participants A total of 53 participants were included in the study; 36 participants with CNSLBP (13 males and 23 females with a mean age of 40.7 (standard deviation (SD) 14.0)) were recruited from local private physiotherapy clinics in the greater Perth area, and 19 painfree controls (8 males and 11 females with a mean age of 41.9 (SD 13.9)) recruited from the same district. Pain participants were included if they had experienced pain for a minimum of 3 months, reported pain intensity on a Visual Analogue Scale (VAS) of 3 or greater on the day of testing and LBP was their primary complaint (from T12 to gluteal fold). Control subjects were included on the basis that they had not reported LBP or any other pain disorder in the previous 6 months. Individuals were excluded if they had been diagnosed with specific spinal pathology or medical causes of low back pain, were pregnant or less than 6 months post-partum or suffered from peripheral neuropathy. In all groups, subjects were excluded if they did not perceive pressure pain below 1000 kPa during PPT testing, or they did not perceive a change in cold sensation during CPT testing. A-priori power calculation determined 18 participants in each group would provide 85% power to detect pairwise differences of at least one standard deviation in mean CPT or PPT assuming a lognormal distribution, at a statistical significance level of 0.05. Ethical approval for this study was granted by the Curtin University Human Research Ethics Committee (PT0180). 2.3. Participants classification The CNSLBP participants, identified following a triage process to exclude red flag and specific pathology, were divided into two groups based on clinical criteria (Fig. 1). Participants in the MP group were included on the basis of: localised and anatomically defined LBP associated with reports of specific and consistent mechanical aggravating and easing factors (LBP that was more intermittent in nature and demonstrated a proportionate pain provocation and easing response to specific postures, activities and movements). Participants in the NMP group were included on the basis of: LBP was more widespread and ill defined, LBP being more constant, non-remitting, spontaneous and where minor mechanical loading factors (such as simple spinal movements) resulted in exaggerated (severe) or prolonged (lasting hours) pain responses (O’Sullivan, 2005). The decision to classify was based on a combination of patient report and response to routine clinical examination. Pain sensitivity testing was not part of this decision making process. Recruitment of the CNSLBP participants occurred across a number of Physiotherapy practices, and consecutive patients were invited to participate if they fulfilled the inclusion criteria. Further screening was performed by RW (Musculoskeletal Physiotherapist with 23 years clinical experience) and POS (Specialist Musculoskeletal Physiotherapist and the developer of the CS who has 25 years clinical experience) both of whom are trained in the CS to ensure the patients fitted the clinical subgroups. A total of 3 participants who agreed to participate were excluded as they failed to meet all the inclusion criteria. One was excluded due to a lack of pain response to pressure, and two had a VAS of less than 3/10 on the day of testing.
2.5. Sensory testing For participants with CNSLBP, the most painful side was tested. The right side was used for those where there was no pain dominant side and for the pain-free controls. Three test sites, the dorsal aspect of the wrist joint line, the L5/SI interspinous space and the lateral calcaneus, were tested in a standardised order and location (Jones, 2007). Each site was tested 4 times with the first test acting as familiarisation with the testing procedure (Wright et al., 1994; Lewis et al., 2010). The testing protocol was strictly followed to limit tester error (Rolke et al., 2006b). Participants were allocated to testers according to time and location of testing, tester allocation was distributed evenly between the three groups, and testers were blinded to pain group allocation. 2.6. Pressure pain thresholds PPT was defined as the moment the sensation of pressure becomes one of pressure and pain (Jones, 2007). The PPT was tested using an algometer (Somedic AB, Sweden) with a contact area of 1 cm2 which was applied perpendicularly to the skin. The pressure increased from 0 kPa at a constant rate of 40 kPa/s until PPT or a maximum of 1000 kPa (Chien and Sterling, 2010) was reached. The standardised instructions were, “Pressure will be applied at a gradual rate. Allow the pressure to increase until it reaches a point where it first feels uncomfortable and then press the button.” Testing was performed by one of two testers (CP, BW). Prior to PPT testing, consistency for PPT measurement between testers was ensured. 2.7. Cold pain thresholds An MSA Thermal stimulator (Somedic AB, Sweden) was used to obtain the CPT. Before assessing CPT a cold detection threshold was obtained for each site to confirm the participant’s ability to detect cold (Mosek et al., 2001). Each test began at a baseline temperature of 32 C, and decreased at 1 C/s until reaching CPT or the automatic minimum cut-off of 5 C (Carli et al., 2002). The standardised instructions were, “The temperature probe will gradually get cooler.
Please cite this article in press as: O’Sullivan P, et al., Sensory characteristics of chronic non-specific low back pain: A subgroup investigation, Manual Therapy (2014), http://dx.doi.org/10.1016/j.math.2014.03.006
4
P. O’Sullivan et al. / Manual Therapy xxx (2014) 1e8
Allow the temperature to drop until it reaches a point where it first feels uncomfortably cold, and then press the button.” Following CPT testing the subjects were asked “Did you feel a sensation other than cold and if yes, how would you describe it?” These responses were divided into ‘cold’ or non-noxious (pressure, nice, cold, tingling, pleasant and numb) and ‘non-cold’ or noxious (burning, ice, sharp, sting, gnawing and freezing) descriptors for further statistical analysis. Previous studies have reported the reliability of CPT measurement (Zwart and Trond, 2002; Wasner and Brock, 2008; Moloney et al., 2012). Testing was performed by one of two testers (AS, BW). 2.8. Statistical analysis The average of 3 trials at each site was used for statistical analysis (Slater et al., 2005). CNSLBP subgroups were examined for differences in clinical profile using chi-squared tests, Fisher’s exact test, ManneWhitney U or KruskaleWallis tests as appropriate. The association between sensory threshold measures and variables considered as covariates (sex, age, waist/hip girth, DASS and PSQI) were examined using chi-squared tests, analysis of variance, ManneWhitney U or KruskaleWallis test as appropriate. Variables with evidence for imbalance among pain groups (p < 0.200) were included in multivariable models. CPT values were suggestive of an underlying bimodal distribution of this measure in the population (see Fig. 2), and all transformations including logarithmic failed to normalise the data. For further analysis we created a dichotomous variable based upon visual examination of the distribution of data for the CPT measure which supported a cut-off point of 15 C as clearly separating two groups in the data (15 C, >15 C, see Fig. 2). This dichotomisation was further supported by k-means cluster analysis, for which a twocluster solution produced two clusters of individuals, with individual CPT measures below and above 15 C. Descriptive statistics and chi-squared tests were used to compare differences in proportions of participants with high CPT at each site between groups. Three binary logistic regressions with high/low CPT at each of the three sites as the outcome variable were used to assess pain group differences adjusting for covariates gender, DASS and PSQI. Differences in frequency of use of non-cold descriptors of sensation experienced during testing between groups were tested using a chi-squared test. PPT measures were log transformed to correct for positive skew. General linear regression models with log transformed PPT measures as the outcome variable were used to assess group differences unadjusted and adjusted for covariates gender, DASS and PSQI (three models for three sites). 95% Confidence intervals with associated p-values are presented for all regression coefficients. All data were analysed using the Statistical Package for Social Sciences (SPSS) student version 18.0
Table 1 Clinical profile of CNSLBP participants. Instrument (max score) VAS (10) Widespread Pain Index (19) RMDQ (24) PainDETECT (39) Nociceptive Unclear Neuropathic StarT Back score (9) Risk category Low Medium High Medication use Non-opioid NSAID Opioid Centrally acting
Mechanical CNSLBP
Non-mechanical CNSLBP
Median (inter-quartile range), minemax 4 (4), 8e17 6 (3), 10e19 2 (2), 1e7 3 (3), 1e9 3 (6), 1e15 Number (percentage 14 of 17 (82%) 3 of 17 (18%) 0
11 (11), 2e20 of pain group) 8 of 19 (42%) 6 of 19 (32%) 5 of 19 (26%)
Number (percentage 11 of 17 (65%) 6 of 17 (35%) 0 of 17 (0%) Number (percentage 1 of 17 (6%) 3 of 17 (18%) 0 of 17 (0%) 2 of 17 (12%)
of pain group) 2 of 19 (11%) 9 of 19 (47%) 8 of 19 (42%) of pain group) 6 of 19 (32%) 8 of 19 (42%) 5 of 19 (26%) 6 of 19 (32%)
p-Value
0.018a 0.014a 0.004a
0.010b
0.001b 0.052b 0.112b 0.023b 0.153b
For each questionnaire, the maximum score is given in brackets. RMDQ, the Roland Morris Disability Questionnaire; VAS, a Visual Analogue Scale for pain on the day of testing; CNSLBP ¼ chronic non-specific low back pain. a Statistical test for group differences is ManneWhitney U test. b Statistical test for group differences is Fisher’s exact test.
(SPSS Inc., Chicago, IL, USA). Data were inputted by one researcher (CP) and cross-checked by a second researcher (AS). 3. Results Nineteen of the CNSLBP participants displayed NMP characteristics (4 males and 15 females with a mean age 42.6 (SD 14.8)) and 17 displayed MP characteristics (9 male and 8 females with a mean age of 39.4 (SD 14.2)). All subjects were screened for health complaints and none reported other co-existing pain conditions, diabetes, endocrine disorders, nervous system disorders or psychiatric disorders. Clinical characteristics of the pain groups are reported in Table 1. The NMP group was characterised by higher pain levels, more pain areas, a larger proportion of neuropathic pain as classified by PainDETECT scores, greater disability, higher risk rating on the SBST and greater frequency of medication use. Fig. 2 presents the untransformed individual values for CPT. Initial univariable analyses provided evidence of group differences in CPT at wrist, lumbar spine and heel sites, and PPT at the lumbar spine site (Table 2). The proportions of subjects with elevated CPTs (>15 C) at the wrist were; control group 26%, MP group 24% and NMP group 84%. There was evidence of some imbalance between groups in DASS total, PSQI and gender, but not age or waist-hip ratio (Table 3), and of various associations between sex, DASS total and
Fig. 2. Untransformed individual values for CPT.
Please cite this article in press as: O’Sullivan P, et al., Sensory characteristics of chronic non-specific low back pain: A subgroup investigation, Manual Therapy (2014), http://dx.doi.org/10.1016/j.math.2014.03.006
P. O’Sullivan et al. / Manual Therapy xxx (2014) 1e8
5
Table 2 Cold pain threshold (CPT) and pressure pain threshold (PPT) measures by participant group. Subgroup Control (n ¼ 19)
Mechanical (n ¼ 17)
Non-mechanical (n ¼ 19)
p-Value
CPT (n (%)>15 C) Wrist Lumbar spine Heel
5 (26.3) 9 (47.4) 6 (31.6)
PPT (median (IQR), mm(Hg)) and Ln(PPT)a (mean (SD)) Wrist (untransformed) 301.3 (141.7) Ln(PPT) 5.73 (0.27) Lumbar spine (untransformed) 352.7 (222.3) Ln(PPT) 5.84 (0.40) Heel (untransformed) 309.3 (151.0) Ln(PPT) 5.76 (0.36)
4 (23.5) 8 (47.1) 9 (52.9)
302.0 5.66 288.7 5.72 315.0 5.78
(177.3) (0.40) (289.0) (0.60) (159.0) (0.40)
16 (84.2) 16 (84.2) 14 (73.7)
239.7 5.59 183.0 5.14 270.3 5.58
(167.7) (0.31) (115.3) (0.71) (109.3) (0.34)
15 C) CPT to those in the MP group. This estimate was similar to the unadjusted odds ratio (OR) of 17.3 (p ¼ 0.001), meaning that sex, DASS total and PSQI were not important confounders of the association between group and CPT. CPT at the lumbar spine and heel sites was not statistically significantly different between NMP and MP groups after adjustment for covariates. At the lumbar spine, patients in the NMP group were estimated to have 5.9 (95% CI: 0.9e38.4, p ¼ 0.064) times the odds of having an elevated (>15 C) CPT to those in the MP group after adjustment for sex, DASS total and PSQI, with the adjusted OR was similar in magnitude to the unadjusted estimate (6.0). At the heel, patients in the NMP had 6.3 (95% CI: 0.9e41.5, p ¼ 0.058) times the odds of having an elevated (>15 C) CPT compared to those in the MP group adjusting for sex, DASS total and PSQI. At this site the adjusted OR (6.3) was larger than the unadjusted OR (2.5) which indicates the likely presence of negative confounding by covariates. At all sites there was no evidence that the MP group had greater or lesser odds than the control group for elevated CPT thresholds. The results of the linear regression models for PPT provided no evidence for group differences at any site (Table 5). Although there was some evidence that the NMP group had lower PPT than the MP group at the lumbar spine for the univariable model (difference: 0.58, 95% CI: 0.97 to 0.19, p ¼ 0.004), the model adjusted for sex, DASS total and PSQI did not confirm a difference existed independently of these covariates (difference: 0.37, 95% CI: 0.83 to 0.09, p ¼ 0.117). There were significant differences in the frequency of reporting of non-cold descriptors (at CPT) between groups at all three sites. Table 6 shows that the NMP group had the highest frequency of non-cold descriptors and controls the lowest. For the wrist and back sites the NMP group had a higher frequency than the MP group. 4. Discussion This study lends support to the presence of differences in PS profile between clinically determined subgroups of CNSLBP
participants based on their pain characteristics, whilst adjusting for potential confounding factors known to influence sensory thresholds. The NMP group was estimated to have at least 2.5 times the odds of having cold hypersensitivity, as defined by a CPT greater than 15 C at the wrist, when compared to the MP CNSLBP group and the pain-free control group (95% CI for OR: 2.5e133.1, p ¼ 0.004), although the sample size was small and consequently confidence intervals for group differences were wide. Estimates of elevated CPT at the lumbar spine and heel were not statistically significant meaning that the null hypothesis of no difference between groups cannot be rejected, however the pattern of larger odds of having cold hypersensitivity in the NMP group is consistent across all three sites, and it is possible that the lack of statistical significance is due to the low power of the study to detect possibly smaller effects at the lumbar spine and heel. Whilst a lower PPT in the NMP group at the lumbar spine was also detected, interestingly there was no statistical evidence for an independent group difference between the MP and control group after controlling for sex, sleep and psychological factors. These findings suggest that the changes in PPT observed in the NMP group may be mediated via gender differences, sleep deficits and/or psychological distress highlighting the multidimensional nature of PS. They also suggest that changes in PPT were limited to the lumbar test site. These findings however are at odds with previous reports where PPT was shown to be the best PS measure to distinguish a group of 40 patients with CNSLBP from pain-free controls after adjusting for age, gender, body compositions and psychological factors (Neziri et al., 2012). The differences in the findings may again reflect different patient profiles and methodological differences. The findings of our study may explain some of the conflicting and variable findings in the previous PS research into CNSLBP disorders (Lewis et al., 2010; Attal et al., 2011; Blumenstiel et al., 2011; O’Neill et al., 2011; Hubsher et al., 2013; Neziri et al., 2012; Roussel et al., 2013), suggesting that NSCLNP is not a homogeneous group and that patient classification is one means by which to deal with this problem. Other authors have also proposed the need to classify NSCLBP patients based on neurophysiological mechanisms (Nijs et al., 2010; Smart et al., 2010; Woolf, 2011). Smart et al. (2010) also described a group of CNSLBP patients with ‘central sensitisation’, defined by pain that is diffuse, lacks clear proportionate mechanical characteristics and present with associated psychological factors. They defined a ‘nociceptive’ CNSLBP group by pain that is more intermittent, localised and responds to clear
Please cite this article in press as: O’Sullivan P, et al., Sensory characteristics of chronic non-specific low back pain: A subgroup investigation, Manual Therapy (2014), http://dx.doi.org/10.1016/j.math.2014.03.006
6
P. O’Sullivan et al. / Manual Therapy xxx (2014) 1e8
Table 3 Association between participant group membership and sex, age, waist:hip ratio, DASS and PSQI scores. Subgroup
Female sex (n (%)) Age (mean (SD)) Waist:hip ratio (mean (SD)) DASS total (0e126a) (median (IQR)) PSQI (0e21a) (mean (SD))
Control (n ¼ 19)
Mechanical (n ¼ 17)
Non-mechanical (n ¼ 19)
p-Value
11 42.6 0.83 10 4.3
8 39.4 0.85 20 7.7
15 41.9 0.85 30 11.0
0.132b 0.788c 0.696c 15 C) and pressure pain (ln(PPT)) threshold measures and sex, age, waist:hip ratio, DASS and PSQI scores. CPT
Sex Age Waist:hip ratio DASS total PSQI
different to the centrally amplified group. Whether this finding represents vulnerability in these subjects to future pain is not known but has been hypothesised previously (Woolf, 2011). The absence of PS differences between the MP and control group may reflect that MP participants’ spinal structures are sensitised to movement and/or load, but not local pressure (O’Sullivan, 2005; Dankaerts et al., 2009), or that the site where the PPT testing was applied was not specific to their pain location. Participants in the MP CNSLBP group also displayed lower levels of psychosocial factors and sleep disturbance (Meeus and Nijs, 2007). Further research is required to determine the relationship between pain characteristics and PS to determine the role that central amplification has on patient clinical profiles.
0.312c* 0.336c*
PPT
0.177c 0.290c*
Bold represent significant findings based on alpha of 0.05. Lx ¼ lumbar spine. *p < 0.05; **p < 0.01. a Measure of association is Pearson correlation coefficient. b Measure of association is Spearman correlation coefficient. c Measure of association is Point-biserial correlation coefficient. d Measure of association is Phi correlation coefficient.
This study was only powered to detect large effect sizes, and consequently may have failed to detect smaller but still clinically meaningful differences between groups. As a consequence of the small sample size, the confidence intervals for the elevated odds of cold hypersensitivity in the NMP group were very wide, limiting
Please cite this article in press as: O’Sullivan P, et al., Sensory characteristics of chronic non-specific low back pain: A subgroup investigation, Manual Therapy (2014), http://dx.doi.org/10.1016/j.math.2014.03.006
P. O’Sullivan et al. / Manual Therapy xxx (2014) 1e8
7
Table 5 Adjusted and unadjusted parameter estimates for group membership from univariable and multivariable binary logistic regression (CPT: 15 C, >15 C) and general linear (ln(PPT)) models (multivariable models adjusted for gender, DASS total and PSQI). Cold pain threshold
Wrist
Unadjusted
Non-mechanical Control Mechanical Non-mechanical Control Mechanical Non-mechanical Control Mechanical
Lx
Heel
Adjusted
Odds ratioa (95% CI)
p-Value
Odds ratio (95% CI)
p-Value
17.3 (3.3, 91.7) 1.2 (0.3, 5.3) REF 6.0 (1.3, 28.5) 1.0 (0.3, 3.8) REF 2.5 (0.6, 10.1) 0.4 (0.1, 1.6) REF
0.001 0.849
18.4 (2.5, 133.1) 1.3 (0.2, 7.0) REF 5.9 (0.9, 38.4) 1.4 (0.3, 6.4) REF 6.3 (0.9, 41.5) 0.3 (0.1, 1.4) REF
0.004 0.759
0.024 0.985 0.201 0.198
0.064 0.637 0.058 0.134
Pressure pain threshold
b (95% CI)b
p-Value
b (95% CI)
p-Value
Wrist
0.07 (0.29, 0.15) 0.08 (0.14, 0.30) REF 0.58 (0.97, -0.19) 0.12 (0.27, 0.51) REF 0.19 (0.43, 0.06) 0.01 (0.26, 0.23) REF
0.551 0.489
0.11 (0.37, 0.15) 0.11 (0.13, 0.35) REF 0.37 (0.83, 0.09) 0.04 (0.38, 0.47) REF 0.22 (0.52, 0.08) 0.01 (0.27, 0.28) REF
0.407 0.347
Non-mechanical Control Mechanical Non-mechanical Control Mechanical Non-mechanical Control Mechanical
Lx
Heel
0.004 0.547 0.133 0.911
0.117 0.838 0.142 0.954
Bold represent significant findings based on alpha of 0.05. a The ratio of the odds for cold pain threshold > 15 C for the test group (non-mechanical or control) to the reference group (mechanical pain group). b Coefficient represents difference in the natural log of pressure pain threshold between test groups (non-mechanical or control) and the reference group (mechanical pain group, positive value indicates higher value in test group).
precise estimation of this association in the population under study. Furthermore, for PPT, testing at a generic site at the lumbar spine may not detect local hyperalgesia. Previous authors have successfully tested PPT in patients with CNSLBP at the site of most severe pain and found it to be predictive with pain, independent of potential confounders (Neziri et al., 2012). Pain medication use was only reported in CNSLBP participants, which precluded use of this variable in the multivariable models presented. However, group differences in medication use were not large (Table 6) and current pain medication use was not associated with CPT or PPT. Other variables only assessed in CNSLBP participants and associated with pain group membership, such as pain intensity, number of pain areas, RMDQ and SBST, were not considered as confounders of the group membership/pain threshold association in this study as they represented part of the common clinical profile of these groups and thus consequences of differential sensory processing. The inter-therapist reliability of the ability of Physiotherapists to differentiate NP from NMP requires further investigation and larger studies are required to verify these results. 5. Conclusion This study provides preliminary evidence that two patient groups with CNSLBP identified clinically, can be distinguished based on their PS profile. When used in conjunction with sound Table 6 Frequency of non-cold descriptorsa cited during the cold pain testing. Controls (n ¼ 19) N (% of group) CPT wrist 3 (15.8) CPT L5/S1 7 (36.8) CPT heel 3 3 (15.8)
Mechanical CNSLBP (n ¼ 17)
Non-mechanical CNSLBP (n ¼ 19)
p-Valueb
6 (35.3) 12 (70.6) 9 (52.9)
12 (63.2) 18 (94.7) 11 (57.9)
0.010 0.001 0.017
a Non-cold descriptors used were ‘burning, ice, sharp, sting, gnawing and freezing’. Any other descriptions were not included as non-cold descriptors. These were ‘pressure, nice, cold, tingling, pleasant and numb’. b Chi-squared test.
clinical reasoning, these profiles may help clinicians more accurately identify mechanisms that underlie CNSLBP and better target interventions. While these pain profiles have yet to be further validated, they provide a framework for future research. Author contributions All authors discussed the results and contributed to the manuscript. References Attal N, Perrot S, Fermanian J, Bouhassira D. The neuropathic components of chronic low back pain: a prospective multicenter study using the DN4 questionnaire. J Pain 2011;12:1080e7. Blumenstiel KMD, Gerhardt AMA, Rolke RMD, Bieber CMD, Tesarz JMD, Friederich H-CMD, et al. Quantitative sensory testing profiles in chronic back pain are distinct from those in fibromyalgia. Clin J Pain 2011;27:682e90. Buysse D, Reynolds C, Monk T, Berman S, Kupfer D. The Pittsburgh sleep quality index: a new instrument for psychiatric practice and research. Psychiatry Res 1989;28:193e213. Campbell C, Edwards R. Mindebody interactions in pain: the neurophysiology of anxious and catastrophic pain-related thoughts. Transl Res 2009;153:97e101. Carli G, Suman AL, Biasi G, Marcolongo R. Reactivity to superficial and deep stimuli in patients with chronic musculoskeletal pain. Pain 2002;100:259e69. Chien A, Sterling M. Sensory hypoaesthesia is a feature of chronic whiplash but not chronic idiopathic neck pain. Man Ther 2010;15:48e53. Dankaerts W, O’Sullivan P, Burnett A, Straker L. Differences in sitting postures are associated with nonspecific chronic low back pain disorders when patients are subclassified. Spine 2006;31:698e704. Dankaerts W, O’Sullivan P, Burnett A, Straker L, Davey P, Gupta R. Discriminating healthy controls and two clinical subgroups of nonspecific chronic low back pain patients using trunk muscle activation and lumbosacral kinematics of postures and movements. Spine 2009;34:1610e8. Deyo RA, Mirza SK, Turner JA, Martin BI. Overtreating chronic back pain: time to back off? J Am Board Fam Med 2009;22:62e8. Dunn W. The impact of sensory processing abilities on the daily lives of young children and their families: a conceptual model. Infants Young Child 1997;9: 23e35. Freynhagen R, Baron R, Gockel U, Tolle T. painDETECT: a new screening questionnaire to identify neuropathic components in patients with back pain. Curr Med Res Opin 2006;22:1911e20. Giesecke T, Gracely RH, Grant MAB, Nachemson AL, Petzke F, Williams DA, et al. Evidence of augmented central pain processing in idiopathic chronic low back pain. Arthritis Rheum 2004;50:613e23.
Please cite this article in press as: O’Sullivan P, et al., Sensory characteristics of chronic non-specific low back pain: A subgroup investigation, Manual Therapy (2014), http://dx.doi.org/10.1016/j.math.2014.03.006
8
P. O’Sullivan et al. / Manual Therapy xxx (2014) 1e8
Heffner K, France C, Trost Z, Ng H, Pigeon W. Chronic low back pain, sleep disturbance, and interleukin-6. Clin J Pain 2011;27:35e41. Hill JC, Dunn KM, Lewis M, Mullis R, Main CJ, Foster NE, et al. A primary care back pain screening tool: identifying patient subgroups for initial treatment. Arthritis Rheum 2008;59:632e41. Hubsher M, Moloney N, Leaver A, Rebbeck T, McAuley J, Refshauge K. Relationship between quantitative sensory testing and pain or disability in people with spinal pain e a systematic review and meta-analysis. Pain 2013;154:1497e504. Huskisson EC. Measurement of pain. Lancet 1974;2:1127e31. Jones D. Testeretest reliability of pressure pain threshold measurements of the upper limb and torso in young healthy women. J Pain 2007;8:650e6. Karayannis NV, Jull GA, Hodges PW. Physiotherapy movement based classification approaches to low back pain: comparison of subgroups through review and developer/expert survey. BMC Musculoskelet Disord 2012;13:24. Kasch H, Qerama E, Bach FW, Jensen TS. Reduced cold pressor pain tolerance in nonrecovered whiplash patients: a 1-year prospective study. Eur J Pain 2005;9: 561e9. Leboeuf-Yde C, Nielsen J, Kyvik K, Fejer R, Hartvigsen J. Pain in the lumbar, thoracic and cervical regions: do age and gender matter? A population-based study of 34,902 Danish twins 20e71 years of age. BMC Musculoskelet Disord 2009;10. Lewis C, Khan A, Souvlis T, Sterling M. Sensory characteristics of tender points in the lower back. Man Ther 2010;15:536e41. Lovibond S, Lovibond P. Manual for the depression anxiety stress scales; 1995. Maxwell S, Sterling M. An investigation of the use of a numeric pain rating scale with ice application to the neck to determine cold hyperalgesia. Man Ther 2013;18:172e4. Meeus M, Nijs J. Central sensitization: a biopsychosocial explanation for chronic widespread pain in patients with fibromyalgia and chronic fatigue syndrome. Clin Rheumatol 2007;26:465e73. Moloney NA, Hall TM, Doody CM. Reliability of thermal quantitative sensory testing: a systematic review. J Rehabil Res Dev 2012;49:191e207. Mosek A, Yarnitsky D, Korczyn AD, Niv D. The assessment of radiating low back pain by thermal sensory testing. Eur J Pain 2001;5:347e51. Neziri A, Curatolo M, Limacher A, Nüesch E, Radanov B, Andersen O, et al. Ranking of parameters of pain hypersensitivity according to their discriminative ability in chronic low back pain. Pain 2012;153:2083e91. Nijs J, Van Houdenhove B, Oostendorp RAB. Recognition of central sensitization in patients with musculoskeletal pain: application of pain neurophysiology in manual therapy practice. Man Ther 2010;15:135e41. O’Sullivan P. Diagnosis and classification of chronic low back pain disorders: maladaptive movement and motor control impairments as underlying mechanism. Man Ther 2005;10:242e55. O’Sullivan P, Straker L, Smith A, Perry M, Kendall G. Carer experience of back pain is associated with adolescent back pain experience even when controlling for other carer and family factors. Clin J Pain 2008;24:226e31. O’Sullivan P. It’s time for change in the management of non-specific chronic low back pain. Br J Sports Med 2012a;46:224e7.
O’Sullivan PB. A classification-based cognitive functional approach for the management of back pain. J Orthop Sports Phys Ther 2012b;42:A17e21. O’Neill S, Kjær P, Graven-Nielsen T, Manniche C, Arendt-Nielsen L. Low pressure pain thresholds are associated with, but does not predispose for, low back pain. Eur Spine J 2011;20:2120e5. Roland M, Fairbank J. The RolandeMorris disability questionnaire and the Oswestry disability questionnaire. Spine 2000;25:3115e24. Roland M, Morris R. A study of the natural history of back pain. Spine 1983;8:141e4. Rolke R, Baron R, Maier C, Tolle TR, Treede RD, Beyer A, et al. Quantitative sensory testing in the German research network on neuropathic pain (DFNS): standardized protocol and reference values. Pain 2006a;123:231e43. Rolke R, Baron R, Maier C, Tölle TR, Treede RD, Beyer A, et al. Quantitative sensory testing in the German research network on neuropathic pain (DFNS): standardized protocol and reference values. Pain 2006b;123:231e43. Roussel NAPMPT, Nijs JPMPT, Meeus MPPT, Mylius VPMD, Fayt CPMD, Oostendorp RPMPTPT. Central sensitization and altered central pain processing in chronic low back pain: fact or myth? Clin J Pain 2013;29:625e38. Scott D, Jull G, Sterling M. Widespread sensory hypersensitivity is a feature of chronic whiplash-associated disorder but not chronic idiopathic neck pain. Clin J Pain 2005;21:175e81. Slater H, Arendtnielsen L, Wright A, Gravennielsen T. Sensory and motor effects of experimental muscle pain in patients with lateral epicondylalgia and controls with delayed onset muscle soreness. Pain 2005;114:118e30. Smart K, Blake C, Staines A, Doody C. Clinical indicators of ‘nociceptive’, ‘peripheral neuropathic’ and ‘central’ mechanisms of musculoskeletal pain. A Delphi survey of expert clinicians. Man Ther 2010;15:80e7. Spitzer WO. Scientific approach to the assessment and management of activityrelated spinal disorders: a monograph for clinicians. Report of the Quebec task force on spinal disorders. Spine 1987;12:1e59. Vibe Fersum K, O’Sullivan PB, Kvåle A, Skouen JS. Inter-examiner reliability of a classification system for patients with non-specific low back pain. Man Ther 2009;14:555e61. Vibe Fersum K, O’Sullivan P, Skouen JS, Smith A, Kvåle A. Efficacy of classification based ‘cognitive functional therapy’ in patients with Non Specific Chronic Low Back Pain – a randomized controlled trial. Eur Pain J 2012;17(6):916e28. Wasner GL, Brock JA. Determinants of thermal pain thresholds in normal subjects. Clin Neurophysiol 2008;119:2389e95. Wolfe F, Clauw D, Fitzcharles M, Goldenberg D, Katz R, Mease P, et al. The American College of Rheumatology preliminary diagnostic criteria for fibromyalgia and measurement of symptom severity. Arthritis Care Res 2010;62:600e10. Woolf C, Mannion R. Neuropathic pain: aetiology, symptoms, mechanisms, and management. Lancet 1999;353:1959e64. Woolf CJ. Central sensitization: implications for the diagnosis and treatment of pain. Pain 2011;152:S2e15. Wright A, Thurnwald P, O’Callaghan J, Smith J, Vicenzino B. Hyperalgesia in tennis elbow patients. J Musculoskelet Pain 1994;2:83e97. Zwart J-A, Trond S. Repeatability of dermatomal warm and cold sensory thresholds in patients with sciatica. Eur Spine J 2002;11:441e6.
Please cite this article in press as: O’Sullivan P, et al., Sensory characteristics of chronic non-specific low back pain: A subgroup investigation, Manual Therapy (2014), http://dx.doi.org/10.1016/j.math.2014.03.006
Contents lists available at ScienceDirect
Manual Therapy journal homepage: www.elsevier.com/math
Original article
Sensory characteristics of chronic non-specific low back pain: A subgroup investigationq Peter O’Sullivan*, Robert Waller, Anthony Wright, Joseph Gardner, Richard Johnston, Carly Payne, Aedin Shannon, Brendan Ware, Anne Smith School of Physiotherapy & Exercise Science, Curtin University, GPO Box 1987, Perth, WA 6845, Australia
a r t i c l e i n f o
a b s t r a c t
Article history: Received 22 May 2013 Received in revised form 6 March 2014 Accepted 14 March 2014
It has been proposed that patients with chronic non-specific low back pain (CNSLBP) can be broadly classified based on clinical features that represent either predominantly a mechanical pain (MP) or nonmechanical pain (NMP) profile. The aim of this study was to establish if patients with CNSLBP who report features of NMP demonstrate differences in pain thresholds compared to those who report MP characteristics and pain-free controls. This study was a cross-sectional design investigating whether pressure pain threshold (PPT) and/or cold pain threshold (CPT) at three anatomical locations differed between patients with mechanical CNSLBP (n ¼ 17) versus non-mechanical CNSLBP (n ¼ 19 and healthy controls (n ¼ 19) whilst controlling for confounders. The results of this study provide evidence of increased CPT at the wrist in the NMP profile group compared to both the MP profile and control subjects, when controlling for gender, sleep and depression (NMP versus MP group Odds Ratio (OR): 18.4, 95% confidence interval (CI): 2.5e133.1, p ¼ 0.004). There was no evidence of lowered PPT at any site after adjustment for confounding factors. Those with an MP profile had similar pain thresholds to pain-free controls, whereas the NMP profile group demonstrated elevated CPT’s consistent with central amplification of pain. These findings may represent different pain mechanisms associated with these patient profiles and may have implications for targeted management. Ó 2014 Published by Elsevier Ltd.
Keywords: Pain sensitivity Chronic non-specific low back pain Biopsychosocial Classification
1. Introduction Patients with chronic non-specific low back pain (CNSLBP) pose a complex diagnostic and management challenge. Classification systems (CS) that identify mechanisms that underlie the pain disorder have been advocated in clinical practice in order to better target interventions (O’Sullivan, 2012a, 2005; Woolf, 2011). The Quebec Task Force CS (Spitzer, 1987) whilst differentiating specific pathology and radicular pain from CNSLBP, does not further differentiate subjects with CNSLBP (Dankaerts et al., 2006). A recent review of clinical CS’s for CNSLBP concluded that a limitation of the majority of CS’s is that they do not consider underlying pain mechanisms and focus largely on biomechanical assessment (Karayannis et al., 2012). A multidimensional CS system for LBP has been proposed that at the first level triages people with LBP to identify red flag disorders q Ethical approval for this study was granted by the Curtin University Human Research Ethics Committee (PT0180). * Corresponding author. Tel.: þ61 8 9266 3629; fax: þ61 8 9266 3699. E-mail address: [email protected] (P. O’Sullivan).
and specific pathology from non-specific LBP (Fig. 1). Once identified, CNSLBP disorders are further differentiated on the basis of their pain characteristic’s reflecting a spectrum from either ‘mechanical pain’ (MP) to ‘non-mechanical pain’ (NMP) (Fig. 1). This is based on routine clinical examination of the patient’s reported pain characteristics linked to aggravating and easing factors and pain responses to movement and loading tests (O’Sullivan, 2005, 2012b; Vibe Fersum et al., 2009, 2012). While it is acknowledged that for some patients there may be a mixed pain profile for others the clinical distinction is clear. It is postulated that these groups may have different underlying neurophysiological mechanisms, where pain in the MP group is related to processes of peripheral sensitisation and some degree of activity dependent central sensitisation, whereas pain in the NMP group is related to more extensive changes in central pain processing. Other dimensions such as pain type, psychosocial, lifestyle, and movement related factors as well as pain comorbidities are also considered in the CS (O’Sullivan, 2005, 2012b; Vibe Fersum et al., 2009). Although this CS has previously been shown to have good inter-rater reliability for identification of aspects of the CS related to movement and psychological profiles (Vibe Fersum et al., 2009), no pain sensitivity (PS) testing
http://dx.doi.org/10.1016/j.math.2014.03.006 1356-689X/Ó 2014 Published by Elsevier Ltd.
Please cite this article in press as: O’Sullivan P, et al., Sensory characteristics of chronic non-specific low back pain: A subgroup investigation, Manual Therapy (2014), http://dx.doi.org/10.1016/j.math.2014.03.006
2
P. O’Sullivan et al. / Manual Therapy xxx (2014) 1e8
Fig. 1. Multidimensional classification of LBP disorders adapted from O’Sullivan, 2005, 2012b; Vibe Fersum et al., 2009, 2012.
has been conducted to quantify the sensory profiles associated with these pain characteristic profiles. Both cold hyperalgesia and widespread pressure hyperalgesia are believed to be indicative of central hyperexcitability (Woolf, 2011). Pain Sensitivity testing is used to assess sensory presentations in various pain disorders (Rolke et al., 2006a) however little research has investigated PS in CNSLBP disorders and controversy exists regarding its value in understanding these disorders (Hubsher et al., 2013). A recent narrative review of available literature in CLBP concluded that currently the available research demonstrates mixed results, with some studies documenting reduced pain thresholds suggestive of widespread or extrasegmental hyperalgesia, other studies observe only segmental hyperalgesia and others reporting no hyperalgesia at all (Roussel et al., 2013). Another recent systematic review investigating the relationship between pain thresholds and pain intensity and disability levels in LBP and neck pain patients, concluded that pain thresholds are a poor marker for patients pain and disability levels (Hubsher et al., 2013). The apparent conflict between these findings
may reflect the heterogeneity of subjects in the different studies, with the potential for different pain phenotypes in the CNSCLP population unaccounted for by study design (Giesecke et al., 2004; Roussel et al., 2013). Both sensory perception and sensory testing are potentially influenced by a number of factors other than pain, such as gender, age, genetics, body composition, sleep and psychosocial factors (Dunn, 1997; O’Sullivan et al., 2008; Leboeuf-Yde et al., 2009; Heffner et al., 2011; Woolf, 2011), highlighting the need to consider these factors when conducting research into PS. While there is limited research investigating whether the presence of CNSLBP is associated with PS changes independent of these factors, a recent study reported that pressure pain threshold (PPT) was most predictive of CNSLBP independent of age, gender, body composition and psychological factors (Neziri et al., 2012). Therefore the primary aim of this study was to investigate whether patients with CNSLBP who report features of NMP demonstrate differences in cold pain threshold (CPT) and PPT compared to those who report MP characteristics and pain-free controls.
Please cite this article in press as: O’Sullivan P, et al., Sensory characteristics of chronic non-specific low back pain: A subgroup investigation, Manual Therapy (2014), http://dx.doi.org/10.1016/j.math.2014.03.006
P. O’Sullivan et al. / Manual Therapy xxx (2014) 1e8
3
2. Materials and methods
2.4. Procedures
2.1. Study design
On the day of testing all participants completed two questionnaires, the Pittsburgh Sleep Quality Index (PSQI) and the Depression Anxiety and Stress Scale (DASS 21), which have established reliability and validity (Buysse et al., 1989; Lovibond and Lovibond, 1995) and were used as covariates to control for the potential confounding effect of poor sleep quality and stress on PS. Age, waist and hip girth were also recorded. Upon agreeing to take part in the study, participants were not asked to stop any of their regular medications. A list of current medications taken over the week prior to testing was documented. Participants with NSCLBP were also asked to complete the following to provide a clinical profile. The pain intensity level of their LBP was measured using the VAS (Huskisson, 1974), and pain areas were recorded using a body chart to provide total areas of pain using the Widespread Pain Index (Wolfe et al., 2010). The Roland Morris Disability Questionnaire (RMDQ) was used to assess functional disability levels and is valid and reliable (Roland and Morris, 1983; Roland and Fairbank, 2000). The StarT Back screening tool (SBST) was used to assess risk profile (Hill et al., 2008). The PainDETECT Questionnaire was used as a validated self-report tool to identify neuropathic pain features. It is an established questionnaire with high sensitivity and specificity (Freynhagen et al., 2006).
A cross-sectional study design was used. 2.2. Participants A total of 53 participants were included in the study; 36 participants with CNSLBP (13 males and 23 females with a mean age of 40.7 (standard deviation (SD) 14.0)) were recruited from local private physiotherapy clinics in the greater Perth area, and 19 painfree controls (8 males and 11 females with a mean age of 41.9 (SD 13.9)) recruited from the same district. Pain participants were included if they had experienced pain for a minimum of 3 months, reported pain intensity on a Visual Analogue Scale (VAS) of 3 or greater on the day of testing and LBP was their primary complaint (from T12 to gluteal fold). Control subjects were included on the basis that they had not reported LBP or any other pain disorder in the previous 6 months. Individuals were excluded if they had been diagnosed with specific spinal pathology or medical causes of low back pain, were pregnant or less than 6 months post-partum or suffered from peripheral neuropathy. In all groups, subjects were excluded if they did not perceive pressure pain below 1000 kPa during PPT testing, or they did not perceive a change in cold sensation during CPT testing. A-priori power calculation determined 18 participants in each group would provide 85% power to detect pairwise differences of at least one standard deviation in mean CPT or PPT assuming a lognormal distribution, at a statistical significance level of 0.05. Ethical approval for this study was granted by the Curtin University Human Research Ethics Committee (PT0180). 2.3. Participants classification The CNSLBP participants, identified following a triage process to exclude red flag and specific pathology, were divided into two groups based on clinical criteria (Fig. 1). Participants in the MP group were included on the basis of: localised and anatomically defined LBP associated with reports of specific and consistent mechanical aggravating and easing factors (LBP that was more intermittent in nature and demonstrated a proportionate pain provocation and easing response to specific postures, activities and movements). Participants in the NMP group were included on the basis of: LBP was more widespread and ill defined, LBP being more constant, non-remitting, spontaneous and where minor mechanical loading factors (such as simple spinal movements) resulted in exaggerated (severe) or prolonged (lasting hours) pain responses (O’Sullivan, 2005). The decision to classify was based on a combination of patient report and response to routine clinical examination. Pain sensitivity testing was not part of this decision making process. Recruitment of the CNSLBP participants occurred across a number of Physiotherapy practices, and consecutive patients were invited to participate if they fulfilled the inclusion criteria. Further screening was performed by RW (Musculoskeletal Physiotherapist with 23 years clinical experience) and POS (Specialist Musculoskeletal Physiotherapist and the developer of the CS who has 25 years clinical experience) both of whom are trained in the CS to ensure the patients fitted the clinical subgroups. A total of 3 participants who agreed to participate were excluded as they failed to meet all the inclusion criteria. One was excluded due to a lack of pain response to pressure, and two had a VAS of less than 3/10 on the day of testing.
2.5. Sensory testing For participants with CNSLBP, the most painful side was tested. The right side was used for those where there was no pain dominant side and for the pain-free controls. Three test sites, the dorsal aspect of the wrist joint line, the L5/SI interspinous space and the lateral calcaneus, were tested in a standardised order and location (Jones, 2007). Each site was tested 4 times with the first test acting as familiarisation with the testing procedure (Wright et al., 1994; Lewis et al., 2010). The testing protocol was strictly followed to limit tester error (Rolke et al., 2006b). Participants were allocated to testers according to time and location of testing, tester allocation was distributed evenly between the three groups, and testers were blinded to pain group allocation. 2.6. Pressure pain thresholds PPT was defined as the moment the sensation of pressure becomes one of pressure and pain (Jones, 2007). The PPT was tested using an algometer (Somedic AB, Sweden) with a contact area of 1 cm2 which was applied perpendicularly to the skin. The pressure increased from 0 kPa at a constant rate of 40 kPa/s until PPT or a maximum of 1000 kPa (Chien and Sterling, 2010) was reached. The standardised instructions were, “Pressure will be applied at a gradual rate. Allow the pressure to increase until it reaches a point where it first feels uncomfortable and then press the button.” Testing was performed by one of two testers (CP, BW). Prior to PPT testing, consistency for PPT measurement between testers was ensured. 2.7. Cold pain thresholds An MSA Thermal stimulator (Somedic AB, Sweden) was used to obtain the CPT. Before assessing CPT a cold detection threshold was obtained for each site to confirm the participant’s ability to detect cold (Mosek et al., 2001). Each test began at a baseline temperature of 32 C, and decreased at 1 C/s until reaching CPT or the automatic minimum cut-off of 5 C (Carli et al., 2002). The standardised instructions were, “The temperature probe will gradually get cooler.
Please cite this article in press as: O’Sullivan P, et al., Sensory characteristics of chronic non-specific low back pain: A subgroup investigation, Manual Therapy (2014), http://dx.doi.org/10.1016/j.math.2014.03.006
4
P. O’Sullivan et al. / Manual Therapy xxx (2014) 1e8
Allow the temperature to drop until it reaches a point where it first feels uncomfortably cold, and then press the button.” Following CPT testing the subjects were asked “Did you feel a sensation other than cold and if yes, how would you describe it?” These responses were divided into ‘cold’ or non-noxious (pressure, nice, cold, tingling, pleasant and numb) and ‘non-cold’ or noxious (burning, ice, sharp, sting, gnawing and freezing) descriptors for further statistical analysis. Previous studies have reported the reliability of CPT measurement (Zwart and Trond, 2002; Wasner and Brock, 2008; Moloney et al., 2012). Testing was performed by one of two testers (AS, BW). 2.8. Statistical analysis The average of 3 trials at each site was used for statistical analysis (Slater et al., 2005). CNSLBP subgroups were examined for differences in clinical profile using chi-squared tests, Fisher’s exact test, ManneWhitney U or KruskaleWallis tests as appropriate. The association between sensory threshold measures and variables considered as covariates (sex, age, waist/hip girth, DASS and PSQI) were examined using chi-squared tests, analysis of variance, ManneWhitney U or KruskaleWallis test as appropriate. Variables with evidence for imbalance among pain groups (p < 0.200) were included in multivariable models. CPT values were suggestive of an underlying bimodal distribution of this measure in the population (see Fig. 2), and all transformations including logarithmic failed to normalise the data. For further analysis we created a dichotomous variable based upon visual examination of the distribution of data for the CPT measure which supported a cut-off point of 15 C as clearly separating two groups in the data (15 C, >15 C, see Fig. 2). This dichotomisation was further supported by k-means cluster analysis, for which a twocluster solution produced two clusters of individuals, with individual CPT measures below and above 15 C. Descriptive statistics and chi-squared tests were used to compare differences in proportions of participants with high CPT at each site between groups. Three binary logistic regressions with high/low CPT at each of the three sites as the outcome variable were used to assess pain group differences adjusting for covariates gender, DASS and PSQI. Differences in frequency of use of non-cold descriptors of sensation experienced during testing between groups were tested using a chi-squared test. PPT measures were log transformed to correct for positive skew. General linear regression models with log transformed PPT measures as the outcome variable were used to assess group differences unadjusted and adjusted for covariates gender, DASS and PSQI (three models for three sites). 95% Confidence intervals with associated p-values are presented for all regression coefficients. All data were analysed using the Statistical Package for Social Sciences (SPSS) student version 18.0
Table 1 Clinical profile of CNSLBP participants. Instrument (max score) VAS (10) Widespread Pain Index (19) RMDQ (24) PainDETECT (39) Nociceptive Unclear Neuropathic StarT Back score (9) Risk category Low Medium High Medication use Non-opioid NSAID Opioid Centrally acting
Mechanical CNSLBP
Non-mechanical CNSLBP
Median (inter-quartile range), minemax 4 (4), 8e17 6 (3), 10e19 2 (2), 1e7 3 (3), 1e9 3 (6), 1e15 Number (percentage 14 of 17 (82%) 3 of 17 (18%) 0
11 (11), 2e20 of pain group) 8 of 19 (42%) 6 of 19 (32%) 5 of 19 (26%)
Number (percentage 11 of 17 (65%) 6 of 17 (35%) 0 of 17 (0%) Number (percentage 1 of 17 (6%) 3 of 17 (18%) 0 of 17 (0%) 2 of 17 (12%)
of pain group) 2 of 19 (11%) 9 of 19 (47%) 8 of 19 (42%) of pain group) 6 of 19 (32%) 8 of 19 (42%) 5 of 19 (26%) 6 of 19 (32%)
p-Value
0.018a 0.014a 0.004a
0.010b
0.001b 0.052b 0.112b 0.023b 0.153b
For each questionnaire, the maximum score is given in brackets. RMDQ, the Roland Morris Disability Questionnaire; VAS, a Visual Analogue Scale for pain on the day of testing; CNSLBP ¼ chronic non-specific low back pain. a Statistical test for group differences is ManneWhitney U test. b Statistical test for group differences is Fisher’s exact test.
(SPSS Inc., Chicago, IL, USA). Data were inputted by one researcher (CP) and cross-checked by a second researcher (AS). 3. Results Nineteen of the CNSLBP participants displayed NMP characteristics (4 males and 15 females with a mean age 42.6 (SD 14.8)) and 17 displayed MP characteristics (9 male and 8 females with a mean age of 39.4 (SD 14.2)). All subjects were screened for health complaints and none reported other co-existing pain conditions, diabetes, endocrine disorders, nervous system disorders or psychiatric disorders. Clinical characteristics of the pain groups are reported in Table 1. The NMP group was characterised by higher pain levels, more pain areas, a larger proportion of neuropathic pain as classified by PainDETECT scores, greater disability, higher risk rating on the SBST and greater frequency of medication use. Fig. 2 presents the untransformed individual values for CPT. Initial univariable analyses provided evidence of group differences in CPT at wrist, lumbar spine and heel sites, and PPT at the lumbar spine site (Table 2). The proportions of subjects with elevated CPTs (>15 C) at the wrist were; control group 26%, MP group 24% and NMP group 84%. There was evidence of some imbalance between groups in DASS total, PSQI and gender, but not age or waist-hip ratio (Table 3), and of various associations between sex, DASS total and
Fig. 2. Untransformed individual values for CPT.
Please cite this article in press as: O’Sullivan P, et al., Sensory characteristics of chronic non-specific low back pain: A subgroup investigation, Manual Therapy (2014), http://dx.doi.org/10.1016/j.math.2014.03.006
P. O’Sullivan et al. / Manual Therapy xxx (2014) 1e8
5
Table 2 Cold pain threshold (CPT) and pressure pain threshold (PPT) measures by participant group. Subgroup Control (n ¼ 19)
Mechanical (n ¼ 17)
Non-mechanical (n ¼ 19)
p-Value
CPT (n (%)>15 C) Wrist Lumbar spine Heel
5 (26.3) 9 (47.4) 6 (31.6)
PPT (median (IQR), mm(Hg)) and Ln(PPT)a (mean (SD)) Wrist (untransformed) 301.3 (141.7) Ln(PPT) 5.73 (0.27) Lumbar spine (untransformed) 352.7 (222.3) Ln(PPT) 5.84 (0.40) Heel (untransformed) 309.3 (151.0) Ln(PPT) 5.76 (0.36)
4 (23.5) 8 (47.1) 9 (52.9)
302.0 5.66 288.7 5.72 315.0 5.78
(177.3) (0.40) (289.0) (0.60) (159.0) (0.40)
16 (84.2) 16 (84.2) 14 (73.7)
239.7 5.59 183.0 5.14 270.3 5.58
(167.7) (0.31) (115.3) (0.71) (109.3) (0.34)
15 C) CPT to those in the MP group. This estimate was similar to the unadjusted odds ratio (OR) of 17.3 (p ¼ 0.001), meaning that sex, DASS total and PSQI were not important confounders of the association between group and CPT. CPT at the lumbar spine and heel sites was not statistically significantly different between NMP and MP groups after adjustment for covariates. At the lumbar spine, patients in the NMP group were estimated to have 5.9 (95% CI: 0.9e38.4, p ¼ 0.064) times the odds of having an elevated (>15 C) CPT to those in the MP group after adjustment for sex, DASS total and PSQI, with the adjusted OR was similar in magnitude to the unadjusted estimate (6.0). At the heel, patients in the NMP had 6.3 (95% CI: 0.9e41.5, p ¼ 0.058) times the odds of having an elevated (>15 C) CPT compared to those in the MP group adjusting for sex, DASS total and PSQI. At this site the adjusted OR (6.3) was larger than the unadjusted OR (2.5) which indicates the likely presence of negative confounding by covariates. At all sites there was no evidence that the MP group had greater or lesser odds than the control group for elevated CPT thresholds. The results of the linear regression models for PPT provided no evidence for group differences at any site (Table 5). Although there was some evidence that the NMP group had lower PPT than the MP group at the lumbar spine for the univariable model (difference: 0.58, 95% CI: 0.97 to 0.19, p ¼ 0.004), the model adjusted for sex, DASS total and PSQI did not confirm a difference existed independently of these covariates (difference: 0.37, 95% CI: 0.83 to 0.09, p ¼ 0.117). There were significant differences in the frequency of reporting of non-cold descriptors (at CPT) between groups at all three sites. Table 6 shows that the NMP group had the highest frequency of non-cold descriptors and controls the lowest. For the wrist and back sites the NMP group had a higher frequency than the MP group. 4. Discussion This study lends support to the presence of differences in PS profile between clinically determined subgroups of CNSLBP
participants based on their pain characteristics, whilst adjusting for potential confounding factors known to influence sensory thresholds. The NMP group was estimated to have at least 2.5 times the odds of having cold hypersensitivity, as defined by a CPT greater than 15 C at the wrist, when compared to the MP CNSLBP group and the pain-free control group (95% CI for OR: 2.5e133.1, p ¼ 0.004), although the sample size was small and consequently confidence intervals for group differences were wide. Estimates of elevated CPT at the lumbar spine and heel were not statistically significant meaning that the null hypothesis of no difference between groups cannot be rejected, however the pattern of larger odds of having cold hypersensitivity in the NMP group is consistent across all three sites, and it is possible that the lack of statistical significance is due to the low power of the study to detect possibly smaller effects at the lumbar spine and heel. Whilst a lower PPT in the NMP group at the lumbar spine was also detected, interestingly there was no statistical evidence for an independent group difference between the MP and control group after controlling for sex, sleep and psychological factors. These findings suggest that the changes in PPT observed in the NMP group may be mediated via gender differences, sleep deficits and/or psychological distress highlighting the multidimensional nature of PS. They also suggest that changes in PPT were limited to the lumbar test site. These findings however are at odds with previous reports where PPT was shown to be the best PS measure to distinguish a group of 40 patients with CNSLBP from pain-free controls after adjusting for age, gender, body compositions and psychological factors (Neziri et al., 2012). The differences in the findings may again reflect different patient profiles and methodological differences. The findings of our study may explain some of the conflicting and variable findings in the previous PS research into CNSLBP disorders (Lewis et al., 2010; Attal et al., 2011; Blumenstiel et al., 2011; O’Neill et al., 2011; Hubsher et al., 2013; Neziri et al., 2012; Roussel et al., 2013), suggesting that NSCLNP is not a homogeneous group and that patient classification is one means by which to deal with this problem. Other authors have also proposed the need to classify NSCLBP patients based on neurophysiological mechanisms (Nijs et al., 2010; Smart et al., 2010; Woolf, 2011). Smart et al. (2010) also described a group of CNSLBP patients with ‘central sensitisation’, defined by pain that is diffuse, lacks clear proportionate mechanical characteristics and present with associated psychological factors. They defined a ‘nociceptive’ CNSLBP group by pain that is more intermittent, localised and responds to clear
Please cite this article in press as: O’Sullivan P, et al., Sensory characteristics of chronic non-specific low back pain: A subgroup investigation, Manual Therapy (2014), http://dx.doi.org/10.1016/j.math.2014.03.006
6
P. O’Sullivan et al. / Manual Therapy xxx (2014) 1e8
Table 3 Association between participant group membership and sex, age, waist:hip ratio, DASS and PSQI scores. Subgroup
Female sex (n (%)) Age (mean (SD)) Waist:hip ratio (mean (SD)) DASS total (0e126a) (median (IQR)) PSQI (0e21a) (mean (SD))
Control (n ¼ 19)
Mechanical (n ¼ 17)
Non-mechanical (n ¼ 19)
p-Value
11 42.6 0.83 10 4.3
8 39.4 0.85 20 7.7
15 41.9 0.85 30 11.0
0.132b 0.788c 0.696c 15 C) and pressure pain (ln(PPT)) threshold measures and sex, age, waist:hip ratio, DASS and PSQI scores. CPT
Sex Age Waist:hip ratio DASS total PSQI
different to the centrally amplified group. Whether this finding represents vulnerability in these subjects to future pain is not known but has been hypothesised previously (Woolf, 2011). The absence of PS differences between the MP and control group may reflect that MP participants’ spinal structures are sensitised to movement and/or load, but not local pressure (O’Sullivan, 2005; Dankaerts et al., 2009), or that the site where the PPT testing was applied was not specific to their pain location. Participants in the MP CNSLBP group also displayed lower levels of psychosocial factors and sleep disturbance (Meeus and Nijs, 2007). Further research is required to determine the relationship between pain characteristics and PS to determine the role that central amplification has on patient clinical profiles.
0.312c* 0.336c*
PPT
0.177c 0.290c*
Bold represent significant findings based on alpha of 0.05. Lx ¼ lumbar spine. *p < 0.05; **p < 0.01. a Measure of association is Pearson correlation coefficient. b Measure of association is Spearman correlation coefficient. c Measure of association is Point-biserial correlation coefficient. d Measure of association is Phi correlation coefficient.
This study was only powered to detect large effect sizes, and consequently may have failed to detect smaller but still clinically meaningful differences between groups. As a consequence of the small sample size, the confidence intervals for the elevated odds of cold hypersensitivity in the NMP group were very wide, limiting
Please cite this article in press as: O’Sullivan P, et al., Sensory characteristics of chronic non-specific low back pain: A subgroup investigation, Manual Therapy (2014), http://dx.doi.org/10.1016/j.math.2014.03.006
P. O’Sullivan et al. / Manual Therapy xxx (2014) 1e8
7
Table 5 Adjusted and unadjusted parameter estimates for group membership from univariable and multivariable binary logistic regression (CPT: 15 C, >15 C) and general linear (ln(PPT)) models (multivariable models adjusted for gender, DASS total and PSQI). Cold pain threshold
Wrist
Unadjusted
Non-mechanical Control Mechanical Non-mechanical Control Mechanical Non-mechanical Control Mechanical
Lx
Heel
Adjusted
Odds ratioa (95% CI)
p-Value
Odds ratio (95% CI)
p-Value
17.3 (3.3, 91.7) 1.2 (0.3, 5.3) REF 6.0 (1.3, 28.5) 1.0 (0.3, 3.8) REF 2.5 (0.6, 10.1) 0.4 (0.1, 1.6) REF
0.001 0.849
18.4 (2.5, 133.1) 1.3 (0.2, 7.0) REF 5.9 (0.9, 38.4) 1.4 (0.3, 6.4) REF 6.3 (0.9, 41.5) 0.3 (0.1, 1.4) REF
0.004 0.759
0.024 0.985 0.201 0.198
0.064 0.637 0.058 0.134
Pressure pain threshold
b (95% CI)b
p-Value
b (95% CI)
p-Value
Wrist
0.07 (0.29, 0.15) 0.08 (0.14, 0.30) REF 0.58 (0.97, -0.19) 0.12 (0.27, 0.51) REF 0.19 (0.43, 0.06) 0.01 (0.26, 0.23) REF
0.551 0.489
0.11 (0.37, 0.15) 0.11 (0.13, 0.35) REF 0.37 (0.83, 0.09) 0.04 (0.38, 0.47) REF 0.22 (0.52, 0.08) 0.01 (0.27, 0.28) REF
0.407 0.347
Non-mechanical Control Mechanical Non-mechanical Control Mechanical Non-mechanical Control Mechanical
Lx
Heel
0.004 0.547 0.133 0.911
0.117 0.838 0.142 0.954
Bold represent significant findings based on alpha of 0.05. a The ratio of the odds for cold pain threshold > 15 C for the test group (non-mechanical or control) to the reference group (mechanical pain group). b Coefficient represents difference in the natural log of pressure pain threshold between test groups (non-mechanical or control) and the reference group (mechanical pain group, positive value indicates higher value in test group).
precise estimation of this association in the population under study. Furthermore, for PPT, testing at a generic site at the lumbar spine may not detect local hyperalgesia. Previous authors have successfully tested PPT in patients with CNSLBP at the site of most severe pain and found it to be predictive with pain, independent of potential confounders (Neziri et al., 2012). Pain medication use was only reported in CNSLBP participants, which precluded use of this variable in the multivariable models presented. However, group differences in medication use were not large (Table 6) and current pain medication use was not associated with CPT or PPT. Other variables only assessed in CNSLBP participants and associated with pain group membership, such as pain intensity, number of pain areas, RMDQ and SBST, were not considered as confounders of the group membership/pain threshold association in this study as they represented part of the common clinical profile of these groups and thus consequences of differential sensory processing. The inter-therapist reliability of the ability of Physiotherapists to differentiate NP from NMP requires further investigation and larger studies are required to verify these results. 5. Conclusion This study provides preliminary evidence that two patient groups with CNSLBP identified clinically, can be distinguished based on their PS profile. When used in conjunction with sound Table 6 Frequency of non-cold descriptorsa cited during the cold pain testing. Controls (n ¼ 19) N (% of group) CPT wrist 3 (15.8) CPT L5/S1 7 (36.8) CPT heel 3 3 (15.8)
Mechanical CNSLBP (n ¼ 17)
Non-mechanical CNSLBP (n ¼ 19)
p-Valueb
6 (35.3) 12 (70.6) 9 (52.9)
12 (63.2) 18 (94.7) 11 (57.9)
0.010 0.001 0.017
a Non-cold descriptors used were ‘burning, ice, sharp, sting, gnawing and freezing’. Any other descriptions were not included as non-cold descriptors. These were ‘pressure, nice, cold, tingling, pleasant and numb’. b Chi-squared test.
clinical reasoning, these profiles may help clinicians more accurately identify mechanisms that underlie CNSLBP and better target interventions. While these pain profiles have yet to be further validated, they provide a framework for future research. Author contributions All authors discussed the results and contributed to the manuscript. References Attal N, Perrot S, Fermanian J, Bouhassira D. The neuropathic components of chronic low back pain: a prospective multicenter study using the DN4 questionnaire. J Pain 2011;12:1080e7. Blumenstiel KMD, Gerhardt AMA, Rolke RMD, Bieber CMD, Tesarz JMD, Friederich H-CMD, et al. Quantitative sensory testing profiles in chronic back pain are distinct from those in fibromyalgia. Clin J Pain 2011;27:682e90. Buysse D, Reynolds C, Monk T, Berman S, Kupfer D. The Pittsburgh sleep quality index: a new instrument for psychiatric practice and research. Psychiatry Res 1989;28:193e213. Campbell C, Edwards R. Mindebody interactions in pain: the neurophysiology of anxious and catastrophic pain-related thoughts. Transl Res 2009;153:97e101. Carli G, Suman AL, Biasi G, Marcolongo R. Reactivity to superficial and deep stimuli in patients with chronic musculoskeletal pain. Pain 2002;100:259e69. Chien A, Sterling M. Sensory hypoaesthesia is a feature of chronic whiplash but not chronic idiopathic neck pain. Man Ther 2010;15:48e53. Dankaerts W, O’Sullivan P, Burnett A, Straker L. Differences in sitting postures are associated with nonspecific chronic low back pain disorders when patients are subclassified. Spine 2006;31:698e704. Dankaerts W, O’Sullivan P, Burnett A, Straker L, Davey P, Gupta R. Discriminating healthy controls and two clinical subgroups of nonspecific chronic low back pain patients using trunk muscle activation and lumbosacral kinematics of postures and movements. Spine 2009;34:1610e8. Deyo RA, Mirza SK, Turner JA, Martin BI. Overtreating chronic back pain: time to back off? J Am Board Fam Med 2009;22:62e8. Dunn W. The impact of sensory processing abilities on the daily lives of young children and their families: a conceptual model. Infants Young Child 1997;9: 23e35. Freynhagen R, Baron R, Gockel U, Tolle T. painDETECT: a new screening questionnaire to identify neuropathic components in patients with back pain. Curr Med Res Opin 2006;22:1911e20. Giesecke T, Gracely RH, Grant MAB, Nachemson AL, Petzke F, Williams DA, et al. Evidence of augmented central pain processing in idiopathic chronic low back pain. Arthritis Rheum 2004;50:613e23.
Please cite this article in press as: O’Sullivan P, et al., Sensory characteristics of chronic non-specific low back pain: A subgroup investigation, Manual Therapy (2014), http://dx.doi.org/10.1016/j.math.2014.03.006
8
P. O’Sullivan et al. / Manual Therapy xxx (2014) 1e8
Heffner K, France C, Trost Z, Ng H, Pigeon W. Chronic low back pain, sleep disturbance, and interleukin-6. Clin J Pain 2011;27:35e41. Hill JC, Dunn KM, Lewis M, Mullis R, Main CJ, Foster NE, et al. A primary care back pain screening tool: identifying patient subgroups for initial treatment. Arthritis Rheum 2008;59:632e41. Hubsher M, Moloney N, Leaver A, Rebbeck T, McAuley J, Refshauge K. Relationship between quantitative sensory testing and pain or disability in people with spinal pain e a systematic review and meta-analysis. Pain 2013;154:1497e504. Huskisson EC. Measurement of pain. Lancet 1974;2:1127e31. Jones D. Testeretest reliability of pressure pain threshold measurements of the upper limb and torso in young healthy women. J Pain 2007;8:650e6. Karayannis NV, Jull GA, Hodges PW. Physiotherapy movement based classification approaches to low back pain: comparison of subgroups through review and developer/expert survey. BMC Musculoskelet Disord 2012;13:24. Kasch H, Qerama E, Bach FW, Jensen TS. Reduced cold pressor pain tolerance in nonrecovered whiplash patients: a 1-year prospective study. Eur J Pain 2005;9: 561e9. Leboeuf-Yde C, Nielsen J, Kyvik K, Fejer R, Hartvigsen J. Pain in the lumbar, thoracic and cervical regions: do age and gender matter? A population-based study of 34,902 Danish twins 20e71 years of age. BMC Musculoskelet Disord 2009;10. Lewis C, Khan A, Souvlis T, Sterling M. Sensory characteristics of tender points in the lower back. Man Ther 2010;15:536e41. Lovibond S, Lovibond P. Manual for the depression anxiety stress scales; 1995. Maxwell S, Sterling M. An investigation of the use of a numeric pain rating scale with ice application to the neck to determine cold hyperalgesia. Man Ther 2013;18:172e4. Meeus M, Nijs J. Central sensitization: a biopsychosocial explanation for chronic widespread pain in patients with fibromyalgia and chronic fatigue syndrome. Clin Rheumatol 2007;26:465e73. Moloney NA, Hall TM, Doody CM. Reliability of thermal quantitative sensory testing: a systematic review. J Rehabil Res Dev 2012;49:191e207. Mosek A, Yarnitsky D, Korczyn AD, Niv D. The assessment of radiating low back pain by thermal sensory testing. Eur J Pain 2001;5:347e51. Neziri A, Curatolo M, Limacher A, Nüesch E, Radanov B, Andersen O, et al. Ranking of parameters of pain hypersensitivity according to their discriminative ability in chronic low back pain. Pain 2012;153:2083e91. Nijs J, Van Houdenhove B, Oostendorp RAB. Recognition of central sensitization in patients with musculoskeletal pain: application of pain neurophysiology in manual therapy practice. Man Ther 2010;15:135e41. O’Sullivan P. Diagnosis and classification of chronic low back pain disorders: maladaptive movement and motor control impairments as underlying mechanism. Man Ther 2005;10:242e55. O’Sullivan P, Straker L, Smith A, Perry M, Kendall G. Carer experience of back pain is associated with adolescent back pain experience even when controlling for other carer and family factors. Clin J Pain 2008;24:226e31. O’Sullivan P. It’s time for change in the management of non-specific chronic low back pain. Br J Sports Med 2012a;46:224e7.
O’Sullivan PB. A classification-based cognitive functional approach for the management of back pain. J Orthop Sports Phys Ther 2012b;42:A17e21. O’Neill S, Kjær P, Graven-Nielsen T, Manniche C, Arendt-Nielsen L. Low pressure pain thresholds are associated with, but does not predispose for, low back pain. Eur Spine J 2011;20:2120e5. Roland M, Fairbank J. The RolandeMorris disability questionnaire and the Oswestry disability questionnaire. Spine 2000;25:3115e24. Roland M, Morris R. A study of the natural history of back pain. Spine 1983;8:141e4. Rolke R, Baron R, Maier C, Tolle TR, Treede RD, Beyer A, et al. Quantitative sensory testing in the German research network on neuropathic pain (DFNS): standardized protocol and reference values. Pain 2006a;123:231e43. Rolke R, Baron R, Maier C, Tölle TR, Treede RD, Beyer A, et al. Quantitative sensory testing in the German research network on neuropathic pain (DFNS): standardized protocol and reference values. Pain 2006b;123:231e43. Roussel NAPMPT, Nijs JPMPT, Meeus MPPT, Mylius VPMD, Fayt CPMD, Oostendorp RPMPTPT. Central sensitization and altered central pain processing in chronic low back pain: fact or myth? Clin J Pain 2013;29:625e38. Scott D, Jull G, Sterling M. Widespread sensory hypersensitivity is a feature of chronic whiplash-associated disorder but not chronic idiopathic neck pain. Clin J Pain 2005;21:175e81. Slater H, Arendtnielsen L, Wright A, Gravennielsen T. Sensory and motor effects of experimental muscle pain in patients with lateral epicondylalgia and controls with delayed onset muscle soreness. Pain 2005;114:118e30. Smart K, Blake C, Staines A, Doody C. Clinical indicators of ‘nociceptive’, ‘peripheral neuropathic’ and ‘central’ mechanisms of musculoskeletal pain. A Delphi survey of expert clinicians. Man Ther 2010;15:80e7. Spitzer WO. Scientific approach to the assessment and management of activityrelated spinal disorders: a monograph for clinicians. Report of the Quebec task force on spinal disorders. Spine 1987;12:1e59. Vibe Fersum K, O’Sullivan PB, Kvåle A, Skouen JS. Inter-examiner reliability of a classification system for patients with non-specific low back pain. Man Ther 2009;14:555e61. Vibe Fersum K, O’Sullivan P, Skouen JS, Smith A, Kvåle A. Efficacy of classification based ‘cognitive functional therapy’ in patients with Non Specific Chronic Low Back Pain – a randomized controlled trial. Eur Pain J 2012;17(6):916e28. Wasner GL, Brock JA. Determinants of thermal pain thresholds in normal subjects. Clin Neurophysiol 2008;119:2389e95. Wolfe F, Clauw D, Fitzcharles M, Goldenberg D, Katz R, Mease P, et al. The American College of Rheumatology preliminary diagnostic criteria for fibromyalgia and measurement of symptom severity. Arthritis Care Res 2010;62:600e10. Woolf C, Mannion R. Neuropathic pain: aetiology, symptoms, mechanisms, and management. Lancet 1999;353:1959e64. Woolf CJ. Central sensitization: implications for the diagnosis and treatment of pain. Pain 2011;152:S2e15. Wright A, Thurnwald P, O’Callaghan J, Smith J, Vicenzino B. Hyperalgesia in tennis elbow patients. J Musculoskelet Pain 1994;2:83e97. Zwart J-A, Trond S. Repeatability of dermatomal warm and cold sensory thresholds in patients with sciatica. Eur Spine J 2002;11:441e6.
Please cite this article in press as: O’Sullivan P, et al., Sensory characteristics of chronic non-specific low back pain: A subgroup investigation, Manual Therapy (2014), http://dx.doi.org/10.1016/j.math.2014.03.006
![[Childhood abuse experiences and chronic low back pain. Direct and mediated effects of childhood abuse in different pain dimensions of nonspecific chronic low back pain].](/assets/img/hold.png)
