Further exploring the relationship between pressure pain thresholds and function in knee osteoarthritis

BACKGROUND

Studies in Knee Osteoarthritis (KOA) have shown lowered Pressure Pain Threshold (PPT) values compared to healthy controls potentially signifying mechanical hypersensitivity, although the relevance of these findings to knee function remains unclear.

OBJECTIVE

This study further explores the relationship between PPT measures and knee function (self-reported, physical) in individuals undergoing total knee arthroplasty for advanced KOA.

DESIGN

Cross-sectional observational study.

METHODS

PPT's were recorded both local to the affected knee and at a remote site (deltoid) in 79 individuals with advanced KOA. Participants also completed self-report (Knee Society Score - functional sub-score) and physical (6-min walk test distance)) measures of knee function, as well as measures of pain-related psychological distress. Hierarchical linear regression models evaluated the relationship between the measures of function (self-report and physical measures modelled separately), PPT measures (local and remote), while accounting for demographic and psychological distress measures.

RESULTS

Higher knee PPT scores were independently associated with higher self-reported knee function (β 0.33, p < 0.02) and higher 6-min walk test distance (β 0.41, p < 0.01), although pain self-efficacy (β 0.33, p < 0.01) was also a significant variable in both models. Nearly identical findings were evident for PPT's measured at the deltoid. Overall PPT's could only explain a modest portion of variance (adjusted R² = 0.15 to 0.17) in the functional measures.

CONCLUSIONS

PPT measures may be limited in their capacity to distinguish the impact of peripheral and central pain mechanisms on knee function in individuals undergoing total knee arthroplasty for advanced KOA.

Magnetic Resonance Spectroscopy Assessment of Brain Metabolite Concentrations in Individuals With Chronic Whiplash-associated Disorder: A Cross-sectional Study

OBJECTIVES

Pathophysiologic mechanisms underpinning ongoing pain in whiplash-associated disorder (WAD) are not well understood, however, alterations in brain morphology and function have been observed in this population and in other chronic pain conditions. This study investigated metabolite profiles of brain regions in people with chronic WAD compared with controls.

MATERIALS AND METHODS

Thirty-eight individuals with chronic WAD (mean [SD] age, 39.5 [11.3] years, 23 female individuals) and 16 pain-free controls (38.9 [12.7] years, 11 female individuals) underwent multivoxel brain magnetic resonance spectroscopy. At the anterior cingulate cortex (ACC), primary motor cortex (1MC), and somatosensory cortex (SSC), ratios of metabolite concentrations were calculated for N-acetylaspartate (NAA), creatine (Cr), choline (Cho), myo-inositol (Ins), and glutamate/glutamine (Glx). Chronic WAD group participants completed clinical questionnaires and cold and pressure pain threshold assessment. Data were analyzed with hypothesis testing and Spearman correlations (P≥0.05), with Benjamini-Hochberg corrections (5% false discovery rate).

RESULTS

No group differences were observed for NAA:Cr, NAA:Cho, Cr:Cho, Glx:NAA, Glx:Cr, Glx:Cho, Ins:NAA, Ins:Cr, Ins:Cho or Ins:Glx for left or right ACC, 1MC, or SSC following correction for multiple comparisons. No significant correlations were observed between metabolite ratios and any clinical variable.

DISCUSSION

These results suggest that ongoing pain and disability in this population may not be underpinned by metabolite aberrations in the brain regions examined. Further research is required to progress our understanding of cortical contributions to neurophysiologic mechanisms in chronic WAD.

Spinal cord injury is not a feature of chronic whiplash-associated disorder: a magnetic resonance spectroscopy study

PURPOSE

Injury to the cervical spinal cord has been suggested as a mechanism that may underpin chronic whiplash-associated disorder (WAD). This study aimed to assess metabolite concentrations indicative of neuronal injury or pathology in the cervical cord in people with chronic WAD.

METHODS

Forty-one people with chronic WAD (mean [SD] age 39.6 [11.0] years, 25 females) and 14 healthy controls (39.2 [12.6] years, 9 females) underwent cervical spinal cord magnetic resonance spectroscopy to measure the metabolites N-acetylaspartate (NAA), creatine (Cr) and choline (Cho). Participants with WAD completed clinical questionnaires on pain intensity (Visual Analogue Scale), disability (Neck Disability Index) and psychological factors (Pain Catastrophising Scale, Post-traumatic Diagnostic Scale), and underwent cervical range of motion assessment and pain threshold testing to cold and pressure stimuli. Data were analysed using hypothesis testing and Spearman correlations (p < 0.05).

RESULTS

There were no differences between the WAD and control groups for NAA/Cr (median [IQR] WAD 1.73 [1.38, 1.97], controls 2.09 [1.28, 2.89], p = 0.37), NAA/Cho (WAD 1.50 [1.18, 2.01], controls 1.57 [1.26, 1.93], p = 0.91) or Cr/Cho (WAD 0.84 [0.64, 1.17], controls 0.76 [0.60, 0.91], p = 0.33). There were no significant correlations between NAA/Cr, NAA/Cho or Cr/Cho and any clinical variable (p ≥ 0.06).

CONCLUSIONS

Findings are consistent with major metabolic changes not being present in chronic WAD.

Evidence of generalised mechanical hyperalgesia in patients with advanced knee osteoarthritis undergoing total knee arthroplasty

BACKGROUND AND OBJECTIVE

Persistent pain is reported in up to 34% of patients following total knee arthroplasty (TKA) for management of knee osteoarthritis (KOA). Persistent pain in this group is thought to be at least partly reflective of pain sensory hypersensitivity. The objective of this study was to evaluate sensory hypersensitivity, using mechanical and thermal quantitative sensory testing, in patients about to undergo TKA.

DESIGN AND METHODS

Pressure pain thresholds (PPT) and cold pain thresholds (CPT) were recorded from 30 participants prior to their TKA, and compared with recordings taken from 30 healthy control participants of similar age and gender. Thresholds were recorded locally and remotely (other knee, deltoid) to the operative knee. Group comparisons (KOA, control, groups) were made using a general linear mixed models approach with age, gender, and body mass index (BMI) included as covariates. Pairwise comparisons were conducted with Bonferonni correction for multiple comparisons.

RESULTS

Significantly lower PPTs were at all measured sites in the KOA group compared to the control group (P<0.001 at all sites, except the deltoid P=0.004). Males demonstrated higher pain threshold compared to females, averaged over all sites, P=0.02. There were no observed between-group differences in CPT (P=0.122).

CONCLUSIONS

This study suggested that some individuals about to undergo TKA for their advanced KOA demonstrated widespread mechanical sensory hypersensitivity. These findings have potentially important clinical implications regarding perioperative and longer-term pain management in these patients.

Intramuscular fat is present in cervical multifidus but not soleus in patients with chronic whiplash associated disorders

The presence of intramuscular fat (IMF) in the cervical spine muscles of patients with whiplash associated disorders (WAD) has been consistently found. The mechanisms underlying IMF are not clear but preliminary evidence implicates a relationship with stress system responses. We hypothesised that if systemic stress system responses do play a role then IMF would be present in muscles remote to the cervical spine. We aimed to investigate if IMF are present in muscle tissue remote (soleus) to the cervical spine in people with chronic WAD. A secondary aim was to investigate associations between IMF and posttraumatic stress symptom levels. Forty-three people with chronic WAD (25 female) and 16 asymptomatic control participants (11 female) participated. Measures of pain, disability and posttraumatic stress symptoms were collected from the WAD participants. Both groups underwent MRI measures of IMF in cervical multifidus and the right soleus muscle. There was significantly greater IMF in cervical multifidus in patients with WAD and moderate/severe disability compared to controls (p = 0.009). There was no difference in multifidus IMF between the mild and moderate/severe disability WAD groups (p = 0.64), or the control and mild WAD groups (p = 0.21). IMF in the right soleus was not different between the groups (p = 0.47). In the WAD group, we found no correlation between PDS symptoms and cervical multifidus IMF or between PDS symptoms and soleus IMF. Global differences in IMF are not a feature of chronic WAD, with differences in IMF limited to the cervical spine musculature. While the mechanisms for the development of IMF in the cervical spine following whiplash injury remain unclear, our data indicate that local factors more likely contribute to these differences.

The influence of isometric exercise on endogenous pain modulation: comparing exercise-induced hypoalgesia and offset analgesia in young, active adults

Background and aims

Impairment of endogenous analgesia has been associated with the development, maintenance and persistence of pain. Endogenous analgesia can be evaluated using exercise-induced hypoalgesia (EIH) and offset analgesia (OffA) paradigms, which measure temporal filtering of sensory information. It is not clear if these paradigms are underpinned by common mechanisms, as EIH and OffA have not previously been directly compared. A further understanding of the processes responsible for these clinically relevant phenomena may have future diagnostic and therapeutic utility in management of individuals with persistent pain conditions. The primary aim of this study was to investigate if there is a correlation between the magnitudes of EIH and OffA. The secondary aim of the study was to examine whether exercise influences OffA.

Methods

Thirty-six healthy, pain-free participants were recruited. EIH was evaluated using pressure pain thresholds (PPT) and pain ratings to suprathreshold pressure stimuli over tibialis anterior and the cervical spine. OffA evaluation utilised a three-step protocol, whereby individualised heat pain thermal stimuli [Numerical Rating Scale (NRS)=50/100] were applied (T1), before increasing 1 °C (T2), followed by 1 °C reduction (T3). The magnitude of OffA was calculated as the percentage reduction in the NRS from T2 to T3. PPT/suprathreshold pain ratings and OffA measures were recorded, before and after 5 min of isometric quadriceps exercise performed at 20–25% maximum voluntary contraction (MVC); and following a 15 min rest period. Data were analysed using repeated measures (RM) ANCOVA and correlational analyses.

Results

There was no correlation between EIH measures (PPTs or pain ratings to suprathreshold pressure stimuli over tibialis anterior or the cervical spine) and OffA (p>0.11 for all). OffA was induced and not modulated by exercise (p=0.28).

Conclusions

Five minutes of 20–25% MVC lower limb isometric exercise provided non-pharmacological pain modulation in young, active adults. Magnitude of EIH was not correlated with that of OffA, and exercise did not influence magnitude of OffA.

Implications

These results suggest that in young, pain-free individuals, separate testing of these two paradigms is required to comprehensively evaluate efficacy of endogenous analgesia. If these results are replicated in patient populations, alternative or complementary methods to exercise interventions may be required to modulate impaired OffA.

Multivariate pattern analysis utilizing structural or functional MRI-In individuals with musculoskeletal pain and healthy controls: A systematic review

OBJECTIVE

The purpose of this systematic review is to systematically review the evidence relating to findings generated by multivariate pattern analysis (MVPA) following structural or functional magnetic resonance imaging (fMRI) to determine if this analysis is able to: a) Discriminate between individuals with musculoskeletal pain and healthy controls, b) Predict pain perception in healthy individuals stimulated with a noxious stimulus compared to those stimulated with a non-noxious stimulus.

METHODS

MEDLINE, CINAHL, Embase, PEDro, Google Scholar, Cochrane library and Web of Science were systematically screened for relevant literature using different combinations of keywords regarding structural and functional MRI analysed with MVPA, both in individuals with musculoskeletal pain and healthy controls. Reference lists of included articles were hand-searched for additional literature. Eligible articles were assessed on risk of bias and reviewed by two independent researchers.

RESULTS

The search query returned 18 articles meeting the inclusion criteria. Methodological quality varied from poor to good. Seven studies investigated the ability of machine-learning algorithms to differentiate patient groups from healthy control participants. Overall, the review demonstrated that MVPA can discriminate between individuals with MSK pain and healthy controls with an overall accuracy ranging from 53% to 94%. Twelve studies utilized healthy control participants (using them as their own controls), during experimental pain paradigms aimed to investigate the ability of machine-learning to differentiate individuals stimulated with noxious stimuli from those stimulated with non-noxious stimuli, with 'pain' detection rates ranging from 60% to 94%. However, significant heterogeneity in patient conditions, study methodology and brain imaging techniques resulted in various findings that make study comparisons and formal conclusions challenging.

CONCLUSION

There is preliminary and emerging evidence that MVPA analyses of structural or functional MRI are able to discriminate between patients and healthy controls, and also discriminate between noxious and non-noxious stimulation. No prospective studies were found in this review to allow determination of the prognostic or diagnostic capabilities or treatment responsiveness of these analyses. Future studies would also benefit from combining various behavioural, genotype and phenotype data into analyses to assist with development of sensitive and specific signatures that could guide future individualized patient treatment options and evaluate how treatments exert their effects.

Evaluating the neck joint position sense error with a standard computer and a webcam

Joint Position Sense Error (JPSE) is a measure of cervical spine proprioception, and a simple method for measuring the JPSE could help in monitoring and evaluating the outcomes of rehabilitation of people with neck pain. In this study we demonstrate preliminary results of a method for measuring JPSE that does not require the participant to wear any equipment. Based on free publicly available head tracking software, compatible with any webcam, we developed a webpage which instructs the participant in performing a self-administered version of the test. The aim of this proof-of-concept study was to demonstrate the viability of this system. We compared our absolute error values (3.68 ± 1.2° after extension, 3.46 ± 1.66° after flexion, 3.89 ± 2.34° after rotation to the left and 4.02 ± 1.82°after rotation to the right) to values from literature, finding that our results do not differ from those of 6 out of 11 studies (which used more complex and expensive setups). The results indicate that our system allows assessment of the JPSE with a standard computer. Being based on a website, the system has potential for telemedicine use. Further research is required to validate the system before it can be recommended for use in clinical practice.

Morphological changes in the cervical muscles of women with chronic whiplash can be modified with exercise-A pilot study

INTRODUCTION

In this preliminary study we determined whether MRI markers of cervical muscle degeneration [elevated muscle fatty infiltration (MFI), cross-sectional area (CSA), and reduced relative muscle CSA (rmCSA)] could be modified with exercise in patients with chronic whiplash.

METHODS

Five women with chronic whiplash undertook 10 weeks of neck exercise. MRI measures of the cervical multifidus (posterior) and longus capitus/colli (anterior) muscles, neck muscle strength, and self-reported neck disability were recorded at baseline and at completion of the exercise program.

RESULTS

Overall significant increases in CSA and rmCSA were observed for both muscles, but significant reductions in MFI were only evident in the cervical multifidus muscle. These changes coincided with increased muscle strength and reduced neck disability.

CONCLUSIONS

MRI markers of muscle morphology in individuals with chronic whiplash appear to be modifiable with exercise.

Physiotherapists' Beliefs About Whiplash-associated Disorder: A Comparison Between Singapore and Queensland, Australia

BACKGROUND AND PURPOSE

Healthcare providers' beliefs may play a role in the outcome of whiplash-associated disorders (WAD), a condition which is proposed to be culturally dependent. Clinical practice guidelines recommend an active approach for the management of WAD, which is often delivered by physiotherapists. However, there is no data on physiotherapists' whiplash beliefs. Our primary objective was to determine physiotherapists' beliefs from Queensland (Australia) and Singapore, two cultures with differing prevalence of chronic musculoskeletal pain and chronic WAD.

METHODS

A pen and paper survey of musculoskeletal physiotherapists practicing in Queensland and Singapore was conducted. Participants completed questionnaires consisting of patient vignettes and statements inquiring knowledge and attitudes towards WAD. Chi-square tests of significance were used to compare the responses of physiotherapists from both samples.

RESULTS

Ninety-one (response rate 45%) Queensland-based and 94 (response rate 98%) Singapore-based physiotherapists participated in the study. The beliefs in the management strategies for the patient vignettes were generally consistent with practice guidelines. A higher proportion of Queensland-based physiotherapists expected permanent disabilities for the patient vignette depicting chronic WAD (Queensland: 55% Singapore: 28% Pearson chi-sq 18.76, p < 0.005).Up to 99% of the physiotherapists from both samples believed in encouragement of physical activity, the effectiveness of exercise and multimodal physiotherapy for WAD. Significantly higher proportions of Singapore-based physiotherapists believed in ordering radiographs for acute WAD (Pearson chi-sq 41.98, p < 0.001) and also believed in a psychogenic origin of chronic WAD (Pearson chi-sq 22.57, p  0.001).

CONCLUSION

The majority of beliefs between physiotherapists in Queensland and Singapore were similar but there were specific differences. Physiotherapists' whiplash beliefs in Queensland and Singapore did not clearly reflect the difference in prevalence of chronic musculoskeletal pain or chronic WAD in Queensland and Singapore.

Laypersons' expectations of recovery and beliefs about whiplash injury: a cross-cultural comparison between Australians and Singaporeans

BACKGROUND

Beliefs and expectations are thought to influence outcome following whiplash injury. Studies have proposed a link between rates of chronic whiplash and laypersons' expectations about outcome following a motor vehicle accident. The prevalence of chronic whiplash is relatively high in Australia and apparently low in Singapore. This study's objectives were to compare laypersons' beliefs and expectations of recovery of whiplash injury in Brisbane and Singapore and to assess the effect of demographic factors on whiplash beliefs.

METHODS

A cross-sectional study using online surveys was conducted on adult Internet users in Brisbane (Australia) and Singapore. The 14-item whiplash beliefs questionnaire (WBQ) was used to evaluate whiplash beliefs. Two additional items assessed expectations of recovery. Individual items of WBQ, WBQ score and expectations of recovery were analysed. Stratified analysis was performed to adjust for sampling bias due to quota sampling.

RESULTS

A total of 402 participants from Singapore and 411 participants from Brisbane, Australia, completed the survey. While participants from Singapore demonstrated slightly more negative whiplash beliefs than participants from Brisbane [t(811)  = -5.72; p < 0.0001], participants from both samples were similar in their expectations of quick recovery and return to normal activities following whiplash injury. Only gender had a significant effect on whiplash beliefs [estimated marginal means of WBQ score for men = 21.5; standard error (SE) = 0.20; women = 22.5; SE = 0.20; F(1,810)  = 11.2; p = 0.001].

CONCLUSIONS

Laypersons' expectations of recovery and beliefs about whiplash injury in Brisbane and Singapore were generally similar and mostly positive. Our results demonstrate that cultural differences reflected by laypersons' beliefs may not reflect the differences in prevalence of chronic whiplash between countries.

The temporal development of fatty infiltrates in the neck muscles following whiplash injury: an association with pain and posttraumatic stress

BACKGROUND

Radiological findings associated with poor recovery following whiplash injury remain elusive. Muscle fatty infiltrates (MFI) in the cervical extensors on magnetic resonance imaging (MRI) in patients with chronic pain have been observed. Their association with specific aspects of pain and psychological factors have yet to be explored longitudinally.

MATERIALS AND FINDINGS

44 subjects with whiplash injury were enrolled at 4 weeks post-injury and classified at 6 months using scores on the Neck Disability Index as recovered, mild and moderate/severe. A measure for MFI and patient self-report of pain, loss of cervical range of movement and posttraumatic stress disorder (PTSD) were collected at 4 weeks, 3 months and 6 months post-injury. The effects of time and group and the interaction of time by group on MFI were determined. We assessed the mediating effect of posttraumatic stress and cervical range of movement on the longitudinal relationship between initial pain intensity and MFI. There was no difference in MFI across all groups at enrollment. MFI values increased in the moderate/severe group and were significantly higher in comparison to the recovered and mild groups at 3 and 6 months. No differences in MFI values were found between the mild and recovered groups. Initial severity of PTSD symptoms mediated the relationship between pain intensity and MFI at 6 months. Initial ROM loss did not.

CONCLUSIONS

MFI in the cervical extensors occur soon following whiplash injury and suggest the possibility for the occurrence of a more severe injury with subsequent PTSD in patients with persistent symptoms.

Cervical lateral glide increases nociceptive flexion reflex threshold but not pressure or thermal pain thresholds in chronic whiplash associated disorders: A pilot randomised controlled trial

Sensory hypersensitivity indicative of augmented central pain processing is a feature of chronic whiplash associated disorders (WAD). This study investigated the immediate effects of a cervical spine manual therapy (SMT) technique on measures of central hyperexcitability. In a randomised, single blind, clinical trial, 39 participants with chronic WAD were randomly assigned to a cervical SMT (lateral glide) or manual contact intervention. The Neck Disability Index (NDI) and GHQ-28 were administered at baseline. Pressure pain thresholds (PPTs), thermal pain thresholds (TPTs) and Nociceptive Flexion Reflex (NFR) responses (threshold and VAS of pain) were measured pre and post intervention. There was a significantly greater increase in NFR threshold following SMT compared to the manual contact intervention (p = 0.04). PPTs at the cervical spine increased following both SMT (mean +/- SE: 24.1 +/- 7.3%) and manual contact (21 +/- 8.4%) with no difference between interventions. There was no difference between interventions for pain ratings with the NFR test, PPTs at the Median Nerve or Tibialis Anterior, heat or cold TPT. SMT may be effective in reducing spinal hyperexcitability in chronic WAD.

A neuropathic pain component is common in acute whiplash and associated with a more complex clinical presentation

Whiplash is a heterogeneous condition with some individuals showing features suggestive of neuropathic pain. This study investigated the presence of a neuropathic pain component in acute whiplash using the Self-reported Leeds Assessment of Neuropathic Signs and Symptoms' scale (S-LANSS) and evaluated relationships among S-LANSS responses, pain/disability, sensory characteristics (mechanical, thermal pain thresholds, and Brachial plexus provocation test (BPPT) responses) and psychological distress (General Health Questionnaire-28 (GHQ-28)). Participants were 85 people with acute whiplash (<4 weeks) (54 females, age 36.27+/-12.69 years). Thirty-four percent demonstrated a predominantly neuropathic pain component (S-LANSS>or=12). This group showed higher pain/disability, cold hyperalgesia, cervical mechanical hyperalgesia, and less elbow extension with the BPPT (p<0.03) when compared to the group with non-neuropathic pain (S-LANSS<or=12). Pressure pain thresholds (PPTs) at distant sites and psychological distress (GHQ-28) were not different between the groups (p>0.09). None of the S-LANSS items could discriminate those with cold hyperalgesia (p=0.06). A predominantly neuropathic pain component is related to a complex presentation of higher pain/disability and sensory hypersensitivity. The S-LANSS may be a useful tool and the BPPT a useful clinical test in the early assessment of whiplash.

Targetting AFLP-DNA markers to specific traits and chromosome regions

The amplified fragment length polymorphism (AFLP) technique is widely used in mapping of wheat as high polymorphism rates are obtained and the procedure is relatively simple. In this study the AFLP markers were targetted to wheat chromosome regions of interest, especially those in which random mapping approaches located relatively few markers. Results showed that the combination of bulk segregant analysis and AFLP markers could target new markers to regions of interest in wheat, and as a result, additional markers were identified for the dough mixing time and noodle colour traits. The new markers for noodle colour were closer to this trait than the markers previously identified by random procedures. As a result, their association with the trait was more significant, an aspect that is important for selection efficiency. In order to improve genome coverage, it was found that regions of chromosomes containing telomere sequences could be targetted using AFLPs combined with a telomere sequence anchor primer.