Aims. The aim of this study was to describe the prevalence and patterns of neuropathic pain over one year in a cohort of patients with chronic post-surgical pain at three months following total knee arthroplasty (TKA). Methods. Between 2016 and 2019, 363 patients with troublesome pain, defined as a score of ≤ 14 on the Oxford Knee Score pain subscale, three months after TKA from eight UK NHS hospitals, were recruited into the Support and Treatment After Replacement (STAR) clinical trial. Self-reported neuropathic pain and postoperative pain was assessed at three, nine, and 15 months after surgery using the painDETECT and Douleur Neuropathique 4 (DN4) questionnaires collected by postal survey. Results. Symptoms of neuropathic pain were common among patients reporting chronic pain at three months post-TKA, with half reporting neuropathic pain on painDETECT (191/363; 53%) and 74% (267/359) on DN4. Of those with neuropathic pain at three months, half continued to have symptoms over the next 12 months (148/262; 56%), one-quarter had improved (67/262; 26%), and for one-tenth their neuropathic symptoms fluctuated over time (24/262; 9%). However, a subgroup of participants reported new, late onset neuropathic symptoms (23/262; 9%). Prevalence of neuropathic symptoms was similar between the screening tools when the lower cut-off painDETECT score (≥ 13) was applied. Overall, mean neuropathic pain scores improved between three and 15 months after TKA. Conclusion. Neuropathic pain is common in patients with chronic pain at three months after TKA. Although neuropathic symptoms improved over time, up to half continued to report painful neuropathic symptoms at 15 months after TKA. Postoperative care should include screening, assessment, and treatment of neuropathic pain in patients with early chronic postoperative pain after TKA. Cite this article: Bone Joint J 2024;106-B(6):582–588

Abstract. Introduction. Total knee replacement (TKR) is a successful operation for many patients, however 15–20% of patients experience chronic post-surgical pain (CPSP). Many will experience neuropathic characteristics. We describe the prevalence and patterns of neuropathic pain in a cohort of patients with CPSP three months after TKR. Methodology. Between 2016–2019, 363 patients with troublesome pain, ≤14 on Oxford Knee score pain subscale, at three months after TKR from eight NHS hospitals were recruited into the Support and Treatment After Replacement (STAR) trial. Self-reported neuropathic pain was assessed at three, nine and fifteen months after surgery using painDETECT and Douleur Neuropathique 4 (DN4). Results. At three months post-operative, 53% reported neuropathic pain on painDETECT and 74% on DN4. Half (56%) remained in neuropathic pain over the twelve-month follow-up period, 26% reported improvement, and 9% reported new neuropathic symtpoms or fluctuated in and out of neuropathic pain (9%). Overall mean neuropathic pain scores improved between three and 15 months after TKR. When the painDETECT cut-off score of ≥13(ambiguous/possible) was used, DN4 and painDETECT measures showed similar prevalence rates at each timepoint. Conclusion. Neuropathic pain is common among patients with CPSP at three months after TKR. Although symptoms improved over time, one quarter to one half of our cohort continued to report symptoms at fifteen months. We propose a painDETECT cutoff score of ≥13 be used to identify neuropathic features in the TKR population. Postoperative care should include identification, assessment, and treatment of neuropathic pain in patients with CPSP after TKR

Background. Low back pain can lead to neuroplastic changes in the central nervous system, known as nociplastic pain. As nociplastic pain may be provoked by premorbid sensory profiles, such profiles may be prognostic in the development of nociplastic pain over time. Objectives. To investigate whether four sensory profiles are prognostic in the development of symptoms of nociplastic pain in people with acute low back pain. Methods. A longitudinal type 2 prognostic factor research study was performed in accordance with the PROGRESS framework, using a baseline and a follow-up after 12 weeks, between the Adolescent/Adult Sensory Profile and the Central Sensitisation Inventory. Study participants were consecutively included from primary care physiotherapy practices randomly spread throughout the Netherlands. A multivariable regression analysis was performed to adjust sensory profiles by the level of pain, disability, age, and duration of low back pain. Results. After adjustment Low Registration B=0.41, 95%CI (0.37, 0.99), Sensory Seeking B=0.37, 95%CI (0.24, 0.73), Sensory Sensitive B=0.51, 95%CI (0.50, 1.06), Sensation Avoiding B=0.46, 95%CI (0.43, 0.99) were significantly associated with the development of nociplastic pain symptoms. Conclusion. Sensory profiles in people with acute low back pain predict symptoms of nociplastic pain after 12 weeks. Conflict of interest: No conflict of interest. Sources of funding: No funding obtained

Aims. The involvement of cyclin D1 in the proliferation of microglia, and the generation and maintenance of bone cancer pain (BCP), have not yet been clarified. We investigated the expression of microglia and cyclin D1, and the influences of cyclin D1 on pain threshold. Methods. Female Sprague Dawley (SD) rats were used to establish a rat model of BCP, and the messenger RNA (mRNA) and protein expression of ionized calcium binding adaptor molecule 1 (IBA1) and cyclin D1 were detected by reverse transcription-polymerase chain reaction (RT-PCR) and western blot, respectively. The proliferation of spinal microglia was detected by immunohistochemistry. The pain behaviour test was assessed by quantification of spontaneous flinches, limb use, and guarding during forced ambulation, mechanical paw withdrawal threshold, and thermal paw withdrawal latency. Results. IBA1 and cyclin D1 in the ipsilateral spinal horn increased in a time-dependent fashion. Spinal microglia proliferated in BCP rats. The microglia inhibitor minocycline attenuated the pain behaviour in BCP rats. The cyclin-dependent kinase inhibitor flavopiridol inhibited the proliferation of spinal microglia, and was associated with an improvement in pain behaviour in BCP rats. Conclusion. Our results revealed that the inhibition of spinal microglial proliferation was associated with a decrease in pain behaviour in a rat model of BCP. Cyclin D1 acts as a key regulator of the proliferation of spinal microglia in a rat model of BCP. Disruption of cyclin D1, the restriction-point control of cell cycle, inhibited the proliferation of microglia and attenuated the pain behaviours in BCP rats. Cyclin D1 and the proliferation of spinal microglia may be potential targets for the clinical treatment of BCP. Cite this article: Bone Joint Res 2022;11(11):803–813

Background. The association between lumbar intervertebral disc degeneration (LDD) and low back pain (LBP) is modest. We have recently shown that genetic propensity to pain is an effect modifier of the LDD-LBP relationship when LDD is defined as a summary score of LDD (LSUM), suggesting the association may be driven by individuals with the greatest genetic predisposition to pain. This study examined the association between individual spine magnetic resonance imaging (MRI)-determined LDD features and LBP in subgroups defined by genetic predisposition to pain. Method. We developed a polygenic risk score (PRS) for “genetic propensity to pain” defined as the number of non-back pain locations (head, face, neck/shoulder, stomach/abdomen, hip, and knee) with duration ≥3 months in 377,538 UK Biobank participants of European ancestry. This PRS was used to stratify TwinsUK MRI samples (n=645) into four strata of genetic propensity to pain. We examined the association between LBP and MRI features of lumbar disc height, disc signal intensity, disc bulge, and osteophytes with adjustments for age, sex, PRS strata, interaction terms for each MRI feature x PRS strata, and twin status. Results. We found significant effect modification of the LDD-LBP relationship by genetic propensity to pain for the lumbar MRI features of disc height (p=0.03 for the interaction term with highest quartile of genetically-predicted propensity to pain) and disc signal intensity (p=0.001), but not for disc bulge and osteophytes. Conclusion. Genetic propensity to pain modifies the association between individual LDD features and LBP and should be considered in LBP clinical studies. Conflicts of interest. No conflicts of interest. Sources of funding. No funding obtained. Acknowledgement. UKBB data were obtained under the project #18219. This paper is submitted to the Spine journal and is under review

Abstract. Background. Around 5–15% of patients will experience chronic postoperative pain after total knee replacement (TKR) surgery but the source of the pain is unknown. The aim of this study was to assesses patients six months after TKR using magnetic resonance imaging (MRI) of the knee, pain sensory profiles and assessments of pain catastrophizing thoughts. Methods. Forty-six patients had complete postoperative data and were included. MRI findings were scored according to the MRI Osteoarthritis Knee Score (MOAKS) recommendation for Hoffa synovitis, effusion size and bone marrow lesions. Pain sensory profiles included the assessment of pressure pain thresholds (PPTs), temporal summation of pain (TSP) and conditioned pain modulation (CPM). Pain catastrophizing was assessed using the pain catastrophizing scale (PCS). Clinical pain was evaluated using a visual analog scale (VAS, 0–10cm) and groups of moderate-to-severe (VAS>3) and non-to-mild postoperative pain (VAS≤3) were identified. Results. Patients with moderate-to-severe postoperative pain demonstrated higher grades of Hoffa synovitis (P<0.001) and effusion size (P<0.001), lower PPTs (P=0.039), higher TSP (P=0.001) and lower CPM (P=0.014) when compared to patients with non-to-mild postoperative pain. No differences were found in PCS scores. Linear regression models found TSP (P=0.013), PCS (P<0.001), Hoffa synovitis (P=0.036) and effusion size (P=0.003) as independent parameters contributing to the postoperative pain severity. Conclusion. These finding indicate that chronic postoperative after TKR is a combination of joint-related synovitis and effusion in combination with sensitization of central pain mechanisms and pain catastrophizing thoughts

Purpose of study and background. Psychological factors are considered to play a role in development and maintenance of chronic low back pain (CLBP). Stress or anxiety can change pain sensitivity; however, this has predominantly been studied in healthy individuals with limited work in individuals with musculoskeletal pain. The objective of this study was to quantify the effect of acute exposure to a psychosocial stressor on mechanical pain sensitivity in individuals with and without CLBP. Summary of methods and results. Six individuals with CLBP and 10 individuals without CLBP performed a 10-minute computer task under conditions of low and high psychosocial stress. Psychosocial stress was manipulated using mental maths and memory tasks combined with social evaluative threat. The effect of the stressor was evaluated using blood pressure, heart rate and the state anxiety component of the Spielberger State-Trait Anxiety Index. Mechanical pressure pain threshold (PPT) was recorded on the tibialis anterior muscle using a handheld digital pressure algometer. The stress manipulation increased self-reported anxiety (p<0.001), but not blood pressure or heart rate (p>0.06). Change in PPT from low to high stress was greater in the CLBP group (median ΔPPT = −0.5 kg/cm. 2. ) than in the control group (−0.15 kg/cm. 2. ; p=0.005). Conclusion. Individuals experienced an increase in pain sensitivity after acute exposure to a stressor designed to mimic low-level workplace stressors, and this increase was greater in individuals with CLBP than asymptomatic individuals. These results indicate that this experimental model can be used to study links between pain sensitivity and psychosocial stressors and increase our understanding of their potential role in CLBP. Conflicts of Interest: No conflicts of interest. Sources of funding: No funding obtained

Background. Embodiment- and distraction-based approaches to immersive virtual reality (IVR) show promise in treating persistent low back pain (PLBP). However, which approach is more effective is unclear. This study aims to evaluate the impact of distraction- and embodiment-based IVR on pain processing and patient-reported outcome measures in PLBP. Method. Individuals with PLBP were randomised to receive eight sessions of either distraction- or embodiment-based IVR over two weeks. Outcome measures were evaluated at baseline and after the eighth session. Pain processing was evaluated using conditioned pain modulation (CPM) and temporal summation (TS). Results. Three participants (n=2 embodiment, n=1 distraction) have completed all eight IVR sessions. Preliminary results indicate a decrease from pre to post-intervention in Numerical Pain Rating Scale score (pre: 5/10, 6/10, 5/10; post: 2/10, 5/10, 2/10) and Pain Catastrophising Scale score (pre: 34/52, 11/52, 38/52; post: 11/52, 8/52, 12/52), with no clear trend in other self-reported measures (Hospital Anxiety and Depression scale, Oswestry low back disability questionnaire, fear-avoidance beliefs questionnaire, Tampa scale of kinesiophobia). Preliminary results suggest a potential increase in NPRS absolute values from pre- to post-intervention in CPM (pre: -2.7, -2.3, -2.0; post: -3.3, -2.0, -4.3) and TS (pre-1.2, 2.5, 2.4; post: 1.4, 2.5, 3.1). Conclusion. Eight sessions of IVR may reduce pain severity and pain catastrophising in people with PLBP and may increase the efficacy of endogenous pain modulatory systems. Data collection is ongoing to compare the effect of distraction- and embodiment-based IVR. Conflicts of Interest. There are no conflicts of interest. Sources of Funding. This project is funded by the Saudi Arabia Cultural Bureau

Abstract. Background. ‘Free From Pain’ is a drug-free, injection injection-free, lifestyle-based musculoskeletal pain management programme for seniors. The programme empowers Seniors with relevant information and inspirational metaphors whilst providing them with validated exercises. The programme is also available as a published book (ISBN-0995676941). This pilot study aimed to assess the suitability and safety of the programme's exercises and the usefulness of the book before considering a larger study. Methods. Participants used 5-point Likert scales to evaluate the exercises. A rating of three or below on a Likert scale denoted non-agreement to a positive statement regarding the exercises. A rating of four or above denoted agreement. The Usefulness Scale for Patient Information Material (USE) was utilised to assess the book. Results. Of 30 participants who attended the programme, 25 completed the questionnaire (19 females and six males), with a mean age of 76 years. All the 25 participants were in agreement that the exercises were suitable, (x? = 4.6) and safe (x? = 4.56). 23 participants would also recommend the programme to family and friends? (x? = 4.48). The USE scale is divided into three, sub-domains: cognition (knowledge obtained); emotional (individual's ability to cope with the illness); and behavioural (ability to self-manage). The mean scores for the book on the cognitive, emotional, and behavioural sub-domains were 25.48, 24.08 and 24.04, respectively. Conclusion. Results indicate that the ‘Free From Pain’ exercises are suitable and safe. The book provides educational information that empowers participants to better their musculoskeletal health

Aims. Total hip arthroplasty (THA) is a common procedure to address pain and enhance function in hip disorders such as osteoarthritis. Despite its success, postoperative patient recovery exhibits considerable heterogeneity. This study aimed to investigate whether patients follow distinct pain trajectories following THA and identify the patient characteristics linked to suboptimal trajectories. Methods. This retrospective cohort study analyzed THA patients at a large academic centre (NYU Langone Orthopedic Hospital, New York, USA) from January 2018 to January 2023, who completed the Patient-Reported Outcomes Measurement Information System (PROMIS) pain intensity questionnaires, collected preoperatively at one-, three-, six-, 12-, and 24-month follow-up times. Growth mixture modelling (GMM) was used to model the trajectories. Optimal model fit was determined by Bayesian information criterion (BIC), Vuong-Lo-Mendell-Rubin likelihood ratio test (VLMR-LRT), posterior probabilities, and entropy values. Association between trajectory groups and patient characteristics were measured by multinomial logistic regression using the three-step approach. Results. Among the 1,249 patients, a piecewise GMM model revealed three distinct pain trajectory groups: 56 patients (4.5%) in group 1; 1,144 patients (91.6%) in group 2; and 49 patients (3.9%) in group 3. Patients in group 2 experienced swift recovery post-THA and minimal preoperative pain. In contrast, groups 1 and 3 initiated with pronounced preoperative pain; however, only group 3 exhibited persistent long-term pain. Multinomial regression indicated African Americans were exceedingly likely to follow trajectory groups 1 (odds ratio (OR) 2.73) and 3 (OR 3.18). Additionally, odds of membership to group 3 increased by 12% for each BMI unit rise, by 19% for each added postoperative day, and by over four if discharged to rehabilitation services (OR 4.07). Conclusion. This study identified three distinct pain trajectories following THA, highlighting the role of individual patient factors in postoperative recovery. This emphasizes the importance of preoperatively addressing modifiable risk factors associated with suboptimal pain trajectories, particularly in at-risk patients. Cite this article: Bone Jt Open 2024;5(3):174–183

Aims. Pain is the most frequent complaint associated with osteonecrosis of the femoral head (ONFH), but the factors contributing to such pain are poorly understood. This study explored diverse demographic, clinical, radiological, psychological, and neurophysiological factors for their potential contribution to pain in patients with ONFH. Methods. This cross-sectional study was carried out according to the “STrengthening the Reporting of OBservational studies in Epidemiology” statement. Data on 19 variables were collected at a single timepoint from 250 patients with ONFH who were treated at our medical centre between July and December 2023 using validated instruments or, in the case of hip pain, a numerical rating scale. Factors associated with pain severity were identified using hierarchical multifactor linear regression. Results. Regression identified the following characteristics as independently associated with higher pain score, after adjustment for potential confounders: Association Research Circulation Osseous classification stage IIIa or IIIb, bone marrow oedema, grade 3 joint effusion, as well as higher scores on pain catastrophizing, anxiety, and central sensitization. The final model explained 69.7% of observed variance in pain scores, of which clinical and radiological factors explained 37%, while psychological and neurophysiological factors explained 24% and demographic factors explained 8.7%. Conclusion. Multidimensional characteristics jointly contribute to the severity of pain associated with ONFH. These findings highlight the need to comprehensively identify potential contributors to pain, and to personalize management and treatment accordingly. Cite this article: Bone Joint Res 2024;13(11):673–681

Background: Anterior cruciate ligament (ACL) injury and re-injury rates are high and continue to rise in adolescents. After surgical reconstruction, less than 50% of patients return to their pre-injury level of physical activity. Clearance for return-to-play and rehabilitation progression typically requires assessment of performance during functional tests. Pain may impact this performance. However, the patient's level of pain is often overlooked during these assessments. Purpose: To investigate the level of pain during functional tests in adolescents with ACL injury. Fifty-nine adolescents with ACL injury (ACLi; female n=43; 15 ± 1 yrs; 167.6 ± 8.4 cm; 67.8 ± 19.9 kg) and sixty-nine uninjured (CON; female n=38; 14 ± 2 yrs; 165.0 ± 10.8 cm; 54.2 ± 11.5 kg) performed a series of functional tests. These tests included: maximum voluntary isometric contraction (MVIC) and isokinetic knee flexion-extension strength tests, single-limb hop tests, double-limb squats, countermovement jumps (CMJ), lunges, drop-vertical jumps (DVJ), and side-cuts. Pain was reported on a 5-point Likert scale, with 1 indicating no pain and 5 indicating extreme pain for the injured limb of the ACLi group and non-dominant limb for the CON group, after completion of each test. Chi-Square test was used to compare groups for the level of pain in each test. Analysis of the level of pain within and between groups was performed using descriptive statistics. The distribution of the level of pain was different between groups for all functional tests (p≤0.008), except for ankle plantar flexion and hip abduction MVICs (Table 1). The percentage of participants reporting pain was higher in the ACLi group in all tests compared to the CON group (Figure 1). Participants most often reported pain during the strength tests involving the knee joint, followed by the hop tests and dynamic tasks, respectively. More specifically, the knee extension MVIC was the test most frequently reported as painful (70% of the ACLi group), followed by the isokinetic knee flexion-extension test, with 65% of ACLi group. In addition, among all hop tests, pain was most often reported during the timed 6m hop (53% of ACLi), and, among all dynamic tasks, during the side-cut (40% of ACLi) test (Figure 1). Furthermore, the tests that led to the higher levels of pain (severe or extreme) were the cross-hop (9.8% of ACLi), CMJ (7.1% of ACLi), and the isokinetic knee flexion-extension test (11.5% of ACLi) (Table 1). Adolescents with and without ACL injury reported different levels of pain for all functional tasks, except for ankle and hip MVICs. The isokinetic knee flexion-extension test resulted in greater rates of severe or extreme pain and was also the test most frequently reported as painful. Functional tests that frequently cause pain or severe level of pain (e.g., timed 6m and cross hops, side-cut, knee flexion/extension MVICs and isokinetic tests) might not be the first test choices to assess function in patients after ACL injury/reconstruction. Reported pain during functional tests should be considered by clinicians and rehabilitation team members when evaluating a patient's readiness to return-to-play. For any figures or tables, please contact the authors directly

Purpose. Cognitive Muscular Therapy (CMT) is a new treatment for low back pain which integrates psychological techniques for pain management alongside training to improve postural control. Rather than focus on postural alignment or strength, CMT aims to improve the regulation of postural tone (low-level activity which supports the body against gravity). This is achieved by teaching patients an awareness of compensatory paraspinal activation, which can be triggered by overactivity of the abdominal muscles. The aim of this study was to understand whether CMT could reduce symptoms associated with low back pain and improve paraspinal muscle activation. Methods and results. Fifteen patients with chronic low back pain received seven weekly sessions of CMT from a physiotherapist. Clinical data was captured at baseline and two weeks after the intervention using the Roland-Morris questionnaire and the pain catastrophising scale. Activation of the erector spinae muscle during walking was also measured at baseline and after the final intervention session. Change data were analysed using paired t-tests. There was a 75% reduction (p<0.001) in the Roland-Morris score from a mean (SD) of 9.3(2.9) to 2.3(2.6), along with a 78% reduction in pain catastrophising (p<0.002) from 16.6(13) to 3.7(4.8). Activation of the contralateral erector spinae muscles reduced by 30% (p<0.01) during the contralateral swing phase of walking. Conclusion. In this small sample, CMT delivered large clinical improvements and reduced activation of the low back muscles during walking. Larger randomised trials are now required to confirm whether CMT could outperform existing physiotherapy treatments for chronic back pain. Conflict of interest. No conflicts of interest. Source of funding. University of Salford

Radioprotective gowns are an essential part of operating in orthopaedicse. As we are aware from the evidence, surgeons, and in particular orthopaedic surgeons, are at risk of developing chronic neck and back pain. This is likely a result of the combination of of long operations, heavy equipment, radioprotective gowns and poor ergonomic set up. Women are a minority in orthopaedics. Amongst trainees there has been an improvement with 20–25% of current trainees are women, however at consultant level this percentage is a lot lower at 5–7%. Radioprotective gowns worn by trainees are frequently not well fitted and few surgeons have access to bespoke fitted gowns. A questionnaire given to 32 trainees in the region found a significant burden of back pain in trainees and 57% of surgeons felt their gowns were not appropriately fitted. In this study every woman questioned reported back pain as a result of operating and 87% felt the gowns used exacerbated back pain, this figure was 56% in men. 80% of surgeons felt that surgeons would benefit from bespoke fitted gowns, even those that did not themselves have severe back pain. 45% of trainees felt their pain was moderate to severe. In surgery we have the responsibility to protect ourselves and our colleagues from work based injury and illness. Back pain should not be ignored as a symptom and radioprotective gowns is a good place to start. Overall the majority the gowns exacerbated their back pain during or after procedures, worse in women as described above. We can use this data and do what we can to provide trainees with a range of sizes whilst working in hospitals during their training. Anectodally women sizes were less available in the departments and we can work to improve this and reduce the burden of pain amongst surgeons

Purpose of the study and background. Although pain is usually described as a private experience, how pain is understood and responded to by others is important. A crucial feature of this process is empathy. The aim of this study was to examine the relationship between empathy for pain and observers' health anxiety and fear of pain. The role of the observer's sex and age were also examined. Methods and results. In this study 159 participants (73 males, mean age=41, SD=19.6) were presented with 16 images of individuals in pain (8 female, 8 male), and subsequently rated their empathy towards them. Participants then completed the fear of pain and health anxiety measures. Both fear of pain and health anxiety were positively associated with empathy for pain, but in the regression model only fear of pain was a significant positive predictor of empathy for pain (p< .001). Further analysis revealed that when controlling for the effects of fear of pain, the correlation between health anxiety and empathy became non-significant. The same results were found when the overall empathy for pain score was split into empathy for male and female images. Observers' sex and age were not significant predictors of empathy for pain. Conclusion. The results highlight the role of fear of pain in empathy for pain, where more fearful observers had higher levels of empathy for pain. They support current theories of empathy and the role of the underlying top-down processes in decoding another's pain. Conflict of interest: None. Sources of funding: None

Background. Over 55,000 spinal operations are performed annually in the NHS. Effective postoperative analgesia facilitates early mobilisation and assists rehabilitation and hospital discharge, but is difficult to achieve with conventional, opioid-based, oral analgesia. The clinical and cost-effectiveness of two alternative techniques, namely intrathecal opioid and the more novel erector-spinae plane blockade, is unknown. The Pain Relief After Instrumented Spinal Surgery (PRAISE) trial aims to evaluate these techniques. Methods. PRAISE is a multicentre, prospective, parallel group, patient-blinded, randomised trial, seeking to recruit 456 adult participants undergoing elective, posterior lumbar-instrumented spinal surgery from up to 25 NHS hospitals. Participants will be randomised 1:1:1 to receive (1) Usual Care with local wound infiltration, (2) Intrathecal Opioid plus Usual Care with local wound infiltration or (3) Erector Spinae Plane blockade plus Usual Care with no local wound infiltration. The primary outcome is pain on movement on a 100mm visual analogue scale at 24 hours post-surgery. Secondary outcomes include pain at rest, leg pain, quality of recovery (QoR-15), postoperative opioid consumption, time to mobilisation, length of hospital stay, health utility (EQ-5D-5L), adverse events and resource use. Parallel economic evaluation will estimate incremental cost-effectiveness ratios. Results. Differences in the primary outcome at 24 hours will be estimated by mixed-effects linear regression modelling, with fixed effects for randomisation factors and other important prognostic variables, and random effects for centre, using the as-randomised population. Treatment effects with 95% confidence intervals will be presented. Conclusion. The study is due to open in May 2024 and complete in 2026. Conflicts of Interest. No conflicts of interest declared. Sources of Funding. NIHR Health Technology Award – grant number NIHR153170. Trial presentations so far. APOMP 2023 and 2024; RCOA conference, York, November 2023; Faculty of Pain Management training day, London, February 2024

Background. There is a paucity of prognosis research in patients with neuropathic low back-related leg pain (LBLP) in primary care. Purpose. To investigate the clinical course and prognostic factors in primary care LBLP patients consulting with neuropathic pain (NP). Methods. LBLP patients in a primary-care cohort study (n=606) completed the self-report version of Leeds Assessment for Neurological Symptoms and Signs (s-LANSS, score of ≥12 indicates possible NP) at baseline and 4-months. Mixed effects models compared pain-intensity (highest of mean leg or mean back pain - 0–10 NRS at baseline, 4-months, 12-months and 3-years) between those with persistent NP (s-LANSS ≥12 at baseline and 4-months) and those without (s-LANSS ≥12 at baseline and <12 at 4-months). Univariable and multivariable binary logistic regression examined association between potential prognostic factors (chosen from baseline self-report questionnaires, clinical examination, MRI scan findings) and persistent NP. Multiple imputation was used to account for missing data. Results. 44% (72/164) of patients with NP at baseline had persistent NP at 4-months. Mean pain intensity of patients with persistent NP was higher at 4-months, 12-months and 3-years compared to those without. In univariable analysis, only pain self-efficacy was significantly associated with persistent NP (OR 0.98, 95% CI 0.96 to 0.998). In multivariable analysis, none of the 7 investigated factors were significantly associated with persistent NP. Conclusion. Patients with persistent NP were consistently worse-off up to 3-years follow-up compared to those without. It was difficult to identify those patients with NP at baseline who would have persistent NP at 4-months. No conflicts of interest. Sources of funding: Sarah Harrisson is a Clinical Doctoral Fellow funded through a National Institute for Health Research (NIHR) Research Professorship for Nadine Foster (NIHR-RP-011-015). Nadine Foster is a NIHR Senior Investigator. Kika Konstantinou is supported by a Higher Education Funding Council for England/ National Institute for Health Research Senior Clinical Lectureship. The views expressed in this publication are those of the author(s), not necessarily those of the NHS, NIHR or the Department of Health and Social Care. This work relates to an Education and Continued Professional Development (level 2) award by the Musculoskeletal Association of Chartered Physiotherapists to Sarah Harrisson (June 2016)

Glutamate regulates the expression of apoptosis-related genes and triggers the apoptosis of fibroblasts in rotator cuff tendons. Subacromial bursitis is always accompanied by symptomatic rotator cuff tear (RCT). However, no study has been reported on the presence of glutamate in subacromial bursa and on its involvement of shoulder pain in patients who had RCT. The purposes of this study were to determine whether the glutamate expression in subacromial bursa is associated with the presence of RCT and with the severity of shoulder pain accompanying RCT. Subacromial bursal tissues were harvested from patients who underwent arthroscopic rotator cuff tendon repair or glenoid labral repair with intact rotator cuff tendon. Glutamate tissue concentrations were measured, using a glutamate assay kit. Expressions of glutamate and its receptors in subacromial bursae were histologically determined. The sizes of RCT were determined by arthroscopic findings, using the DeOrio and Cofield classification. The severity of shoulder pain was determined, using visual analog scale (VAS). Any associations between glutamate concentrations and the size of RCT were evaluated, using logistic regression analysis. The correlation between glutamate concentrations and the severity of pain was determined, using the Pearson correlation coefficient. Differences with a probability <0.05 were considered statistically significant. Glutamate concentrations showed significant differences between the torn tendon group and the intact tendon group (P = 0.009). Concentrations of glutamate significantly increased according to increases in tear size (P < 0.001). In histological studies, the expressions of glutamate and of its ionotropic and metabotropic receptors have been confirmed in subacromial bursa. Glutamate concentrations were significantly correlated with pain on VAS (Rho=0.56 and P =0.01). The expression of glutamate in subacromial bursa is significantly associated with the presence of RCT and significantly correlated with its accompanying shoulder pain. Acknowledgements: This research was supported by the Basic Science Research Program, through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2015R1D1A3A01018955 and 2017R1D1A1B03035232)

Purpose: To evaluate whether the presence of leg pain influences healthcare use and work disability in patients with low back pain (LBP). Methods: Prospective cohort study of primary care consulters with LBP in North Staffordshire and Cheshire. Patients completed questionnaires at baseline and 12 months, collecting data on back pain, work and healthcare utilisation. At baseline, patients were classified as reporting. LBP only,. LBP + leg pain above knee only or. LBP + leg pain extending below the knee. Results: 456 patients had complete data and were included in this analysis. At baseline, 191 (42%) reported LBP only, 116 (25%) leg pain above the knee and 149 (33%) leg pain below the knee. In comparison to those with LBP only, patients reporting leg pain below knee were more likely to be referred to secondary care (46% vs 17%, p< 0.01), to re-consult their GP (68% vs 43%, p< 0.01) and to receive physiotherapy (40% vs 21%, p< 0.01) in the 12 months after baseline. At 12 months, those with leg pain below knee were less likely to be employed (67% vs 81%, p=0.01) than patients with LBP alone, more likely to have time off work (55% vs 31%, p< 0.01) or be on reduced work duties. Conclusions: Self-reported leg pain is common. These patients access significantly more healthcare and are more likely to be off work over 12 months. This highlights the need for early identification of patients with concurrent leg pain and appropriate targeting of interventions to reduce work disability. Conflicts of Interest: None. Funding source: Arthritis Research Campaign

Background. Chronic pain after joint replacement is common, affecting approximately 10% of patients after total hip replacement (THR) and 20% of patients after total knee replacement (TKR). Heightened generalised sensitivity to nociceptive input could be a risk factor for the development of this pain. The primary aim of this study was to investigate whether preoperative widespread pain sensitivity was associated with chronic pain after joint replacement. Methods. Data were analysed from 254 patients receiving THR and 239 patients receiving. TKR. Pain was assessed preoperatively and at 12 months after surgery using the Western Ontario and McMaster Universities Osteoarthritis Pain Scale. Preoperative widespread pain sensitivity was assessed through measurement of pressure pain thresholds (PPTs) at the forearm using an algometer. Statistical analysis was conducted using linear regression and linear mixed models, and adjustments were made for confounding variables. Results. In both the THR and TKR cohort, lower PPTs (heightened widespread pain. sensitivity) were significantly associated with higher preoperative pain severity. Lower PPTs were also significantly associated with higher pain severity at 12 months after surgery in the THR cohort. However, PPTs were not associated with the change in pain severity from preoperative to 12 months postoperative in either the TKR or THR cohort. Conclusions. These findings suggest that although preoperative widespread pressure pain sensitivity is associated with pain severity before and after joint replacement, it is not a predictor of the amount of pain relief that patients gain from joint replacement surgery, independent of preoperative pain severity. Level of Evidence. 2. Approvals. The APEX trials were registered as an International Standardised Randomised Controlled Trial (96095682), approved by Southampton and South West Hampshire Research Ethics Committee(09/H0504/94) and all participants provided informed written consent