Mechanisms of bone pain: Progress in research from bench to bedside

Integrative review of the gut microbiome’s role in pain management for orthopaedic conditions

The gut microbiome, a complex ecosystem of microorganisms, has a significant role in modulating pain, particularly within orthopaedic conditions. Its impact on immune and neurological functions is underscored by the gut-brain axis, which influences inflammation, pain perception, and systemic immune responses. This integrative review examines current research on how gut dysbiosis is associated with various pain pathways, notably nociceptive and neuroinflammatory mechanisms linked to central sensitization. We highlight advancements in meta-omics technologies, such as metagenomics and metaproteomics, which deepen our understanding of microbiome-host interactions and their implications in pain. Recent studies emphasize that gut-derived short-chain fatty acids and microbial metabolites play roles in modulating neuroinflammation and nociception, contributing to pain management. Probiotics, prebiotics, synbiotics, and faecal microbiome transplants are explored as potential therapeutic strategies to alleviate pain through gut microbiome modulation, offering an adjunct or alternative to opioids. However, variability in individual microbiomes poses challenges to standardizing these treatments, necessitating further rigorous clinical trials. A multidisciplinary approach combining microbiology, immunology, neurology, and orthopaedics is essential to develop innovative, personalized pain management strategies rooted in gut health, with potential to transform orthopaedic pain care.

Extensive Periosteal Injury During Fracture Induces Long-Term Pain in Mice

Bone fractures pose a significant public health challenge, often necessitating surgical interventions to facilitate bone healing and functional recovery. Sensory nerve fibers innervate various compartments of the bone tissue, with the periosteum exhibiting the most extensive innervation that is susceptible to injury during trauma. Despite its importance, the effect of injured periosteum on fracture pain remains unknown. This study examines the impact of extensive periosteal injury on fracture pain by using a mouse model. Periosteal injury is induced by mechanical resection during unilateral transverse fracture and compared to transverse fractures with no periosteal injury. Our results demonstrate that extensive periosteal injury induces severe and long-term pain, as assessed by von Frey and dynamic weight bearing measurements, for up to 12 weeks postfracture. Immunofluorescence staining revealed an increase in local neurofilament heavy polypeptide (NF200 +) nerve innervation and an elevated number of calcitonin gene-related peptide (CGRP +) expressing neurons in the dorsal root ganglion (DRG). Additionally, flow cytometric analyses revealed increased presence of myeloid immune cells in the DRG. Furthermore, bone healing in fractures with extensive periosteal injury exhibited reduced callus size at all time points as assessed by Faxitron X-ray imaging. This study describes a previously unknown effect of extensive periosteal injury in exacerbating fracture pain and establishes a potential model to study long-term orthopedic fracture pain.

Metastatic neuroendocrine carcinoma of the small intestine presenting as temporomandibular disorder

BACKGROUND

Neuroendocrine carcinomas (NECs) are rare tumors from hormone-secreting neuroendocrine cells, often within the gastrointestinal tract. The authors report what is, to their best knowledge, the first case of a small intestine NEC metastasizing to the temporomandibular joint (TMJ).

CASE DESCRIPTION

A 60-year-old man came to the oral medicine, oncology, and orofacial pain clinic with a chief concern of left-sided jaw pain. Clinical examination revealed left TMJ arthralgia and deep masseter myalgia, and results of imaging showed both osteoblastic and osteolytic changes in the left TMJ. A comprehensive diagnostic approach, including detailed history, clinical evaluation, and advanced imaging techniques, such as positron emission tomography computed tomography, was used to establish an accurate diagnosis.

PRACTICAL IMPLICATIONS

This case highlights the importance of considering metastasis in differential diagnosis of TMJ pain in patients with NEC, underscoring collaboration between oncology and orofacial pain specialists for accurate diagnosis and effective management.

Functional Hydrogel Interfaces for Cartilage and Bone Regeneration

Effective treatment of bone diseases is quite tricky due to the unique nature of bone tissue and the complexity of the bone repair process. In combination with biological materials, cells and biological factors can provide a highly effective and safe treatment strategy for bone repair and regeneration, especially based on these multifunctional hydrogel interface materials. However, itis still a challenge to formulate hydrogel materials with fascinating properties (e.g., biological activity, controllable biodegradability, mechanical strength, excellent cell/tissue adhesion, and controllable release properties) for their clinical applications in complex bone repair processes. In this review, we will highlight recent advances in developing functional interface hydrogels. We then discuss the barriers to  producing of functional hydrogel materials without sacrificing their inherent properties, and potential applications in cartilage and bone repair are discussed. Multifunctional hydrogel interface materials can serve as a fundamental building block for bone tissue engineering.

Patient-Reported Outcomes in Autosomal Dominant Osteopetrosis: Findings From the Osteopetrosis Registry Study

CONTEXT

Autosomal dominant osteopetrosis (ADO) is a rare sclerotic bone disease characterized by impaired osteoclast activity, resulting in high bone mineral density and skeletal fragility. The full phenotype and disease burden on patients' daily lives has not been systematically measured.

OBJECTIVE

We developed an online registry to ascertain population-based data on the spectrum and rate of progression of disease and to identify relevant patient-centered outcomes that could be used to measure treatment effects and guide the design of future clinical trials.

METHODS

Cross-sectional data from participants with osteopetrosis were collected using an online REDCap-based database. Thirty-four participants with a confirmed diagnosis of ADO, aged 4-84 years were included. Participants aged 18 years and older completed the PROMIS 57, participants aged 8-17 years completed the PROMIS Pediatric 49, and parents of participants aged <18 years completed the PROMIS Parent Proxy 49.

RESULTS

Based on the PROMIS 57, relative to the general population, adults with ADO reported low physical function and low ability to participate in social roles and activities, and high levels of anxiety, fatigue, sleep problems, and pain interference. Daily pain medications were reported by 24% of the adult population. In contrast, neither pediatric participants nor their parent proxy reported a negative impact on health-related quality of life.

CONCLUSION

Data from this registry demonstrate the broad spectrum of ADO disease severity and high impact on health-related quality of life in adults with ADO.

Neurovascularization inhibiting dual responsive hydrogel for alleviating the progression of osteoarthritis

Treating osteoarthritis (OA) associated pain is a challenge with the potential to significantly improve patients lives. Here, we report on a hydrogel for extracellular RNA scavenging and releasing bevacizumab to block neurovascularization at the osteochondral interface, thereby mitigating OA pain and disease progression. The hydrogel is formed by cross-linking aldehyde-phenylboronic acid-modified sodium alginate/polyethyleneimine-grafted protocatechuic acid (OSAP/PPCA) and bevacizumab sustained-release nanoparticles (BGN@Be), termed OSPPB. The dynamic Schiff base bonds and boronic ester bonds allow for injectability, self-healing, and pH/reactive oxygen species dual responsiveness. The OSPPB hydrogel can significantly inhibit angiogenesis and neurogenesis in vitro. In an in vivo OA model, intraarticular injection of OSPPB accelerates the healing process of condyles and alleviates chronic pain by inhibiting neurovascularization at the osteochondral interface. The injectable hydrogel represents a promising technique to treat OA and OA associated pain.

Chronic Pain and Bone-Related Pathologies: A Narrative Review

Purpose

Pain related to bone may occur as a result of trauma, bone fracture, genetic disease, arthritis, benign or malignant primary bone tumors and bone cancer metastases. We discuss the pathophysiology of chronic bone-related pain, treatment options and therapeutic perspectives.

Methods

Using predefined terms, we searched PubMed, MEDLINE, and Google Scholar for meta-analyses, evidence-based reviews, and clinical practice guidelines. This narrative article reviews pathologies linked to chronic bone pain and discusses the preventive and therapeutic strategies for better bone pain management.

Results

Pathophysiology of bone-related pain is complex, especially in cancer conditions and missing gaps are underlined. Treatment of pain, after adequate evaluation, includes classical analgesics, adjuvants for neuropathic and refractory pain, specific bone drugs, surgery and non-pharmacological approaches. Prevention of chronic bone pain encompasses prevention of central sensitization and of causal diseases.

Conclusion

Translational research, drug repurposing, an interdisciplinary approach and a person-centered assessment to evaluate, beyond pain, physical, social and functional abilities, are proposed future directions to improve chronic bone pain management and optimize independence and quality of life.

Summary

Chronic bone-related pain is frequent and is associated with an impairment of quality of life. In this review, we summarize the pathophysiology of chronic bone pain, describe treatment approaches and envisage new avenues for pain alleviation. Our article will help doctors manage chronic bone pain and address unmet needs for future research to alleviate bone-related pain.

Bone mineral density is not associated with incident high-intensity back pain: a 10-year cohort study in men

Although patients believe that osteoporosis is a painful condition, health professionals assume it is painless unless a fracture occurs. The association between BMD and back pain has not been examined longitudinally in community-based adults in an unbiased population using gold-standard measures. This study aimed to examine the association between BMD and incident high-intensity back pain and/or high disability over 10 years in Australian men without high-intensity symptoms at baseline. Men with no high-intensity back pain and/or high disability attending the Geelong Osteoporosis Study at the 5-year visit (occurring between 2006-2010) (considered the baseline for the current study) were followed for 10 years (reassessed between 2016-2021). Back pain and disability were assessed using the Graded Chronic Pain Scale at both time points. At baseline, DXA was used to measure lumbar spine and total hip BMD and spinal artefacts. The relationships between BMD and incident high-intensity pain and/or high disability at follow-up were examined using binary logistic regression, adjusted for age, body mass index, depression, education, smoking, mobility, and spinal artefacts. A total of 679 participants had no to low-intensity pain and/or no to low disability at baseline. A total of 441 attended follow-up, providing back pain and disability data. Thirty-seven men developed high-intensity pain and/or high disability. No association of BMD at any site was seen with incident high-intensity pain and/or high disability. BMD was not associated with incident high-intensity pain or disability in community-based men. These data provide evidence to dispel the erroneous community-held belief that low BMD is related to back pain and disability.

Sensory nerve regulation of bone homeostasis: Emerging therapeutic opportunities for bone-related diseases

Understanding the intricate interplay between sensory nerves and bone tissue cells is of paramount significance in the field of bone biology and clinical medicine. The regulatory role of sensory nerves in bone homeostasis offers a novel perspective for the development of targeted therapeutic interventions for a spectrum of bone-related diseases, including osteoarthritis, osteoporosis, and intervertebral disc degeneration. By elucidating the mechanisms through which sensory nerves and their neuropeptides influence the differentiation and function of bone tissue cells, this review aims to shed light on emerging therapeutic targets that harness the neuro-skeletal axis for the treatment and management of debilitating bone disorders. Moreover, a comprehensive understanding of sensory nerve-mediated bone regulation may pave the way for the development of innovative strategies to promote bone health and mitigate the burden of skeletal pathologies in clinical practice.

Promotion of Bone Formation in a Rat Osteoporotic Vertebral Body Defect Model via Suppression of Osteoclastogenesis by Ectopic Embryonic Calvaria Derived Mesenchymal Stem Cells

Osteoporotic vertebral compression fractures (OVCFs) are the most prevalent fractures among patients with osteoporosis, leading to severe pain, deformities, and even death. This study explored the use of ectopic embryonic calvaria derived mesenchymal stem cells (EE-cMSCs), which are known for their superior differentiation and proliferation capabilities, as a potential treatment for bone regeneration in OVCFs. We evaluated the impact of EE-cMSCs on osteoclastogenesis in a RAW264.7 cell environment, which was induced by the receptor activator of nuclear factor kappa-beta ligand (RANKL), using cytochemical staining and quantitative real-time PCR. The osteogenic potential of EE-cMSCs was evaluated under various hydrogel conditions. An osteoporotic vertebral body bone defect model was established by inducing osteoporosis in rats through bilateral ovariectomy and creating defects in their coccygeal vertebral bodies. The effects of EE-cMSCs were examined using micro-computed tomography (μCT) and histology, including immunohistochemical analyses. In vitro, EE-cMSCs inhibited osteoclast differentiation and promoted osteogenesis in a 3D cell culture environment using fibrin hydrogel. Moreover, μCT and histological staining demonstrated increased new bone formation in the group treated with EE-cMSCs and fibrin. Immunostaining showed reduced osteoclast activity and bone resorption, alongside increased angiogenesis. Thus, EE-cMSCs can effectively promote bone regeneration and may represent a promising therapeutic approach for treating OVCFs.

Senescence of endplate osteoclasts induces sensory innervation and spinal pain

Spinal pain affects individuals of all ages and is the most common musculoskeletal problem globally. Its clinical management remains a challenge as the underlying mechanisms leading to it are still unclear. Here, we report that significantly increased numbers of senescent osteoclasts (SnOCs) are observed in mouse models of spinal hypersensitivity, like lumbar spine instability (LSI) or aging, compared to controls. The larger population of SnOCs is associated with induced sensory nerve innervation, as well as the growth of H-type vessels, in the porous endplate. We show that deletion of senescent cells by administration of the senolytic drug Navitoclax (ABT263) results in significantly less spinal hypersensitivity, spinal degeneration, porosity of the endplate, sensory nerve innervation and H-type vessel growth in the endplate. We also show that there is significantly increased SnOC-mediated secretion of Netrin-1 and NGF, two well-established sensory nerve growth factors, compared to non-senescent OCs. These findings suggest that pharmacological elimination of SnOCs may be a potent therapy to treat spinal pain.

Senescence of endplate osteoclasts induces sensory innervation and spinal pain

Spinal pain affects individuals of all ages and is the most common musculoskeletal problem globally. Its clinical management remains a challenge as the underlying mechanisms leading to it are still unclear. Here, we report that significantly increased numbers of senescent osteoclasts (SnOCs) are observed in mouse models of spinal hypersensitivity, like lumbar spine instability (LSI) or aging, compared to controls. The larger population of SnOCs is associated with induced sensory nerve innervation, as well as the growth of H-type vessels, in the porous endplate. We show that deletion of senescent cells by administration of the senolytic drug Navitoclax (ABT263) results in significantly less spinal hypersensitivity, spinal degeneration, porosity of the endplate, sensory nerve innervation, and H-type vessel growth in the endplate. We also show that there is significantly increased SnOC-mediated secretion of Netrin-1 and NGF, two well-established sensory nerve growth factors, compared to non-senescent OCs. These findings suggest that pharmacological elimination of SnOCs may be a potent therapy to treat spinal pain.

Treatment of Pelvic and Spinal Bone Metastases: Radiotherapy and Hyperthermia Alone vs. in Combination

Painful pelvic and spinal bone metastases are a considerable challenge for doctors and patients. Conventional therapies include morphine-equivalent medication (MeM) and local radiotherapy (RT), but these interventions are not always successful. More recently, hyperthermia (HT) has been applied to complement RT and MeM, and this complex approach has shown promising synergistic results. The objective of our study was to present the results of RT combined with a special kind of HT (modulated electrohyperthermia, mEHT), in which some of the thermal effect is contributed by equivalent nonthermal components, drastically reducing the necessary power and energy. This retrospective study included 61 patients divided into three groups with pelvic and spinal bone metastases to compare the effects of RT and mEHT alone and in combination (RT + mEHT). A detailed evaluation of pain intensity, measured by the brief pain inventory score, MeM use, and breakthrough pain episodes, revealed no significant differences between RT and mEHT alone; thus, these individual methods were considered equivalent. However, RT + mEHT yielded significantly better results in terms of the above parameters. Clinically, mEHT has a lower risk of adverse thermal effects, and due to its efficacy, mEHT can be used to treat RT-resistant lesions.

Zinc based biodegradable metals for bone repair and regeneration: Bioactivity and molecular mechanisms

Bone fractures and critical-size bone defects are significant public health issues, and clinical treatment outcomes are closely related to the intrinsic properties of the utilized implant materials. Zinc (Zn)-based biodegradable metals (BMs) have emerged as promising bioactive materials because of their exceptional biocompatibility, appropriate mechanical properties, and controllable biodegradation. This review summarizes the state of the art in terms of Zn-based metals for bone repair and regeneration, focusing on bridging the gap between biological mechanism and required bioactivity. The molecular mechanism underlying the release of Zn ions from Zn-based BMs in the improvement of bone repair and regeneration is elucidated. By integrating clinical considerations and the specific bioactivity required for implant materials, this review summarizes the current research status of Zn-based internal fixation materials for promoting fracture healing, Zn-based scaffolds for regenerating critical-size bone defects, and Zn-based barrier membranes for reconstituting alveolar bone defects. Considering the significant progress made in the research on Zn-based BMs for potential clinical applications, the challenges and promising research directions are proposed and discussed.

Knee osteoarthritis pendulum therapy: In vivo evaluation and a randomised, single-blind feasibility clinical trial

Background

Exercise is recommended as the first-line management for knee osteoarthritis (KOA); however, it is difficult to determine which specific exercises are more effective. This study aimed to explore the potential mechanism and effectiveness of a leg-swinging exercise practiced in China, called 'KOA pendulum therapy' (KOAPT). Intraarticular hydrostatic and dynamic pressure (IHDP) are suggested to partially explain the signs and symptoms of KOA. As such this paper set out to explore this mechanism in vivo in minipigs and in human volunteers alongside a feasibility clinical trial. The objective of this study is 1) to analyze the effect of KOAPT on local mechanical and circulation environment of the knee in experimental animals and healthy volunteers; and 2) to test if it is feasible to run a large sample, randomized/single blind clinical trial.

Methods

IHDP of the knee was measured in ten minipigs and ten volunteers (five healthy and five KOA patients). The effect of leg swinging on synovial blood flow and synovial fluid content depletion in minipigs were also measured. Fifty KOA patients were randomly divided into two groups for a feasibility clinical trial. One group performed KOAPT (targeting 1000 swings/leg/day), and the other performed walking exercise (targeting 4000 steps/day) for 12 weeks with 12 weeks of follow-up.

Results

The results showed dynamic intra-articular pressure changes in the knee joint, increases in local blood flow, and depletion of synovial fluid contents during pendulum leg swinging in minipigs. The intra-articular pressure in healthy human knee joints was -11.32 ± 0.21 (cmH2O), whereas in KOA patients, it was -3.52 ± 0.34 (cmH2O). Measures were completed by 100% of participants in all groups with 95-98% adherence to training in both groups in the feasibility clinical trial. There were significant decreases in the Oxford knee score in both KOAPT and walking groups after intervention (p < 0.01), but no significant differences between the two groups.

Conclusion

We conclude that KOAPT exhibited potential as an intervention to improve symptoms of KOA possibly through a mechanism of normalising mechanical pressure in the knee; however, optimisation of the method, longer-term intervention and a large sample randomized-single blind clinical trial with a minimal 524 cases are needed to demonstrate whether there is any superior benefit over other exercises.

The translational potential of this article

The research aimed to investigate the effect of an ancient leg-swinging exercise on knee osteoarthritis. A minipig animal model was used to establish the potential mechanism underlying the exercise of knee osteoarthritis pendulum therapy, followed by a randomised, single-blind feasibility clinical trial in comparison with a commonly-practised walking exercise regimen. Based on the results of the feasibility trial, a large sample clinical trial is proposed for future research, in order to develop an effective exercise therapy for KOA.

Clinical outcomes following tibiotalocalcaneal arthrodesis with intramedullary nailing combined with partial fibulectomy and onlay bone graft

INTRODUCTION

Although intramedullary nailing is a popular method for tibiotalocalcaneal arthrodesis, nonunion is one of the most commonly reported complications. This study aimed to evaluate the fusion rate, improvement in functional outcomes, and occurrence of complications in tibiotalocalcaneal arthrodesis using retrograde intramedullary nailing with partial fibulectomy and onlay bone graft technique.

MATERIALS AND METHODS

Twenty-six consecutive patients using the proposed technique were retrospectively reviewed. For radiographic outcomes, the union rate, alignment, and any related complications were assessed. Functional outcomes were evaluated using the American Orthopedic Foot and Ankle Society hindfoot scale, Foot and Ankle Outcome Score, and visual analog scale, preoperatively and at the final follow-up.

RESULTS

The mean follow-up period was 38.2 months. The tibiotalar joint achieved complete union in 80.8% at six months postoperatively, while all the cases achieved complete union at 12 months postoperatively. However, the subtalar joint achieved complete union in 26.9% at six months postoperatively, which gradually increased to 73.1% at 12 months postoperatively, and 80.8% at the final follow-up without revision surgery. A subgroup analysis showed there was a trend of higher subtalar fusion rate when an additional screw for the subtalar joint fixation was placed (86.7% vs. 54.5%). The functional outcomes significantly improved at the final follow-up. A few minor complications occurred, including surgical site infection, irritational symptoms, and metal failure; however, they eventually resolved.

CONCLUSIONS

Our technique of tibiotalocalcaneal arthrodesis with partial fibulectomy and onlay bone grafting could be a good option where both the tibiotalar and subtalar joints need to be fused.

A bone to pick-cellular and molecular mechanisms of bone pain in sickle cell disease

The bone is one of the most commonly affected organs in sickle cell disease (SCD). Repeated ischemia, oxidative stress and inflammation within the bone is largely responsible for promoting bone pain. As more individuals with SCD survive into adulthood, they are likely to experience a synergistic impact of both aging and SCD on their bone health. As bone health deteriorates, bone pain will likely exacerbate. Recent mechanistic and observational studies emphasize an intricate relationship between bone remodeling and the peripheral nervous system. Under pathological conditions, abnormal bone remodeling plays a key role in the propagation of bone pain. In this review, we first summarize mechanisms and burden of select bone complications in SCD. We then discuss processes that contribute to pathological bone pain that have been described in both SCD as well as non-sickle cell animal models. We emphasize the role of bone-nervous system interactions and pitfalls when designing new therapies especially for the sickle cell population. Lastly, we also discuss future basic and translational research in addressing questions about the complex role of stress erythropoiesis and inflammation in the development of SCD bone complications, which may lead to promising therapies and reduce morbidity in this vulnerable population.

Value of Edema-like Marrow Signal Intensity in Diagnosis of Joint Pain: Radiologists' Perspective

Musculoskeletal pain is a significant contributor to disability. The mechanism and target of the treatment should be optimized by imaging, but currently no accepted gold standard exists to image pain. In addition to end-organ pathology, other mediators also contribute to nociception, such as angiogenesis, axonal extension, immunologic modulation, and central sensitization. Recent research indicates that local inflammation is a significant contributor to pain in the extremities; therefore, we focus here on edema-like marrow signal intensity (ELMSI). We examine both the relevance of ELMSI for pain and novel imaging techniques.

Case Report and Literature Review: Bisphosphonate, Sirolimus, and Atenolol Treatment in a 4-Year-Old Child Diagnosed with Gorham-Stout Disease

We report a 4-year-old with Gorham-Stout disease (GSD) who was treated with a combination of bisphosphonate, sirolimus, and atenolol. A previously healthy 4-year-old girl presented with back pain after falling on her back 2 months prior. Thoracolumbar spine X-ray revealed diffuse compression spinal fractures in T9-L2. Magnetic resonance imaging (MRI) confirmed multiple compression fractures at T9-L5 and revealed a paraspinal mass along the T1-L1 level. Based on clinical, radiological, and histopathological findings, Gorham-Stout disease was diagnosed. Treatment with sirolimus (0.5 mg twice daily, 1.6 mg/m2) was initiated and intravenous bisphosphonate (pamidronate, 1 mg/kg for 3 days, total 3 mg/kg every 4 months) was added for back pain; she had immediate improvement in back pain. After 9 months with this treatment, she had a mild increase in paraspinal lymphangiomatosis and aggravation in T9-L5 compression fractures; atenolol was administered. The patient underwent 11 months of combination treatment with bisphosphonate, sirolimus, and atenolol, and MRI showed mild degree of reduction in the paraspinal lesions at L1-L5. The patient is currently in stable condition with no back pain or side effects. The triple combination treatment with bisphosphonate, sirolimus, and atenolol may be helpful in stabilizing the disease course of GSD.

A case of disappearing amyloid on technetium pyrophosphate scan

Technetium-99mm pyrophosphate (Tc-PYP) scintigraphy is a highly accurate non-invasive method for the diagnosis of transthyretin (ATTR) cardiac amyloidosis. Prognosis for this disease is improved following treatment with the transthyretin (TTR) stabilizer tafamidis. Although tafamidis slows disease progression, its effects on myocardial amyloid and Tc-PYP uptake remain unclear. We present a patient with ATTR cardiac amyloidosis who had a strongly positive initial Tc-PYP scan, with a dramatic decrease in Tc-PYP uptake on repeat scan after 3 years of tafamidis treatment. However, myocardial biopsy showed persistent diffuse amyloid deposits. This case highlights the need for further studies regarding the utility of serial Tc-PYP scans in monitoring the progress of ATTR cardiomyopathy.

Quadriceps Strength, Postural Stability, and Pain Mediation in Bilateral Knee Osteoarthritis: A Comparative Analysis with Healthy Controls

Bilateral knee osteoarthritis (OA) poses significant challenges to individuals' functional abilities, including quadriceps strength, postural stability, and pain perception. Understanding the complex relationships among these factors is crucial for enhancing knee OA management strategies. The primary objective of this research is to evaluate and draw comparisons between the strength of the quadriceps and the level of postural stability in two distinct groups: individuals afflicted with bilateral knee OA and those who are healthy. Furthermore, the study seeks to examine the potential correlation between the strength of the quadriceps and the level of postural stability in individuals with knee OA. In addition to this, an investigation into the potential mediating effect of pain on the relationship between these physiological factors will also be conducted. A total of 95 participants with bilateral knee OA and 95 healthy controls were recruited. Quadriceps strength was assessed using dynamometry and postural stability was evaluated through anterior-posterior and medial-lateral sway measurements along with the ellipse area using a force plate. Pain levels were measured using the Visual Analog Scale (VAS). Mediation analysis was employed to explore the role of pain in mediating the relationship between quadriceps strength and postural stability. Statistical analyses included t-tests, Pearson correlation coefficients, and mediation analysis. Knee OA participants exhibited significantly lower quadriceps strength (1.08 Nm/kg ± 0.54) compared to controls (1.54 Nm/kg ± 0.57, p < 0.001). They also demonstrated compromised postural stability with increased anterior-posterior sway (9.86 mm ± 3.017 vs. 2.98 mm ± 1.12, p < 0.001), medial-lateral sway (7.87 mm ± 2.23 vs. 3.12 mm ± 1.34, p < 0.001), and larger ellipse area (935.75 mm2 ± 172.56 vs. 436.19 mm2 ± 135.48, p < 0.001). Negative correlations were observed between quadriceps strength and postural stability variables (r = from -0.43 to -0.51, p < 0.001). Pain significantly mediated the relationship between quadriceps strength and postural stability variables (p < 0.05). This study highlights the associations between quadriceps strength, postural stability, and pain mediation in individuals with bilateral knee OA. Our findings emphasize the need for targeted interventions addressing quadriceps weakness and compromised postural stability. Additionally, the mediation effect of pain underscores the complexity of these relationships, offering insights for more effective management strategies.

Ion channels in cancer-induced bone pain: from molecular mechanisms to clinical applications

Cancer-induced bone pain (CIBP) caused by bone metastasis is one of the most prevalent diseases, and current treatments rely primarily on opioids, which have significant side effects. However, recent developments in pharmaceutical science have identified several new mechanisms for CIBP, including the targeted modification of certain ion channels and receptors. Ion channels are transmembrane proteins, which are situated on biological cell membranes, which facilitate passive transport of inorganic ions across membranes. They are involved in various physiological processes, including transmission of pain signals in the nervous system. In recent years, there has been an increasing interest in the role of ion channels in chronic pain, including CIBP. Therefore, in this review, we summarize the current literature on ion channels, related receptors, and drugs and explore the mechanism of CIBP. Targeting ion channels and regulating their activity might be key to treating pain associated with bone cancer and offer new treatment avenues.

The Edmonton Classification System for Cancer Pain in Patients with Bone Metastasis: a descriptive cohort study

PURPOSE

We describe the prevalence of the Edmonton Classification System for Cancer Pain (ECS-CP) features in patients with bone metastasis and cancer-induced bone pain (CIBP) and the relationship between ECS-CP features, pain intensity, and opioid consumption.

METHODS

We assessed ECS-CP features and recoded pain mechanisms and opioid use in adult patients with bone metastasis. Validated measures were used to assess pain intensity, incident pain, psychological distress, addictive behavior, and cognition.

RESULTS

Among 147 eligible patients, 95.2% completed the assessment. Mean participant age was 73.2 years, the majority female (52.1%) with breast cancer occurring most commonly (25.7%). One or more ECS-CP features were present in 96.4% and CIBP in 75.7% of patients. The median average and worst pain scores were 3 and 6, respectively. Neuropathic pain was the most prevalent pain mechanism (45.0%) and was associated with breakthrough pain frequency (p=0.014). Three-quarters had incident pain, which was strongly associated with a higher average and worst pain scores (3.5 and 7, p<0.001 for both), background oral morphine equivalent daily dose (26.7mg, p=0.005), and frequency of daily breakthrough analgesia (1.7 doses/day, p=0.007). Psychological distress (n=90, 64.3%) was associated with a significantly higher average pain score (4, p=0.009) and a slightly higher worst pain score (7, p=0.054). Addictive behaviour and cognitive dysfunction were relatively uncommon (18.6% and 12.9%, respectively).

CONCLUSION

There is a need to promote standardized assessment and classification of pain syndromes such as CIBP. The ECS-CP may allow us to consider CIBP in a systematic manner and develop personalized pain interventions appropriate to the pain profile.

TRIAL REGISTRATION

Retrospectively registered in ANZCTR ACTRN12622000853741 (16/06/2022).

Pharmacological Interventions Targeting Pain in Fibrous Dysplasia/McCune-Albright Syndrome

Fibrous dysplasia (FD) is a rare, non-inherited bone disease occurring following a somatic gain-of-function R201 missense mutation of the guanine-nucleotide binding protein alpha subunit stimulating activity polypeptide 1 (GNAS) gene. The spectrum of the disease ranges from a single FD lesion to a combination with extraskeletal features; an amalgamation with café-au-lait skin hyperpigmentation, precocious puberty, and other endocrinopathies defines McCune-Albright Syndrome (MAS). Pain in FD/MAS represents one of the most prominent aspects of the disease and one of the most challenging to treat-an outcome driven by (i) the heterogeneous nature of FD/MAS, (ii) the variable presentation of pain phenotypes (i.e., craniofacial vs. musculoskeletal pain), (iii) a lack of studies probing pain mechanisms, and (iv) a lack of rigorously validated analgesic strategies in FD/MAS. At present, a range of pharmacotherapies are prescribed to patients with FD/MAS to mitigate skeletal disease activity, as well as pain. We analyze evidence guiding the current use of bisphosphonates, denosumab, and other therapies in FD/MAS, and also discuss the potential underlying pharmacological mechanisms by which pain relief may be achieved. Furthermore, we highlight the range of presentation of pain in individual cases of FD/MAS to further describe the difficulties associated with employing effective pain treatment in FD/MAS. Potential next steps toward identifying and validating effective pain treatments in FD/MAS are discussed, such as employing randomized control trials and probing new pain pathways in this rare bone disease.

Genetic susceptibility to autoimmunity-Current status and challenges

Autoimmune diseases (ADs) often arise from a combination of genetic and environmental triggers that disrupt the immune system's capability to properly tolerate body self-antigens. Familial studies provided the earliest insights into the risk loci of such diseases, while genome-wide association studies (GWAS) significantly broadened the horizons. A drug targeting a prominent pathological pathway can be applied to multiple indications sharing overlapping mechanisms. Advances in genomic technologies used in genetic studies provide critical insights into future research on gene-environment interactions in autoimmunity. This Review summarizes the history and recent advances in the understanding of genetic susceptibility to ADs and related immune disorders, including coronavirus disease 2019 (COVID-19), and their indications for the development of diagnostic or prognostic markers for translational applications.