Frozen shoulder. An overview of pathology and biology with hopes to novel drug therapies

Frozen shoulder (FS) is a common disorder characterized by spontaneous onset of shoulder pain accompanied by progressive loss of range-of-motions. The cause of FS is still unclear, and radical therapy has not been established. With the final aim of preventing or curing FS at an earlier stage, we reviewed the pathological and biological features of this disease. Many studies indicate that the main pathology of FS is inflammation initially and fibrosis later. There are inflammatory cytokines, immune cells, fibrotic growth factors, and type-III collagen in the synovium and the joint capsule. The immune cell landscape switches from the macrophages to T cells. Activated fibroblasts seem to regulate the inflammatory and fibrotic processes. The imbalance between matrix metalloproteinases and tissue inhibitors of metalloproteases might promote fibrosis. Additionally, advanced glycation end-products are noted in the FS synovium. Diabetes mellitus and hypothyroidism are closely related to the development of FS. In terms of nonsurgical treatment, oral or intra-articular glucocorticoids are the only drugs that provide early benefit. Some other anti-inflammatory or antifibrotic drugs may potentially control the FS, but have not been proven effective in the clinical setting. Future studies should be targeted to develop steroid-sparing agents that inhibit biological events in FS.

A single cell atlas of frozen shoulder capsule identifies features associated with inflammatory fibrosis resolution

Frozen shoulder is a spontaneously self-resolving chronic inflammatory fibrotic human disease, which distinguishes the condition from most fibrotic diseases that are progressive and irreversible. Using single-cell analysis, we identify pro-inflammatory MERTKlowCD48+ macrophages and MERTK + LYVE1 + MRC1+ macrophages enriched for negative regulators of inflammation which co-exist in frozen shoulder capsule tissues. Micro-cultures of patient-derived cells identify integrin-mediated cell-matrix interactions between MERTK+ macrophages and pro-resolving DKK3+ and POSTN+ fibroblasts, suggesting that matrix remodelling plays a role in frozen shoulder resolution. Cross-tissue analysis reveals a shared gene expression cassette between shoulder capsule MERTK+ macrophages and a respective population enriched in synovial tissues of rheumatoid arthritis patients in disease remission, supporting the concept that MERTK+ macrophages mediate resolution of inflammation and fibrosis. Single-cell transcriptomic profiling and spatial analysis of human foetal shoulder tissues identify MERTK + LYVE1 + MRC1+ macrophages and DKK3+ and POSTN+ fibroblast populations analogous to those in frozen shoulder, suggesting that the template to resolve fibrosis is established during shoulder development. Crosstalk between MerTK+ macrophages and pro-resolving DKK3+ and POSTN+ fibroblasts could facilitate resolution of frozen shoulder, providing a basis for potential therapeutic resolution of persistent fibrotic diseases.

Three-dimensional, in-vitro approaches for modelling soft-tissue joint diseases

Diseases affecting the soft tissues of the joint represent a considerable global health burden, causing pain and disability and increasing the likelihood of developing metabolic comorbidities. Current approaches to investigating the cellular basis of joint diseases, including osteoarthritis, rheumatoid arthritis, tendinopathy, and arthrofibrosis, involve well phenotyped human tissues, animal disease models, and in-vitro tissue culture models. Inherent challenges in preclinical drug discovery have driven the development of state-of-the-art, in-vitro human tissue models to rapidly advance therapeutic target discovery. The clinical potential of such models has been substantiated through successful recapitulation of the pathobiology of cancers, generating accurate predictions of patient responses to therapeutics and providing a basis for equivalent musculoskeletal models. In this Review, we discuss the requirement to develop physiologically relevant three-dimensional (3D) culture systems that could advance understanding of the cellular and molecular basis of diseases that affect the soft tissues of the joint. We discuss the practicalities and challenges associated with modelling the complex extracellular matrix of joint tissues-including cartilage, synovium, tendon, and ligament-highlighting the importance of considering the joint as a whole organ to encompass crosstalk across tissues and between diverse cell types. The design of bespoke in-vitro models for soft-tissue joint diseases has the potential to inform functional studies of the cellular and molecular mechanisms underlying disease onset, progression, and resolution. Use of these models could inform precision therapeutic targeting and advance the field towards personalised medicine for patients with common musculoskeletal diseases.

Salvianolic acid B attenuates inflammation and prevent pathologic fibrosis by inhibiting CD36-mediated activation of the PI3K-Akt signaling pathway in frozen shoulder

Frozen shoulder (FS) is characterized by pain and limited range of motion (ROM). Inflammation and fibrosis are accepted as main pathologic processes associated with the development of FS. However, the intrinsic mechanisms underlying pathologic fibrosis remain unclear. We aimed to elucidate the key molecules involved in pathologic fibrosis and explore new therapeutic targets for FS. Synovial fibroblasts isolated from patient biopsies were identified using immunofluorescence. Western blotting, RT-qPCR, cell adhesion tests, and would-healing assays were used to evaluate the fibrosis-related functions of synovial fibroblasts. Elevated cluster of differentiation 36 (CD36) expression was detected in FS using Western blotting and immunohistochemistry. Salvianolic acid b (SaB) inhibited CD36, blocking synovial fibroblast-induced inflammation and fibrosis. Our RNA-seq data showed that knocking down CD36 dramatically impaired the capacity of synovial fibroblasts for cell adhesion and that the PI3K-Akt signaling pathway may be crucial to the fibrotic process of FS. By up-regulating CD36 and inhibiting the phosphorylation of Akt, we demonstrated that CD36 promotes pathologic fibrosis by activating the PI3k-Akt pathway. Finally, rats treated with SaB had improved ROM and less collagen fiber deposition than the FS model group. Conclusion: SaB attenuates inflammation and inhibited the CD36-mediated activation of the PI3K-Akt signaling pathway to block pathologic fibrosis of FS in vitro and in vivo models.

Frozen shoulder

Frozen shoulder is a common debilitating disorder characterized by shoulder pain and progressive loss of shoulder movement. Frozen shoulder is frequently associated with other systemic conditions or occurs following periods of immobilization, and has a protracted clinical course, which can be frustrating for patients as well as health-care professionals. Frozen shoulder is characterized by fibroproliferative tissue fibrosis, whereby fibroblasts, producing predominantly type I and type III collagen, transform into myofibroblasts (a smooth muscle phenotype), which is accompanied by inflammation, neoangiogenesis and neoinnervation, resulting in shoulder capsular fibrotic contractures and the associated clinical stiffness. Diagnosis is heavily based on physical examination and can be difficult depending on the stage of disease or if concomitant shoulder pathology is present. Management consists of physiotherapy, therapeutic modalities such as steroid injections, anti-inflammatory medications, hydrodilation and surgical interventions; however, their effectiveness remains unclear. Facilitating translational science should aid in development of novel therapies to improve outcomes among individuals with this debilitating condition.

Randomized controlled trial of suprascapular nerve blocks for subacute adhesive capsulitis

BACKGROUND

Shoulder pain and loss of function remain a therapeutic challenge in adhesive capsulitis. Suprascapular nerve blocks, a common treatment in adhesive capsulitis, are considered a safe and effective method for the resolution of pain and restoration of shoulder range of motion (ROM). To our knowledge, no data are available on the use of suprascapular nerve blocks in adhesive capsulitis in the subacute phase.

AIM

The aim of this study was to compare the efficacy of ultrasound-guided suprascapular nerve blocks versus saline injections for treating adhesive capsulitis in the subacute phase.

DESIGN

Randomized double-blinded controlled trial; level of evidence 2.

SETTING

Out-patient consultation of Physical and Rehabilitation Medicine in a general hospital.

POPULATION

Thirty-five patients with subacute adhesive capsulitis.

METHODS

Patients were randomly allocated to receive either 3 successive (1-week interval) ultrasound-guided suprascapular nerve blocks with ropivacaine 5 mL 2 mg/mL (intervention group) or ultrasound-guided injections of 5 mL sterile saline solution (NaCl 0.9%) (control group), at the floor of the suprascapular fossa. Primary outcome was shoulder function assessed by the Constant-Murley Score. Secondary outcomes were shoulder ROM and shoulder pain intensity. Assessments were performed before each injection and 4 weeks after the last injection.

RESULTS

A significant increase of Constant-Murley Score (P<0.001), increase of shoulder ROM (all directions: P<0.011) and decrease of pain (P<0.001), were observed over time in both study groups. However, no significant differences were observed between the intervention and the control group.

CONCLUSIONS

Three successive suprascapular nerve blocks did not provide a better outcome than saline injections on shoulder function, ROM, and pain in subacute adhesive capsulitis. These negative findings warrant some considerations on the natural history of adhesive capsulitis, as well as timing, type, and placebo effects of injections.

CLINICAL REHABILITATION IMPACT

The current place of suprascapular nerve blocks in the treatment strategy of adhesive capsulitis needs to be rediscussed.

Translational targeting of inflammation and fibrosis in frozen shoulder: Molecular dissection of the T cell/IL-17A axis

Frozen shoulder is a common fibroproliferative disease characterized by the insidious onset of pain and restricted range of shoulder movement with a significant socioeconomic impact. The pathophysiological mechanisms responsible for chronic inflammation and matrix remodeling in this prevalent fibrotic disorder remain unclear; however, increasing evidence implicates dysregulated immunobiology. IL-17A is a key cytokine associated with inflammation and tissue remodeling in numerous musculoskeletal diseases, and thus, we sought to determine the role of IL-17A in the immunopathogenesis of frozen shoulder. We demonstrate an immune cell landscape that switches from a predominantly macrophage population in nondiseased tissue to a T cell-rich environment in disease. Furthermore, we observed a subpopulation of IL-17A-producing T cells capable of inducing profibrotic and inflammatory responses in diseased fibroblasts through enhanced expression of the signaling receptor IL-17RA, rendering diseased cells more sensitive to IL-17A. We further established that the effects of IL-17A on diseased fibroblasts was TRAF-6/NF-κB dependent and could be inhibited by treatment with an IKKβ inhibitor or anti-IL-17A antibody. Accordingly, targeting of the IL-17A pathway may provide future therapeutic approaches to the management of this common, debilitating disease.

Surgical treatments compared with early structured physiotherapy in secondary care for adults with primary frozen shoulder: the UK FROST three-arm RCT

BACKGROUND

Frozen shoulder causes pain and stiffness. It affects around 10% of people in their fifties and is slightly more common in women. Costly and invasive surgical interventions are used, without high-quality evidence that these are effective.

OBJECTIVES

To compare the clinical effectiveness and cost-effectiveness of three treatments in secondary care for adults with frozen shoulder; to qualitatively explore the acceptability of these treatments to patients and health-care professionals; and to update a systematic review to explore the trial findings in the context of existing evidence for the three treatments.

DESIGN

This was a pragmatic, parallel-group, multicentre, open-label, three-arm, randomised superiority trial with unequal allocation (2 : 2 : 1). An economic evaluation and a nested qualitative study were also carried out.

SETTING

The orthopaedic departments of 35 hospitals across the UK were recruited from April 2015, with final follow-up in December 2018.

PARTICIPANTS

Participants were adults (aged ≥ 18 years) with unilateral frozen shoulder, characterised by restriction of passive external rotation in the affected shoulder to < 50% of the opposite shoulder, and with plain radiographs excluding other pathology.

INTERVENTIONS

The inventions were early structured physiotherapy with a steroid injection, manipulation under anaesthesia with a steroid injection and arthroscopic capsular release followed by manipulation. Both of the surgical interventions were followed with post-procedural physiotherapy.

MAIN OUTCOME MEASURES

The primary outcome and end point was the Oxford Shoulder Score at 12 months post randomisation. A difference of 5 points between early structured physiotherapy and manipulation under anaesthesia or arthroscopic capsular release or of 4 points between manipulation under anaesthesia and arthroscopic capsular release was judged clinically important.

RESULTS

The mean age of the 503 participants was 54 years; 319 were female (63%) and 150 had diabetes (30%). The primary analyses comprised 473 participants (94%). At the primary end point of 12 months, participants randomised to arthroscopic capsular release had, on average, a statistically significantly higher (better) Oxford Shoulder Score than those randomised to manipulation under anaesthesia (2.01 points, 95% confidence interval 0.10 to 3.91 points; p = 0.04) or early structured physiotherapy (3.06 points, 95% confidence interval 0.71 to 5.41 points; p = 0.01). Manipulation under anaesthesia did not result in statistically significantly better Oxford Shoulder Score than early structured physiotherapy (1.05 points, 95% confidence interval -1.28 to 3.39 points; p = 0.38). No differences were deemed of clinical importance. Serious adverse events were rare but occurred in participants randomised to surgery (arthroscopic capsular release,n = 8; manipulation under anaesthesia,n = 2). There was, however, one serious adverse event in a participant who received non-trial physiotherapy. The base-case economic analysis showed that manipulation under anaesthesia was more expensive than early structured physiotherapy, with slightly better utilities. The incremental cost-effectiveness ratio for manipulation under anaesthesia was £6984 per additional quality-adjusted life-year, and this intervention was probably 86% cost-effective at the threshold of £20,000 per quality-adjusted life-year. Arthroscopic capsular release was more costly than early structured physiotherapy and manipulation under anaesthesia, with no statistically significant benefit in utilities. Participants in the qualitative study wanted early medical help and a quicker pathway to resolve their shoulder problem. Nine studies were identified from the updated systematic review, including UK FROST, of which only two could be pooled, and found that arthroscopic capsular release was more effective than physiotherapy in the long-term shoulder functioning of patients, but not to the clinically important magnitude used in UK FROST.

LIMITATIONS

Implementing physiotherapy to the trial standard in clinical practice might prove challenging but could avoid theatre use and post-procedural physiotherapy. There are potential confounding effects of waiting times in the trial.

CONCLUSIONS

None of the three interventions was clearly superior. Early structured physiotherapy with a steroid injection is an accessible and low-cost option. Manipulation under anaesthesia is the most cost-effective option. Arthroscopic capsular release carries higher risks and higher costs.

FUTURE WORK

Evaluation in a randomised controlled trial is recommended to address the increasing popularity of hydrodilatation despite the paucity of high-quality evidence.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN48804508.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 24, No. 71. See the NIHR Journals Library website for further project information.

Transcriptomic analysis of adhesive capsulitis of the shoulder

Adhesive capsulitis (AC) is a disabling condition of the shoulder joint affecting 2 to 5% of the general population. Our understanding of the molecular mechanisms is limited. The present study aimed to determine potential biomarkers of AC through transcriptomic analysis. This multi-centre study investigated patients undergoing arthroscopic capsulotomy surgery for resistant AC compared to those undergoing arthroscopic stabilization surgery for glenohumeral instability (control). Tissue samples were harvested from the anterior capsule during surgery. Total RNA was extracted and RNA-sequencing-based transcriptomics were performed. A number of genes deemed differentially expressed in RNA-sequencing analysis were validated using real-time reverse transcription polymerase chain reaction (RT-PCR). Baseline characteristics of the AC group (n = 22) were; mean age 52.7 years (SD: 10.2), 73% female, and Oxford Shoulder Score 19.6 (SD: 8.0), compared with the control group (n = 26), average age 23.9 years (SD: 5.2), 15% female, and Oxford Shoulder Score 39.0 (SD: 7.4). Transcriptomic analysis with false discovery rate correction and log₂ fold change cut-off of ±1.5 revealed 545 differentially expressed genes in AC relative to control. Bioinformatic analyses were carried out to identify biological processes and pathways enriched in this dataset. Real-time RT-PCR using two different normalization processes confirmed increased expression of matrix metallopeptidase 13 (MMP13) and platelet-derived growth factor subunit B (PDGFB), in patients with AC, while tumor necrosis factor α (TNFA) expression was reduced. These findings provide a comprehensive assessment of transcriptional changes associated with AC that give insights into the aetiology of the disease and provides a resource for molecular targets to better diagnose and treat this condition.

Intra-Articular versus Subacromial Corticosteroid Injection for the Treatment of Adhesive Capsulitis: A Meta-Analysis and Systematic Review

Background

Adhesive capsulitis is one of the most well-known causes of pain and stiffness of the shoulder. Corticosteroid injections have been used for many years. However, it is still controversial where corticosteroid should be injected, whether subacromial or intra-articular.

Objective

The objective of this meta-analysis was to compare the effects of intra-articular (IA) and subacromial (SA) corticosteroid injections for the treatment of adhesive capsulitis.

Materials and Methods

Four foreign databases and two Chinese databases were searched for RCTs and quasi-RCTs involving the comparison of IA and SA corticosteroid injection for the treatment of adhesive capsulitis. The Cochrane risk of bias tool and PEDro score were used to evaluate the quality of the studies. The primary clinical outcomes including VAS, Constant score, ASES score, and ROM were collected. The secondary outcome of corticosteroid-related adverse reactions was also compared between the two groups. The results were evaluated and compared at five time points. Subgroup analyses were performed to further explore the differences between groups.

Results

Eight RCTs and one quasi-RCT, involving 512 participants, were identified and included in this meta-analysis. All studies were of low risk of bias and medium-high quality with the PEDro score ≥5 points. The pooled effect showed that there was no significant difference in the primary outcomes between IA injection and SA injection, with an exception of VAS at 2-3 weeks (P=0.02) and ROM of internal rotation at 8–12 weeks (P=0.02). According to the results of subgroup analyses, the differences of VAS and ROM of internal rotation did not last beyond the 2-3-week time period. Additionally, SA injection had the advantage of avoiding adverse reactions from the corticosteroid, especially in avoiding a large fluctuation of serum blood glucose levels.

Conclusions

When corticosteroid injection is used to treat adhesive capsulitis, both injection sites can be selected. However, due to the scarcity of related studies, more rigorous trials are needed to confirm the current findings.