The molecular pathophysiology of subacromial bursitis in rotator cuff disease

The subacromial bursa modulates tendon healing after rotator cuff injury in rats

Rotator cuff injuries result in more than 500,000 surgeries annually in the United States, many of which fail. These surgeries typically involve repair of the injured tendon and removal of the subacromial bursa, a synovial-like tissue that sits between the rotator cuff and the acromion. The subacromial bursa has been implicated in rotator cuff pathogenesis and healing. Using proteomic profiling of bursa samples from nine patients with rotator cuff injury, we show that the bursa responds to injury in the underlying tendon. In a rat model of supraspinatus tenotomy, we evaluated the bursa's effect on the injured supraspinatus tendon, the uninjured infraspinatus tendon, and the underlying humeral head. The bursa protected the intact infraspinatus tendon adjacent to the injured supraspinatus tendon by maintaining its mechanical properties and protected the underlying humeral head by maintaining bone morphometry. The bursa promoted an inflammatory response in injured rat tendon, initiating expression of genes associated with wound healing, including Cox2 and Il6. These results were confirmed in rat bursa organ cultures. To evaluate the potential of the bursa as a therapeutic target, polymer microspheres loaded with dexamethasone were delivered to the intact bursae of rats after tenotomy. Dexamethasone released from the bursa reduced Il1b expression in injured rat supraspinatus tendon, suggesting that the bursa could be used for drug delivery to reduce inflammation in the healing tendon. Our findings indicate that the subacromial bursa contributes to healing in underlying tissues of the shoulder joint, suggesting that its removal during rotator cuff surgery should be reconsidered.

Histological and biochemical changes in a rat rotator cuff tear model with or without the subacromial bursa

The subacromial bursa (SAB) plays an important role in the tendon healing process. Based on previous reports, co-culture of the rotator cuff (RC) and SAB have been shown to increase the tendon-related gene expressions, inflammatory cytokines, and tensile strength. However, the nature of the specific biochemical alterations during the inflammatory and repair phases of tendon healing with or without the SAB remain unknown. Using a full-thickness RC tear rat model, we determined how the presence or absence of the SAB alters the histological characteristics and gene expressions. After 3 and 6 weeks, tissues were collected for histological and real-time quantitative polymerase chain reaction (RT-qPCR) evaluations. Results showed greater cell density at 3 weeks, neovascularization and tendon thickening at 6 weeks with SAB preservation. Immunostaining revealed significant increases in type 3 collagen (COL3) expression at 6 weeks with SAB preservation. The RT-qPCR results showed that SAB preservation induced significant increases in the expression of scleraxis, matrix metalloproteinase-13 (MMP-13), interleukin-1β (IL-1β), and inducible nitric oxide synthase (iNOS) at 3 weeks and significant increases in COL3, IL-10, and arginase-1 (Arg-1) at 6 weeks. An RC tear undergoes more appropriate inflammatory and repair phases during the tendon healing process when the SAB is retained.

Clinical Implication of Glenohumeral and Subacromial Synovitis in Rotator Cuff Tears

Background

Synovitis of the glenohumeral (GH) joint and the subacromial (SA) space is commonly observed during arthroscopic rotator cuff surgery.

Purpose

To investigate the distribution, severity, and clinical implications of synovitis in the GH joint and SA space in patients with a full-thickness rotator cuff tear (RCT).

Study Design

Case series; Level of evidence, 4.

Methods

Data were retrospectively collected from 207 patients with a full-thickness RCT who underwent arthroscopic repair. Preoperative parameters used in the clinical assessment included pain, range of motion (ROM), muscle strength, and functional scores. Macroscopic assessment of synovitis was performed intraoperatively in the 3 regions of interest (ROIs) of the GH joint and 4 ROIS of the SA space using an evaluation system. The distribution and severity of synovitis and the association between synovitis and clinical assessment were evaluated.

Results

Synovitis was more severe in the GH joint than in the SA space (P < .001). Synovitis in the posterior GH joint and the lateral SA space, where most of the rotator cuff was located, was the most severe area among the ROIs of the GH joint and the SA space, respectively (P < .05). All types of pain, except for pain at rest, were associated with synovitis in the posterior GH joint (P < .05). All ROM measures were associated with synovitis in the posterior and inferior GH joint (|r| > 0.20; P < .05 for both). The strength of the supraspinatus and the infraspinatus was associated with synovitis in the posterior GH joint (P < .05). Shoulder function was associated with synovitis in the posterior and inferior GH joint and more in the posterior GH joint (P < .05 for both). Synovitis in the SA space was not associated with any of the clinical parameters.

Conclusion

Synovitis in the posterior GH joint was the most severe form of synovitis in the GH joint in patients with a full-thickness RCT. Synovitis in the posterior GH joint was closely associated with increased pain and decreased ROM, muscle strength, and functional score. Synovitis in the SA space was milder and not associated with any clinical parameters.

The association of metabolic syndrome with rotator cuff tendinopathy: a two-sample Mendelian randomization study

BACKGROUND

Observational research reported the underlying correlation of metabolic syndrome (MetS) and its components with rotator cuff tendinopathy (RCT), but their causality remained unclear. This study aimed to investigate whether genetically predicted MetS was related to the risk of RCT.

METHODS

Both univariable and multivariable Mendelian randomization (MR) analysis was applied using summary-level data from the most comprehensive genome-wide association studies to estimate the associations of MetS and its component with RCT, with the inverse variance weighted (IVW) as the primary method, and the method of Causal Analysis Using Summary Effect Estimates (CAUSE) as a supplement for false positives detection. The mediation analysis was furtherly used for the assessment of direct and indirect effects.

RESULTS

Univariable analysis revealed that genetically predicted MetS (OR: 1.0793; 95% CI 1.0311 to 1.1297), body mass index (BMI) (OR 1.2239; 95% CI 1.1357 to 1.3189), and waist circumference (WAC) (OR 1.3177; 95% CI 1.2015 to 1.4451) had a significant positive association with the risk of RCT. Triglycerides and systolic blood pressure were suggestively associated with RCT risk. These associations were also identified by CAUSE. There was independent causality of BMI (OR: 1.1806; 95% CI 1.0788 to 1.2920) and WAC (OR 1.3716; 95% CI 1.2076 to 1.5580) on RCT after adjustment for confounders. No mediator was found in the causal associations.

CONCLUSION

Our study revealed the genetic causality of MetS and its components, especially BMI and WAC, with RCT risk. Early prevention and diagnosis of excess central adiposity contributing to MetS are significant in the RCT risk management.

Metformin increases the expression of proinflammatory cytokines and inhibits supraspinatus fatty infiltration

BACKGROUND

After a rotator cuff (RC) tendon tear, the supraspinatus (SS) inflammatory response induces fatty infiltration (FI). Metformin has the effect of regulating the initial inflammatory response of atrophic muscles. Therefore, this study aimed to investigate the effect of metformin use on modulating the expression of proinflammatory cytokines and SS FI in an acute RC tear rat model.

METHODS

This study used 26 male Sprague-Dawley rats. Animals were randomly divided into two groups: The metformin group received metformin for 5 days after cutting the RC tendon, and the control group was administered only with saline after cutting the tendon. Metformin 50 mg/kg was intraperitoneally injected for 5 days. Three rats in each group were sacrificed 5 days after SS tendon rupture surgery, and 10 rats in each group were sacrificed 14 days after surgery. The SS was sampled 5 days after SS tendon tear surgery, and the expression of proinflammatory cytokines was measured by quantitative reverse-transcription polymerase chain reaction (qRT-PCR). On day 14 after sampling, histological analysis of the SS was performed using hematoxylin and eosin, Masson's trichrome, and picrosirius red staining.

RESULTS

On day 5 of surgery, the expression values of interferon gamma (increased 7.2-fold, P < .01), tumor necrosis factor alpha (increased 13-fold, P < .05), interleukin-1β (increased 4.7-fold, P < .001), and interleukin-6 (increased 4.6-fold, P < .01) increased significantly in the metformin group compared with those in the control group. As a result of Oil Red O staining, SS FI was significantly suppressed in the metformin group compared with that in the control group (metformin group, 305 ± 50.3 µm2, P < .001; control group, 3136 ± 662.8 µm2, P < .001). In addition, the SS volume of the metformin group was not reduced compared with those of the control group, and the morphology and structure of the SS were better preserved.

CONCLUSIONS

The results of this study revealed that metformin can increase the expression of proinflammatory cytokines and suppress SS fat infiltration in delayed sutures.

The subacromial bursa is a key regulator of the rotator cuff and a new therapeutic target for improving repair

Rotator cuff injuries result in over 500,000 surgeries performed annually, an alarmingly high number of which fail. These procedures typically involve repair of the injured tendon and removal of the subacromial bursa. However, recent identification of a resident population of mesenchymal stem cells and inflammatory responsiveness of the bursa to tendinopathy indicate an unexplored biological role of the bursa in the context of rotator cuff disease. Therefore, we aimed to understand the clinical relevance of bursa-tendon crosstalk, characterize the biologic role of the bursa within the shoulder, and test the therapeutic potential for targeting the bursa. Proteomic profiling of patient bursa and tendon samples demonstrated that the bursa is activated by tendon injury. Using a rat to model rotator cuff injury and repair, tenotomy-activated bursa protected the intact tendon adjacent to the injured tendon and maintained the morphology of the underlying bone. The bursa also promoted an early inflammatory response in the injured tendon, initiating key players in wound healing. In vivo results were supported by targeted organ culture studies of the bursa. To examine the potential to therapeutically target the bursa, dexamethasone was delivered to the bursa, prompting a shift in cellular signaling towards resolution of inflammation in the healing tendon. In conclusion, contrary to current clinical practice, the bursa should be retained to the greatest extent possible and provides a new therapeutically target for improving tendon healing outcomes.

One Sentence Summary

The subacromial bursa is activated by rotator cuff injury and regulates the paracrine environment of the shoulder to maintain the properties of the underlying tendon and bone.

The major pain source of rotator cuff-related shoulder pain: A narrative review on current evidence

BACKGROUND

Rotator cuff-related shoulder pain (RCRSP) was proposed to have a complex pain mechanism, but the exact aetiology is still unclear. A recent review summarised the updated research to analyse the traditional concept of shoulder impingement which may not be accurate. Current studies have demonstrated that mechanical factors including a reduction in subacromial space, scapular dyskinesia and different acromial shapes are unlikely directly contributing to RCRSP.

AIMS

Since the precise RCRSP pain mechanism remains unclear, the aim of this narrative review is to discuss possible sources of pain contributing to RCRSP according to the mechanisms-based pain classifications.

RESULTS AND DISCUSSION

Research findings on potential mechanical nociceptive factors of RCRSP are conflicting; investigations of neuropathic and central pain mechanisms of RCRSP are limited and inconclusive. Overall, available evidence has indicated moderate to strong correlations between RCRSP and chemical nociceptive sources of pain.

CONCLUSION

Results from current research may provide new directions for future studies on the aetiology of RCRSP and its clinical management towards a biochemical view instead of the traditional mechanical hypothesis.

Role of immune cell infiltration and small molecule drugs in adhesive capsulitis: Novel exploration based on bioinformatics analyses

Background

Adhesive capsulitis (AC) is a type of arthritis that causes shoulder joint pain, stiffness, and limited mobility. The pathogenesis of AC is still controversial. This study aims to explore the role of immune related factors in the occurrence and development of AC.

Methods

The AC dataset was downloaded from Gene Expression Omnibus (GEO) data repository. Differentially expressed immune-related genes (DEIRGs) were obtained based on R package "DESeq2" and Immport database. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) were performed to explore the functional correlation of DEIRGs. MCC method and Least Absolute Shrinkage and Selection Operator (LASSO) regression were conducted to identify the hub genes. The immune cell infiltration in shoulder joint capsule between AC and control was evaluated by CIBERSORTx, and the relationship between hub genes and infiltrating immune cells was analyzed by Spearman's rank correlation. Finally, potential small molecule drugs for AC were screened by the Connectivity Map database (CMap) and further verified by molecular docking.

Results

A total of 137 DEIRGs and eight significantly different types of infiltrating immune cells (M0 macrophages, M1 macrophages, regulatory T cells, Tfh cells, monocytes, activated NK cells, memory resting CD4+T cells and resting dendritic cells) were screened between AC and control tissues. MMP9, FOS, SOCS3, and EGF were identified as potential targets for AC. MMP9 was negatively correlated with memory resting CD4+T cells and activated NK cells, but positively correlated with M0 macrophages. SOCS3 was positively correlated with M1 macrophages. FOS was positively correlated with M1 macrophages. EGF was positively correlated with monocytes. Additionally, dactolisib (ranked first) was identified as a potential small-molecule drug for the targeted therapy of AC.

Conclusions

This is the first study on immune cell infiltration analysis in AC, and these findings may provide a new idea for the diagnosis and treatment of AC.

The Composition of Adipose-Derived Regenerative Cells Isolated from Lipoaspirate Using a Point of Care System Does Not Depend on the Subject's Individual Age, Sex, Body Mass Index and Ethnicity

Uncultured, unmodified, autologous, adipose-derived regenerative cells (UA-ADRCs) are a safe and effective treatment option for various musculoskeletal pathologies. However, it is unknown whether the composition of the final cell suspension systematically varies with the subject's individual age, sex, body mass index and ethnicity. UA-ADRCs were isolated from lipoaspirate from n = 232 subjects undergoing elective lipoplasty using the Transpose RT system (InGeneron, Inc.; Houston, TX, USA). The UA-ADRCs were assessed for the number of nucleated cells, cell viability and the number of viable nucleated cells per gram of adipose tissue harvested. Cells from n = 37 subjects were further characterized using four-channel flow cytometry. The present study shows, for the first time, that key characteristics of UA-ADRCs can be independent of the subject's age, sex, BMI and ethnicity. This result has important implications for the general applicability of UA-ADRCs in regeneration of musculoskeletal tissue. Future studies must determine whether the independence of key characteristics of UA-ADRCs of the subject's individual age, sex, BMI and ethnicity only applies to the system used in the present study, or also to others of the more than 25 different experimental methods and commercially available systems used to isolate UA-ADRCs from lipoaspirate that have been described in the literature.

RNA-Seq analysis reveals sex-dependent transcriptomic profiles of human subacromial bursa stratified by tear etiology

Rotator cuff tendinopathy, a major cause of shoulder disability, occurs due to trauma or degeneration. Our molecular understanding of traumatic and degenerative tears remains elusive. Here, we probed transcript level differences between traumatic and degenerative tears. Subacromial bursa tissues were collected from patients with traumatic or degenerative tears during arthroscopy (N = 32). Transcripts differentially expressed by tear etiology were detected by RNA-seq. RNA-seq results were validated by real-time quantitative polymerase chain reaction. We identified 334 protein-coding transcripts differentially expressed between traumatic and degenerative tears in females and 167 in males at a fold-change greater than 2. In females, XIRP2, MYL1, MYBPC1, TNNT1, and LMOD2, were highly expressed in traumatic tears whereas TPSD1, CDSN, RCVRN, LTBP4, and PTGS1 were elevated in degen tears. Transcripts elevated in traumatic tears represented muscle cell differentiation and development, and muscle contraction whereas those elevated in degenerative tears represented cell activation and immune response. In males, AZGP1, CNTFR, COL9A1, ZNF98, and EREG were highly elevated in traumatic tears whereas MYL2, HOXD11, SLC6A7, CADM1, and MMP17 were highly expressed in degenerative tears. Transcripts elevated in traumatic tears represented metabolic/catabolic processes, and transmembrane protein transport while processes related to cell cycle were mainly enriched in degenerative tears. Numerous long noncoding RNAs were differentially expressed between traumatic and degenerative tears in both sexes. In summary, this study provides insights into molecular biology of bursa in patients with rotator cuff tendon disease based on tear acuity and novel sex-based transcript differences that could inform clinical decision making in treating patients with traumatic or degenerative shoulder injuries.

Effect of the Critical Shoulder Angle on the Efficacy of Ultrasound-Guided Steroid Injection for Subacromial Bursitis

The critical shoulder angle (CSA) is associated with impingement and rotator cuff lesions, and ultrasound-guided corticosteroid injection is effective for subacromial bursitis. However, because the efficacy of this treatment varies, this study investigated the effect of the CSA on the efficacy of corticosteroid injection in the subacromial space. Patients who received a diagnosis of subacromial bursitis after a clinical physical examination and ultrasound were enrolled prospectively from May 2019 to December 2021. Patients’ baseline variables and CSAs were assessed before intervention. Patients’ shoulder pain and disability index (SPADI), visual analog scale (VAS), and shoulder joint range of motion (ROM) scores were assessed at 2, 6, and 12 weeks after ultrasound-guided corticosteroid injection. All participants were divided into CSA > 38° and CSA ≤ 38° groups. We conducted the intragroup and intergroup comparisons of the variables and performed Pearson analysis to identify potential correlations between the CSA and outcome parameters. A total of 55 patients were enrolled in this study. Of these, 28 were included in the CSA > 38° group and 27 in the CSA ≤ 38° group. The baseline variables of the two groups did not differ. In the intragroup and intergroup comparisons, although VAS, SPADI, and ROM scores improved up to 12 weeks after intervention, no difference was identified between groups. The Pearson analysis revealed a positive correlation (r = 0.30, p = 0.024) between the CSA and VAS scores before the intervention. However, no correlation was found between the CSA and follow-up parameters. The CSA was not associated with the clinical efficacy of ultrasound-guided corticosteroid injection for subacromial bursitis.

Histological changes and neural elements in the subacromial bursa on patients with rotator cuff tear: Pilot study

OBJECTIVE

This study aimed to investigate the neural elements of the subacromial bursa (SAB) in rotator cuff tears.

MATERIALS AND METHODS

Twenty patients with rotator cuff tears were recruited, and their visual analog scale (VAS) score, duration of symptoms, and range of motion (ROM), including flexion, external rotation, and internal rotation were evaluated. Tear size was measured using magnetic resonance imaging (MRI). The SAB specimens obtained during arthroscopic rotator cuff repair were studied using routine hematoxylin and eosin staining and immunohistochemistry (S-100 protein and PGP 9.5 protein). The SAB specimen for the control group was obtained from 2 fresh cadavers and 2 patients with acute humeral shaft fracture. The Mann-Whitney U test was applied to assess the difference between histological findings of the rotator cuff tear group and control group. The correlation between the histological findings and clinical features was evaluated using the Spearman correlation coefficient.

RESULTS

The mean duration of symptom was 10.2 ± 6.4 months. The preoperative average VAS score was 2.9 ± 1.2. The degrees of preoperative ROM in forward flexion and external and internal rotations were 143.8 ± 19.5, 49.5 ± 23.1, and -4.3 ± 4.2, respectively. The tear was 2.0 ± 0.9 cm. For histological findings, the number of neural elements per low power field in the rotator cuff tear group was significantly less than the control group in both immunohistochemical stainings (S-100: 0.5 ± 0.7 vs 2.8 ± 0.5, p < .01; PGP 9.5: 0.4 ± 0.7 vs 3.5 ± 0.6, p < .01). During the correlation analysis, the number of neural elements in the PGP 9.5 staining was negatively correlated with the ROM in forward flexion and external rotation.

CONCLUSION

This study revealed that chronic rotator cuff tears may induce degeneration of neural elements in SAB.

The morphology of the subacromial and related shoulder bursae. An anatomical and histological study

Shoulder bursae are essential for normal movement and are also implicated in the pathogenesis of shoulder pain and dysfunction. The subacromial bursa (SAB), within the subacromial space, is considered a primary source of shoulder pain. Several other bursae related to the subcoracoid space, including the coracobrachial (CBB), subcoracoid (SCB) and subtendinous bursa of subscapularis (SSB), are also clinically relevant. The detailed morphology and histological characteristics of these bursae are not well described. Sixteen embalmed cadaveric shoulders from eight individuals (five females, three males; mean age 78.6 ± 7.9 years) were investigated using macro-dissection and histological techniques to describe the locations, dimensions and attachments of the bursae, their relationship to surrounding structures and neurovascular supply. Bursal sections were stained with haematoxylin and eosin to examine the synovium and with antibodies against von Willebrand factor and neurofilament to identify blood vessels and neural structures respectively. Four separate bursae were related to the subacromial and subcoracoid spaces. The SAB was large, with a confluent subdeltoid portion in all except one specimen, which displayed a distinct subdeltoid bursa. The SAB roof attached to the lateral edge and deep surface of the acromion and coracoacromial ligament, and the subdeltoid fascia; its floor fused with the supraspinatus tendon and greater tubercle. The CBB (15/16 specimens) was deep to the conjoint tendon of coracobrachialis and short head of biceps brachii and the tip of the coracoid process, while the inconstant SCB (5/16 specimens) was deep to the coracoid process. Located deep to the subscapularis tendon, the SSB was a constant entity that commonly displayed a superior extension. Synovial tissue was predominantly areolar (SAB and SSB) or fibrous (CBB and SCB), with a higher proportion of areolar synovium in the bursal roofs compared to their floors. Blood vessels were consistently present in the subintima with a median density of 3% of the tissue surface area, being greatest in the SSB and SAB roofs (4.9% and 3.4% respectively) and least in the SAB floor (1.8%) and CBB roof and floor (both 1.6%). Nerve bundles and free nerve endings were identified in the subintima in approximately one-third of the samples, while encapsulated nerve endings were present in deeper tissue layers. The extensive expanse and attachments of the SAB support adoption of the term subacromial-subdeltoid bursa. Morphologically, the strong attachments of the bursal roofs and floors along with their free edges manifest as fixed and mobile portions, which enable movement in relation to surrounding structures. The presence of neurovascular structures demonstrates that these bursae potentially contribute blood supply to surrounding structures and are involved in mechanoreception. The anatomical details presented in this study clarify the morphology of the shoulder bursae, including histological findings that offer further insight into their potential function.

Subacromial Bursal Tissue and Surrounding Matrix of Patients Undergoing Rotator Cuff Repair Contains Progenitor Cells

PURPOSE

To build upon previous literature to identify a complete analysis of cellular contents of subacromial bursal tissue as well as the matrix surrounding the rotator cuff.

METHODS

Samples of subacromial bursal tissue and surrounding matrix milieu from above the rotator cuff tendon and above the rotator cuff muscle bellies were obtained from 10 patients undergoing arthroscopic rotator cuff repair. Samples were analyzed using fluorescent-activated cell sorting and histologic analysis with staining protocols (Oil Red O, Alcian Blue, and Picro-Sirius Red), for identification of matrix components, including fat, proteoglycans, and collagen.

RESULTS

Progenitor cells and fibroblast-type cells were present in significant amounts in subacromial bursal tissue in both tissues obtained from over the tendinous and muscle belly portions. Markers for neural tissue, myeloid cells, and megakaryocytes also were present to a lesser extent. There were prominent amounts of fat and proteoglycans present in the matrix, based on ImageJ analysis of stained histologic slides.

CONCLUSIONS

The subacromial bursal tissue and surrounding matrix of patients undergoing rotator cuff repair contains progenitor cells in significant concentrations both over the tendon and muscle belly of the rotator cuff.

CLINICAL RELEVANCE

This presence of progenitor cells, in particular, in the subacromial bursal tissue provides a potential basis for future applications of augmentation purposes in rotator cuff healing, and calls into question the practice of routine bursectomy. As the potential role of bursal tissue contents in growth and regeneration in the setting of rotator cuff healing is more well understood, maintaining this tissue may become more relevant. Concentration of these cellular components for use in autologous re-implantation is also an avenue of interest.

The Effect of Acromioplasty or Bursectomy on the Results of Arthroscopic Repair of Full Thickness Rotator Cuff Tears: Does the Acromion Type Affect These Results?

Objectives:

The aim of this study was to investigate the effect of subacromial decompression on the results of full thickness rotator cuff repair applied arthroscopically. Examination was also made of the effect of acromion type on the subacromial decompression procedure in patients applied with arthroscopic rotator cuff repair.

Methods:

The study included a total of 150 patients, comprising 102 (68%) females and 48 (32%) males with a full thickness rotator cuff tear repaired arthroscopically. The patients were separated into three groups of 50. Group A comprised those with acromioplasty and bursectomy applied additional to the repair. In Group B, only bursectomy was performed additional to the repair and in Group C, only rotator cuff repair was applied. Evaluation was made of the post-operative long-term pain and functional results.

Results:

The mean age of the cases was 65.63±9.22 years (range, 46–86 years). The affected side was right side in 95 (63.3%) cases and left side in 55 (36.7%). No statistically significant difference was determined between the groups according to the post-operative Constant Murley and ASES scores (p>0.05). In the paired comparisons, the post-operative VAS scores of Group C were higher than those of Groups A and B (p=0.018, p=0.029, p<0.05). No statistically significant difference was determined between Group A and Group B in respect of the post-operative VAS scores (p>0.05).

Conclusion:

In the arthroscopic repair of full thickness rotator cuff tears, neither acromioplasty, coracoacromial ligament loosening nor bursectomy were determined to have any positive effect on the results. Whatever the acromion type, there is no need for an additional subacromial decompression procedure after rotator cuff repair, in respect of pain and functional outcomes. Only acromial spurs should be gently removed paying attention to the coraco-acromial ligament.

The Usefulness of Serological Inflammatory Markers in Patients with Rotator Cuff Disease—A Systematic Review

Background and Objectives: Rotator cuff disease (RCD) is a prominent musculoskeletal pain condition that spans a variety of pathologies. The etiology and precise diagnostic criteria of this condition remain unclear. The current practice of investigating the biochemical status of RCD is by conducting biopsy studies but their invasiveness is a major limitation. Recent biochemical studies on RCD demonstrate the potential application of serological tests for evaluating the disease which may benefit future clinical applications and research. This systematic review is to summarize the results of available studies on serological biochemical investigations in patients with RCD. Methods: An electronic search on databases PubMed and Virtual Health Library was conducted from inception to 1 September 2021. The inclusion criteria were case-control, cross-sectional, and cohort studies with serological biochemical investigations on humans with RCD. Methodological quality was assessed using the Study Quality Assessment Tool for Observational Cohort and Cross-sectional studies from the National Heart, Lung, and Blood Institute. Results: A total of 6008 records were found in the databases; of these, 163 full-text studies were checked for inclusion and exclusion criteria. Nine eligible studies involving 984 subjects with RCD emerged from this systematic review. The quality of the studies found ranged from poor to moderate. In summarizing all the studies, several fatty acids, nonprotein nitrogen, interleukin-1 β, interleukin-8, and vascular endothelial growth factor were found to be significantly higher in blood samples of patients with RCD than with control group patients, while Omega-3 Intex, vitamin B12, vitamin D, phosphorus, interleukin-10, and angiogenin were observed to be significantly lower. Conclusions: This is the first systematic review to summarize current serological studies in patients with RCD. Results of the studies reflect several systemic physiological changes in patients with RCD, which may prove helpful to better understand the complex pathology of RCD. In addition, the results also indicate the possibility of using serological tests in order to evaluate RCD; however, further longitudinal studies are required.

Subacromial Bursa: A Neglected Tissue Is Gaining More and More Attention in Clinical and Experimental Research

The subacromial bursa has long been demolded as friction-reducing tissue, which is often linked to shoulder pain and, therefore, partially removed during shoulder surgery. Currently, the discovery of the stem cell potential of resident bursa-derived cells shed a new light on the subacromial bursa. In the meanwhile, this neglected tissue is gaining more attention as to how it can augment the regenerative properties of adjacent tissues such as rotator cuff tendons. Specifically, the tight fibrovascular network, a high growth factor content, and the large progenitor potential of bursa-derived cells could complement the deficits that a nearby rotator cuff injury might experience due to the fact of its low endogenous regeneration potential. This review deals with the question of whether bursal inflammation is only a pain generator or could also be an initiator of healing. Furthermore, several experimental models highlight potential therapeutic targets to overcome bursal inflammation and, thus, pain. More evidence is needed to fully elucidate a direct interplay between subacromial bursa and rotator cuff tendons. Increasing attention to tendon repair will help to guide future research and answer open questions such that novel treatment strategies could harvest the subacromial bursa's potential to support healing of nearby rotator cuff injuries.

Serum Levels of TNF-α Are Increased in Patients with Rotator Cuff Tear and Sleep Disturbance

The purpose of this study was to determine serum levels of sleep-related cytokines in patients with rotator cuff tear (RCT) who were experiencing pain-related sleep disturbance. Peripheral blood samples before surgery were collected from 63 study participants and divided into three groups: RCT with sleep disturbance group; SD group (n = 21), RCT with normal sleep group; NS group (n = 21), and patients with chronic shoulder instability; control group (n = 21). Serum concentration levels of interleukin-1α (IL-1α), IL-1β, IL-2, IL-6, IL-8, IL-10, and tumor necrosis factor-α (TNF-α) were measured via ELISA. The associations between serum levels of sleep-related cytokines and clinical scores and the Pittsburgh Sleep Quality Index (PSQI) were analyzed. Serum concentration levels of TNF-α were significantly higher in the SD group compared with those of the NS and control groups (p = < 0.001 and 0.05). Serum levels of IL-8 and IL-10 were significantly higher in the SD group compared with those of control group (p = 0.01 and = 0.05), but did not differ significantly from that of the NS group. There were no associations between serum levels of sleep-related cytokines and all clinical scores. The current findings suggest that TNF-α may be associated with sleep disturbance in patients with RCT.

The Subacromial Bursa: Current Concepts Review

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The subacromial bursa is a distinct anatomic structure with distinct histologic features; it plays a critical role in the symptoms of the painful shoulder and in the local healing capacity of the rotator cuff tendon.

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Treatment of pain from bursitis of the subacromial bursa largely involves nonoperative interventions; however, operative treatment may be considered in certain instances.

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Preservation of the subacromial bursa should occur whenever possible given its intrinsic trophic and pluripotent factors, which have been shown to play important roles in rotator cuff tendon pathology.

Cellular and molecular modulation of rotator cuff muscle pathophysiology

Rotator cuff (RC) tendon tears are common shoulder injuries that result in irreversible and persistent degeneration of the associated muscles, which is characterized by severe inflammation, atrophy, fibrosis, and fatty infiltration. Although RC muscle degeneration strongly dictates the overall clinical outcomes, strategies to stimulate RC muscle regeneration have largely been overlooked to date. In this review, we highlight the current understanding of the cellular processes that coordinate muscle regeneration, and the roles of muscle resident cells, including immune cells, fibroadipogenic progenitors, and muscle satellite cells in the pathophysiologic regulation of RC muscles following injury. This review also provides perspectives for potential therapies to alleviate the hallmarks of RC muscle degeneration to address current limitations in postsurgical recovery.

Histological and molecular features of the subacromial bursa of rotator cuff tears compared to non-tendon defects: a pilot study

Background

The role of the subacromial bursa in the development or healing of shoulder pathologies is unclear. Due to this limited knowledge, we aimed to understand specific reactions of the subacromial bursa according to rotator cuff (RC) pathologies compared to non-tendon defects of the shoulder. We hypothesized that the tissue composition and inflammatory status of the bursa are likely to vary between shoulder pathologies depending on the presence and the extent of RC lesion.

Method

Bursa samples from patients with either 1) shoulder instability with intact RC (healthy bursa, control), 2) osteochondral pathology with intact RC, 3) partial supraspinatus (SSP) tendon tear, or 4) full-thickness SSP tear were investigated histologically and on gene expression level.

Result

Bursae from SSP tears differed from non-tendon pathologies by exhibiting increased chondral metaplasia and TGFβ1 expression. MMP1 was not expressed in healthy bursa controls, but strongly increased with full-thickness SSP tears. Additionally, the expression of the inflammatory mediators IL1β, IL6, and COX2 increased with the extent of SSP tear as shown by correlation analysis. In contrast, increased angiogenesis and nerve fibers as well as significantly upregulated IL6 and COX2 expression were features of bursae from patients with osteochondral pathology. Using immunohistochemistry, CD45+ leukocytes were observed in all examined groups, which were identified in particular as CD68+ monocytes/macrophages.

Conclusion

In summary, besides the strong increase in MMP1 expression with SSP tear, molecular changes were minor between the investigated groups. However, expression of pro-inflammatory cytokines correlated with the severity of the SSP tear. Most pronounced tissue alterations occurred for the osteochondral pathology and full-thickness SSP tear group, which demonstrates that the bursal reaction is not exclusively dependent on the occurrence of an SSP tear rather than longstanding degenerative changes. The present bursa characterization contributes to the understanding of specific tissue alterations related to RC tears or non-tendon shoulder pathologies. This pilot study provides the basis for future studies elucidating the role of the subacromial bursa in the development or healing of shoulder pathologies.

Chronicity is associated with the glenohumeral synovitis in patients with a rotator cuff tear

Synovitis of the glenohumeral joint (GHJ) and subacromial space (SAS) is one of the most common findings during arthroscopic rotator cuff repair (RCR). The purpose of this study is to determine clinical factors associated with the degree of synovitis in patients with a rotator cuff tear and whether macroscopic synovitis affects early clinical outcomes following arthroscopic RCR. Arthroscopic videos of 230 patients treated with arthroscopic RCR were randomly reviewed by two experienced shoulder surgeons. The synovitis scores of the GHJ using Davis's grading system and the SAS using Jo's grading system were rated with a consensus. Univariate and multivariate analyses were used to identify the associations between the synovitis scores and various parameters, including demographics, preoperative, and postoperative clinical outcomes. Univariate analyses revealed that age, side, body mass index, duration of symptoms, preoperative stiffness, diabetes, muscle atrophy, fatty infiltration, tear size, preoperative clinical scores, and preoperative range of motion were significantly associated with the GHJ synovitis score (all p < 0.05). Multivariate analyses revealed that the duration of symptoms, tear size, and diabetes was significantly associated with the GHJ synovitis score (p = 0.048, p = 0.025, p = 0.011, respectively). Longer duration of symptoms, larger tear size, and the presence of diabetes was independently associated with increased GHJ synovitis in patients with a rotator cuff tear. These results suggest that GHJ synovitis might be more involved in the pathogenesis for pain and tear progression of rotator cuff disease compared with SAS synovitis.

A genome-wide association study for shoulder impingement and rotator cuff disease

BACKGROUND

The purpose of the study was to identify genetic variants associated with rotator cuff disease by performing a genome-wide association study (GWAS) for shoulder impingement using the UK Biobank (UKB) cohort and then combining the GWAS data with a prior GWAS for rotator cuff tears. The loci identified by the GWAS and meta-analysis were examined for changes in expression following rotator cuff tearing using RNA sequencing.

METHODS

A GWAS was performed using data from UKB with 3864 cases of shoulder impingement. The summary statistics from shoulder impingement and a prior study on rotator cuff tears were combined in a meta-analysis. Also, the previous association of 2 single-nucleotide polymorphisms (SNPs) with shoulder impingement from a published GWAS using the UKB was tested. Rotator cuff tendon biopsies were obtained from 24 patients with full-thickness rotator cuff tears who underwent arthroscopic rotator cuff repair (cases) and 9 patients who underwent open reduction internal fixation for a proximal humeral fracture (controls). Total RNA was extracted and differential gene expression was measured by RNA sequencing for genes with variants associated with rotator cuff tearing.

RESULTS

The shoulder impingement GWAS identified 4 new loci: LOC100506457, LSP1P3, LOC100506207, and MIS18BP1/LINC00871. Combining data with a prior GWAS for rotator cuff tears in a meta-analysis resulted in the identification of an additional 7 loci: SLC39A8/UBE2D3, C5orf63, ASTN2, STK24, FRMPD4, ACOT9/SAT1, and LINC00890/ALG13. Many of the identified loci have known biologic functions or prior associations with diseases, suggesting possible biologic pathways leading to rotator cuff disease. RNA sequencing experiments show that expression of STK24 increases whereas expression of SAT1 and UBE2D3 decreases following rotator cuff tearing. Two SNPs previously reported to show an association with shoulder impingement from a prior UKB GWAS were not validated in our study.

CONCLUSION

This is the first GWAS for shoulder impingement in which new data from UKB enabled the identification of 4 loci showing a genetic association. A meta-analysis with a prior GWAS for rotator cuff tearing identified an additional 7 loci. The known biologic roles of many of the 11 loci suggest plausible biologic mechanisms underlying the etiology of rotator cuff disease. The risk alleles from each of the genetic loci can be used to assess the risk for rotator cuff disease in individual patients, enabling preventative or restorative actions via personalized medicine.

Distinct Gene Expression Profile in Patients With Poor Postoperative Outcomes After Rotator Cuff Repair: A Case-Control Study

BACKGROUND

Impaired healing after rotator cuff repair is a major concern, with retear rates as high as 94%. A method to predict whether patients are likely to experience poor surgical outcomes would change clinical practice. While various patient factors, such as age and tear size, have been linked to poor functional outcomes, it is currently very challenging to predict outcomes before surgery.

PURPOSE

To evaluate gene expression differences in tissue collected during surgery between patients who ultimately went on to have good outcomes and those who experienced a retear, in an effort to determine if surgical outcomes can be predicted.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

Rotator cuff tissue was collected at the time of surgery from 140 patients. Patients were tracked for a minimum of 6 months to identify those with good or poor outcomes, using clinical functional scores and follow-up magnetic resonance imaging to confirm failure to heal or retear. Gene expression differences between 8 patients with poor outcomes and 28 patients with good outcomes were assessed using a multiplex gene expression analysis via NanoString and a custom-curated panel of 145 genes related to various stages of rotator cuff healing.

RESULTS

Although significant differences in the expression of individual genes were not observed, gene set enrichment analysis highlighted major differences in gene sets. Patients who had poor healing outcomes showed greater expression of gene sets related to extracellular matrix production (P < .0001) and cellular biosynthetic pathways (P < .001), while patients who had good healing outcomes showed greater expression of genes associated with the proinflammatory (M1) macrophage phenotype (P < .05).

CONCLUSION

These results suggest that a more proinflammatory, fibrotic environment before repair may play a role in poor healing outcome. With validation in a larger cohort, these results may ultimately lead to diagnostic methods to preoperatively predict those at risk for poor surgical outcomes.

The interaction between human rotator cuff tendon and subacromial bursal tissue in co-culture

BACKGROUND

The role of subacromial bursa in rotator cuff pathology is unclear. Along with recognized inflammatory potential, current data demonstrate the presence of mesenchymal stem cells and potential regenerative properties of the bursa. The purpose of this study was to (1) approximate an in vitro co-culture model that represents interaction between torn rotator cuff tendon and subacromial bursa, (2) quantify the cellular activity of tendon and bursa and their interactions, (3) use this model to induce a state of inflammation present with rotator cuff pathology.

METHODS

In part 1, tendon and bursa samples were obtained from 6 patients undergoing rotator cuff repair. Tendon and bursa were cultured alone and together in co-culture wells for 21 days. Markers specific for tenocyte gene expression (tenascin C, decorin, etc) were measured in both tendon and bursa alone and compared to co-culture models. In part 2 of the study, an inflammatory state was induced with interleukin-1β treatment, and markers of inflammation were measured via protein assay at 0 and 21 days in samples from 7 additional patients.

RESULTS

There was an increase in tendon and bursa markers in nearly all groups as evidenced by increased gene expression of known tendon and bursa markers. There was a significant increase in gene expression when torn tendon was co-cultured with bursa compared with culturing alone. Additionally, a state of inflammation was induced as evidenced by increased markers of inflammation, inflammatory protein concentration, and inflammatory cells and disruption of histologic morphology.

CONCLUSION

There is a clear interaction between rotator cuff tendon and the milieu produced by the subacromial bursa in this in vitro co-culture system that is significantly different when compared to an isolated culture of tendon and bursa. This system was successfully used to induce a state of inflammation that may represent in vivo inflammation. This in vitro model of rotator cuff pathology can aid investigators in testing effects of agents proposed to improve rotator cuff healing. This can lead to further knowledge regarding effective treatment options.

The inflammatory response of the supraspinatus muscle in rotator cuff tear conditions

BACKGROUND

Rotator cuff (RC) disorders involve a spectrum of shoulder conditions from early tendinopathy to full-thickness tears leading to impaired shoulder function and pain. The pathology of RC disorder is, nonetheless, still largely unknown. Our hypothesis is that a supraspinatus (SS) tendon tear leads to sustained inflammatory changes of the SS muscle along with fatty infiltration and muscle degeneration, which are threshold markers for poor RC muscle function. The aim of this study was to determine the extent of this muscle inflammation in conjunction with lipid accumulation and fibrosis in RC tear conditions.

METHODS

We used proteomics, histology, electrochemiluminescence immunoassay, and quantitative polymerase chain reaction analyses to evaluate inflammatory and degenerative markers and fatty infiltration in biopsies from 22 patients undergoing surgery with repair of a full-thickness SS tendon tear.

RESULTS

Bioinformatic analysis showed that proteins involved in innate immunity, extracellular matrix organization, and lipid metabolism were among the most upregulated, whereas mitochondrial electronic transport chain along with muscle fiber function was among the most downregulated. Histologic analysis confirmed changes in muscle fiber organization and the presence of inflammation and fatty infiltration. Inflammation appeared to be driven by a high number of infiltrating macrophages, accompanied by elevated matrix metalloprotease levels and changes in transforming growth factor-β and cytokine levels in the SS compared with the deltoid muscle.

CONCLUSIONS

We demonstrated massive SS muscle inflammation after the tendon tear combined with fatty infiltration and degeneration. The regulation of tissue repair is thus extremely complex, and it may have opposite effects at different time points of healing. Inhibition or stimulation of muscle inflammation may be a potential target to enhance the outcome of the repaired torn RC.

A prospective, comparative study of subacromial corticosteroid injection and subacromial corticosteroid injection plus suprascapular nerve block in patients with shoulder impingement syndrome

INTRODUCTION

Efforts are recently focused on the management of shoulder impingement syndrome (SIS) with a conservative and targeted approach because of its psychosocial impact, reduction in the quality of life, the cost to the economy and its negative effect on daily activities. Therefore, many studies have been designed to evaluate and compare the effectiveness of different treatments. The main purpose of this study was to identify the effect of combination of subacromial corticosteroid injection (SCI) and suprascapular nerve block (SSNB) on shoulder impingement syndrome (SIS).

MATERIALS AND METHODS

66 patients with SIS were randomly divided into two groups (33 patients per group): Group 1: SCI; Group 2: SCI plus SSNB. The estimation of the severity of pain by the visual analogue scale (VAS) and shoulder disability using quick DASH (Disabilities of the Arm, Shoulder and Hand) were assessed at baseline and 1, 3 months post-injection.

RESULTS

The mean age of patients was 55.55 ± 10.42 years in Group 1 and 57.24 ± 12.75 years in Group 2. In steroid group, pre- and post-treatment (at 1 and 3 months) VAS/quickDASH scores were 8.64 ± 0.99/78.03 ± 9.24, 2.09 ± 0.84/15.58 ± 7.23 and 3.06 ± 1.12/25.06 ± 8.74, respectively. In steroid plus SSNB group, pre- and post-treatment (at 1 and 3 months) VAS/quickDASH scores were 8.45 ± 0.90/75.15 ± 9.86, 1.24 ± 0.43/10.88 ± 2.14 and 1.51 ± 0.56/15.51 ± 5.04, respectively. Both treatment groups showed a significant relief of pain at 1 and 3 months post-injection (p < 0.05). However, the VAS and quickDASH scores at 1 and 3 months were significantly lower in Group 2 versus Group 1 (p < 0.05).

CONCLUSION

The combination of SCI and SSNB seems to produce the long-term effect in pain relief and functional improvement.

Pathological changes of frozen shoulder in rat model and the therapeutic effect of PPAR-γ agonist

Frozen shoulder is a common shoulder disorder characterized by a gradual increase of pain and a limited range of motion. However, its pathophysiologic mechanisms remain unclear and there is no consensus as to the most effective treatment. The purpose of the study was to investigate the effect of transforming growth factor-β (TGF-β) on fibrosis and inflammatory response of the shoulder joint of rat models and to explore the therapeutic effect of the peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist. In the study, the effect of PPAR-γ agonist CDDO-IM treatment on cell proliferation, migration, and extracellular matrix proteins synthesis (vimentin, α-smooth muscle actin, collagen I, and collagen III) were tested by cell proliferation test, scratches test, real-time quantitative polymerase chain reaction, and Western blot analysis. The frozen shoulder was also established on the rat model by injecting adenovirus-TGF-β1 into rats' shoulder capsule. Pathological changes of the frozen shoulder tissue of the experimental group and PPAR-γ agonist treatment group were evaluated. The stiffness of joints of the three groups was tested. Inflammatory mediators' expression including cyclooxygenase-1, interleukin-1β, and tumor necrosis factor-α of the shoulder was tested by enzyme-linked immunosorbent assay, and the expression of extracellular matrix proteins was evaluated by hematoxylin and eosin staining and immunohistochemistry. The results showed that pathological changes of the frozen shoulder in the rat model include an abnormal proliferation of fibroblasts, infiltration of inflammatory cells, and disorder of fibrous structure, while rosiglitazone reduced the severity of the frozen shoulder in the treatment group. Clinically, PPAR-γ agonists may be a promising target for the treatment of the frozen shoulder.

Relationship between fatty infiltration and gene expression in patients with medium rotator cuff tear

BACKGROUND

Fatty infiltration (FI) is a key prognostic factor that affects outcomes after rotator cuff repair and is radiologically evaluated using the Goutallier classification. The purpose of this study was to assess alterations in gene and protein expression according to the Goutallier classification in the supraspinatus muscle and any relationships among various gene expression profiles.

METHODS

Twenty-four samples of the supraspinatus muscle from 12 patients with a high FI grade (grade 3 or 4) and 12 patients with a low FI grade (grade 1 or 2) with medium-sized tears were acquired during arthroscopic surgery. Alterations in the expression of genes and proteins associated with adipogenesis, fibrosis, inflammation, and muscle atrophy were compared between the high- and low-FI groups using reverse-transcription quantitative polymerase chain reaction, Western blotting, and immunohistochemistry.

RESULTS

mRNA expression of not only the adipogenic genes (peroxisome proliferator-activated receptor γ and CCAAT/enhancer-binding protein α; P < .001 and P = .020) but also the fibrosis-related gene (α-smooth muscle actin; P < .001), inflammation-related genes (interleukin [IL]-1β and tumor necrosis factor α; P = .041 and P = .039), and muscle atrophy-related genes (atrogin 1 and myostatin; P = .006 and P < .001) was higher in the high-FI group compared with that in the low-FI group. In addition, adipogenic gene expression was significantly correlated with the expression of other categories of genes (all P < .05, except atrogin 1). A correlation of gene and protein expression was observed for IL-1β (P = .027) and myostatin (P = .029).

CONCLUSIONS

The radiologic grading of FI was associated with the expression of various genes, including adipogenic, fibrotic, inflammatory, and atrophy-related genes, and these genes were closely correlated with each other in terms of expression. This information could be helpful in patient counseling.

Subacromial bursal preservation can enhance rotator cuff tendon regeneration: a comparative rat supraspinatus tendon defect model study

BACKGROUND

The role of subacromial bursa in rotator cuff surgery is unknown. This study aimed to assess the subacromial bursa's role in the healing of supraspinatus tendon injury in a rat model.

METHODS

Twenty-three male Sprague-Dawley rats (9 weeks old; weight, approximately 296 g) were used in this study. Three rats used as biomechanical study controls were killed at 12 weeks of age. A supraspinatus tendon defect was made bilaterally in 20 rats, whereas an additional subacromial bursa sectioning was performed on the left side. Six rats were killed for biomechanical testing and 4 were killed for histologic observation at 3 and 9 weeks, respectively.

RESULTS

The regenerated tendon in the bursal preservation group showed significantly superior biomechanical properties in maximum load to failure at 3 and 9 weeks and stiffness at 9 weeks after surgery compared with the bursal removal group. The modified Bonar scale scores showed better regenerated supraspinatus tendons in the bursal preservation group.

CONCLUSION

The present study found that the subacromial bursa plays an important role in rotator cuff regeneration in this rat supraspinatus injury model. Extensive bursectomy of the subacromial bursa may not be recommended in rotator cuff repair surgery, though future in vivo human studies are needed to confirm these observations.

Factors affecting the onset and progression of rotator cuff tears in the general population

While previous studies have revealed factors affecting the progression of rotator cuff tear (RCT), none have yet described factors affecting its onset. The purpose of this longitudinal observational study was to analyze factors affecting the RCT onset and progression in the general population. The present study included 185 shoulders from 93 participants who completed all the examinations in both 2012 and 2017. Participants received a questionnaire with age, gender, arm dominance, and presence of pain at rest, in motion, and at night. The range of motion (ROM), simple shoulder test (SST) were also examined. Anteroposterior radiograph of the shoulder joint was performed to evaluate the degree of osteoarthritic changes by the Samilson-Prieto (S-P) classification. The degree of RCT was examined by ultrasonography. There were 132 shoulders without RCT and 53 with RCT in 2012. RCT occurred in 21 of 132 shoulders, and the factor affecting the RCT onset was S-P grade 2 osteoarthritic change in 2012 (odds ratio [OR] 10.10). RCT progressed in 22 of 53 shoulders, and the factor affecting RCT progression was the presence of motion pain in 2012 (OR 13.76). These results added new knowledge regarding the natural course of RCT onset and progression.

Increased levels of inflammatory markers in the subscapularis tendon and joint capsule in patients with subacromial impingement

PURPOSE

To analyze biopsy samples from the subscapularis tendon and from the joint capsule from male patients with subacromial impingement syndrome and compare them with samples from male patients with post-traumatic recurrent shoulder instability, to detect increased inflammatory activity that might be present inside the humeroscapular joint.

METHODS

Twenty male patients scheduled for surgery for either subacromial decompression or Bankart reconstruction were included. Four biopsies from each patient were obtained during surgery from the capsule and the subscapularis tendon. Each specimen was analyzed for TNF-α, IL-6, CD-3 and CD-72. Multiplex fluorescence immunohistochemistry was performed on histological samples from the capsule and tendon to demonstrate the level of inflammatory markers. Fluorescence microscope images were acquired using an automated scanning system. On each slide, the number of pixels was registered and used in the analyses.

RESULTS

The subacromial impingement syndrome group comprised eight patients, median age 53 (45-74) years, while the instability group 12, median age 27 (22-48) years (p < 0.00001). The amount of IL-6 and TNF-α was significantly higher in the subscapularis tendon of the patients with subacromial impingement syndrome compared with instability patients (p = 0.0015 and p = 0.0008 respectively). In the capsular samples, significantly higher amount of TNF-α and CD-72 was found in patients with subacromial impingement syndrome compared with instability patients (p < 0.0001 for both). On the other hand, the amount of CD-3 was significantly higher in the instability group (p = 0.0013).

CONCLUSIONS

This study provides evidence that an extended inflammatory process is present, not only in the subacromial bursa but also in the glenohumeral joint in patients with subacromial impingement syndrome.

LEVEL OF EVIDENCE

Level III.

CLINICAL RELEVANCE

To develop a treatment targeted towards intra-articular inflammatory cytokines appears appealing.

Localized delivery of ibuprofen via a bilayer delivery system (BiLDS) for supraspinatus tendon healing in a rat model

The high prevalence of tendon retear following rotator cuff repair motivates the development of new therapeutics to promote improved tendon healing. Controlled delivery of non-steroidal anti-inflammatory drugs to the repair site via an implanted scaffold is a promising option for modulating inflammation in the healing environment. Furthermore, biodegradable nanofibrous delivery systems offer an optimized architecture and surface area for cellular attachment, proliferation, and infiltration while releasing soluble factors to promote tendon regeneration. To this end, we developed a bilayer delivery system (BiLDS) for localized and controlled release of ibuprofen (IBP) to temporally mitigate inflammation and enhance tendon remodeling following surgical repair by promoting organized tissue formation. In vitro evaluation confirmed the delayed and sustained release of IBP from Labrafil-modified poly(lactic-co-glycolic) acid microspheres within sintered poly(ε-caprolactone) electrospun scaffolds. Biocompatibility of the BiLDS was demonstrated with primary Achilles tendon cells in vitro. Implantation of the IBP-releasing BiLDS at the repair site in a rat rotator cuff injury and repair model led to decreased expression of proinflammatory cytokine, tumor necrotic factor-α, and increased anti-inflammatory cytokine, transforming growth factor-β1. The BiLDS remained intact for mechanical reinforcement and recovered the tendon structural properties by 8 weeks. These results suggest the therapeutic potential of a novel biocompatible nanofibrous BiLDS for localized and tailored delivery of IBP to mitigate tendon inflammation and improve repair outcomes. Future studies are required to define the mechanical implications of an optimized BiLDS in a rat model beyond 8 weeks or in a larger animal model.

Combined bursal aspiration and corticosteroid injection for rotator cuff tear patients unresponsive to conservative management: Case report

RATIONALE

Subacromial-subdeltoid (SASD) bursitis is characterized by bursal distension caused by fluid collection, commonly resulting from rotator cuff tears. Aspiration of the bursal fluid associated with rotator cuff tears tends to be overlooked. The effects of combined bursal aspiration and corticosteroid injection on full-thickness tears of the rotator cuff with SASD bursitis have not been previously reported.

PATIENT CONCERNS

We report the cases of 3 patients with shoulder pain caused by rotator cuff tears with marked amounts of fluid in the SASD bursa. The patients experienced intractable pain despite previous conservative management, including corticosteroid injection.

DIAGNOSES

Physical examination and imaging studies revealed rotator cuff tears with remarkable quantities of fluid in the SASD bursa.

INTERVENTIONS AND OUTCOMES

The patients underwent ultrasound (US)-guided aspiration of the bursal fluid and intra-articular corticosteroid injection, following which, all patients experienced reduced shoulder pain for several months.

LESSONS

Combined aspiration of fluid in the SASD bursa and intra-articular corticosteroid injection in the rotator cuff tear is recommended, especially in cases with untreated shoulder pain unresponsive to previous conservative management.

Mental health and tobacco use are correlated with PROMIS upper extremity and pain interference scores in patients with shoulder pathology

PURPOSE

To determine whether patient demographics have predictive influence on patient-reported outcomes measurement information system (PROMIS) domains of pain interference (PROMIS-PI), depression (PROMIS-D), and upper extremity (PROMIS-UE) for patients with shoulder pathology treated nonoperatively.

METHODS

Patients with partial rotator cuff tears, impingement, scapular dyskinesia, osteoarthritis, muscle strains, biceps tendonitis, instability, and acromioclavicular arthritis were retrospectively identified. Patients who underwent surgery were excluded. Demographic characteristics were documented, and PROMIS scores before and after nonoperative intervention were analyzed for correlations between each domain.

RESULTS

A total of 638 questionnaires (PROMIS-UE, PROMIS-PI, and PROMIS-D) were analyzed. PROMIS-UE had a strong negative correlation with PROMIS-PI (R = - 0.73, P < .001). PROMIS-PI and PROMIS-D demonstrated a positive correlation of moderate strength (R = 0.54, P < .001). Patients who never used tobacco, compared to current or former users, had significantly higher PROMIS-UE scores (34.5 vs. 30.6 and 31.9; P < .001), lower PROMIS-PI (59.7 vs. 63.1 and 60.9; P < .001), and lower PROMIS-D scores (47.3 vs. 52.1 and 49.3; P < .001). Patients with body mass index < 24.8 had significantly higher PROMIS-UE scores than those with > 24.8 (P < .05).

CONCLUSION

There is an inverse relationship between upper extremity physical function and pain and depression, as measured by PROMIS scores. Smoking and increased BMI are significant contributors to worse outcomes in patients with shoulder pathology, even in nonoperative populations. Counseling patients regarding prognosis and functional outcomes is important in managing their expectations in this patient population.

Gene Expression in Torn Rotator Cuff Tendons Determined by RNA Sequencing

Background:

Although the cause of rotator cuff tearing is likely multifactorial and a genetic predisposition has been proposed, the biochemical basis remains unknown.

Purpose:

To determine gene expression profiles in torn rotator cuff tendon tissue through use of RNA sequencing.

Study Design:

Controlled laboratory study.

Methods:

The supraspinatus tendon edge was biopsied in 24 patients undergoing arthroscopic rotator cuff repair for full-thickness supraspinatus rotator cuff tears. The supraspinatus tendon was also biopsied in 9 patients undergoing open reduction and internal fixation for a proximal humeral fracture (controls). Total RNA was extracted and sequenced. Differential gene expression was analyzed between the tear and control groups, and a secondary analysis was conducted between groups defined by an unbiased clustering.

Results:

Tear and control transcriptomes demonstrated significant differential expression in more than 3000 genes. The identified differential genes were highlighted in pathways involved in inflammation in control patients and extracellular matrix generation in patients with tears. Secondary analysis using unsupervised and thus unbiased hierarchical clustering revealed 2 clusters (c2 and c3). Cluster c3 contained smaller (P < .001) and less retracted (P = .018) tears (ie, tears earlier in the progression of rotator cuff disease) with increased expression of hypoxia target genes. Cluster c2 contained larger, more retracted tears (ie, tears further in the progression of rotator cuff disease) with increased expression of endothelial cell markers and chronic inflammation target genes. Tears in c2 had significantly worse healing rates compared with tears in c3 (0% vs 89%; P = .007).

Conclusion:

Smaller, less retracted tears had increased expression of hypoxia target genes and improved healing, whereas larger, more retracted tears were associated with endothelial cell markers and worse healing. Thus, hypoxia may be the inciting event for tear development, whereas with tear enlargement, a chronic, inflammatory, angiogenic process may predominate.

Clinical Relevance:

Identification of differential gene expression in rotator cuff tears may be a reliable tool to predict repair healing in the future.

Metabolic and inflammatory links to rotator cuff tear in hand osteoarthritis: A cross sectional study

Objectives

To estimate the prevalence and associated factors of rotator cuff tear (RCT) in patients with hand osteoarthritis (HOA).

Methods

Between June 2013 and December 2015, we recruited 1150 participants in rural area of South Korea. Of the 1150 participants, 307 participants with HOA were analyzed. Plain radiography of both hands, magnetic resonance imaging of both shoulders, and serum levels of high-sensitive C-reactive protein (hsCRP) and high-density lipoprotein (HDL) were obtained for all patients. HOA and RCT were diagnosed by clinical and radiologic findings.

Results

The prevalence of RCT in patients with HOA (192/307, 62.5%) was higher than that in those without HOA (410/827, 49.5%, p<0.001). Among the 307 patients with HOA, the patients with RCT were older, and had higher hsCRP and lower HDL levels than the patients without RCT. Multiple logistic regression analysis confirmed significant associations of age (odds ratio [OR], 1.06; 95% confidence interval [CI], 1.02–1.11), serum hsCRP levels ≥0.6mg/L (OR, 1.68; CI, 1.00–2.80), and low HDL levels (male, <50 mg/dL; female, <40 mg/dL) (OR, 1.93; CI, 1.05–3.56) with RCT in patients with HOA. For patients below 60 years old, the prevalence of RCT was 2.8-fold higher in the low HDL group than normal HDL group (p = 0.048). Finally, the prevalence of RCT was 2.6-fold higher in patients with HOA with both elevated hsCRP and low HDL levels compared with those with neither (p<0.05).

Conclusions

Our findings suggest inflammation and metabolic factors were associated with the prevalence of RCT in HOA patients.

Is there an association between metabolic syndrome and rotator cuff-related shoulder pain? A systematic review

Objectives

Rotator cuff-related shoulder pain (RCRSP) is a common upper limb complaint. It has been suggested that this condition is more common among people with cardiometabolic risk factors. This systematic review has synthesised evidence from case–control, cross-sectional and cohort studies on the association between metabolic syndrome (MetS) and RCRSP.

Design and data sources

Five medical databases (MEDLINE, EMBASE, SCOPUS, CINAHL and AMED) and reference checking methods were used to identify all relevant English articles that considered MetS and RCRSP. Studies were appraised using the Newcastle-Ottawa Scale (NOS). Two reviewers performed critical appraisal and data extraction. Narrative synthesis was performed via content analysis of statistically significant associations.

Results

Three cross-sectional, two case–control and one cohort study met the inclusion criteria, providing a total of 1187 individuals with RCRSP. Heterogeneity in methodology and RCRSP or MetS definition precluded a meaningful meta-analysis. Four of the included studies identified associations between the prevalence of MetS and RCRSP. Studies consistently identified independent cardiometabolic risk factors associated with RCRSP. All studies were level III evidence.

Summary and conclusion

The low-moderate quality evidence included in this review suggests an association between MetS and RCRSP. Most studies demonstrated moderate quality on appraisal. The direction of association and cardiometabolic factors influencing should be investigated by longitudinal and treatment studies. These preliminary conclusions and clinical utility should be treated with caution due to limitations of the evidence base.

Postoperative residual pain is associated with a high magnetic resonance imaging (MRI)-based signal intensity of the repaired supraspinatus tendon

PURPOSE

To assess patients with and without postoperative residual pain and to compare clinical function and magnetic resonance imaging (MRI) appearance of the repaired supraspinatus tendon between patients with and without pain.

METHODS

One-hundred and seventeen patients with supraspinatus tear were included in this study. Visual Analog Scale (VAS) scores for pain were assessed at a follow-up of at least 1 year. Patients with residual shoulder pain were enrolled in the residual pain group (RP group) and patients without pain enrolled in the no pain group (NP group). The American Shoulder and Elbow Surgeons (ASES) shoulder evaluation form, the modified University of California at Los Angeles (UCLA) score and the Fudan University Shoulder Score (FUSS) were also used to evaluate shoulder function. MRI examinations were performed to evaluate rotator cuff integrity according to the Sugaya method, and muscular hypotrophy, fatty infiltration, and signal/noise quotient (SNQ) of the rotator cuff tendon.

RESULTS

Thirty-five patients had residual pain (RP group) and 82 patients had no pain (NR group). At the final follow-up, there was a significant difference in ASES (92 ± 8 points vs 76 ± 10 points; p < 0.001), UCLA (32 ± 3 points vs 28 ± 3 points; p < 0.001), FUSS (90 ± 7 points vs 80 ± 9 points; p < 0.001) and strength (9 ± 3 kg vs 6 ± 2 kg; p < 0.001) between the NP group and the RP group, respectively. Postoperative MRI revealed that there was no significant difference in the retear rate (9.8% vs 8.6%; ns), the muscular hypotrophy (ns), and the fatty infiltration index (0.9 ± 0.2 vs 0.9 ± 0.2; ns) between the NP and the RP groups, respectively. The postoperative tendon SNQ of the RP group was significantly higher than that of the NP group (4.6 ± 2.5 vs 3 ± 1.7; p < 0.001). There was a significant association between tendon SNQ and VAS for this cohort ([Formula: see text] = 0.29; p = 0.003).

CONCLUSION

Postoperative residual pain is associated with a high MRI signal intensity of the repaired supraspinatus tendon. Since high signal intensity of tendon tissue indicates degenerated tendon tissue quality, it highlighted the necessity of debriding the degenerated rotator cuff tendon tissue.

LEVEL OF EVIDENCE

III.

IL-1β mediates NGF and COX-2 expression through transforming growth factor-activating kinase 1 in subacromial bursa cells derived from rotator cuff tear patients

BACKGROUND

Increased interleukin (IL)-1β expression in the subacromial bursa (SAB) is associated with severe pain in rotator cuff tears (RCTs). Additionally, transforming growth factor (TGF)-β-activated kinase 1 (TAK1) is essential for cytokine-mediated cascades. TAK1 also regulates the expression of pain-associated molecules such as cycloxygenase-2 (COX-2) and nerve growth factor (NGF) in synovial fibroblasts; however, this regulation in the SAB is not fully understood.

METHODS

SAB samples were harvested from 18 subjects with RCTs. The expression and localization of NGF and COX-2 was determined using polymerase chain reaction (PCR) analysis and immunohistochemistry. Regulation of COX-2 and NGF by IL-1β in subacromial bursa cells (SABCs) was investigated by culturing and stimulating SABCs with vehicle control (culture medium), 50 ng/ml recombinant human IL-1β (rhIL1-β), 50 ng/ml rhIL-1β and 10 μM celecoxib (COX-2 inhibitor), or 10 μM prostaglandin E2 (PGE2) for 24 h. The effects of TAK1 inhibition on rhIL-1β stimulation were determined by culturing and treating SABCs with control, 50 ng/ml rhIL-1β, or 50 ng/ml rhIL-1β and 10 μM (5Z)-7-oxozeaenol (TAK1 inhibitor) for 24 h. NGF and COX-2 mRNA expression was monitored using quantitative PCR.

RESULTS

COX-2 and NGF mRNA expression was observed in all SAB specimens. Immunohistochemical analysis showed that COX-2-positive cells were in the lining and sublining layers. NGF-positive cells were observed in the sublining layer. rhIL-1β treatment significantly increased NGF and COX-2 mRNA levels compared with control cells. The COX-2 inhibitor did not suppress rhIL-1β-induced NGF expression, and PGE2 stimulation did not alter NGF mRNA expression. In contrast, the TAK1 inhibitor significantly reduced rhIL-1β-stimulated COX-2 and NGF mRNA expression.

CONCLUSION

IL-1β regulates the expression of NGF and COX-2, pain-related molecules in the SAB, through TAK1. Therefore, TAK1 may be one potential therapeutic target for reducing pain in patients with RCTs.

Synovitis as a concomitant disease in shoulder pathologies

INTRODUCTION

Shoulder pathologies are often accompanied by rotator interval synovitis. This phenomenon is poorly described in the literature so far. The aim of the study was to analyze the occurrence of macroscopically visible synovial reaction in the rotator interval in patients with chronic shoulder pathologies and to perform a histopathological evaluation.

MATERIALS AND METHODS

In this prospective cohort study, 167 consecutive patients undergoing arthroscopic shoulder surgery for chronic shoulder pathology were included (♀ = 45, ♂ = 122; [Formula: see text]54.5 years ± 12.8). Included patients were divided into subgroups according to the encountered chronic shoulder pathology: (1) impingement syndrome with or without bursal sided partial rotator cuff tear (RCT); (2) articular sided partial RCT; (3) full-thickness RCT; (4) RCT that involves at least two tendons; (5) shoulder instability; and (6) cartilage damage. Standardized soft tissue biopsies from the rotator interval were taken. The synovitis score of Krenn/Morawietz was used for histopathological examination.

RESULTS

Extraarticular pathology (group 1) showed significantly decreased synovitis scores compared to all the other groups. Increased size of rotator cuff tears (group 4), as well as cartilage damage (group 6) showed significantly higher synovitis scores than group 3 (p < 0.05). Moreover, the synovitis score was significantly increased in patients with concomitant pathologies of the long head of the biceps (p = 0.001).

CONCLUSIONS

This study suggests that chronic intra- and extraarticular shoulder diseases are very often accompanied by a histopathologically verifiable low-grade synovitis. Intraarticular pathologies seem to induce increased levels of synovitis. Furthermore, the increased size of rotator cuff tears is accompanied by a higher degree of synovitis.

STUDY DESIGN

Cohort study, level of evidence, 2b.

Biological Augmentation With Subacromial Bursa in Arthroscopic Rotator Cuff Repair

Rotator cuff tears can be associated with significant shoulder dysfunction and pain. Despite improved surgical techniques and new materials for rotator cuff reconstruction, there is no significant reduction in the re-rupture rate. Innovative approaches for enhanced tendon healing are required. The potential of biologically optimized tendon integration has probably been insufficiently explored so far. The existing practice of debridement might eliminate repair tissue and a major source of cells and blood vessels necessary for tendon healing. Biological augmentation may be an option to improve the healing process. The subacromial bursa is a highly proliferative tissue with mesenchymal stem cells capable of differentiating into various cell lines and is easily accessible during rotator cuff repair. We describe the technique of bursal augmentation in arthroscopic double-row SutureBridge repair of a posterosuperior rotator cuff tear with the aim of improving tendon-to-bone healing.

Nerve growth factor continuously elevates in a rat rotator cuff tear model

BACKGROUND

Nerve growth factor (NGF) plays a key role in osteoarthritic pain and low back pain. Rotator cuff tear (RCT) is often associated with severe shoulder pain. However, the role of NGF in RCT remains to be fully understood.

METHODS

Rats were divided into sham and RCT groups. The rotator cuff was harvested from the sham and RCT groups on various days for reverse transcription-polymerase chain reaction analysis of Tnfa, Ngf, Il1b, and Cox2 expression. Rotator cuffs from the sham and RCT groups were also harvested at 1 and 14 days for enzyme-linked immunosorbent assay and immunohistochemistry to assess NGF protein levels and localization. Rotator cuff-derived cells were stimulated with rat recombinant tumor necrosis factor (TNF)-α to investigate the involvement of TNF-α in the regulation of NGF expression.

RESULTS

Tnfa and Ngf messenger RNA levels increased within 1 day in the RCT group. Notably, Tnfa and Ngf upregulation persisted for up to 56 days after the RCT surgery, while Il1b and Cox2 expression was significantly reduced. NGF levels in the RCT group were significantly higher than those in the sham operation group on days 1 and 14. Certain inflammatory cells and synovial-like cells lining the surface of the laminated tears were NGF-positive on days 1 and 14, respectively. Ngf messenger RNA levels increased significantly in rotator cuff-derived cells after TNF-α stimulation.

CONCLUSION

NGF levels are continuously elevated in RCT, which is mainly regulated by TNF-α. NGF may thus represent a potential target for therapies that modulate RCT pain.

Outcomes After Limited or Extensive Bursectomy During Rotator Cuff Repair: Randomized Controlled Trial

PURPOSE

To evaluate the effects of extensive bursectomy (EB) and limited bursectomy (LB) during arthroscopic rotator cuff repair.

METHODS

In the EB group (n = 39), subacromial bursae were thoroughly removed from anterior to posterior and lateral to medial. In the LB group (n = 39), bursectomy was minimized to allow torn cuff visualization and tendon repair. Visual analog scale pain scores, passive forward flexion, external rotation at the side (ER), and internal rotation at the back were measured at 5 weeks and 3, 6, and 12 months after surgery. At each time point, bursal thickness was measured and repair integrity was assessed by sonography or magnetic resonance imaging.

RESULTS

The analysis included 36 patients in the LB group and 35 in the EB group. Group visual analog scale pain scores were not significantly different at any time (P > .05 for all). Forward flexion and internal rotation at the back showed no intergroup difference during follow-up. However, ER was significantly better in the LB group at 6 months and 1 year postoperatively (31° ± 15° vs 22° ± 16° [P = .020] and 40° ± 19° vs 27° ± 20° [P = .009], respectively). Integrity failures were not significantly different at 5 weeks and at 3, 6, and 12 months (P > .05 for all). Marked bursal thickening (>2 mm) was more frequently observed in the EB group (18 of 32 in the LB group and 27 of 32 in the EB group) at 6 months (P = .014).

CONCLUSIONS

EB during arthroscopic rotator cuff repair appears to have no benefit in terms of reducing pain. More adhesions in the subacromial space after EB may result in slower motion recovery, especially in terms of ER. The extent of bursectomy did not affect tendon integrity. However, marked bursal thickening was more frequently observed in the EB group.

LEVEL OF EVIDENCE

Level I, randomized controlled study.

Editorial Commentary: When Less Is More-The Benefits of Limiting Bursectomy in Arthroscopic Rotator Cuff Repair

Although the exact function of the subacromial bursa as it relates to rotator cuff repair is still debatable, most surgeons would agree that the more invasive the procedure, the more likely there will be scarring and/or adhesions, which can lead to decreased motion. So, when performing subacromial bursectomy during rotator cuff repair, "Observe due measure, moderation is best in all things [subacromial]."

Clinical Anatomy for the Innervated Pattern and Boundary of the Subdeltoid Bursa

The aim of this study was to accurately identify the distribution of sensory nerve branches running to bursa with mesoscopic dissection and boundaries following the injection of gelatin into the bursa. Eighteen shoulders of 11 Korean soft cadavers (average age, 65 years; age range, 43 - 88 years) were dissected. The most prominent point of greater tubercle of the humerus (GT) was used as a reference point. The horizontal line passing through GT was used as the x-axis while the vertical line passing through the GT was used as the y-axis. Average distances of the anterior, posterior, superior, and inferior from the GT were 1.9±0.6, 2.4±1.3, 2.1±0.7, and 3.2±1.5 cm, respectively. In 15 cases of 18 shoulders, the anterior branch of the axillary nerve was distributed to the subdeltoid bursa that was running posteriorly. The muscular branch of the anterior and middle parts of the deltoid was distributed to the branch of nerve that was running into the subdeltoid bursa. A branch of the posterior cord of brachial plexus was distributed to the subdeltoid bursa that was running anteriorly in three cases. Most of the branches of the axillary nerve were distributed into the posterolateral area. The branches of the posterior cord of brachial plexus were distributed in the anterolateral area. These results might be useful for preventing residual pain on the anterior shoulder region following an injection for the relief of shoulder pain.