Pathologic evidence of degeneration as a primary cause of rotator cuff tear

The Biological Effect of Platelet-Rich Plasma on Rotator Cuff Tears: A Prospective Randomized In Vivo Study

The positive effect of platelet-rich plasma (PRP) on tendon metabolism has been extensively investigated and proven in vitro. Additionally, in vivo animal studies have correlated the application of PRP with the enhancement of tenocyte anabolic activity in the setting of tendon degeneration. However, less is known about its in vivo effect on human tendon biology. The purpose of the current prospective randomized comparative study was to evaluate the effect of PRP on torn human supraspinatus tendon. Twenty consecutive eligible patients with painful and magnetic resonance imaging (MRI)-confirmed degenerative supraspinatus tendon tears were randomized in a one-to-one ratio into two groups. The patients in the experimental group (n = 10) underwent an ultrasound-guided autologous PRP injection in the subacromial space 6 weeks before the scheduled operation. In the control group (n = 10), no injection was made prior to surgery. Supraspinatus tendon specimens were harvested from the lateral end of the torn tendon during shoulder arthroscopy and were evaluated under optical and electron microscopy. In the control group, a mixed cell population of oval and rounded tenocytes within disorganized collagen and sites of accumulated inflammatory cells was detected. In contrast, the experimental group yielded abundant oval-shaped cells with multiple cytoplasmic processes within mainly parallel collagen fibers and less marked inflammation, simulating the intact tendon structure. These findings indicate that PRP can induce microscopic changes in the ruptured tendon by stimulating the healing process and can facilitate a more effective recovery.

Role of tear size and tendon degeneration for development of pain in rat models of rotator cuff tear

BACKGROUND

Rotator cuff tear (RCT) is a frequent etiology of shoulder pain and disability; however, the triggers for the onset and aggravation of pain remain obscure. In this study, we established novel rat RCT models to examine the impact of tear size and tendon degeneration on pain.

METHODS

Fifty-five adult male Sprague-Dawley rats were allocated into 4 study groups: large tear (L group, n = 10), small tear (S group, n = 15), small tear with scratching (S+ group n = 15), and sham surgery (Sham group, n = 15). Pain-related behaviors were evaluated by weight distribution of forelimbs during a 5-minute free gait using a dynamic weight-bearing apparatus at 2, 4, 6, and 8 weeks. Calcitonin gene-related peptide (CGRP) expressions in ipsilateral dorsal root ganglion (DRG) neurons of C4, C5, and C6 were evaluated at 4 and 8 weeks. The area of scar tissues around the torn tendon, infiltration of inflammatory cells, and severity of tendon degeneration (modified Bonar score) were histologically assessed at 4 and 8 weeks. Additionally, enzyme-linked immunosorbent assay (ELISA) was conducted to evaluate the levels of cyclooxygenase-2 (COX-2) and nerve growth factor (NGF) expression in torn tendons and surrounding tissues at 4 weeks.

RESULTS

The weight distribution ratio (ipsilateral and contralateral side) was significantly decreased in the L and S+ group compared with its baseline and Sham group (P < .05), but the S group showed no significant difference compared with the Sham. The ratio of CGRP-immunoreactive neurons in the DRGs was significantly higher in the L and S+ groups than in the S and Sham groups. The histologic assessment indicated that scar tissue formation was more extensive in the L group than in the S and S+ groups. Still, there was no significant difference between the S and S+ groups. The modified Bonar score was considerably higher in the S+ group than in the S group. Furthermore, ELISA analysis demonstrated no significant disparity in COX-2 levels between the groups; however, NGF levels were substantially higher in the S+ group than in the S and Sham groups.

CONCLUSION

The present study provides compelling evidence that large RCT is strongly associated with heightened pain severity in a rat model. Nevertheless, even a small tear can significantly aggravate pain when the torn tendon is degenerated. CGRP upregulation driven by peripheral NGF possibly played a pivotal role in the genesis and exacerbation of pain in small RCT.

A Pilot Study for Effectiveness and Safety of Adjunctive Pharmacopuncture to Acupuncture Treatment for Rotator Cuff Diseases: A Pragmatic Randomized Controlled Trial

Purpose

Pharmacopuncture therapy has been used in the conservative treatment of rotator cuff disease adjuvant to acupuncture treatment. Despite the increasing utilization of pharmacopuncture therapy, there is still a lack of high-quality research to support its effectiveness. This pilot study aimed to assess the feasibility of pharmacopuncture therapy adjuvant to acupuncture treatment for rotator cuff disease.

Patients and Methods

This was a parallel-grouped, pragmatic randomized controlled, pilot study. Forty patients were randomly allocated to either the experimental or the control group. All patients received acupuncture treatment for four weeks, and pharmacopuncture was additionally administered to the experimental group. After eight treatments were delivered over four weeks, follow-up assessments were performed. The primary outcome was the mean change in the visual analog scale (VAS) score for shoulder pain from baseline to visit 8. Secondary outcomes included shoulder pain and disability index (SPADI) at visits 4, 8, and 9, shoulder range of motion (ROM) at visits 4, 8, and 9, EuroQol 5-Dimension 5-Level questionnaire (EQ-5D-5L) at visits 8 and 9, patient global impression of change (PGIC) at visits 8 and 9, and mean rescue medication consumption at visits 8 and 9.

Results

Both groups showed that each treatment effectively improved rotator cuff disease in most assessments. Particularly, the group that received acupuncture plus pharmacopuncture required fewer rescue medications than the group that received acupuncture alone. However, there was little statistically significant difference between the two groups. There were no serious adverse events experienced by patients in this study.

Conclusion

Although there was little statistical difference between the two groups, the combination of acupuncture and pharmacopuncture for rotator cuff disease was associated with a reduction in the rescue medicine dosage compared with acupuncture alone. Also, it confirmed the safety of pharmacopuncture therapy. This pilot study would help design future research on the effectiveness of pharmacopuncture in rotator cuff disease.

Safety and Efficacy of Wharton's Jelly Connective Tissue Allograft for Rotator Cuff Tears: Findings from a Retrospective Observational Study

With the increasing occurrence of rotator cuff injuries every year, there is a great need for a reliable treatment option. Wharton's Jelly contains several components that can positively impact the replacement and repair of musculoskeletal defects. The overall objective of this study is to evaluate the improvement of patient-reported pain scales after applying Wharton's Jelly (WJ) in rotator cuff defects. Eighty-seven patients with rotator cuff defects who failed at least eight weeks of conservative treatment were selected from the retrospective repository. A total of 2 cc of WJ flowable allograft was applied to the specific affected anatomy, the most common being supraspinatus tendon, biceps tendon insertion, labral tear, and subscapularis tear. No adverse reactions were reported. Statistically significant improvements were found from the initial to Day 90 in all scales. Patient satisfaction was calculated using minimal clinically important differences. No statistically significant differences were found in mean changes between gender, BMI, and age. Scanning electron microscopy images reveal the similarities between the collagen matrix in WJ and the rotator cuff. The significant improvement in patient outcomes coincides with the current literature analyzing WJ applications with other structural defects around the body. WJ is a promising alternative for musculoskeletal defects when the standard of care fails.

Hydrotherapy after Rotator Cuff Repair Improves Short-Term Functional Results Compared with Land-Based Rehabilitation When the Immobilization Period Is Longer

Background: The evidence of hydrotherapy after rotator cuff repair (RCR) is limited as most studies either used it as an adjuvant to standard land-based therapy, or have different initiation timing. This study aimed to compare hydrotherapy and land-based therapy with varying immobilization time. Methods: Patients who underwent RCR with a 10-days or 1-month immobilization duration (early or late rehabilitation) were prospectively randomized. Results: Constant scores significantly differed at three months only, with the best score exhibited by the late hydrotherapy group (70.3 ± 8.2) followed by late land-based (61.0 ± 5.7), early hydrotherapy (55.4 ± 12.8) and early land-based (54.6 ± 13.3) groups (p < 0.001). There was a significant interaction between rehabilitation type and immobilization duration (p = 0.004). The effect of hydrotherapy compared to land-based therapy was large at three months when initiated lately only (Cohen's d, 1.3; 95%CI, 0.9-1.7). However, the relative risk (RR) of postoperative frozen shoulder or retear occurrence for late hydrotherapy was higher compared to early hydrotherapy (RR, 3.9; 95%CI, 0.5-30.0). Conclusions: Hydrotherapy was more efficient compared to land-based therapy at three months only and if initiated lately. Even though initiating hydrotherapy later brought greater constant scores at three months, it might increase the risk of frozen shoulders or retear compared to early hydrotherapy.

Interventions used to mitigate muscle fatty degeneration following the repair of massive rotator cuff tears. A systematic review of animal studies

BACKGROUND

Muscle fatty degeneration following rotator cuff tears has been unequivocally associated with poorer functional outcomes and increased risk for retear following rotator cuff repair. Promising results have emerged from animal studies, with the implementation of various interventions for biologic inhibition of this fatty muscle degeneration. The lack of high quality randomized human evidence on this topic, increases the impact of pooled results from animal literature. The aim of the present study was to systematically review the available published literature for animal studies evaluating the ability of several interventions used to mitigate muscle fatty degeneration following the repair of massive rotator cuff tears.

PATIENTS AND METHODS

A comprehensive search was conducted on Pubmed, Scopus and Google Scholar, covering the period from conception until 16th April 2022. Datasets were stratified based on the type of intervention performed. SYRCLE risk of bias instrument was implemented for quality assessment of the included studies.

RESULTS

Rotator cuff repair augmentation with Adipose derived stem cells (ADSC's), Mesenchymal stem cells (MSC's) and Nandrolone was effective against fatty infiltration, but less effective against muscle atrophy. More beneficial effect was shown by the utilization of Beige adipose tissue - Fibroadipogenic progenitors (BAT-FAP) stimulation, using either Amibregon or BAT-FAPs transplantation. Both provided good results in mitigating muscle atrophy, fatty infiltration and fibrosis.

DISCUSSION

ADSC's, MSC's, Nandrolone and BAT-FAP stimulation may have a role in mitigating muscle fatty degeneration following rotator cuff tears. Large scale human studies are required to further elucidate their role in the clinical setting.

LEVEL OF EVIDENCE

V; systematic review of pre-clinical studies.

Spatially and Temporally Controllable BMP-2 and TGF-β3 Double Release From Polycaprolactone Fiber Scaffolds via Chitosan-Based Polyelectrolyte Coatings

Temporally and spatially controlled growth factor release from a polycaprolactone fiber mat, which also provides a matrix for directional cell colonization and infiltration, could be a promising regenerative approach for degenerated tendon-bone junctions. For this purpose, polycaprolactone fiber mats were coated with tailored chitosan-based nanogels to bind and release the growth factors bone morphogenetic protein 2 (BMP-2) and transforming growth factor-β3 (TGF-β3), respectively. In this work we provide meaningful in vitro data for the understanding of the drug delivery performance and sterilizability of novel implant prototypes in order to lay the foundation for in vivo testing. ELISA-based in vitro release studies were used to investigate the spatial and temporal control of release, as well as the influence of radiation sterilization on protein activity and release behavior. Layer-by-layer coatings based on BMP-2-containing chitosan tripolyphosphate nanogel particles and negatively charged alginate showed a good sustainment of BMP-2 release from chemically modified polycaprolactone fiber mats. Release control improved with increasing layer numbers. The approach of controlling the release via a barrier of cross-linked chitosan azide proved less promising. By using a simple, partial immersion-based dip-coating process, it was possible to apply opposing gradients of the growth factors BMP-2 and TGF-β3. Final radiation sterilization of the growth factor-loaded implant prototypes resulted in a radiation dose-correlated degradation of the growth factors, which could be prevented by lyophilization into protective matrices. For the manufacture of sterile implants, the growth factor loading step must probably be carried out under aseptic conditions. The layer-by-layer coated implant prototypes provided sustained release from opposing gradients of the growth factors BMP-2 and TGF-β3 and thus represent a promising approach for the restoration of tendon-bone defects.

Sirtuin 6 Overexpression Improves Rotator Cuff Tendon-to-Bone Healing in the Aged

Aging is an independent risk factor for recurrent tearing after surgical repair of rotator cuff ruptures around the tendon-to-bone area. However, aging signature factors and related mechanisms involved in the healing of the rotator cuff are still unknown. We hypothesized that differences in proteins involved in the rotator cuff according to age may affect tendon-to-bone healing. The proteome analysis performed to identify the signature aging proteins of the rotator cuff confirmed the sirtuin signal as an age-specific protein. In particular, the expression of SIRT6 was markedly down-regulated with age. Ingenuity pathway analysis of omics data from age-dependent rat rotator cuffs and linear regression from human rotator cuffs showed SIRT6 to be closely related to the Wnt/β-catenin signal. We confirmed that overexpression of SIRT6 in the rotator cuff and primary tenocyte regulated canonical Wnt signaling by inhibiting the transcriptional expression of sclerostin, a Wnt antagonist. Finally, SIRT6 overexpression promoted tendon-to-bone healing after tenotomy with reconstruction in elderly rats. This approach is considered an effective treatment method for recovery from recurrent rotator cuff tears, which frequently occur in the elderly.

Overload in a Rat In Vivo Model of Synergist Ablation Induces Tendon Multiscale Structural and Functional Degeneration

Tendon degeneration is typically described as an overuse injury with little distinction made between magnitude of load (overload) and number of cycles (overuse). Further, in vivo, animal models of tendon degeneration are mostly overuse models, where tendon damage is caused by a high number of load cycles. As a result, there is a lack of knowledge of how isolated overload leads to degeneration in tendons. A surgical model of synergist ablation (SynAb) overloads the target tendon, plantaris, by ablating its synergist tendon, Achilles. The objective of this study was to evaluate the structural and functional changes that occur following overload of plantaris tendon in a rat SynAb model. Tendon cross-sectional area (CSA) and shape changes were evaluated by longitudinal MR imaging up to 8 weeks postsurgery. Tissue-scale structural changes were evaluated by semiquantified histology and second harmonic generation microscopy. Fibril level changes were evaluated with serial block face scanning electron microscopy (SBF-SEM). Functional changes were evaluated using tension tests at the tissue and microscale using a custom testing system allowing both video and microscopy imaging. At 8 weeks, overloaded plantaris tendons exhibited degenerative changes including increases in CSA, cell density, collagen damage area fraction (DAF), and fibril diameter, and decreases in collagen alignment, modulus, and yield stress. To interpret the differences between overload and overuse in tendon, we introduce a new framework for tendon remodeling and degeneration that differentiates between the inputs of overload and overuse. In summary, isolated overload induces multiscale degenerative structural and functional changes in plantaris tendon.

Are the Pathologic Features of Enthesopathy, Tendinopathy, and Labral and Articular Disc Disease Related to Mucoid Degeneration? A Systematic Review

BACKGROUND

Tendinopathy, enthesopathy, labral degeneration, and pathologic conditions of the articular disc (knee meniscus and ulnocarpal) are sometimes described in terms of inflammation or damage, while the histopathologic findings are often consistent with mucoid degeneration. A systematic review of the histopathology of these structures at diverse locations might reconceptualize these diseases as expected aspects of human aging. The potential benefits of this evolution might include healthier patient and clinician mindsets as well as a reduced likelihood of overdiagnosis and overtreatment resulting from greater awareness of base rates of pathology.

QUESTION/PURPOSE

In this systematic review of studies of surgical specimens, we asked: Are there are any differences in the histopathologic findings of structural soft tissue conditions (mucoid degeneration, inflammation, and vascularity) by anatomic site (foot, elbow, or knee) or structure (tendon body, muscle or tendon origin or insertion [enthesis], labrum, or articular disc)?

METHODS

Studies between 1980 and 2021 investigating the histopathologic findings of specimens from surgery for trigger digit, de Quervain tendinopathy, plantar fasciitis, lateral and medial elbow enthesopathy, rotator cuff tendinopathy, posterior tibial tendinopathy, patellar tendinopathy, Achilles tendinopathy, or disease of the hip labrum, ulnocarpal articular disc, or knee meniscus were searched for in the PubMed, EMBASE, and CINAHL databases. Inclusion criteria were the prespecified anatomic location or structure being analyzed histologically and any findings described with respect to inflammation, vascularity, or mucoid degeneration. Studies were excluded if they were nonhuman studies or review articles. Search terms included "anatomy," "pathology," and "histopathology." These terms were coupled with anatomic structures or disorders and included "trigger finger," "de Quervain," "fasciitis, plantar," "tennis elbow," "rotator cuff tendinopathy," "elbow tendinopathy," "patellar tendonitis," "posterior tibial tendon," and "triangular fibrocartilage." This resulted in 3196 studies. After applying the inclusion criteria, 559 articles were then assessed for eligibility according to our exclusion criteria, with 52 eventually included. We recorded whether the study identified the following histopathologic findings: inflammatory cells or molecular markers, greater than expected vascularity (categorized as quantitative count, with or without controls; molecular markers; or qualitative judgments), and features of mucoid degeneration (disorganized collagen, increased extracellular matrix, or chondroid metaplasia). In the absence of methods for systematically evaluating the pathophysiology of structural (collagenous) soft tissue structures and rating histopathologic study quality, all studies that interpreted histopathology results were included. The original authors' judgment regarding the presence or absence of inflammation, greater than expected vascularity, and elements of mucoid degeneration was recorded along with the type of data used to reach that conclusion.

RESULTS

Regarding differences in the histopathology of surgical specimens of structural soft tissue conditions by anatomic site, there were no differences in inflammation or mucoid degeneration, and the knee meniscus was less often described as having greater than normal vascularity. There were no differences by anatomic structure. Overall, 20% (10 of 51) of the studies that investigated for inflammation reported it (nine inflammatory cells and one inflammatory marker). Eighty-three percent (43 of 52) interpreted increased vascularity: 40% (17 of 43) using quantitative methods (14 with controls and three without) and 60% (26 of 43) using imprecise criteria. Additionally, 100% (all 52 studies) identified at least one element of mucoid degeneration: 69% (36 of 52) reported an increased extracellular matrix, 71% (37 of 52) reported disorganized collagen, and 33% (17 of 52) reported chondroid metaplasia.

CONCLUSION

Our systematic review of the histopathology of diseases of soft tissue structures (enthesopathy, tendinopathy, and labral and articular disc) identified consistent mucoid degeneration, minimal inflammation, and imprecise assessment of relative vascularity; these findings were consistent across anatomic sites and structures, supporting a reconceptualization of these diseases as related to aging (senescence or degeneration) rather than injury or activity.

CLINICAL RELEVANCE

This reconceptualization supports accommodative mindsets known to be associated with greater comfort and capability. In addition, awareness of the notable base rates of structural soft tissue changes as people age might reduce overdiagnosis and overtreatment of incidental, benign, or inconsequential signal changes and pathophysiology.

Histological, radiological and clinical analysis of the supraspinatus tendon and muscle in rotator cuff tears

BACKGROUND

Macroscopic alterations of the affected rotator cuff (RC) are undoubtedly linked to microscopic changes, but they may underestimate the actual degree of the disease. Moreover, it remains unclear whether preoperative structural RC changes may alter clinical outcomes.

METHODS

Supraspinatus tendon and muscle samples were collected from 47 patients undergoing RC surgery. Tendons were evaluated histologically according to the Bonar score; fatty infiltration and muscle atrophy were quantified using a software for biomedical image analysis (ImageJ) in percentage of area affected in the observed muscle section. Preoperative shoulder ROM and pain were evaluated. Radiological muscle atrophy was evaluated with the Tangent Sign and Occupation Ratio; fatty infiltration was assessed according to the Goutallier classification. Correlations between histological, radiological and clinical outcomes were assessed. Statistics were performed using the Spearman correlation coefficient. Intraobserver and interobserver agreement was calculated.

RESULTS

Histopathologic fatty infiltration (r = 0.007, p = 0.962), muscle atrophy (r = 0.003, p = 0.984) and the total Bonar score (r = 0.157, p = 0.292) were not correlated to preoperative shoulder pain. Muscle atrophy showed a significant but weak negative correlation with the preoperative movement of abduction (r = -0.344, p = 0.018). A significant but weak positive correlation was found between muscle atrophy and the total Bonar score (r = 0.352, p = 0.015). No correlation between histological and radiological evaluation was found for both fatty infiltration (r = 0.099, p = 0.510) and muscle atrophy (Tangent Sign: r = -0.223, p = 0.131; Occupation Ratio: r = -0.148, p = 0.319). Our histological evaluation showed a modal value of 3 (out of 3) for fatty infiltration and an equal modal value of 2 and 3 (out of 3) for muscle atrophy. In contrast, the modal value of the Goutallier score was 1 (out of 4) and 28 patients out of 47 showed a negative Tangent sign. At histology, intraobserver agreement ranged from 0.59 to 0.81 and interobserver agreement from 0.57 to 0.64. On the MRI intraobserver agreement ranged from 0.57 to 0.71 and interobserver agreement ranged from 0.53 to 0.65.

CONCLUSIONS

Microscopic muscle atrophy appeared to negatively correlate with the movement of abduction leading to functional impairment. Shoulder pain did not show any relationship with microscopic changes. Radiological evaluation of the supraspinatus muscle alterations seemed to underestimate the degree of the same abnormalities evaluated at histology.

Ultrasound-guided versus landmark-guided subacromial corticosteroid injections for rotator cuff related shoulder pain: A systematic review of randomised controlled trials

INTRODUCTION

Rotator cuff related shoulder pain (RCRSP) is the most common presentation of shoulder pain within physiotherapy. Corticosteroid injections (CSI) have become increasingly popular to reduce pain, increase range of motion (ROM) and improve shoulder function. Evidence around the use of ultrasound-guided (USG) versus landmark-guided (LMG) CSIs remains controversial.

OBJECTIVE

The objective of this appraisal was to compare the effectiveness of each approach in the management of RCRSP.

METHODS

Cochrane, PubMed and CINAHL electronic databases were searched (from January 2014 to February 2021). Randomised controlled trials (RCTs) were included comparing USG to LMG CSIs for RCRSP. An independent reviewer selected the studies, extracted and synthesised the data. Two reviewers carried out a quality appraisal. Outcome measures were pain, function and ROM.

RESULTS

Four RCTs (n = 179 participants, n = 184 shoulders) were reviewed. Both USG and LMG groups showed statistically significant within group improvements in clinical outcomes. There were no significant differences between groups. Three studies were identified as being a 'low' risk of bias (RoB) and did not favour the use of ultrasound. One study did favour the use of ultrasound for improving function, although it was found to have 'high' RoB. Adverse events were seldom reported.

CONCLUSION

There is limited evidence to suggest using USG CSIs has a superior effect on clinical outcomes compared to LMG, though small sample sizes and lack of long-term follow-up limit the generalisability of the findings.

A predictive model for the critical shoulder angle based on a three-dimensional analysis of scapular angular and linear morphometrics

BACKGROUND

The purpose of this study was to define the features of scapular morphology that are associated with changes in the critical shoulder angle (CSA) by developing the best predictive model for the CSA based on multiple potential explanatory variables, using a completely 3D assessment.

METHODS

3D meshes were created from CT DICOMs using InVesalius (Vers 3.1.1, RTI [Renato Archer Information Technology Centre], Brazil) and Meshmixer (3.4.35, Autodesk Inc., San Rafael, CA). The analysis included 17 potential angular, weighted linear and area measurements. The correlation of the explanatory variables with the CSA was investigated with the Pearson's correlation coefficient. Using multivariable linear regression, the approach for predictive model-building was leave-one-out cross-validation and best subset selection.

RESULTS

Fifty-three meshes were analysed. Glenoid inclination (GI) and coronal plane angulation of the acromion (CPAA) [Pearson's r: 0.535; -0.502] correlated best with CSA. The best model (adjusted R-squared value 0.67) for CSA prediction contained 10 explanatory variables including glenoid, scapular spine and acromial factors. CPAA and GI were the most important based on their distribution, estimate of coefficients and loss in predictive power if removed.

CONCLUSIONS

The relationship between scapular morphology and CSA is more complex than the concept of it being dictated solely by GI and acromial horizontal offset and includes glenoid, scapular spine and acromial factors of which CPAA and GI are most important. A further investigation in a closely defined cohort with rotator cuff tears is required before drawing any clinical conclusions about the role of surgical modification of scapular morphology.

LEVEL OF EVIDENCE

Level 4 retrospective observational cohort study with no comparison group.

Clinical perspectives for repairing rotator cuff injuries with multi-tissue regenerative approaches

Background

In the musculoskeletal system, bone, tendon, and muscle form highly integrated multi-tissue units such as the rotator cuff complex, which facilitates functional and dynamic movement of the shoulder joint. Understanding the intricate interplay among these tissues within clinical, biological, and engineering contexts is vital for addressing challenging issues in treatment of musculoskeletal disorders and injuries.

Methods

A wide-ranging literature search was performed, and findings related to the socioeconomic impact of rotator cuff tears, the structure-function relationship of rotator cuff bone-tendon-muscle units, pathophysiology of injury, current clinical treatments, recent state-of-the-art advances (stem cells, growth factors, and exosomes) as well as their regulatory approval, and future strategies aimed at engineering bone-tendon-muscle musculoskeletal units are outlined.

Results

Rotator cuff injuries are a significant socioeconomic burden on numerous healthcare systems that may be addressed by treating the rotator cuff as a single complex, given its highly integrated structure-function relationship as well as degenerative pathophysiology and limited healing in bone-tendon-muscle musculoskeletal tissues. Current clinical practices for treating rotator cuff injuries, including the use of commercially available devices and evolving trends in surgical management have benefited patients while advances in application of stem/progenitor cells, growth factors, and exosomes hold clinical potential. However, such efforts do not emphasize targeted regeneration of bone-tendon-muscle units. Strategies aimed at regenerating bone-tendon-muscle units are thus expected to address challenging issues in rotator cuff repair.

Conclusions

The rotator cuff is a highly integrated complex of bone-tendon-muscle units that when injured, has severe consequences for patients and healthcare systems. State-of-the-art clinical treatment as well as recent advances have resulted in improved patient outcome and may be further enhanced by engineering bone-tendon-muscle multi-tissue grafts as a potential strategy for rotator cuff injuries.

Translational Potential of this Article

This review aims to bridge clinical, tissue engineering, and biological aspects of rotator cuff repair and propose a novel therapeutic strategy by targeted regeneration of multi-tissue units. The presentation of these wide-ranging and multi-disciplinary concepts are broadly applicable to regenerative medicine applications for musculoskeletal and non-musculoskeletal tissues.

Evaluation of SS-31 as a Potential Strategy for Tendinopathy Treatment: An In Vitro Model

BACKGROUND

Studies in our laboratory have demonstrated mitochondrial dysfunction in human and animal models of supraspinatus tendinopathy. SS-31 (elamipretide) has been reported to improve mitochondrial function and to be effective in clinical trials for several diseases. The potential of SS-31 in treating tendinopathy has not been explored.

HYPOTHESIS

SS-31 would improve mitochondrial function in human tenocytes sampled from patients with tendinopathy.

STUDY DESIGN

Controlled laboratory study.

METHODS

Healthy tenocytes were obtained from normal hamstring tendon biopsy specimens in 9 patients undergoing anterior cruciate ligament reconstruction, and tenocytes were collected from degenerative supraspinatus tendon biopsy specimens in 9 patients undergoing rotator cuff repair. Tenocytes were cultured, used at passage 1, and assigned to 4 groups: healthy tenocytes, healthy tenocytes with 1μM SS-31 treatment for 72 hours, degenerative tenocytes, and degenerative tenocytes with 1μM SS-31 treatment for 72 hours. The outcomes included measurements of mitochondrial potential, mitochondrial morphology by transmission electron microscopy imaging, reactive oxygen species and superoxidative dismutase activity, gene expression, and cell viability.

RESULTS

An increase in the cell fraction with depolarized mitochondria was found in degenerative tenocytes (P = .014), followed by a decrease after SS-31 treatment (P = .018). Transmission electron microscopy images demonstrated morphological changes with a decreased number and size of mitochondria per cell in the degenerative tenocytes (P = .018) and with improvement after SS-31 treatment. There was no significant difference in the level of reactive oxygen species between healthy and degenerative tenocytes in culture, but superoxidative dismutase activity was significantly decreased in the degenerative group (P = .006), which then increased after SS-31 treatment (P = .012). These findings suggested that mitochondrial dysfunction may be reversed by SS-31 treatment. The gene expression of matrix metalloproteinase-1 (matrix remodeling, P = .029) and fatty acid-binding protein 4 (fatty infiltration, P = .046) was significantly upregulated in the degenerative tenocytes and reduced by SS-31 treatment (P = .048; P = .007). Gene expression for hypoxia-inducible factor1 α and the proapoptotic regulator Bcl-2-associated X protein was increased in the degenerative tenocytes. There was a significant decrease in cell viability in degenerative tenocytes as compared with the healthy tenocytes, with small improvement after treatment with SS-31.

CONCLUSION

There are changes in mitochondrial structure and function in tenocytes derived from degenerative tendons, and SS-31, as a mitochondrial protectant, could improve mitochondrial function and promote the healing of tendinopathy.

CLINICAL RELEVANCE

Mitochondrial dysfunction appears to play a role in the development of tendinopathy, and SS-31, as a mitochondrial protective agent, may be a therapeutic agent in the treatment of tendinopathy.

Rotator Cuff Repair with Graft Augmentation Improves Function, Decreases Revisions, and Is Cost-Effective

PURPOSE

The purpose of this study is to evaluate the cost effectiveness of the use of extracellular matrix (ECM) augment at the time of primary rotator cuff repair utilizing a decision tree analysis.

METHODS

A decision tree model was created utilizing the existing literature for retear rates with and without dermal graft augmentation. Costs for rotator cuff repair (hospital and surgeon fees) were based on published studies and the cost for graft augmentation was based on institutional data. Utility measures were based upon EQ-5D (European Quality of Life 5 Dimension) scores to assess for improvement in quality adjusted life years (QALY) over a 10-year postoperative period with and without graft augmentation. Cost effectiveness was assessed using the incremental cost effectiveness ratio (ICER), or the incremental cost for per QALY with graft augmentation. Cost effectiveness is based on previous literature whereby an intervention is considered cost effective if the ICER is less than $50,000/QALY.

RESULTS

On the basis of our decision tree analysis, total cost for rotator cuff tear without augmentation was $12,763, while the cost increased to $16,039 with ECM augmentation. With graft augmentation there was an improvement in 2.29 QALY, while there was an improvement of 2.05 without graft augmentation. The ICER of graft augmentation is $14,000/QALY, well below the cost effectiveness cut-off of $50,000/QALY. Sensitivity analysis showed the maximum cost of the ECM augment to be cost effective is $11,921.

CONCLUSION

Graft augmentation does come with a significant upfront cost; however, on the basis of our decision-tree analysis, it may represent a cost-effective procedure. There is evidence to potentially consider more routine use in rotator cuff repairs, while being cost effective.

LEVEL OF EVIDENCE

Economic: Level IV: computer simulation model (Monte Carlo simulation, Markov model) with inputs derived from Level IV studies.

Relationship of superoxide dismutase to rotator cuff injury/tear in a rat model

Rotator cuff degeneration is one of the several factors that lead to rotator cuff tears. Oxidative stress and superoxide dismutase have been reported to be related to rotator cuff degeneration; however, the precise mechanism still remains unclear. In this study, we investigated the relationship of oxidative stress and superoxide dismutase to the degeneration of the rotator cuff using rat models. Eighty-four rats were used to create a collagenase-induced rotator cuff injury model (injury model) and a rotator cuff tear model (tear model). The controls were administered saline and had only a deltoid incision, respectively. We evaluated degeneration morphology of the rotator cuff using a degeneration score; dihydroethidium fluorescence intensity, which detects oxidative stress; gene expression; and superoxide dismutase activity. The rotator cuffs in the injury and tear models significantly increased degeneration scores and dihydroethidium fluorescence intensity. On the other hand, gene expression of superoxide dismutase isoform, superoxide dismutase 1, and superoxide dismutase activity were significantly decreased in the injury model but showed no significant difference in the tear model. These findings suggested that superoxide dismutase might not be associated with rotator cuff degeneration after tear but may be involved in degenerative rotator cuff without tear. However, we found that rotator cuff degeneration involves oxidative stress both with and without tear. Based on these findings, it is presumed that different treatments may be appropriate, depending on the state of rotator cuff degeneration, because the mechanisms of the degeneration may be different.

Influence of Diabetes-Induced Glycation and Oxidative Stress on the Human Rotator Cuff

Most shoulder rotator cuff tears (RCTs) are caused by non-traumatic age-related rotator cuff degeneration, of which hyperglycemia is a risk factor due to its glycation reaction and oxidative stress. We aimed to identify the influence of diabetes-induced glycation and oxidative stress in patients with non-traumatic shoulder RCTs. Twenty patients, aged over 50 years, with non-traumatic shoulder RCTs participated in this study. Patients with a history of diabetes mellitus or preoperative HbA1c ≥ 6.5% were assigned to the diabetic group (n = 10), and the rest to the non-diabetic group (n = 10). Cell proliferation; expression of genes related to oxidative stress, glycation reaction, inflammation, and collagen; intracellular reactive oxygen species (ROS) levels; and apoptosis rates were analyzed. The diabetic group had significantly lower cell proliferation than the non-diabetic group. In the diabetic group, the mRNA expression levels of NOX1, NOX4, IL6, RAGE, type III collagen, MMP2, TIMP1, and TIMP2 were significantly higher; type I collagen expression was significantly lower; and the rate of ROS-positive cells and apoptotic cells, as well as the expression of advanced glycation end-products (AGEs) and the receptor for AGEs (RAGE), was significantly higher. In conclusion, hyperglycemia caused by diabetes mellitus increased AGE and RAGE expression, and led to increased NOX expression, ROS production, and apoptosis in the human rotator cuff. This provides scope to find a preventive treatment for non-traumatic RCTs by inhibiting glycation and oxidative stress.

The Relationship of Aging and Smoking With Rotator Cuff Disease: A Systematic Review and Meta-analysis

OBJECTIVE

Despite rotator cuff disease being one of the most common causes of shoulder pain, its pathogenesis and biology are poorly understood. In this study, we synthesized evidence from studies reporting associations for aging and smoking status in relation to rotator cuff disease.

DESIGN

A systematic review was performed using multiple databases (PubMed, Embase, Cochrane, CINAHL, and Science Direct). Articles that met our eligibility criteria and presented data on the association between aging and/or smoking status and rotator cuff disease were included. We performed meta-analyses and reported cumulative effects using odds ratios and corresponding 95% confidence intervals.

RESULTS

Of the 212 articles eligible for full-text review, seven studies reported on the relationship between aging and rotator cuff disease, and 10 studies reported on the relationship between smoking and rotator cuff disease. Aging was consistently associated with increased odds of having rotator cuff disease when assessed continuously (per 10-yr increase: odds ratio = 1.20, 95% confidence interval = 1.18-1.21) or categorically (ages <40 yrs vs: [a] 40-44 yrs [odds ratio = 2.71, 95% confidence interval = 1.78-4.13], [b] 45-49 yrs [odds ratio = 4.33, 95% confidence interval = 2.88-6.55], and [c] ≥50 yrs [odds ratio = 6.97, 95% confidence interval = 4.85-10.01]). Assessing studies that reported smoking status as current smokers versus nonsmokers, current smokers were more likely to have rotator cuff disease (odds ratio = 1.94, 95% confidence interval = 1.52-2.48). However, a statistically significant association was not found when never smokers were compared with former smokers (odds ratio = 1.08, 95% confidence interval = 0.97-1.20) and to current smokers (odds ratio = 0.97, 95% confidence interval = 0.87-1.07).

CONCLUSIONS

In this systematic review and meta-analysis, increasing age was a strong risk factor for rotator cuff disease. The finding that current smokers are more likely to have rotator cuff disease as compared with nonsmokers implies that cessation of smoking can potentially lead to mitigation of this risk factor.

Roles of Oxidative Stress in Acute Tendon Injury and Degenerative Tendinopathy-A Target for Intervention

Both acute and chronic tendon injuries are disabling sports medicine problems with no effective treatment at present. Sustained oxidative stress has been suggested as the major factor contributing to fibrosis and adhesion after acute tendon injury as well as pathological changes of degenerative tendinopathy. Numerous in vitro and in vivo studies have shown that the inhibition of oxidative stress can promote the tenogenic differentiation of tendon stem/progenitor cells, reduce tissue fibrosis and augment tendon repair. This review aims to systematically review the literature and summarize the clinical and pre-clinical evidence about the potential relationship of oxidative stress and tendon disorders. The literature in PubMed was searched using appropriate keywords. A total of 81 original pre-clinical and clinical articles directly related to the effects of oxidative stress and the activators or inhibitors of oxidative stress on the tendon were reviewed and included in this review article. The potential sources and mechanisms of oxidative stress in these debilitating tendon disorders is summarized. The anti-oxidative therapies that have been examined in the clinical and pre-clinical settings to reduce tendon fibrosis and adhesion or promote healing in tendinopathy are reviewed. The future research direction is also discussed.

Supraspinatus tendon thickness and subacromial impingement characteristics in younger and older adults

Background

Subacromial impingement (SAI) may be a cause of age-related rotator cuff abnormalities; therefore, the purpose of this study was to compare SAI characteristics between younger and older adults. In addition to the fact that thickened supraspinatus tendon (SST) indicates tendon abnormalities, SAI characteristics have been recognized as follows: greater SST thickness, reduced acromiohumeral distance (AHD), greater reduction of AHD (∆AHD) with arm elevation, and a higher percentage of SST within AHD (i.e., occupation ratio: OcAHD). Furthermore, we investigated the relationships between SST thickness and AHD, as well as SST thickness and ∆AHD to clarify the effect of SAI on rotator cuff abnormalities.

Methods

Healthy younger (n = 18, 21–24-year-old) and older (n = 27, 45–80-year-old) adults without any shoulder symptoms participated in this study. We measured their SST thickness and AHD at rest and at arm elevation (30° and 60°) in the scapular plane using ultrasound, and calculated ∆AHD as the relative change expressed as a percentage of the baseline. OcAHD was expressed as the ratio of SST thickness at rest to AHD at rest and in elevated positions.

Results

The older subjects had approximately one mm thicker SST (P = 0.003, 95% Confidence interval [CI] = 0.410 to 1.895) and approximately 1.0 to 1.3 mm greater AHD than the younger subjects (P = 0.011, 95%CI = 0.284 to 2.068 at rest; P = 0.037, 95%CI = 0.082 to 2.609 for 30° of arm elevation; P = 0.032, 95%CI = 0.120 to 2.458 for 60° of arm elevation). However, there were no differences in ΔAHD and OcAHD between the groups.

Conclusion

This study demonstrated that, compared with the younger subjects, the older subjects showed thicker supraspinatus tendon but no other SAI characteristics including decreases in AHD and increases in OcAHD. Thus, this study suggests that older subjects showed age-related SST abnormalities without SAI, although the magnitude of the differences in SST thickness is notably small and the clinical significance of this difference is unclear.

Effects of leukocyte-rich platelet-rich plasma and leukocyte-poor platelet-rich plasma on the healing of bone-tendon interface of rotator cuff in a mice model

Platelet-rich plasma (PRP) is widely used clinically to treat tendon injuries, and often contains leukocytes. However, the debate regarding the concentration of leukocytes in PRP is still ongoing. This study aimed to evaluate the therapeutic effects of leukocyte-rich platelet-rich plasma (LR-PRP) and leukocyte-poor platelet-rich plasma (LP-PRP) on the healing of the bone-tendon interface (BTI) of the rotator cuff. A total of 102 C57BL/6 mice were used. Thirty mice were used to prepare the PRP, while 72 underwent acute supraspinatus tendon injury repair. The animals were then randomly assigned to three groups: LR-PRP, LP-PRP and control groups. The mice were euthanized at 4 and 8 weeks postoperatively, and histological, immunological and biomechanical analyses were performed. The histological results showed that the fusion effect at the bone-tendon interface at 4 and 8 weeks after surgery was greater in the PRP groups and significantly increased at 4 weeks; however, at 8 weeks, the area of the fibrocartilage layer in the LP-PRP group increased significantly. M2 macrophages were observed at the repaired insertion for all the groups at 4 weeks. At 8 weeks, M2 macrophages withdrew back to the tendon in the control group, but some M2 macrophages were retained at the repaired site in the LR-PRP and LP-PRP groups. Enzyme-linked immunoassay results showed that the concentrations of IL-1β and TNF-α in the LR-PRP group were significantly higher than those in the other groups at 4 and 8 weeks, while the concentrations of IL-1β and TNF-α in the LP-PRP group were significantly lower than those in the control group. The biomechanical properties of the BTI were significantly improved in the PRP group. Significantly higher failure load and ultimate strength were seen in the LR-PRP and LP-PRP groups than in the control group at 4 and 8 weeks postoperatively. Thus, LR-RPR can effectively enhance the early stage of bone-tendon interface healing after rotator cuff repair, and LP-PRP could enhance the later stages of healing after rotator cuff injury.

Accuracy of Critical Shoulder Angle and Acromial Index for Predicting Supraspinatus Tendinopathy

Critical shoulder angle (CSA) is the angle between the superior and inferior bony margins of the glenoid and the most lateral border of the acromion. The acromial index (AI) is the distance from the glenoid plane to the acromial lateral border and is divided by the distance from the glenoid plane to the lateral aspect of the humeral head. Although both are used for predicting shoulder diseases, research on their accuracy in predicting supraspinatus tendinopathy in patients with shoulder pain is limited. Data were retrospectively collected from 308 patients with supraspinatus tendinopathy between January 2018 and December 2019. Simultaneously, we gathered the data of 300 patients with shoulder pain without supraspinatus tendinopathy, confirmed through ultrasound examination. Baseline demographic data, CSA, and AI were compared using the independent Student’s t test and Mann–Whitney U test. Categorical variables were analyzed using the chi-square test. A receiver operating characteristic curve (ROC) analysis was performed to investigate the accuracy of CSA and AI for predicting supraspinatus tendinopathy, and the optimal cut-off point was determined using the Youden index. No statistical differences were observed for age, sex, body mass index, evaluated side (dominant), diabetes mellitus, and hyperlipidemia between the groups. The supraspinatus tendinopathy group showed higher CSAs (p < 0.001) than did the non-supraspinatus tendinopathy group. For predicting supraspinatus tendinopathy, the area under the curve (AUC) of ROC curve of the CSA was 76.8%, revealing acceptable discrimination. The AUC of AI was 46.9%, revealing no discrimination. Moreover, when patients with shoulder pain had a CSA > 38.11°, the specificity and sensitivity of CSA in predicting supraspinatus tendinopathy were 71.0% and 71.8%, respectively. CSA could be considered an objective assessment tool to predict supraspinatus tendinopathy in patients with shoulder pain. AI revealed no discrimination in predicting supraspinatus tendinopathy in patients with shoulder pain.

Protocatechuic acid impacts rotator cuff healing and reduces fatty degeneration in a chronic rotator cuff tear model in rats

Background

The purpose of this study was to verify the effect of protocatechuic acid (PCA) on tendon healing and fatty degeneration in a chronic rotator cuff model.

Methods

Twenty-eight Sprague-Dawley male rats were randomly allocated into two groups: Saline+repair (SR) and PCA+repair (PR). The right shoulder was used for experimental interventions, and the left served as a control. PCA (30 mg/kg/day) was administered intraperitoneally at the site of infraspinatus tendon detachment in rats in the PR group, and the same volume of saline was administered to the same site in the SR group. The torn tendon was repaired 4 weeks after infraspinatus detachment. Four weeks after repair, hematoxylin and eosin (H&E), S100, and CD68 stains were performed to evaluate the degree of fatty degeneration and H&E and Masson trichrome stains were performed to assess tendon healing. Superoxide dismutase (SOD) was measured to test the efficacy of PCA as an antioxidant.

Results

Results from histological evaluation indicated that SOD and CD68 levels at the musculotendinous region and collagen fiber parallel to the orientation at the tendon-to-bone junction were not significantly different between the SR and PR groups. The mean load-to-failure of the PR group (20.32±9.37 N) was higher than that of the SR group (16.44±6.90 N), although this difference was not statistically significant (p=0.395). The SOD activity in the operative side infraspinatus muscle of the PR group was higher than that of the SR group, but the difference was not statistically significant (p=0.053).

Conclusions

The use of PCA could improve tendon healing and decrease fatty degeneration after rotator cuff repair.

Three-dimensional muscle loss assessment: a novel computed tomography-based quantitative method to evaluate rotator cuff muscle fatty infiltration

BACKGROUND

Rotator cuff fatty infiltration (FI) is one of the most important parameters to predict the outcome of certain shoulder conditions. The primary objective of this study was to define a new computed tomography (CT)-based quantitative 3-dimensional (3D) measure of muscle loss (3DML) based on the rationale of the 2-dimensional (2D) qualitative Goutallier score. The secondary objective of this study was to compare this new measurement method to traditional 2D qualitative assessment of FI according to Goutallier et al and to a 3D quantitative measurement of fatty infiltration (3DFI).

MATERIALS AND METHODS

102 CT scans from healthy shoulders (46) and shoulders with cuff tear arthropathy (21), irreparable rotator cuff tears (18), and primary osteoarthritis (17) were analyzed by 3 experienced shoulder surgeons for subjective grading of fatty infiltration according to Goutallier, and their rotator cuff muscles were manually segmented. Quantitative 3D measurements of fatty infiltration (3DFI) were completed. The volume of muscle fibers without intramuscular fat was then calculated for each rotator cuff muscle and normalized to the patient's scapular volume to account for the effect of body size (NV_fibers). 3D muscle mass (3DMM) was calculated by dividing the NV_fibers value of a given muscle by the mean expected volume in healthy shoulders. 3D muscle loss (3DML) was defined as 1 - (3DMM). The correlation between Goutallier grading, 3DFI, and 3DML was compared using a Spearman rank correlation.

RESULTS

Interobserver reliability for the traditional 2D Goutallier grading was moderate for the infraspinatus (ISP, 0.42) and fair for the supraspinatus (SSP, 0.38), subscapularis (SSC, 0.27) and teres minor (TM, 0.27). 2D Goutallier grading was found to be significantly and highly correlated with 3DFI (SSP, 0.79; ISP, 0.83; SSC, 0.69; TM, 0.45) and 3DML (SSP, 0.87; ISP, 0.85; SSC, 0.69; TM, 0.46) for all 4 rotator cuff muscles (P < .0001). This correlation was significantly higher for 3DML than for the 3DFI for SSP only (P = .01). The mean values of 3DFI and 3DML were 0.9% and 5.3% for Goutallier 0, 2.9% and 25.6% for Goutallier 1, 11.4% and 49.5% for Goutallier 2, 20.7% and 59.7% for Goutallier 3, and 29.3% and 70.2% for Goutallier 4, respectively.

CONCLUSION

The Goutallier score has been helping surgeons by using 2D CT scan slices. However, this grading is associated with suboptimal interobserver agreement. The new measures we propose provide a more consistent assessment that correlates well with Goutallier's principles. As 3DML measurements incorporate atrophy and fatty infiltration, they could become a very reliable index for assessing shoulder muscle function. Future algorithms capable of automatically calculating the 3DML of the cuff could help in the decision process for cuff repair and the choice of anatomic or reverse shoulder arthroplasty.

Full-Thickness Rotator Cuff Tears Can Be Safely Treated With a Resorbable Bioinductive Bovine Collagen Implant: One-Year Results of a Prospective, Multicenter Registry

Purpose

The purpose of this study was to prospectively collect safety and efficacy data in a large group of patients undergoing arthroscopic repair of full-thickness rotator cuff tears augmented with a resorbable bioinductive bovine collagen implant designed to promote healing.

Methods

Seventeen centers across the United States enrolled patients in an institutional review board-approved registry to collect outcomes data on the implant. Patients undergoing surgical management of full-thickness rotator cuff tears augmented with the implant were enrolled. Inclusion criteria were age of ≥21 years, willingness to participate and the ability to read and speak English. Exclusion criteria included hypersensitivity to bovine-derived products. Patients were assessed before and after surgery at up to 1 year with outcomes including the single-assessment numeric evaluation (SANE), Veterans RAND 12-Item (VR-12) mental components and physical components (VR-12 PCS), American Shoulder and Elbow Surgeons (ASES), and Western Ontario Rotator Cuff (WORC) outcome measures. Ad hoc analyses were performed to compare these outcomes at all time points depending on tear size (small/medium vs large/massive). Serious complications were collected.

Results

Of 210 patients enrolled, 192 had 1-year follow-up data available. The patients experienced statistically significant improvement between baseline and 1 year for mean SANE, VR-12 PCS, ASES, and WORC scores (40.0-82.0, 33.5-47.3, 46.2-87.8, and 36.2-81.0, respectively; P < .001 for all results). Ad-hoc analysis demonstrated that similar results were obtained at 1 year regardless of tear size. Twenty patients (10.4%) experienced serious complications (10.4%), including revision surgery (n = 18), proximal humerus fracture/partial subscapularis tear resulting from multiple falls (n = 1), and adhesive capsulitis (n = 1).

Conclusions

The safety and efficacy of a bioinductive implant in the surgical management of full-thickness rotator cuff tears at 1 year was shown in this study. Implant efficacy appears to be comparable regardless of the underlying tear size.

Level of Evidence

Level IV, therapeutic case series.

Screening of key biomarkers of tendinopathy based on bioinformatics and machine learning algorithms

Tendinopathy is a complex multifaceted tendinopathy often associated with overuse and with its high prevalence resulting in significant health care costs. At present, the pathogenesis and effective treatment of tendinopathy are still not sufficiently elucidated. The purpose of this research is to intensely explore the genes, functional pathways, and immune infiltration characteristics of the occurrence and development of tendinopathy. The gene expression profile of GSE106292, GSE26051 and GSE167226 are downloaded from GEO (NCBI comprehensive gene expression database) and analyzed by WGCNA software bag using R software, GSE26051, GSE167226 data set is combined to screen the differential gene analysis. We subsequently performed gene enrichment analysis of Gene Ontology (GO) and "Kyoto Encyclopedia of Genes and Genomes" (KEGG), and immune cell infiltration analysis. By constructing the LASSO regression model, Support vector machine (SVM-REF) and Gaussian mixture model (GMMs) algorithms are used to screen, to identify early diagnostic genes. We have obtained a total of 171 DEGs through WGCNA analysis and differentially expressed genes (DEGs) screening. By GO and KEGG enrichment analysis, it is found that these dysregulated genes were related to mTOR, HIF-1, MAPK, NF-κB and VEGF signaling pathways. Immune infiltration analysis showed that M1 macrophages, activated mast cells and activated NK cells had infiltration significance. After analysis of THE LASSO SVM-REF and GMMs algorithms, we found that the gene MACROD1 may be a gene for early diagnosis. We identified the potential of tendon disease early diagnosis way and immune gene regulation MACROD1 key infiltration characteristics based on comprehensive bioinformatics analysis. These hub genes and functional pathways may as early biomarkers of tendon injuries and molecular therapy level target is used to guide drug and basic research.

Supraspinatus-to-Glenoid Contact Occurs During Standardized Overhead Reaching Motion

Background:

Rotator cuff tears may result from repeated mechanical deformation of the cuff tendons, and internal impingement of the supraspinatus tendon against the glenoid is one such proposed mechanism of deformation.

Purpose:

To (1) describe the changing proximity of the supraspinatus tendon to the glenoid during a simulated overhead reaching task and (2) determine the relationship between scapular morphology and this proximity. Additionally, the patterns of supraspinatus-to-glenoid proximity were compared with previously described patterns of supraspinatus-to-coracoacromial arch proximity.

Study Design:

Descriptive laboratory study.

Methods:

Shoulder models were created from magnetic resonance images of 20 participants. Standardized kinematics were imposed on the models to simulate functional reaching, and the minimum distances between the supraspinatus tendon and the glenoid and the supraspinatus footprint and the glenoid were calculated every 5° between 0° and 150° of humerothoracic elevation. The angle at which contact between the supraspinatus and the glenoid occurred was documented. Additionally, the relationship between glenoid morphology (version and inclination) and the contact angle was evaluated. Descriptive statistics were calculated for the minimum distances, and glenoid morphology was assessed using Pearson correlation coefficients and simple linear regressions.

Results:

The minimum distances between the tendon and the glenoid and between the footprint and the glenoid decreased as elevation increased. Contact between the tendon and the glenoid occurred in all participant models at a mean elevation of 123° ± 10°. Contact between the footprint and the glenoid occurred in 13 of 20 models at a mean of 139° ± 10°. Less glenoid retroversion was associated with lower tendon-to-glenoid contact angles (r = –0.76; R² = 0.58; P < .01).

Conclusion:

This study found that the supraspinatus tendon progressively approximated the glenoid during simulated overhead reaching. Additionally, all participant models eventually made contact with the glenoid by 150° of humerothoracic elevation, although anatomic factors influenced the precise angle at which contact occurred.

Clinical Relevance:

Contact between the supraspinatus and the glenoid may occur frequently within the range of elevation required for overhead activities. Therefore, internal impingement may be a prevalent mechanism for rotator cuff deformation that could contribute to cuff pathology.

Sharpened lateral acromion morphology (SLAM sign) as an indicator of rotator cuff tear: a retrospective matched study

Background

Bigliani types of acromion and critical shoulder angle (CSA) have been implicated as indicators of rotator cuff disease. A sharpened inferolateral edge of acromion (termed as Sharpened Lateral Acromion Morphology or SLAM sign) is frequently observed in anteroposterior radiographs of the glenohumeral joint in patients with rotator cuff tears (RCT). We aimed to evaluate the association of the SLAM sign with RCT in comparison to high CSA (≥35°) and Bigliani type 3 (hooked) acromion.

Methods

A cohort of 100 consecutive patients undergoing non-arthroplasty surgery for RCT and 106 patients with primary frozen shoulder were matched manually in 1:1 ratio based on age and gender to yield study population with 50 patients in each group. The 2 groups were compared for the presence of the SLAM sign, high CSA, and type 3 acromion on the radiographs.

Results

All the 3 parameters were found more prevalent in the RCT group than the frozen shoulder group (SLAM, 46% vs. 0; high CSA, 60% vs. 40%; type 3 acromion, 18% vs. 4%) (P < .05). The SLAM sign showed stronger correlation with RCT than high CSA and type 3 acromion (Ps = 0.562 vs. 0.220 vs. 0.224 respectively).

Conclusion

The SLAM sign is a simple and easily identifiable radiological predictor of rotator cuff disease.

Increasing transforming growth factor-beta concentrations with age decrease apelin in the rat rotator cuff

Background

The rotator cuff undergoes natural degeneration with age, leading to age-related rotator cuff tear; however, the precise mechanism remains unclear. Transforming growth factor-beta (TGF-β) concentrations rise with age and TGF-β contributes to the pathophysiology of skeletal muscle. TGF-β has also been shown to suppress expression of the myokine, apelin, in skin fibroblasts. We hypothesized that TGF-β expression in the rotator cuff changes with age and regulates apelin expression, thereby contributing to rotator cuff degeneration.

Methods

We used quantitative reverse-transcription polymerase chain reaction (Q-RT-PCR) to measure the expression of apelin and tendon-related genes (Tnmd, Col1a1, and Col3a1) in the rotator cuff of young (12 weeks), adult (24 weeks), and old (48 weeks) rats. Using Q-RT-PCR and enzyme-linked immunosorbent assay, we also measured Tgfb mRNA and TGF-β protein levels, respectively. Furthermore, we used Q-RT-PCR to measure apelin mRNA levels in rotator cuff-derived cells after treatment with 0 (control) and 10 ng/mL recombinant TGF-β.

Results

Apelin mRNA levels were significantly lower in old compared to young and adult rats. Similarly, tendon-related genes, Tnmd, Col1a1, and Col3a1, were significantly lower in adult and old rats than young rats. In contrast, Tgfb mRNA and TGF-β protein were significantly higher in old compared to young rats. Stimulation with exogenous TGF-β significantly decreased Apelin mRNA expression compared to control.

Conclusions

TGF-β regulates apelin expression in the rotator cuff and may play a key role in the degenerative pathology of the rotator cuff with age.

First immunohistochemical evidence of human tendon repair following stem cell injection: A case report and review of literature

BACKGROUND

Current clinical treatment options for symptomatic, partial-thickness rotator cuff tear (sPTRCT) offer only limited potential for true tissue healing and improvement of clinical results. In animal models, injections of adult stem cells isolated from adipose tissue into tendon injuries evidenced histological regeneration of tendon tissue. However, it is unclear whether such beneficial effects could also be observed in a human tendon treated with fresh, uncultured, autologous, adipose derived regenerative cells (UA-ADRCs). A specific challenge in this regard is that UA-ADRCs cannot be labeled and, thus, not unequivocally identified in the host tissue. Therefore, histological regeneration of injured human tendons after injection of UA-ADRCs must be assessed using comprehensive, immunohistochemical and microscopic analysis of biopsies taken from the treated tendon a few weeks after injection of UA-ADRCs.

CASE SUMMARY

A 66-year-old patient suffered from sPTRCT affecting the right supraspinatus and infraspinatus tendon, caused by a bicycle accident. On day 18 post injury [day 16 post magnetic resonance imaging (MRI) examination] approximately 100 g of abdominal adipose tissue was harvested by liposuction, from which approximately 75 × 10⁶ UA-ADRCs were isolated within 2 h. Then, UA-ADRCs were injected (controlled by biplanar X-ray imaging) adjacent to the injured supraspinatus tendon immediately after isolation. Despite fast clinical recovery, a follow-up MRI examination 2.5 mo post treatment indicated the need for open revision of the injured infraspinatus tendon, which had not been treated with UA-ADRCs. During this operation, a biopsy was taken from the supraspinatus tendon at the position of the injury. A comprehensive, immunohistochemical and microscopic analysis of the biopsy (comprising 13 antibodies) was indicative of newly formed tendon tissue.

CONCLUSION

Injection of UA-ADRCs can result in regeneration of injured human tendons by formation of new tendon tissue.

Acromioplasty reduces critical shoulder angle in patients with rotator cuff tear

Critical shoulder angle (CSA) is the angle between the superior and inferior bone margins of the glenoid and the most lateral border of the acromion and is potentially affected during a rotator cuff tear (RCT). Acromioplasty is generally performed to rectify the anatomy of the acromion during RCT repair surgery. However, limited information is available regarding the changes in the CSA after anterolateral acromioplasty. We hypothesized that CSA can be decreased after anterolateral acromioplasty. Data were retrospectively collected from 712 patients with RCTs and underwent arthroscopic rotator cuff repair between January 2012 and December 2018, of which 337 patients were included in the study. The presurgical and postsurgical CSA were then determined and compared using a paired samples t test. Because previous study mentioned CSA more than 38 degrees were at risk of rotator cuff re-tear, patients were segregated into two groups: CSA < 38° and CSA ≥ 38°; these groups were compared using an independent-samples t test. These 337 participants (160 male and 177 female) presented a CSA of 38.4° ± 6.0° before anterolateral acromioplasty, which significantly decreased to 35.8° ± 5.9° after surgery (P < .05). Before surgery, 172 patients were present in the CSA ≥ 38° group and 57 were preset in the CSA < 38° group after surgery. The CSA decreased significantly in the CSA ≥ 38° group rather than in the CSA < 38° group (P < .05). In conclusion, the CSA can be effectively decreased through anterolateral acromioplasty, and this reduction in the CSA is more significant among individuals with CSA ≥ 38° than among those with CSA < 38°, indicating that acromioplasty is recommended along with RCT repair especially among individuals with a wide presurgical CSA.

Can a simple fall cause a rotator cuff tear? Literature review and biomechanical considerations

PURPOSE

A simple fall on the shoulder is often referred to as minor trauma that cannot cause a tendon tear but at best reveal a pre-existing rotator cuff pathology. We wanted to know whether this statement was true. The purpose of our study was therefore to summarize the causes of acute rotator cuff tears reported in the literature and provide a biomechanical explanation for tendon tears diagnosed after a fall.

METHOD

We searched PubMed and included studies reporting rotator cuff tears occurring due to a trauma. The number of cases, the tendons involved, the age of the patients, and the nature of trauma were summarized. In addition, we noted any information provided by the authors on the pathogenesis of acute tendon ruptures.

RESULTS

Sixty-seven articles with a total of 4061 traumatic rotator cuff tears met the inclusion criteria. A simple fall was the most common cause (725 cases) and the supraspinatus tendon was most frequently affected. The postulated pathomechanism is a sudden stretch of the tendon-muscle unit while contracting (eccentric loading).

CONCLUSION

A simple fall can cause an acute rotator cuff tear and fall-related tears are not restricted to young individuals. They can affect patients of any age. The stresses occurring within the rotator cuff during an attempt to cushion a fall may locally exceed the tensile strength of the tendon fibers and cause a partial or full-thickness tear.

Non-surgical and surgical treatments for rotator cuff disease: a pragmatic randomised clinical trial with 2-year follow-up after initial rehabilitation

BACKGROUND

Rotator cuff disease (RCD) causes prolonged shoulder pain and disability in adults. RCD is a continuum ranging from tendinopathy to full-thickness tendon tear. Recent studies have shown that subacromial decompression and non-surgical treatments provide equivalent results in RCD without a full-thickness tendon lesion. However, the importance of surgery for full-thickness tendon tears remains unclear.

METHODS

In a pragmatic, randomised, controlled trial, 417 patients with subacromial pain underwent 3-month initial rehabilitation and MRI arthrography (MRA) for the diagnosis of RCD. Of these, 190 shoulders remained symptomatic and were randomised to non-surgical or surgical treatments. The primary outcomes were the mean changes in the Visual Analogue Scale for pain and the Constant Murley Score for shoulder function at the 2-year follow-up.

RESULTS

At the 2-year follow-up, both non-surgical and surgical treatments for RCD reduced pain and improved shoulder function. The scores differed between groups by 4 (95% CI -3 to 10, p=0.25) for pain and 3.4 (95% CI -0.4 to 7.1, p=0.077) for function. Among patients with full-thickness ruptures, the reduction in pain (13, 95% CI 5 to 22, p=0.002) and improvement in function (7.0, 95% CI 1.8 to 12.2, p=0.008) favoured surgery.

CONCLUSIONS

Non-surgical and surgical treatments for RCD provided equivalent improvements in pain and function. Therefore, we recommend non-surgical treatment as the primary choice for patients with RCD. However, surgery yielded superior improvement in pain and function for full-thickness rotator cuff rupture. Therefore, rotator cuff repair may be suggested after failed non-surgical treatment.

TRIAL REGISTRATION DETAILS

ClinicalTrials.gov, NCT00695981 and NCT00637013.

The biomechanics of the rotator cuff in health and disease - A narrative review

The rotator cuff has an important role in the stability and function of the glenohumeral joint. It is a complex anatomic structure commonly affected by injury such as tendinopathy and cuff tears. The rotator cuff helps to provide a stabilising effect to the shoulder joint by compressing the humeral head against the glenoid cavity via the concavity compression mechanism. To appreciate the function of the cuff it is imperative to understand the normal biomechanics of the cuff as well as the mechanisms involved in the pathogenesis of cuff disease. The shoulder joint offers a wide range of motion due to the variety of rotational moments the cuff muscles are able to provide. In order for the joint to remain stable, the cuff creates a force couple around the glenohumeral joint with coordinated activation of adjacent muscles, which work together to contain the otherwise intrinsically unstable glenohumeral joint and prevent proximal migration of the humerus. Once this muscular balance is lost, increased translations or subluxation of the humeral head may result, leading to changes in the magnitude and direction of the joint reaction forces at the glenohumeral joint. These mechanical changes may then result in a number of clinical presentations of shoulder dysfunction, disease and pain. This narrative review aims to highlight the importance of functional rotator cuff biomechanics whilst assessing the kinetics and kinematics of the shoulder joint, as well as exploring the various factors involved in cuff disease.

Low serum vitamin B12 levels are associated with degenerative rotator cuff tear

BACKGROUND

Vitamin B₁₂ (Vit B₁₂) deficiency results in elevated homocysteine levels and interference with collagen cross-linking, which may affect tendon integrity. The purpose of this study was to investigate whether serum Vit B₁₂ levels were correlated with degenerative rotator cuff (RC) tear.

METHODS

Eighty-seven consecutive patients with or without degenerative RC tear were enrolled as study participants. Possible risk factors (age, sex, medical history, bone mineral density, and serum chemistries including glucose, magnesium, calcium, phosphorus, zinc, homocysteine, Vitamin D, Vit B₁₂, homocysteine, and folate) were assessed. Significant variables were selected based on the results of univariate analyses, and a logistic regression model (backward elimination) was constructed to predict the presence of degenerative RC tear.

RESULTS

In the univariate analysis, the group of patients with degenerative RC tear had a mean concentration of 528.4 pg/mL Vit B₁₂, which was significantly lower than the healthy control group (627.1 pg/mL). Logistic regression analysis using Vit B₁₂ as an independent variable revealed that Vit B₁₂ concentrations were significantly correlated with degenerative RC tear (p = 0.044). However, Vit B₁₂ levels were not associated with tear size.

CONCLUSION

Low serum levels of Vit B₁₂ were independently related to degenerative RC tear. Further investigations are warranted to determine if Vit B₁₂ supplementation can decrease the risk of this condition.

Factors Associated With Symptomatic Rotator Cuff Tears: The Rotator Cuff Outcomes Workgroup Cohort Study

OBJECTIVE

Although rotator cuff tear is one of the most common musculoskeletal disorders, its etiology is poorly understood. We assessed factors associated with the presence of rotator cuff tears in a cohort of patients with shoulder pain.

DESIGN

From February 2011 to July 2016, a longitudinal cohort of patients with shoulder pain was recruited. Patients completed a detailed questionnaire in addition to a magnetic resonance imaging scan and a clinical shoulder evaluation. The association of multiple factors associated with rotator cuff tears was assessed using multivariate logistic regression.

RESULTS

In our cohort of 266 patients, 61.3% of patients had a rotator cuff tear. Older age (per 1 yr: odds ratio = 1.03, 95% confidence interval = 1.02-1.07), involvement of the dominant shoulder (odds ratio = 2.02, 95% confidence interval = 1.16-3.52), and a higher body mass index (per 1 kg/m2: odds ratio = 1.06, 95% confidence interval = 1.03-1.12) were independently associated with rotator cuff tears. Sex, depression, smoking status, shoulder use at work, hypertension, and diabetes were not significantly associated with rotator cuff tear.

CONCLUSIONS

In a cohort of patients with shoulder pain, we identified older age, involvement of the dominant shoulder, and a higher body mass index to be independently associated with rotator cuff tear. The mechanism of how these factors possibly lead to rotator cuff tears needs further research.

TO CLAIM CME CREDITS

Complete the self-assessment activity and evaluation online at http://www.physiatry.org/JournalCME.

CME OBJECTIVES

Upon completion of this article, the reader should be able to: (1) Identify factors associated with an increased risk of developing rotator cuff tears in adults; (2) Describe the current epidemiological trends of rotator cuff tears in the United States; and (3) Discuss the pathophysiological role of aging in the development of nontraumatic rotator cuff tears.

LEVEL

Advanced.

ACCREDITATION

The Association of Academic Physiatrists is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.The Association of Academic Physiatrists designates this Journal-based CME activity for a maximum of 1.0 AMA PRA Category 1 Credit(s)™. Physicians should only claim credit commensurate with the extent of their participation in the activity.

Engineering multi-tissue units for regenerative Medicine: Bone-tendon-muscle units of the rotator cuff

Our body systems are comprised of numerous multi-tissue units. For the musculoskeletal system, one of the predominant functional units is comprised of bone, tendon/ligament, and muscle tissues working in tandem to facilitate locomotion. To successfully treat musculoskeletal injuries and diseases, critical consideration and thoughtful integration of clinical, biological, and engineering aspects are necessary to achieve translational bench-to-bedside research. In particular, identifying ideal biomaterial design specifications, understanding prior and recent tissue engineering advances, and judicious application of biomaterial and fabrication technologies will be crucial for addressing current clinical challenges in engineering multi-tissue units. Using rotator cuff tears as an example, insights relevant for engineering a bone-tendon-muscle multi-tissue unit are presented. This review highlights the tissue engineering strategies for musculoskeletal repair and regeneration with implications for other bone-tendon-muscle units, their derivatives, and analogous non-musculoskeletal tissue structures.

The association between Interleukin-6 rs1800795/rs1800797 polymorphisms and risk of rotator cuff tear in a Chinese population

Expression of proinflammatory cytokines, such as interleukin (IL)-6 (IL-6) and metalloproteases, are elevated in patients with rotator cuff tear (RCT). In order to investigate the role of IL-6 gene polymorphisms on RCT risk, we genotyped two SNPs on IL-6 gene (rs1800795 and rs1800797) in 138 RCT patients and 137 healthy controls using polymerase chain reaction (PCR) and Sanger sequencing. The IL-6 expression in shoulder joint synovial fluid was determined by using enzyme-linked immunosorbent assay (ELISA) method. The constant score and visual analog scale (VAS) were used to evaluate the clinical outcome of two s (surgicsal vs. conservative) for RCT patients. For rs1800795, individuals with the GG genotype or G allele had significantly higher risk of RCT. Elevated risk of tear size was associated with the GG genotype of the rs1800795 polymorphism. The IL-6 rs1800797 polymorphism was also associated with an increased risk of RCT, especially among female, drinkers, and individuals with B(MI) < 25 kg/m². The elevated levels of IL-6 gene were observed among the mutant genotype of rs1800795/rs1800797 polymorphism. Surgical group is significantly better than conservative treatment from the perspective of constant score and VAS. Furthermore, CG genotype of rs1800795 polymorphism increased the constant score at 6 months in comparison with CC genotype. In conclusion, our study supports a role of IL-6 rs1800795/rs1800797 polymorphisms on increased RCT risk. The RCT patients with CG genotype of rs1800795 polymorphism have more obvious surgical treatment effects by influencing the IL-6 expression.

Novel self-amplificatory loop between T cells and tenocytes as a driver of chronicity in tendon disease

OBJECTIVES

Increasing evidence suggests that inflammatory mechanisms play a key role in chronic tendon disease. After observing T cell signatures in human tendinopathy, we explored the interaction between T cells and tendon stromal cells or tenocytes to define their functional contribution to tissue remodelling and inflammation amplification and hence disease perpetuation.

METHODS

T cells were quantified and characterised in healthy and tendinopathic tissues by flow cytometry (FACS), imaging mass cytometry (IMC) and single cell RNA-seq. Tenocyte activation induced by conditioned media from primary damaged tendon or interleukin-1β was evaluated by qPCR. The role of tenocytes in regulating T cell migration was interrogated in a standard transwell membrane system. T cell activation (cell surface markers by FACS and cytokine release by ELISA) and changes in gene expression in tenocytes (qPCR) were assessed in cocultures of T cells and explanted tenocytes.

RESULTS

Significant quantitative differences were observed in healthy compared with tendinopathic tissues. IMC showed T cells in close proximity to tenocytes, suggesting tenocyte-T cell interactions. On activation, tenocytes upregulated inflammatory cytokines, chemokines and adhesion molecules implicated in T cell recruitment and activation. Conditioned media from activated tenocytes induced T cell migration and coculture of tenocytes with T cells resulted in reciprocal activation of T cells. In turn, these activated T cells upregulated production of inflammatory mediators in tenocytes, while increasing the pathogenic collagen 3/collagen 1 ratio.

CONCLUSIONS

Interaction between T cells and tenocytes induces the expression of inflammatory cytokines/chemokines in tenocytes, alters collagen composition favouring collagen 3 and self-amplifies T cell activation via an auto-regulatory feedback loop. Selectively targeting this adaptive/stromal interface may provide novel translational strategies in the management of human tendon disorders.

Bringing tendon biology to heel: Leveraging mechanisms of tendon development, healing, and regeneration to advance therapeutic strategies

Tendons are specialized matrix-rich connective tissues that transmit forces from muscle to bone and are essential for movement. As tissues that frequently transfer large mechanical loads, tendons are commonly injured in patients of all ages. Following injury, mammalian tendons heal poorly through a slow process that forms disorganized fibrotic scar tissue with inferior biomechanical function. Current treatments are limited and patients can be left with a weaker tendon that is likely to rerupture and an increased chance of developing degenerative conditions. More effective, alternative treatments are needed. However, our current understanding of tendon biology remains limited. Here, we emphasize why expanding our knowledge of tendon development, healing, and regeneration is imperative for advancing tendon regenerative medicine. We provide a comprehensive review of the current mechanisms governing tendon development and healing and further highlight recent work in regenerative tendon models including the neonatal mouse and zebrafish. Importantly, we discuss how present and future discoveries can be applied to both augment current treatments and design novel strategies to treat tendon injuries.

Genetic variants associated with rotator cuff tearing utilizing multiple population-based genetic resources

BACKGROUND

The etiology of rotator cuff tearing is likely multifactorial, including a potential genetic predisposition. The purpose of the study was to identify genetic variants associated with rotator cuff tearing utilizing the UK Biobank (UKB) cohort, confirm variants using a separate genetic database, and evaluate tissue expression of genes with associated variants following rotator cuff tearing using RNA sequencing.

METHODS

Genome-wide association study (GWAS): A GWAS was performed using data from UKB with 5701 cases of rotator cuff injury. RNA sequencing analyses: rotator cuff 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 humerus fracture (controls). Total RNA was extracted and differential gene expression was measured by RNAseq for genes with variants associated with rotator cuff tearing.

RESULTS

The results of the UKB GWAS identified 3 loci that reached genome-wide statistical significance: 2 loci on chromosome 7 in GLCCI1 (rs4725069; P = 5.0E-09) and THSD7A (rs575224171; P = 5.3E-09), and 1 locus on chromosome 2 in ZNF804A (rs775583810; P = 3.9E-09). The association with rotator cuff injury of the GLCCI1 single-nucleotide polymorphism (SNP; rs4725069) was confirmed in the Kaiser Permanente Research Bank cohort (P = .008). Twenty previously reported SNPs in 12 genes were evaluated using summary statistics from the UKB GWAS, which confirmed 3 SNPs in TNC with rotator cuff injury (rs1138545, rs72758637, and rs7021589; all P < .0024). Of 17 genes with variants associated with rotator cuff injury (14 previously from literature plus 3 new genes from current UKB GWAS), TIMP2, Col5A1, TGFBR1, and TNC were upregulated (P < .001 for all) and THSD7A was downregulated (P = .005) in tears vs. controls in the RNA sequencing data set.

CONCLUSION

The UKB GWAS has identified 3 novel loci associated with rotator cuff tearing (ZNF804A, GLCCI1, THSD7A). Expression of the THSD7A gene was significantly downregulated in rotator cuff tears vs. controls supporting a potential functional role. Three previously reported SNPs in the TNC gene were validated in the UKB GWAS, supporting a role for this gene in rotator cuff tearing. Finally, TIMP2, Col5A1, TGFBR1, and TNC genes were found to have significantly upregulated tissue expression in cases vs. controls supporting a biologic role in tearing for these genes.

Clinical Y-view versus 3-dimensional assessments of intramuscular fat in patients with full-thickness rotator cuff tears

RATIONALE AND OBJECTIVES

Recent evidence suggests an inhomogeneous distribution of intramuscular rotator cuff fat infiltration (FI) in a small sample of individuals with rotator cuff tears, yet clinically just a few slices at the scapular Y-view are used to evaluate FI in patients with rotator cuff tears. The purpose of this study was to determine if assessment of FI using the scapular Y-view is representative of the entire muscle in patients with full-thickness rotator cuff tears, and whether this varies by tear size.

MATERIALS AND METHODS

Patients (N = 25) diagnosed with full-thickness rotator cuff tear and confirmed with magnetic resonance imaging (MRI) were included. Fat-water sequences were used to objectively quantify mean FI (%) in the entire 3D muscle and the mean from 3 slices at the Y-view. Mixed-model 2 × 2 ANOVAs were used to assess for differences between methods, and if results vary by tear-size.

RESULTS

There were no statistically significant differences between mean amount of FI of the entire 3D muscle and mean Y-view in the supraspinatus or infraspinatus muscles (p > 0.05). Additionally, this did not differ across tear size groups (p > 0.05).

CONCLUSION

Results of this study suggest FI assessed in the Y-view is not different (mean difference < 1.0%) from FI of the entire 3D muscle in patients with full-thickness rotator cuff tears. Therefore, the clinical utility of evaluating rotator cuff intramuscular fat infiltration with the Y-view is further supported in patients with full-thickness rotator cuff tears across tear sizes.

Definition of the terms "acute" and "traumatic" in rotator cuff injuries: a systematic review and call for standardization in nomenclature

BACKGROUND

Although of high relevance for clinical decision making, there exists no consensus throughout the literature of the terms "acute" and "traumatic" used in the classification of rotator cuff tears. With differing definitions, the comparability of outcome studies may be limited. The aim was to provide a detailed systematic review of the definitions used in the literature and present a suggestion for a standardization in nomenclature based on the findings.

METHODS

Four different internet databases were searched in February 2020 using the terms ("acute" OR "traumatic" OR "trauma" OR "athlete" OR "young") AND ("rotator cuff tears" OR "rotator cuff tear" OR "rotator cuff" OR "rotator cuff rupture" OR "supraspinatus" OR "infraspinatus" OR "subscapularis" OR "teres minor"). Prospective, retrospective, cohort and case-control studies as well as case series were included. Systematic reviews, cadaveric or laboratory studies and studies on non-traumatic or non-acute rotator cuff tears were excluded.

RESULTS

The literature search conducted 10,349 articles of which 10,151 were excluded based on the title, 119 based on the abstract and 33 based on the manuscript. A total of 46 studies were finally included for review and subsequently analyzed. Overall, there exists no consensus neither on the term "acute" nor on "traumatic" in the context of rotator cuff tears in the literature. The time span for acute injuries ranged between 2 weeks and 6 months. For traumatic injuries, only 20% of the selected studies described a specific and adequate injury mechanism in combination with adequate imaging.

CONCLUSION

The term "acute" should be reserved for RCT showing muscle edema, wavelike appearance of the central part of the torn tendon and joint effusion, which typically requires adequate imaging within 2 weeks from trauma. Repair of acute tears should occur within 8 weeks from trauma to benefit from possibly superior biological healing capacities. The term "traumatic" should be used for a sudden onset of symptoms in a previously asymptomatic patient, triggered by an adequate trauma, e.g., a fall on the retroverted arm with an axial cranioventral force or a traumatic shoulder dislocation.

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.

Inhibition of Smad3 promotes the healing of rotator cuff injury in a rat model

To investigate the effect of inhibiting transforming growth factor-β (TGF-β1)/Smad2/3 signaling on rotator cuff (RC) healing. A bilateral supraspinatus tendon detachment-repair model of Sprague-Dawley (SD) rats was utilized. A total of 120 SD rats were randomly assigned to six groups and each group received the subacromial injection of normal saline, empty vectors, or lentiviral vectors containing small interfering RNA against TGF-β1, Smad2, Smad3 at the bone-tendon junction. Biomechanical and histological analyses were performed to evaluate bone-tendon junction healing quality at 8 weeks after repair. Histologically, scar healing was found in all surgical groups. Animals with inhibited Smad3 exhibited better bone-tendon junction structures with higher density, parallel orientation, and collagen fiber continuity than other surgical group animals. Immunohistochemistry revealed that the protein expression level of collagen I in animals with inhibited Smad3 was more prominent compared with all other surgical groups. Biomechanically, Animals with inhibited Smad3 showed better results in the maximum load at 4, 6, and 8 weeks after surgery compared with other surgical groups. Besides, C3H10T1/2 (Smad3-) cells increased TT-D6 cell migration and tendon-associated genes expression (scleraxis, tenascin C, collagen I) in coculture system. We conclude that inhibition of Smad3 promotes RC tendon healing in the rat supraspinatus model.

Lateral acromioplasty cannot sufficiently reduce the critical shoulder angle if preoperatively measured over 40°

PURPOSE

To investigate whether arthroscopic lateral acromion resection can sufficiently reduce the critical shoulder angle (CSA) without damaging deltoid muscle insertion.

METHODS

Ninety patients who underwent arthroscopic rotator cuff (RC) repair were retrospectively analysed. According to the preoperative CSA, patients were categorized as Group I (CSA < 35°) and Group II (CSA ≥ 35°). Additional arthroscopic lateral acromion resection was performed in Group II. The CSA was measured 1 week postoperatively, while RC integrity and the deltoid attachment were assessed at 3, 6 and 12 months via ultrasound. Deltoid function was evaluated using the Akimbo test, in which patients place their hands on the iliac crest with abduction in the coronal plane and internal rotation of the shoulder joint while simultaneously flexing the elbow joint and pronating the forearm.

RESULTS

Large and massive RC tears were more prevalent in Group II (p = 0.017). In both groups, the CSA reduction was statistically significant (Group I = 1°: range 0°-3°, Group II = 3.7°: range 1°-8°; p < 0.001). When the preoperative CSA was > 40°, the respective postoperative CSA remained > 35° in 83.3% of cases (p < 0.001). Final shoulder strength was correlated with the amount of CSA reduction (rho = 0.41, p = 0.002). The postoperative CSA was higher, but not significantly different (n.s.), in patients with re-torn (36°, range 32°-40°) than with healed RC (33°, range 26°-38°). No clinical detachment or hypotrophy of the deltoid was observed with the Akimbo test and ultrasound evaluation.

CONCLUSIONS

Arthroscopic lateral acromion resection is a safe procedure without affecting deltoid muscle origin or function, and it is effective in significantly reducing the CSA. However, the CSA cannot always be reduced to < 35°, especially in patients with preoperative CSA values > 40°.

LEVEL OF EVIDENCE

III.