Editorial Commentary: Illuminating the Fragility of Nonsignificant Trials in Sports Medicine.

Orthopaedic clinical research findings can be prone to ß error (false negative), owing to small sample sizes. Such trials show no difference between groups when, in fact, a difference may exist. The reverse fragility index is defined as the number of "events" that would cause an individual research study's findings to flip from nonsignificant to statistically significant, and this index can help determine the clinical relevance and validity of clinical trials reporting nonsignificant results. Orthopaedic surgeons should critically evaluate clinical research that shows no statistically significant difference between groups to rule out a ß error, given that underpowered studies are particularly prone to fragility. If an orthopaedic trial reports statistically insignificant results, this does not mean the results are clinically insignificant.

Counteractive Effects of IL-33 and IL-37 on Inflammation in Osteoarthritis.

Osteoarthritis (OA) is a chronic inflammatory disease where pro-inflammatory cytokines, damage-associated molecular patterns (DAMPs), and macrophages play a crucial role. However, the interactive role of these mediators, the exact cause precipitating OA and definitive treatment for OA are not known yet. Moreover, the interactive role of interleukin (IL)-33 and IL-37 with other factors in the pathogenesis of OA has not been discussed elaborately. In this study, we analyzed the expression of IL-33 and IL-37 in human OA knee and hip joint cartilage tissues. The effect of increased DAMPs, IL-33, and IL-37 on IL-6, tumor necrosis factor (TNF)-α, toll-like receptors (TLRs), and matrix metalloproteinases (MMPs) expression was delineated using human normal and osteoarthritic chondrocytes. The effect of anti-inflammatory cytokine IL-37 on various mediators of inflammation in the presence of IL-33, rHMGB-1, and LPS was investigated to delineate the effects of IL-37. Further, the effects of blocking IL-33 downstream signaling and the effects of IL-33 and IL-37 on macrophage polarization were assessed along with examining the macrophage phenotypes in human OA cartilage tissues. The results of this study revealed increased expression of IL-33 in OA cartilage and that IL-33 increases IL-6, TNF-α, TLRs, and MMPs expression and favors phenotypic conversion towards the M1 phenotype, while IL-37 and blocking IL-33 receptor ST2 have opposite effects. Overall, the results suggest that blocking IL-33 and increasing IL-37 act synergistically to attenuate inflammation and might serve as potential therapeutics in OA.

Hybrid interpenetrating hydrogel network favoring the bidirectional migration of tenocytes for rotator cuff tendon regeneration.

Replenishment of tenocytes to the injury site is an ideal strategy to improve healing response and accelerate the tendon ECM regeneration. The present study focused on the synthesis and characterization of a hybrid hydrogel scaffold system poly(propylene-fumarate)-alginate-polyvinyl alcohol-acrylic acid (PAPA) using poly(propylene-fumarate) (PPF), alginate, polyvinyl alcohol (PVA) and acrylic acid and the in vitro investigation of bidirectional mobility of swine shoulder tenocytes (SST) for its potential application in rotator-cuff tendon regeneration. IR analysis revealed the presence of alginate, PPF and PVA segments on the surface, SEM and AFM analyses revealed the porous and nano-topographical features of PAPA, respectively, swelling was 712.6 ± 84.21% with the EWC (%) of 87.59 ± 1.26 having the diffusional exponent and swelling constant 0.551 and 1.8, respectively. PAPA was biodegradable, cytocompatible and supported long-term survival of SSTs. SEM imaging revealed the adhesion, colonization, and sheet formation of SSTs within the PAPA hydrogel network. The SSTs seeded on the PAPA scaffolds were peculiar for their bidirectional migration as the anterograde movement was completed in 9 days whereas the retrograde infiltration occurred up to the depth of 198 µm. These findings suggest the promising translational potential of PAPA scaffold system in the management of rotator cuff tendon injury.

Editorial Commentary: Off the Hip or Off the Shelf? An Analysis of Autograft and Allograft as a Graft Source for Shoulder Superior Capsular Reconstruction.

Superior capsular reconstruction can effectively relieve pain and improve function in the rotator cuff-deficient shoulder, but the optimal graft has not been determined. Multiple authors have demonstrated the effectiveness of the procedure, but bias and heterogeneity between studies do not allow valid comparative analysis of graft type. Until we can adequately compare outcomes, complications, or survival, graft availability and cost may be the greatest determinants of graft selection.

Matrix regeneration proteins in the hypoxia-triggered exosomes of shoulder tenocytes and adipose-derived mesenchymal stem cells.

Regenerative functions of exosomes rely on their contents which are influenced by pathological stimuli, including hypoxia, in rotator cuff tendon injuries (RCTI). The hypoxic environment triggers tenocytes and adjacent adipose-derived mesenchymal stem cells (ADMSCs) to release regenerative mediators to the ECM via the exosomes which elicit autocrine/paracrine responses to protect the tendon matrix from injury. We investigated the exosomal protein contents from tenocytes and subcutaneous ADMSCs from the shoulder of Yucatan microswine cultured under hypoxic conditions (2% O2). The exosomal proteins were detected using high-resolution mass spectrometry nano-LC-MS/MS Tribrid system and were compiled using 'Scaffold' software. Hypoxic exosomes from tenocytes and ADMSCs carried 199 and 65 proteins, respectively. The key proteins identified by mass spectrometry and associated with ECM homeostasis from hypoxic ADMSCs included MMP2, COL6A, CTSD and TN-C and those from hypoxic tenocytes were THSB1, NSEP1, ITIH4 and TN-C. These findings were confirmed at the mRNA and protein level in the hypoxic ADMSCs and tenocytes. These proteins are involved in multiple signaling pathways of ECM repair/regeneration. This warrants further investigations for their translational significance in the management of RCTI.

Do we really need to order magnetic resonance imaging? Shoulder surgeon ultrasound practice patterns and beliefs.

BACKGROUND: Despite significant benefits, many orthopedic surgeons are hesitant to incorporate diagnostic ultrasound into their practice. This may be because of a lack of comfort, knowledge, and/or training. The purpose of this study was to analyze practice patterns regarding the use of shoulder ultrasound by orthopedic surgeons to diagnose rotator cuff tears. MATERIALS AND METHODS: We conducted a survey of the members of the American Shoulder and Elbow Surgeons (ASES) regarding their use of ultrasound. A systematic review of the literature on the use of ultrasound in the shoulder by orthopedic surgeons was also performed. RESULTS: Of the members of ASES responding to the survey, 55% are using ultrasound for diagnostic purposes in the shoulder. The leading reason for not using ultrasound as the sole imaging modality prior to performing rotator cuff repair was lack of confidence in the ability to determine the reparability of the tear (83%). Our systematic review showed that for an orthopedic surgeon diagnosing a full-thickness rotator cuff tear, the mean sensitivity was 92% and mean specificity was 89%. CONCLUSIONS: Many ASES surgeons are not using ultrasound in the shoulder despite its many potential benefits over magnetic resonance imaging. This is because of a lack of confidence in the ability to quantify fatty infiltration, muscle atrophy, and the level of retraction medial to the acromion. Our systematic review showed that orthopedic surgeons can be accurate in the diagnosis of full-thickness rotator cuff tears. Future research should focus on defining parameters of shoulder ultrasound associated with rotator cuff tendon reparability. Educating surgeons on ultrasound technique, cost, and evidence may be a promising strategy to enhance the value in musculoskeletal care delivery.

Therapeutic potential of exosomes in rotator cuff tendon healing.

Rotator cuff tears are common musculoskeletal injuries that can cause significant pain and disability. While the clinical results of rotator cuff repair can be good, failure of tendon healing remains a significant problem. Molecular mechanisms underlying structural failure following surgical repair remain unclear. Histologically, enhanced inflammation, disorganization of the collagen fibers, calcification, apoptosis and tissue necrosis affect the normal healing process. Mesenchymal stem cells (MSCs) have the ability to provide improved healing following rotator cuff repair via the release of mediators from secreted 30-100 nm extracellular vesicles called exosomes. They carry regulatory proteins, mRNA and miRNA and have the ability to increase collagen synthesis and angiogenesis through increased expression of mRNA and release of proangiogenic factors and regulatory proteins that play a major role in proper tissue remodeling and preventing extracellular matrix degradation. Various studies have shown the effect of exosomes on improving outcome of cutaneous wound healing, scar tissue formation, degenerative bone disease and Duchenne Muscular Dystrophy. In this article, we critically reviewed the potential role of exosomes in tendon regeneration and propose the novel use of exosomes alone or seeded onto biomaterial matrices to stimulate secretion of favorable cellular factors in accelerating the healing response following rotator cuff repair.

Collagen type III content of the long head of the biceps tendon as an indicator of glenohumeral arthritis.

Tendonosis is characterized by an increase in collagen type III relative to collagen type I, but the precise ratio of collagen type I to collagen type III in pathologic shoulder tendons has not been reported. A tendon continuously bathed in an OA synovial environment may exhibit histomorphologic differences as compared to those from shoulders with a preserved articular surface. The purpose of this study was to evaluate the biochemical and histological differences in the proximal portion of the long head of the biceps tendon (LHBT) from a non-arthritic versus an arthritic glenohumeral joint. Sixteen patients undergoing shoulder surgery were prospectively enrolled in the study. Group-1 consisted of patients with glenohumeral OA and Group-2 consisted of patients without OA. The LHBT was tenodesed and excised tendon was fixed, embedded, sectioned (5 µm), deparaffinized, and used for histology (H&E and Masson trichrome staining) and immunofluorescence analysis to determine levels of collagen III, MMP-1, MMP-9, TIMP-1, and TIMP-2. Compared to the patients without arthritis, group-1 exhibited significant inflammation with extracellular matrix disorganization and significantly higher (P < 0.05) collagen III, MMP-2, and MMP-9 levels. No considerable difference in collagen I was observed between the two groups. TIMP-1 and TIMP-2 were completely absent in both the groups. The level of collagen subtypes varied markedly between LHBT tendons from patients with and without OA. Increased collagen III in the LHBT is associated with glenohumeral arthritis. Measuring collagen type in the LHBT may serve as a useful metric in the diagnosis and treatment of musculoskeletal pathology.

Epigenetic mechanisms and implications in tendon inflammation (Review).

Cellular inflammation is not just an immediate response following pathogenic infections or resulting from damage due to injury, it is also associated with normal physiological functions, including wound healing and tissue repair. The existence of such a definitive role in normal physiology and in disease pathology indicates the presence of a regulatory mechanism that is tightly controlled in normal cells. A tight control over gene expression is associated with regulatory mechanisms in the cells, which can be either inducible or epigenetic. Among other intracellular mechanisms that contribute to epigenetic gene regulation, DNA methylation has been shown to maintain a tight control over gene expression through the actions of DNA methyltransferases (DNMTs). With a clear role in developmental and tissue­specific temporal gene regulation, the involvement of DNMTs is evident in normal and pathological conditions. In this review article, inflammation in tendons associated with disease pathology and tissue repair or regeneration at the musculoskeletal joints is critically reviewed. More specifically, the review focuses on known epigenetic mechanisms and their role in the clinical presentation of the disease in human joint disorders associated with tendon inflammation, with an emphasis on the gene regulatory mechanisms that are controlled through DNA methylation, histone deacetylation, and microRNAs.

Genes interconnecting AMPK and TREM-1 and associated microRNAs in rotator cuff tendon injury.

Fatty infiltration and inflammation delay the healing responses and raise major concerns in the therapeutic management of rotator cuff tendon injuries (RCTI). Our evaluations showed the upregulation of 'metabolic check point' AMPK and inflammatory molecule, TREM-1 from shoulder biceps tendons collected from RCTI subjects. However, the epigenetic regulation of these biomolecules by miRNAs is largely unknown and it is likely that a deeper understanding of the mechanism of action can have therapeutic potential for RCTI. Based on this background, we have evaluated the miRNAs from RCTI patients with fatty infiltration and inflammation (FI group) and compared with RCTI patients without fatty infiltration and inflammation (No-FI group). NetworkAnalyst was employed to evaluate the genes interconnecting AMPK and TREM-1 pathway, using PRKAA1 (AMPK), TREM-1, HIF1α, HMGB1, and AGER as input genes. The most relevant miRNAs were screened by considering the fold change below - 7.5 and the number of target genes 10 and more which showed 13 miRNAs and 216 target genes. The exact role of these miRNAs in the fatty infiltration and inflammation associated with RCTI is still unknown and the understanding of biological activity of these miRNAs can pave ways to develop miRNA-based therapeutics in the management of RCTI.

Amplification of Mitochondrial Activity in the Healing Response Following Rotator Cuff Tendon Injury.

Mitochondrial function following rotator cuff tendon injury (RCI) influences the tendon healing. We examined the mitochondrial morphology and function under hypoxia in the shoulder tendon tissue from surgically-induced tenotomy-RCI rat model and cultured swine tenocytes. The tendon tissue was collected post-injury on 3-5 (Group-A), 10-12 (Group-B), and 22-24 (Group-C), days and the corresponding contralateral tendons were used as control for each group. There was higher protein expression of citrate synthase (P < 0.0001) [10.22 MFI (mean fluorescent intensity)] and complex-1 (P = 0.0008) (7.86 MFI) in Group-A and Group-B that decreased in Group-C [(P = 0.0201) (5.78 MFI and (P = 0.7915) (2.32 MFI), respectively] compared to control tendons. The ratio of BAX:Bcl2 (Bcl2 associated x protein:B cell lymphoma 2) in RCI tendons increased by 50.5% (Group-A) and 68.4% (Group-B) and decreased by 25.8% (Group-C) compared to normoxic controls. Hypoxia increased ß-tubulin expression (P = 0067) and reduced PGC1-α (P = 0412) expression in the isolated swine tenocytes with no effect on the protein expression of Complex-1 (P = 7409) and citrate synthase (P = 0.3290). Also, the hypoxic tenocytes exhibited about 4-fold increase in mitochondrial superoxide (P < 0.0001), altered morphology and mitochondrial pore integrity, and increase in mitochondrial density compared to normoxic controls. These findings suggest the critical role of mitochondria in the RCI healing response.

Editorial Commentary: Get Ready to Download the i-Cuff App: Developing the Rotator Cuff Irreparability Equation.

Despite extensive published literature on rotator cuff repair, it can still be difficult to predict surgical reparability. We understand that larger chronic tears with fatty infiltration are associated with a greater risk of irreparability. However, it can be difficult to accurately determine the odds of irreparability on a patient-specific level. Several ubiquitous preoperative variables can be incorporated into an "irreparability equation" to more accurately predict if the rotator cuff can be repaired, which could be of tremendous benefit to both the patient and surgeon.

Association of Inflammatory Responses and ECM Disorganization with HMGB1 Upregulation and NLRP3 Inflammasome Activation in the Injured Rotator Cuff Tendon.

Inflammation and extracellular matrix (ECM) disorganization following the rotator cuff tendon injuries (RCTI) delay the repair and healing process and the molecular mechanisms underlying RCTI pathology are largely unknown. Here, we examined the role of HMGB1 and NLRP3 inflammasome pathway in the inflammation and ECM disorganization in RCTI. This hypothesis was tested in a tenotomy-RCTI rat model by transecting the RC tendon from the humerus. H&E and pentachrome staining revealed significant changes in the morphology, architecture and ECM organization in RC tendon tissues following RCTI when compared with contralateral control. Severity of the injury was high in the first two weeks with improvement in 3-4 weeks following RCTI, and this correlated with the healing response. The expression of proteins associated with increased HMGB-1 and upregulation of NLRP3 inflammasome pathway, TLR4, TLR2, TREM-1, RAGE, ASC, Caspase-1, and IL-1ß, in the first two weeks following RCTI followed by decline in 3-4 weeks. These results suggest the association of inflammatory responses and ECM disorganization with HMGB1 upregulation and NLRP3 inflammasome activation in the RC tendons and could provide novel target(s) for development of better therapeutic strategies in the management of RCTI.

Editorial Commentary: Our Mentors Were Right, New Is Not Always Better: The Posterolateral Shoulder Trans-Rotator Cuff Portal Is Safe for SLAP Repairs.

Shoulder SLAP repair anchors have traditionally been placed through a posterolateral trans-rotator cuff "Port of Wilmington" portal. Alternative anterolateral portals have been proposed to place superior glenoid anchors that seemingly avoid traversing the rotator cuff via the rotator interval but put the suprascapular nerve at risk. A recent cadaveric study demonstrated that the traditional posterolateral portal safely traversed the infraspinatus muscle belly in all specimens, which was in contrast to the anterolateral portal that traversed the supraspinatus tendon in all specimens. In addition, 80% of anchors placed through the anterolateral portal perforated the posterior glenoid in proximity to the suprascapular nerve. As originally suggested nearly 20 years ago, the posterolateral Port of Wilmington trajectory is safe on both the rotator cuff and glenoid side for SLAP repairs.

Collagen I: a kingpin for rotator cuff tendon pathology.

Derangements in tendon matrisome are pathognomonic for musculoskeletal disorders including rotator cuff tendinopathies (RCT). Collagen type-1 accounts for more than 85% of the dry weight of tendon extracellular matrix (ECM). The understanding of basic tendon physiology, organization of ECM, structure and function of component biomolecules of matrisome and the underlying regulatory mechanisms reveal the pathological events associated with RCT. Histomorphological evidence from RCT patients and animal models illustrate that ECM disorganization is the major hallmark in tendinopathy where a significant decrease in type-1 collagen is prevalent. However, the molecular events and regulatory signals associated with the regulation of collagen organization and its composition switch in response to pathological stimuli are largely unknown. The elucidation of various regulatory signalling pathways associated with collagen type-1 gene expression could benefit to develop novel promising therapeutic approaches to restore the tendon ECM. The major focus of the article is to critically evaluate tendon architecture regarding type-1 collagen, the molecular events associated with gene expression, secretion and maturation, the possible mechanisms of type-1 collagen regulation and its translational significance in RCT management.

MicroRNAs associated with inflammation in shoulder tendinopathy and glenohumeral arthritis.

Inflammation is associated with glenohumeral arthritis and rotator cuff tendon tears. Epigenetically, miRNAs tightly regulate various genes involved in the inflammatory response. Alterations in the expression profile of miRNAs and the elucidation of their target genes with respect to the pathophysiology could improve the understanding of their regulatory role and therapeutic potential. Here, we screened key miRNAs that mediate inflammation and linked with JAK2/STAT3 pathway with respect to the coincidence of glenohumeral arthritis in patients suffering from rotator cuff injury (RCI). Human resected long head of the biceps tendons were examined for miRNA profile from two groups of patients: Group 1 included the patients with glenohumeral arthritis and massive rotator cuff tears and the Group 2 patients did not have arthritis or rotator cuff tears. The miRNA profiling revealed that 235 miRNAs were highly altered (fold change less than -3 and greater than +2 were considered). Data from the NetworkAnalyst program revealed the involvement and interaction between 3,430 different genes associated with inflammation out of which 284 genes were associated with JAK2/STAT3 pathway and interconnect 120 different pathways of inflammation. Around 1,500 miRNAs were found to play regulatory role associated with these genes of inflammatory responses and 77 miRNAs were found to regulate more than 10 genes. Among them, 25 genes with less than tenfold change were taken to consideration which altogether constitute for the regulation of 102 genes. Targeting these miRNAs and the underlying regulatory mechanisms may advance our knowledge to develop promising therapies in the management of shoulder tendon pathology.

Alterations in tendon microenvironment in response to mechanical load: potential molecular targets for treatment strategies.

Rotator cuff (RC) tendons could beinflicted in many ways with an eventual outcome of pain, weakness and disability, which represent a large burden on health care cost. However, optimal healing, either conservatively or with surgical intervention, remains an issue that needs further investigation. Disorders of the RC tendons may result from external factors like trauma, or internal factors through physiologic and metabolic derangement. Most RC tendon disorders may be asymptomatic and may result from an over-activity of the inflicted shoulder and its tendons. Such tendon disorders are poorly diagnosed since patients do not seek medical attention until pain or weakness ensue. Immunological and biochemical events in RC disorders due to mechanical intolerance have not been investigated. Generally, the mechanical load drives normal physiological properties of the tendon. But, mechanical overload/burden exerts stress on tenocytes, and disrupts the tendon microenvironment by triggering a multitude of signaling pathways leading to extracellular matrix remodeling, disorganization, alteration in collagen composition and apoptosis. These events result in weak tendon which is highly susceptible to rupture or tear. In this article, we critically reviewed the intrinsic signaling pathways that are excessively triggered by continuous mechanical load and the counteracting physiological responses and associated derangements. The elucidation of the molecular events underlying mechanical stress-induced symptomatic/asymptomatic tendinopathy could provide information on potential target sites for translational application in the management of rotator cuff disorders.

Changing Body Movement Patterns in 9-Year-Old Baseball Pitchers: A Pilot Study.

BACKGROUND: Arm injuries in throwing athletes continue to increase. Injuries may be due to multiple variables, including inefficient body movement patterns, especially in young baseball throwers. It is unclear whether these patterns can be efficiently altered in this population. PURPOSE/HYPOTHESIS: To investigate the effect of a novel 21-day throwing program on body movement patterns in youth baseball players using common practical tools. Our hypothesis was that this program would change body movement patterns over a relatively short period. STUDY DESIGN: Descriptive laboratory study. METHODS: Ten 9-year-old baseball athletes were asked to participate in a 21-consecutive day throwing program focused on decreasing inefficiencies. All participants underwent video evaluation from 2 vantage points as well as radar evaluation before and after the programs. Throwing arm humerothoracic and antecubital angles as well as pelvic angles in the frontal view were measured at the time of front (directional) leg heel/toe down (late cocking) for each of 3 pitches. Glove-side humerothoracic angles and back leg minimum popliteal angles were measured from behind for each of 3 additional pitches. Velocity was measured using a radar gun. All angular measurements were performed by a physical therapist blinded to the purposes of the program and study as well as to video chronology. RESULTS: Throwing arm antecubital angle (P = .01) and humerothoracic angle (P = .03) as well as back leg minimum popliteal angle (P = .03) all decreased, with mean decreases of 35°, 10°, and 8°, respectively. Velocity increased with decreased back leg popliteal angles (P = .019); mean velocity increased 2.6 mph (P = .016). CONCLUSION: Young baseball throwers can quickly retrain their bodies to accomplish different movement patterns. CLINICAL RELEVANCE: This novel throwing program may have implications for injury prevention and treatment as we identify better baseball-throwing movement patterns.

Pain and the pathogenesis of biceps tendinopathy.

Biceps tendinopathy is a relatively common ailment that typically presents as pain, tenderness, and weakness in the tendon of the long head of the biceps brachii. Though it is often associated with degenerative processes of the rotator cuff and the joint, this is not always the case, thus, the etiology remains considerably unknown. There has been recent interest in elucidating the pathogenesis of tendinopathy, since it can be an agent of chronic pain, and is difficult to manage. The purpose of this article is to critically evaluate relevant published research that reflects the current understanding of pain and how it relates to biceps tendinopathy. A review of the literature was conducted to create an organized picture of how pain arises and manifests itself, and how the mechanism behind biceps tendinopathy possibly results in pain. Chronic pain is thought to arise from neurogenic inflammation, central pain sensitization, excitatory nerve augmentation, inhibitory nerve loss, and/or dysregulation of supraspinal structures; thus, the connections of these theories to the ones regarding the generation of biceps tendinopathy, particularly the neural theory, are discussed. Pain mediators such as tachykinins, CGRP, and alarmins, in addition to nervous system ion channels, are highlighted as possible avenues for research in tendinopathy pain. Recognition of the nociceptive mechanisms and molecular of biceps tendinopathy might aid in the development of novel treatment strategies for managing anterior shoulder pain due to a symptomatic biceps tendon.

Vitamin D and Its Effects on Articular Cartilage and Osteoarthritis.

BACKGROUND: Osteoarthritis (OA) currently affects 10% of the American population. There has been a recent push to determine exactly what causes OA and how it can be treated most effectively. Serum vitamin D levels have been associated with OA and may have an effect on articular cartilage remodeling. PURPOSE: To critically review the published research on the effect of vitamin D on articular cartilage and the development of OA as well as on the mechanism behind cartilage regeneration and degeneration. STUDY DESIGN: Review. METHODS: A systematic search of PubMed and the Web of Science was performed for relevant studies published in the English language through April 30, 2016, using the terms vitamin D, articular cartilage, and osteoarthritis. RESULTS: On a molecular level, 1α,25(OH)2D3, the activated form of vitamin D, plays a role in articular cartilage degeneration. Vitamin D binds to vitamin D receptors, triggering a signaling cascade that leads to chondrocyte hypertrophy. In clinical trials, vitamin D deficiency poses a risk factor for OA, and those with decreased cartilage thickness are more likely to be vitamin D-insufficient. CONCLUSION: The role of vitamin D supplementation in the treatment or prevention of OA remains uncertain. More research is needed to reconcile these conflicting findings.