Impact of aging on tendon homeostasis, tendinopathy development, and impaired healing

Aging is a complex and progressive process where the tissues of the body demonstrate a decreased ability to maintain homeostasis. During aging, there are substantial cellular and molecular changes, with a subsequent increase in susceptibility to pathological degeneration of normal tissue function. In tendon, aging results in well characterized alterations in extracellular matrix (ECM) structure and composition. In addition, the cellular environment of aged tendons is altered, including a marked decrease in cell density and metabolic activity, as well as an increase in cellular senescence. Collectively, these degenerative changes make aging a key risk factor for the development of tendinopathies and can increase the frequency of tendon injuries. However, inconsistencies in the extent of age-related degenerative impairments in tendons have been reported, likely due to differences in how "old" and "young" age-groups have been defined, differences between anatomically distinct tendons, and differences between animal models that have been utilized to study the impact of aging on tendon homeostasis. In this review, we address these issues by summarizing data by well-defined age categories (young adults, middle-aged, and aged) and from anatomically distinct tendon types. We then summarize in detail how aging affects tendon mechanics, structure, composition, and the cellular environment based on current data and underscore what is currently not known. Finally, we discuss gaps in the current understanding of tendon aging and propose key avenues for future research that can shed light on the specific mechanisms of tendon pathogenesis due to aging.

Targeting Senescent Tendon Stem/Progenitor Cells to Prevent or Treat Age-Related Tendon Disorders

Age-related tendon disorder, a primary motor system disease, is characterized by biological changes in the tendon tissue due to senescence and seriously affects the quality of life of the elderly. The pathogenesis of this disease is not well-understood. Tendon stem/progenitor cells (TSPCs) exhibit multi-differentiation capacity. These cells are important cellular components of the tendon because of their roles in tendon tissue homeostasis, remodeling, and repair. Previous studies revealed alterations in the biological characteristics and tenogenic differentiation potential of TSPCs in senescent tendon tissue, in turn contributing to insufficient differentiation of TSPCs into tenocytes. Poor tendon repair can result in age-related tendinopathies. Therefore, targeting of senescent TSPCs may restore the tenogenic differentiation potential of these cells and achieve homeostasis of the tendon tissue to prevent or treat age-related tendinopathy. In this review, we summarize the biological characteristics of TSPCs and histopathological changes in age-related tendinopathy, as well as the potential mechanisms through which TSPCs contribute to senescence. This information may promote further exploration of innovative treatment strategies to rescue TSPCs from senescence.

The value of the peroneus brevis tendon cross-sectional area in early diagnosing of peroneus brevis tendinitis: The peroneus brevis tendon cross-sectional area

A thickened peroneus brevis tendon has been considered to be an important morphologic parameter of peroneus brevis tendinitis (PBT). Previous researchers have found that the peroneus brevis tendon thickness (PBTT) is correlated with inflammation of the peroneus brevis tendon. However, inflammatory hypertrophic change is different from simple thickness. Thus, we devised the peroneus brevis tendon cross-sectional area (PBTCSA) as a new diagnostic parameter to analyze the hypertrophy of the whole PBT. We assumed that the PBTCSA is a major morphologic parameter useful for early PBT diagnosis. Peroneus brevis tendon images were collected from 22 patients with PBT and from 22 normal subjects who underwent ankle-magnetic resonance imaging and revealed no evidence of PBT. The T1-weighted axial ankle-magnetic resonance imaging images were evaluated at the ankle level from all participants. The PBTT was measured as the thickest point at the transverse image of the peroneus brevis tendon. The PBTCSA was measured as the cross-sectional ligament whole area of the peroneus brevis tendon that was most hypertrophied in the axial A-MR images. The average PBTT was 2.22 ± 0.29 mm in the normal group and 2.85 ± 0.36 mm in the PBT group. The average PBTCSA was 6.98 ± 1.54 mm2 in the normal group and 13.11 ± 2.45 mm2 in the PBT group. PBT patients had significantly greater PBTT (P < .001) and PBTCSA (P < .001) than the normal group did. A receiver operating characteristic curve analysis revealed that the most suitable cutoff value of the PBTT was 2.51 mm, with 81.8% sensitivity and 81.8% specificity, and an AUC for the score was 0.93. The most suitable cutoff value of the PBTCSA was 10.08 mm2, with 90.9% sensitivity and 90.9% specificity, and AUC for the score was 0.98. Even though the PBTT and PBTCSA were both significantly associated with PBT, the PBTCSA was a more sensitive diagnostic parameter.

Irisin promotes the proliferation and tenogenic differentiation of rat tendon-derived stem/progenitor cells via activating YAP/TAZ

Tendinopathy is a common tendon disorder characterized by pain, swelling, and dysfunction. Current evidence has demonstrated that the depletion of stem cell pool and non-tenogenic differentiation of tendon-derived stem/progenitor cells (TSPCs) might account for the pathogenesis of tendinopathy. FNDC5/Irisin, as a novel exercise-induced myokine, is proved to be involved in the exercise-induced protective effects on musculoskeletal disorders. However, whether irisin can affect TSPCs fate is still unknown. To ascertain the roles of irisin on the proliferation and tenogenic differentiation of TSPCs, rat TSPCs were isolated and incubated with irisin. Cell viability, phenotypic changes, and related signaling pathways were evaluated by CCK-8 assay, colony formation assay, real-time PCR, Western blot, immunofluorescence, and proteasome activity assay. We found that irisin treatment increased the proliferative and colony-forming abilities, and promoted the tenogenic differentiation of TSPCs by upregulating the expression of YAP/TAZ. In conclusion, our work showed for the first time that irisin promotes the proliferation and tenogenic differentiation of rat TSPCs in vitro by activating YAP/TAZ, and the process was associated with a ubiquitin-proteasome proteolytic pathway. In conclusion, irisin and agents targeting YAP/TAZ may be promising therapeutic options for tendinopathy.

[Magnetic resonance imaging analysis on the effect of marathon on the dynamic changes of morphological characteristics of patellar tendon in amateur marathon runners after half marathon]

Objective: To explore the dynamic changes of morphological characteristics of patellar tendon (PT) in amateur athletes after a half-marathon using magnetic resonance imaging. Methods: A total of 19 male amateur marathon runners with 38 knee joints,aged from 26 to 53(41.5±7.9) years, running for 3 to 18 years, with a weekly running volume of 30-90 km and a monthly running volume of 100-300 km were enrolled and underwent 1.5T MRI scan before the half-marathon, within 3 hours after running and 3 days after running. Ten healthy male volunteers with 20 knee joints, who had never participated in marathon and exercised (including but not limited to running) per week for less than 150 minutes were recruited as the control group, aged from 26 to 54 (39.4±9.1) years. Firstly, the PT signal was qualitatively assessed on fat-suppressed proton density-weighted imaging (fs-PDWI) sequence to observe the presence of patellar tendinitis. Then, the length, proximal, middle and distal cross-sectional area (CSA), and volume of PT were measured using the post-processing tool ITK-SNAP, and the data were standardized. The independent sample t-test was used for comparing. One-way repeated measures analysis of variance was used to analyze the morphological changes of PT before and after half-marathon running. Results: The incidence of asymptomatic patellar tendinitis in amateur marathon runners was 26.3% (5/19). No significant MR signal changes of PT were observed in all runners after running. The proximal CSA in runners group was larger than that in controls [(4.20±0.62) mm²/kg^3/4 vs (3.63±0.57) mm²/kg^3/4, P<0.05], and there was no significant difference in length, medium and distal CSA and volume(all P>0.05). The length, proximal and distal CSA and volume of PT in runners group increased at 3 h after running [(47.35±3.22) mm vs (46.83±3.35) mm; (102.52±13.03) mm² vs (98.98±13.14) mm²; (108.67±15.72) mm² vs (100.27±14.37) mm²; (4 020.36±514.38) mm³ vs (3 826.57±499.23) mm³, all P<0.05]. There was no significant difference between before running and 3 days after running(all P>0.05). The middle CSA were not significantly different among different periods(all P>0.05). Conclusion: Marathon has effect on the normal PT morphology in male amateur marathon runners, showing an increase in proximal CSA. A half-marathon will cause reversible changes in PT length, regional CSA and volume.

Evaluating the role of type 2 diabetes mellitus in rotator cuff tendinopathy: Development and analysis of a novel rat model

OBJECTIVE

To establish and validate an intact rotator cuff rat model for exploring the pathophysiological effects of type 2 diabetes on the rotator cuff tendon in vivo.

METHODS

A total of 45 adult male rats were randomly divided into a control group (n = 9) and type 2 diabetes group (n=36). The rats were sacrificed at 2 weeks (T2DM-2w group, n=9), 4 weeks (T2DM-4w group, n=9), 8 weeks (T2DM-8w group, n=9), and 12 weeks (T2DM-12w group, n=9) after successful modeling of type 2 diabetes. Bilateral shoulder samples were collected for gross observation and measurement, protein expression(enzyme-linked immunosorbent assay,ELISA), histological evaluation, biomechanical testing, and gene expression (real-time quantitative polymerase chain reaction, qRT-PCR).

RESULTS

Protein expression showed that the expression of IL-6 and Advanced glycation end products (AGEs)in serum increased in type 2 diabetic group compared with the non-diabetic group. Histologically, collagen fibers in rotator cuff tendons of type 2 diabetic rats were disorganized, ruptured, and with scar hyperplasia, neovascularization, and extracellular matrix disturbances, while Bonar score showed significant and continuously aggravated tendinopathy over 12 weeks. The biomechanical evaluation showed that the ultimate load of rotator cuff tendons in type 2 diabetic rats gradually decreased, and the ultimate load was negatively correlated with AGEs content. Gene expression analysis showed increased expression of genes associated with matrix remodeling (COL-1A1), tendon development (TNC), and fatty infiltration (FABP4) in tendon specimens from the type 2 diabetic group.

CONCLUSION

Persistent type 2 diabetes is associated with the rupture of collagen fiber structure, disturbance in the extracellular matrix, and biomechanical decline of the rotator cuff tendon. The establishment of this new rat model of rotator cuff tendinopathy provides a valuable research basis for studying the cellular and molecular mechanisms of diabetes-induced rotator cuff tendinopathy.

What Is the Efficacy of a Nonoperative Program Including a Specific Stretching Protocol for Flexor Hallucis Longus Tendonitis?

BACKGROUND

Diagnosis and treatment of tendonitis/entrapment of the flexor hallucis longus (FHL) has been sporadically described in the evidence, primarily in the context of dancers and other athletes. Although various nonspecific nonoperative treatments have been described, it is not clear how often they achieve a satisfactory amount of symptom improvement.

QUESTIONS/PURPOSES

The present study was designed to address the following questions regarding the nonoperative treatment of FHL tendonitis: (1) In a population of patients where the default management option for FHL tendonitis is a comprehensive nonsurgical approach, what proportion of patients thus treated opted not to have surgery? (2) What factors were associated with a patient's decision to undergo surgery after a period of nonsurgical management?

METHODS

The 656 patients included were all those diagnosed with FHL tendonitis who were initially treated nonoperatively in the foot and ankle division between January 2009 and December 2018. Demographics, comorbidities, examination findings, imaging results, pain scores, treatment instituted, and final outcome were obtained from the electronic medical record. The primary outcome was the decision to have surgery due to unsatisfactory symptom improvement. We compared patients who opted for surgery with those who did not after nonoperative treatment with univariable and multivariable statistics using demographics, comorbidities, and clinical findings as potential risk factors, with p < 0.05.

RESULTS

Forty-four percent (180 of 409) of patients decided to forgo surgery after the institution of a specific FHL stretching program. Surgery was more likely in patients with clinical hallux rigidus (OR 2.4 [95% CI 1.16 to 4.97]; p = 0.02) or posteromedial ankle pain (OR 1.78 [95% CI 1.12 to 2.83]; p = 0.01) and less likely in those who completed an FHL stretching program (OR 0.15 [95% CI 0.08 to 0.27]; p < 0.001).

CONCLUSION

FHL tendonitis is more common than the previous evidence suggests and frequently occurs in nonathletes. Once it was diagnosed by detection of tenderness anywhere along the tendon, most frequently at the fibroosseous tunnel, nonoperative treatment focused on specific FHL stretching and immobilization in more severe cases reduced the symptoms to the extent that 44% of patients decided that surgery was unnecessary. The key to its diagnosis is awareness that this injury is possible because most patients treated in this study had been previously seen by orthopaedic providers who had not appreciated the presence of the condition, leading to a delay in diagnosis and treatment of more than a year in many patients.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Single-cell transcriptomic profiling reveals distinct mechanical responses between normal and diseased tendon progenitor cells

Regenerative medicine approaches utilizing stem cells offer a promising strategy to address tendinopathy, a class of common tendon disorders associated with pain and impaired function. Tendon progenitor cells (TPCs) are important in healing and maintaining tendon tissues. Here we provide a comprehensive single cell transcriptomic profiling of TPCs from three normal and three clinically classified tendinopathy samples in response to mechanical stimuli. Analysis reveals seven distinct TPC subpopulations including subsets that are responsive to the mechanical stress, highly clonogenic, and specialized in cytokine or growth factor expression. The single cell transcriptomic profiling of TPCs and their subsets serves as a foundation for further investigation into the pathology and molecular hallmarks of tendinopathy in mechanical stimulation conditions.

Radiocapitellar incongruity of the radial head in magnetic resonance imaging correlates with pathologic changes of the lateral elbow stabilizers in lateral epicondylitis

OBJECTIVE

Post-traumatic posterolateral rotatory instability (PLRI) can be shown as radiocapitellar incongruity or posterior translation (PT) of the radial head in magnetic resonance imaging (MRI). We aimed to evaluate whether PT correlated with pathologic changes of lateral elbow stabilizers in patients with lateral epicondylitis.

MATERIALS AND METHODS

In MRIs of 160 patients with lateral epicondylitis, we measured PT of the radial head in the sagittal images. We qualitatively graded five lesions of the lateral elbow structures that included common extensor tendon (CET) lesion (grade 1-3), lateral collateral ligament complex (LCLC) insufficiency (grade 0-2), and absence or presence of bone marrow signal change, osteochondral lesion, and calcification. We analyzed whether the PT correlated with pathologic changes of the lateral elbow stabilizers and evaluated the diagnostic value of the PT for severe lesions.

RESULTS

The average PT was 1.9 mm. The PT correlated with both the CET lesion (p < 0.001) and LCLC insufficiency (p < 0.001). The optimal cutoff values of the PT for grade 3 CET lesion and grade 2 LCLC lesion were 2.6 and 2.8 mm, respectively. When potential PLRI was defined as the PT of > 3.4mm as suggested for post-traumatic PLRI, 21 patients had potential PLRI. The positive predictive values of the PT > 3.4mm were 76% for grade 3 CET lesions and 67% for grade 2 LCLC insufficiency.

CONCLUSION

This study demonstrates that PT of the radial head correlates with pathological changes of the lateral elbow stabilizers. As radiocapitellar incongruity is easy to measure quantitatively, it can be used for screening potential PLRI in patients with lateral epicondylitis.

Spironolactone Ameliorates Senescence and Calcification by Modulating Autophagy in Rat Tendon-Derived Stem Cells via the NF-κB/MAPK Pathway

Tendinopathy is a disabling musculoskeletal disease, the pathological process of which is tightly associated with inflammation. Spironolactone (SP) has been widely used as a diuretic in clinical practice. Recently, SP has shown anti-inflammatory features in several diseases. Tendon-derived stem cells (TDSCs), a subset cell type from tendon tissue possessing clonogenic capacity, play a vital role in the pathological process of tendinopathy. In the present study, the protective effect of SP on TDSCs was demonstrated under simulated tendinopathy conditions both in vitro and in vivo. SP contributed to the maintenance of TDSC-specific genes or proteins, while suppressing the interleukin- (IL-) 1β-induced overexpression of inflammation-mediated factors. Additionally, IL-1β-induced cellular senescence in TDSCs was inhibited, while autophagy was enhanced, as determined via β-galactosidase activity, western blot (WB), and quantitative real-time polymerase chain reaction analysis. With the aid of several emerging bioinformatics tools, the mitogen-activated protein kinase (MAPK) pathway likely participated in the effect of SP, which was further validated through WB analysis and the use of MAPK agonist. Immunofluorescence analysis and an NF-κB agonist were used to confirm the inhibitory effect of SP on IL-1β-induced activation of the NF-κB pathway. X-ray, immunofluorescence, immunohistochemistry, hematoxylin and eosin staining, histological grades, and Masson staining showed that SP ameliorated tendinopathy in an Achilles tenotomy (AT) rat model in vivo. This work elucidates the protective role of SP on the pathological process of tendinopathy both in vitro and in vivo, indicating a potential therapeutic strategy for tendinopathy treatment.

Platelet-rich plasma for rotator cuff tendinopathy: A systematic review and meta-analysis

Shoulder rotator cuff tendinopathy is a common debilitating condition that affects a person daily function and the quality of life. Despite its frequent occurrence, the best treatment is still inconclusive. This review assessed the clinical effect of platelet-rich plasma injection for rotator cuff tendinopathy. A systematic literature search was conducted using CINAHL, Medline, SCOPUS, SPORTSDiscus and Web of Science databases to retrieve articles published in peer-reviewed journals until December 2020. Randomised controlled trials (RCTs), which compared clinical effects of PRP injection to the usual care among adults diagnosed with rotator cuff conditions were reviewed. The main outcomes of interest were changes in shoulder pain symptoms and shoulder functions. All variables were analysed using random effects meta-analyses. Eight RCTs were reviewed in this study. The risk of bias for randomization was low for 6 RCTs, one study had unclear risk and the other was a high risk. Studies vary on the PRP techniques including preparation and injections. Moreover, the control intervention also differs. Four studies compared PRP with normal saline injection while in the remaining 4 RCTs the control intervention were rehabilitation program and dry needling. Meta-analysis of selected studies showed that PRP injection was safe and effective intervention for long-term pain control and shoulder function in patients with RC disorders.

Topical diclofenac vs placebo for the treatment of chronic Achilles tendinopathy: A randomized controlled clinical trial

INTRODUCTION

The application of topical diclofenac has been suggested as a possible treatment for Achilles tendinopathy. Our aim was to answer the question, is topical diclofenac more effective than placebo for the treatment of Achilles tendinopathy?.

METHODS

67 participants with persistent midportion or insertional Achilles tendinopathy were randomly assigned to receive a 4 week course of 10% topical diclofenac (n = 32) or placebo (n = 35). The a priori primary outcome measure was change in severity of Achilles tendinopathy (VISA-A score) at 4 and 12 weeks. Secondary outcome measures included numeric pain rating, and patient-reported change in symptoms using a 7 point scale, from substantially worse to substantially better. Pressure pain threshold (N) and transverse tendon stiffness (N/m) were measured over the site of maximum Achilles tendon pathology at baseline and 4 weeks.

RESULTS

There were no statistically or clinically significant differences between the diclofenac and placebo groups in any of the primary or secondary outcome measures at any timepoint. Average VISA-A score improved in both groups (p<0.0001), but the improvements were marginal: at 4 weeks, the improvements in VISA-A were 9 (SD 11) in the diclofenac group and 8 (SD 12) in the placebo group, and at 12 weeks the improvements were 9 (SD 16) and 11 (SD13) respectively-these average changes are smaller than the minimum clinically important difference of the VISA-A.

CONCLUSION

The regular application of topical diclofenac for Achilles tendinopathy over a 4 week period was not associated with superior clinical outcomes to that achieved with placebo.

Moderate and intensive mechanical loading differentially modulate the phenotype of tendon stem/progenitor cells in vivo

To examine the differential mechanobiological responses of specific resident tendon cells, we developed an in vivo model of whole-body irradiation followed by injection of either tendon stem/progenitor cells (TSCs) expressing green fluorescent protein (GFP-TSCs) or mature tenocytes expressing GFP (GFP-TNCs) into the patellar tendons of wild type C57 mice. Injected mice were subjected to short term (3 weeks) treadmill running, specifically moderate treadmill running (MTR) and intensive treadmill running (ITR). In MTR mice, both GFP-TSC and GFP-TNC injected tendons maintained normal cell morphology with elevated expression of tendon related markers collagen I and tenomodulin. In ITR mice injected with GFP-TNCs, cells also maintained an elongated shape similar to the shape found in normal/untreated control mice, as well as elevated expression of tendon related markers. However, ITR mice injected with GFP-TSCs showed abnormal changes, such as cell morphology transitioning to a round shape, elevated chondrogenic differentiation, and increased gene expression of non-tenocyte related genes LPL, Runx-2, and SOX-9. Increased gene expression data was supported by immunostaining showing elevated expression of SOX-9, Runx-2, and PPARγ. This study provides evidence that while MTR maintains tendon homeostasis by promoting the differentiation of TSCs into TNCs, ITR causes the onset of tendinopathy development by inducing non-tenocyte differentiation of TSCs, which may eventually lead to the formation of non-tendinous tissues in tendon tissue after long term mechanical overloading conditions on the tendon.

Molecular and Structural Effects of Percutaneous Interventions in Chronic Achilles Tendinopathy

Achilles tendinopathy (AT) is a common problem, especially in people of working age, as well as in the elderly. Although the pathogenesis of tendinopathy is better known, therapeutic management of AT remains challenging. Various percutaneous treatments have been applied to tendon lesions: e.g., injectable treatments, platelet-rich plasma (PRP), corticosteroids, stem cells, MMP inhibitors, and anti-angiogenic agents), as well as percutaneous procedures without any injection (percutaneous soft tissue release and dry needling). In this review, we will describe and comment on data about the molecular and structural effects of these treatments obtained in vitro and in vivo and report their efficacy in clinical trials. Local treatments have some impact on neovascularization, inflammation or tissue remodeling in animal models, but evidence from clinical trials remains too weak to establish an accurate management plan, and further studies will be necessary to evaluate their value.

A Clinician's Guide to Femoacetabular Impingement in Athletes

Femoroacetabular impingement (FAI) is the most common cause of hip pain in both professional and recreational athletes. It is caused by abnormal bone development on both the acetabulum and proximal femur as a result of genetic factors and in reaction to high-volume athletics participation. Athletes typically become symptomatic after reaching skeletal maturity and commonly describe deep groin pain that worsens with activities such as squatting, cutting, or pivoting motions. For this reason, sports such as hockey, football, and soccer can be particularly irritating to an athlete with FAI. Moreover, the athlete with FAI often presents with contaminant hip and pelvis pathologies such as athletic pubalgia and iliopsoas tendinopathy that must also be addressed. While this pain often limits performance or participation in sports, perhaps the most significant ramification of FAI is the role it plays in driving early onset osteoarthritis. Fortunately, FAI can be reliably diagnosed through careful history taking, appropriate provocative physical exam maneuvers, and familiarity with hallmark radiographic features. The aims of this review are to provide clinicians with information regarding the pathogenesis of FAI, to thoroughly describe the classic history and physical exam elements, and to introduce various management strategies for athletes suffering from FAI.

Association of estrogen receptor β polymorphisms with posterior tibial tendon dysfunction

Posterior tibial tendon (PTT) dysfunction is three times more common in females, and some patients may have a predisposition without a clinically evident cause, suggesting that individual characteristics play an important role in tendinopathy. The present study investigated the association of rs4986938 (+ 1730G > A; AluI RFLP) and rs1256049 (- 1082G > A; RsaI RFLP) single nucleotide polymorphisms (SNPs) of estrogen receptor-beta (ER-β) gene with PTT dysfunction. A total of 400 participants were recruited. The PTT dysfunction group: these patients underwent surgery, with PTT tendinopathy confirmed by histopathology and magnetic resonance image (MRI). The control group was composed of participants with no clinical or MRI evidence of PTT dysfunction. Each group was composed of 100 postmenopausal women, 50 premenopausal women, and 50 men. Genomic DNA was extracted from saliva samples, and genotypes were obtained by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP). Concerning the ER-β SNP rs4986938, there were significant differences in the frequencies of alleles between test and control groups of all the cases, only postmenopausal women and only men (p < 0.0001, p = 0.0016 and p = 0.0001). Considering the PTT dysfunction group and comparing postmenopausal women versus premenopausal women adding men, the analysis showed significant differences in the allelic distribution (p = 0.0450): the allele A in postmenopausal women is a risk factor. The ER-β SNP rs1256049 did not show differences in the frequencies of alleles and genotypes between groups. The ER-β SNP rs4986938, but not ER -β SNPs rs1256049, may contribute to PTT insufficiency in the Brazilian population, with additional risk in postmenopausal women. Addition, in men the genetic factor could be more determinant.

Bilateral changes in tendon structure of patients diagnosed with unilateral insertional or midportion achilles tendinopathy or patellar tendinopathy

PURPOSE

Changes in tendon structure are commonly seen in patients with unilateral achilles (AT) or patellar (PT) tendinopathy but might also be present on the asymptomatic side, indicating a higher risk for developing symptoms. The aim of this study is to compare tendon structure of the symptomatic side with the asymptomatic side in AT and PT patients and control subjects.

METHODS

A total of 46 patients with unilateral AT (16 insertional and 30 midportion) and 38 with unilateral PT were included. For the control group, a total of 18 Achilles tendons and 25 patellar tendons were scanned. Tendon structure was assessed using ultrasound tissue characterisation (UTC), which quantifies tendon organisation dividing the structure into four different echo types (I-IV).

RESULTS

There were significant differences in echo types I, III, and IV between symptomatic and asymptomatic sides and controls. Additionally, there was a significant difference between the symptomatic and the asymptomatic side for all tendinopathy locations. In the insertional AT tendon portion, the symptomatic side showed a higher percentage of echo type III. For the midportion AT, the symptomatic side showed a lower percentage of echo type I and a higher percentage of echo types III and IV. For the patellar tendon, the symptomatic side showed a higher percentage of echo types III and IV. All differences were higher than the minimal detectable changes.

CONCLUSION

Although patients have symptoms unilaterally, the tendon structures are compromised on both sides. These results stress the importance of monitoring both symptomatic and asymptomatic tendon structures and in addition highlight that the asymptomatic side should not be used as reference in clinical practice.

LEVEL OF EVIDENCE

III.

Assessing the effects of intratendinous genipin injections: Mechanical augmentation and spatial distribution in an ex vivo degenerative tendon model

Background

Tendinopathy is a common musculoskeletal disorder and current treatment options show limited success. Genipin is an effective collagen crosslinker with low cytotoxicity and a promising therapeutic strategy for stabilizing an intratendinous lesion.

Purpose

This study examined the mechanical effect and delivery of intratendinous genipin injection in healthy and degenerated tendons.

Study design

Controlled laboratory study

Methods

Bovine superficial digital flexor tendons were randomized into four groups: Healthy control (N = 25), healthy genipin (N = 25), degenerated control (N = 45) and degenerated genipin (N = 45). Degeneration was induced by Collagenase D injection. After 24h, degenerated tendons were subsequently injected with either 0.2ml of 80mM genipin or buffer only. 24h post-treatment, samples were cyclically loaded for 500 cycles and then ramp loaded to failure. Fluorescence and absorption assays were performed to analyze genipin crosslink distribution and estimate tissue concentration after injection.

Results

Compared to controls, genipin treatment increased ultimate force by 19% in degenerated tendons (median control 530 N vs. 633 N; p = 0.0078). No significant differences in mechanical properties were observed in healthy tendons, while degenerated tendons showed a significant difference in ultimate stress (+23%, p = 0.049), stiffness (+27%, p = 0.037), work to failure (+42%, p = 0.009), and relative stress relaxation (-11%, p < 0.001) after genipin injection. Fluorescence and absorption were significantly higher in genipin treated tendons compared to control groups. A higher degree of crosslinking (+45%, p < 0.001) and a more localized distribution were observed in the treated healthy compared to degenerated tendons, with higher genipin tissue concentrations in healthy (7.9 mM) than in degenerated tissue (2.3 mM).

Conclusion

Using an ex-vivo tendinopathy model, intratendinous genipin injections recovered mechanical strength to the level of healthy tendons. Measured by genipin tissue distribution, injection is an effective method for local delivery.

Clinical relevance

This study provides a proof of concept for the use of intratendinous genipin injection in the treatment of tendinopathy. The results demonstrate that a degenerated tendon can be mechanically augmented by a clinically viable method of local genipin delivery. This warrants further in vivo studies towards the development of a clinically applicable treatment based on genipin.

Recovery of Tendon Characteristics by Inhibition of Aberrant Differentiation of Tendon-Derived Stem Cells from Degenerative Tendinopathy

The inhibition of the aberrant differentiation of tendon-derived stem cells (TDSCs) is a major target for the regeneration of damaged tendon tissues, as tendinopathy can be caused by the aberrant differentiation of TDSCs. We investigated whether the possible aberrant differentiation of TDSCs can be prevented by using adequate inhibitors. TDSCs extracted from chemically induced tendinopathy and injury-with-overuse tendinopathy models were cultured with 18α-glycyrrhetinic acid (AGA) and T0070907 to block osteogenic differentiation and adipogenic differentiation, respectively. The optimal dose of AGA decreased the osteogenic-specific marker Runx2 (Runt-related transcription factor 2), and T0070907 blocked the adipogenic-specific marker peroxisome proliferator-activated receptor gamma (PPARγ) in mRNA levels. We also found that AGA induced tenogenic differentiation in mRNA levels. However, T0070907 did not affect the tenogenic differentiation and regenerative capacity of TDSCs. We expect that optimal doses of AGA and T0070907 can prevent tendinopathy by inhibiting osteogenic and adipogenic differentiation, respectively. In addition, AGA and T0070907 may play important roles in the treatment of tendinopathy.

Sonoanatomy and Pathology of the Gluteus Minimus Tendon

Gluteus minimus disorders are a potential source of greater trochanteric or anterior hip pain. Disorders of the gluteus minimus tendon most commonly occur in conjunction with gluteus medius tendon abnormalities but can also occur in isolation. Understanding the sonoanatomy of the gluteus minimus muscle-tendon unit is a prerequisite for recognizing and characterizing gluteus minimus tendon disorders, which, in turn, guides treatment for patients with greater trochanteric or anterior hip pain syndromes.

Ultrasound Doppler Flow in Patients With Chronic Midportion Achilles Tendinopathy: Is Surface Area Quantification a Reliable Method?

OBJECTIVES

Ultrasound assessments of patients with chronic midportion Achilles tendinopathy include determining the degree of neovascularization using Doppler flow. A frequently used measure to quantify neovascularization is the modified Öhberg score. It is unknown whether the semiquantitative modified Öhberg score (0-4+) has higher reliability than a quantified measure of Doppler flow (0-100%). The purpose of this cross-sectional study was to evaluate the interobserver reliability of the modified Öhberg score and a surface area quantification (SAQ) method for Doppler flow in patients with chronic midportion Achilles tendinopathy.

METHODS

Two observers examined the degree of Doppler flow independently using SAQ and the modified Öhberg score during a single consultation. The intraclass correlation coefficient, standard error of measurement, and minimal detectable difference were determined to evaluate the reliability and measurement properties of the SAQ method and the modified Öhberg score.

RESULTS

In total, 28 consecutive patients with chronic midportion Achilles tendinopathy participated. The intraclass correlation coefficient for interobserver reliability of the SAQ method was 0.81 (95% confidence interval, 0.58-0.91), compared to 0.64 (95% confidence interval, 0.45-0.81) for the modified Öhberg score. The standard error of measurement and minimal detectable difference values for the SAQ method were 2.9% and 8.0%, respectively, and for the modified Öhberg score, they were 0.55 and 1.53 points.

CONCLUSIONS

The SAQ method shows good reliability to evaluate the degree of Doppler flow in patients with chronic midportion Achilles tendinopathy, and it overcomes the ceiling effect of the modified Öhberg score. Future research should focus on the relationship between the SAQ method and clinical outcomes and use this method to monitor treatment responses.

Calcific Tendinitis in the Elbow Presented as Acute Tennis Elbow

Calcific tendinitis occurs frequently in shoulder and hip region. Its occurrence in elbow joint is frequently misdiagnosed because of its rare incidence and similar clinical presentation with other acute conditions of elbow like trauma, infection and tennis elbow. Characteristic symptoms of this condition are acute onset of pain, tenderness and swelling on the lateral aspect the elbow. Plain Radiograph is the primary modality to distinguish and evaluate this condition. Awareness and familiarity with this condition helps in early diagnosis and avoids unnecessary treatments and biopsy as this condition is self-limited. Keywords: Calcific tendinitis; self-limited; tennis elbow.

Laryngeal gout mimicking chondrosarcoma with concurrent longus colli tendinitis

A 42-year-old man with multiple comorbidities, including gout, presented to the emergency department with severe odynophagia for 4 days with intermittent dysphagia for 1-2 months. A CT scan of the neck showed right longus colli tendinitis and partially calcified excrescences from the right thyroid cartilage which raised suspicion of a cartilaginous tumour. He underwent an MRI scan of the neck to better evaluate the thyroid cartilage findings, which showed a heterogeneous mass suspicious for a chondroid tumour. He then underwent a positron-emission tomography-CT scan which showed a fluorodeoxyglucose-avid mass containing foci of calcification involving the right thyroid cartilage and adjacent strap muscle, with high standardised uptake value of 7.7. He subsequently underwent a CT-guided biopsy and an open biopsy of the right thyroid cartilage, and the results revealed gouty tophi. To our knowledge, this is the first reported case of laryngeal gout with longus coli tendinitis, both of which are rare conditions.

A comprehensive ultrasonographic investigation of the common flexor tendon and medial epicondyle in asymptomatic individuals

AIM

To investigate the common flexor tendon (CFT) thickness and the frequency of ultrasound (US) pathological alterations in its structure in a healthy population and to evaluate if these findings can be correlated with dominant hand, age, gender, body mass index, workload, menopause status.

MATERIAL AND METHODS

The study population consisted of 111 healthy volunteers. Bilateral CFT thicknesses were measured at 5 mm, 10 mm and 15 mm distance to medial epicondyle. Tendon echotexture, tears, calcification, enthesophyte, and neovascularization were also evaluated.

RESULTS

The CFT was thicker on the dominant side at all three locations (2.1 versus 1.9 mm proximal, 4.0 versus 3.7 mm in the middle and 7.0 versus 6.6 mm distal, all p<0.05). Thickness correlated negatively with postmenopausal duration in all landmarks, except for the nondominant side distal part and positive with body mass index, significantly on the dominant side proximal and middle parts. A statistically significant correlation was found between heavy workers group and tendon thicknesses on the proximal and middle parts of the dominant side and the distal part of the non-dominant sides. US tendinosis was detected in 24/222 tendons, calcification in 11/222 tendons and enthesophyte in 33/222 tendons. The threshold age was 46.5 years for enthesophytes and 51.5 years for calcifications. The prevalence of calcification and enthesophyte tended to be higher in blue-collar workers and on the dominant side.

CONCLUSIONS

The CFT thickness varies depending on measurement locations, handedness, body mass index, postmenopausal duration and workload. The US signs of tendinosis may be encountered in a symptom-free population. Calcification and enthesophyte tended to be more frequent in blue-collar workers.

Tendinosis develops from age- and oxygen tension-dependent modulation of Rac1 activity

Age‐related tendon degeneration (tendinosis) is characterized by a phenotypic change in which tenocytes display characteristics of fibrochondrocytes and mineralized fibrochondrocytes. As tendon degeneration has been noted in vivo in areas of decreased tendon vascularity, we hypothesized that hypoxia is responsible for the development of the tendinosis phenotype, and that these effects are more pronounced in aged tenocytes. Hypoxic (1% O₂) culture of aged, tendinotic, and young human tenocytes resulted in a mineralized fibrochondrocyte phenotype in aged tenocytes, and a fibrochondrocyte phenotype in young and tendinotic tenocytes. Investigation of the molecular mechanism responsible for this phenotype change revealed that the fibrochondrocyte phenotype in aged tenocytes occurs with decreased Rac1 activity in response to hypoxia. In young hypoxic tenocytes, however, the fibrochondrocyte phenotype occurs with concomitant decreased Rac1 activity coupled with increased RhoA activity. Using pharmacologic and adenoviral manipulation, we confirmed that these hypoxic effects on the tenocyte phenotype are linked directly to the activity of RhoA/Rac1 GTPase in in vitro human cell culture and tendon explants. These results demonstrate that hypoxia drives tenocyte phenotypic changes, and provide a molecular insight into the development of human tendinosis that occurs with aging.