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Summary 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., Graphical abstract, Highlights Single cell profiling of tendon progenitor cells under mechanical stimulus Seven distinct tendon progenitor subpopulations are identified A subpopulation shows different mechanical response at the single cell level Mitochondria factors TUFM and TFAM downregulated in diseased state under stimulus, Still et al. use single-cell RNA sequencing to profile subpopulations of tendon progenitor cells (TPCs) from normal and diseased patient tendon tissues under mechanical stretching. They identify seven TPC subpopulations and observe different mechanical responses of TPCs at the single-cell level.

Tendinopathy carries a large burden of musculoskeletal disorders seen in both athletes and aging population. Treatment is often challenging, and progression to chronic tendinopathy is common. Physical therapy, nonsteroidal anti-inflammatory drugs, and corticosteroid injections have been the mainstay of treatment but are not optimal given that most tendon disorders seem to involve degenerative changes in addition to inflammation. The field of regenerative medicine has taken the forefront, and various treatments have been developed and explored including prolotherapy, platelet rich plasma, stem cells, and percutaneous ultrasonic tenotomy. However, high-quality research with standardized protocols and consistent controls for proper evaluation of treatment efficacy is currently needed. This will make it possible to provide recommendations on appropriate treatment options for tendinopathy.

Achilles tendon disorders are a common health problem in middle-aged active people. With increasing sport activities in the general population, the number of overuse injuries has increased. Tendon disorders comprise 30–50% of all sports-related injuries. To evaluate the Injuries of Achilles tendon by ultrasonography and magnetic resonance imaging MRI. A cross sectional study was conducted including 20 patients complaining from distal leg pain with history of trauma to lower leg in Achilles tendon to be evaluated by ultrasonography and further evaluation by magnetic resonance imaging. The duration of the study was from 6 to 12 months. The mean age of cases was 41.80±10.7 with range of (20-50) years, 50% was in age group of (41-50) and percent of females was 45% and males was 55%. Ultrasonography is an initial imaging of choice for evaluation of symptomatic Achilles tendon disorders. Diagnostic sensitivity reaches 91.1%. However, Tendons that appeared normal by US should be followed by MRI for more diagnostic accuracy, detailed regional evaluation and subsequently can exclude other etiologies giving similar clinical manifestations.

Tendon-related disorders are common musculoskeletal system disorders in clinical practice, accounting for 30-50% of all sports-related injuries, and they are difficult to treat due to the hypovascular structure of the tendons. Platelet-rich plasma (PRP), including pure PRP and leukocyte- and platelet-rich plasma (L-PRP), has been attracting increasing attention, as it may stimulate tissue regeneration through the release of growth factors and cytokines. The aim of the present review was to provide a summary of the effects of L-PRP on tendon disorders and the underlying mechanisms through a comprehensive examination of the published literature, including in vitro, animal and clinical studies. It has been demonstrated that L-PRP results in comparatively greater pain relief and improved function in patients suffering from tendon disorders. Furthermore, L-PRP may exert its effects through a diverse range of mechanisms, such as neovascularization, cell proliferation and differentiation of tendon/progenitor stem cells into tenocytes, as well as extracellular matrix reorganization by transforming type III to type I collagen fibers. It has also been indicated that the effects of leukocytes in L-PRP depend on the biological state of the injured tissue and its surrounding microenvironment. L-PRP is beneficial and promotes tendon healing at the early stage, whereas it is likely detrimental to the repair of tendon at a later stage because of the risk of excessive catabolic and inflammatory responses. Overall, the application of L-PRP in tendon disorders appears to be a promising field that is worthy of further research.

Tendon injuries are one of the most common musculoskeletal disorders that cause considerable morbidity and significantly compromise the patients' quality of life. The innate limited regenerative capacity of tendon poses a substantial treating challenge for clinicians. MicroRNAs (miRNAs) are a family of small non-coding RNAs that play a vital role in orchestrating many biological processes through post-transcriptional regulation. Increasing evidence reveals that miRNA-based therapeutics may serve as an innovative strategy for the treatment of tendon pathologies. In this review, we briefly present miRNA biogenesis, the role of miRNAs in tendon cell biology and their involvement in tendon injuries, followed by a summary of current miRNA-based approaches in tendon tissue engineering with a special focus on attenuating post-injury fibrosis. Next, we discuss the advantages of miRNA-functionalized scaffolds in achieving sustained and localized miRNA administration to minimize off-target effects, and thus hoping to inspire the development of effective miRNA delivery platforms specifically for tendon tissue engineering. We envision that advancement in miRNA-based therapeutics will herald a new era of tendon tissue engineering and pave a way for clinical translation for the treatments of tendon disorders.

Tendons are vital to joint movement by connecting muscles to bones. Along with an increasing incidence of tendon injuries, tendon disorders can burden the quality of life of patients or the career of athletes. Current treatments involve surgical reconstruction and conservative therapy. Especially in the elderly population, tendon recovery requires lengthy periods and it may result in unsatisfactory outcome. Cell-mediated tendon engineering is a rapidly progressing experimental and pre-clinical field, which holds great potential for an alternative approach to established medical treatments. The selection of an appropriate cell source is critical and remains under investigation. Dermal fibroblasts exhibit multiple similarities to tendon cells, suggesting they may be a promising cell source for tendon engineering. Hence, the purpose of this review article was in brief, to compare tendon to dermis tissues, and summarize in vitro studies on tenogenic differentiation of dermal fibroblasts. Furthermore, analysis of an open source Gene Expression Omnibus (GEO) data repository was carried out, revealing great overlap in the molecular profiles of both cell types. Lastly, a summary of in vivo studies employing dermal fibroblasts in tendon repair as well as pilot clinical studies in this area is included. Altogether, dermal fibroblasts hold therapeutic potential and are attractive cells for rebuilding injured tendons.

Purpose: Although several studies with animals have reported the effects of mesenchymal stem cells (MSCs) for tendon regeneration, little is known about the efficacy and safety of MSCs in human tendon disorders. We performed this meta-analysis to evaluate the efficacy and safety of MSC therapy in patients with tendon disorders enrolled in prospective clinical studies.Methods: We systematically searched prospective clinical studies investigating the effects of MSCs administration on human tendon disorders with at least a 6-month follow-up period on PubMed-Medline, Embase, and Cochrane Library databases. The primary outcome of interest was the change in pain on motion related to tendon disorders. We performed a pairwise meta-analysis using the fixed-effects model to assess treatment response, which was calculated by the standardized mean difference. Meta-regression analyses were performed to assess the relationship between MSCs dose and pooled effect sizes in each cell dose.Results: Four prospective clinical trials investigating the effect of MSCs on tendon disorders were retrieved. MSCs showed significant pooled effect size (overall Hedge’s g pooled standardized mean difference (SMD) = 1.868; 95% confidence interval [CI], 1.274–2.462; P < 0.001). The treatment with MSCs improved all the aspects analyzed, i.e. pain, functional scores, radiologic parameters (magnetic resonance image or ultrasonography), and arthroscopic findings. In the meta-regression analysis, there was a significant cell dose-dependent response in pain relief (Q = 9.06, P = 0.029). While three studies reported mild adverse events after MSCs injection, these were not severe and relieved spontaneously.Conclusions: Our meta-analysis revealed that MSC therapy may improve pain, function, radiologic, and arthroscopic parameters in patients with tendon disorders. Due to the small number of studies in this meta-analysis and considering the increasing MSCs applications, there is a strong need for large-scale randomized controlled trials to confirm the long-term functional improvement as well as the adverse effects of MSC therapies in tendon disorders.

Human amniotic membrane and amniotic membrane-derived mesenchymal stromal cells (hAMSCs) have produced promising results in regenerative medicine, especially for the treatment of inflammatory-based diseases and for different injuries including those in the orthopedic field such as tendon disorders. hAMSCs have been proposed to exert their anti-inflammatory and healing potential via secreted factors, both free and conveyed within extracellular vesicles (EVs). In particular, EV miRNAs are considered privileged players due to their impact on target cells and tissues, and their future use as therapeutic molecules is being intensely investigated. In this view, EV-miRNA quantification in either research or future clinical products has emerged as a crucial paradigm, although, to date, largely unsolved due to lack of reliable reference genes (RGs). In this study, a panel of thirteen putative miRNA RGs (let-7a-5p, miR-16-5p, miR-22-5p, miR-23a-3p, miR-26a-5p, miR-29a-5p, miR-101-3p, miR-103a-3p, miR-221-3p, miR-423-5p, miR-425-5p, miR-660-5p and U6 snRNA) that were identified in different EV types was assessed in hAMSC-EVs. A validated experimental pipeline was followed, sifting the output of four largely accepted algorithms for RG prediction (geNorm, NormFinder, BestKeeper and &Delta, Ct method). Out of nine RGs constitutively expressed across all EV isolates, miR-101-3p and miR-22-5p resulted in the most stable RGs, whereas miR-423-5p and U6 snRNA performed poorly. miR-22-5p was also previously reported to be a reliable RG in adipose-derived MSC-EVs, suggesting its suitability across samples isolated from different MSC types. Further, to shed light on the impact of incorrect RG choice, the level of five tendon-related miRNAs (miR-29a-3p, miR-135a-5p, miR-146a-5p, miR-337-3p, let-7d-5p) was compared among hAMSC-EVs isolates. The use of miR-423-5p and U6 snRNA did not allow a correct quantification of miRNA incorporation in EVs, leading to less accurate fingerprinting and, if used for potency prediction, misleading indication of the most appropriate clinical batch. These results emphasize the crucial importance of RG choice for EV-miRNAs in hAMSCs studies and contribute to the identification of reliable RGs such as miR-101-3p and miR-22-5p to be validated in other MSC-EVs related fields.

Background:Stem cell therapy is an emerging treatment for tendon disorders.Purpose:To systematically review the efficacy of stem cell therapy for patients with tendon disorders.Study Design:Systematic review; Level of evidence, 4.Methods:MEDLINE/PubMed, EMBASE, CINAHL, CENTRAL, PEDro, and SPORTDiscus; trial registers; and gray literature were searched to identify randomized controlled trials (RCTs) and non-RCTs, cohort studies, and case series with 5 or more cases. Studies investigating any type of stem cell therapy for patients with tendon disorders were eligible if they included patient-reported outcome measures or assessed tendon healing. Risk of bias was assessed through use of the Cochrane risk of bias tools.Results:This review included 8 trials (289 patients). All trials had moderate to high risk of bias (level 3 or 4 evidence). In Achilles tendon disorders, 1 trial found that allogenic-derived stem cells led to a faster recovery compared with platelet-rich plasma. Another study found no retears after bone marrow–derived stem cell therapy was used in addition to surgical treatment. There were 4 trials that studied the efficacy of bone marrow–derived stem cell therapy for rotator cuff tears. The controlled trials reported superior patient-reported outcomes and better tendon healing. A further 2 case series found that stem cell therapy improved patient-reported outcomes in patients with patellar tendinopathy and elbow tendinopathy.Conclusion:Level 3 evidence is available to support the efficacy of stem cell therapy for tendon disorders. The findings of available studies are at considerable risk of bias, and evidence-based recommendations for the use of stem cell therapy for tendon disorders in clinical practice cannot be made at this time. Stem cell injections should not be used in clinical practice given the lack of knowledge about potentially serious adverse effects.

Peroneal tendon tears are a common but under-recognized source of ankle pain and dysfunction. Recognition of the characteristic symptoms, physical findings, and imaging results of peroneal tendon tears is essential for accurate diagnosis and appropriate treatment. Acute, limited tears of a single peroneal tendon may be debrided and repaired. However, by the time operative treatment is undertaken, many tears of a single tendon are sufficiently advanced that the surgeon may need to consider excision of the nonviable segment and tenodesis of the damged tendon to the to the adjacent peroneal tendon. Irreparable tearing of both peroneal tendons may be treated with flexor tendon transfer and/or allograft reconstruction. This review article focuses on diagnosis and operative treatment of peroneal tendon tears, including the treatment algorithms, operative technique, and published outcomes.

Tearing of the rotator cuff commonly occurs as among one of the most frequently experienced tendon disorders. While treatment typically involves surgical repair, failure rates to achieve or sustain healing range from 20 to 90%. The insufficient capacity to recover damaged tendon to heal to the bone, especially at the enthesis, is primarily responsible for the failure rates reported. Various types of biomaterials with special structures have been developed to improve tendon-bone healing and tendon regeneration, and have received considerable attention for replacement, reconstruction, or reinforcement of tendon defects. In this review, we first give a brief introduction of the anatomy of the rotator cuff and then discuss various design strategies to augment rotator cuff repair. Furthermore, we highlight current biomaterials used for repair and their clinical applications as well as the limitations in the literature. We conclude this article with challenges and future directions in designing more advanced biomaterials for augmentation of rotator cuff repair.

Tendon disorders are common, affect people of all ages, and are often debilitating. Standard treatments, such as anti-inflammatory drugs, rehabilitation, and surgical repair, often fail. In order to define tendon function and demonstrate efficacy of new treatments, the mechanical properties of tendons from animal models must be accurately determined. Murine animal models are now widely used to study tendon disorders and evaluate novel treatments for tendinopathies; however, determining the mechanical properties of mouse tendons has been challenging. In this study, a new system was developed for tendon mechanical testing that includes 3D-printed fixtures that exactly match the anatomies of the humerus and calcaneus to mechanically test supraspinatus tendons and Achilles tendons, respectively. These fixtures were developed using 3D reconstructions of native bone anatomy, solid modeling, and additive manufacturing. The new approach eliminated artifactual gripping failures (e.g., failure at the growth plate failure rather than in the tendon), decreased overall testing time, and increased reproducibility. Furthermore, this new method is readily adaptable for testing other murine tendons and tendons from other animals.

Tendinopathies are very common in general population and a huge number of tendon-related procedures take place annually worldwide, with significant socio-economic repercussions. Numerous treatment options are commonly used for tendon disorders. Besides pharmacological and physical therapy, nutrition could represent an additional tool for preventing and treating this complex pathology that deserve a multidisciplinary approach. In recent years, nutraceutical products are growing up in popularity since these seem to favor the prevention and the healing processes of tendon injuries. This narrative literature review aims to summarize current understanding and the areas of ongoing research about the management of tendinopathies with the help of oral supplementation.

Resumo Objetivo Relacionar os transtornos traumáticos cumulativos autorreferidos por trabalhadores portuários e seus condicionantes socioambientais. Métodos Estudo transversal com 232 portuários (136 em terra e 96 a bordo) com média de idade de 48,7 anos. Os transtornos traumáticos cumulativos foram autorreferidos; a intensidade foi medida pela atribuição de uma nota de 1 a 4. Foi realizada análise do coeficiente de Spearman para relacionar intensidade dos transtornos e variáveis de caracterização, e teste qui quadrado de Pearson foi usado para relacionar grupos de trabalhadores aos transtornos. Resultados Ambas as categorias de portuários destacaram lombocitalgias (36,8% em terra e 28,1% a bordo) e tendinite (27,9% em terra e 31,3% a bordo de navio). Houve correlação estatística entre a idade e tempo de trabalho com a intensidade dos adoecimentos. Conclusão A autorreferência de adoecimentos ressaltou doenças lombares e tendinosas que inferiram causalidade às doenças autorreferidas, cuja clínica deve integrar o processamento do raciocínio clínico da enfermagem. Abstract Objective To associate cumulative post-traumatic disorders self-reported by port workers with their socio-environmental constraints. Methods Cross-sectional study conducted with 232 port workers (136 onshore and 96 on board) with a mean age of 48.7 years. The cumulative post-traumatic disorders were self-reported, and their intensity was measured by a grade from one to four. Spearman’s correlation coefficient was used to associate the intensity of disorders with characterization variables, and Pearson’s chi-square test was used to associate groups of workers with the disorders. Results Both categories of port workers pointed out lumboischialgia (36.8% onshore and 28.1% on board) and tendinitis (27.9% onshore and 31.3% on board). There was a statistical correlation between age and work time with the intensity of the illnesses. Conclusion The self-reporting of illnesses pointed out low back pain and tendon disorders that inferred causality to the self-reported diseases, whose practice should integrate the processing of the nursing clinical reasoning.

Plantar fasciitis is the most common cause of chronic heel pain in adults, affecting both young active patients and older sedentary individuals. It results from repetitive stress to the plantar fascia at its origin on the medial tubercle of the calcaneus and is often associated with gastrocnemius tightness. The diagnosis can be made clinically with a focused history and physical examination; imaging is reserved for atypical presentations and those that do not respond to initial treatment. The most common presenting symptom is aching plantar heel pain, which is worst with first step in the morning or after periods of rest. Diagnosis is confirmed with point tenderness at the origin of the plantar fascia on the medial tubercle of the calcaneus. Initial treatment consists of activity modification, anti-inflammatory medication, gastrocnemius and plantar fascia stretching, and an in-shoe orthosis that lifts and cushions the heel. These nonoperative treatments lead to complete resolution of pain in 90% of patients but can take 3-6 months. Patients who remain symptomatic despite a 6-month trial of nonoperative therapy may be considered for minimally invasive treatment or surgery. Platelet-rich plasma injections and therapeutic ultrasound are among a number of minimally invasive treatments that stimulate the body’s healing response. Corticosteroid injections temporarily relieve pain, but may increase the risk of plantar fascia rupture and fat pad atrophy. Botulinum toxin injections relax the calf muscles, which decreases the stress in the plantar fascia. Operative treatments include gastrocnemius recession and medial head of gastrocnemius release, which decrease the stress on the plantar fascia and partial planter fasciotomy, which stimulates a healing response. Level of Evidence: Level V, expert opinion.

The role of arthroscopy in the management of ankle and hindfoot pathology management has increased greatly in recent years with the potential for lower complication rates, faster recovery, improved access, and improved outcomes when compared to open techniques. Procedural variations exist as techniques aim to optimize lesion access, decrease operative time, and improve patient safety. Our goal is to summarize the described approaches and patient positionings common in minimally invasive arthroscopic surgery for anterior, lateral, and posterior ankle pathologies. A survey of pathology organized by arthroscopic approach and a review of recent advances in concomitant lesion management may be useful when planning arthroscopic foot and ankle surgery.Level of Evidence:Level V, expert opinion.

Background: Inversion ankle injuries are extremely common, sometimes causing injury to the peroneus brevis tendon. If more than 50% of the tendon is injured, it oftentimes requires tenodesis to the adjacent peroneus longus tendon. Both Pulvertaft (PT) and side-to-side (SS) techniques have been used for joining the 2 tendons. The purpose of this study was to compare the strength and stiffness of these 2 techniques. Methods: Five matched pairs of cadaver ankle specimens were randomized to receive either an SS or PT tenodesis of the peroneus brevis to longus tendons. Following the tenodesis, the specimens were tested for failure load, displacement, energy absorbed at failure, and peak load. Stiffness was also calculated. Paired t tests were performed to detect differences between the 2 conditions. Results: There were no statistically significant differences between the SS and PT tenodesis for any of the metrics measured. For stiffness, the techniques were very similar (SS = 10.14 [4.35], PT = 12.85 [1.72]). Conclusion: There is no difference in failure load, displacement, energy absorbed at failure, peak load or stiffness between the PT and SS techniques for peroneal tenodesis. Level of Evidence: Level V, cadaver study.

Tendon disorders are associated with increased morbidity and a reduction in the quality of life, especially in people of working age. Recently, a new approach, cell-based therapy, offers promising potential to treat tendon injuries. Mesenchymal stem cells are the most suitable candidates for such therapies due to their capacity to differentiate into cells of mesodermal origin, their paracrine properties and their potential use in autologous transplantation. This review summarizes experimental as well as clinical data focusing on the use of mesenchymal stem cells to treat tendinophaties.

Background. Earlier studies have reported positive results from eccentric training in patients with tendon disorders. The reasons for the beneficial clinical effects of eccentric training are not known. Vascularization followed by regression of the vasculature enhances the healing response of injured tendons. Eccentric exercise induces a more beneficial healing response than concentric exercise. Methods. Sixty rats with patellar tendon injuries were divided into three groups: nonexercise controls (group N; n = 20); concentric exercise group (group C; n = 20); eccentric exercise group (group E; n = 20). Each rat was taught to run uphill or downhill for 14 days. Patellar tendons were removed 1, 4, 7, 10, and 14 days following injury. Vascular endothelial growth factor (VEGF), angiopoietin-1, and angiopoietin-2 were measured by reverse transcription polymerase chain reaction. Results. In group C, VEGF mRNA was increased 1 and 4 days following injury but was decreased on days 7, 10, and 14. In group E, VEGF mRNA was elevated only on day 1. In group N, VEGF mRNA remained at a low level throughout all 14 days. The angiopoietin-2/angiopoietin- 1 ratio was higher for group C than for group E. Conclusions. In the presence of VEGF, angiopoietin-1 promotes vessel stability, whereas angiopoietin-2 has the opposite effect. Eccentric exercise contributes to stabilized angiogenesis during the early phase of tendon injury. Conversely, concentric exercise, which induces destabilized angiogenesis, leads to a delayed healing response. Initiation of eccentric exercise immediately after tendon injury may help improve healing by reducing vascularity. © 2008 The Japanese Orthopaedic Association.

The idea for this special number of Journal of Ultrasound arose from the Editor in chief of the journal, Ferdinando Draghi, and myself as a result of our longstanding friendship and previous publication in 2012 of a monothematic musculoskeletal number written by Italian authors and French speaking authors of the SIMS (Societe Imagerie Musculosqueletique). We choose the ankle and foot region since, because of the superficial position of most of their structures, it can be optimally explored by ultrasound (US). All the tendons, most of the nerves and vessels of this region can be accurately assessed, statically and dynamically, when using a high-definition modern US equipment by a well-trained examiner. Essential prerequisites for successful assessment include in depth knowledge of the normal anatomy and variations, realization of the US examination based on clinical findings and knowledge of intrinsic limits of US. The first article describes the sonographic anatomy of the ankle. Following articles deal with US appearance of a wide variety of pathologic conditions including ankle impingement syndrome, mid-portion Achilles tendon injury, tibialis anterior muscle and tendon disorders, peroneal tendon tear and, finally, evaluation of hindfoot disorders. All the articles have been written by well-renowned sonologits including not only radiologists but also clinicians (orthopedic surgeons and family medicine doctors). Authors are from Europe (Italy, France and England) and also from North America (USA and Canada) thus reflecting the widespread diffusion of Journal of Ultrasound. The articles were written with an effort to help the readers in their every day US practice. We hope you will appreciate our effort during scanning your next ankle and foot region! Have a good lecture.

The knowledge about tendons and tenocyte biological behaviour during aging and, especially, oestrogen deficiency is limited. Women differ from men with regard to muscle and tendon, most likely due to differences in sex hormones activity and tissue response. To-date the interest in metabolic factors that may induce tendon disorders is growing. The aim of this paper is to elucidate the current findings in the correlation between oestrogen deficiency, aging and tendon pathology and to encourage future researches to ameliorate assessment and management of tendinopathies in postmenopausal women.

Background: Tendon disorders are among the most common musculoskeletal conditions in active patients. Platelet rich plasma (PRP) has been used in the treatment of tendon disorders, but little is known as to the mechanisms by which PRP acts. PRP contains numerous different growth factors and cytokines which activate various cellular signaling cascades, but it has been difficult to determine precisely which signaling pathways and cellular responses are activated following PRP treatment. Additionally, macrophages are important in modulating tendon regeneration, but the influence of PRP on determining whether macrophages assume a proinflammatory or antiinflammatory phenotype remains unknown. Our objectives were to use genome wide expression profiling, bioinformatics and protein analysis to determine the cellular pathways activated in fibroblasts treated with PRP, and to also evaluate the effect of PRP on macrophage polarization. Methods: Tendon fibroblasts or macrophages from rats were cultured and treated with either platelet poor plasma (PPP) or PRP. RNA or protein was isolated from cells and analyzed using microarrays, qPCR, immunoblot or bioinformatics techniques. Results: Bioinformatics analysis determined that the two signaling pathways predicted to be activated by PRP were the TNFα and NFκB pathways. PRP also downregulated several ECM genes, and induced the expression of autophagy related genes and reactive oxygen species (ROS) genes, as well as markers of protein oxidation in tendon fibroblasts. PRP failed to have a major impact on markers of macrophage polarization. Conclusions: PRP induces an inflammatory response in tendon fibroblasts which leads to the formation of ROS and activation of oxidative stress pathways. PRP does not appear to significantly modulate macrophage polarization. Clinical Relevance: PRP might act by inducing a transient inflammatory event which could then trigger a tissue regeneration response.

Rupture of tendons due to either high load or laceration is a common injury, especially for the hand. Tendon disorders are traditionally treated by reducing inflammation, restoring flexibility, and, if necessary, performing surgical repair. It has been estimated that hand surgeons repair nearly one-third of a million digital flexor tendon injuries per year in the United States. Despite the fact that surgery of tendons is a common procedure, its outcome is often unsatisfactory. Recovery after tendon surgery can take months. At best, the restored tendon is about half of its initial mechanical properties, so surgeons often face patients’ dissatisfaction. On the other hand, if left untreated, healing tendon is not as good as original structure from a mechanical point of view. Moreover, the related pain is difficult to treat. Several factors may explain these unsatisfactory results such as the difficulty to anchorage the tendon in muscle, the high mechanical constraint on the repair structure, or the unavailability of ideal tendon grafts (currently, tendon grafts are either auto, allo, or synthetic). It has been shown that early mobilization following tendon surgery gives superior results. The repaired tendon should then be able to support immediate loading. However, suturing techniques to joint split ends of tendons, while providing sufficient mechanical strength to limit gapping, are inadequate to carry normal loads. Based on the shortcomings of the actual tendon surgery, tendon tissue engineering may offer an alternative approach. The objective in developing an engineered tendon will then be the reconstruction of the injured structure with structural and functional properties as good as the original. Moreover, an engineered tendon could reduce the rate of secondary problems by making the surgical procedure less extensive. This article gives first some general details on anatomy and physiological properties of tendons, followed by a list of requirements for an ideal engineered tendon. A review of the actual state of the art in tendon replacement is then performed, and finally, some remarks on the future of tissue engineering of tendons are proposed.

Primary disorders of tendons are common and constitute a high proportion of referrals to rheumatologists. Certain tendons are particularly vulnerable to degenerative pathology; these include the Achilles, patella, elements of the rotator cuff, forearm extensors, biceps brachi and tibialis posterior tendons. Disorders of these tendons are often chronic and can be difficult to manage successfully in the long term. Significant advances have been made in understanding the pathophysiology of these conditions. Histopathological evidence, together with advances in imaging techniques, has made us more appreciative of the degenerative (rather that inflammatory) nature of these conditions. Additionally the presence of neovascularization is now well-recognized in long-standing tendinopathy. We review the mechanical, vascular and developing neural theories that attempt to explain the aetiology of degenerative tendinopathy. We also explore theories of why specific tendons (such as the Achilles and supraspinatus tendons) are particularly prone to degenerative pathology. Traditionally, treatments have placed a heavy emphasis on anti-inflammatory strategies, which are often inappropriate. Recently, however, significant advances in the practical management of tendon disorders have been made. In particular the advent of 'eccentric loading' training programmes has revolutionized the treatment of Achilles tendinopathy in some patients. This concept is currently being extended to include other commonly injured tendons. Other current treatments are reviewed, as are potential future treatments.

Distal biceps tendon rupture is a rare injury. While plain radiographs are usually not helpful in visualizing the defect, evaluation of the tendon with MRI has proven to be useful as it depicts complete anatomic detail of the tendon and associated structures. Its multiplanar imaging capability and superior soft tissue contrast resolution makes MRI a prime diagnostic tool in the diagnosis of tendon disorders. We report a case of complete rupture of the biceps tendon diagnosed by MRI.