A comprehensive guide to western blotting for tendon research

Tendons are classified as dense fibrous connective tissue. This fibrous composition poses challenges in protein extraction, particularly hindering the application of Western blotting techniques. Because of these challenges, it becomes necessary to implement additional steps and specific solutions to attain success in this methodology with the tissue in question. The objective of this article is to provide a detailed protocol, elucidating each step, and making it easily replicable for researchers. The study focused on the Achilles tendons of Sprague-Dawley rats, emphasizing the need for a tailored approach in working with this tissue. By addressing the nuances of protein extraction from the dense and fibrous tendons, our protocol aims to facilitate the reproducibility of Western blotting experiments, contributing to a better understanding of this tissue.

The Outcome of the WALANT Technique in Primary Hand Flexor Tendons Repair

Introduction

Wide-awake local anesthesia and no tourniquet (WALANT) represents a revolutionary technique for hand surgeons who dismiss tourniquets and sedation. In this study, we present our experience with the WALANT technique in primary flexor tendon injuries of the hand.

Patient and methods

This prospective research was carried out on 30 patients undergoing hand primary, flexor tendon repair surgery. Flexor tendon injury zones 2, 3, 4, and 5 were included. WALANT was prepared and injected. The tendons were surgically managed by a cruciate single cross-stitched locked 4-strand technique. The pain was assessed using a visual analog scale (VAS) score. The range of motion (ROM) of affected fingers was assessed according to the Strickland evaluation system.

Results

There was a highly significant relationship between the patient's compliance with physiotherapy and obtained ROM of the affected finger with a P value <0.001. During injection of WALANT solution, 4 cases (13.3%) had no pain, 25 cases (83.3%) had mild pain (score 1-4), and 1 case (3.3%) had moderate pain (score 5-7).

Conclusion

WALANT provides an optimal bloodless and comfortable field with an opportunity to assess the strength of tendon repair, gapping or triggering and managing them intra-operatively.

Visualization of rat tendon in three dimensions using micro-Computed Tomography

Micro-computed tomography (CT) is an X-ray-based imaging modality that produces three-dimensional (3D), high-resolution images of whole-mount tissues, but is typically limited to dense tissues, such as bone. The X-rays readily pass-through tendons, rendering them transparent. Contrast-enhancing chemical stains have been explored, but their use to improve contrast in different tendon types and across developmental stages for micro-CT imaging has not been systematically evaluated. Therefore, we investigated how phosphotungstic acid (PTA) staining and tissue hydration impacts tendon contrast for micro-CT imaging. We showed that PTA staining increased X-ray absorption of tendon to enhance tissue contrast and obtain 3D micro-CT images of immature (postnatal day 21) and sexually mature (postnatal day 50) rat tendons within the tail and hindlimb. Further, we demonstrated that tissue hydration state following PTA staining significantly impacts soft tissue contrast. Using this method, we also found that tail tendon fascicles appear to cross between fascicle bundles. Ultimately, contrast-enhanced 3D micro-CT imaging will lead to better understanding of tendon structure, and relationships between the bone and soft tissues.•Simple tissue fixation and staining technique enhances soft tissue contrast for tendon visualization using micro-CT.•3D tendon visualization in situ advances understanding of musculoskeletal tissue structure and organization.

Development and growth of the temporal fascia: a histological study using human fetuses

The temporal fascia is a double lamina sandwiching a thick fat layer above the zygomatic bony arch. To characterize each lamina, their developmental processes were examined in fetuses. We observed histological sections from 22 half-heads of 10 mid-term fetuses at 14-18 weeks (crown-rump length, 95-150 mm) and 12 near-term fetuses at 26-40 weeks (crown-rump length, 215-334 mm). The superficial lamina of the temporal fascia was not evident at mid-term. Instead, a loose subcutaneous tissue was attached to the thin, deep lamina of the temporal fascia covering the temporalis muscle. At near-term, the deep lamina became thick, while the superficial lamina appeared and exhibited several variations: i) a mono-layered thick membrane (5 specimens); ii) a multi-layered membranous structure (6) and; iii) a cluster of independent thick fasciae each of which were separated by fatty tissues (1). In the second and third patterns, fatty tissue between the two laminae was likely to contain longitudinal fibrous bands in parallel with the deep lamina. Varying proportions of the multi-layered superficial lamina were not attached to the zygomatic arch, but extended below the bony arch. Whether or not lobulation or septation of fatty tissues was evident was not dependent on age. The deep lamina seemed to develop from the temporalis muscle depending on the muscle contraction. In contrast, the superficial lamina developed from subcutaneous collagenous bundles continuous to the cheek. Therein, a difference in development was clearly seen between two categories of the fasciae.

Usefulness of sulfonated azo dyes to evaluate macromolecularly oriented protein substrates

Sulfonated azo dyes are crucial for the histochemical, topochemical, and electrophoretic demonstration of proteins. Additionally, these dyes may reveal the significance of evaluating the anisotropic phenomenon of linear dichroism in macromolecularly oriented stained proteins. However, this requires that the ordered -NH3+ groups available for electrostatic binding of the -SO3- dye groups are present in the protein substrate. Further, the reactive -SO3- dye groups should be positioned in a way to permit selective absorption of polarized light at the level of the dye -NN- chromophore azo groups. This review reports the usefulness of sulfonated azo dyes in revealing the extrinsic phenomenon of linear dichroism in dye-substrate complexes and changes in the oriented state of protein macromolecules.

Regional shear wave speeds track regional axial stress in nonuniformly loaded fibrous soft tissues

Ligaments and tendons undergo nonuniform deformation during movement. While deformations can be imaged, it remains challenging to use such information to infer regional tissue loading. Shear wave tensiometry is a promising noninvasive technique to gauge axial stress and is premised on a tensioned beam model. However, it is unknown whether tensiometry can predict regional stress in a nonuniformly loaded structure. The objectives of this study were to (1) determine whether regional shear wave speed tracks regional axial stress in nonuniformly loaded fibrous soft tissues, and (2) determine the sensitivity of regional axial stress and shear wave speed to nonuniform load distribution and fiber alignment. We created a representative set of 12,000 dynamic finite element models of a fibrous soft tissue with probabilistic variations in fiber alignment, stiffness, and aspect ratio. In each model, we applied a randomly selected nonuniform load distribution, and then excited a shear wave and tracked its regional propagation. We found that regional shear wave speed was an excellent predictor of the regional axial stress (RMSE = 0.57 MPa) and that the nature of the regional shear wave speed-stress relationship was consistent with a tensioned beam model (R2 = 0.99). Variations in nonuniform load distribution and fiber alignment did not substantially alter the wave speed-stress relationship, particularly at higher loads. Thus, these findings suggests that shear wave tensiometry could provide a quantitative estimate of regional tissue stress in ligaments and tendons.

Extracellular vesicles are key players in mesenchymal stem cells' dual potential to regenerate and modulate the immune system

MSCs are used for treatment of inflammatory conditions or for regenerative purposes. MSCs are complete cells and allogenic transplantation is in principle possible, but mostly autologous use is preferred. In recent years, it was discovered that cells secrete extracellular vesicles. These are active budded off vesicles that carry a cargo. The cargo can be miRNA, protein, lipids etc. The extracellular vesicles can be transported through the body and fuse with target cells. Thereby, they influence the phenotype and modulate the disease. The extracellular vesicles have, like the MSCs, immunomodulatory or regenerative capacities. This review will focus on those features of extracellular vesicles and discuss their dual role. Besides the immunomodulation, the regeneration will concentrate on bone, cartilage, tendon, vessels and nerves. Current clinical trials with extracellular vesicles for immunomodulation and regeneration that started in the last five years are highlighted as well. In summary, extracellular vesicles have a great potential as disease modulating entity and treatment. Their dual characteristics need to be taken into account and often are both important for having the best effect.

Treatment of a fractured humerus and partially torn supraspinatus tendon in a professional boxer with liquid platelet-rich fibrin and heat-coagulated albumin gel: a case report

INTRODUCTION

Fractures with delayed healing can be a serious complication, especially for athletes depending on quick return to sports. To our knowledge, no cases of increased healing of delayed union fractures with autologous biomedical interventions have been reported.

CASE PRESENTATION

A 33-year-old Swedish professional boxer with a fractured humerus with a delayed union and a partially torn supraspinatus tendon was treated with injections of liquid platelet-rich fibrin and heat-coagulated albumin gel. He recovered almost completely from both injuries in only 1 month and could return to professional boxing in 3 months.

CONCLUSION

This case raises the hypothesis that liquid platelet-rich fibrin and heat-coagulated albumin gel may be an effective, minimally invasive intervention in fractures with a delayed union. Further research is required to test this theory.

Contribution of Soft Tissue Passive Forces in Thumb Carpometacarpal Joint Distraction

Thumb carpometacarpal joint space changes when the surrounding soft tissues including the capsule, ligaments, and tendons are stretched or pulled away. When at rest, joint forces originate from passive contraction of muscles and the involvement of joint capsule and ligaments. Previous biomechanical models of hand and finger joints have mostly focused on the assessment of joint properties when muscles were active. This study aims to present an experimental-numerical biomechanical model of thumb carpometacarpal joint to explore the contribution of tendons, ligaments, and other soft tissues in the passive forces during distraction. Five fresh cadaveric specimens were tested using a distractor device to measure the applied forces upon gradual distraction of the intact joint. The subsequent step involved inserting a minuscule sensor into the joint capsule through a small incision, while preserving the integrity of tendons and ligaments, in order to accurately measure the fundamental intra-articular forces. A numerical model was also used to calculate the passive forces of tendons and ligaments. Before the separation of bones, the forces exerted by tendons and ligaments were relatively small compared to the capsule force, which accounted for approximately 92% of the total applied force. Contribution of tendons and ligaments, however, increased by further distraction. The passive force contribution by tendons at 2-mm distraction was determined less than 11%, whereas it reached up to 74% for the ligaments. The present study demonstrated that the ligament-capsule complex plays significant contribution in passive forces of thumb carpometacarpal joint during distraction.

Peracetic acid sterilized tendon and ligament allografts for knee reconstruction : For anterior cruciate ligament (ACL), posterior cruciate ligament (PCL) and complex knee surgery

BACKGROUND

The use of allografts and autografts has been met with mixed views on whether allografts are a suitable alternative to autografts.

QUESTION

We aimed to investigate if chemically sterilized allografts show similar rerupture rates to those reported in the literature for allografts and autografts in anterior (ACL) and posterior cruciate ligaments (PCL) and complex knee surgery.

MATERIALS AND METHODS

Retrospective data on knee reconstructions performed between 2011 and 2015 with tendon/ligamnet allografts sterilized with peracetic acid were collected in the form of a questionnaire. The inclusion criteria of 2 years for each patient were met by 38 patients, representing 22 ACL reconstructions, 5 PCL reconstructions, 3 OTHER surgeries, including the Larson technique and medial patellofemoral ligament (MPFL) reconstruction and 8 COMPLEX surgeries. The main endpoints were rerupture and complication rate. Secondary endpoints included stability of the knee (Lachman test, Pivot shift test) and the range of motion.

RESULTS

The rerupture rate was 7.9% (3 grafts). Reruptures only occurred in the ACL group. No reruptures were observed in the PCL, OTHER and COMPLEX surgery groups. Stability improved significantly after surgery and the range of motion returned to values similar to that of healthy knees.

CONCLUSIONS

Tendon allografts sterilized with peracetic acid show promising low rerupture rates and good clinical scores and the results are comparable to the literature on autografts and other allografts.

Neonatal Achilles Tendon Microstructure is Negatively Impacted by Decorin and Biglycan Knockdown After Injury and During Development

Interest in studying neonatal development and the improved healing response observed in neonates is increasing, with the goal of using this work to create better therapeutics for tendon injury. Decorin and biglycan are two small leucine-rich proteoglycans that play important roles in collagen fibrillogenesis to develop, maintain, and repair tendon structure. However, little is known about the roles of decorin and biglycan in early neonatal development and healing. The goal of this study was to determine the effects of decorin and biglycan knockdown on Achilles tendon structure and mechanics during neonatal development and recovery of these properties after injury of the neonatal tendon. We hypothesized that knockdown of decorin and biglycan would disrupt the neonatal tendon developmental process and produce tendons with impaired mechanical and structural properties. We found that knockdown of decorin and biglycan in an inducible, compound decorin/biglycan knockdown model, both during development and after injury, in neonatal mice produced tendons with reduced mechanical properties. Additionally, the collagen fibril microstructure resembled an immature tendon with a large population of small diameter fibrils and an absence of larger diameter fibrils. Overall, this study demonstrates the importance of decorin and biglycan in facilitating tendon growth and maturation during neonatal development.

Contributions of collagen and elastin to elastic behaviours of tendon fascicle

Tendon exhibits the capacity to be stretched and to return to its original length without suffering structural damage in vivo, a capacity known as elastic recoil. Collagen fibres are aligned longitudinally and elastin fibres mostly run parallel to collagen fibres in tendon. However, their interactions and contributions to tendon elastic behaviours are not well understood. The present study examined functional roles of collagen and elastin in tendon elastic behaviours using a variety of mechanical tests. We prepared three types of fascicle specimens from mouse tail tendon: fascicles freshly isolated, those digested with elastase in PBS to selectively remove elastin, and those incubated in PBS without elastase. A quasi-static tensile test demonstrated that elastase-treated fascicles had higher tangent moduli and strength compared to fresh and PBS fascicles. Cyclic stretching tests showed that fresh and PBS fascicles could withstand cyclic strain at both small and large amplitudes, but elastase-treated fascicles could only behave elastically to a limited degree. Fibre-sliding analysis revealed that fresh fascicles could be elongated both through stretching of collagen fibers and through movement of the fibres. However, elastase-treated fascicles could be stretched only via fibre stretching. This evidence suggests that normal tendons can be extended through both fibre stretching and fibre sliding, whereas tendons without elastin can only extend as much as collagen fibers can withstand. Accordingly, collagen fibres mainly contribute to tendon elastic behaviours by furnishing rigidity and elasticity, whereas elastin provides tendon viscoelasticity and also enables sliding of collagen fibres during elastic behaviours. STATEMENT OF SIGNIFICANCE: The present study revealed distinct mechanical functions of collagen and elastin fibres in elastic behaviours of mouse tail tendon fascicle using a variety of mechanical tests at both microscopic and macroscopic levels. It was demonstrated that collagen mainly governs tendon fascicle rigidity and elasticity, but only possesses limited extensibility, whereas elastin contributes to viscoelasticity and collagen fibre sliding, enabling elastic recoil behaviour against relatively large deformation. By their interactions, tendon can be elongated without suffering major structural damage and withstand a large magnitude of tensile force in response to mechanical loading. Such information should be particularly useful in designing collagen-based biomaterials such as artificial tendons, in that previous studies have merely considered collagen without incorporation of elastin.

Midfoot width changes after first metatarsal osteotomy in hallux valgus surgery: A biomechanical effect?

Hallux valgus is a challenging pathology characterized by a valgus deformity in the metatarsophalangeal area of the first ray. The aim of this study was to analyze the influence of first metatarsal osteotomy on the relationship between midfoot bones in patients with hallux valgus. The sample consisted of patients from the orthopedics and traumatology outpatient clinic who underwent surgical treatment for hallux valgus. Preoperative and postoperative X-rays were compared regarding the width of the midfoot and the tarsometatarsal joint. The sample consisted of 17 women, with 22 feet assessed in each group. The distance from the medial cuneiform to the cuboid, the distance from the intermediate cuneiform to the cuboid, the distance between the first and fifth metatarsals, and the distance between the second and fifth metatarsals reduced significantly between pre- and postoperative assessments. Hallux valgus correction through osteotomy of the first metatarsal leads to a structural change in the midfoot. Further studies should determine whether these changes persist over time.

The trend of allogeneic tendon decellularization: literature review

Tendon injuries repair is a significant burden for orthopaedic surgeons. Finding a proper graft material to repair tendon is one of the main challenges in orthopaedics, for which the requirement of substitute for tendon repair would be different for each clinical application. Among biological scaffolds, the use of decellularized tendon increasingly represents an interesting approach to treat tendon injuries and several articles have investigated the approaches of tendon decellularization. To understand the outcomes of the the approaches of tendon decellularization on effect of tendon transplantation, a literature review was performed. This review was conducted by searching in Pubmed and Embase and 64 studies were included in this study. The findings revealed that the common approaches to decellularize tendon include chemical, physical, and enzymatic decellularization methods or their combination. With the development of tissue engineering, researchers also put forward new theories such as automatic acellular machine, 3D printing technology to manufacture acellular scaffold.

High-intensity interval training enhances mRNA expression of IGF1Ea in rat Achilles tendon

High-intensity interval training (HIIT) reportedly enhances the functional properties of the musculoskeletal system. However, the effects of HIIT on tendons remain unclear. Sixteen male rats were randomly assigned to the control (Con) or HIIT group (n = 8 in each group). Rats in the HIIT group executed the HIIT program consisting of 2.5 min treadmill running and 4.5 min rests between the bouts, 5 days per week for 9 weeks. Running speed, number of sets, and inclination were incrementally increased during the training period. Histological analysis revealed no apparent morphological changes in the extracellular matrix structure or nuclei of tenocytes between the groups. Real-time reverse transcription polymerase chain reaction analysis revealed that Igf1Ea mRNA expression was enhanced in the HIIT group. Furthermore, Igfbp5 mRNA expression tended to be higher in the HIIT group. The 9-week HIIT program enhanced tenogenic Igf1Ea mRNA expression.

All-endoscopic approach for distal biceps tendon pathology: Analysis of long-term outcomes in partial and complete ruptures

BACKGROUND

Distal biceps tendon (DBT) pathology is a spectrum that ranges from tendinopathy to complete retracted ruptures, and surgical treatment is usually performed via open approaches. The purpose of this study was to analyze safety and long-term outcomes of all-endoscopic surgery for entire spectrum of primary DBT pathology. The hypothesis was that at an all-endoscopic technique would result in satisfactory clinical outcomes and a low complication rate.

METHODS

Consecutive patients who underwent all-endoscopic surgery for primary isolated DBT pathology (bursitis, partial and acute/chronic complete tears) between January 2013 and December 2021 were assessed and analyzed retrospectively. Refractory bursitis and low-grade partial tears underwent endoscopic débridement, and high-grade partial tears and complete ruptures underwent all-endoscopic repair or graft reconstruction. Preoperative and follow-up assessment included functional assessment using Mayo Elbow Performance Score (MEPS) and a Patient-Reported Distal Biceps Score (PRDBS), and radiological assessment was performed using plain biplanar radiographs and sonography. Pre- and postoperative scores for the overall group, and for partial and complete tears, were compared using a paired T-test.

RESULTS

Overall, 26 male patients underwent an all-endoscopic surgery for distal biceps tendon tears; the pathology was classified by endoscopic findings into 6 types, and follow-up period ranged from 21 to 125 months (mean 79.4 months). Nine chronic partial tears (35%) included predominantly bursitis (type I, n=2) and predominantly partial tears (type IIA and B, n=7). The complete tear group (65%) included isolated short or long head tears (type IIIA and IIIB, n=2) and complete tendon ruptures (types IV, V, and VIA-C, n=15). Endoscopic débridement of the bursitis/ low grade tears and repair of the high-grade and complete ruptures resulted in complete resolution of symptoms and significant improvement in both MEPS and PRDBS (p<0.001). Autografts were necessary in 35% (6/17) of complete tears, and no significant difference was found in functional scores in this group as compared to those where primary repairs were possible. There were 2 minor complications (7.6%) that involved transient lateral antebrachial cutaneous nerve (LACN) neuropraxia. Follow-up sonography and radiographs showed an intact tendon and absence of heterotopic ossification or synostosis.

CONCLUSIONS

An all-endoscopic approach for treating distal biceps tendon pathology was safe and reliable and was associated with significant improvement in subjective and functional outcomes in the long term. The dual-anchor onlay repair technique showed long-term radiologically demonstrable structural integrity of the tendon and was associated with a low minor complication rate and absence of heterotopic ossification.

Equine Embryonic Stem Cell-Derived Tenocytes are Insensitive to a Combination of Inflammatory Cytokines and Have Distinct Molecular Responses Compared to Primary Tenocytes

Tissue fibrosis following tendon injury is a major clinical problem due to the increased risk of re-injury and limited treatment options; however, its mechanism remains unclear. Evidence suggests that insufficient resolution of inflammation contributes to fibrotic healing by disrupting tenocyte activity, with the NF-κB pathway being identified as a potential mediator. Equine embryonic stem cell (ESC) derived tenocytes may offer a potential cell-based therapy to improve tendon regeneration, but how they respond to an inflammatory environment is largely unknown. Our findings reveal for the first time that, unlike adult tenocytes, ESC-tenocytes are unaffected by IFN-γ, TNFα, and IL-1β stimulation; producing minimal changes to tendon-associated gene expression and generating 3-D collagen gel constructs indistinguishable from unstimulated controls. Inflammatory pathway analysis found these inflammatory cytokines failed to activate NF-κB in the ESC-tenocytes. However, NF-κB could be activated to induce changes in gene expression following stimulation with NF-κB pharmaceutical activators. Transcriptomic analysis revealed differences between cytokine and NF-κB signalling components between adult and ESC-tenocytes, which may contribute to the mechanism by which ESC-tenocytes escape inflammatory stimuli. Further investigation of these molecular mechanisms will help guide novel therapies to reduce fibrosis and encourage superior tendon healing.

Pathological calcification in canine tendon-derived cells is modulated by extracellular ATP

Tendon calcification is a commonly associated with degenerative tendinopathy of the Achilles tendons in dogs. It is characterised by the formation of calcific deposits and is refractory to treatment, often re-forming after surgical removal. Little is known about its pathogenesis and therefore the aims of this study were to develop an in vitro model of canine tendon calcification and use this model to investigate mechanisms driving calcification. Cells from the canine Achilles tendon were cultured with different calcifying media to establish which conditions were best able to induce specific, cell-mediated calcification. Once optimum calcification conditions had been established, the effect of ATP treatment on calcification was assessed. Results revealed that 2 mM di-sodium phosphate combined with 2 mM calcium chloride provided the optimum calcifying conditions, increasing calcium deposition and expression of osteogenic-related genes similar to those observed in tendon calcification in vivo. ATP treatment inhibited calcification in a dose-dependent manner, reducing calcium deposition and increasing cell viability, while osteogenic-related genes were no longer upregulated. In conclusion, the in vitro model of canine tendon calcification developed in this study provides the ability to study mechanisms driving tendon calcification, demonstrating that ATP plays a role in modulating tendon calcification that should be explored further in future studies.

A systematic review on sonoelastography for post-repair rotator cuff assessment

Surgical repair of rotator cuff tears is performed routinely; however, the risks of re-tears and the associated consequences are significant. Sonoelastography, an imaging modality that evaluates the mechanical properties of tissues, can examine the dynamic transitions in rotator cuff stiffness following retear and investigate the relationship between these changes and the occurrences of retears. This systematic review aimed to summarize the role of perioperative sonoelastography in repaired rotator cuffs. A comprehensive search of the PubMed, Embase, and Cochrane databases was conducted, covering studies published until June 19, 2023. The Newcastle-Ottawa scale was used for quality assessment. The key information extracted from each study included the injury/surgery type, follow-up duration, sonoelastography mode, and main sonoelastographic findings. Eleven eligible studies comprising 355 patients were included. All studies focused on supraspinatus muscles and tendons with previous arthroscopic repairs. During the postoperative 1st - 6th months, muscle stiffness increased in the supraspinatus and decreased in the ipsilateral deltoid. Failure to recover supraspinatus muscle elasticity might be indicative of potential tendon re-tear; however, it is imperative to first establish correlations with other imaging modalities. Conflicting findings have been observed regarding stiffening or softening of the supraspinatus tendon after surgical repair. The preoperative stiffness of the supraspinatus tendon did not correlate with postoperative tendon integrity or function.

Current practice, guideline adherence, and barriers to implementation for Achilles tendinopathy rehabilitation: a survey of physical therapists and people with Achilles tendinopathy

Objective

To explore clinical practice patterns of physical therapists (PTs) who treat people with Achilles tendinopathy (AT), and identify perceived barriers and facilitators for prescribing and engaging with therapeutic exercise among PTs and people with AT.

Methods

Two cross-sectional surveys were electronically distributed between November 2021 and May 2022; one survey was designed for PTs while the second was for people with AT. Survey respondents answered questions regarding their physical therapy training and current practice (PTs), injury history and management (people with AT), and perceived barriers and facilitators (PTs and people with AT).

Results

341 PTs and 74 people with AT completed the surveys. In alignment with clinical practice guidelines, more than 94% of PTs surveyed (97% of whom had some form of advanced musculoskeletal training) prioritise patient education and therapeutic exercise. Patient compliance, patient knowledge, and the slow nature of recovery were barriers to prescribing therapeutic exercise reported by PTs, while time, physical resources, and a perceived lack of short-term treatment effectiveness were barriers for people with AT.

Conclusions

Consistent with clinical practice guidelines, PTs with advanced training reported prioritising therapeutic exercise and education for managing AT. However, both PTs and people with AT identified many barriers to prescribing or engaging with therapeutic exercise. By addressing misconceptions about the time burden and ineffectiveness of exercise, and by overcoming access issues to exercise space and equipment, PTs may be able to improve intervention adherence and subsequently outcomes for people with AT.

An automated method for tendon image segmentation on ultrasound using grey-level co-occurrence matrix features and hidden Gaussian Markov random fields

BACKGROUND

Despite knowledge of qualitative changes that occur on ultrasound in tendinopathy, there is currently no objective and reliable means to quantify the severity or prognosis of tendinopathy on ultrasound.

OBJECTIVE

The primary objective of this study is to produce a quantitative and automated means of inferring potential structural changes in tendinopathy by developing and implementing an algorithm which performs a texture based segmentation of tendon ultrasound (US) images.

METHOD

A model-based segmentation approach is used which combines Gaussian mixture models, Markov random field theory and grey-level co-occurrence (GLCM) features. The algorithm is trained and tested on 49 longitudinal B-mode ultrasound images of the Achilles tendons which are labelled as tendinopathic (24) or healthy (25). Hyperparameters are tuned, using a training set of 25 images, to optimise a decision tree based classification of the images from texture class proportions. We segment and classify the remaining test images using the decision tree.

RESULTS

Our approach successfully detects a difference in the texture profiles of tendinopathic and healthy tendons, with 22/24 of the test images accurately classified based on a simple texture proportion cut-off threshold. Results for the tendinopathic images are also collated to gain insight into the topology of structural changes that occur with tendinopathy. It is evident that distinct textures, which are predominantly present in tendinopathic tendons, appear most commonly near the transverse boundary of the tendon, though there was a large variability among diseased tendons.

CONCLUSION

The GLCM based segmentation of tendons under ultrasound resulted in distinct segmentations between healthy and tendinopathic tendons and provides a potential tool to objectively quantify damage in tendinopathy.

Cell Sheet Technology: An Emerging Approach for Tendon and Ligament Tissue Engineering

Tendon and ligament injuries account for a substantial proportion of disorders in the musculoskeletal system. While non-operative and operative treatment strategies have advanced, the restoration of native tendon and ligament structures after injury is still challenging due to its innate limited regenerative ability. Cell sheet technology is an innovative tool for tissue fabrication and cell transplantation in regenerative medicine. In this review, we first summarize different harvesting procedures and advantages of cell sheet technology, which preserves intact cell-to-cell connections and extracellular matrix. We then describe the recent progress of cell sheet technology from preclinical studies, focusing on the application of stem cell-derived sheets in treating tendon and ligament injuries, as well as highlighting its effects on mitigating inflammation and promoting tendon/graft-bone interface healing. Finally, we discuss several prerequisites for future clinical translation including the selection of appropriate cell source, optimization of preparation process, establishment of suitable animal model, and the fabrication of vascularized complex tissue. We believe this review could potentially provoke new ideas and drive the development of more functional biomimetic tissues using cell sheet technology to meet the needs of clinical patients.

Characterization of an in vitro engineered ligament model

In vivo tendon and ligament research can be limited by the difficultly of obtaining tissue samples that can be biochemically analyzed. In this study, we characterize the most widely used in vitro engineered ligament model. Despite previous works suggesting multiple passages change gene expression in 2D primary tenocytes, we found no relationship between passage number and expression of classical tendon fibroblast markers across different biological donors. When engineered into 3D ligaments, there was an increase in maximal tensile load between 7 and 14 days in culture, that corresponded with an increase in collagen content. By contrast, percent collagen increased logarithmically from Day 7 to Day 14, and this was similar to the increase in the modulus of the tissue. Importantly, there was no relationship between passage number and mechanical function or collagen content in the two independent donors tested. These results suggest that the model develops quickly and is reliable across differing passage numbers. This provides the field with the ability to 1) consistently determine functional changes of interventions out to passage number 10; and 2) to time interventions to the appropriate developmental stage: developing/regenerating (Day 7) or mature (Day 14) tissue.

Biology and physiology of tendon healing

Tendon disorders affect people of all ages, from elite and recreational athletes and workers to elderly patients. After an acute injury, 3 successive phases are described to achieve healing: an inflammatory phase followed by a proliferative phase, and finally by a remodeling phase. Despite this process, healed tendon fails to recover its original mechanical properties. In this review, we proposed to describe the key factors involved in the process such as cells, transcription factors, extracellular matrix components, cytokines and growth factors and vascularization among others. A better understanding of this healing process could help provide new therapeutic approaches to improve patients' recovery while tendon disorders management remains a medical challenge.

Aged Tendons Exhibit Altered Mechanisms of Strain-Dependent Extracellular Matrix Remodeling

Aging is a primary risk factor for degenerative tendon injuries, yet the etiology and progression of this degeneration is poorly understood. While aged tendons have innate cellular differences that support a reduced ability to maintain mechanical tissue homeostasis, the response of aged tendons to altered levels of mechanical loading has not yet been studied. To address this question, we subjected young and aged murine flexor tendon explants to various levels of in vitro tensile strain. We first compared the effect of static and cyclic strain on matrix remodeling in young tendons, finding that cyclic strain is optimal for studying remodeling in vitro. We then investigated the remodeling response of young and aged tendon explants after 7 days of varied mechanical stimulus (stress-deprivation, 1%, 3%, 5%, or 7% cyclic strain) via assessment of tissue composition, biosynthetic capacity, and degradation profiles. We hypothesized that aged tendons would show muted adaptive responses to changes in tensile strain and exhibit a shifted mechanical setpoint, at which the remodeling balance is optimal. Interestingly, we found 1% cyclic strain best maintains native physiology while promoting ECM turnover for both age groups. However, aged tendons display fewer strain-dependent changes, suggesting a reduced ability to adapt to altered levels of mechanical loading. This work has significant impact in understanding the regulation of tissue homeostasis in aged tendons, which can inform clinical rehabilitation strategies for treating elderly patients.

Biomechanical evaluation of the ST-knot: A new suture for flexor tendon repair

PURPOSE

Although tendon lacerations are common, there is currently no consensus on choice of suture. Easy and fast sutures that impart enough strength to allow mobilization are needed. This study compared the ex vivo biomechanical strength (force required to create a 2 mm tendon gap) of a novel suture (ST-knot) with that of a conventional suture (double Kessler).

MATERIALS AND METHODS

Forty fresh deep flexor tendons from porcine forelimbs were used. Both repaired tendon ends were mounted on standard traction jaws of an axial traction machine at an initial distance of 40 mm for all tendons. A high-definition camera was used to determine the force forming a 2 mm gap. Ten tendons in group 1 (ST-knot) and 10 in group 2 (double Kessler) were prepared with PDS 4.0 (single thread for Kessler, double thread for ST-knot). Tendons in groups 3 (ST-knot) and 4 (double Kessler) were repaired with PDS 1.0 using the same principle.

RESULTS

There was no significant difference in the force required to form a 2 mm tendon gap between groups 1 and 2, and this trend was identical when using a stronger thread in groups 3 and 4. The maximum force before rupture, mode of repair failure, stress and stiffness were also comparable, with no significant differences between groups 1 and 2, or between groups 3 and 4.

CONCLUSIONS

The ST-knot showed comparable results to the double-Kessler knot, whichever the thread used. Because it involves fewer steps than conventional techniques and is easy to perform, the ST-knot may offer a therapeutic solution, particularly in complex trauma with multiple tendon injury.

Applications of ultrasound elastography to hand and upper limb disorders

Ultrasound elastography is a recently developed method for accurate measurement of soft tissue stiffness in addition to the clinician's subjective evaluation. The present review briefly describes the ultrasound elastography techniques and outlines clinical applications for tendon, muscle, nerve, skin and other soft tissues of the hand and upper limb. Strain elastography provides a qualitative evaluation of the stiffness, and shear-wave elastography generates quantitative elastograms superimposed on a B-mode image. The stiffness in degenerative tendinopathy and/or tendon injury was significantly lower than in a normal tendon in several studies. Elastography is also a reliable method to evaluate functional muscle activity, compared to conventional surface electromyography. The median nerve is consistently stiffer in patients with carpal tunnel syndrome than in healthy subjects, on whatever ultrasound elastography technique. Elastography distinguishes normal skin from scars and can be used to evaluate scar severity and treatment. Elastography has huge clinical applications in musculoskeletal tissues. Continued development of systems and increased training of clinicians will expand our knowledge of elastography and its clinical applications in the future.

In vivo attenuation profile of 660 nm and 830 nm wavelengths on human elbow skin and calcaneus tendon of different phototypes

Physical factors and tissue characteristics determine the transmission of light through tissues. One of the significant clinical limitations of photobiomodulation is the quantification of fluence delivered at application sites and optical penetration depth in vivo. There is also the difficulty of determining the distances of the application points to cover a uniformly irradiated area. Thus, the aim was to evaluate in vivo the influence of melanin on light transmission of the 660 nm and 830 nm laser wavelengths on skin and tendon. Thirty young individuals of both sexes were recruited, divided into two groups based on melanin index, and submitted to photobiomodulation protocols in the posterior region of the elbow (skin-skin) and the calcaneus tendon (skin-tendon-skin). The irradiation area was evaluated using a homemade linear array of five sensors. We found significant transmission power values for different melanin indexes and wavelengths (p<0.0001). Also, different equipment can generate significant differences in the transmitted power at an 830-nm wavelength. Average scattering values are 14 mm and 21 mm for 660 nm, in higher and lower melanin index, respectively. For 830 nm, values of 20 mm and 26 mm are indicated. Laser light transmission in vivo tissues is related to wavelength, beam diameter, tissue thickness, and composition, as well as melanin index. The 830-nm laser presents higher light transmission on the skin than 660 nm. The distances between the application points can be different, with higher values for 830 nm than 660 nm.

Accessory Extensor Pollicis Longus Tendon Incidentally Discovered During Dorsal Distal Radius Plating

Anatomical variations of the extensor pollicis longus (EPL) tendon are rare. Variations are typically asymptomatic, yet knowledge of these variations poses significance in the setting of dorsal approaches to wrist surgery. We present a case of an accessory EPL tendon that was discovered intraoperatively in the fourth dorsal compartment during open repair of a distal radius fracture with a dorsal spanning plate. If not correctly identified, the accessory EPL could have been entrapped beneath the plate, resulting in limited thumb extension and potentially tendon rupture.

Shear-wave elastography for the evaluation of tendinopathies: a systematic review and meta-analysis

PURPOSE

To compare pathologic and healthy tendons using shear-wave elastography (SWE).

METHODS

A systematic review with meta-analysis was done searching Pubmed and EMBASE up to September 2022. Prospective, retrospective and cross-sectional studies that used SWE in the assessment of pathologic tendons versus control were included. Our primary outcome were SWE velocity (m/s) and stiffness (kPa). Methodological quality was assessed by the methodological index for non-randomized studies (MINORS). We used the mean difference (MD) with corresponding 95% confidence intervals (CIs) to quantify effects between groups. We performed sensitivity analysis in case of high heterogeneity, after excluding poor quality studies according to MINORS assessment. We used Grades of Recommendation, Assessment, Development and Evaluation to evaluate the certainty of evidence (CoE).

RESULTS

Overall, 16 studies with 676 pathologic tendons (188 Achilles, 142 patellar, 96 supraspinatus, 250 mixed) and 723 control tendons (484 healthy; 239 contralateral tendon) were included. Five studies (31.3%) were judged as poor methodological quality. Shear-wave velocity and stiffness meta-analyses showed high heterogeneity. According to a sensitivity analysis, pathologic tendons had a lower shear wave velocity (MD of - 1.69 m/s; 95% CI 1.85; - 1.52; n = 274; I2 50%) compared to healthy tendons with very low CoE. Sensitivity analysis on stiffness still showed high heterogeneity.

CONCLUSION

Pathological tendons may have reduced SWE velocity compared to controls, but the evidence is very uncertain. Future robust high-quality longitudinal studies and clear technical indications on the use of this tool are needed.

PROTOCOL

PROSPERO identifier: CRD42023405410 CLINICAL RELEVANCE STATEMENT: SWE is a relatively recent modality that may increase sensitivity and diagnostic accuracy of conventional ultrasound imaging promoting early detection of tendinopathy. Non-negligible heterogeneity has been observed in included studies, so our findings may encourage the conduct of future high-quality longitudinal studies which can provide clear technical indications on the use of this promising tool in tendon imaging.

Strain inhibition of bacterial collagenase is consistent with a collagen fibril uncrimping mechanism in rat tail tendons

Mechanical strain inhibits bacterial collagenase from cleaving collagen. Additionally, the toe region of a soft tissue's force-elongation curve arises from sequentially engaging collagen fibrils as the tissue lengthens. Together, these phenomena suggest that mechanical strain may gradually inhibit collagenase activity through a soft tissue's toe region. Therefore, this investigation sought to test this hypothesis. 92 rat tail tendon fascicles from 3 female sentinel animals underwent preliminary stiffness tests, and their force-elongation curves were fit to a collagen distribution model. This distribution-based model calculated the force magnitude corresponding to p% of collagen fibril engagement. Specimens were separated into one of five levels of p, and that level of force was maintained for two hours while being exposed to 0.054 U/mL of bacterial collagenase from C. histolyticum. The specimens were strained to failure following the creep test, and the relative reduction in stiffness was quantified to estimate the fraction of digested fibrils. Every 10% additional collagen engagement corresponded to a 6.3% (97% highest density interval: 4.3 - 8.4%) retention of stiffness, which indicated collagenase inhibition. The results of this investigation were consistent with a strain-inhibition hypothesis along with the established uncrimping mechanism in the toe region. These results support an interaction between mechanical strain and collagenolysis, which may be valuable for disease prevention or treatment.

Identification of Periostin as a critical niche for myofibroblast dynamics and fibrosis during tendon healing

Tendon injuries are a major clinical problem, with poor patient outcomes caused by abundant scar tissue deposition during healing. Myofibroblasts play a critical role in the initial restoration of structural integrity after injury. However, persistent myofibroblast activity drives the transition to fibrotic scar tissue formation. As such, disrupting myofibroblast persistence is a key therapeutic target. While myofibroblasts are typically defined by the presence of αSMA+ stress fibers, αSMA is expressed in other cell types including the vasculature. As such, modulation of myofibroblast dynamics via disruption of αSMA expression is not a translationally tenable approach. Recent work has demonstrated that Periostin-lineage (PostnLin) cells are a precursor for cardiac fibrosis-associated myofibroblasts. In contrast to this, here we show that PostnLin cells contribute to a transient αSMA+ myofibroblast population that is required for functional tendon healing, and that Periostin forms a supportive matrix niche that facilitates myofibroblast differentiation and persistence. Collectively, these data identify the Periostin matrix niche as a critical regulator of myofibroblast fate and persistence that could be targeted for therapeutic manipulation to facilitate regenerative tendon healing.

Arthroscopic subscapularis repair using the subscapularis interlocking (SICK)-stitch technique leads to restoration of clinical function with low complication and revision rates

Background

The purpose of this study is to determine the mid-term outcome after arthroscopic subscapularis tendon (SCP) reconstruction using the subscapularis interlocking (SICK)-stitch technique. The hypotheses are that arthroscopically repaired SCP lesions using the SICK-stitch show a good restoration of shoulder function with low complication and failure rates.

Methods

This is a retrospective monocentric study of n = 199 patients (n = 106 female) with arthroscopically treated SCP tears with the interlocking (SICK) stitch technique from July 2013 to October 2018. Inclusion criteria: minimum follow-up of 2 years. Exclusion criteria: irreparable and massive cuff tears, osteoarthritis, and fractures. The postoperative assessment consisted of the range of motion, constant score, simple shoulder test, simple shoulder value, disability of the shoulder and arm score, short form 12, and patient satisfaction.

Results

Mean age was 61 years (25-83); n = 4 (2%) patients were lost to follow-up with mean follow-up time of 63.6 months (36-96). Additional supraspinatus tendon lesions (n = 147) were repaired in n = 101 cases. SCP grading (n = 69) (35% traumatic) (Fox/Romeo): n = 113 grade II, n = 71 grade III, n = 11 grade IV. A positive preoperative lift-off test (n = 132, 68%) was corrected in n = 124 (94%) of cases. Ninety seven percent of patients would undergo surgery again with a mean satisfaction score of 14.4/15. Results at final follow-up (data: mean pre; post; P value): lexion (130; 166; .001), abduction (123;159; .001), external rotation (35;82; .001), internal rotation (52; 68; .07), constant score (50; 82; .001), disability of the shoulder and arm score (40; 19; .001), simple shoulder test (5; 10; .001), and simple shoulder value (44; 83; .001) significantly improved. The mean physical health scale short form 12 was 46 (24-63) and 51 (15-66) for mental health. Age, body mass index, SCP-grading, and supraspinatus tendon repair did not significantly affect any outcome parameter. Three (1.5%) patients underwent revision surgery, of which 1 (0.5%) had an infection.

Conclusion

Two years after arthroscopic SCP repair using the SICK-stitch technique, we observed excellent restoration of clinical function with low complication and revision rates. The SICK-stitch technique thus represents a good and reliable therapeutic option for the arthroscopic repair of SCP lesions.

Accessory Extensor Pollicis Longus Tendon Classification Modification

Supernumerary extensor pollicis longus (EPL) and extensor indicis proprius tendons are infrequently reported. There are few case reports on more than one accessory tendon in one individual. As a result, they are not represented in previously described classifications for variations in extensors to the thumb. Elective surgery was performed on a 57-year-old right-handed female. Within the fourth compartment, two anomalous accessory tendons were present. These tendons were identified as an accessory EPL tendon and an accessory extensor indicis proprius tendon. The normal EPL tendon occupied the third compartment ulnar to Lister's tubercle, as usual. The previous classification system for anomalous EPL tendons is useful in the organization and description of thumb extensor tendon variations. However, it is not a complete representation of the anomalies identified, including the one in this report. We have proposed an additional category for this classification system to better encompass the variation in anomalous tendon anatomy.

Association between quadriceps tendon elasticity and neuromuscular control in individuals with knee osteoarthritis

BACKGROUND

Knee osteoarthritis is a complex condition with established risk factors such as female sex, increasing age and body mass index, reduced quadriceps muscle strength and knee injury. Despite known associated risks, the role and behaviour of knee tendons in knee osteoarthritis remains unclear. This study explores the association between quadriceps tendon elasticity, muscle strength, neuromuscular control, proprioception and patient reported outcome measures in individuals with knee osteoarthritis.

METHODS

Adults with doctor-diagnosed knee osteoarthritis were recruited from rheumatology clinics and general practitioner practices. Quadriceps tendon elasticity was estimated using sonoelastography. Neuromuscular control data including electromyography, electromechanical delay and proprioception measures were included. Participants completed the Knee Injury and Osteoarthritis Outcome Score. Associations between elasticity values, physical and neuromuscular data and patient reported outcomes scores were evaluated using Spearman's correlations.

FINDINGS

Thirty-nine adults with knee osteoarthritis were eligible for inclusion. Increased tendon stiffness was negatively associated with rate of force development, time to half peak force and passive positioning sense in individuals with knee osteoarthritis. Similarly, patient reported symptoms were found to be associated with sonoelastography findings with moderate-strong associations observed between activities of daily living sport and recreation, pain and symptoms and between neuromuscular control measures and muscle strength.

INTERPRETATION

Stiffer tendon identified within the knee osteoarthritis group was associated with reduced neuromuscular control and knee joint proprioception. Stiffer quadriceps tendon may contribute to the poorer reported symptoms by knee osteoarthritis individuals. These findings may impact disease symptoms and progression which could lead to further joint impairment.

Tailoring the pore design of embroidered structures by melt electrowriting to enhance the cell alignment in scaffold-based tendon reconstruction

Tissue engineering of ligaments and tendons aims to reproduce the complex and hierarchical tissue structure while meeting the biomechanical and biological requirements. For the first time, the additive manufacturing methods of embroidery technology and melt electrowriting (MEW) were combined to mimic these properties closely. The mechanical benefits of embroidered structures were paired with a superficial micro-scale structure to provide a guide pattern for directional cell growth. An evaluation of several previously reported MEW fiber architectures was performed. The designs with the highest cell orientation of primary dermal fibroblasts were then applied to embroidery structures and subsequently evaluated using human adipose-derived stem cells (AT-MSC). The addition of MEW fibers resulted in the formation of a mechanically robust layer on the embroidered scaffolds, leading to composite structures with mechanical properties comparable to those of the anterior cruciate ligament. Furthermore, the combination of embroidered and MEW structures supports a higher cell orientation of AT-MSC compared to embroidered structures alone. Collagen coating further promoted cell attachment. Thus, these investigations provide a sound basis for the fabrication of heterogeneous and hierarchical synthetic tendon and ligament substitutes.

Second Extensor Compartment Entrapment in an Adult Following Distal Radius Fracture

Extensor tendon entrapment in the presence of distal radius fracture is a known but relatively uncommon complication. Single tendon or entire compartment entrapment has been described through the literature in youths and adults. However these findings generally are limited to a certain age demographic or are found on advanced imaging but are unable to be confirmed intraoperatively. We describe to our knowledge the first known description of second extensor compartment entrapment in an adult seen on computerized tomography scan and confirmed intraoperatively.

Recent advances of exosomes in soft tissue injuries in sports medicine: A critical review on biological and biomaterial applications

Sports medicine is generally associated with soft tissue injuries including muscle injuries, meniscus and ligament injuries, tendon ruptures, tendinopathy, rotator cuff tears, and tendon-bone healing during injuries. Tendon and ligament injuries are the most common sport injuries accounting for 30-40% of all injuries. Therapies for tendon injuries can be divided into surgical and non-surgical methods. Surgical methods mainly depend on the operative procedures, the surgeons and postoperative interventions. In non-surgical methods, cell therapy with stem cells and cell-free therapy with secretome of stem cell origin are current directions. Exosomes are the main paracrine factors of mesenchymal stem cells (MSCs) containing biological components such as proteins, nucleic acids and lipids. Compared with MSCs, MSC-exosomes (MSC-exos) possess the capacity to escape phagocytosis and achieve long-term circulation. In addition, the functions of exosomes from various cell sources in soft tissue injuries in sports medicine have been gradually revealed in recent years. Along with the biological and biomaterial advances in exosomes, exosomes can be designed as drug carriers with biomaterials and exosome research is providing promising contributions in cell biology. Exosomes with biomaterial have the potential of becoming one of the novel therapeutic modalities in regenerative researches. This review summarizes the derives of exosomes in soft tissue regeneration and focuses on the biological and biomaterial mechanism and advances in exosomal therapy in soft tissue injuries.

Abduction causes increased strain gradient compared to forward flexion: Evidence from a cadaver model of simultaneous strain study of the rotator cuff tendons

BACKGROUND

Various strain studies of the supraspinatus have been done in isolation. Given that rotator cuff muscles function as a group, it may be physiologically representative to measure strain behaviour with the glenohumeral joint intact. Here, we explored a novel method in measuring simultaneous strain behaviour of the rotator cuff tendons and investigated the effect of full-thickness anterior tear of the supraspinatus on the infraspinatus and subscapularis tendons.

METHODS

Nine cadaveric shoulders were evaluated on a customized rig. Using linear differential variable transducers to measure strain, each shoulder was subjected to up to 60° of elevation in the coronal, scapular, and sagittal planes. We also assessed 30° of external rotation and up to 60° of internal rotation of the humerus. Full-thickness anterior tear of the supraspinatus was then made before re-assessing strain patterns in the scapular plane.

FINDINGS

Strain measurements of the intact tendons revealed a significant strain gradient between the articular and bursal sides of the supraspinatus during increasing degrees of elevation in the coronal and scapular planes. Full thickness anterior tear of the supraspinatus is localised to the tendon and does not affect the surrounding cuff musculature, with a potential shielding effect of the infraspinatus during early glenohumeral abduction.

INTERPRETATION

Significant strain gradient exists between the articular and bursal sides of the supraspinatus during abduction but not during forward flexion in an intact glenohumeral joint. Rehabilitation exercises for anterior supraspinatus tears can be appropriately targeted on the remaining intact rotator cuff musculature.

Reliability of a special device for measuring the cross-sectional area of the patellar tendon by ultrasonography

The objective of this study was to evaluate the intra- and inter-rater reliability and agreement between conditions with and without a special device (SD) in the evaluation of the patellar tendon (PT) cross-sectional area (CSA). Forty trained adult volunteers participated in the study. With the knee positioned at 90°, the ultrasound probe was placed in the transverse plane at 25, 50, and 75% of the PT length. Two raters and one analyzer obtained the images. We use a two-way ANOVA with a significance level of α = 0.05. No significant differences were found between raters or conditions. Intra-rater reliability ranged from moderate to good. Inter-rater reliability without the SD ranged from low to good, improving from moderate to good when the SD was used. Evaluation of the PT ends showed a lower coefficient of variation with the SD. We observed a moderate correlation at the ends and a strong correlation in the middle between conditions. The mean difference in the three positions is small (~ 0.013 cm2/ ~ 1.7%) with an upper limit of 43.2% and a lower limit of 32.5%. Therefore, we conclude that the use of the SD can be employed for evaluating the PT ends, while for the central region, it becomes optional.

Advances in Regional Vascular Injection Techniques for the Delivery of Stem Cells to Musculoskeletal Injury Sites

Vascular injections of stem cells are a pertinent alternative to direct intralesional injections when treating multiple or extensive lesions or with lesions impossible to reach directly. Extensive research using stem cell tracking has shown that intra-arterial injections without the use of a tourniquet should be preferred over venous or arterial regional limb perfusion techniques using a tourniquet. The median artery is used for the front limbs and the cranial tibial artery for the hind limbs. Proper efficacy studies are still lacking but early clinical work seems promising.

Optimization of wrist tendon detection in virtual monochromatic images using dual energy-computed tomography

OBJECTIVES

To evaluate the depiction of wrist tendons in virtual monochromatic images (VMIs) during a dual-energy CT (DE-CT) with the VMI image of conventional equivalent to 120 kVp.

MATERIALS AND METHODS

Using Catphan600 and phantom analysis software for CT evaluation, measurements of VMI in a DE-CT were performed corresponding to the tube voltages of single-energy CT at 120 kVp. Using a Discovery CT750 HD CT scanner (GE Healthcare) with DE-CT technology, 73 patients were scanned. We calculated the CT number, image noise, visual score, and contrast noise ratio (CNR) at the extensor pollicis tendon, extensor digitorum tendon, and flexor tendon in 11 VMIs from the DE-CT and VMI image of conventional equivalent to 120 kVp. The results from the optimal VMIs were then compared with that of the VMI image of the conventional equivalent to 120 kVp.

RESULTS

The highest CT number and CNR for the tendon were for the 140 keV VMI in the DE-CT compared to the other energy levels. There were significantly higher CT numbers, CNR values, and visual scores for each tendon at 140 keV VMI with the DE-CT (p < 0.01) compared with a VMI image of conventional equivalent to 120 kVp.

CONCLUSION

Energy level of the VMIs during DE-CT for the best wrist tendon delineation was 140 keV. This value of 140 keV for the DE-CT was significantly higher than the CT number and CNR for the extensor pollicis, extensor digitorum, and flexor tendon compared with a VMI image of conventional equivalent to 120 kVp.

Equine Platelet-Rich Plasma

Platelet-rich plasma (PRP) is an orthobiologic therapy composed of platelets, leukocytes, red blood cells, and plasma proteins. PRP has been used for 20 years, but progress determining efficacy has been slow. The definitions and classification of PRP are reviewed, and the use of PRP for tendon, ligament, and joint disease is discussed with a focus on findings of basic science and clinical studies, platelet activation, concurrent administration of nonsteroidal anti-inflammatory drugs, and treatment complications. Finally, the advantages of platelet lysates and freeze-dried platelets are discussed. The promising results of a PRP lysate optimized for antibiofilm and antimicrobial properties are introduced.

On the contribution of solid and fluid behavior to the modeling of the time-dependent mechanics of tendons under semi-confined compression

The present work aims to investigate whether it is possible to identify and quantify the contributions of the interstitial fluid and the solid skeleton to the overall time-dependent behavior of tendons based on a single mechanical test. For this purpose, the capabilities of three different time-dependent models (a viscoelastic, a poroelastic and a poroviscoelastic) were investigated in the modeling of the experimental behavior obtained from semi-confined compression with stress relaxation tests transverse to collagen fibers. The main achieved result points out that the poroviscoelastic model was the only one capable to characterize both the experimental responses of the force and volume changes of the tissue samples. Moreover, further analysis of this model shows that while the kinematics of the sample are mainly governed by the fluid flow (pore pressure contribution of the model), the behavior intrinsically associated with the viscoelastic solid skeleton makes a significant contribution to the experimental force response. This study reinforces the importance of taking both the experimental kinematics and kinetics of tendon tissues into account during the constitutive characterization procedure.

Mmp14 is required for matrisome homeostasis and circadian rhythm in fibroblasts

The circadian clock in tendon regulates the daily rhythmic synthesis of collagen-I and the appearance and disappearance of small-diameter collagen fibrils in the extracellular matrix. How the fibrils are assembled and removed is not fully understood. Here, we first showed that the collagenase, membrane type I-matrix metalloproteinase (MT1-MMP, encoded by Mmp14), is regulated by the circadian clock in postnatal mouse tendon. Next, we generated tamoxifen-induced Col1a2-Cre-ERT2::Mmp14 KO mice (Mmp14 conditional knockout (CKO)). The CKO mice developed hind limb dorsiflexion and thickened tendons, which accumulated narrow-diameter collagen fibrils causing ultrastructural disorganization. Mass spectrometry of control tendons identified 1195 proteins of which 212 showed time-dependent abundance. In Mmp14 CKO mice 19 proteins had reversed temporal abundance and 176 proteins lost time dependency. Among these, the collagen crosslinking enzymes lysyl oxidase-like 1 (LOXL1) and lysyl hydroxylase 1 (LH1; encoded by Plod2) were elevated and had lost time-dependent regulation. High-pressure chromatography confirmed elevated levels of hydroxylysine aldehyde (pyridinoline) crosslinking of collagen in CKO tendons. As a result, collagen-I was refractory to extraction. We also showed that CRISPR-Cas9 deletion of Mmp14 from cultured fibroblasts resulted in loss of circadian clock rhythmicity of period 2 (PER2), and recombinant MT1-MMP was highly effective at cleaving soluble collagen-I but less effective at cleaving collagen pre-assembled into fibrils. In conclusion, our study shows that circadian clock-regulated Mmp14 controls the rhythmic synthesis of small diameter collagen fibrils, regulates collagen crosslinking, and its absence disrupts the circadian clock and matrisome in tendon fibroblasts.

Investigation of the effects of subacromial bursal tissue preservation and microfracture procedure on healing after rotator cuff repair in a rat model

INTRODUCTION

The aim of this study is to compare the preservation of bursal tissue and microfracture techniques and to examine the effectiveness of the combination of the two methods in rotator cuff tear healing in the rat shoulder.

HYPOTHESIS

Bursal tissue preservation combined with microfracture is more effective in the rotator cuff repair.

MATERIALS AND METHODS

Twenty-three male Sprague-Dawley rats were randomly divided into two groups. The bursal tissue was preserved in group 1 (n=11) and excised in group 2 (n=12). Groups were categorized into subgroups as L (left) and R (right) based on the shoulder side receiving microfracture (L received microfracture, R did not). Histopathological examination was performed using modified Bonar Score System.

RESULTS

Cell morphology grades of group 1 were lower than group 2 (p<0.05). In terms of collagen measurements, the grade of group 1L (bursa preservation+microfracture) was lower than groups 1R, 2L, and 2R, and the grade of group 1R was lower than groups 2L and 2R. Cellularity grades of group 2 were higher than group 1 (p<0.05). Extracellular matrix grades of group 1 were lower than group 2 (p<0.05). The overall grades were lower in group 1 than in group 2 (p<0.05).

DISCUSSION

Combined treatment of bursal tissue preservation and microfracture was the most efficient method as determined by healing findings in histopathological specimens. Preservation of bursal tissue was a more effective option in tendon healing than performing only microfracture.

LEVEL OF PROOF

II, animal research.

Adjacent tissues modulate shear wave propagation in axially loaded tendons

Shear wave tensiometry is a noninvasive approach for gauging tendon loads based on shear wave speed. Transient shear waves are induced and tracked via sensors secured to the skin overlying a superficial tendon. Wave speeds measured in vivo via tensiometry modulate with tendon load but are lower than that predicted by a tensioned beam model of an isolated tendon, which may be due to the added inertia of adjacent tissues. The objective of this study was to investigate the effects of adjacent fat tissue on shear wave propagation measurements in axially loaded tendons. We created a layered, dynamic finite element model of an elliptical tendon surrounded by subcutaneous fat. Transient shear waves were generated via an impulsive excitation delivered across the tendon or through the subcutaneous fat. The layered models demonstrated dispersive behavior with phase velocity increasing with frequency. Group shear wave speed could be ascertained via dispersion analysis or time-to-peak measures at sequential spatial locations. Simulated wave speeds in the tendon and adjacent fat were similar and modulated with tendon loading. However, wave speed magnitudes were consistently lower in the layered models than in an isolated tendon. For all models, the wave speed-stress relationship was well described by a tensioned beam model after accounting for the added inertia of the adjacent tissues. These results support the premise that externally excited shear waves are measurable in subcutaneous fat and modulate with axial loading in the underlying tendon. The model suggests that adjacent tissues add inertia to the system, which in turn lowers shear wave speeds. This information must be considered when using tensiometry as a clinical or research tool to infer absolute tendon loading.

Biomechanical Forces in the Tissue Engineering and Regeneration of Shoulder, Hip, Knee, and Ankle Joints

Tear on the tendon, ligament and articular cartilage of the joints do not heal by itself and new modalities of treatment are required to address the need for full restoration of joint functions. Accompanied by degenerative diseases, the healing of these tissues does not occur naturally and hence requires surgical interventions, but with associated morbidity. Tissue engineering strategies are now focusing on the effective incorporation of biomechanical stimulation by the application of biomechanical forces relevant to the tissue of interest to regenerate and engineer functional tissues. Bioreactors are being continuously developed to accomplish this goal. Although bioreactors have been developed, the advancement in the field of biomaterial, basic science, and cell engineering warrant further refinement for their effective use. In this article we reviewed the application of biomechanical forces in the tissue engineering and regeneration of the joints such as rotator cuff of shoulder, ball and socket joint of the hip, articular cartilage of knee, and the ankle joints.

Decoding the transcriptomic expression and genomic methylation patterns in the tendon proper and its peritenon region in the aging horse

OBJECTIVES

Equine tendinopathies are challenging because of the poor healing capacity of tendons commonly resulting in high re-injury rates. Within the tendon, different regions - tendon proper (TP) and peritenon (PERI) - contribute to the tendon matrix in differing capacities during injury and aging. Aged tendons have decreased repair potential; the underlying transcriptional and epigenetic changes that occur in the TP and PERI regions are not well understood. The objective of this study was to assess TP and PERI regional differences in adolescent, midlife, and geriatric horses using RNA sequencing and DNA methylation techniques.

RESULTS

Differences existed between TP and PERI regions of equine superficial digital flexor tendons by age as evidenced by RNASeq and DNA methylation. Cluster analysis indicated that regional distinctions existed regardless of age. Genes such as DCN, COMP, FN1, and LOX maintained elevated TP expression while genes such as GSN and AHNAK were abundant in PERI. Increased gene activity was present in adolescent and geriatric populations but decreased during midlife. Regional differences in DNA methylation were also noted. Notably, when evaluating all ages of TP against PERI, five genes (HAND2, CHD9, RASL11B, ADGRD1, and COL14A1) had regions of differential methylation as well as differential gene expression.