Tendon is a bradytrophic and hypovascular tissue, hence, healing remains a major challenge. The molecular key events involved in successful repair have to be unravelled to develop novel strategies that reduce the risk of unfavourable outcomes such as non-healing, adhesion formation, and scarring. This review will consider the diverse pathophysiological features of tendon-derived cells that lead to failed healing, including misrouted differentiation (e.g. de- or transdifferentiation) and premature cell senescence, as well as the loss of functional progenitors. Many of these features can be attributed to disturbed cell-extracellular matrix (ECM) or unbalanced soluble mediators involving not only resident tendon cells, but also the cross-talk with immigrating immune cell populations. Unrestrained post-traumatic inflammation could hinder successful healing. Pro-angiogenic mediators trigger hypervascularization and lead to persistence of an immature repair tissue, which does not provide sufficient mechano-competence. Tendon repair tissue needs to achieve an ECM composition, structure, strength, and stiffness that resembles the undamaged highly hierarchically ordered tendon ECM. Adequate mechano-sensation and -transduction by tendon cells orchestrate ECM synthesis, stabilization by cross-linking, and remodelling as a prerequisite for the adaptation to the increased mechanical challenges during healing. Lastly, this review will discuss, from the cell biological point of view, possible optimization strategies for augmenting Achilles tendon (AT) healing outcomes, including adapted mechanostimulation and novel approaches by restraining neoangiogenesis, modifying stem cell niche parameters, tissue engineering, the modulation of the inflammatory cells, and the application of stimulatory factors.

Cite this article: Bone Joint Res 2022;11(8):561–574.

Objectives. This study aimed to evaluate the histological and mechanical features of tendon healing in a rabbit model with second-harmonic-generation (SHG) imaging and tensile testing. Materials and Methods. A total of eight male Japanese white rabbits were used for this study. The flexor digitorum tendons in their right leg were sharply transected, and then were repaired by intratendinous stitching. At four weeks post-operatively, the rabbits were killed and the flexor digitorum tendons in both right and left legs were excised and used as specimens for tendon healing (n = 8) and control (n = 8), respectively. Each specimen was examined by SHG imaging, followed by tensile testing, and the results of the two testing modalities were assessed for correlation. Results. While the SHG light intensity of the healing tendon samples was significantly lower than that of the uninjured tendon samples, 2D Fourier transform SHG images showed a clear difference in collagen fibre structure between the uninjured and the healing samples, and among the healing samples. The mean intensity of the SHG image showed a moderate correlation (R. 2. = 0.37) with Young’s modulus obtained from the tensile testing. Conclusion. Our results indicate that SHG microscopy may be a potential indicator of tendon healing. Cite this article: E. Hase, K. Sato, D. Yonekura, T. Minamikawa, M. Takahashi, T. Yasui. Evaluation of the histological and mechanical features of tendon healing in a rabbit model with the use of second-harmonic-generation imaging and tensile testing. Bone Joint Res 2016;5:577–585. DOI: 10.1302/2046-3758.511.BJR-2016-0162.R1

Purpose: We hypothesised that the rate of tendon healing after arthroscopic repair of full-thickness tears of the supraspinatus is equivalent to that obtained with open techniques reported in the literature. Material and methods: We studied prospectively a cohort of 65 patients with arthroscopically repaired full-thickness tears of the supraspinatus. The patients were reviewed a mean 19 months (12–43) after repair. At arthroscopy, patients were aged 59.5 years on average (28–79). Bone-tendon sutures were performed with resorbable thread and self-locking anchors positioned on the lateral aspect of the humerus. Repair was protected with an abduction brace for six weeks. Forty-one patients (63%) accepted an arthroscan performed six months to two years after arthroscopy to assess tendon healing. Results: Ninety-four percent of the patients were satisfied with the outcome. The mean Constant score was 51.6±10.6 points preoperatively and 80.2±13.2 at last follow-up (p< 0.001). The arthroscan showed that the rotator cuff had healed in 70% of the cases (29/41). The supra-spinatus had not healed on the trochiter in eight cases (25%) and was partially healed in two (5%). The size of the residual tendon defect was less than the initial tear in all cases except one. The rate of patient satisfaction and function was not significantly different if the tendon had healed (Constant score 81.3/100, satisfaction 93%) or if there was a residual tendon defect (Constant score 77.5/100, satisfaction 92%). Shoulder force in patients with a healed tendon (6±1.9 kg) was better than in those with a tendon defect (4.5±2.8 kg), but the difference was not significant. Factors affecting tendon healing were age > 65 years (43% healing, p< 0.02), and wide tears. Conclusion: Arthroscopic repair of isolated supraspinatus tears enables tendon healing in 70% of cases as demonstrated by arthroscan. This rate was equivalent to those reported in historical series of open repair. Patients aged over 65 years had significantly less satisfactory healing. The absence of tendon healing does not compromise functional and subjective outcome despite reduced force

Objectives. Recently, the field of tissue engineering has made numerous advances towards achieving artificial tendon substitutes with excellent mechanical and histological properties, and has had some promising experimental results. The purpose of this systematic review is to assess the efficacy of tissue engineering in the treatment of tendon injuries. Methods. We searched MEDLINE, Embase, and the Cochrane Library for the time period 1999 to 2016 for trials investigating tissue engineering used to improve tendon healing in animal models. The studies were screened for inclusion based on randomization, controls, and reported measurable outcomes. The RevMan software package was used for the meta-analysis. Results. A total of 388 references were retrieved and 35 studies were included in this systematic review. The different biomaterials developed were analyzed and we found that they improve the biomechanical and histological characteristics of the repaired tendon. At meta-analysis, despite a high heterogeneity, it revealed a statistically significant effect in favour of the maximum load, the maximum stress, and the Young’s modulus between experimental and control groups. In the forest plot, the diamond was on the right side of the vertical line and did not intersect with the line, favouring experimental groups. Conclusions. This review of the literature demonstrates the heterogeneity in the tendon tissue engineering literature. Several biomaterials have been developed and have been shown to enhance tendon healing and regeneration with improved outcomes. Cite this article: D. González-Quevedo, I. Martínez-Medina, A. Campos, F. Campos, V. Carriel. Tissue engineering strategies for the treatment of tendon injuries: a systematic review and meta-analysis of animal models. Bone Joint Res 2018;7:318–324. DOI: 10.1302/2046-3758.74.BJR-2017-0326

Aims

Despite recent advances in arthroscopic rotator cuff repair, re-tear rates remain high. New methods to improve healing rates following rotator cuff repair must be sought. Our primary objective was to determine if adjunctive bone marrow stimulation with channelling five to seven days prior to arthroscopic cuff repair would lead to higher Western Ontario Rotator Cuff (WORC) scores at 24 months postoperatively compared with no channelling.

Tendons mainly consist of collagen in order to withstand high tensile forces. Compared to other, high turnover tissues, cellularity and vascularity in tendons are low. Thus, the natural healing process of tendons takes long and can be problematic. In case of injury to the enthesis, the special transition from tendon over cartilage to bone is replaced by a fibrous scar tissue, which remains an unsolved problem in rotator cuff repair. To improve tendon healing, many different approaches have been described using scaffolds, stem cells, cytokines, blood products, gene therapy and others. Despite promising in vitro and in vivo results, translation to patient care is challenging. In clinics however, tendon auto- or allografts remain still first choice to augment tendon healing if needed. Therefore, it is important to understand natural tendon properties and natural tendon healing first. Like in other tissues, senescence of tenocytes seems to play an important role for tendon degeneration which is interestingly not age depended. Our in vivo healing studies have shown improved and accelerated healing by adding collagen type I, which is now used in clinics, for example for augmentation of rotator cuff repair. Certain cytokines, cells and scaffolds may further improve tendon healing but are not yet used routinely, mainly due to missing clinical data, regulatory issues and costs. In conclusion, the correct diagnosis and correct first line treatment of tendon injuries are important to avoid the necessity to biologically augment tendon healing. However, strategies to improve and accelerate tendon healing are still desirable. New treatment opportunities may arise with further advances in tendon engineering in the future

Tendon injuries present a major clinical challenge, as they necessitate surgical intervention and are prone to fibrotic progression. Despite advances in physical therapy and surgical technique, tendons fail to return to full native functioning, underlining the need for a biological therapeutic to improve tendon healing. Myofibroblasts are activated fibroblasts that participate in the proliferative and remodeling phases of wound healing, and while these matrix-producing cells are essential for proper healing, they are also linked to fibrotic initiation. A subset of tenocytes has been shown to give rise to the myofibroblast fate, and potentially contribute to fibrotic tendon healing. A viable anti-fibrotic therapy in other tissues has been reprogramming the fibroblast-myofibroblast differentiation route, avoiding a more pro-fibrotic myofibroblast phenotype. Thus, defining the molecular programs that underlie both physiological and pathological tendon healing is critical for the development of potential pharmacologic treatments. Towards that end, we have taken advantage of spatial transcriptomics, using the tenocyte marker Scleraxis as a tool, and have outlined three major spatiotemporally distinct tenocyte differentiation trajectories (synthetic, proliferative, and reactive) following acute tendon injury in mouse FDL. We have further outlined key transcriptional controls that may be manipulated to alter the differentiation process and influence the resulting myofibroblast phenotype, thereby promoting regenerative tendon healing

Tendons are characterised by an inferior healing capacity when compared to other tissues, ultimately resulting in the formation of a pathologically altered extracellular matrix structure. Although our understanding of the underlying causes for the development and progression of tendinopathies remains incomplete, mounting evidence indicates a coordinated interplay between tendon-resident cells and the ECM is critical. Our recent results demonstrate that the matricellular protein SPARC (Secreted protein acidic and rich in cysteine) is essential for regulating tendon tissue homeostasis and maturation by modulating the tissue mechanical properties and aiding in collagen fibrillogenesis [1,2]. Consequently, we speculate that SPARC may also be relevant for tendon healing. In a rat patellar tendon window defect model, we investigated whether the administration of recombinant SPARC protein can modulate tendon healing. Besides the increased mRNA expression of collagen type 1 and the downregulation of collagen type 3, a robust increase in the expression of pro-regenerative fibroblast markers in the repair tissue after a single treatment with rSPARC protein was observed. Additionally, pro-fibrotic markers were significantly decreased by the administration of rSPARC. Determination of structural characteristics was also assessed, indicating that the ECM structure can be improved by the application of rSPARC protein. Therefore, we believe that SPARC plays an important role for tendon healing and the application of recombinant SPARC to tendon defects has great potential to improve functional tendon repair

Approximately 30% of general practice consultations for musculoskeletal pain are related to tendon disorders, causing substantial personal suffering and enormous related healthcare costs. Treatments are often prone to long rehabilitation times, incomplete functional recovery, and secondary complications following surgical repair. Overall, due to their hypocellular and hypovascular nature, the regenerative capacity of tendons is very poor and intrinsically a disorganized scar tissue with inferior biomechanical properties forms after injury. Therefore, advanced therapeutic modalities need to be developed to enable functional tissue regeneration within a degenerative environment, moving beyond pure mechanical repair and overcoming the natural biological limits of tendon healing. Our recent studies have focused on developing biologically augmented treatment strategies for tendon injuries, aiming at restoring a physiological microenvironment and boosting endogenous tissue repair. Along these lines, we have demonstrated that the local application of mesenchymal stromal cell-derived small extracellular vesicles (sEVs) has the potential to improve rotator cuff tendon repair by modulating local inflammation and reduce fibrotic scarring. In another approach, we investigated if the local delivery of the tendon ECM protein SPARC, which we previously demonstrated to be essential for tendon maturation and tissue homeostasis, has the potential to enhance tendon healing. Finally, I will present results demonstrating the utility of nanoparticle-delivered, chemically modified mRNAs (cmRNA) to improve tendon repair

To analyse the efficacy and safety of cellular therapy utilizing Mesenchymal Stromal Cells (MSCs) in the management of rotator cuff(RC) tears from clinical studies available in the literature. We conducted independent and duplicate electronic database searches including PubMed, Embase, Web of Science, and Cochrane Library on August 2021 for studies analyzing the efficacy and safety of cellular therapy (CT) utilizing MSCs in the management of RC tears. VAS for pain, ASES Score, DASH Score, Constant Score, radiological assessment of healing and complications and adverse events were the outcomes analyzed. Analysis was performed in R-platform using OpenMeta [Analyst] software. RESULTS:. 6 studies involving 238 patients were included for analysis. We noted a significant reduction in VAS score for pain at 3 months (WMD=-2.234,p<0.001) and 6 months (WMD=-3.078,p<0.001) with the use of CT. Concerning functional outcomes, utilization of CT produced a significant short-term improvement in the ASES score (WMD=17.090,p<0.001) and significant benefit in functional scores such as Constant score (WMD=0.833,p=0.760) at long-term. Moreover, we also observed a significantly improved radiological tendon healing during the long-term follow-up (OR=3.252,p=0.059). We also noted a significant reduction in the retear rate upon utilization of CT in RC tears both at short- (OR=0.079,p=0.032) and long-term (OR=0.434,p=0.027). We did not observe any significant increase in the adverse events as compared with the control group (OR=0.876,p=0.869). Utilization of CT in RC tear is safe and it significantly reduced pain severity, improved functional outcome, enhanced radiological tendon healing, and mitigated retear rates at short- and long-term follow-up

Chronic Achilles tendinopathy is characterised by sub-acute inflammation with pro-inflammatory type 1 macrophages (M1), tissue degeneration and consequent partial or total tendon injury. Control of the inflammatory response and M1-to-M2 macrophage polarisation can favour tendon healing both directly and indirectly, by allowing for the regenerative process driven by local mesenchymal stem cells. Ten patients (3 females and 7 males aged between 32 and 71 years old) with partial Achilles tendon injury were treated with injections of autologous peripheral blood mononuclear cells (PB-MNCs). The cell concentrate was obtained from 100-120 cc of each patient's blood with a selective point-of-care filtration system. PB-MNCs remained trapped in the filter and were injected immediately after sampling. Around 60% of the PB-MNC concentrate was injected directly into the injured area, while the remaining 40% was injected in smaller amounts into the surrounding parts of the Achilles tendon affected by tendinosis. All patients were evaluated both clinically with the help of the American Orthopaedic Foot & Ankle Society (AOFAS) scale, and radiologically (MRI examination) at baseline and 2 months after the PB-MNC injection. A clinical reassessment with the AOFAS scale was also performed 6 months after the intervention. The rehabilitation protocol implied full weight-bearing walking immediately after the procedure, light physical activity 3-4 days after the injection, and physiotherapist-assisted stretching exercises and eccentric training. In all patients, functional and radiological signs of tendon healing processes were detected as early as 2 months after a single treatment and the AOFAS scale rose from the initial mean value of 37.5 (baseline) to 85.4 (6 months). Our preliminary results indicate that regenerative therapies with PB-MNCs can prove useful for partial Achilles tendon injuries as a valid alternative to surgical options, especially when other conservative approaches have failed. Advantages of this therapy include rapid execution, no need for an operating theatre, easy reproducibility, quick recovery and good tolerability regardless of the patient's age (the procedure is not to be performed in subjects who are below 18 years old). Further studies on the topic are recommended to confirm these observations

Aims. In the context of tendon degenerative disorders, the need for innovative conservative treatments that can improve the intrinsic healing potential of tendon tissue is progressively increasing. In this study, the role of pulsed electromagnetic fields (PEMFs) in improving the tendon healing process was evaluated in a rat model of collagenase-induced Achilles tendinopathy. Methods. A total of 68 Sprague Dawley rats received a single injection of type I collagenase in Achilles tendons to induce the tendinopathy and then were daily exposed to PEMFs (1.5 mT and 75 Hz) for up to 14 days - starting 1, 7, or 15 days after the injection - to identify the best treatment option with respect to the phase of the disease. Then, 7 and 14 days of PEMF exposure were compared to identify the most effective protocol. Results. The daily exposure to PEMFs generally provided an improvement in the fibre organization, a decrease in cell density, vascularity, and fat deposition, and a restoration of the physiological cell morphology compared to untreated tendons. These improvements were more evident when the tendons were exposed to PEMFs during the mid-acute phase of the pathology (7 days after induction) rather than during the early (1 day after induction) or the late acute phase (15 days after induction). Moreover, the exposure to PEMFs for 14 days during the mid-acute phase was more effective than for 7 days. Conclusion. PEMFs exerted a positive role in the tendon healing process, thus representing a promising conservative treatment for tendinopathy, although further investigations regarding the clinical evaluation are needed. Cite this article: Bone Joint Res 2020;9(9):613–622

Introduction. It is an example of tendon to bone healing of rotator cuff tears. Low Level Laser Therapy (LLLT) is used in pain literature, pain palliation, tendinopathies, osteoarthritis treatment, implant osteointegration in jaw surgery, wound healing, fracture healing, tendon healing, nerve healing. But; there is not a study on tendon-bone healing. It is aimed to investigate the effects of tendon to bone healing with the rotator cuff experimental tear model. Material and Methods. 60 Wistor Albino Rat right shoulders were used in our project in four groups. Effectiveness of the study in each study group to increase and use the minimum number of animals that would be significant it was planned to use 15 (6 histology + 9 biomechanical) subjects. In our study, there are 4 groups in total. 1. Group 4. Week sacrified control group 2. Group 4. Week sacrificed LLLT group 3. Group 8. Week sacrified control group 4. Group is postoperative LLLT group. The 4 round SSP tendons have been cut with a full course. A total of eight sessions of biostimulation were performed with 24 j energy per session. Biomechanical tensile test and histopathological examination were performed on rats sacrificed at 4 and 8 weeks. In histological examination, cellularity at the repair site with hemotoxylin-eosin staining, extracellular matrix localization with Masson trichrome staining and fibrosis, TRAP (Tartrate Resistance Acid Phosphatase) and osteoclast activity, collagen fibril organization with picrochucine were evaluated. In immunohistological examination, proliferation activity was evaluated by CD-31 (Abcam, Cambridge, MA, USA) through vascular endothelial cells, Ki-67 (Tucson, AZ) and tendon proliferation index. Failure load for comparison of biomechanical stability between groups drawing will be done. Biomechanical pulling applications Linear pulling force over tendon It will be realized by applying. Last failure load (Newton), elongation (mm) and hardness values was recorded. Results. Two rats died in the postoperative first group and one rat died in the other groups. Six animals from each group were examined histopathologically. While the mean of stifness was higher in the patient who underwent LLLT at the 4th week biomechanically compared to the control group, there was no difference in the 8th week between the control group LLLT biomechanically. Histologically, the group with LLLT at 4 weeks showed increased fibroblastic activity and osteoclastic activity, but at 8 weeks there was no significant difference. Discussion. There are studies on the benefits of biostimulation with LLLT in fracture healing, implant integration, wound healing, tendon healing. Biostimulation experiments with LLLT for tendon healing were evaluated in rotator cuff healing as they were not available in literature. Especially early contributions were thought to be beneficial for postoperative rupture

Partial thickness abductor tendon tears are a significant source of recalcitrant laterally based hip pain. For those that fail conservative treatment, the results of endoscopic repair are highly successful with minimal morbidity. The principal burden is the protracted rehabilitation that is necessary as part of the recovery process. There is a wide gap between failed conservative treatment and successful surgical repair. It is hypothesized that a non-repair surgical strategy, such as a bioinducitve patch, could significantly reduce the burden associated recovery from a formal repair. Thus, the purpose of this study is to report the preliminary results of this treatment strategy. Symptomatic partial thickness abductor tendon tears are treated conservatively, including activity modification, supervised physical therapy and ultrasound guided corticosteroid injections. Beginning in January 2022, patients undergoing hip arthroscopy for intraarticular pathology who also had persistently symptomatic partial thickness abductor tendon tears, were treated with adjunct placement of a bioinducitve (Regeneten) patch over the tendon lesion from the peritrochanteric space. The postop rehab protocol is dictated by the intraarticular procedure performed. All patients are prospectively assessed with a modified Harris Hip Score (mHHS) and iHOT and the tendon healing response examined by ultrasound. Early outcomes will be presented on nine consecutive cases. Conclusions - Will be summarized based on the preliminary outcomes to be reported

Digital Ventilated Cages (DVC) offer an innovative technology to obtain accurate movement data from a single mouse over time [1]. Thus, they could be used to determine the occurrence of a tendon damage event as well as inform on tissue regeneration [2,3]. Therefore, using the mouse model of tendon experimental damage, in this study it has been tested whether the recovery of tissue microarchitecture and of extracellular matrix (ECM) correlates with the motion data collected through this technology. Mice models were used to induce acute injury in Achilles tendons (ATs), while healthy ones were used as control. During the healing process, the mice were housed in DVC cages (Tecniplast) to monitor animal welfare and to study biomechanics assessing movement activity, an indicator of the recovery of tendon tissue functionality. After 28 days, the AT were harvested and assessed for their histological and immunohistochemical properties to obtain a total histological score (TSH) that was then correlated to the movement data. DVC cages showed the capacity to distinguish activity patterns in groups from the two different conditions. The data collected showed that the mice with access to the mouse wheel had a higher activity as compared to the blocked wheel group, which suggests that the extra movement during tendon healing improved motion ability. The histological results showed a clear difference between different analyzed groups. The bilateral free wheel group showed the best histological recovery, offering the highest TSH score, thus confirming the results of the DVC cages and the correlation between movement activity and structural recovery. Data obtained showed a correlation between TSH and the DVC cages, displaying structural and movement differences between the tested groups. This successful correlation allows the usage of DVC type cages as a non-invasive method to predict tissue regeneration and recovery. Acknowledgements: This research is part of the P4FIT project ESR13, funded by the H2020-ITN-EJD MSCA grant agreement No.955685

The aim of the study is to determine the histological, biochemical, and biomechanical efficacy of fibrin clot and vitamin C in the healing of Achilles tendon ruptures (ATR) in a rat model.52 adult Wistar Albino rats (300–450 g) were used in the study. 12 groups were divided into four groups as Monitor (Group I), Control (Group II), Fibrin Clot (Group III), Fibrin Clot with vitamin C (Group IV). Four rats were used to obtain fibrin clots. Fibroblast Growth Factor (FGF) and Vascular Endothelial Growth Factor (VEGF) were measured in the blood of tail vein (1 cc) on the 3rd, 7th, 14th, and 21st day. Four rats were sacrificed on the 21st day from each group for histological evaluation. The rest of the rats were sacrificed at 42nd day, half for biomechanical and a half for histological evaluation. The 42nd-day HSS scores in group III and group IV were significantly lower than those of group I and group II (p =0.036 and 0.019; respectively). The 42nd-day HSS score of group IV was significantly lower than group III (p =0.036). The Maximum force N value of group III and group IV was significantly higher than those of group I and group II (p <0.05). Group IV showed a significantly higher Maximum force N value than group III (p =0.025). The blood FGF and VEGF levels of group III and group IV on the 3rd, 7th, 14th, and 21st days were higher than those of group I and group II (p <0.05). In the experimentally formed ATR model, fibrin clot and vitamin C produced a stronger tendon structure in terms of biomechanics while providing histological and biochemically better quality tendon healing in the surgical treatment of ATR. We believe that this model can be used to accelerate high-quality tendon healing after ATR

Early identification of patients at risk for impaired tendon healing and corresponding novel therapeutic approaches are urgent medical needs. This study aimed to clarify the role of CD3+ T-cells during acute Achilles tendon (AT) healing. Blood and hematoma aspirate were taken from 26 patients during AT reconstruction, and additional blood samples were obtained during clinical follow-up at 6, 26 and 52 weeks after surgery. T-cell subsets were analyzed by flow cytometry using CD3, CD4, CD8, CD11a, CD57 and CD28 antibodies. Clinical follow-up included functional tests, MRI assessments, and subjective questionnaires. In vitro, the functional behavior of patient-derived tenocytes was investigated in co-cultures with autologous unpolarized CD4+ or CD8+ T-cells, or IFNy-polarized CD8+ or IL17-polarized CD4+ Tcells (n=5-6). This included alterations in gene expression (qPCR), MMP secretion (ELISA), migration rate (scratch wound healing assay) or contractility (collagen gels). Analysis revealed that elevated CD4+ T-cell levels and reduced CD8+ T-cell levels (increased CD4/CD8 ratio) in hematoma aspirate and pre-operative blood were associated with inferior clinical outcomes regarding pain and function at 26 and 52 weeks. Increased levels of CD8+ -memory T-cell subpopulations in blood 6 weeks after surgery were associated with less tendon elongation. In vitro, tenocytes showed increased MMP1/2/3 levels and collagen III/I ratio in co-culture with unpolarized and/or IL17-polarized CD4+ T-cells compared to unpolarized CD8+ T-cells. This coincided with increased IL17 receptor expression in tenocytes co-cultured with CD4+ T-cells. Exposure of tenocytes to IL17-polarized CD4+ T-cells decreased their migration rate and increased their matrix contractility, especially compared to IFNy-polarized CD8+ T-cells. The CD4+ /CD8+ T-cell ratio could serve as prognostic marker for early identification of patients with impaired AT healing potential. Local reduction of CD4+ T-cell levels or their IL17 secretion represent a potential therapeutic approach to improve AT healing and to prevent weakening of the tendon ECM

During aging, tendons demonstrate substantial disruptions in homeostasis, leading to impairments in structure-function. Impaired tendon function contributes to substantial declines quality of life during aging. Aged tendons are more likely to undergo spontaneous rupture, and the healing response following injury is impaired in aged tendons. Thus, there is a need to develop strategies to maintain tendon homeostasis and healing capacity through the lifespan. Tendon cell density sharply declines by ∼12 months of age in mice, and this low cell density is retained in geriatric tendons. Our data suggests that this decline in cellularity initiates a degenerative cascade due to insufficient production of the extracellular matrix (ECM) components needed to maintain tendon homeostasis. Thus, preventing this decline in tendon cellularity has great potential for maintaining tendon health. Single cell RNA sequencing analysis identifies two changes in the aged tendon cell environment. First, aged tendons primarily lose tenocytes that are associated with ECM biosynthesis functions. Second, the tenocytes that remain in aged tendons have disruptions in proteostasis and an increased pro-inflammatory phenotype, with these changes collectively termed ‘programmatic skewing'. To determine which of these changes drives homeostatic disruption, we developed a model of tenocyte depletion in young animals. This model decreases tendon cellularity to that of an aged tendon, including decreased biosynthetic tenocyte function, while age-related programmatic skewing is absent. Loss of biosynthetic tenocyte function in young tendons was sufficient to induce homeostatic disruption comparable to natural aging, including deficits in ECM organization, composition, and material quality, suggesting loss biosynthetic tenocytes as an initiator of tendon degeneration. In contrast, our data suggest that programmatic skewing underpins impaired healing in aged tendons. Indeed, despite similar declines in the tenocyte environment, middle-aged and young-depleted tendons mount a physiological healing response characterized by robust ECM synthesis and remodeling, while aged tendons heal with insufficient ECM

Depletion of Scleraxis-lineage (ScxLin) cells in adult tendon recapitulates age-related decrements in cell density, ECM organization and composition. However, depletion of ScxLin cells improves tendon healing, relative to age-matched wildtype mice, while aging impairs healing. Therefore, we examined whether ScxLin depletion and aging result in comparable shifts in the tendon cell environment and defined the intrinsic programmatic shifts that occur with natural aging, to define the key regulators of age-related healing deficits. ScxLin cells were depleted in 3M-old Scx-Cre+; Rosa-DTRF/+ mice via diphtheria toxin injections into the hindpaw. Rosa-DTRF/+ mice were used as wildtype (WT) controls. Tendons were harvested from 6M-old ScxLin depleted and WT mice, and 21-month-old (21M) C57Bl/6 mice (aged). FDL tendons (n=6) were harvested for single-cell RNAseq, pooled, collagenase digested, and sorted for single cell capture. Data was processed using Cell Ranger and then aligned to the annotated mouse genome (mm10). Filtering, unsupervised cell clustering, and differential gene expression (DEG) analysis were performed using Seurat. Following integration and sub-clustering of the tenocyte populations, five distinct subpopulations were observed. In both ScxLin depletion and aging, ‘ECM synthesizers’ and ‘ECM organizers’ populations were lost, consistent with disruptions in tissue homeostasis and altered ECM composition. However, in ScxLin depleted mice retention of a ‘specialized ECM remodeler’ population was observed, while aging tendon cells demonstrated inflammatory skewing with retention of a ‘pro-inflammatory tenocyte population’. In addition, enrichment of genes associated with protein misfolding clearance were observed in aged tenocytes. Finally, a similar inflammatory skewing was observed in aged tendon-resident macrophages, with this skewing not observed in ScxLin depleted tendons. These data suggest that loss of ‘ECM synthesizer’ populations underpins disruptions in tendon homeostasis. However, retention of ‘specialized remodelers’ promotes enhanced healing (ScxLin depletion), while inflammatory skewing may drive the impaired healing response in aged tendons

Tendinopathy is a tendon pathology often resulting from a failed healing response to tendon injury. Activated protein C (APC) is a natural anti-coagulant with anti-inflammatory and wound healing promoting functions, which are mainly mediated by its receptors, endothelial protein C receptor (EPCR) and protease activated receptors (PARs). This study aimed to determine whether APC stimulates tenocyte healing and if so, to assess the involvement of the receptors. Mouse-tail tenocytes were isolated from 3-week-old wild type (WT), PAR- 1 knockout (KO) and PAR-2 KO mice. The expression of EPCR, PAR-1 and −2 and the effect of APC on tenocytes tendon healing and the underlying mechanisms were investigated by Reverse transcription real time PCR, western blot, 3- (4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) assay, zymography, and scratch wound healing/ migration assay. When compared to WT cells, PAR-1 KO tenocytes showed increased cell proliferation (3.3-fold, p<0.0001), migration (2.7-fold, p<0.0001) and wound healing (3-fold, p<0.0001), whereas PAR-2 KO cells displayed decreased cell proliferation (0.6-fold, p<0.05) and no change in cell migration or wound healing. APC at 1 μg/ml stimulated WT and PAR-1 KO tenocyte proliferation (~1.3, respectively, p<0.05) and wound healing (~1.3-fold, respectively, p<0.05), and additionally promoted PAR1-KO cell migration (1.4-fold, p<0.0001). APC only increased the migration (2-fold, p<0.05) of PAR-2 KO tenocytes. The activation of AKT, extracellular signal-regulated kinase (ERK)-2, and glycogen synthase kinase (GSK)-β3, the intracellular molecules that are associated with cell survival/growth, and matrix metalloproteinase (MMP)-2 that is related to cell migration and wound healing, were increased in all three cell lines in response to APC treatment. These findings show that PAR-1 and PAR-2 act differentially in tenocyte proliferation/migration/wound healing. APC likely promotes tenocyte proliferation/ wound healing via PAR-2, not PAR-1

Adipose-derived stem cells (ADSCs) are an effective alternative for Teno-regeneration. Despite their applications in tendon engineering, the mechanisms promoting tendon healing still need to be understood. Since there is scattered information on ovine ADSCs, this research aims to investigate in vitro their teno-differentiation for potential use in preclinical tendon regeneration models. Ovine ADSCs were isolated from the tail region according to FAT-STEM laboratories, expanded until passage six (P6), and characterized in terms of stemness, adhesion and MHC markers by Flow Cytometry (FCM) and immunocytochemistry (ICC). Cell proliferation and senescence were evaluated with MTT and Beta-galactosidase assays, respectively. P1 ADSCs’ teno-differentiation was assessed by culturing them with teno-inductive Conditioned Media (CM) or engineering them on tendon-mimetic PLGA scaffolds. ADSCs teno-differentiation was evaluated by morphological, molecular (qRT-PCR), and biochemical (WesternBlot) approaches. ADSCs exhibited mesenchymal phenotype, positive for stemness (SOX2, NANOG, OCT4), adhesion (CD29, CD44, CD90, CD166) and MHC-I markers, while negative for hematopoietic (CD31, CD45) and MHC-II markers, showing no difference between passages. ICC staining confirmed these results, where ADSCs showed nuclear positivity for SOX2 (≅ 56%) and NANOG (≅ 67%), with high proliferation capacity without senescence until P6. Interestingly, ADSCs cultured with the teno-inductive CM did not express tenomodulin (TNMD) protein or gene. Conversely, ADSCs seeded on scaffolds teno-differentiated, acquiring a spindle shape supported by TNMD protein expression at 48h (p<0.05 vs. ADSCs 48h) with a significant increase at 14 days of culture (p<0.05 vs. ADSCs + fleece 48h). Ovine ADSCs respond differently upon distinct teno-inductive strategies. While the molecules on the CM could not trigger a teno-differentiation in the cells, the scaffold's topological stimulus did, resulting in the best strategy to apply. More insights are requested to better understand ovine ADSCs’ tenogenic commitment before using them in vivo for tendon regeneration. Acknowledgements: This research is part of the P4FIT project ESR5, under the H2020MSCA-ITN-EJD-P4 FIT-Grant Agreement ID:955685

Objectives. Emerging evidence indicates that tendon disease is an active process with inflammation that is critical to disease onset and progression. However, the key cytokines responsible for driving and sustaining inflammation have not been identified. Methods. We performed a systematic review of the literature using MEDLINE (U.S. National Library of Medicine, Bethesda, Maryland) in March 2017. Studies reporting the expression of interleukins (ILs), tumour necrosis factor alpha (TNF-α) and interferon gamma in diseased human tendon tissues, and animal models of tendon injury or exercise in comparison with healthy control tissues were included. Results. IL-1β, IL-6, IL-10, and TNF-α are the cytokines that have been most frequently investigated. In clinical samples of tendinopathy and tendon tears, the expression of TNF-α tended not to change but IL-6 increased in tears. Healthy human tendons showed increased IL-6 expression after exercise; however, IL-10 remained unchanged. Animal tendon injury models showed that IL-1β, IL-6, and TNF-α tend to increase from the early phase of tendon healing. In animal exercise studies, IL-1β expression showed a tendency to increase at the early stage after exercise, but IL-10 expression remained unchanged with exercise. Conclusions. This review highlights the roles of IL-1β, IL-6, IL-10, and TNF-α in the development of tendon disease, during tendon healing, and in response to exercise. However, there is evidence accumulating that suggests that other cytokines are also contributing to tendon inflammatory processes. Further work with hypothesis-free methods is warranted in order to identify the key cytokines, with subsequent mechanistic and interaction studies to elucidate their roles in tendon disease development. Cite this article: W. Morita, S. G. Dakin, S. J. B. Snelling, A. J. Carr. Cytokines in tendon disease: A Systematic Review. Bone Joint Res 2017;6:656–664. DOI: 10.1302/2046-3758.612.BJR-2017-0112.R1

Recent studies on animal models focused on the effect of preserving tendon remnant of rotator cuff on tendon healing. A positive effect by combining tendon remnant preservation and small bone vents on the greater tuberosity in comparison with standard tendon-to-bone repair has been shown. The purpose of the present clinical study was to evaluate the efficacy of biologic augmentation of arthroscopic rotator cuff repair by maintaining tendon remnant on rotator cuff footprint combined with small bone vents of the greater tuberosity. A retrospective study was conducted. All patients who underwent arthroscopic rotator cuff repair associated with small bone vents (nanofractures) and tendon footprint preservation were considered eligible for the study. Inclusion criteria were: diagnosis of full-thickness rotator cuff tear as diagnosed at preoperative magnetic resonance imaging (MRI) and confirmed at the time of surgery; minimum 24-month of follow-up and availability of post-operative MRI performed not earlier than 6 months after surgery. Exclusion criteria were: partial thickness tears, irreparable tears, capsulo-labral pathologies, calcific tendonitis, gleno-humeral osteoarthritis and/or previous surgery. Primary outcome was the ASES score. Secondary outcomes were: Quick-DASH and WORC scores, and structural integrity of repaired tendons by magnetic resonance imaging (MRI) performed six months after surgery. A paired t-test was used to compare pre- and postoperative clinical outcomes. Subgroup analysis was performed according to tear size. Significance was set at p < 0.05. The study included 29 patients (M:F = 15:14). Mean age (+ SD) of patients was 61.7 + 8.9 years. Mean follow-up was 27.4 ± 2.3 months. Comparison between pre- and postoperative functional scores showed significant clinical improvement (p < 0.001). Subgroup analysis for tear size showed significant differences in the QuickDASH score (0.04). Particularly, a significant difference in the QuickDASH score could be detected between medium and large tears (p=0.008) as well as medium and massive lesions (p=0.04). No differences could be detected between large and massive tears (p= 0.35). Postoperative imaging showed healed tendons in 21 out of 29 (72%) cases. Preservation of tendon remnant combined with small bone vents in the repair of medium-to-massive full-thickness rotator cuff tears provided significant improvement in clinical outcome compared to baseline conditions with complete structural integrity in 72% of the cases

Tendon healing is a complex process that often results in compromised healing of the tendon tissue. It has recently been shown that temporal changes in the expression profile and the histological tissue quality of the tendons occur during the early healing process after acute Achilles tendon rupture. Whether these changes are accompanied by an altered healing process, is not yet known and was the aim of the present study. Tendon biopsies were obtained from 24 patients with acute Achilles tendon rupture at the time of surgery (2–9 days after rupture) and examined histologically as well as on RNA level. Histologically, the tendon architecture, the amount of aligned collagen, glycosaminoglycan and fat as well as the cellularity, vascularity and immune cell infiltration were determined. On RNA level the expression of markers for the modeling/remodeling (MMPs and TIMPs), collagens (1, 3, 5), tendon markers (scleraxis, tenomodulin), pro- and anti-inflammatory markers (IL-1beta, IL6, IL10, IL33, TNFa, TGF-beta1, COX2) and immune cell markers (CD3, CD68, CD80, CD206) were analyzed by Real-Time PCR. To determine the clinical outcome, the patients were followed up 12 months after the operation and the following scores were recorded: Subjective score, Tegner score, Visual Analog Scale (VAS) pain, VAS function, Matles Test, Achilles tendon total rupture score (ATRS), Therman 100-points score, Heel rise test. Statistics: Spearman correlation analysis. Correlation analysis shows that early post-rupture surgery is associated with better clinical outcome (ATRS Score: p=0.022). Histologically, a good functional healing outcome shows a positive correlation to the amount of aligned collagen (Heel Rise Test: p = 0.009) and glycosaminoglycans in the tendon (Heel Rise Test: p = 0.026, Matles difference: p = 0.029), as well as a negative correlation to the fat content (Thermann score: p = 0.018, subjective score: p = 0.027, VAS function: p = 0.031). On RNA level, a good healing outcome correlates with increased expression of MMP13, collagen 1, 3, 5 (Heel Rise Test: p = 0.019, p = 0.048, p = 0.030), and TIMP2 (Tegner Score: p = 0.040), TGF-beta1 (Thermann Score: p = 0.032) and CD80 (ATRS: p = 0.025, Thermann score:, p = 0.032). Whereas a limited healing outcome is associated with an increased expression of MMP2 (Heel Rise Test: p = 0.033), MMP3 (Matles Test: p=0.001, Heal Rise test p = 0.017), and IL33 (Tegner Score: p = 0.047). The results of the study show a clear relationship between the tendon biology at the time of the surgery and the clinical and functional healing outcome 12 months after the operation. Especially matrix formation and remodeling play a crucial role, while the examined immunological factors seem to influence the tendon healing to a lesser extent. The modulation of matrix formation could potentially lead to improved treatment options in the future

Tendon diseases are prevalent health concerns for which current therapies present limited success, in part due to the intrinsically low regenerative ability of tendons. Therefore, tissue engineering presents a potential to improve this outcome. Here, we hypothesize that a concurrent control over both biophysical and biochemical stimuli will boost the tenogenic commitment of stem cells, thus promoting regeneration. To achieve this, we combine molecularly imprinted nanoparticles (MINPs), which act as artificial amplifiers for endogenous growth factor (GF) activity, with bioinspired anisotropic hydrogels. 2. to manufacture 3D tenogenic constructs. MINPs were solid phase-imprinted using a TGF-β3 epitope as template and their affinity for the target was assessed by SPR and dot blot. Magnetically-responsive microfibers were produced by cryosectioning electrospun meshes containing iron oxide nanoparticles. The constructs were prepared by encapsulating adipose tissue-derived stem cells (ASCs), microfibers, and MINPs within gelatin hydrogels, while aligning the microfibers with an external magnetostatic field during gelation. This allows an effective modulation of hydrogel fibrillar topography, mimicking the native tissue's anisotropic architecture. Cell responses were analyzed by multiplex immunoassay, quantitative polymerase chain reaction, and immunocytochemistry. MINPs showed an affinity for the template comparable to monoclonal antibodies. Encapsulated ASCs acquired an elongated shape and predominant orientation along the alignment direction. Cellular studies revealed that combining MINPs with aligned microfibers increased TGF-β signaling via non-canonical Akt/ERK pathways and upregulated tendon-associated gene expression, contrasting with randomly oriented gels. Immunostaining of tendon-related proteins presented analogous outcomes, corroborating our hypothesis. Our results thus demonstrate that microstructural cues and biological signals synergistically direct stem cell fate commitment, suggesting that this strategy holds potential for improving tendon healing and might be adaptable for other biological tissues. The proposed concept highlights the GF-sequestering ability of MINPs which allows a cost-effective alternative to recombinant GF supplementation, potentially decreasing the translational costs of tissue engineering strategies. Acknowledgements: The authors acknowledge the funding from the European Union's Horizon 2020 under grant No. 772817; from FCT/MCTES for scholarships PD/BD/143039/2018 & COVID/BD/153025/2022 (S.P.B.T.), and PD/BD/129403/2017 (S.M.B.), co-financed by POCH and NORTE 2020, under the Portugal 2020 partnership agreement through the European Social Fund, for contract 2020.03410.CEECIND (R.M.A.D.) and project 2022.05526.PTDC; and from Xunta de Galicia for grant ED481B2019/025 (A.P.)

Unresolved inflammatory processes in tendon healing have been related to the progression of tendinopathies. Thus, the management of tendon injuries may rely on cell-based strategies to identify and modulate tendon inflammatory cues. Pulsed electromagnetic field (PEMF) has been approved by FDA for orthopedics therapies and has been related to a reduction in pain and to improve healing. However, the influence of PEMF in tendon healing remains largely unknown. Human tendon resident cells (hTDCs) were cultured in an inflammatory environment induced by exogenous supplementation of IL-1β and their response assessed after exposure to different PEMF treatments. This study demonstrates that IL-1β induced up-regulation of pro-inflammatory factors (IL-6 and TNFα) and extracellular matrix components (MMP−1, −2, −3) whereas reduces the expression of TIMP-1, suggesting IL-1β as a candidate inflammation model to study hTDCs response to inflammation cues. Moreover, in both homeostatic and inflammatory environments, hTDCs respond differently to PEMF treatment suggesting that cells are sensitive to magnetic field parameters such as strength (1.5 – 5mT), frequency (5–17Hz) and duration (10–50% duty cycle, dc). Among the conditions studied, PEMF treatment with 4mT/5Hz/50%dc suppresses the inflammatory response of hTDCs to the IL-1β stimulation, as evidenced by the decreases amount of IL-6, TNFα and downregulation of MMP-1, −2, −3 and COX-2, IL-8, IL-6, TNFα genes. These results demonstrate the potential of PEMF, in particular 4mT/5Hz/50%dc PEMF in treating tendon inflammation suppressing the inflammatory stimulation induced by IL-1β, which may be beneficial for tendon healing strategies

Rotator cuff repair has excellent clinical outcomes but continues to be a challenge when it comes to large and massive tears as well as revision procedures. Reported symptomatic retear rates are still too high to be acceptable. The purpose of the present study was to evaluate the effectiveness of a combination of augmentation techniques consisting of microfractures of the greater tuberosity, extracellular matrix (ECM) patch graft and subsequent platelet concentrate (PC) subacromial injections in revision rotator cuff repair. The study was designed as a retrospective comparative study on prospectively collected data from a consecutive cohort of patients. All patients who underwent arthroscopic revision rotator cuff repair for symptomatic failure of previous posterosuperior rotator cuff repair were considered eligible for the study. Symptomatic failure had been diagnosed according to clinical examination and confirmed by magnetic resonance imaging (MRI). Structural integrity had been assessed on MRI and classified according to Sugaya classification. Only patients affected by stage IV-V were considered eligible. Tear reparability was confirmed during arthroscopy. Only patients with a minimum 2 years follow-up were included. Patients were divided in two groups. In group 1 (control group) a standard arthroscopic revision and microfractures of the greater tuberosity were performed; in group 2 (experimental group), microfractures of the greater tuberosity and a ECM patch graft were used to enhance tendon repair, followed by postoperative PC injections. Minimum follow-up was 12 months. Primary outcome was the Constant-Murley score (CMS) normalized for age and gender. Subjective outcome was assessed with the Disabilities of the Arm, Shoulder and Hand (DASH) score in its short version (Quick-DASH). Tendon integrity was assessed with MRI at 6 months after surgery. Comparison between groups for all discrete variables at baseline and at follow-up was carried out with the Student's t-test for normally distributed data, otherwise Mann-Whitney U-test was used. Within-group differences (baseline vs follow-up) for discrete variables were analyzed by paired t-test, or by Wilcoxon signed-rank test in case of data with non-normal distribution. Differences for categorical variables were assessed by chi-squared test. Significance was considered for p values < 0.05. Forty patients were included in the study (20 patients for each group). The mean follow-up was 13 ± 1.6 months. No patients were lost at the follow up. Comparison between groups did not show significant differences for baseline characteristics. At follow-up, mean CMS was 80.7 ± 16.6 points in group 1 and 91.5 ± 11.5 points in group 2 (p= 0.022). Mean DASH score was 28.6 ± 21.6 points in group 1 and 20.1 ± 17.4 points in group 2 (p= 0.178). Post-operative MRI showed 6 healed shoulders in Group 1 and 16 healed shoulders in Group 2 (p<0.004). No postoperative complications were reported in both groups. The combination of microfractures of the greater tuberosity, ECM patch graft, and subsequent PC subacromial injections is an effective strategy in improving tendon healing rate

Stem cells represent an exciting biological therapy for the management of many musculoskeletal tissues that suffer degenerative disease and/or where the reparative process results in non-functional tissue (‘failed healing’). The original hypothesis was that implanted cells would differentiate into the target tissue cell type and synthesise new matrix. However, this has been little evidence that this happens in live animals compared to the laboratory, and more recent theories have focussed on the immunomodulatory effects via the release of paracrine factors that can still improve the outcome, especially since inflammation is now considered one of the central processes that drive poor tendon healing. Because of the initial ‘soft’ regulatory environment for the use of stem cells in domestic mammals, bone and fat-derived stem cells quickly established themselves as a useful treatment for naturally occurring musculoskeletal diseases in the horse more than 20 years ago (Smith, Korda et al. 2003). Since the tendinopathy in the horse has many similarities to human tendinopathy, we propose that the following challenges and, the lessons learnt, in this journey are highly relevant to the development of stem cells therapies for human tendinopathy:. Source – while MSCs can be recovered from many tissues, the predominant sources for autologous MSCs have been bone and fat. Other sources, including blood, amnion, synovium, and dental pulp have also been commercialised for allogenic treatments. Preparation – ex vivo culture requires transport from a licensed laboratory while ‘minimally manipulated’ preparations can be prepared patient-side. Cells also need a vehicle for transport and implantation. Delivery – transport of cells from the laboratory to the clinic for autologous ex vivo culture techniques; implantation technique (usually by ultrasound-guided injection to minimise damage to the cells (or, more rarely, incorporated into a scaffold). They can also be delivered by regional perfusion via venous or arterial routes. Retention – relatively poor although small numbers of cells do survive for at least 5 months. Immediate loss to the lungs if the cells are administered via vascular routes. Synovially administered cells do not engraft into tendon. Adverse effects – very safe although needle tracts often visible (but do not seen to adversely affect the outcome). Allogenic cells require careful characterisation for MHC Class II antigens to avoid anaphylaxis or reduced efficacy. Appropriate injuries to treat – requires a contained lesion when administered via intra-lesional injection. Intrasynovial tendon lesions are more often associated with surface defects and are therefore less appropriate for treatment. Earlier treatment appears to be more effective than delayed, when implantation by injection is more challenging. Efficacy - beneficial effects shown at both tissue and whole animal (clinical outcome) level in naturally-occurring equine tendinopathy using bone marrow-derived autologous MSCs Recent (licenced) allogenic MSC treatment has shown equivalent efficacy while intra-synovial administration of MSCs is ineffective for open intra-synovial tendon lesions. Regulatory hurdles – these have been lighter for veterinary treatments which has facilitated their development. There has been greater regulation of commercial allogenic MSC preparations which have required EMA marketing authorisation

Summary. We found an increased natural expression of the growth factors bFGF, BMP-12, VEGF, and TGF-b1 during tendon healing of rat Achilles tendons. External application of these growth factors improved the tendons failure load in the early healing phase. Introduction. Tendon ruptures recover slowly and the healing of injuries can be devastating. Growth factors are known to influence tendon healing. However, only little is understood about growth factors in a healing tendon. Aim of this study was to investigate the influence of growth factors on tendon healing of rats following their natural expression. Methods. The Achilles tendon of rats were transected and resutured. First the expression of bFGF, BMP-12, VEGF and TGF-b1 was assessed by immunohistochemical analysis 1 to 8 weeks after surgery. Second the maximal failure load of healed Achilles tendons was measured dependent on the external application of bFGF, TGF-b1 and BMP-12. Results. The natural expression of bFGF (p<0.05), BMP-12 (p<0.05), TGF-b1, and VEGF was highest 1 week after transection. VEGF expression persisted during the remaining period whereas bFGF and BMP-12 declined. TGF-b1 expression peaked again after 8 weeks. A combined application of bFGF, TGF-b1 and BMP-12 resulted in a 4fold greater load to failure after 1 week (p<0.05), whereas a sequential treatment of these growth factors increased the load to failure even 5.5fold (p<0.05). Conclusion. During natural tendon healing the growth factors bFGF, BMP-12, VEGF, and TGF-b1 are differentially expressed. Additional administration of the mentioned growth factors can improve the load to failure in the early healing phase of rat Achilles tendons

Objectives. The incidence of acute Achilles tendon rupture appears to be increasing. The aim of this study was to summarize various therapies for acute Achilles tendon rupture and discuss their relative merits. Methods. A PubMed search about the management of acute Achilles tendon rupture was performed. The search was open for original manuscripts and review papers limited to publication from January 2006 to July 2017. A total of 489 papers were identified initially and finally 323 articles were suitable for this review. Results. The treatments of acute Achilles tendon rupture include operative and nonoperative treatments. Operative treatments mainly consist of open repair, percutaneous repair, mini-open repair, and augmentative repair. Traditional open repair has lower re-rupture rates with higher risks of complications. Percutaneous repair and mini-open repair show similar re-rupture rates but lower overall complication rates when compared with open repair. Percutaneous repair requires vigilance against nerve damage. Functional rehabilitation combining protected weight-bearing and early controlled motion can effectively reduce re-rupture rates with satisfactory outcomes. Biological adjuncts help accelerating tendon healing by adhering rupture ends or releasing highly complex pools of signalling factors. Conclusion. The optimum treatment for complete rupture remains controversial. Both mini-open repair and functional protocols are attractive alternatives, while biotherapy is a potential future development. Cite this article: X. Yang, H. Meng, Q. Quan, J. Peng, S. Lu, A. Wang. Management of acute Achilles tendon ruptures: A review. Bone Joint Res 2018;7:561–569. DOI: 10.1302/2046-3758.710.BJR-2018-0004.R2

Introduction and Objective. Achilles tendon defect is difficult problem for orthopedic surgeon, and therefore the development of new treatments is desirable. Platelet-rich fibrin (PRF), dense fibrin scaffold composed of a fibrin matrix containing many growth factors, is recently used as regenerative medicine preparation. However, few data are available on the usefulness of PRF on Achilles tendon healing after injury. The objective of this study is to examine whether PRF promotes the healing of Achilles tendon defect in vivo and evaluated the effects of PRF on tenocytes in vitro. Materials and Methods. PRF were prepared from rats according to international guidelines on the literature. To create rat model for Achilles tendon defect, a 4-mm portion of the right Achilles tendon was completely resected, and PRF was placed into the gap in PRF group before sewing the gap with nylon sutures. To assess the histological healing of Achilles tendon defect, Bonar score was calculated using HE, Alcian-blue, and Picosirius-red staining section. Basso, Beattie, Bresnahan (BBB) score was used for the evaluation of motor functional recovery. Biomechanical properties including failure tensile load, ultimate tensile stress, breaking elongation, and elastic modulus were measured. We examined the effects of PRF on tenocytes isolated from rat Achilles tendon in vitro. The number of viable cells were measured by MTS assay, and immunostaining of ki-67 was used for detection of proliferative cells. Migration of tenocytes was evaluated by wound closure assay. Protein or gene expression level of extracellular matrix protein, such as collagen, were evaluated by immunoblotting, immunofluorescence, or PCR. Phosphorylation level of AKT, FGF receptor, or SMAD3 was determined by western blotting. Inhibitory experiments were performed using MK-2206 (AKT inhibitor), FIIN-2 (FGFR inhibitor), SB-431542 (TGF-B receptor inhibitor), or SIS3 (SMAD3 inhibitor). All p values presented are two-sided and p values < 0.05 were considered statistically significant. Results. In rat Achilles tendon defects, Bonar score was significantly improved in PRF group compared to control group. Collagen deposition at the site of Achilles tendon defect was observed earlier in PRF group. Consistent with the histological findings, BBB score was significantly improved in PRF group. PRF also significantly improved the biomechanical properties of injured Achilles tendon. Furthermore, proliferating tenocytes, labelled by ki-67 were significantly increased in PRF group. These data suggested PRF prompted the healing of Achilles tendon defect. Thus, we further examined the effects of PRF on tenocytes in vitro. PRF significantly increased the number of viable cells, the proliferative cells labelled by ki-67, and migratory ability. Furthermore, PRF significantly increased the protein expression levels of collagen-I, collagen-III, α-SMA, and tenascin-C in tenocytes. Next, we examined the signalling pathway associated with PRF-induced proliferation of tenocytes. PRF increased the phosphorylation level and induced nuclear translocation of AKT, known as key regulator of cell survival. PRF also induced the phosphorylation of FGF receptor. Inhibition of AKT or FGF-receptor completely suppressed the positive effects of PRF on tenocytes. Furthermore, we found that inhibition of FGF receptor partially suppressed the phosphorylation of AKT by PRF. Thus, PRF induced the proliferation of tenocytes via FGFR/AKT axis. We further evaluated the signalling pathway associated with PRF-induced expression of extracellular matrix. PRF increased the phosphorylation levels of SMAD3 and induced nuclear translocation of SMAD3. Furthermore, inhibition of TGF-B receptor or SMAD3 suppressed increased expression level of extracellular matrix by PRF. Thus, PRF increased expression level of extracellular matrix protein via TGF-BR/SMAD3 axis. Conclusions. PRF promotes tendon healing of the Achilles tendon defect and recovery of exercise performance and biomechanical properties. PRF increases the proliferation ability or protein expression level of extracellular matrix protein in tenocytes via FGFR/AKT or TGF-βR/SMAD3 axis, respectively

Objectives. Platelet-rich plasma (PRP) is being used increasingly often in the clinical setting to treat tendon-related pathologies. Yet the optimal PRP preparations to promote tendon healing in different patient populations are poorly defined. Here, we sought to determine whether increasing the concentration of platelet-derived proteins within a derivative of PRP, platelet lysate (PL), enhances tenocyte proliferation and migration in vitro, and whether the mitogenic properties of PL change with donor age. Methods. Concentrated PLs from both young (< 50 years) and aged (> 50 years) donors were prepared by exposing pooled PRP to a series of freeze-thaw cycles followed by dilution in plasma, and the levels of several platelet-derived proteins were measured using multiplex immunoassay technology. Human tenocytes were cultured with PLs to simulate a clinically relevant PRP treatment range, and cell growth and migration were assessed using DNA quantitation and gap closure assays, respectively. Results. Platelet-derived protein levels increased alongside higher PL concentrations, and PLs from both age groups improved tenocyte proliferation relative to control conditions. However, PLs from aged donors yielded a dose-response relationship in tenocyte behaviour, with higher PL concentrations resulting in increased tenocyte proliferation and migration. Conversely, no significant differences in tenocyte behaviour were detected when increasing the concentration of PLs from younger donors. Conclusion. Higher PL concentrations, when prepared from the PRP of aged but not young donors, were more effective than lower PL concentrations at promoting tenocyte proliferation and migration in vitro. Cite this article: D. R. Berger, C. J. Centeno, N. J. Steinmetz. Platelet lysates from aged donors promote human tenocyte proliferation and migration in a concentration-dependent manner. Bone Joint Res 2019;8:32–40. DOI: 10.1302/2046-3758.81.BJR-2018-0164.R1

We investigated the effect of Platelet Rich Plasma (PRP) in tendon healing. The aim was to assess the effect of an application of PRP on angiogenesis and immunohistochemical expression of TGF-b1 and IGF-I during tendon healing. We used a patellar tendon defect model after resecting its central portion. 48 skeletally mature New Zealand White rabbits were divided into the respective group and each group they were randomised into controls and PRP treated cases. The rabbits were sacrificed at weekly intevals and histological and immunohistological assessments were performed. The results showed a faster healing rate, increased vascularity, and higher expression of the growth factors in the PRP group. We conclude that the mixture of growth factors present in PRP gel improved the rate and quality of tendon healing

Thrombin has many biological properties similar to those of growth factors. In a previous study, we showed that thrombin improves healing of the rat tendo Achillis. Low molecular weight heparin (LMWH) inhibits the activity and the generation of thrombin. We therefore considered that LMWH at a thromboprophylactic dose might inhibit tendon repair. Transection of the tendo Achillis was carried out in 86 rats and the healing tested mechanically. Low molecular weight heparin (dalateparin) was either injected a few minutes before the operation and then given continuously with an osmotic mini pump for seven days, or given as one injection before the operation. In another experiment ,we gave LMWH or a placebo by injection twice daily. The anti-factor Xa activity was analysed. Continuous treatment with LMWH impaired tendon healing. After seven days, this treatment caused a 33% reduction in force at failure, a 20% reduction in stiffness and a 67% reduction in energy uptake. However, if injected twice daily, LMWH had no effect on tendon healing. Anti-factor Xa activity was increased by LMWH treatment, but was normal between intermittent injections. Low molecular weight heparin delays tendon repair if given continuously, but not if injected intermittently, probably because the anti-factor Xa activity between injections returns to normal, allowing sufficient thrombin stimulation for repair. These findings indicate the need for caution in the assessment of long-acting thrombin and factor Xa inhibitors

Previous studies have shown that Tnmd is important for tendon maturation and has key implications for the residing tendon stem/progenitor cells. The putative signaling in which Tnmd participates is just starting to be better understood (Dex et al. 2016). However, its exact functions during tendon healing process still remain elusive. Therefore, the aims of this study were to perform systematic review of the literature on Tnmd-related research and to investigate the role of Tnmd in early tendon healing by applying a tendon rupture model in Tnmd-deficient mice. First, we searched in the PubMed database for articles containing “tenomodulin” or its alternative names and abbreviations. After exclusion of papers only available in abstract form and foreign language, we grouped the remaining 128 full-text publications into four study types: 1) looking into functions of Tnmd; 2) using Tnmd as a tendon marker; 3) correlating Tnmd mutations to a variety of diseases; and 4) reviews. Following literature analysis, we carried out a pilot Achilles tendon injury model with Tnmd-knockout (KO) mouse strain. Adult Tnmd-KO (n = 8) and wild-type (WT) (n = 8) mice underwent unilateral surgery of Achilles tendon based on Palmes et al. 2002 and were compared at day 8 postoperatively by: 1) H&E staining for overall assessment; 2) immunohistochemical BrdU analysis for cell proliferation; and 3) Safranin O staining for endochondral formation. Our literature screen revealed that Tnmd has been strongly justified as the best tendon and ligament marker in more than 90 different studies. Moreover, in vivo and in vitro investigations have demonstrated its positive role on tendon cell proliferation and tissue functions. Our follow up surgical study showed a very different scar organization in Tnmd-KO with a clearly reduced cell density. BrdU analysis confirmed a lower number of proliferating cells in Tnmd-KO scar area. Interestingly, endochondral formation was not observed in the scar tissues in either of the genotypes at day 8. Taken together, we systematically summarized the current knowledge on Tnmd gene and highlighted several future research perspectives. Lack of studies on the role of Tnmd in tissue healing, motivated our pilot investigation on Achilles tendon rupture, which in turn suggested that loss of Tnmd results in inferior repair process

Ultrasound has been shown to have positive biological effects, including increased angiogenic, chondrogenic, and osteogenic activities. The aim of our study was to evaluate the evidence available in the scientific literature for the ultrasound treatment for tendon healing. To identify “best evidence” published research a computerized literature search of Medline, Cochrane, PEDro, IME, IBECS and ENFISPO. Keywords used to identify the study population and interventions were: ultrasound, low intensity pulsed ultrasound, physiotherapy, clinical trial, meta-analysis, practice guideline, randomized controlled trial, repair tendon and tendon healing. The scientific evidence of the group of selected documents were measured using the scale described by the US Preventive Task Force. The assignment of the evidence level to each study was evaluated independently by two reviewers without communication among them. To determine inter-rather reliability Kappa index it was used (K) with a value of CI of 95%. The study populations were 39 pertinent recovered documents. The findings suggest that therapeutic ultrasound can increase in collagen synthesis and enhance the maturation of collagen fibrils of repairing tendons. Researchers have reported that therapeutic ultrasound could facilitate tissue recovery and US with dosages between 0.125–3 W/cm2 have been used in the treatment of tendon ruptures reported an improvement in both strength and energy absorption capacity of repairing rabbit or rat tendons with 1-MHz continuous US. Best results were: continuous US at 1 MHz, 0.5w/cm2 starting from day 5 after injury, 20 treatment sessions, 4 mi each session. There is not a general consensus on the choice of parameters for US treatment and the evidence for efficacy of therapeutic. Limits of studies: The time needed to develop such an interface in humans was reported to be much longer than that reported in animal models. Continuous and low-intensity pulsed ultrasound was able to accelerate tendon healing and facilitating earlier physiotherapy

Purpose of the study: The objective of this study was to identify clinical and anatomic factors which could affect the outcome of tendon healing after arthroscopic repair of rotator cuff tears. Material and methods: This prospective cohort study included 122 patients who underwent arthroscopic treatment between May 1999 and September 2002. One hundred twelve patients (114 shoulders) were reviewed (93.4%). Mean age at surgery was 61 years. An arthroscan (78% of patients) or magnetic resonance imaging (MRI) were performed six months postoperatively. Mean follow-up was 24 months (range 13–46 months). Results: Rotator cuff tears healed completely in 64% of the shoulders (n=73) and partially in 7% (n=8). No healing was observed in 29% (n=33). The Constant score was 49.8 preoperatively and 82.4 at last follow-up (p< 0.0001). Cuff healing improved clinical outcome with a Constant score of 85 points versus 77, particularly for force, 14.5 points versus 10 without healing. Four factors were statistically predictive of tendon healing: duration from symptom onset to operation (24 months for healed tears versus 37 months, p< 0.05); age at cuff repair (81% healed tears in patients aged less than 50 years versus 50% for patients aged over 65 years, p< 0.002); sagittal extension of the rotator interval or extension to the upper third of the infrascapularis (45% healed tears versus 79% without anterior extension, p< 0.0001); fatty degeneration (69% of healed tears for Goutallier grade 0 versus 38% for grade 1 and 2, p< 0.01). Conclusion: This study demonstrated that four factors can predict tendon healing: time to treatment, age at surgery, anterior extension of the tear, fatty degeneration

Tendinopathy is a debilitating musculoskeletal condition which can cause significant pain and lead to complete rupture of the tendon, which often requires surgical repair. Due in part to the large spectrum of tendon pathologies, these disorders continue to be a clinical challenge. Animal models are often used in this field of research as they offer an attractive framework to examine the cascade of processes that occur throughout both tendon pathology and repair. This review discusses the structural, mechanical, and biological changes that occur throughout tendon pathology in animal models, as well as strategies for the improvement of tendon healing. Cite this article: Bone Joint Res 2014;3:193–202

Rotator cuff tendon healing has proven to be a substantial clinical challenge. There is significant interest in finding biologic augmentation methods to improve this healing process. Two currently available products include platelet rich plasma/platelet rich fibrin matrix and several commercially available extra cellular matrix (ECM) patches. Platelet rich plasma is a sample of an autologous blood which has been centrifuged to a concentration of platelets three to four times that of normal. Platelets contain multiple growth factors, many of which have been shown to be involved in all phases in tendon healing. An alternative is platelet rich fibrin matrix. This forms a fibrin matrix with the platelets embedded within. Growth factors are subsequently released as the fibrin is reabsorbed. There are only a few studies which look at the effectiveness of platelet rich plasma and fibrin matrix. Overall, there is no strong evidence to support its routine use in the setting of rotator cuff repair. Extra cellular matrix patches are used to reinforce the strength of the repair and offload the tendon. They also provide the potential to form a scaffold for new growth and differentiation and may at some point be a delivery vehicle for cells and growth factors. There are currently two prospective randomised studies evaluating ECM patches – one showed that the patch studied was actually harmful to repair and the second suggested there was some benefit in larger tears. While there is not a lot of strong evidence to support routine use, further research and development is necessary to maximise this strategy

Healing of tendons is sensitive to mechanical loading, and the callus strength is reduced by ¾ after 14 days, if loading is prevented. Exogenous GDFs stimulate tendon healing. This response is influenced by loading: without loading, cartilage and bone formation is initiated. This suggests that BMP signalling is crucial during tendon healing, and that it is influenced by mechanical loading. We investigated if mechanical loading influences BMP signalling in intact and healing tendons, and how BMP gene expression changes during healing. The Achilles tendon was transected in rats and left to heal. Half of the rats had one Achilles tendon unloaded by injection of Botox in the calf muscles. Ten tendons were analyzed before transection and for each of four time points. Gene expression for OP-1, GDF-5, -6, -7, Follistatin, Noggin, BMP-receptor 1b and BMP-receptor 2 were analysed with real-time PCR. Loading had no detectable effects on intact tendons. During repair, loading decreased follistatin by more than half (p=0.0001), and increased GDF-5 (p=0.02). All genes showed changes during repair (p=0.0001), but the time sequences differed. GDF-5 and GDF-7 were generally more expressed than OP-1 and GDF-6. GDF-5 and GDF-7 were more expressed in normal tendons than during repair. Noggin was never detected. Our results suggest that GDF-5 is specific for the mature tendon, and not much involved in repair. This contrasts to GDF-7, which is involved in both. OP-1 and GDF-6 seem to be involved in early healing. There was less expression of follistatin in loaded tendons during healing. The mechanosensitivity is likely of most importance at day 14 and 21 since the difference in strength between loaded and unloaded tendons is huge. An Anova with only these time points reveals effects of loading on GDF-5 and follistatin (p=0.0001 for both) and significant differences between the days for most variables

Purpose: Partial rotator cuff tears are a frequent source of shoulder pain. At times, diagnosis is difficult and treatment unsuccessful. Historical treatment has involved open debridement when conservative treatment has failed. The purpose of this study was to evaluate the results of arthroscopic treatment of deep partial thickness tears of the supraspinatus tendon in patients over 40 years and to assess the healing radiographically. Method: Forty-nine patients (mean age: 55 years) underwent treatment of a deep partial thickness tear of the supraspinatus tendon. Exclusion criteria: age < 40 years, associated instability, posterosuperior impingement or previous shoulder surgery. Patients were re-examined with a mean 32 months follow-up. For lesions involving less than 50% of the tendon thickness, an acromioplasty and either a debridement (n=39) or a side-to-side repair (n=3) was performed. For lesions involving greater than 50% of the tendon thickness (n=7), an acromioplasty and a trans-osseous repair was performed after completion of the tear. Twenty patients (41%) had an assessment of tendon healing by CT arthrogram, MRI or MR arthrogram, at a minimum 12 months post-operatively. Results: Results were good or excellent in 90% of patients, and 94% were satisfied. The Constant score improved from 56 to 82 points (p< 0.0001) and the UCLA score improved from 15 to 30 points (p< 0.0001). Of the 31 patients employed preoperatively, three did not return to work; an occupational injury was predictive of a lower Constant score (p=0.02). Four out of 13 (31%) cases involving less than 50% of the tendon thickness healed and all cases (n=7) involving greater than 50% had healed. Conclusion: Patients over 40 years with an isolated deep partial thickness tear of the supraspinatus tendon benefited both subjectively and objectively from arthroscopic intervention. For deep tears involving < 50% of the tendon thickness, resolution of pain and return to work is possible after acromioplasty and debridement. For deeper tears, completion of the tendon and reattachment to the greater tuberosity enables tendon healing

Background: Severe and chronic back pain often originates from degenerated intervertebral discs, probably from lesions in the outer posterior anulus. Unlike the nucleus, the outer anulus has a high cell density and adequate metabolite transport. The outer annulus can heal after injury in small and young experimental animals, but little is known about the healing potential of adult human discs. Purpose: We seek evidence that healing of the human outer anulus follows the three stages of tendon healing: inflammation, repair, remodelling. If so, then manual therapy and self-treatment techniques known to facilitate tendon healing could be adapted to treat discogenic back pain. Methods: Anulus tissue was removed at surgery (usually posteriorly) from 14 patients with discogenic back pain. Tissue was paraffin embedded and sectioned at 5 μm for histology and immunohistochemistry. Apoptosis was detected using an antibody for caspase-3. Results: Fissures in the peripheral posterior annulus, and herniated tissue fragments, were associated with blood vessels, inflammatory cells, and with focal loss of proteoglycans. Cell density decreased with distance from fissures from the disc periphery. Overall cell density decreased with age. Apoptosis was greater in the nucleus than in the annulus, and was particularly associated with cell clusters, and with anulus fissures. Conclusion: These preliminary results suggest an inflammatory healing response in the outer anulus, strongly associated with radial fissures. Loss of proteoglycan from fissure margins may facilitate the ingrowth of capillaries and nerves, which then stimulate local healing in the vicinity of the fissures. Conflicts of Interest: None. Source of Funding: BackCare

We investigated the effect of mitomycin-C on the reduction of the formation of peritendinous fibrous adhesions after tendon repair. In 20 Wistar albino rats the tendo Achillis was cut and repaired using a modified Kessler technique. The rats were divided into two equal groups. In group 1, an injection of mitomycin-C was placed between the tendon and skin of the right leg. In group 2, an identical volume of sterile normal saline was injected on the left side in a similar fashion. All the rats received mitomycin-C or saline for four weeks starting from the day of operation. The animals were killed after 30 days. The formation of peritendinous fibrous tissue, the inflammatory reaction and tendon healing were evaluated. The tensile strength of the repaired tendons was measured biomechanically. Microscopic evidence of the formation of adhesions and inflammation was less in group 1. There was no significant difference in the tensile load required to rupture the repaired tendons in the two groups. Mitomycin-C may therefore provide a simple and inexpensive means of preventing of post-operative adhesions

Rotator cuff tears are common in middle-aged and elderly patients. Despite advances in the surgical repair of rotator cuff tears, the rates of recurrent tear remain high. This may be due to the complexity of the tendons of the rotator cuff, which contributes to an inherently hostile healing environment. During the past 20 years, there has been an increased interest in the use of biologics to complement the healing environment in the shoulder, in order to improve rotator cuff healing and reduce the rate of recurrent tears. The aim of this review is to provide a summary of the current evidence for the use of forms of biological augmentation when repairing rotator cuff tears.

Cite this article: Bone Joint J 2024;106-B(9):978–985.

Purpose of the study: Posterior fracture-impaction of the humeral head (Hill-Sachs defect or Malgainge notch) is a well-known factor of failure for arthroscopic shoulder stabilisation procedures. Recently, Wolf proposed arthroscopic posterior capsulodesis and tenodesis of the infraspinatus, or what we call in French Hill-Sachs Remplissage (filling). We hypothesised that capsule and tendon healing within the bony defect could explain the efficacy of this arthroscopic technique. Material and methods: Prospective clinical study of a continuous series. Inclusion criteria:. recurrent anterior instability (dislocation or subluxation);. isolated “engaged” humeral defect;. Bankart arthroscopy and Hill-Sachs remplissage;. arthroCT or MRI at least 6 months after surgery. Exclusion criteria:. associated bone loss in the glenoid;. associated rotator cuff tear. Twenty shoulders (20 patients) met the inclusion and exclusion criteria and underwent Hill-Sachs remplissage. Four orthopaedic surgeons evaluated independently the soft tissue healing in the humeral defect. Mann-Whitney analysis was used to search for a link between rate of healing and clinical outcome. Results: Filling of the humeral defect reached 75 to 100% in 16 patients (80%°; it was 50–75% in 4 patients. Healing was never noted less than 50%. The short-term clinical outcome (mean follow-up 11.4 months, range 6–32) showed an excellent results as assessed by the Constant score (mean 92±8.9 points) and the Walch-Duplay score (91 points). The subjective shoulder value (SSV) was 50% preoperatively and 89% at last follow-up. There were no cases of recurrent instability. This study was unable to establish a relationship between minor healing and less favourable clinical outcome. Discussion: This study confirmed our hypothesis that arthroscopic Hill-Sachs remplissage provides a high rate of significant healing in a majority of patients. Capsule and tendon healing in the humeral defect yields significant shoulder stability via at least two mechanisms:. prevention of defect engagement on the anterior border of the glenoid and. posterior force via improved muscle and tendon balance in the horizontal plane. Further mid- and long-term results will be needed to establish a confirmed correlation between healing and clinical outcome

Summary. Silver nanoparticles improve the tensile property of the repaired Achilles tendon by modulating the synthesis and deposition of collagen. This makes silver nanoparticles a potential drug for tendon healing process with less undesirable side effect. Introduction. Tendon injury is a common injury that usually takes a long time to fully recover and often lead to problems of joint stiffness and re-rupture due to tissue adhesions and scarring on the repaired tendon respectively. Recently, it has been proven that silver nanoparticles (AgNPs) are capable of regenerating skin tissue with minimal scarring and comparable tensile property to normal skin. Hence, it is hypothesised that AgNPs could also improve the healing in tendon injury as both tissues are predominating with fibroblasts. The objective of this study is to look at the in vitro response of primary tenocytes to AgNPs and to investigate the mechanical and histological outcome in vivo. Methods and Materials. Primary tenocytes were harvested from 4 weeks old Sprague Dawley rat. 1.5×10. 4. cells per cm. 2. were seeded in triplicate for BrdU incorporation assay and Sirius red/ fast green staining to study the proliferation and collagen synthesis respectively. In vivo rat Achilles tendon injury model was used to investigate the effect of AgNPs to tendon regeneration. Briefly, the Achilles tendon was transected at 0.5cm from its insertion. The wound was either treated with 1mM AgNPs every 5 days or left untreated as the control. Skin incision was done without transecting the tendon in the sham group. The tendons were harvested on day 42 post operation. Tensile test and immunohistological staining on 7μm cryosections were performed to assess the mechanical property and biological events in healing respectively. SHG imaging was used to determine the collagen fibre orientation and abundance. Results. In vitro BrdU incorporation and Sirius red fast green assay suggested that AgNPs promoted the proliferation and collagen synthesis of tenocytes between 1 to 20μM and 10 to 20μM respectively. Tensile test on in vivo tissue showed that AgNPs-treated samples had significantly better tensile modulus compared to the untreated ones (p<0.05). SHG imaging suggested a better collagen alignment and density in AgNPs-treated samples. Immunohistochemistry demonstrated that AgNPs suppressed tumor necrosis factor (TNF α) whilst promoted fibromodulin (Fmod) and proliferating cell nucleus antigen (PCNA) expression. Discussion. Collagen is the major component that contributes to the tensile strength of a tendon. Its thickness, abundance and alignment directly affect the strength. In this study, it is found that AgNPs stimulate cell proliferation both in vitro and in vivo which is believed to be the reason of the increase in collagen synthesis. Fmod is an important proteoglycan responsible for collagen fibrillogenesis and TNF α is related to ECM degradation which directly affects collagen integrity. Stimulation of Fmod and alleviation of TNF α therefore promote collagen maturity and integrity which attributes to the improvement in the tensile property of the regenerated tissue. Furthermore, inflammation is known to relate to fibrosis and scarring in healing of many types of tissue. It is therefore postulated that the anti-inflammatory effect of AgNPs is one of the major reasons for this phenomenal healing of tendon. To conclude, this study demonstrates a positive effect of AgNPs to the early events of tendon healing which is important for accelerating the whole healing process and shortening of rehabilitation time

Summary Statement. A novel biomimetic polydioxanone tendon patch with woven and electrospun components is biocompatible, recapitulates native tendon architecture and creates a tissue-healing microenvironment directed by a subpopulation of regenerative macrophages. The woven component provides tensile strength while the tendon heals. Introduction. There is great interest in the use of biomimetic devices to augment tendon repairs. Ideally, implants improve healing without causing adverse local or systemic reactions. Biocompatibility remains a critical issue prior to implantation into humans, as some implants elicit a foreign body response (FBR) involving inflammation, poor wound healing and even fistulae formation. Additionally, the effect on articular cartilage locally or systemically with placement of a juxta-articular implant has not been examined. The purpose of this study is to test the in vivo biocompatibility of a novel hybrid woven and electrospun polydioxanone patch in a rat tendon transection model. Patients and Methods. Sixty Lewis rats were divided into 4 groups in which the infraspinatus was surgically transected 3 mm from its insertion. Tendons were repaired with a woven and electrospun polydioxanone patch (PDOe) and 5-0 Prolene sutures. Vicryl and Silk patches or a simple Prolene suture repair served as comparators. Animals were sacrificed at 1, 2, 4, 6 and 12 weeks to examine the biocompatibility of the implants. Immunohistochemistry was used to examine macrophage subpopulations and hematoxylin and eosin staining was used to assess foreign-body giant cells and both analyzed with a one-way ANOVA with significance set at p<.05. Articular cartilage was scrutinised with semi-quantitative analysis. Hind paw inflammatory indices were used to determine the systemic effects and biomechanical testing the tensile strength of the materials over time. Results. The PDOe patch remained grossly quiescent at all time-points. There was a severe inflammatory reaction to Vicryl at one and 2-week time-points with gross exudate. Silk patches were associated with larger fibrous capsules at each time point. There were no adverse systemic effects and articular cartilage remained normal with no differences between materials to controls. Immunohistochemistry showed a significantly higher ratio of regenerative to inflammatory macrophages for the PDOe patch compared to other constructs at each time-point and similar to controls. Silk and Vicryl patches had a greater than 10-fold increase in foreign-body giant cells compared to the PDOe patch and controls (p<.05) suggesting incorporation rather than rejection and walling off of the biomaterial. Tensile strength of the PDOe patch increased in the first 2 weeks to greater than 90 N and gradually declined to a mean of 22 N at 12 weeks. Discussion/Conclusion. The novel PDOe patch appears to be biocompatible and illicit very little FBR in this rat tendon injury model. Importantly, there was no joint reaction to the biomaterial which has not been addressed previously. We believe the electrospun component of the patch recapitulates native tendon architecture creating a tissue healing microenvironment directed by a regenerative macrophage subpopulation. These results corroborate earlier in vitro work that showed incorporation of tenocytes within the electrospun scaffold. The woven component of the scaffold provides tensile strength as the tendon heals and begins to degrade after healing is underway making it less likely to elicit a FBR. Based on these and earlier in vitro data we believe this implant shows excellent biocompatibility and is ready to proceed to human trials

There is a growing socio-economic need (i.e. “ageing society”) for effective and reproducible strategies to repair musculoskeletal tissue. In particular, acute tendon injury and chronic tendinopathies remain clinically challenging and novel treatment modalities are urgently needed. Tendons resemble a connective tissue rich in highly organized collagen fibers, displaying a remarkably high tensile strength. However, partly due to the low number of cells and their more or less avascular nature tendons heal relatively slowly. Ultimately, tendon regeneration encompasses the full restoration of the biological, biochemical and biomechanical properties, which are often impaired by endogenous healing cascades. Usually, a connective scar tissue forms at the injury site and the replaced tissue does not function adequately at high strain levels, increasing the chance of re-rupture. Despite significant advancements in tissue regeneration and engineering strategies, the clinical impact for the regeneration of tendon remains limited. For the development of novel methods to repair tendons we need to pin down the molecular and cellular mechanisms amenable to modulate endogenous (or exogenous) cell behaviour towards functional tissue regeneration. By comparing the gene expression profile of Achilles tendon tissue harvested from young-mature and old mice we demonstrate profound changes in the expression of ECM-related proteins and a previously unknown role of Secreted protein acidic and rich in cysteine (Sparc; also known as BM-40 or osteonectin) in tendons. Sparc levels in tendons are critical for proper collagen fibril maturation and its age-related decrease, together with a change in ECM properties potentially drives adipogenic differentiation of tendon stem and progenitor cells (TDSPCs) and consequently lipid accretion in tendons. Generally, the fate of stem/ progenitor cells is largely determined by stimuli from the stem cell niche. In tendons, we describe a novel cellular barrier, most likely preventing the leakage of blood-borne products into the tendon proper. We propose that this “blood-tendon barrier” is part of the stem cell niche in tendons controlling TDSCP fate, preventing erroneous differentiation. By investigating the developmental programs driving tendon tissue formation and on the other hand the mechanisms contributing to the senescence of tendons, ultimately resulting in decreased quality of tendons in the elderly, novel targets for clinical intervention potentially can be discovered

Aim: Experimentally forming a frayed Achilles tendon rupture model in rabbit and repairing the ruptured site with different methods; after the tendon healing, with the help of biomechanical and histopathological analyses, to find out which repair method is the most ideal. Material and Method: This study was carried out using 34 mature, female New Zealand type of rabbits with weights ranging 2200 to 2900 grams (2429,4 on average). The animals were divided into two groups named P and V, each with 17 rabbits. In each group, Achilles tendon on the right side was employed for the experiment (Pd and Vd) and the other side as a control (Pk and Vk). In the experiment groups, a frayed Achilles tendon rupture was performed. The control groups, however, received no procedures. After the primary repair, the Achilles tendons in the group Pd were augmented with the plantaris tendon. The Achilles tendons in the group Vd were primarily repaired after releasing gastrocnemius aponeurosis using “inverted-V” incision. In both groups, an above-knee cast was applied on the surgically procedured sides. After six weeks of observation, the repaired sites on tendons in the animals alive were analyzed biomechanically and histopathologically. 12 and 3 animals from each group were used respectively for the biomechanical and the histopathological analyses. Results: The elongation at tendon to rupture was 3,02±0,47 mm for Pd and 2,86±0,35 mm for Vd. The difference between two groups, however, was not statistically significant (p> 0,05). The maximum load at rupture for Pd was 105,88±38,14 N, and it was 71,95±17,44 N for Vd, thus the difference was statistically significant (p< 0,05). The energy needed to initiate a damage to the tendon was 0,1979±0,0902 J for Pd, and 0,1309±0,0368 J for Vd, the difference was also statistically significant (p< 0,05). The elongation, maximum load and energy values were lower in Pd group than in Pk, and in Vd group than in Vk, and the differences between each groups were statistically significant (p< 0,05). In histopathological sense, the tendon healing process in group Pd was faster than in group Vd. Conclusion: Although the repairs made with the augmentation of plantaris tendon yielded better results; the tendon, no matter which method is used, could not has its former strength. Results are bound to be better with stronger repair, and if the repair as much as supported by adjacent tendinous structures. Key Words: Achilles tendon, rupture, primary repair, m. plantaris, rabbit

Aims

To determine whether platelet-rich plasma (PRP) injection improves outcomes two years after acute Achilles tendon rupture.

Aims

The effects of remnant preservation on the anterior cruciate ligament (ACL) and its relationship with the tendon graft remain unclear. We hypothesized that the co-culture of remnant cells and bone marrow stromal cells (BMSCs) decreases apoptosis and enhances the activity of the hamstring tendons and tenocytes, thus aiding ACL reconstruction.

Introduction: Selective COX-2 (Cyclooxygenase-2) inhibitors have been found to impede fracture healing. The effect of selective COX-2 inhibitors on tendon healing in a bone tunnel, however, is unknown. Methods: The authors performed bilateral anterior cruciate ligament reconstructions in 32 rabbits and used peripheral quantitative computed tomography (pQCT) to compare tendon-to-bone healing between tunnel aperture and midtunnel regarding bone mineral density (BMD) and ingrowth of new bone. Each animal was assigned to one of four groups. Two groups received selective COX-2 inhibitors orally for 3 weeks (Cele-coxib; 10 mg/kg/d), the two other groups received no COX-2 inhibitors (controls). The animals were sacrificed 3 and 6 weeks after surgery. In biomechanical testing maximum load to failure and stiffness of the tendon grafts were calculated from the load displacement curve and failure modes were recorded. To assess indirectly the effect on local COX-2 activity the synovial content of Prostaglandin E2 (PGE2), the major metabolite of arachnidonic acid metabolism and catalyzed by COX-2, was measured by Enzyme-linked Immunosorbent Assay (ELISA). Results: Animals treated with selective COX-2 inhibitors had significantly lower BMD at the tunnel aperture (P=.02). In all groups the BMD at the tunnel aperture was significantly higher in comparison with the midtunnel (P< .05). In the controls ingrowth of new bone was greater at the tunnel aperture at 3 weeks (P=.028). After 3 weeks of COX-2 inhibitor administration synovial fluid concentrations of PGE2 were significantly lowered (P=.018) and increased more than threefold by 6 weeks after surgery and 3 weeks after last drug administration (P=.022), while in the controls there was a decrease in PGE2 between week 3 and 6. At 6 weeks the controls exhibited a twofold increase in maximum load to failure (3 weeeks: 28.2±20.9 N; 6 weeks: 59.6±53.6 N; P=.394), whereas the COX-2 inhibitor treated specimens decreased 1.9fold (3 weeks: 69.3±50.5 N; 6 weeks: 37.4±16.8 N; P=.24). Maximum load to failure values correlated with PGE2 changes, but not statistically significant (r. 2. = −0,502; p=0,056). Failure modes at 3 and 6 weeks were rupture and degloving, respectively, of the tendon graft. Discussion: This study revealed decreased bone mineral density at the tunnel aperture at 3 weeks, an increase of the inflammatory mediator PGE2 and decreased graft stability with time after treatment with selective COX-2 inhibitors. Untreated controls appeared to have a more physiological healing course with a continuous decrease in PGE2 and an increase in graft stability. Our results suggest, that selective COX-2 inhibitors may delay tendon healing in a bone tunnel

We performed a prospective ultrasonographic study of tendon healing following Ponseti-type Achilles tenotomy in 27 tendons (20 patients) with idiopathic congenital talipes equinovarus. Serial ultrasound examinations (both static and dynamic) were performed at 3, 6 and 12 weeks post-operatively. Casts were removed routinely 3 weeks post-tenotomy apart from two patients over 24 months of age who remained immobilised for 6 weeks. We observed three differing phases of healing apparent at 3, 6 and 12 weeks post tenotomy. We defined the end point of healing as the observation of tendon homogeneity across the gap zone on ultrasonography. This transition to normal ultra-structure was frequently seen by ultrasonography only at 12 weeks, when the divided ends of the tendon were indistinct. Though there is evidence of continuity of the tendon at the time of cast removal, it remains in the mid-phase of healing. The time taken for complete healing should be considered prior to planning a revision tenotomy. In two children over the age of 2 years, who had repeat tenotomy, the completion of healing by our criteria took longer than 12 weeks. The tendon gap healing does not appear to occur as readily in children over two years and other Methods: may be preferable to percutaneous tenotomy

Aims

The conventionally described mechanism of distal biceps tendon rupture (DBTR) is of a ‘considerable extension force suddenly applied to a resisting, actively flexed forearm’. This has been commonly paraphrased as an ‘eccentric contracture to a flexed elbow’. Both definitions have been frequently used in the literature with little objective analysis or citation. The aim of the present study was to use video footage of real time distal biceps ruptures to revisit and objectively define the mechanism of injury.

Aims

Myokine developmental endothelial locus-1 (DEL-1) has been documented to alleviate inflammation and endoplasmic reticulum (ER) stress in various cell types. However, the effects of DEL-1 on inflammation, ER stress, and apoptosis in tenocytes remain unclear.

The February 2023 Shoulder & Elbow Roundup³⁶⁰ looks at: Arthroscopic capsular release or manipulation under anaesthesia for frozen shoulder?; Distal biceps repair through a single incision?; Distal biceps tendon ruptures: diagnostic strategy through physical examination; Postoperative multimodal opioid-sparing protocol vs standard opioid prescribing after knee or shoulder arthroscopy: a randomized clinical trial; Graft healing is more important than graft technique in massive rotator cuff tear; Subscapularis tenotomy versus peel after anatomic shoulder arthroplasty; Previous rotator cuff repair increases the risk of revision surgery for periprosthetic joint infection after reverse shoulder arthroplasty; Conservative versus operative treatment of acromial and scapular spine fractures following reverse total shoulder arthroplasty.

Bone marrow concentrates are being used to augment soft tissue healing. However, only 0.01% of these cells meet the criteria of a mesenchymal stem cell (MSC), which likely accounts for the variability in reported results. Previous studies using an established rat rotator cuff repair model have demonstrated that bone marrow-derived MSCs had no effect on healing. In this study we evaluated the effect of purified human MSCs on rotator cuff healing in an athymic rat model. Hypothesis: Purified human MSCs added to the repair site will improve biomechanical strength and fibrocartilage formation of the healing tendon. Fifty-two athymic rats underwent unilateral detachment and repair of the supraspinatus tendon with either fibrin glue (control) or fibrin glue with 106 hMSCs (experimental) applied at the repair site. Flow cytometry verified the stem cell phenotype of the cells as CD73+, CD90+, CD105+, CD14-, CD34- and CD45-. Rats were sacrificed at 2 and 4 weeks, with 10 used for biomechanical testing and 3 for histologic analysis from each group. Biomechanical testing revealed a significant increase in failure load (11.5±2.4N vs. 8.5±2.4N, p=0.002) and stiffness (7.1±1.2 N/mm vs. 5.7±2.1 N/mm, p0.17). These data demonstrate the potential for stem cells to augment tendon healing. This is the first study to use purified stem cells, rather than simple bone marrow concentrate. In the future, cell sorting techniques and culture expansion could be used to select and expand the small population of true stem cells in bone marrow. Furthermore, healing could potentially be improved with repeat cell injection at an additional post-operative time point

The December 2022 Foot & Ankle Roundup³⁶⁰ looks at: Evans calcaneal osteotomy and multiplanar correction in flat foot deformity; Inflammatory biomarkers in tibialis posterior tendon dysfunction; Takedown of ankle fusions and conversion to total ankle arthroplasty; Surgical incision closure with three different materials; Absorbable sutures are not inferior to nonabsorbable sutures for tendo Achilles repair; Zadek’s osteotomy is a reliable technique for treating Haglund’s syndrome; How to best assess patient limitations after acute Achilles tendon injury; Advances in the management of infected nonunion of the foot and ankle.

Aims

To test the hypothesis that reseeded anterior cruciate ligament (ACL)-derived cells have a better ability to survive and integrate into tendon extracellular matrix (ECM) and accelerate the ligamentization process, compared to adipose-derived mesenchymal stem cells (ADMSCs).

Aims

Mechanical stimulation is a key factor in the development and healing of tendon-bone insertion. Treadmill training is an important rehabilitation treatment. This study aims to investigate the benefits of treadmill training initiated on postoperative day 7 for tendon-bone insertion healing.

Conventional non-steroidal anti-inflammatory drugs (NSAIDs) and newer specific cyclo-oxygenase-2 (cox-2) inhibitors are commonly used in musculoskeletal trauma and orthopaedic surgery to reduce the inflammatory response and pain. These drugs have been reported to impair bone metabolism. In reconstruction of the anterior cruciate ligament the hamstring tendons are mainly used as the graft of choice, and a prerequisite for good results is healing of the tendons in the bone tunnel. Many of these patients are routinely given NSAIDs or cox-2 inhibitors, although no studies have elucidated the effects of these drugs on tendon healing in the bone tunnel. In our study 60 female Wistar rats were randomly allocated into three groups of 20. One received parecoxib, one indometacin and one acted as a control. In all the rats the tendo-Achillis was released proximally from the calf muscles. It was then pulled through a drill hole in the distal tibia and sutured anteriorly. The rats were given parecoxib, indometacin or saline intraperitoneally twice daily for seven days. After 14 days the tendon/bone-tunnel interface was subjected to mechanical testing. Significantly lower maximum pull-out strength (p < 0.001), energy absorption (p < 0.001) and stiffness (p = 0.035) were found in rats given parecoxib and indometacin compared with the control group, most pronounced with parecoxib

Metabolic disorders are frequently associated with tendon degeneration and impaired healing after acute injury. However, the underlying cellular and molecular mechanisms remain largely unclear. We have previously shown that human and rat tendon cells responde to glucose stimulation in vitro by secretion of insulin. Therefore, we now hypothesize that nutritional glucose uptake affects tendon healing in a rat model. In female rats (n=30/group), unilateral full-thickness Achilles tendon defects were created. Immediately after surgery animals were either fed a glucose rich- or a control diet for up to 4 weeks. Gait analysis (Catwalk, Noldus) was performed at three time points. In addition, tendon thickness measurements, biomechanical testing and immunohistochemical analysis were conducted. Subsequently, gene expression analysis, comparing cDNA pools (n=5) prepared from repair tissues of both groups was performed. The repair tissues of the high glucose group were significantly thicker compared to the control group (p<0.001). The intermediate toe spread, an indicator of pain, were significantly improved in the high glucose group one and two weeks post surgery. Biomechanical analysis revealed that the repair tissues of the high glucose group were significantly stiffer (p<0.05) compared to the control group, no significant difference was detected for maximum tensile load…. The proportion of Ki67+ cells in the repair tissue was 3.3% in the control diet group and 9,8% in the high glucose group, indicating increased cell proliferation (p<0.001). Finally, gene expression analysis revealed the chondrogenic marker genes Collagen II, Aggrecan, COMP and SOX9 to be upregulated and genes involved in lipid metabolism like PPARgamma and Fabp2 to be downregulated in the glucose diet group. Here we show fort he first time that a high-glucose diet affects gait pattern and tendon biomechanics, influences tendon thickness and cell proliferation. Gene expression analysis reveals a regulation of chondrogenic as well as adipogenic marker genes. The molecular mechanisms underlying these effects on cells and extracellular matrix are currently under investigation, potentially revealing targets for developing a dietary intervention scheme to support tendon regeneration after trauma or tendon disease

Subscapularis repair and integrity after a primary total shoulder arthroplasty is critical for successful outcomes. One should be familiar with the 3 basic takedown and repair techniques commonly utilised. Subscapularis repair after reverse shoulder arthroplasty is not as critical and in some cases may be detrimental to return of external rotation strength and motion. Subscapularis tenotomy: The tendon is incised approximately 1 cm from the lesser tuberosity and an oblique incision is created from proximal lateral to distal medial stopping at the sentinel vessels. A combination of tendon-to-tendon figure of 8 sutures. Lesser tuberosity osteotomy: This approach is helpful not only in obtaining a bone-to-bone healing, but also in the exposure. Osteotomies range from a fleck of bone in patients with minimal deformity, to a C-shaped osteotomy including part of the head which facilitates exposure of the posterior glenoid. Despite an ability to document radiographic healing of the lesser tuberosity fragment, this technique does not prevent fatty infiltration of the subscapularis. Subscapularis Peel: This repair requires tendon healing to bone and probably incomplete, in most cases, reconstitution of a normal enthesis. External rotation can be gained by recessing the subscapularis insertion medially with the arm in external rotation. While bone-to-tendon sutures are the gold standard, augmentation of the sutures using a prosthesis as the anchor has led to the development of prostheses with multiple holes. Dual row repair of the tendon, however, may lead to medial rupture

An established rabbit model was used to preliminarily investigate the effect of acellular triphase, namely bone-cartilage-tendon, scaffold (ATS) sandwiched with autologous bone mesenchymal stem cells (BMSCs) sheets on tendon-bone interface healing. Bone, fibrocartilage and tendon tissue were harvested from the rabbits and sectioned into a book-type scaffold. The scaffolds were decellularized and their characterization was presented. BMSCs were isolated and co-cultured with the scaffolds to verify their cytocompatibility. BMSCs sheets were fabricated and inserted into the book page of the scaffold to construct an autologous BMSCs-sheets/book-type ATS complex. The complex was implated in the right knee of rabbits which operated standard partial patellectomy for TBI regeneration using Imaging, histological and biomechanical examinations. The bone, fibrocartilage and tendon tissue were sectioned into a book-type scaffold before decellularization. Then we decellularized the above tissue and mostly preserved their microstructure and composition of the natural extracellular matrix, including collagen and proteoglycan. After the physicochemical and biological properties of the book-type ATS were evaluated, autologous BMSCs sheets were inserted into the book page of the scaffold to construct an autologous BMSCs-sheets/book-type ATS implants for TBI regeneration. In addition, the ATS has the advantages of non-toxicity, suitable for cell adhesion and growth as well as low immunogenicity while co-cultured with the BMSCs. At the same time, different scaffolds has the ability to induce the osteogenic, chondrogenic and tenogenic differentiation of BMSCs by immunofluorescence, reverse transcription-polymerase chain reaction and western blot analysis. To determine the efficacy of the tissue-engineered implants for TBI regeneration, we transplanted it into a rabbit patella-patellar tendon (PPT) injury model, and the rabbits were sacrificed at postoperative week 8 or 16 for the radiological, histological, and mechanical evaluation. Radiologically, Synchrotron radiation micro-computed tomography (SR-μCT) showed that BMSCs/ATS group significantly increased bone area, BV/TV, trabecular thickness and trabecular number at the healing interface as compared with other groups at postoperative week 8 or 16. Histologically, the BMSCs/ATS group showed more woven bone, and a more robust fibrocartilaginous junction with a characteristic matrix rich in proteoglycans was seen at the PPT healing interface in comparison with other groups after 8 weeks. At week 16, the healing interface in 3 groups displayed better remodeling with respect to postoperative week 8. Healing and remodeling at the PPT junction were almost complete, with a resemblance to a healthy BTI consisting of the characteristic 4 zones in all groups. At last, we used biomechanical test as functional parameters to evaluate the quality of tendon-bone healing. Biomechanical testing indicated that BMSCs/ATS group showed significantly higher failure load and stiffness than other groups at postoperative week 8 and 16. The complex composed of acellular triphase, namely bone-cartilage-tendon, scaffold (ATS) sandwiched with autologous bone mesenchymal stem cells (BMSCs) sheets can simulate the gradient structure of tendon-bone interface, inducing stem cell directional differentiation, so as to promote patella-patellar tendon interface healing effectively after injury

Treatment of massive rotator cuff tears can be challenging. Previous studies with irreparable rotator cuff tears showed good clinical results of tendon healing with the arthroscopic insertion of a protective biodegradable spacer balloon filled with saline solution between the repaired tendon and the acromion [1,2], but so far no scientific evidence has showed how the device alters pressures over the repaired tendon. This biomechanical study investigated the effects of a spacer inserted in the subacromial space on pressures over the repaired rotator cuff tendon in passive motion cycles typical for post-operative rehabilitation routines. Six human cadaveric shoulders were prepared with the humerus cut 15cm below the joint and embedded in a pot, while the scapula fixed at three points on a plate. A rotator cuff tear was simulated and repaired using a suture anchor and a Mason-Allen suture. The specimens were then mounted on a custom-made pneumatic testing rig to induce passive motion cycles of adduction-abduction (90–0°) and flexion-extension (0–40°) with constant glenohumeral and superior loads and tension is exerted on the supraspinatus tendon with weights. A pressure sensor was placed between the supraspinatus tendon and the acromion. After pressure measurements for 15 cycles of each motion type, the InSpace balloon (OrthoSpace, Inc, Israel) was inserted and the specimens tested and pressure measured again for 15 cycles. Statistically significant changes in peak pressures were then measured before and after balloon. Peak pressures were measured near 90 degrees abduction. No statistical differences were observed for internal-external rotation before and after balloon-shaped subacromial spacer was inserted. Mean pressures in abduction-adduction were significantly reduced from 121.7 ± 9.5 MPa to 51.5 ± 1.2 MPa. Peak pressures after repair were 1171.3 ± 99.5 MPa and 1749.6 ± 80.7 MPa in flexion-extension and abduction-adduction motion, respectively, and significantly decreased to 468.7 ± 16.0 MPa and 535.1 ± 27.6 MPa after spacer insertion (p<0.0001). The use of the spacer above the repaired tendon reduced peak pressures and distributed them more widely over the sensor during both abduction-adduction and flexion-extension motions and therefore can reduce the stress on the rotator cuff repair. The InSpace system may reduce the pressure on the repaired tendon, thus potentially protecting the repair. Further studies to investigate this phenomenon are warranted, in particular relating these changes to shoulder kinematics following tear repair and spacer insertion

Rotator cuff repair is performed to treat shoulder pain and disability. Failure of the tendon repair site is common; one strategy to improve healing is to enforce a period of post-operative immobilisation. Immobilisation may have unintended effects on tendon healing. Tenocytes under uniaxial strain form more organised collagen and up regulate expression of proliferative genes. Vitamin C (ascorbic acid), an anti-oxidant that is a co-factor for collagen synthesis, has also been reported to enhance collagen deposition and organisation. The purpose of this study was to compare human tenocyte cultures exposed to uniaxial cyclical strain with or without slow-release ascorbic acid (ascorbyl-2 phosphate) to determine their individual and combined effects on tissue remodelling and expression of tissue repair genes. Rotator cuff tissues were collected from degenerative supraspinatus tears from eight patients. Tenocytes were incorporated into 3D type I collagen culture matrices. Cultures were divided into four groups: 1) ascorbic acid (0.6mMol/L) + strain (1%–20% uniaxial cyclic strain at 0.1 Hz), 2) ascorbic acid unstrained, 3) strain + vehicle 4) unstrained + vehicle. Samples were fixed in paraffin, stained with picrosirius red and analysed with circular polarising light. A second set of cultures were divided into three groups: 1) 0.5mM ascorbic acid, 2) 1mM ascorbic acid, 3) vehicle cultured for 24, 72, 120 and 168 hours. Cell-free collagen matrix was used as a control. Tenocyte proliferation was assessed using the water soluble tetrazolium-1 (WST1) assay and f tissue repair gene expression (TGFB1, COL1A1, FN1, COLIII, IGF2, MMP1, and MMP13), were analysed by qPCR. The data were analysed using a Split model ANOVA with contrast and bonferroni correction and a one-way ANOVAs and Tukey's test (p<0.05 was significant). Our results indicated that unstrained cultures with or without exposure to slow release ascorbic acid exhibited greater picrosirius red birifringency and an increase in collagen fiber deposition in a longitudinal orientation compared to strained tenocytes. We found that slow release ascorbic acid promoted significant dose and culture-time dependent increases in tenocyte proliferation (p<0.05) but no obvious enhancement in collagen deposition was evident over cultures without ascorbic acid supplementation. Based on these data, applying strain to tenocytes may result in less organised formation of collagen fibers, suggestive of fibrotic tissue, rather than tendon remodelling. This may indicate that a short period of immobilisation post-rotator cuff repair is beneficial for the healing of tendons. Exposure to slow release ascorbic acid enhanced tenocyte proliferation, suggesting that supplementation with Vitamin C may improve tendon repair post-injury or repair. Future studies will assess levels of tissue repair-associated proteins as well as comparing traumatic and degenerative rotator cuff tears to healthy uninjured rotator cuff tissue

Introduction. Achilles tendinopathy (AT) is a highly prevalent injury in athletes and non-athletes with an unknown aetiology. Genetic risk factors have been a recent focus of investigation. The aim of this systematic review was to determine which loci have been linked with mid-portion AT and could potentially be used as biomarkers in tendinopathy risk models or as preventative or therapeutic targets. Materials and Methods. Eight electronic bibliographic databases were searched from inception to April 2015 for cross-sectional, prospective cohort and case-control studies that included empirical research investigating genes associated with mid-portion AT. Potential publications were assessed by two independent reviewers (AAC and PRJ) for inclusion and quality. Quality was evaluated using a validated scale. Results. Twelve candidate gene studies and three pathway-based genetic association studies that investigated genetic risk factors for AT were identified. According to Ariëns's criteria, there was strong evidence for the COL5A1 gene. There was some evidence for 6 of the other genes investigated: COL5A3, TNC, CASP8, MIR608, GDF5, MMP3 and TIMP2 genes. There was inconclusive evidence for the following genes: COL3A1, COL5A2, COL11A1, COL11A2, COL12A1, COL1A1, COL27A1, COL14A1, COMP, THBS2, ADAMTS2, ADAMTS5, ADAMTS14, ADAM12, TGFβ1, IL-1β, IL-1RN, IL-6, NOS2 and NOS3. There was some evidence for combinations of functional variants of different genes and pseudohaplotypes constructed from many functional variants. The quality of included studies varied (3/9 to 7/9), and the average quality assessment score was 5.5/9 (61%). Discussion. There are genetic differences between subjects with and without AT. To further elucidate these findings, prospective studies are needed to investigate the increased risk associated with specific genetic findings. Modifying training loads or preventative exercise may be used to mitigate increased risk, although it needs to be highlighted that a genetic association does not necessarily mean an individual will develop Achilles tendinopathy. Gene therapy may have a role in tendon healing, but further research is necessary to develop risk models and establish the most advantageous genes to transfer

Introduction. Tendon healing begins with inflammation and results in an incomplete repair with fibrosis, culminating in tendon pathology along with tissue degeneration. Inflammatory mediators regulate the expression of growth factors, and members of the TGFβ superfamily including BMPs have been suggested to play a key role in the development of fibrosis. In established tendon diseases where inflammation and reparative processes persists, the cellular phenotype of tendon cells has been implied to undergo a transformation from that of normal tissue. This study investigates the inflammation-driven mechanisms of tendon pathology using an in vitro tendon cell model. We hypothesized that cells from diseased tendons will exhibit dysregulation of TGFβ superfamily members in response to inflammatory mediators when compared to cells derived from healthy tendons. Materials and Methods. Diseased human tendon cells were isolated from patients with large to massive rotator cuff tears (n=4). Cells isolated from healthy human hamstring tendons served as control tissue (n=5). Cells were treated with human recombinant IL-1β (5ng/ml), oncostatin M (10ng/ml), IL-6 (10ng/ml), IL-10 (10ng/ml) in serum-free medium, or serum-free medium alone (control) for 24 hours. Cell viability was monitored by Alamar Blue assay, and expression of TGFB1, TGFBR1, TGFBR2, CTGF, BMP2 and BMP7 were quantified by quantitative reverse transcription polymerase chain reaction (RT-QPCR). Results. Cytokine stimulation did not significantly influence cell viability in either group. In diseased cells, IL-1β induced a 4.9-fold increase in BMP2 compared to control cells (p=0.032). There were no significant changes in the expression of other TGFβ superfamily genes after stimulation with other cytokines. CTGF was significantly increased in diseased compared to healthy cells following IL-1β stimulation (p=0.0295). No other genes showed differential regulation by inflammatory cytokines between diseased and healthy cells. Discussion. This work suggests that BMP-2, a growth factor related to cell differentiation, is dysregulated with IL-1β stimulation and plays a key role in the development of tendon diseases. Differences in IL-1β-induced CTGF expression suggests increased responsiveness of diseased cells to this cytokine. BMP-2 could be an important growth factor in the development of tendon diseases and further investigation of its role in chronic inflamed tissue is warranted

Introduction. Metabolic disorders are among known risk factors for tendinopathies or spontaneous tendon ruptures. However, the underlying cellular and molecular mechanisms remain unclear. We have previously shown that human and rat tendon cells produce and secrete insulin upon glucose stimulation. Therefore, we hypothesize that nutritional glucose uptake affects tendon healing in a rat model. Materials and Methods. Unilateral full-thickness Achilles tendon defects were created in 60 female rats. Animals were randomly assigned to three groups receiving different diets for 2 weeks (high glucose diet, low glucose/high fat diet, control diet). Gait analysis was performed at three time points (n=20/group). In addition, tendon thickness, biomechanical (n=14/group), and histological and immunohistochemical analysis was conducted. Subsequently, a subtractive-suppression-hybridization (SSH) screen comparing cDNA pools (n=5) prepared from repair tissues of the high glucose and the control diet group was conducted to identify differentially expressed genes. Results. Newly formed repair tissue of the high-glucose and high-fat group was significantly thicker compared to the control group (p<0.001). Gait analysis revealed a significantly increased Intermediate Toe Spread for animals receiving high glucose diet one week p.o. compared to the control and high fat diet group (p<0.01). Maximum tensile load was significantly reduced in the control diet and the fat diet group, compared to intact tendons (p<0.05). Interestingly, there was no reduction evident for the glucose diet group. A similar trend was observed for tendon stiffness, with glucose diet repair tissue being significantly stiffer compared to the control diet (p<0.05). The proportion of Ki67+ cells in the repair tissue was 3,3% in the control, 9,8% in the glucose and 8,4% in the fat diet group, indicating an increased cell proliferation rate for the glucose and fat diet groups (p<0.001). Finally, the SSH screen revealed 48 candidate genes to be differentially expressed among the diet groups. Discussion. Tendon repair tissue quality is moderately affected by nutritional glucose. The molecular mechanisms underlying these effects on cells and matrix are currently under investigation and may be helpful in developing a dietary intervention scheme to support tendon regeneration after trauma or tendon disease

Introduction. Adult tendon injuries occur very frequently, but injured tendon heals very slowly and the mechanisms of the slow-healing response to injury are still largely unknown. Currently, the main barrier is our insufficient understanding of the mechanisms responsible for homeostasis, regeneration and repair of adult tendon. This gap in knowledge translates to a lack of experimental models. Therefore, using the combination of state-of-the-art genetic approaches, we have established novel cell biological tools to advance the understanding of tendon biology. Materials and Methods. Adult mouse tendon progenitor lines and Adult mouse tenocyte lines: Primary adult tenocytes were isolated from Achilles tendon in Scleraxis(fl/fl)/Scleraxis-GFP/p21(−/−) mice, then CD90.2- and subsequent Sca1-positive cells were sorted by Flow Cytometry. Then Scleraxis-null progenitor lines were generated by the treatment of those cells with adenovirus-Cre. Adult Scleraxis(+/+) and Scleraxis-null tenocyte lines were also generated from Scleraxis(fl/fl)/Scleraxis-GFP/p21(−/−) mice. To establish Scleraxis-Flag overexpressing tenocyte lines, Scleraxis and Flag-tag fusion-protein expression construct was generated and transfected into Scleraxis-null tenocytes (Scleraxis transgenic mouse strains were provided by Dr Ronen Schweitzer). Scleraxis antibody: DNA coding mouse Scleraxis residues were obtained by PCR, then the recombinant protein was expressed, immunized in rabbits, and an affinity-purified antibody was generated. Results. Established parental progenitor lines highly expressed Sca1 (98.9%), CD90.2 (97.3%), and CD44 (99.8%) and were almost negative for ScxGFP (2.3%). Interestingly, Scleraxis-null progenitors showed significantly increased clonogenicity. Furthermore, when stimulated toward mesenchymal lineages, Scleraxis-null progenitors enhanced differentiation into chondrocytes. Our Scleraxis antibody reacted with lysates from cells expressing Scleraxis-Flag fusion proteins (∼30 kDa), whereas it did not react with Scleraxis-null cells by Western analysis. Immunofluorescence analysis of adult mouse Achilles tendons further confirmed intense Scleraxis protein expression in wild-type tenocytes, whereas considerably decreased expression of Scleraxis was evident in Cre-treated Scleraxis(fl/fl) tenocytes. Discussion. These novel tools will be the promising resources to get an insight into molecular framework for Scleraxis in adult tendons. It is anticipated that the establishment of experimental models using these resources will fill major gaps in the current knowledge of adult tendon biology and will facilitate development of novel strategies to treat adult tendon injury

Purpose. Glenoid version has been correlated with tears within the rotator cuff. Cuff tear arthropathy is an evolution of multiple unhealed tendons ultimately resulting in pseudoparalysis. Although several factors are critical to allow tendon healing, we have observed that there is less glenoid version in patients with cuff tear arthropathy. This was compared to those with osteoarthritis where rotator cuff tears are uncommon. We hypothesize that patients undergoing inverse prosthesis generally have a near neutral glenoid. Method. A single surgeons practice (JPW) was retrospectively reviewed for all cuff tear arthropathy and osteoarthritis patients undergoing primary shoulder arthroplasty. (Zimmer, Warsaw, IN). Glenoid version was measured by 2 fellowship trained shoulder surgeons. Inter and intra-class correlation was measured. Results. The axial CT scans of 84 patients (cuff tear arthropathy and osteoarthritis) were evaluated. Inter and intra-class correlation was excellent (0.96, 0.97). Glenoid version was between 4.1 +/− 3.6 and 16.5 +/− 8.6 degrees for cuff tear arthropathy and osteoarthritis, respectively (p < 0.0001). Conclusion. Our observation of near neutral glenoid version in patients with cuff tear arthropathy has not been reported in the literature. The anatomical version of the glenoid may be a risk factor in patients undergoing rotator cuff repair. This may predispose certain individuals to cuff tear arthropathy compared to those with increased retroversion

Two views of tendon healing’s capability have prevailed since the early 1940’s. This presentation will outline the change in perspective regarding the primary tendon repair potential of intrasynovial flexor tendons and the clinical innovations that have been devised to reduce the inflammatory response and to improve the functional and structural characteristics of repair. Specifically, advanced suture, rehabilitation, and salvage techniques for tendon injuries will be discussed

Purpose of the study: Platelet rich fibrin (PRF) favours proliferation of tenocytes and synthesis of extracellular matrix. The purpose of this study was to demonstrate the technical feasibility of adding a PRF envelope during arthroscopic rotator cuff repair to favour short-term vascularisation of the tendon-trochiter zone vascularization. Material and method: Twenty patients aged over 55 years with a posterosuperior rotator cuff tear were included in this prospective randomized controlled study. The double strand technique was used for all patients. Patients were selected at random for insertion of a PRF envelope between the tendon and the trochiter. There were thus two groups of ten patients. The SSV, SST, VAS and Constant scores were noted. Vascularization was assessed with Power Doppler ultrasound at 6 weeks and 3 months by an independent operator unaware of the study group. Results: There were no complications during or after the operations. Postoperatively, all patients increased their SSV, SST, VAS and Constant scores significantly. Vascularization of the tendon-trochiter zone, as assessed by Power Doppler, was significantly higher in the PRF group at 6 weeks. It was unchanged in the two groups at 3 months. Discussion: Arthroscopic rotator cuff repair with adjunction of a PRF envelope is technically feasible and increases vascularizaton of the tendon-trochiter zone at 6 weeks. Conclusion: PRF can improve the tendon healing rate for rotator cuff tears

Summary Statement. The peripheral neuronal phenotype is significantly altered in rotator cuff tendinopathy (RCT) with a clear upregulation of the Glutaminergic system being present in disease. Introduction. Shoulder pain is the third most frequent cause of chronic musculoskeletal pain in the community and is usually caused by rotator cuff tendinopathy (RCT). The central and peripheral nervous system play an important role in both tissue homoeostasis and tendon healing. The Glutaminergic system is of key importance in driving the peripheral and central neuronal changes which increase the body's sensitivity to pain (1, 2). No study to date has investigated the role of the glutaminergic system in human RCT. We hypothesised that the peripheral neuronal phenotype would be altered in RCT, and would vary according to disease stage as measured by size of tear. The term ‘peripheral neuronal phenotype’ is used to refer to refer to specific characteristics of the peripheral nervous system, neuronal mediators and the receptors for these mediators in peripheral tissue. Methods. Rotator cuff tendon specimens were obtained from 64 patients undergoing the surgical repair of rotator cuff tears. Control supraspinatus tendon was obtained from 10 patients undergoing surgery for anterior instability using an ultrasound guided biopsy technique. Patients with rotator cuff tears were divided into 2 groups: the small/medium group (≤ 3cm size) and the large/massive group (>3cm size). The tendon tissue was histologically stained using Haematoxylin and Eosin, and immunohistochemically stained with primary antibodies visualised using 3, 3′-diaminobenzidine (DAB). Image analysis was performed blindly by 2 observers using Image-J to quantify the amount of DAB positive staining. Data was non-parametric in distribution and Mann-Whitney U tests were carried out using SPSS with significance levels set at a minimum of p<0.025. Results. There were significant changes in the peripheral neuronal phenotype in RCT. The Glutaminergic system was significantly up-regulated with an increase in Glutamate and changes in several related receptors in disease versus control (p<0.01). The standard deviation in nuclei count and mean cell nuclear area were both increased in disease (p<0.01) compared to controls. Tendon vascularity and cell proliferation were reduced in disease vs control (p<0.01). There were no significant correlations between pain scores and the peripheral tissue markers. Discussion/Conclusion. The peripheral neuronal phenotype is significantly altered in rotator cuff tendinopathy (RCT) with clear changes in the Glutaminergic system in disease. These findings are novel and improve our understanding of pain and tissue healing in RCT, potentially providing novel therapeutic targets

Intra-synovial tendon injuries affect compressed tendon within a synovial environment (eg Rotator cuff tears of the shoulder) and frequently demonstrate ‘failed healing'. Current therapeutic methods for tendon tears (intra-synovial corticosteroid medication and surgical debridement) offer poor outcomes and new strategies for enhancing repair are needed. We have therefore evaluated two different approaches involving the use of mesenchymal stem cells and scaffolds. Bone marrow- and synovial-derived stem cells were capable of adhering to cut surfaces of tendon in vitro and modulating the release of extracellular matrix into the media. However, when administered in vivo into the digital flexor tendon sheath in naturally-occurring deep digital flexor tendon tears in horses and in an experimental model in sheep, neither cell type was capable of healing the tendon defect. Superparamagnetic iron oxide particle labelling of the implanted cells imaged using MRI and histologically revealed that cells only engraft into the synovium. In contrast a non-cellularised bilayered electrospun and woven polydioxanone scaffold, when used in the same experimental sheep model via a modified open approach and sutured over the created defect resulted in no local or systemic signs of excessive inflammation 3 months after implantation. All the tendon lesions healed with only a mild local inflammatory reaction and minimal-to-mild adhesion formation. Significant proliferative fibroblast infiltration was observed within and immediately adjacent to the implanted scaffold. The cellular infiltrate was accompanied by an extensive network of new blood vessel formation within the new tissue. In conclusion, the use of a scaffold to cover the defect appears to be a more successful strategy to repair intra-synovial tendon defects than intra-synovially injected mesenchymal stem cells. It remains to be tested whether the combination of the two techniques might offer an even better healing response

The effects of extracorporeal shock waves (ESWT) on tendon healing were assessed by observing histological and biomechanical parameters in a rat model of injury to the tendo Achillis. The injury was created by inserting an 18-G needle through tendo Achillis in 48 adult Wistar albino rats. The animals were divided into three groups. The first group received radiation only after the operation. The second received no shock waves and the third had 500 15 KV shocks on the second post-operative day. All the rats were killed on the 21st day after surgery. Histopathological analysis showed an increase in the number of capillaries and less formation of adhesions in the study group compared with the control group (p = 0.03). A significantly greater force was required to rupture the tendon in the study group (p = 0.028). Our findings suggest a basis for clinical trials using ESWT

Summary Statement. The aim of this study was to compare patterns (aligned, random and grid) of electrospun polydioxanone scaffolds for tendon repair. The aligned design was optimal, directing cell shape, orientation and protein expression. Moreover, it naturally crimped, presenting tendon-like morphology. Introduction. Nanofibrous electrospun materials have been previously proposed as potential scaffolds for tendon repair, with emphasis on biomimetic design, postulated to encourage tissue regeneration. In this study, we characterised the interaction of primary tendon-derived cells with polydioxanone (PDO) scaffolds. PDO is a polymer with an excellent in vitro and in vivo biocompatibility, and is specifically compatible with tendon-derived cells. Here, we designed electrospun PDO scaffolds with different fibre orientations, namely aligned, random and grid-like patterns. To evaluate their potential as patches for tendon repair, we grew primary tendon derived cells on these scaffolds, and tested different aspects of cell behavior, including cell shape, proliferation and protein expression. Methods. Scaffolds with different orientations were produced using a single nozzle electrospinning set-up. Human tendon cells were extracted from rotator cuff tissue resected during surgical repair, with appropriate ethical approval. Cells were grown on different scaffolds for at least 14 days. Multiphoton microscopy (MPM) was used to image cells (green, calcein AM, and red, actin-phalloidin). Cell growth was monitored using AlamarBlue assay. Cell length, width and orientation were manually measured from images acquired by fluorescence microscopy. RNA was extracted by Trizol homogenisation in a GentleMACS (Miltenyi Biotec). RNA samples were reversibly transcribed to cDNA and RT QPCR were performed using a ViiA7 (Life Technologies) with QuantiTect primer assays (QIAGEN). Results are in relative expression to GAPDH. Results. MPM enabled the visualization of the scaffolds and viable cells grown for at least 14 days. Images demonstrate the distinct appearance of cells grown on highly aligned scaffold compared to random, grid-orientation and glass control. They also show the crimp-like appearance of the oriented scaffold as well as the cells on these crimped fibres. Interestingly, proliferation was not significantly effected by scaffold pattern. However, cell shape was clearly affected, and cells grown on oriented scaffolds showed higher anisotropy and elongated, narrower cell shape compared to all other groups, presenting a more tendon-like phenotype. This was further supported by a strong increase in the expression of β-actin on the aligned compared to the randomly oriented scaffold, correlating with observed changes in cell length and shape. Conclusion. The aim of this study was to compare patterns (aligned, random and grid) of electrospun polydioxanone scaffolds as templates for tendon repair. Aligned PDO scaffolds significantly affected cell length, width, and orientation. We also found that β-actin expression was significantly increased on aligned polydioxanone scaffolds. Moreover, PDO scaffolds fabricated as aligned/oriented were observed to present crimp-like morphology, similar to native tendon. Taken together, these findings suggest an aligned morphology of polydioxanone may hold the potential to improve tendon healing

Large and retracted rotator cuff tendon tears fail to repair, or re-tear following surgical intervention. This study attempted to develop novel tissue engineering approaches using tenocytes-seeded bioscaffolds for tendon reconstruction of massive rotator cuff tendon defect in rabbits. Porcine small intestine submucosa (Restore™) and type I/III collagen bioscaffold (ACI-MaixTM) were chosen as bioscaffold carriers for autologous tenocytes. Biological characterization of autologous tenocytes was conducted prior to the implantation. The tenocyte-seeded bioscaffolds were implanted as interposition grafts to reconstruct massive rotator cuff tendon defects in rabbits. In situ re-implantation of the autologous rotator cuff tendon, excised during defect creation served as a positive control. Histological outcomes were analysed and semi-quantitatively graded at four and eight weeks after surgery. The results demonstrate that at four weeks both tenocyte-seeded bioscaffolds display inflammatory reaction similar to bioscaffold-only cuff reconstruction and the histological grading were inferior to control repair. However, at eight weeks inflammatory reaction of both tenocyte-seeded bioscaffolds were dramatically reduced as compared to bioscaffold alone. In addition, bioscaf-folds seeded with tenocytes generated similar histological appearance to that of the positive control. The implantation of autologous tenocytes on collagen-based bioscaffold offers improved rotator cuff tendon healing and remodelling compared to the implantation of bioscaffold alone

OBJECTIVE: The purpose of this study is to examine the effect of a single percutaneous injection of platelet-rich-plasma compared to an injection of corticosteroids in patients with chronic lateral epicondylitis. BACKGROUND: Lateral epicondylitis is a common problem that usually resolves with nonoperative treatments. Platelet Rich Plasma (PRP) is a component of whole blood that contains concentrated amounts of powerful growth factors. PRP has been used for a variety of orthopedic applications including tendinopathy, wound healing and spinal fusion with varying degrees of success. Buffered PRP has also been used to enhance cell proliferation in-vitro. HYPOTHESIS: Treatment of chronic severe lateral epicondylitis with buffered platelet-rich plasma will reduce pain and increase function in patients considering surgery for their problem. METHODS: One hundred patients with persistent lateral epicondylar pain were evaluated in this study. All these patients were initially given a variety of nonoperative treatments. These patients had significant persistent pain for at least 3 months despite these interventions. All patients were considering surgery. This cohort of patients who had failed nonoperative treatment was then given either a single percutaneous injection of platelet-rich plasma (experimental group, n = 50) or corticosteroids (control group, n = 50). RESULTS: PRP has a significant better effect on lateral epicondylitis than corticosteroid injections. CONCLUSION: This in-vivo data suggest that tendon healing is occurring in lateral epicondylitis using PRP

This study looks at the dynamic tendon-to-bone contact properties of rotator cuff (RC) repairs—comparing single row repairs (SRR) with double row transosseous- equivalent (TOE) repairs. It was postulated that relaxation during, and movement following, the repair would significantly compromise contact properties and therefore, the ability of the tendon healing. Simulated tears were created in the supraspinatus tendon of six cadaveric human shoulders. A SRR was then performed using the OPUS System, creating two horizontal mattress sutures. An I-Scan electronic pressure-sensor (Tekscan, Boston, MA) was placed between the supraspinatus tendon and bone. The arm was then rested for 300secs (relaxation) before being passively moved twice through a range-of-motion (0-90 degrees abduction, 0-45 external and 0-45 internal rotation) and finally returned to neutral. The contact properties were recorded throughout each movement. The procedure was then repeated using two TOE techniques: parallel sutures (TOE-P) and a cross over suture pattern (TOE-C). While peak pressures during the repair were higher in the two TOE repairs, all three methods demonstrated relaxation over 300s such that there was no significant diference in contact pressures at the end of this time. TOE parallel and cross-over repairs demonstrated no significant change in mean TTB contact pressure, force and area during abduction, external rotation and return to neutral, when compared to the 300sec relaxation state. TOE-C demonstrated a higher contact force on internal rotation (+53%). The SRR demonstrated a significant drop in contact force on abduction (−63%), and return to neutral (−43%) and a trend on external rotation (−34%). SRR exhibited no change on internal rotation. There have been very few biomechanical studies with which observe RC repair contact properties dynamically. Relaxation of the repair can be partially reversed. Significant decrease in contact area with SRR during movement occurred, compared to the TOE repairs, which remains unaltered. This is an important consideration when determining postoperative rehabilitation

Aims

The aim of this meta-analysis was to assess the prognosis after early functional rehabilitation or traditional immobilization in patients who underwent operative or nonoperative treatment for rupture of the Achilles tendon.

Summary Statement. Transportation media and injection protocol have implications for the viability of MSCs used for intra-lesional treatment of tendon injuries. Every effort should be made to implant cells within 24h of laboratory re-suspension, using a needle bore larger than 21G. Introduction. Intra-lesional implantation of autologous mesenchymal stem cells (MSCs) has resulted in significant improvements in tendon healing in experimental animal models. Intra-tendinous injection of MSCs into naturally-occurring equine tendon injuries has been shown to be both safe and efficacious. 1. and these protocols can assist in the translation to the human. Efficient transfer of cells from the laboratory into the tissue requires well validated techniques for transportation and implantation. The aim of this study was to determine the influence of transport media and injection procedure on cellular damage. Methods. Bone marrow derived MSCs (n=3 horses) were prepared and expanded as described. 1. Cells were suspended in 0.5mL of experimental media at 2.5×10. 6. cells/mL and stored at 4–8°C for 24, 48 and 72h. Experimental media were: bone marrow aspirate (BMA); cell culture media (DMEM); equine serum; equine plasma; isotonic saline; hyaluronic acid (HA); platelet-rich plasma (PRP) and frozen (in 90% serum, 10% DMSO). In addition, cells suspended in DMEM were injected through a 19G, 21G or 23G needle and cell viability, proliferation and apoptosis were analysed using trypan blue, alamarBlue® and Annexin-V assays respectively. Results. There was no significant difference in overall viability at 24h storage in any media, however cell death was most rapid when cells were suspended in BMA, PRP and serum. Viability was greatest at all time points when cells were frozen. Cell proliferation was similar following storage for 24 and 72h in all media, except for 24h in serum, wherein proliferation was enhanced. There was no significant decrease in viability immediately following injection but 21G and 23G needles resulted in a marked increase in apoptotic cells compared to 19G and non-injected controls after 24h when re-seeded for culture. All needle gauges resulted in a marked decrease in cell proliferation immediately post-injection with recovery by 2h post-injection. Conclusions. Although there is, as yet, no guidance on the storage of MSCs, it has been suggested that in vitro storage of hematopoietic stem or progenitor cells should not exceed 2h. 2. This suggestion is impractical both for current equine therapeutic use and when considering future, commercial applications of MSC therapy in humans, because of the necessity to transport the cells from a remote licensed facility to the clinic. Our data suggest an upper limit of 24h for transportation, whereas for transportation of greater duration than 24h, cells should ideally be frozen, to maximise viability. An increased number of dead cells potentially has two adverse consequences; first, a reduced efficacy and second, the presence of dead cell debris may induce inflammation. While the first can be compensated for by higher cell numbers, this compounds the problems of the second. This study reinforces the importance of limiting the delay between preparation of cells for shipment from the laboratory and implantation in the clinic and suggests that an injection procedure while not causing immediate cell death can cause significant delayed cell death if small bore needles are used

We reconstructed defects in the infraspinatus tendon using polytetrafluoroethylene (PTFE) felt grafts in 31 beagle dogs and examined the mechanical responses and histocompatibility. Except for one infected specimen, all the reconstructed infraspinatus tendons healed. We examined eight specimens each immediately after surgery and at six and 12 weeks. The ultimate tensile strength of the reconstructed tendons was 60.84 N, 172.88 N, and 306.51 N immediately after surgery and at six and 12 weeks, respectively. The stiffness of the specimens at the PTFE felt-bone interface was 9.61 kN/m, 64.67 kN/m, and 135.09 kN/m immediately after surgery and at six and 12 weeks, respectively. Six tendons were examined histologically at three, six, 12 and 24 weeks. Histological analysis showed that there was ingrowth of fibrous tissue between the PTFE fibres. Foreign-body reactions were found at the margin of the PTFE-bone interface between 12 and 24 weeks. The mechanical recovery and tissue affinity of PTFE felt to bone and to tendon support its use for reconstruction of the rotator cuff. The possible development of a foreign-body reaction should be borne in mind

Introduction. Latissimus dorsi transfer is a procedure used in massive irreparable posterosuperior rotator cuff tears, in young patient with severe pain and significant functional impairment. The purpose of this retrospective study was to evaluate its clinical, radiological and electromyographic results. Methods. Forteen massive irreparable posterosuperior rotator cuff tears were performed with latissimus dorsi transfer between 2000 and 2008, and were reviewed at an average follow-up of 56 months and minimum of 19 months. Five transfers were primary reconstructions, and nine were revision surgeries. Patients’ mean age was 52.7 years. Clinical outcomes were measured by the Constant score, pain level, active range of motion, and strength. Osteoarthritis and acromiohumeral distance were measured on standardized radiographs. Ultrasound examination evaluate the integrity of the tendon. Axial images in CT-scan looked for muscle atrophy of latissimus dorsi in comparison with the controlateral. Electromyographic activity was measured during active flexion, abduction, adduction and rotations. Results. Twelve patients were satisfied. At the last follow-up, the average pain level according to a 100 mm visual analog scale was 31. The mean age and gender-matched Constant and Murley score improved from 34 to 60 % (p=0.003), forward elevation from 89° to 132° (p=0.006), abduction from 92° to 104°, external rotation from 12° to 24° (p=0.015). Mean abduction and external rotation strength were measured at 2.5 kg. Osteoarthritis progressed, and mean acromio-humeral distance has a significant decrease from 7.5 mm to 4.4 mm (p=0.003). Ultrasound examination showed twelve transferred tendons healed to the greater tuberosity. CT-scan showed a small atrophy of the transferred muscle, with a measurement of the cross-sectional area of the muscle belly at the inferior angle of the scapula at 1405 mm2, versus 1644 mm2 for the controlateral (p=0.06). Electromyographic analysis demonstrated a significant higher electric activity on the operative side during abduction and external rotation, and significant lower activity during adduction and internal rotation in comparison with the nonoperative side. Conclusions. Latissimus dorsi transfer allows for significant pain relief and function improvement in irreparable posterosuperior rotator cuff tears at young patients. Its electric activity increase in abduction and external rotation shows that the transferred muscle can integrate a new function and act like an active muscle transfer, in addition to an interposition or tenodesis effect. However we didn't find any depression of the humeral head or strength improvement

Introduction: Recent in vivo studies of flexor tendon midsubstance healing have indicated that during the first 10 days after injury and repair there is no increase in ultimate tensile force. In contrast, there is an increase of approximately 170% in the rigidity (stiffness) of the repair site and a decrease of more than 45% in the repair-site strain at 20 N force. The basis for the increase in rigidity during the early stages of tendon healing is not known, but may be due to either biological or mechanical factors. In particular, cyclic loading of the tendon repair site during post-operative rehabilitation may have a mechanical conditioning effect that increases the stiffness of the repair site independent of repair-site healing. Our objective was to determine whether or not cyclic loading of repaired flexor tendons causes an in increase in repair-site rigidity and whether or not this increase depends on the level of applied force. We simulated 10 days of passive motion rehabilitation by applying 6000 loading cycles to repaired flexor tendons ex vivo at force levels generated during passive motion rehabilitation. We then evaluated the tensile mechanical properties. We hypothesized that cyclic loading causes an increase in repair-site rigidity and a decrease in repair-site strain. Materials and Methods Forty-eight flexor digitorum profundus (FDP) tendons with attached distal phalanges were obtained from twelve hindlimbs of six adult mongrel dogs. Specimens were randomly assigned to one of three groups: control (no loading), low-force (5 N) cyclic loading or high force (17 N) cyclic loading. Tendons were transected in Zone II, 4 cm proximal to the insertion site. They were repaired using a four-strand modified Kessler technique with double-stranded 4-0 Supramid suture (S. Jackson) supplemented with a running peripheral suture of 6-0 Prolene (Ethicon). For cyclic loading, the distal phalanx and proximal tendon stump were placed in custom clamps attached to a materials testing machine (Instron 8500R). Tendons in the low-force and high-force groups were loaded for 6000 cycles at 2 Hz from 0.5 N to peak forces of 5 and 17 N, respectively. The force levels were chosen to match the peak tendon forces that were measured in vivo for low- and high-force passive motion rehabilitation protocols of the canine forelimb; 6000 cycles were used to simulate the number of cycles applied during a 10-day period of rehabilitation (600 cycles/day). Specimens in the control group were sham loaded for an equivalent period of time (50 minutes). After cyclic loading, specimens were allowed to recover for 1 hour and then tested to failure in tension. From plots of force versus repair-site strain we determined ultimate (maximum) force (N), repair-site rigidity (N/[mm/mm]) and repair-site strain (%) at 20 N force. One-way analysis of variance was used to determine the effect of loading on tensile properties. Results: Specimens subjected to high-force cyclic loading had significantly increased rigidity compared to specimens in the low-force and control groups. Rigidity in the high-force group was increased by 100% compared to control. Similarly, repair-site strain at 20 N was decreased by 50% in the high-force group compared to control group. Ultimate force was increased in the high force group compared to control (p = 0.02; Table), but the magnitude of the increase was only 13%. There were no significant differences between the low-force and control groups (p > 0.05). Discussion: Based on our findings, we conclude: 1) Repair-site rigidity is increased by 100% and repair-site strain decreased by 50% following 6000 cycles of high-force (17 N) loading. In contrast, ultimate force is changed only slightly (13%) by high-force loading. 2) Mechanical conditioning of the repair site by repetitive forces applied during rehabilitation may have a consequence that has not been noted previously, i.e. it leads to increases in rigidity and decreases in strain. This effect may explain in part the changes in tensile properties observed after only 10 days of healing in vivo. 3) The lack of effect of low-force (5 N) loading on repair-site rigidity and strain is in contrast to the previous in vivo findings in which rigidity increased in the low-force rehabilitation group. This discrepancy suggests that the observed in vivo changes can not be explained entirely by mechanical conditioning effects. 4) Therefore, both biological and mechanical factors are likely to play an important role in the rapid changes in repair-site mechanical properties that occur following flexor tendon injury and repair

The healing of a hamstring graft to bone is the weak link in the reconstruction of a cruciate ligament using this donor material. We therefore investigated the augmentation of healing at the tendon-bone interface using calcium-phosphate cement (CPC). We performed semitendinosus autograft reconstructions of the anterior cruciate ligament on both knees of 22 New Zealand white rabbits. The interface between the grafted tendon and the bone tunnel for one knee was filled with CPC. Six rabbits were killed at the end of the first and second post-operative weeks in order to evaluate the biomechanical changes. Two rabbits were then killed sequentially at the end of weeks 1, 3, 6, 12 and 24 after operation and tissue removed for serial histological observation. Histological examination showed that the use of CPC produced early, diffuse and massive bone ingrowth. By contrast, in the non-CPC group of rabbits only a thin layer of new bone was seen. Mechanical pull-out testing at one week showed that the mean maximal tensile strength was 6.505 ± 1.333 N for the CPC group and 2.048 ± 0.950 N for the non-CPC group. At two weeks the values were 11.491 ± 2.865 N and 5.452 ± 3.955 N, respectively. Our findings indicate that CPC is a potentially promising material in clinical practice as regards its ability to reinforce the fixation of the tendon attachment to bone and to augment the overall effectiveness of tendon healing to bone

Healing of the subscapularis, documented by ultrasound, following total shoulder arthroplasty was examined in thirty shoulders. All had marked improvement in pain, SST, and ASES scores. Four subscapularis tears were identified but only one patient had a positive abdominal compression test, 7/26 patients had a positive compression test despite an intact cuff, and 4/7 patients had a significant internal rotation contracture. The abdominal compression test was not accurate in detecting sub-scapularis tears. There was a significant false positive rate, which may be related to a lack of internal rotation. Overall, the outcome was excellent and not related to the status of the subscapularis. Very little information is available on healing of the subscapularis after shoulder arthroplasty. The purpose of this study was to document the subscapularis healing rate and relate it to post-operative function and the abdominal compression test. Thirty consecutive shoulders (twenty-three patients) s/p total shoulder replacement had standardized pre- and post-operative examinations including quantitative strength assessment and specific subscapularis testing. Ultrasound (validated for postop accuracy) was performed to document tendon healing. All thirty shoulders had marked improvements in pain, SST, and ASES scores. Four subscapularis tears were identified but only one patient had a positive abdominal compression test. Seven out of twenty-six patients had a positive compression test despite an intact cuff. Four of seven patients had a significant internal rotation contracture. Neither the status of the subscapularis nor a positive compression test appeared to affect outcome. Although specific subscapularis tests are often positive, only a small percentage of subscapularis tendons appear to retear after shoulder arthroplasty. The abdominal compression test is not accurate in detecting subscapularis tears post arthroplasty. There is a significant false positive rate, which may be related to a lack of internal rotation. However, overall outcome of shoulder arthroplasty was excellent and did not appear to be dependant on the status of the subscapularis

Purpose: The “Hill-Sachs Remplissage” (HSR) is a procedure used in the treatment of anterior shoulder instability associated with an engaging Hill-Sachs (HS) defect. It consists of an arthroscopic capsulotenodesis of the posterior capsule and infraspinatus tendon within the defect. There is currently no evidence that the capsule and tendon heal in the humeral bone defect. Our hypotheses were. that the capsulotenodesis heals in the HS defect and fills at least 50% of its area; and,. that limitation of range of motion compared to the non-operated shoulder would be minimal. Method: Prospective clinical study. Inclusion criteria:. recurrent anterior shoulder instability;. engaging HS lesion. Exclusion criteria:. glenoid bone loss;. rotator cuff tear. Twenty-nine patients underwent an arthroscopic Bankart repair plus HSR. Clinical assessment at a mean follow up of 13.1 months (range 6 to 32 months) consisted of a structured interview and detailed physical examination including range of motion compare to the contralateral shoulder and instability signs. Range of motion was analyzed in two groups according to length of follow-up, Group 1 with less than 12 months follow-up (14 patients); and Group 2 with greater than 12 months follow-up (15 patients). Either a CT arthrogram (25 patients) or an Arthro-MRI (2 patient) was performed at a minimum of six months postoperatively. Four orthopaedic surgeons analyzed the images independently to determine the percentage of healing of the capsulotenodesis. Results: There was no recurrence of instability at the latest follow-up. There was no statistically significant deficit in forward elevation in either group. Group 1 patients had statistically significant mean deficits as compared to the contralateral side of 15 degrees of external rotation in adduction (ER1), 15 degrees of external rotation at 90 degrees of abduction (ER2), and 1.1 points of internal rotation in adduction according to the Constant score system (ER1). Group 2 patients had statistically significant mean deficits of 4 degrees of ER1 and 11 degrees of ER2, with no significant difference in IR1. There was healing of the capsulotenodesis within the bone defect in all twenty-seven patients. The bone defect was filled more than 75% of its surface in 22 of 29 patients (76%). The remaining seven had between 50 and 75% filling (24%). There was no defect filling of less than 50% in this study. Conclusion: We demonstrated greater than 50% HS defect filling in all patients in our series after an arthroscopic “Hill-Sachs Remplissage” and filling > 75% in 22 of 29 (76%). Modest deficits of external rotation were demonstrated at greater than 12 months follow-up. While these results suggest that the technical goal of HS defect filling is achievable, longer term studies are necessary to establish whether there is an association between the rate of healing, the functional impairment of external rotation and clinical outcomes

Introduction: New biotechnologies create opportunities for gene therapy to promote rotator cuff healing. We have previously demonstrated that genetically engineered mesenchymal stem cells (MSCs) over expressing BMP-2 and SMAD8 signaling molecule differentiate to tenocytes in vitro and in vivo. Therefore, we hypothesized that rotator cuff defect could be regenerated using genetically engineered MSCs. Method: Nonviral methods were utilized to establish genetically engineered MSCs that co-express BMP-2 and the Smad8 signaling molecule. A previously validated animal model was utilized to examine rotator cuff healing. A 2mm x2mm full thickness defect was created in the infraspinatus tendon of 8 nude rats. A collagen-I biomembrane (TissueMend) containing 3 x 10. 6. engineered cells was sewn into the defect. An identical control procedure was repeated on the contralateral side with biomembrane containing non-engineered MSCs. Results: 4 weeks post implantation the area of implantation was isolated and analyzed by light microscopy and histochemical staining. Analysis of the engineered implants revealed the formation of dense connective tissue with parallel-organized fibers and spindle shaped cells, unlike the control samples. Proton Double Quantum Filtered Magnetic Resonance Imaging technique of the rotator cuff tendons demonstrated an increased presence of organized collagen fibers within the engineered rotator cuff tissue when compared with either native rotator cuff or those treated with non-engineered MSCs. Conclusion: This is the first report showing rotator cuff tendon repair using genetically engineered MSCs. Moreover these findings may have considerable importance for tendon healing and may indicate a clinical gene therapy platform to augment surgical repair

Purpose of the study: Arthroscopic repair of rotator cuff tendons is a well-described technique. Clinical outcome is good. The purpose of this work was to assess tendon healing as observed with the arthroscan after arthroscopic repair of rotator cuff tears. We search for epidemiological, anatomic, and technical factors predictive of healing. Material and methods: This was a prospective consecutive non-randomized series of 167 shoulders. All patients were assessed preoperatively with the Constant clinical score and had a standard imaging protocol for assessing the status of the rotator cuff. Arthroscopic repair was used in all cases. Outcome was assessed with the Constant score and an arthroscan was available for 148 patients. Results: Mean patient age was 59 years, 49% male and 77% dominant side. Mean duration of symptoms before repair was nine months. The tear resulted from trauma in 28% and was a work accident in 9%. The preoperative functional assessment was 52.48. An isolated supraspinatus tear was observed in 68% of the shoulders. Frontal retraction of the supraspinatus was distal in 74%. For 29 shoulders, reduction was difficult and the quality of the tendon was considered normal in 56. Non-anatomic repair was required in six cases. The Constant score at last follow-up (19 months) was 80. An arthroscan was available for 148 shoulders: healing was anatomic in 69, defective healing was observed in 27 and repeated tears were noted in 52. Factors predictive of healing were: demographic (lesion duration less than six months, non-dominant side, young patient, female gender, sedentary lifestyle); anatomic (isolated lesion of the supraspinatus with little extension and no retraction); technical (normal easily reduced tendon, good quality bone). Discussion: The time before surgical management of rotator cuff tears was an important factor in this study. Tendon and muscle alterations after rotator cuff tears could explain, at least in part, healing failures. Conclusion: This study confirmed the good functional and anatomic results obtained with arthroscopic repair of rotator cuff tears

Aims: Peroneal tendons possess a vascular supply through a mesotendineal structure named vinculum; vincula are identifiable with tendoscopy and are supposed to play a role in tendon healing response, due to prominent vascularity; aim of the study is to verify the feasibility of tendoscopy in evaluating peroneal tendons, to clarify the histological structure of peroneal vincula and to investigate the presence of nervous tissue, so formulating a hypothesis regarding the functional role of vincula. Methods: cadaver study was performed on 8 fresh-frozen ankles; dissection were conducted to verify accessibility of endoscope, proximity with superficial peroneal nerve and presence of vincula; samples of vincula were obtained; light microscopy and immunohisto-chemistry (anti-human S100 antibody) were performed, describing structure of vincula and identifying peripheral nerve fibers. 5 peroneal vincula biopsies were analyzed from patients affected by ankle instability and undergoing tendoscopy for peroneal tenosynovitis. Results: peroneal tendons are accessible along the whole common tendon sheath and a discrete distance between the endoscope and the superficial peroneal nerve is present in all specimens; a membranous mesotendineal structure was found in all specimens between both tendons and tendon sheath; macroscopic inspection revealed the presence of a vessel network, arising from the sheath toward the tendon; light microscopy of cadaver samples confirmed the presence of multiple vessel branches crossing the entire structure of the vinculum and identified nervous structures close to the vessels, resembling a neurovascular bundle; immunohistochemical analysis revealed nerve fibers in each specimen;tendoscopy in patients affected by ankle instability showed lesions of the vincula and histology from intraoperative biopsies showed presence of nerve fibers. Conclusions: tendoscopy is a useful tool to visualize peroneal tendons and to diagnose and treat different disorders; although literature provides no data about innervations of peroneal vincula, the study shows nervous fibers consistently present inside the intimate structure of vinculum; besides its function in repair and healing processes, this suggests a proprioceptive role of the vinculum in peroneal tendon physiology and lesion of vinculum could be an important element acting synergistically with joint capsule and surrounding tissues lesions and ultimately leading to clinical pictures of ankle instability

Background. High re-rupture rates following repairs of rotator cuff tears (RCTs) have resulted in the increased use of repair grafts to act as temporary scaffolds to support tendon healing. It has been estimated that thousands of extracellular matrix repair grafts are used annually to augment surgical repair of rotator cuff tears. The only mechanical assessment of the suitability of these grafts for rotator cuff repair has been made using tensile testing only, and compared grafts to canine infraspinatus. As the shoulder and rotator cuff tendons are exposed to shearing as well as uniaxial loading, we compared the response of repair grafts and human rotator cuff tendons to shearing mechanical stress. We used a novel technique to study material deformation, dynamic shear analysis (DSA). Methods. The shear properties of four RCT repair grafts were measured (Restore, GraftJacket, Zimmer Collagen Repair and SportsMesh). 3mm-sized biopsy samples were taken and subjected to DSA using oscillatory deformation under compression to calculate the storage modulus (G') as an indicator of mechanical integrity. To assess how well the repair grafts were matched to normal rotator cuff tendons, the storage modulus was calculated for 18 human rotator cuff specimens which were obtained from patients aged between 22 and 89 years (mean age 58.8 years, with 9 males and 9 females). Control human rotator cuff tendons were obtained from the edge of tendons during hemiarthoplasties and stabilisations. A 1-way ANOVA of all of the groups was performed to compare shear properties between the different commercially available repair grafts and human rotator cuff tendons to see if they were different. Specific comparison between the different repair grafts and normal rotator cuff tendons was done using a Dunn's multiple comparison test. Results. We report a significant difference in the shear moduli of all four rotator cuff repair grafts (P<0.0001, 1 way ANOVA, Kruskall-Wallis test). 2 of the grafts, Zimmer Collagen Repair and SportMesh, were not significantly different when compared to rotator cuff tendons and were found to have comparable shear mechanical properties (P > 0.05, Dunn's multiple comparison test). The other repair grafts, GraftJacket and Restore, had a significantly lower storage modulus when compared to human rotator cuff tendons. Conclusions. With increasing numbers of repairs of rotator cuff tears, and augmentation of these repairs, there is a need to understand the mechanical and biological properties of the both repair grafts and the tendons they are designed to augment. At present there is no clear definition of the ideal mechanobiological properties of rotator cuff repair patches. Current rotator cuff repair grafts display a wide variation in their shear mechanical properties, and how closely they are matched to the mechanical properties of human rotator cuff tendons. It is hoped that this study may help to guide surgeons in deciding on the most appropriate rotator cuff tendon repair graft

Aim of the study: To evaluate whether additional aperture fixation to distal fixation (two-point fixation or 2P) may diminish tibial tunnel enlargement compared to distal fixation alone (one-point fixation or1P). Methods: Two groups of patients were evaluated. In group 1P (44pts.) the grafts were fixed on the tibial side, using two 4 mm Mersilene tapes tied over a 10 mm bone bridge created in the anterior cortex. In group 2P, an additional fixation, using 1 absorbable cross pin in 27 pts. and 2 absorbable cross pins (Rigid fix, Mitek) in 24 pts., was performed. AP and lateral radiographs as well as patients evaluation were performed 3, 6 and 12 months post-op. Tibial tunnel size was measured at the widest diameter in both AP and lateral radiographs. Results: Tunnel enlargement occurred in both groups at 3 months post-op, but not thereafter. In the lateral radiographs, tunnel enlargement was significantly less in group 2P compared to group 1P (p< 0.05). No statistical relationship was found between tunnel enlargement and gender, age, IKDC, and KT 1000 side-to-side difference. Conclusion: Additional tibial graft fixation with cross-pins seems to diminish tibial tunnel enlargement in the sagital plane. This may be explained by the fact that the cross pins inserted in the coronal plane, reduce tibial graft movements mainly in the sagital plane. The study supports the hypothesis that tibial graft micro-movements during the period of tendon healing to bone (up to 3m) play a role in tibial tunnel enlargement after ACL reconstruction using hamstrings

Restoring of anatomic footprint may improve the healing and mechanical strength of repaired tendons. A double row of suture anchors increases the tendon-bone contact area, reconstituting a more anatomic configuration of the rotator cuff footprint. We aimed to investigate if there were differences in clinical and imaging outcome between single row and double row suture anchor technique repairs of rotator cuff tears. We recruited 60 patients affected by a rotator cuff tear diagnosed on clinical grounds, magnetic resonance imaging evidence of cuff tear and inadequate response to nonoperative management, an unretracted and sufficiently mobile full-thickness rotator cuff lesion to allow a double row repair found at the time of surgery. In 30 patients, rotator cuff repair was performed with single row suture anchor technique (Group 1). In the other 30 patients, rotator cuff repair was performed with double row suture anchor technique (Group 2). 8 patients (4 in the single row anchor repair group and 4 in the double row anchor repair group) were lost at follow up. A modified UCLA shoulder rating scale was used to evaluate preoperative and postoperative shoulder pain, function and range of motion, strength and patient satisfaction. All patients received a post-operative MR arthrography at the final follow up appointment. At the 2 year follow-up, no statistically significant differences were seen with respect to the UCLA score and ROM values. Post-operative MR arthrography at 2 years of follow up in group 1 showed intact tendons in 14 patients, partial thickness defects in 10 patients and full thickness defects in 2 patients. In group 2, MR arthrography showed an intact rotator cuff in 18 patients, partial thickness defects in 7 patients, and full thickness defects in 1 patient. Biomechanical studies comparing single versus double row suture anchor technique for rotator cuff repair show that a double row of suture anchors increases the tendonbone contact area and restores the anatomic rotator cuff footprint, providing a better environment for tendon healing. Our study shows that there are no advantages in using a double row suture anchor technique to restore the anatomical footprint. The mechanical advantages evidenced in cadaveric studies do not translate into superior clinical performance when compared with the more traditionally, technically less demanding, and economically more advantageous technique of single row suture anchor repair

Purpose of the study: Surgical treatment of rotator cuff tears (RCT) in the older subject is genearlly considered to best involve simple debridement without any attempt at repair. This is however no evidence concerning the healing capacity of tendon repairs after RCT in the older subject. The purpose of this study was to assess the functional outcome of arthroscopically repaired RCT in subjects aged over 65 and to determine the healing pattern. Materials and Methods: This was a non-randomized prospective study which included patients aged over 65 years who presented a full thickness RCT repaired arthroscopically. The patients were evaluated preoperatively and at last follow-up with the simple shoulder test (SST) and the Constant score. A control arthroscan was obtained systematically six months postoperatively. Results: From January 2001 through December 2004, 88 patients, mean age 70 years were included in this study with a mean follow-up of three years (range 2–5 years). The tear involved two tendons in 45 shoulders, the frontal retraction was distal in 58 shoulders, the index of fatty degeneration was 0.6 (range 0–3) preoperatively and 13 patients presented stage 1 chondral lesions. The SST improved from 2.4 (range 1–6) preoperatively to 9.7 (3–12) at last follow-up (p< 0.001) and the Constant score from 45 (10–70) to 77.7 (49–93) (p< 0.001) Seventy-seven patients (87.5%) had a control arthroscan and 45 had an intact cuff. For the patients with an intact cuff, the SST was 10.6 and the Constant score 81.6 versus respectively 7.8 and 72.1 for patients with a non intact cuff (p< 0.001). Factors predictive of non healing were size of the tear (p=0.02), its frontal extension (p=0.01), its tendinous aspect (p=0.02) and difficult reduction (p=0.005). There was no increase in the size of the tears (p=0.46). Six patients presented Hamada stage 1 osteoarthritis at last follow-up. Discussion: This study is the first to demonstrate objective evidence of tendon healing after arthroscopic repair of RCT in patients aged over 65 years. In 59% of the patients, the arthroscan demonstrated intact cuffs with a significant improvement in the functional results. Conclusion: Arthroscopic repair of RCT in subjects aged over 65 years provides satisfactory results and can be proposed as treatment

The practice of rotator cuff repair rapidly moves towards arthroscopic techniques especially for single tendon tears. Although the clinical results are relatively well established, the structural results of open rotator cuff repair and their correlation with the clinical outcome are poorly known. In order to provide a baseline for future studies using other repair techniques, this study was carried out to assess the structural changes in the repaired musculotendinous unit and to correlate these findings with the clinical outcome after rupture and repair of an isolated full thickness single tendon tear of the rotator cuff. To prospectively assess the quality of an open rotator cuff tendon repair technique, to determine how structural changes of rotator cuff muscles are affected by tendon repair, and to correlate the structural results of MRI studies with the clinical outcome. Direct open repair of a complete, isolated single tendon tear of the rotator cuff resulted in significant improvement in function and objective evidence of tendon healing on MRI. Successful direct repair was not associated with recovery of preoperative muscular atrophy or fatty infiltration when comparing Goutallier stage fatty infiltration between pre and postoperative patients. The age and gender-adjusted Constant score increased significantly from an average of 63.9% preoperatively to 94.5% postoperatively (p< 0.0001). Pain improved significantly from 6.8 points to 13.2 points on a visual analogue scale. (p< 0.0001). Activities of daily living increased from 11.2 points preoperatively to 17.9 points postoperatively (p< 0.0001). Anterior elevation, abduction and internal rotation improved significantly for subscapularis and supraspinatus repairs, but there was no significant change in external rotation. The overall rerupture rate was 12.5%. There was no significant improvement or recovery of muscular atrophy or fatty infiltration after tendon repair. Thirty-two consecutive open repairs of a single tendon tear of the rotator cuff were analysed. The supraspinatus tendon was involved in twenty-two patients and the subscapularis tendon in ten patients. All tendons were repaired using an open technique, a modified Mason-Allen suturing technique, and transosseus fixation with non-absorbable suture material knotted over a bone augmentation device

Aims: Healing of the rotator cuff after surgical repair continues to be one of the most challenging areas of shoulder surgery. Autologous Platelet Derived Grow Factors (PDGF) have been shown to positively affect the tissue healing, but their effect have not been studied in relation to tendon healing. The purpose of this study is to evaluate if the use of PDGF in rotator cuff surgery could lead to a better and faster healing of the repair. Materials e Methods: We treated two groups (A,B) of 14 shoulders in 14 patients (mean age 66 and 63.4) with a full thickness rotator cuff tear. The group A and B were treated with a full arthroscopic repair of the cuff. In the group A, at the end of the procedure, the PDGF have been injected at the level of the lesion, between the tendon and the bone and over the tendon repair without irrigation and after the removal of all the cannulas. The group B, repaired in the same fashion, without PDGF, has been used as control. In the group A the patients had an accelerated postop. rehabilitation. The group B received a standard rehabilitation protocol. Each group has been evaluated prospectively with VAS, UCLA and Constant scores pre-op and during follow-up. Results: Both group showed an increase of the scores, compared to the pre-op. value (tab.1). The VAS score of group A (PDGF) was pre-op. 5.6 and at 1 year 1.4. The VAS score of group B (no PDGF) was pre-op. 5.2 and at 1 year 1.4. The UCLA score of group A was pre-op. 16 and at 1 year 33.8. The UCLA score of group B was pre-op. 16.7 and at 1 year 32.9. The Constant score of group A was pre-op. 53 and at 1 year 90.7. The Constant score of group B was pre-op. 54.2 and at 1 year 90.1. The complete statistical analysis of the data showed no significant differences in the results of the two groups (p< 0,01), with every kind of scores, VAS, UCLA and Constant, at the final follow-up of 1 year. Conclusions: Our data suggest that the use of PDGF, compared to a standard repair, does not affect the quality of the rotator cuff repair at 1 year. Moreover the study suggest that the use of PDGF allows an accelerated rehabilitation program with ten days of immobilization compared to four weeks as usually prescribed. Further studies should clarify the real effect of PDGF about the acceleration of the first phase of the cuff healing

Aims

Rotator cuff (RC) tears are common musculoskeletal injuries which often require surgical intervention. Noninvasive pulsed electromagnetic field (PEMF) devices have been approved for treatment of long-bone fracture nonunions and as an adjunct to lumbar and cervical spine fusion surgery. This study aimed to assess the effect of continuous PEMF on postoperative RC healing in a rat RC repair model.

Introduction: As Achilles tendon ruptures are healing slowly, many attempts are made trying to improve the healing after injury. Rat experiments have shown that injection of platelets improves tendon healing. A clinical study on patients has also shown a better outcome after injecting platelets into the rupture area. Therefore we wanted to verify the effect of platelets by measuring the mechanical properties of the healing Achilles tendon in a randomised study. Methods: We included 30 patients with an Achilles tendon rupture. All patients left one blood unit at the hospital blood bank. From this unit of blood approximately 20 ml of platelet concentrate were gained. All patients were operated the next day using an open technique. Just before wound closure, patients were randomised into 2 groups, with one group receiving 10 ml of their own platelet concentrate. In order to measure mechanical properties, we implanted Tantalum beads on either side of the rupture giving us the chance of exactly determining the distance between the beads using RSA and thereby measuring the stiffness of the tendon. CT was used to measure the area of the rupture site. Both groups were postoperatively treated with a cast for 7 weeks. 4 weeks with the ankle in the equines position and 3 weeks in the neutral position. After cast removal, the patients started rehabilitation. The patients in both groups received exactly the same treatment after surgery. Patients were examined with CT and RSA to determine area, stiffness and modulus of elasticity. Measurements were performed at 7 weeks after operation and again at 19 weeks. Results: 16 patients were randomised to platelet concentrate. One patient got a deep infection and another patient suffered from a rerupture of the Achilles tendon. Both patients had to be excluded after the first CT- and RSA-examination. Both patients had received platelet concentrate. There was no significant difference between both groups after 7 and 19 weeks in area, stiffness or modulus of elasticity. Discussion: Our results indicate that platelet concentrate does not improve the mechanical properties of the healing Achilles tendon, at least when patients are treated with a cast for 7 weeks. Studies have shown that the effect of platelet concentrate is depending on a certain loading of the Achilles tendon during the early phase of healing. Unfortunately we do not know much about loading of the Achilles tendon while having the leg in a cast, but the rigid fixation might lead to certain unloading. Further studies are needed to learn more about loading of the Achilles tendon in a cast. Furthermore we have also done a clinical examination of all patients, as we know from a previous study that there is a correlation between early mechanical properties and clinical outcome but we have not evaluated the clinical results of this study yet

Objectives: The replacement tissue used for anterior cruciate ligament reconstruction undergoes extensive biologic remodelling and incorporation after implantation. These changes, in which the tendon loses some of its characteristic features and adopts those typically associated with ligaments, has been referred to as ligamentization. The purpose of this study was to identify the proinflammatory response in the healing graft in the early phase. Methodes: Twenty New Zealand White Rabbits underwent ACL reconstruction with a semitendinosus tendon. Animals were sacrificed at 3 and 6 weeks. The harvested tissue including parts of remaining grafted tendon and genuine anterior cruciate ligament at time of the surgery as well as the tendon graft withdrawn at sacrification were prepared for immunohistochemical, histomorphometry and electromicroscopical analysis; synovia samples were taken at the sacrification as well. The tissues were immunostained for IL-1beta, TGF-beta, TNF-alpha (induction of inflammatory cascade), COX-2 (mediator of inflammatory response), Matrix Metalloproteinases (MMP-1, MMP-3, MMP-13, matrix destructive enzymes), TIMP-2 (Tissue Inhibitor of MMPs); the PGE2 (mediator of inflammatory response) content in the synovia was quantified by ELISA. Results: At 3 weeks after surgery the COX-2+ cells accounted for 70% of all cells present in the graft tissue, and decreased to 28% at 6 weeks. Similar, IL-1beta+ cells within the tendon decreased from week 3 to week 6. Controversly, there was an increase of COX-2, IL-1beta and MMP-1 in the intercellular tissue. The numbers of COX-2+ cells and IL-1beta+ cells at 3 weeks as well as the intercellular area stained positiv for COX-2, IL-1beta and MMP-1 at 6 weeks were significantly larger compared to the genuine ACL (p =< 0.05). At 3 weeks some cells stained positiv for MMP-3 and MMP-13, but not at 6 weeks. There was a slight pericellular staining for TIMP-2 at 3 weeks. TGF-beta+ cells and TNF-alpha+ cells were almost not detectable at every time point. Thus, proinflammatory cytokines and MMPs were synthesized in the early phase after ACL reconstruction by the tendon cells and accumulated at 6 weeks in the intercellular tissue. Conclusions: In the early phase of the graft healing after ACL reconstruction, there was a signifikant increase in proinflammatory cytokines and matrix destructive enzymes in the tendon graft. With the capability of synthesizing cytokines, tendon cells may play a critical role in tendon healing at early time points. Facing the widespread use the bias of cox-2 inhibitors on these immunologic processes has to be checked. Activating matrix destructive enzymes, cytokines appear to be crucial for connective tissue remodelling and graft stability after ACL reconstruction