Tissue expansion is a technique used by plastic and restorative surgeons to cause the body to grow additional skin, bone or other tissues. For example, distraction osteogenesis has been widely applied in lower limb surgery (trauma / congenital), and congenital upper limb reconstruction (e.g. radial dysplasia). This complex and tightly regulated expansion process can thus far only be optimised by long-term animal or human experimentation. Here the intent is to develop an in vitro model of tissue expansion that will allow to both optimise the extension regime (µm/h, continuous/ intermittent) and investigate using proteomic techniques which molecular pathways are involved in its regulation. Cells cultured onto sheets of polymer (PCL) can be stretched at very low, adjustable speeds, using a stepper motor and various 3D printed and laser cut designs. The system utilises plastic flow of the polymer, enabling the material to stay extended upon strain being released. Tensile tests have displayed the plastic behaviour of the polymer sheet when stretched, and digital image correlation (DIC) has been used to analyse homogeneity of the strain field. Further analysis involving nuclear localisation of yes-associated protein (YAP) aims to link cell response to this strain field. Nuclear orientation analysis has demonstrated a morphological response to strain (1 mm/day) in comparison to not being stretched, and this is in the process of being linked to nanoscale changes of the substrate (using atomic force microscopy) during the stretching regime. Future work will identify how strain is affecting the cell cycle, before a mass tagging approach is used to identify protein changes induced by strain

Objectives. The present study describes a novel technique for revitalising allogenic intrasynovial tendons by combining cell-based therapy and mechanical stimulation in an ex vivo canine model. Methods. Specifically, canine flexor digitorum profundus tendons were used for this study and were divided into the following groups: (1) untreated, unprocessed normal tendon; (2) decellularised tendon; (3) bone marrow stromal cell (BMSC)-seeded tendon; and (4) BMSC-seeded and cyclically stretched tendon. Lateral slits were introduced on the tendon to facilitate cell seeding. Tendons from all four study groups were distracted by a servohydraulic testing machine. Tensile force and displacement data were continuously recorded at a sample rate of 20 Hz until 200 Newton of force was reached. Before testing, the cross-sectional dimensions of each tendon were measured with a digital caliper. Young’s modulus was calculated from the slope of the linear region of the stress-strain curve. The BMSCs were labeled for histological and cell viability evaluation on the decellularized tendon scaffold under a confocal microscope. Gene expression levels of selected extracellular matrix tendon growth factor genes were measured. Results were reported as mean ± SD and data was analyzed with one-way ANOVAs followed by Tukey’s post hoc multiple-comparison test. Results. We observed no significant difference in cross-sectional area or in Young’s modulus among the four study groups. In addition, histological sections showed that the BMSCs were aligned well and viable on the tendon slices after two-week culture in groups three and four. Expression levels of several extracellular matrix tendon growth factors, including collagen type I, collagen type III, and matrix metalloproteinase were significantly higher in group four than in group three (p < 0.05). Conclusion. Lateral slits introduced into de-cellularised tendon is a promising method of delivery of BMSCs without compromising cell viability and tendon mechanical properties. In addition, mechanical stimulation of a cell-seeded tendon can promote cell proliferation and enhance expression of collagen types I and III in vitro. Cite this article: J. H. Wu, A. R. Thoreson, A. Gingery, K. N. An, S. L. Moran, P. C. Amadio, C. Zhao. The revitalisation of flexor tendon allografts with bone marrow stromal cells and mechanical stimulation: An ex vivo model revitalising flexor tendon allografts. Bone Joint Res 2017;6:179–185. DOI: 10.1302/2046-3758.63.BJR-2016-0207.R1

Ligament fibroblasts must be mechanosensitive and possess sufficient adaptability to a novel mechanomilieu ensuring the permanent load capacity of the tissue. Once mechanoreceptors are activated, the fibroblasts react with a specific signal transmission (mechanotransduction), which ultimately leads to an adaption of their cytoskeletal organization and protein synthesis. However, the cellular response of anterior cruciate ligament (ACL) fibroblasts to cyclic mechanical stretching is still unclear. Hence, this study should allow a deeper understanding of the reaction profile of mechanically stretched ACL cells in two- (2D) and three-dimensional (3D) biomaterial-free and biomaterial cultures with respect to cell survival, size, orientation, migration and distribution. For the 2D approach consisting of monolayers with 6000 lapine (L) ACL cells per cm2 and for the 3D cultures using preformed LACL cell spheroids (2.5–4/cm2) with 25.000 cells per spheroid, silicone chambers were coated with geltrex and statically colonized with the LACL cells for 24 h before cyclically stretched for 48 h (14 percent uniaxial stretch). A second approach using 3D scaffold cultures was performed which were seeded dynamically for 24 h with LACL cells before cyclically stretched in a novel custom-made mechanostimulator. The scaffolds [polylactic acid (PLA) and polycaprolactone (PCL)] were functionalized with 10 percent gas fluorination and a collagen foam. Scaffolds (120 mm2) were precolonized dynamically with an LACL cell suspension (1 mio cells/mL) for 24 h before stretched for 72 h (4 percent uniaxial stretch). Cell vitality and numbers were monitored. The cytoskeleton orientation was shown by cytochemistry (F-actin) and evaluated (ImageJ). Cell proliferation, based on the DNA content was measured. Cell viability in stretched samples (2D, 3D and scaffold) remained above 90 percent. Stretching on the silicone chambers led to increased cell counts, length and significantly higher colonized areas than in unstretched controls. Higher numbers of LACL cells migrated out of the 3D spheroids under stretching conditions. In response to intermittent stretching, cells oriented in a 70 degrees' angle against the stretch direction in silicone chambers, whereas cell arrangement was more compact on the threads of the scaffolds than in unstretched cultures. In summary, stretching induced a rapid (48 h) cell and cytoskeletal alignment in 2D as well as in 3D cultures. The natural ACL is characterized by a strongly uniaxial cell and extracellular matrix organization which might be achieved in tissue engineered constructs by a suitable cyclic stretching protocol in future

Lumbar diseases have become a major problem affecting human health worldwide. Conservative treatment of lumbar diseases is difficult to achieve ideal results, and surgical treatment of trauma, complications, it is imperative to develop a new treatment method. This study aims to explore the regulatory mechanism of cartilage endplate ossification caused by abnormal stress, and design intervention targets for this mechanism, so as to provide theoretical reference for the prevention and treatment of lumbar degeneration. In vivo, we constructed spinal instability model in mice. In vitro, we used a mechanical tensile machine to simulate the abnormal stress conditions of the endplate cartilage cells. Through the high-throughput sequencing, we found the enrichment of Hippo signaling pathway. As YAP is a key protein in the Hippo signaling pathway, we then created cartilaginous YAP elimination mice (Col2::YAPfl/fl). The lumbar spine model was constructed again in these mice for H&E, SOFG and immunofluorescence staining. In vitro lentivirus was used to knock out YAP, immunofluorescence staining, WB and qPCR were performed. Finally, we conducted therapeutic experiments by using YAP agonist and AAV5 carrying YAP plasmids. We collected 8w samples from C57/BL6 mice after modeling. We found ossification of the endplate in mice similar to human disc degeneration. High-throughput sequencing of stretched cells demonstrated high enrichment of the Hippo signaling pathway. By immunofluorescence staining, it was confirmed that Col-II decreased and Col-X gradually increased in the endplate cartilage of mice. This was also confirmed at 7 days after an in vitro stretch of 5% and 12%. Meanwhile, we found that cartilaginous YAP elimination mice developed very severe endplate degeneration. However, the endplate was well protected by intraperitoneal injection of YAP agonist or AAV5-YAP endplate injection, and the results in vitro were consistent with that. In the process of cartilaginous ossification, abnormal stress regulates Col10a1 to promote cartilage endplate ossification through Hippo signaling pathway mediated YAP, and we expect to find potential drug targets for treatment through this mechanism

Background. Balance impairment and falling are of the major health problems in elderly individuals. The ability to maintain standing balance influences the risk of falling while performing everyday activities. Postural control is the base of balance that is the result of collaboration of visual, vestibular and somatosensory systems. Single leg stance test is a simple clinical method to evaluate static balance. In this test, the center of body mass is on a small support level and need to make corrective movements to create balance by postural control system. Kinesiotaping and stretching of ankle plantar flexor muscles used in physical therapy are effective in improvement of postural balance. Kinesiotaping is effective in maintaining balance by activates cutaneous receptors and promoting alpha motor neuron stimulation. Moreover, stretching is a common treatment used to prevent muscle shortness and increase the range of motion that improves the balance. Aim. Therefore the aim of current study was to compare the effects of these two methods in elderly women and men on ankle plantar flexor muscles which are effective to maintain postural status. Materials and Methods. In a single blind randomized clinical trial, 20 elderly male and 20 elderly female were assigned into 2 groups of kinesiotaping and stretching. Inhibitory Y shape tape was applied on the gastrocnemius in first group. In the stretching group, the muscle was stretched for 60 seconds by 4 times. The static balance was examined before and after the interventions by using single leg stance test. In this test, the subjects were asked to stand bare foot on dominant limb and cross their arms over chest. A maximum time for this test is 30 seconds. The researcher who was assessing balance was unaware to the intervention group. Results. According to paired t-test, Despite progress in time to stance on one leg after the interventions, the changes were not significant (P>0.05). Although the trend was more pronounced in the stretching group, independent t-test results showed no significant difference between groups (P>0.05). While in any of the treatment groups, there was no difference between men and women (P=0.1 and P=0.7 for kinesiotaping and stretching group, respectively). Conclusion. While the results did not show any significant difference after the intervention, but Increasing of the test time, which means improving the balance of participants, is evident. However, changes in the stretching group were more pronounced. Keyword. Single leg stance test, Elderly, Stretching, kinesiotaping, Plantar flexor muscle

The need to accurately forecast the injury burden has never been higher. With an aging, ever expanding trauma population and less than half of the beds available compared to 1990, the National Health Service (NHS) is stretched to breaking point. 1,2. . We utilised a dataset of 22,585 trauma patients across the four countries of the United Kingdom (UK) admitted to 83 hospitals between 22/08/22 – 16/10/22 to determine whether it is possible to predict the proportionality of injuries treated operatively within orthopaedic departments based on their number of Neck of Femur fracture (NOF) patients. More operations were performed for elderly hip fractures alone than for the combined totals of the next four most common fractures: ankle, distal radius, tibial shaft and forearm (6387 vs 5922). Conversely, 10 out of the 13 fracture types were not encountered by at least one hospital and 93% of hospitals encountered less than 2 fractures of a certain type. 60% trauma is treated within Trauma Units (TUs) however, per unit, Major Trauma Centres (MTCs) treat approximately 43% more patients. After excluding NOF, lower limb fractures accounted for approximately 57% of fractures in all countries and ankle and distal radius fracture combined comprised more than 50% in 74% of regions. The number of hip fractures seen on average by an individual unit remains relatively consistent as does the regional variation of any given fracture; resultantly, it is possible to predict injury proportionality based off a unit's hip fracture numbers. This powerful tool could transform both resource allocation and recruitment

Introduction. Regular, repeated stretching increases joint range of movement (RoM), however the physiology underlying this is not well understood. The traditional view is that increased flexibility after stretching is due to an increase in muscle length or stiffness whereas recent research suggests that increased flexibility is due to modification of tolerance to stretching discomfort/pain. If the pain tolerance theory is correct the same degree of micro-damage to muscle fibres should be demonstrable at the end of RoM before and after a period of stretch training. We hypothesise that increased RoM following a 3 weeks hamstrings static stretching exercise programme may partly be due to adaptive changes in the muscle/tendon tissue. Materials and Methods. Knee angle and torque were recorded in healthy male subjects (n=18) during a maximum knee extension to sensation of pain. Muscle soreness (pain, creatine kinase activity, isometric active torque, RoM) was assessed before knee extension, and 24 and 48 hours after maximum stretch. An exercise group (n=10) was given a daily home hamstring stretching programme and reassessed after 3 weeks and compared to a control group (n=8). At reassessment each subject's hamstring muscles were stretched to the same maximum knee extension joint angle as determined on the first testing occasion. After 24 hours, a reassessment of maximum knee extension angle was made. Results. At the start of the study RoM was 71.3 ± 10.0 degrees and there was no significant difference between groups. After 3 weeks stretching RoM increased significantly (p=0.01) by 9 degrees; the control group showed no change. Stiffness did not differ for either group. Pain score and RoM were the most sensitive markers of muscle damage and were significantly changed 24 and 48 hours after the initial stretch to end of range, (p<0.005) and (p=0.004) respectively. Discussion. The results show that a 3 week stretching programme causes muscle adaptation resulting in an increase in the extensibility of the hamstring muscle/tendon unit but no change in stiffness. The lack of evidence of muscle damage suggests that participants in the stretching group are likely to have undergone a physical change/adaptation rather than simply an increase in pain threshold

Tendinopathy is the most frequent musculoskeletal disease that requires medical attention. Mechanical overload has been considered as a key driver of its pathology. However, the underline mechanism on how overload induces tendinopathy and inflammation is unclear. Extracellular mitochondria (EM) are newly identified as cell-to-cell communicators. The aim of this study is to elucidate the role of mitochondria in overload-induced inflammation. We performed three-dimensional uniaxial stretching to mouse tendon organoid in bioreactors. Cyclic strain of uniaxial loadings included underload, normal load, and overload, according to previous work. We then harvested microvesicles including EM, from the bioreactor by differential centrifugation and evaluated their characteristics by flow cytometry and super-resolution confocal microscopy. Raw 264.7 mouse macrophage cell line was used for chemotaxis assay in a Boyden Chamber System with Magnetic-Activated Cell Sorting Technology. EM induced cytokines secretion by macrophages was analyzed by a bead-based multiplex assay panel. N-Acetyl-L-cysteine (NAC) was used as the antioxidant to tendon organoid to regulate mitochondrial fitness. We showed mechanical load induced tendon organoid to release microvesicles including mitochondria. The size of microvesicles is mainly in the range from 220nm to 880nm. More than 75% of microvesicles could be stained by PKH26, confirming they were with lipophilic membrane. Super-resolution confocal microscopy identified two forms of mitochondria, including mitochondria encapsulated in vesicles and free mitochondria. Overload led to the degeneration of the organoid and induced microvesicles release containing most EM. Chemotaxis assay showed that EM from overloaded tendon organoid induced macrophages chemotaxis. In addition, microvesicles extracted from overloaded tendon organoid induced the production of proinflammatory cytokines including IL-6, KC (Keratinocyte-Derived Chemokine) and IL-18. NAC treatment to tendon cells could attenuate overload-induced macrophage chemotaxis. Overload induces EM releasing from tendon cells, which leads to chemotaxis of macrophages toward tendon, resulting in induction of inflammation

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

Abstract. Objectives. The need to accurately forecast the injury burden has never been higher. With an aging, ever expanding trauma population and less than half of the beds available compared to 1990, the National Health Service (NHS) is stretched to breaking point1,2. Resultantly, we aimed to determine whether it is possible to predict the proportionality of injuries treated operatively within orthopaedic departments based on their number of Neck of Femur fracture (NOF) patients reported both in our study and the National Hip Fracture Database (NHFD). Methods. We utilised the ORthopaedic trauma hospital outcomes - Patient operative delays (ORTHOPOD) dataset of 22,585 trauma patients across the four countries of the United Kingdom (UK) admitted to 83 hospitals between 22/08/22 – 16/10/22. This dataset had two arms: arm one was assessing the caseload and theatre capacity, arm two assessed the patient, injury and management demographics. Results. Our results complied with the data reported to the NHFD in over 80% of cases for both the 2022 and five-year average reported numbers. More operations were performed for elderly hip fractures alone than for the combined totals of the next four most common fractures: ankle, distal radius, tibial shaft and forearm (6387 vs 5922). Conversely, 10 out of the 13 fracture types were not encountered by at least one hospital and 93% of hospitals encountered less than 2 fractures of a certain type.60% of trauma is treated within Trauma Units (TUs) however, per unit, Major Trauma Centres (MTCs) treat approximately 43% more patients. Similarly, 11 out of the 14 fracture types examined presented more frequently to a MTC however 3 of the most common fractures had a preponderance for TUs (elderly hip, distal radius and forearm fractures). After excluding NOF, lower limb fractures accounted for approximately 57% of fractures in all countries and ankle and distal radius fracture combined comprised more than 50% in 74% of regions. There were few outliers across the study regarding number of fractures treated by a hospital with tibial shaft fractures demonstrating the highest number of outliers with 4. Conclusions. The number of hip fractures seen on average by an individual unit remains relatively consistent as does the regional variation of any given fracture; resultantly, it is possible to predict injury proportionality based off a unit's hip fracture numbers. This powerful tool could transform both resource allocation and recruitment. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Numerous implanted hip and knee joint arthroplasties have to be replaced due to early or late loosening of the implant, a failure of osteointegration with fibrous tissue at the bone-implant-interface. This could be counteracted by ensuring that cells which attach to the implant surface differentiate towards bone cells afterwards. For this reason, human mesenchymal stem cells (hMSCs) will be included in this study. These cells are naturally available at the bone-implant-interface, multipotent and therefore ideal to study the osteoinductivity of a material. The goal of this pilot study was to test the cell response towards three different titanium grades with a novel surface structuring, as a first step towards achieving an improved implant surface for enhanced osteointegration. Disk-shaped titanium scaffolds with a diameter of 12 mm and a height of 1.2 mm were used. The surface topography (500 µm × 500 µm × 300 µm pores) was generated via laser treatment of the surface. By using nanosecond pulsed laser technique, a rough surface with micro- and nanostructural (titanium droplets) features was automatically formed. Three different batches made of commercially pure titanium grades 1 and 2 (Ti1/Ti2) or Ti6Al4V alloy grade 5 (Ti5) were produced. Four cell types were analysed on these batches: primary hMSCs from one donor (m, 25 y), periosteum derived cells (PDCs), human osteoblasts (hOBs) and periodontal ligament cells (PDLs). Cells were seeded on Ti1, Ti2 and Ti5 scaffolds in triplicates. Resazurin assay to examine cell viability was conducted with all cell types. Measurements were executed on several days after seeding, from day one up to day 14. Actin staining as well as live/dead staining was performed with hMSCs cultured on titanium for 1, 3, 5 or 7 days. The cell viability assay revealed early turning points of growth for osteogenic hOBs (day 3) and PDCs (day 7). HMSCs grew steadily on the material and non-osteogenic PDLs stayed in plateau throughout the cultivation period. With respect to the material, cells demonstrated better proliferation on Ti1 and Ti2 than on Ti5. Live/dead staining showed a high survival rate of hMSCs at each time point and on all three titanium grades, with a neglectable number of dead cells. Actin staining confirmed an enhanced spreading and stretching of hMSCs on Ti1 and Ti2 compared to hMSCs on Ti5. Our pilot data indicates that cells react to different titanium compositions, revealed by increased proliferation on commercially pure titanium (Ti1/2). Furthermore, our results demonstrate that osteogenic cells prefer the novel surface structuring in comparison to non-osteogenic PDL cells, which stayed in plateau. The turning points of growth (hOBs/PDCs) suggest an osteosupportiveness of the surface. Although hMSCs did not show a turning point in growth, their growth was steady and resulted in the highest number of cells along with a well stretched morphology. Due to their good proliferation and response to the material, hMSCs are currently being used for evaluating the osteogenic potential of the novel scaffolds

Shortening of patellar tendon after total knee arthroplasty (TKA) was previously reported by several studies. Its etiology still remains controversial. Patellar tendon shortening, a direct cause of patella baja, has a dramatic negative impact in terms of clinical outcomes after TKA. Main objective of this study is to assess the feasibility of utilizing a different technique with Ultrasound that is easy to use, cost-effective and able to eliminate the problem of differential magnification occurring in other techniques which count on standard x-rays and to establish the correlation between clinical outcomes and changes in patellar tendon length and thickness after TKA. The study was designed as prospective cohort and, after a minimum of 4-year-follow up period, 47 knees of 24 patients who had undergone primary TKA without patellar resurfacing were included in the study. All patients were scored with Kujala and HSS scores and all patellar tendons were evaluated with USG regarding their length and thickness. We used conventional grey-scale ultrasound imaging (US) to determine any changes in patellar tendon morphology. All cases were evaluated by the same radiologist. The patellar tendon was examined with the knee in 30° flexion. The flexion angle helped to stretch the extensor mechanism and avoid anisotropy (concavity) of the patellar tendon. The transducer was placed along the long axis of the tendon. The patellar tendon was initially examined in the longitudinal plane in order to measure the total length. Then, total length was divided into three parts and sagittal thickness was calculated at the proximal, median, and distal thirds of the patellar tendon. Both the length and thickness of the tendon were measured before surgery and at the 4th year of follow-up. Of the 47 knees that were included in our study, the mean pre-operative and postoperative length of the patellar tendon was 40.78±6.15 mm and 35.93±4.52 mm. Our results suggested significant shortening of the patellar tendon after primary TKA surgery (p<0.05). Intergroup analysis suggested that reduced sagittal thickness in the proximal third of the tendon was more strongly correlated with an increase in functional outcomes (p<0.05). Our results suggested no significant difference in clinical outcome scores between patients with increased or decreased length of the patellar tendon after TKA (p>0.05). We suggest that determining morphologic changes in sagittal thickness as well as length is important in explaining some of the ambiguous causes of anterior knee pain and impaired clinical outcomes after TKA. More accurate documentation of morphologic changes in the patellar tendon after TKA will certainly help to develop new techniques by surgeons or avoid some existing routines that may harm the tendon. USG is a feasible method for evaluating patellar tendon morphology after TKA but more future studies are needed

Adductor strain is a common injury among football players. The adductor muscle group contains the three adductor muscles. (adductor longus, magnus and brevis) Adductor longus muscle is a triangular-shaped long muscle. This muscle originates from the superior ramus of the pubic bone and inserted into the middle part of the linea aspera. Adductor longus muscle is the most commonly injured muscle of adductors. Sudden acceleration, jumping, stretching, and kicking the ball are common causes of an adductor injury. Adductor muscle strains can result in missed playing time for football players. We present a 26-year-old man soccer player with pain in the left groin and proximal thigh. The symptoms had started during training and after kicking the ball with left foot (dominant side), he felt an acute pain in the groin region and proximal thigh. Despite the injury, he managed to finish the training. The team physician examined the patient immediately after training. The range of motion of both hip joints was in normal ranges and mild pain with adduction. There was a palpable mass at the inner proximal thigh during contraction of adductor muscles. There was no history of groin pain or adductor problems before this injury. Conventional radiographs showed no osseous abnormalities. 36 hours after the injury, MRI revealed acute grade IIB strain in the left adductor longus muscle, including both superior and inferior parts of the muscle. A hematoma was observed in the superior part of the left adductor muscle, with a craniocaudal length of 42 millimeters. There was an adductor muscle strain with hyperintensity extending for a craniocaudal length of approximately 12 centimeters involving more than 50% crosses sectional diameter of the muscle belly. Conservative treatment started immediately, consisting of cold therapy and soft tissue massage. Compression of the injured tissue using a 15-cm elastic bandage roll is done to limit bleeding and provide support. Iced water machine (Game Ready) was used. The team physician examined the player every day and prescribed physiotherapy protocol daily. Additionally, short interval follow-up MRI is used to evaluate the injury. (After 7 and 14 days of the injury) No injection was performed. The player is able to return to play immediately, despite MRI's strain images. The player started straight running 5 days later and joined to team training 8 days later and played 90 minutes-league-match 12 days after injury without any pain. No injection was performed. The player is able to return to play immediately, despite MRI's strain images. The player started straight running 5 days later and joined to team training 8 days later and played 90 minutes-league-match 12 days after injury without any pain. MRI is a useful technique in diagnosing trauma in football players presenting with groin pain. In this case, to estimate time-to-return-to-play, MRI alone is not strong evidence. MRI is a good option for follow up, but anamnesis and clinical examination is not inferior to diagnostic imaging

In-situ assessment of collateral ligaments strain could be key to improving total knee arthroplasty outcomes by improving the ability of surgeons to properly balance the knee intraoperatively. Ultrasound (US) speckle tracking methods have shown promise in their capability to measure in-situ soft tissue strain in large tendons but prior work has also highlighted the challenges that arise when attempting to translate these approaches to the in-situ assessment of collateral ligaments strain. Therefore, the aim of this project was to develop and validate an US speckle tracking method to specifically assess in-situ strains of both the MCL and LCL. We hypothesize that coefficients of determination (R. 2. ) would be above 0.90 with absolute differences below 0.50% strain for the comparison between US-based and the reference strain, with better results expected for the LCL compared with the MCL. Five cadaveric legs with total knee implants (NH019 2017-02-03) were submitted to a varus (LCL) and valgus (MCL) ramped loading (0 – 40N). Ultrasound radiofrequency (rf) data and reference surface strains data, obtained with 3D digital image correlation (DIC), were collected synchronously. Prior to processing, US data were qualitatively assessed and specimens displaying substantial imaging artefacts were discarded, leaving five LCL and three MCL specimens in the analysis. Ultrasound rf data were processed in Matlab (The MathWorks, Inc., Natick, MA) with a custom-built speckle tracking approach adapted from a method validated on larger tendons and based on normalized cross-correlation. Digital image correlation data were processed with commercial software VIC3D (Correlated Solutions, Inc., Columbia, SC). To optimize speckle tracking, several tracking parameters were tested: kernel and search window size, minimal correlation coefficient and simulated frame rate. Parameters were ranked according to three comparative measures between US- and DIC-based strains: R. 2. , mean absolute error and strains differences at 40N. Parameters with best average rank were considered as optimal. To quantify the agreement between US- and DIC-based strain of each specimen, the considered metrics were: R. 2. , mean absolute error and strain differences at 40N. The LCL showed a good agreement with a high average R. 2. (0.97), small average mean absolute difference (0.37%) and similar strains at 40N (DIC = 2.92 ± 0.10%; US = 2.99 ± 1.16%). The US-based speckle tracking method showed worse performance for the MCL with a lower average correlation (0.55). Such an effect has been observed previously and may relate to the difficulty in acquiring sufficient image quality for tracking the MCL compared to the LCL, which likely arises due to structural or mechanical differences; notably MCL is larger, thinner, more wrapped around the bone and stretches less. However, despite these challenges, the MCL tracking still showed small average mean absolute differences (0.44%) and similar strains at 40N (DIC = 1.48 ± 0.06%; US = 1.44 ± 1.89%). We conclude that the ultrasound speckle tracking method developed is ready to be used as a tool to assess in-situ strains of LCL. Concerning the MCL strain assessment, despite some promising results in terms of strain differences, further work on acquisition could be beneficial to reach similar performance

Objectives. Temperature is known to influence muscle physiology, with the velocity of shortening, relaxation and propagation all increasing with temperature. Scant data are available, however, regarding thermal influences on energy required to induce muscle damage. Methods. Gastrocnemius and soleus muscles were harvested from 36 male rat limbs and exposed to increasing impact energy in a mechanical test rig. Muscle temperature was varied in 5°C increments, from 17°C to 42°C (to encompass the in vivo range). The energy causing non-recoverable deformation was recorded for each temperature. A measure of tissue elasticity was determined via accelerometer data, smoothed by low-pass fifth order Butterworth filter (10 kHz). Data were analysed using one-way analysis of variance (ANOVA) and significance was accepted at p = 0.05. Results. The energy required to induce muscle failure was significantly lower at muscle temperatures of 17°C to 32°C compared with muscle at core temperature, i.e., 37°C (p < 0.01). During low-energy impacts there were no differences in muscle elasticity between cold and warm muscles (p = 0.18). Differences in elasticity were, however, seen at higher impact energies (p < 0.02). Conclusion. Our findings are of particular clinical relevance, as when muscle temperature drops below 32°C, less energy is required to cause muscle tears. Muscle temperatures of 32°C are reported in ambient conditions, suggesting that it would be beneficial, particularly in colder environments, to ensure that peripheral muscle temperature is raised close to core levels prior to high-velocity exercise. Thus, this work stresses the importance of not only ensuring that the muscle groups are well stretched, but also that all muscle groups are warmed to core temperature in pre-exercise routines. Cite this article: Professor A. H. R. W. Simpson. Increased risk of muscle tears below physiological temperature ranges. Bone Joint Res 2016;5:61–65. doi: 10.1302/2046-3758.52.2000484

Ligaments and tendons are connective tissues with a highly hierarchical structure, from collagen fibres, to fibrils and fascicules. Their intricate structural arrangement produces an anisotropic non-linear elastic mechanical behaviour and a complex damage pattern before failure. Recent constitutive models have been developed with all parameters describing the structure of the tissue, with the advantage that they can in theory be measured on the tissue rather than being phenomenologically-derived. This is an ideal framework to model damage as its onset and propagation can be associated to changes in the structure directly. In this preliminary study, the possibility to identify damage mechanisms in the tissue structure using in silico models was analysed for both the anterior cruciate ligament, with fascicules forming a helix with its longitudinal axis, and the patellar tendon, with fascicules co-aligned with its longitudinal axis. Tissues of interest were modelled as cylinders submitted to uniaxial tension. Damage was modelled as either a reduction of collagen volume fraction with increased strain, assuming the number of collagen fibres sustaining load decreases as fibres fail, or a reduction of the modulus of the fibres, assuming pre-failure damage of the fibres. Each damage mechanism was associated with a damage variable with different fibre stretch threshold for damage initiation and assuming linear variation of damage until an arbitrary failure point. The apparent behaviour of the modelled tissues was significantly different as damage thresholds, damage mechanisms, type of fascicules were varied. This preliminary work showed that using a structural constitutive model to describe occurrence and propagation of structural damage in an in silico model of hierarchical connective tissues is a framework that can clearly differentiate at a macroscopic level between different values of damage threshold and different damage mechanisms for tissue with co-aligned or helical fascicules

Daytime spinal loading is twice as long as night time rest, but diurnal disc height changes due to fluid flow are balanced. A direction-dependent permeability of the endplates, favouring inflow over outflow, has been proposed to explain this; however, fluid also flows through the annulus fibrosus. This study investigates the poro-elastic behaviour of entire intervertebral discs in the context of diurnal fluid flow. Caprine discs were preloaded in saline for 24 hours under different levels of static load. Under sustained load, we modulated the disc's swelling pressure by replacing saline for demi-water and back again to saline, both for 24h intervals. We measured the disc height creep and used stretched exponential models to determine the respective time constants. Reduction of culture medium osmolality induced an increase in disc height, and the subsequent restoration induced a decrease in disc height. Creep varied with the mechanical load applied. No direction-dependent resistance to fluid flow was observed. In addition, time constants for mechanical preloading were much shorter than for osmotic loading, suggesting that outflow is faster than inflow. However, a time constant does not describe the actual rate of fluid flow: close to equilibrium fluid flow is slower than far from equilibrium. As time constants for mechanical loading are shorter and daytime loading twice as long, the system is closer to the loading equilibrium than to the unloading equilibrium. Therefore, paradoxically, fluid inflow is faster during the night than fluid outflow during the day

The biomechanical evaluation of tendon repair with collagen-based scaffolds in rat model is a common method to determine the functional outcome of the tested material. We introduced a magnetic resonance imaging (MRI) approach to verify the biomechanical test data. In present study different collagen scaffolds for tendon repair were examined. Two collagen test materials: based on bovine stabilized collagen, chemically cross-linked with oriented collagenous fibres (material 1) and based on porcine dermal extracellular matrix, with no cross-linking (material 2) were compared. The animal study was approved by the local review board. Surgery was performed on male Sprague-Dawley rats with a body weight of 400 ± 19 g. Each rat underwent a 5 mm transection of the right Achilles tendon. The M. plantaris tendon was removed. The remaining tendon ends were re-joined with a 5 mm scaffold of either the material 1 or 2. Each scaffold material was sutured into place with two single stiches (Vicryl 4–0, Ethicon) each end. A total of 16 rats (n= 8 each group) were observed for 28 days follow up. The animals were sacrificed and hind limbs were transected proximal to the knee joint. MRI was performed using a 7 Tesla scanner (BioSpec 70/30, Bruker). T2-weighted TurboRARE sequences with an in-plane resolution of 0.12 mm and a slice thickness of 0.7 mm were analysed. All soft and hard tissues were removed from the Achilles tendon-calcaneus-foot complex before biomechanical testing. Subsequently, the specimens were fixed in a materials testing machine (Z1.0, Zwick, Ulm, Germany) for tensile testing. All tendons were preloaded with 1 N and subsequently stretched at a rate of 1 mm/s until complete failure was observed. Non-operated tendons were used as a control (n=4). After 28 postoperative days, MRI demonstrated that four scaffolds (material 1: n=2, material 2: n=2) were slightly dislocated in the proximal part of hind limb. In total five failures of reconstruction could be detected in the tendon repairs (material 1: n=3, material 2: n=2). Tendons augmented with the bovine material 1 showed a maximum tensile load of 57.9 ± 17.9 N and tendons with porcine scaffold material 2 of 63.1 ± 19.5 N. The native tendons demonstrated only slightly higher loads of 76.6 ± 11.6 N. Maximum failure load of the tendon-scaffold construct in both groups did not differ significantly (p < 0.05). Stiffness of the tendons treated with the bovine scaffold (9.9 ± 3.6 N/mm) and with the porcine scaffold (10.7 ± 2.7 N/mm) showed no differences. Stiffness of the native healthy tendon of the contralateral site was significantly higher (20.2 ± 6.6 N/mm, p < 0.05). No differences in the mechanical properties between samples of both scaffold groups could be detected, regardless of whether the repaired tendon defect has failed or the scaffold has been dislocated. The results show that MRI is important as an auxiliary tool to verify the biomechanical outcome of tendon repair in animal models

Introduction. Energy storing tendons such as the equine superficial digital flexor tendon (SDFT) stretch and recoil with each stride and therefore require a high degree of compliance compared to tendons with a purely positional function, such as the equine common digital extensor tendon (CDET). This extra extensibility is provided by a specialised interfascicular matrix (IFM), which provides greater sliding and recoil between adjacent fascicles in energy storing tendons. However, the composition of the IFM remains largely undefined. We hypothesised that the IFM in the SDFT has a distinct composition, with a greater abundance of proteoglycans and elastin which facilitate extension and recoil. Materials and Methods. Transverse and longitudinal sections were cut from the mid-metacarpal regions of SDFTs and CDETs from 5 horses aged 3–7 years. Sections were stained using Alcian blue/Periodic acid Schiff to detect proteoglycans, elastic Van Giesson's to detect elastin, and immunohistochemistry was performed using antibodies for decorin, biglycan, fibromodulin, lumican and lubricin. Resultant images were graded by blinded observers to assess staining intensity in the IFM and fascicular matrix (FM), and statistical significance determined using ANOVA. Results. Overall proteoglycan abundance was significantly greater in the SDFT than the CDET (p<0.0001). In the SDFT, overall proteoglycan staining was greater in the FM than the IFM (p<0.0001). Elastin content was greater in the SDFT, where it was predominantly localised to the IFM. Fibromodulin staining was significantly greater in the CDET than the SDFT (p<0.05), whereas decorin staining was greater in the SDFT (p<0.05). In the SDFT, lubricin and biglycan staining were significantly greater in the IFM than the FM (p<0.05). Lumican staining was significantly greater in the CDET IFM than in the SDFT IFM (p<0.01). Discussion. As hypothesised, the IFM has a specialised composition in the SDFT, with a greater abundance of elastin, lubricin and biglycan. It is likely that the greater abundance of lubricin facilitates sliding between fascicles, whereas the localisation of elastin to the IFM is likely to provide the superior ability to recoil. The differential abundance of decorin, fibromodulin and lumican across tendon regions and types may reflect the different roles of these proteoglycans in tendon

Introduction. Whilst all tendons connect muscle to bone, energy storing (ES) tendons, such as the equine superficial digital flexor tendon (SDFT) play an additional role, storing energy to improve locomotion efficiency. ES tendons experience significantly higher strains during locomotion than other positional tendons, such as the common digital extensor tendon (CDET). Our previous work has demonstrated that the interfascicular matrix (IFM) is more extensible in ES tendons, allowing ES tendons to stretch further during use. However, ES tendons must also recoil efficiently to perform their energy storing function. It has not been yet established if the IFM is able to recoil and recover after loading. Thus, this project aimed to determine the recoil capacity of the IFM in both the ES and positional tendons from young and old horses. Materials and Methods. Five young (3–7 years) and five old (17–20 years) SDFTs and CDETs were dissected from the forelimbs of 10 euthanized horses. Groups of 2 intact fascicles (bounded by IFM) were dissected from each tendon. Using a custom-made dissection rig and a polarised light microscope, samples were dissected, and the opposing end of each fascicle was cut transversely, leaving a 10 mm length of IFM. IFM samples were tested in shear, by preconditioning with 10 loading cycles then pulling to failure. The hysteresis and stress relaxation that occurred during preconditioning were calculated. Results. The IFM was able to recoil in both SDFT and CDET tendons. However, hysteresis and stress relaxation were both significantly higher in CDET than SDFT IFM samples. The SDFT IFM was less stiff than the CDET IFM, but the SDFT IFM stiffness increased with ageing. Discussion. The IFM showed reversible deformation behaviour, with a greater ability to recoil in the SDFT. Changes with ageing were only evident in the SDFT, where the IFM became less fatigue resistant and stiffer. These results further indicate that ES tendons have a specialised IFM to facilitate efficient function, and changes in the mechanical properties of this matrix with ageing may predispose these tendons to injury