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

The use of passive stretching of the elbow after arthrolysis is controversial. We report the results of open arthrolysis in 81 patients. Prospectively collected outcome data with a minimum follow-up of one year were analysed. All patients had sustained an intra-articular fracture initially and all procedures were performed by the same surgeon under continuous brachial plexus block anaesthesia and with continuous passive movement (CPM) used post-operatively for two to three days. CPM was used to maintain the movement achieved during surgery and passive stretching was not used at any time. A senior physiotherapist assessed all the patients at regular intervals. The mean range of movement (ROM) improved from 69° to 109° and the function and pain of the upper limb improved from 32 to 16 and from 20 to 10, as assessed by the Disabilities of the Arm Shoulder and Hand score and a visual analogue scale, respectively. The greatest improvement was obtained in the stiffest elbows: nine patients with a pre-operative ROM < 30° achieved a mean post-operative ROM of 92° (55° to 125°). This study demonstrates that in patients with a stiff elbow after injury, good results may be obtained after open elbow arthrolysis without using passive stretching during rehabilitation

The most considerable cause of nerve root damage are compression force and stretch force. Many researchers had reported about experimental study of the compression force, but it is difficult to find the report describing the stretch force to the nerve roots. The purpose of this study is to evaluate the physiological reaction of nerve roots of rats nuder stretch force. The nerve roots were prepared from the cauda equina of 8 Wister rats (weight: 300 – 400g). We investigated the changes in threshold and action potential of the nerve roots under stretch force and compression force. The threshold of the nerve roots increased and action potential decreased in parallel with stretch force. Also, the threshold and action potential recovered after releasing the stretch force. On the other hand, by compression force, the action potential decreased parallel with compression force, but the threshold did not change with compression force. Ten minutes after releasing compression force, the action potential did not recover as much as before, and the threshold increased rather than control. The different physiological reactions that occurred between compression force and stretch force are hard to explain by circulation insufficiency, as previously reported (hypoxemia and lack of nutrition). We considered that the etiology of the stretch force might be a change in internal pressure of nerve roots and a structural change in nerve cells. The physiological reaction of the nerve root under stretch force differed from that under compression force and recovered from the damage after release from stretch force

Aim: To measure the percentage increase in length of the donor graft during rehabilitation from 0 degrees to 120 degrees of elbow flexion and to compare this with the end range strength. Method: During the troids procedure four metal skin-clips were inserted at the proximal and distal margins of the proximal and distal tibialis posterior tendon weaves creating three intervals for measurement. Lateral x-rays of the humerus with the tube distance at 100cms were taken after five weeks of plaster immobilisation before elbow flexion commenced at a maximum rate of 15 degrees per week. X-rays were repeated when 60 degrees and 120 degrees of flexion obtained and when possible six months post surgery. Elbow torque was measured by the Troidometer throughout the range of motion at similar time intervals. Interval measurement was by a Vidar VRX 12 digital scanner. The Paired T test was used for statistical analysis. Results: Sixteen arms (nine patients) were entered into the study but complete rehabilitation data were available from only 12 arms and late data from only four. There was a 12.3% average increase between 0 degrees and 60 degrees (range six to 20.6 degrees) and a further 3% increase from 60 degrees to 120 degrees (range −6 degrees to 21 degrees). The most stretch occurred in the distal segment and in bilateral arms the percentage of stretch was similar for each arm. There was no correlation between the percentage of stretch and end range torque or lag. Conclusions: The Troids transfer restores elbow extension for tetraplegics but an extensor lag often develops which is thought to be from stretching of the donor tendon graft. This study confirmed that tendon stretch occurs but there was wide variation among individuals although similar for each arm in bilateral procedures. An average of 75% of stretch occurred during the 0 degrees to 60 degrees mobilisation. We concluded that tendon stretch is inevitable but is not a major contributor to end range weakness or lag

1. Forty-seven tibial nerves of rabbits were stretched, twenty-four gradually by the Instron machine and twenty-three suddenly by dropping a load. The stretched nerves were examined histologically throughout their length. 2. Nerve trunks possess a high degree of elasticity, which is mainly a feature of the epineurium. 3. The initial elongation of the nerve is due to extension of the epineurium and straightening of the funiculi and of the nerve fibres. Such elongation is "physiological" in the sense that it does not affect the nerve fibres. 4. The first structure to be ruptured during stretching is the epineurium ; this occurs when the nerve trunk has reached its limit of elasticity. 5. Before rupture of the epineurium the damage to the nerve fibres is either neurapraxia or axonotmesis, because the endoneurial sheaths and Schwann tubes remain intact. 6. Beyond the limit of elasticity very severe damage of the nerve trunk occurs; all elements of the nerve may be ruptured. If less violent force is applied, some funiculi may survive. The longitudinal extent of the lesion is always great, reaching 2 to 5 centimetres in the rabbit

Biomechanical stimuli have fundamental roles in the maintenance and remodeling of ligaments including collagen gene expressions. Mechanical stretching signals are mainly transduced by cell adhesion molecules such as integrins. However, the relationships between stress-induced collagen expressions and integrin-mediated cellular behaviors are still unclear in anterior cruciate ligament cells. Human ACL cells were harvested from ligament samples donated by patients who underwent total knee arthroplasties with informed consents. Interface cells were isolated from the 5-mm-end of ACL. Midsubstance cells were cultured from the middle part of ACL. The cells were seeded onto stretch chambers (2Ä−2 cm, 50,000 cells/chamber) and uni-axial cyclic mechanical stretch (0.5 Hz, 7%) was applied for 2 h using a ST140. RNA samples were reverse-transcripted and quantitative real-time RT-PCR analysis were performed. To inhibit the function of integrin alphaVbeta3 subunit or alpha5 in stretching experiments, anti-human integrin alphaVbeta3 and alpha5 functional blocking antibodies (alphaVbeta3: 20 mg/ml, alpha5: 4 mg/ml) were used. To investigate the cellular attachments responding to mechanical stretch, we observed the distribution of integrins and stress fibers in both ACL cells. The shape of midsubstance cells showed spindle and fibroblastic cellular morphologies. On the other hand, the interface cells displayed chondroblastic appearances such as small and triangular morphologies. The expressions of COL1A1, COL2A1, and COL3A1 genes were detected in the tissue RNAs of interface zones. However, these expressions were decreased in cultured interface cells. In midsubstance cells, the expression of COL1A1 gene was equally detected in both tissues and cultured cells. COL3A1 gene expression was maintained in cultured midsubstance cells. These results indicated that the phenotypes of both ACL cells were changed by cultured conditions, especially in the interface cells. After mechanical stretch, the COL1A1 expression of midsubstance and interface cells were stimulated up to 6 and 14-fold levels of each non-stretched control, respectively. The COL3A1 expressions were also enhanced up to 1.8-fold level of controls by stretching treatment in both cells. Integrin alphaVbeta3 was shifted to the peripheral edge of cells by stretching treatment. In addition, mechanical stretch changed the integrin alphaVbeta3-dependent stress fiber formation in both ACL cells. The functional blocking of integrin alphaVbeta3 inhibited stretch-activated COL1A1 and COL3A1 expressions. However, the functional blocking of integrin alpha5 did not suppress the stretch-induced COL1A1 and COL3A1 expressions in both ACL cells. Cultured interface cells loose their phenotypes in collagen gene expressions. However, mechanical stretch reproduces the expression of COL1A1 and COL3A1 genes in cultured ACL cells. The present study demonstrated that stretch-activated collagen gene expressions depend on the integrin alphaVbeta3-mediated cellular adhesions

We developed an animal model of stretch injury to nerve in order to study in vivo conduction changes as a function of nerve strain. In 24 rabbits, the tibial nerve was exposed and stretched by 0%, 6% or 12% of its length. The strain was maintained for one hour. Nerve conduction was monitored during the period of stretch and for a one-hour recovery period. At 6% strain, the amplitude of the action potential had decreased by 70% at one hour and returned to normal during the recovery period. At 12% strain, conduction was completely blocked by one hour, and showed minimal recovery. These findings have clinical implications in nerve repair, limb trauma, and limb lengthening

The straight leg raising test and the femoral nerve stretch test exert traction on the sciatic and femoral nerve, and the lumbosacral plexus and roots. In 40 patients with a suspected L4/5 disc protrusion, ipsilateral sciatica was induced by the femoral nerve stretch test. We believe that this is a pathognomonic sign of a lateral protrusion at L4/5 level

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

Aims. It has been established that mechanical stimulation benefits tendon-bone (T-B) healing, and macrophage phenotype can be regulated by mechanical cues; moreover, the interaction between macrophages and mesenchymal stem cells (MSCs) plays a fundamental role in tissue repair. This study aimed to investigate the role of macrophage-mediated MSC chondrogenesis in load-induced T-B healing in depth. Methods. C57BL/6 mice rotator cuff (RC) repair model was established to explore the effects of mechanical stimulation on macrophage polarization, transforming growth factor (TGF)-β1 generation, and MSC chondrogenesis within T-B enthesis by immunofluorescence and enzyme-linked immunosorbent assay (ELISA). Macrophage depletion was performed by clodronate liposomes, and T-B healing quality was evaluated by histology and biomechanics. In vitro, bone marrow-derived macrophages (BMDMs) were stretched with CELLOAD-300 load system and macrophage polarization was identified by flow cytometry and quantitative real-time polymerase chain reaction (qRT-PCR). MSC chondrogenic differentiation was measured by histochemical analysis and qRT-PCR. ELISA and qRT-PCR were performed to screen the candidate molecules that mediated the pro-chondrogenic function of mechanical stimulated BMDMs. Results. Mechanical stimulation promoted macrophage M2 polarization in vivo and in vitro. The conditioned media from mechanically stimulated BMDMs (MS-CM) enhanced MSC chondrogenic differentiation, and mechanically stimulated BMDMs generated more TGF-β1. Further, neutralizing TGF-β1 in MS-CM can attenuate its pro-chondrogenic effect. In vivo, mechanical stimulation promoted TGF-β1 generation, MSC chondrogenesis, and T-B healing, which were abolished following macrophage depletion. Conclusion. Macrophages subjected to appropriate mechanical stimulation could polarize toward the M2 phenotype and secrete TGF-β1 to promote MSC chondrogenesis, which subsequently augments T-B healing. Cite this article: Bone Joint Res 2023;12(3):219–230

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

Introduction. Sheffield Children's Hospital specialises in limb lengthening for children. Soft tissue contracture and loss of range of motion at the knee and ankle are common complications. This review aims to look at therapeutic techniques used by the therapy team to manage these issues. Materials & Methods. A retrospective case review of therapy notes was performed of femoral and tibial lengthening's over the last 3 years. Included were children having long bone lengthening with an iIntramedullary nail, circular frame or mono-lateral rail. Patients excluded were any external fixators crossing the knee/ankle joints. Results. 20 tibial and 25 femoral lengthening's met the inclusion criteria. Pathologies included, complex fractures, limb deficiency, post septic necrosis and other congenital conditions leading to growth disturbance. All patients had issues with loss of motion at some point during the lengthening process. The knee and foot/ankle were equally affected. Numerous risk factors were identified across the cohort. Treatment provided included splinting, serial casting, bolt on shoes, exercise therapy, electrical muscle stimulation and passive stretching. Conclusions. Loss of motion in lower limb joints was common. Patients at higher risk were those with abnormal anatomy, larger target lengthening's, poor compliance or lack of access to local services. Therapy played a significant role in managing joint motion during treatment. However, limitations were noted. No one treatment option gave preferential outcomes, selection of treatment needed to be patient specific. Future research should look at guidelines to aid timely input and avoid secondary complications

Purpose and Background. Clinical practice guidelines (CPGs) recommend self-management for low back pain (LBP). Our recent narrative review on self-management needs revealed a consensus with respect to the critical components of self-management interventions. With mobile health advancements, apps offer innovative support for LBP management. This study aims to identify current apps for the self-management of LBP, assessing them for their quality, intervention content, theoretical approaches, and risk management approaches. Methods and Results. We identified 69 apps for LBP self-management from a systematic search in the UK iTunes and Google Play stores. The most recommended interventions are muscle stretching (n=51, 73.9%), muscle strengthening (n=42, 60.9%), and core stability exercises (n=32, 46.4%). The average MARS (SD) overall score for the included apps was 2.4 (0.44) out of a possible 5 points, with the engagement and information dimension scoring the lowest at 2.1. In terms of theoretical and risk management approaches, no apps offered a theoretical care model and all failed to specify the age group targeted; only one (1.4%) provided a tailored care approach; 18 (26.1%) included intervention progression; and 11 (15.9%) reported management safety checks. Conclusion. This study shows that app developers generally select interventions endorsed by CPGs. However, the application of a biopsychosocial care model is not being considered. Most of them are of low quality, lacking theoretical approaches to care and consideration of associated risks. It is essential to involve clinicians and patients in developing LBP self-management apps to improve the quality and related approach. Conflicts of interest. None. Sources of funding. No funding obtained. This study has been published in JMIR mHealth and uHealth

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

Aims. Distraction osteogenesis (DO) is a useful orthopaedic procedure employed to lengthen and reshape bones by stimulating bone formation through controlled slow stretching force. Despite its promising applications, difficulties are still encountered. Our previous study demonstrated that pulsed electromagnetic field (PEMF) treatment significantly enhances bone mineralization and neovascularization, suggesting its potential application. The current study compared a new, high slew rate (HSR) PEMF signal, with different treatment durations, with the standard Food and Drug Administration (FDA)-approved signal, to determine if HSR PEMF is a better alternative for bone formation augmentation. Methods. The effects of a HSR PEMF signal with three daily treatment durations (0.5, one, and three hours/day) were investigated in an established rat DO model with comparison of an FDA-approved classic signal (three hrs/day). PEMF treatments were applied to the rats daily for 35 days, starting from the distraction phase until termination. Radiography, micro-CT (μCT), biomechanical tests, and histological examinations were employed to evaluate the quality of bone formation. Results. All rats tolerated the treatment well and no obvious adverse effects were found. By comparison, the HSR signal (three hrs/day) treatment group achieved the best healing outcome, in that endochondral ossification and bone consolidation were enhanced. In addition, HSR signal treatment (one one hr/day) had similar effects to treatment using the classic signal (three three hrs/day), indicating that treatment duration could be significantly shortened with the HSR signal. Conclusion. HSR signal may significantly enhance bone formation and shorten daily treatment duration in DO, making it a potential candidate for a new clinical protocol for patients undergoing DO treatments. Cite this article: Bone Joint Res 2021;10(12):767–779

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

Introduction. Compartment syndrome can be a life changing consequence of injury to a limb. If not diagnosed and treated early it can lead to permanent disability. Neurovascular observations done on the ward by nursing staff, are often our early warning system to those developing compartment syndrome. But are these adequate for detecting the early signs of compartment syndrome? Our aim was to compare the quality and variability of charts across the UK major trauma network. Materials & Methods. All major trauma centres in England and Scotland were invited to supply a copy of the neurovascular chart routinely used. We assessed how such charts record relevant information. Specific primary data points included were pain scores, analgesia requirements, pain on passive stretch and decreased sensation in the first web space specifically. As secondary objectives, we assessed how late signs were recorded, whether clear instructions were included, quantitative scores and the use of regional blocks recorded. Results. A response rate of 46% was achieved. Of the charts reviewed, 25% documented pain scores or pain on passive movement. Pain on movement and analgesia requirements were documented in 33% and 8% respectively. Specific sensation within the 1. st. webspace was recorded in 16%. No charts recorded use of regional block. All charts recorded global sensation, movement (unspecified), pulse and colour whilst 66% documented capillary refill and 83% temperature. Instructions were included in 41% of charts. Conclusions. In 2016, the BOA supported publication of an observation chart for this purpose however, it is not widely used. In our study, late signs of compartment syndrome were generally well recorded. However, documentation of early signs and regional blocks was poor. This may lead to delays in diagnosis with significant clinical and medicolegal consequences. Standardisation of documentation by updating and promoting the use of the pre-existing chart would ensure highest quality care across the network

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