The article shows the effectiveness of the use of polymer additives for the production of fine-grained concrete mixtures and concretes based on using coal fly ash, which can be used as working mixtures for a 3D printer. Using mathematical planning of experiments, a set of experimental–statistical models was obtained that describes the influence of mixture composition factors including copolymer additive on the most important properties of ash-containing concrete mixtures and concretes for 3D concrete printing in the presence of a hardening accelerator additive. It is shown that when the dry mixture is mixed in water, the redispersed polymer powders are converted into an adhesive polymer dispersion, which, when the solution cures, creates “rubber bridges” in its pores and at the border with the base. They have high tensile strength and elastically reinforce the cement stone; in addition, they are also capable of not only significantly increasing the adhesion between the layers of the extruded mixture, but also significantly smoothing out such shortcomings of the cement stone as increased brittleness, low ultimate elongation, and a tendency to cracking. The development of such materials makes it possible to rationally use natural raw materials, fuel, electrical energy, utilize production waste, and reduce greenhouse gas emissions. This approach allows solving a number of important environmental, economic, and social problems [Modern construction is developing at a high speed due to the integration of innovative technologies and modern building materials into its process. The construction industry is one of the most resource- and energy-consuming, since the construction of buildings and structures for industrial and civil purposes requires a significant amount of non-renewable resources, the consumption of which increases with the increasing needs of people . Today, problems ,4.The most famous additive technology is the use of 3D printing in the construction process. The essence of this method is the layer-by-layer application of the mixture. With the use of 3D printers, it is possible to provide high-speed robotic construction of objects, including complex shapes, with a minimization of material consumption and labor use.Nowadays, a large amount of materials for 3D printing is used; the main ones are fine-grained concrete mixtures using Portland cement, mineral aggregates and fillers, various chemical additives, and fiber ,6.Building mixtures for 3D printing must have certain properties, in particular: the necessary workability (extrudability); structural strength after a certain time of layer curing; tensile strength at splitting, characterized by adhesion between the layers; as well as design compressive strength.A series of studies indicate the improvement of the properties of mixtures suitable for 3D concrete printing by adding various polymer additives to the cement matrix ,8. TheirDuring mixing in water, redispersed polymer powders are transformed into an adhesive polymer dispersion, which, when the concrete cures, creates “rubber bridges” in its pores and at the interface with the base . They haYi Zhang et al.  investigNowadays, the technology of cement concrete and mortars using industrial wastes, in particular fly ash, has been developed. Fly ash, having a high specific surface area, in addition to a direct chemical interaction with cement, actively affects the physicochemical processes on the surface of distribution “cement paste—aggregate” where the formation of contacts between them begins. For ash-containing mixtures, the impact of RPP is currently not fully investigated.The aim of this work was to develop ash-containing mixtures using redispersed polymer powder, characterized by the required technological properties, as well as structural strength at a certain time after extrusion of the layer, strength, providing adhesion of concrete layers, and compressive strength at an early and a project age.3S—57.10%; C2S—21.27%; C3A—6.87%; C4AF—12.19% (EN 196-2). The specific surface area of the Portland cement was S = 300–320 m2/kg (EN 196-6).The materials used in the research were Portland cement CEM I 42.5R of Cement Plant Dyckerhoff Ukraine and fly ash from Burshtynska thermal power plant , which belongs to type II ash of category B with a residue on a sieve, with a mesh size of 45 μm no more than 25% (class 2) (EN 450-1:2012). The chemical composition of Portland cement and fly ash are given in 2SO4. The redispersed polymer powders are selected among the most popular ones, in particular: vinyl ester of versatile acid (VEOVA), copolymer—vinyl acetate–ethylene (VAE), and polymer of vinyl acetate (PVA), the characteristics of which are given in Quartz sand with fineness modulus 2.1 was used as an aggregate. Chemical additives were: superplasticizer (SP) of polycarboxylate type and hardening accelerator (HA) sodium sulfate NaThe main task in the study of suitability for 3D printer fine-grained concrete mixtures without coarse aggregate DSTU B V.2.7-43-96 (Ukrainian Standart) is to ensure their required shape when extruded from the printer head with the achievement of the specified structural strength, as well as the strength of adhesion between the layers without the formation of cracks and other defects ,20,21. SThe 3D printed sample was cut into four-layer specimens with cross-sectional dimensions of 40 mm × 50 mm × 50 mm. The surfaces of the samples to which the load was applied were additionally smoothed.The workability of concrete mixtures was determined by immersion of a standard cone; the tensile splitting strength and compressive strength were determined according to EN 196-1 at the age of 1, 7, and 28 days. The testing machine FP-100/1 100 kN  was used for testing. Tests for tensile splitting strength were carried out on three samples. The samples were placed in the machine and loaded with cylindrical steel heads at the boundaries of the layers. The load was transferred to the sample at a constant speed of 50 N/s until destruction. Compressive strength was tested on six samples; the load was transferred to the sample at a speed of 500 N/s until destruction. The head of the testing machine was assembled with a hinge to adapt to any possible non-parallel surface.The setting time (curing time) was determined according to EN 196–3 by the time from the moment of mixing to the beginning of setting, at which it becomes impossible to further mold with a 3D printer.To determine the structural strength, a technique is proposed that allows to measure the ultimate load limit on a sample of an extruded concrete layer, at which it begins to deform  Figure .At the first stage of the study, the effects of redispersed polymer powders of different natures were compared. In the mixtures containing cement and quartz sand, a polycarboxylate superplasticizer and a hardening accelerator were added during mixing. The proportion of polymer was 0%, 1.0%, and 2.0% by weight of the dry mix; the W/C ratio was constant at each point (W/C = 0.6). The compositions of the studied mixtures are given in The obtained experimental results are shown in Analyzing the results obtained, it can be concluded that the addition of RPP causes an increase in the workability of the mixture on the immersion of the cone from 8 cm to 10–11.5 cm at a constant water content and polymer content of 1% by weight of the mixture. With a further increase in the amount of RPP to 2%, there is a slight increase in workability to 12–13.5 cm a. The efThe effect of RPP on the structural strength 30 min after mixing the mixture is ambiguous. Vinyl ester of versatic acid significantly reduces structural strength. The effect of polyvinyl acetate is similar; however, the reduction of strength is less significant. At the same time, a positive effect is observed at a medium content (1%) of the vinyl acetate–ethylene copolymer; however, with a further increase in the content of RPP, the structural strength also decreases compared to the sample without polymer powder .Polymer powders have mixed effects on both compressive and splitting strengths at different curing times. According to the results obtained , the addThe tensile splitting strength a at the The effect of RPP on compressive strength b is someThus, it can be concluded that the best results of structural strength and tensile splitting strength, which characterizes the adhesion between the layers, were obtained using a copolymer–vinyl acetate–ethylene; thus, further studies were carried out using this RPP.2 [n rows and m columns, which gives a set of combinations of factors varied relative to some origin or zero (basic) level. The permissible range of the variation of factors (factor space) is selected on the basis of a preliminary study of the object in accordance with the purpose. To simplify the recording of experimental conditions and processing of experimental data, the upper level of factors is coded +1, the lower level −1, and the main level corresponds to 0.In the second stage, algorithmic experiments were performed to study the combined effect of fly ash and vinyl acetate–ethylene copolymer on the properties of concrete suitable for 3D printer according to the three-level two-factor plan B2 . The useib was estimated by finding the experimental value of the t—criterion (it) and comparing it with the table [For the construction of quadratic models, a full factorial experiment was used, which provides for all the possible combinations of factors at three levels. For the technological analysis and selection of significant factors, along with checking the adequacy of the equation, the significance of the regression coefficients was also assessed. The significance of the regression coefficients he table . Regressk factors. The conditions for planning the experiments are given in The results of the experiments were processed using methods of mathematical statistics, obtaining quadratic regression equations in general form for The parameters studied were: the setting time; structural strength 30 min after mixing; compressive strength; and tensile splitting strength at the age of 1, 7, and 28 days.The planning matrix and composition of the mixtures, as well as experimental results are given in During the research, at each point of the plan to evaluate the influence of factors on the properties of concrete, mixtures were prepared according to The water consumption was varied to ensure the necessary workability by immersion of a standard cone of 8–10 cm, which ensured sufficient formability (extrusion) of the mixture. Formability was determined by the ability of the mixture to be squeezed out of the printer’s mouthpiece without cracks and delaminating along the length of the bar.The suitability of the mixtures for molding was determined by the time from the moment of mixing to the beginning of hardening after which further molding on a 3D printer becomes impossible.After statistical processing of the results of the experiments , performY is the calculated value of the studied parameter; iX…jX are independent variables (factors) that can be varied during experiments; 0β, iβ…jβ, iiβ…ijβ are statistical estimates of regression coefficients.General type of equations:The analysis of the coefficients  of the rTo analyze the obtained experimental and statistical models, two-factor graphical dependencies were built, which show the influence of composition factors on the properties of concrete suitable for the 3D printer .The addition of RPP to the mixtures for the 3D printer allows to increase the setting time a or the The obtained results clearly show the negative effect on the tensile splitting strength a and comThe influence of the studied factors on the strength parameters is to some extent linear, as evidenced by the insignificant quadratic coefficients of the regression equations . This is2 emissions and improves the environmental situation. RPP, in turn, increases the plasticity (extrudability) of the mixture, as well as the adhesive strength of the adhesion of the layers, which is important for mixtures used in 3D printers.The purpose of fly ash in construction mixtures and RPP is different; however, their combination gives a positive effect. Fly ash is an active mineral additive that helps to increase the volume of hydrate formations; moreover, the addition of fly ash to cements and concrete leads to a reduction in clinker consumption, which reduces COComparing the analysis of the influence of the studied redispersible polymer powders allows to consider that the best values of the complex of basic properties of mixtures and concretes for a 3D printer are achieved when using copolymer–vinyl acetate–ethylene.Addition of redispersible polymer powder to the fly ash containing concrete mixture increases the tensile splitting strength, which improves the adhesion strength between the layers of the printed mixture.As follows from the nature of the interaction between redispersible polymer powder and cement–ash binder, the increased content of polymer additive has a more positive effect on the tensile splitting strength at a lower cement–ash binder consumption strength increase by 35–40% at 20% CAB consumption and 8–12% at 15% CAB.The use of a redispersible polymer powder with a cement–ash binder content of 180–200 kg/t, along with increased adhesive strength, makes it possible to provide the necessary compressive strength of ash-containing concrete, suitable for printing on a 3D printer.In further research, it is advisable to develop compositions of building mixtures for a 3D printer using other dispersed products of technogenic origin; in addition, to offer technological solutions that take into account the design features of existing 3D printers.


Determination of spine posture is of great interest for the effective prevention, evaluation, treatment and evolution monitoring of spinal disorders. Limitations of traditional imaging systems, including cost, radiation exposure (for X-ray based systems), projection volume issues and subject positioning requirements, etc., make non-invasive motion assessment tools effective alternatives for clinical and non-clinical use. In this work, a procedure was developed to obtain a subject-specific multibody model of the spine using either inertial or optical sensors and, based on this multibody model, to estimate the locations and orientations of the 17 vertebrae constituting the thoracolumbar spine. The number and calibration of the sensors, angular offsets, scaling difficulties and gender differences were addressed to achieve an accurate 3D-representation of the spine. The approach was validated by comparing the estimated positions of the sensors on 14 healthy subjects with those provided by an optical motion capture system. A mean position error of lower than 12 mm was obtained, thus showing that the proposed method can offer an effective non-invasive tool for the assessment of spine posture. The spine is defined by a strong, stable and flexible structure composed of vertebrae,  and its ® imaging system offers the possibility of obtaining 3D information from two X-ray images, by placing two pairs of tubes and detectors orthogonal to each other [The plain radiography image remains an essential tool for the diagnosis of spinal abnormalities and deformities, and it is still used as the gold standard . It invoch other . An axiach other , the usech other ,9.In addition to the invasive approach offered in , there iSince spinal curvature is soft (it can be approximated by a cubic spline ), and thThe remainder of the paper is organized as follows: To facilitate understanding of the proposed method that is described in this section, a flowchart is presented below .Fourteen volunteer subjects  were recruited for this study, all of whom had no history of spinal surgery, tumors or disorders of the trunk. All subjects gave written informed consent for their participation. Six IMUs  sampling at 100 Hz, were attached to the subject’s body with double-sided adhesive tape at vertebrae Thoracic 1 (T1), Thoracic 4 (T4), Thoracic 7 (T7), Thoracic 10 (T10), Lumbar 1 (L1) and Lumbar 5 (L5) d, as canx-axis in the posterior–anterior direction, y-axis in the medial–lateral direction, and z-axis in the vertical direction. Once calibrated, the global reference frames of the sensors shared the same vertical z-axis, but their x-axes were given by the direction of magnetic North. Therefore, to compare the data obtained by both motion capture systems, the initial z-axis rotations of the base body (L5), as measured by both the optical system and the inertial sensors, were canceled in the orientations of both the markers and the IMUs.As explained in , the optx-axis  of the vertebra frame of reference  and theBecause the anteversion of the pelvis induces a higher inclination of the attached lumbar L5 in the sagittal plane, an additional rotation of 10° for men or 14° for women was added. The differences between the sexes for the angle used in this work corresponds to the differences in the acetabular version reported in the literature ,30,31.From this predicted spinal curvature, the angular offsets were defined as the angles between the orientation measured by the sensor  and the calculated distance along the estimated one b, and thFrom here on, the proposed method used to build a personalized multibody model of the subject’s spine based on the orientations of several inertial sensors placed on various identified vertebrae, and to estimate the spinal posture from this personalized multibody model, is called TPM. Moreover, where the orientations of the inertial sensors were provided by the inertial sensors themselves, the method is called TPM-IMU, and where the orientations of the inertial sensors were obtained using the cluster of three markers attached to each sensor and the optical motion capture system, the method is called TPM-OPT.To validate the proposed method and the correct location of the bodies, the estimated positions of the sensors  was set at the position of the first IMU at L5, and the distances between the measured and the estimated positions of sensors #2 to #6 , the last body of the open kinematic chain, was 8.3 mm for 6 sensors with TPM-OPT, and, with fewer sensors, e6 was found to be lower than 10.3 mm when using the optimal configuration. As the mean measured distance along the skin of the back for all subjects was 43 cm, the error at T1 was lower than 2%.The fourteen 3D models obtained using TPM-OPT and six sensors are represented in The fourteen 3D models obtained using TPM-IMU and six sensors are represented in This work proposed an approach to determine the 3D human spine posture through a multibody model using the orientations of a set of sensors attached to the back of the subject, obtained either by the readings of inertial sensors (TPM-IMU) or by an optical motion capture system where the sensors were simply clusters of markers (TPM-OPT). The calculation of the differences between the direct optical measurement of the positions of the sensors (from the three markers attached to each of them) and the estimated position of the sensors, using either TPM-OPT or TPM-IMU for positions #2 to #6, served to validate the approach. The errors obtained with TPM-OPT showed a mean value lower than 12 mm using either six or five sensors. The mean errors obtained with TPM-IMU were 12 mm using six sensors and 12.5 mm using five sensors. Differences between the two procedures were almost undetectable by visual inspection . For botThe mean error e6 at the top of the thoracolumbar spine (T1) was lower than 9 mm using 6 sensors (TPM-OPT and TPM-IMU), which corresponds to 2% of the subjects’ mean skin surface length. At first glance, it could be surprising that errors e2 (L1) and e3 (T10) were higher than e6 (T1). The reason is that, while these points are closer to the origin of the model (L5), the lumbar region is affected by a thicker region of soft tissue due to the presence of both muscle and adipose tissue around the upper gluteal muscles , and theThe complex mathematical model proposed in  to reproOwing to the additional rotation imposed at L5, the curves defined by the estimated skin surface matched well with the curves defined by the optical markers for both sexes. Correct location and orientation of the spine bodies are of great interest, because spine curvature influences vertebral loading and risk factor patterns for neutral standing and other activities , which mFuture work includes: (i) to validate the proposed method against X-ray imaging, the gold standard; (ii) to test a broader group of people, considering subjects with lateral deformities, such as scoliosis, and subjects of different ages, body fat percentages, etc., since the relationship between the external and internal curves requires corrections which depend on the subject’s personal characteristics; and (iii) to study the accuracy provided by the proposed method when measuring the spine configuration along the motion, as the skin artifact can affect the location of sensors with respect to their associated vertebrae .The conclusion is twofold. First, it has been shown that wearable inertial sensors offer a non-invasive tool for the assessment of spine posture which can be valuable for clinical use. Second, a procedure has been proposed to obtain a subject-specific spine multibody model for computational simulations using any type of 3D orientation sensors. In this work, both inertial and optical sensors have been tested.


We regret that the original version of our paper unfortunately contained some inappropriate representative images. The immunostaining images of VASP in the LV-VASP and VASP-shRNA groups in Figure 2D, and the representative images of transwell in Figures 2B, 2C, and 4B were mis-pasted when choosing representative images from the large image data. The correct versions of Figures 2 and 4 appear below. The authors confirm that these corrections made in this erratum do not affect the original conclusions. All the authors of the paper have agreed to this correction. The authors apologize for any inconvenience that the errors may have caused.


In the present study, pins made from the novel Mg-2Zn-2Ga alloy were installed within the femoral bones of six Wistar rats. The level of bioresorption was assessed after 1, 3, and 6 months by radiography, histology, SEM, and EDX. Significant bioresorption was evident after 3 months, and complete dissolution of the pins occurred at 6 months after the installation. No pronounced gas cavities could be found at the pin installation sites throughout the postoperative period. The animals’ blood parameters showed no signs of inflammation or toxication. These findings are sufficiently encouraging to motivate further research to broaden the experimental coverage to increase the number of observed animals and to conduct tests involving other, larger animals. The history of employing metallic structures for bone repair has witnessed more than 150 years of selection and application of various metal alloys for the fabrication and optimization of bone fixators ,3. The fTo date, there are three main groups of biodegradable materials that can be used for osteosynthesis: polymers, ceramics and their composites, and the bioresorbable alloys of various metals . MagnesiMagnesium is a vital chemical macronutrient (comprising 0.2% of a human’s body weight) deposited in the bone tissue that is considered to be non-toxic and has good biocompatibility, biodegradability, and absorbability, as well as high tensile strength, compared with polymers, and it is less stiff than ceramics. The elastic modulus of magnesium (45 GPa) is closer to the elastic modulus of cortical bone (15–25 GPa) in comparison with the elastic moduli of titanium alloys and stainless steel (115–200 GPa) ,17.When biodegradable implants are installed, their degradation rate must not exceed the tissue growth rate to ensure proper filling of the voids formed within the implant by the new bone tissue. The addition of alloying elements into Mg alloys or the use of barrier coatings to reinforce bone growth can improve the bone healing process . For exaThe studied Mg-2Zn-2Ga (wt.%) alloy has previously shown a low in vitro corrosion rate and low cytotoxicity , and it However, despite the significant advantages, a number of unresolved issues persist that relate to the prospective use of bioresorbable magnesium alloys. Pure magnesium and some of its alloys corrode too rapidly under physiological conditions, leading to the early loosening or disintegration of implants before new bone has formed. Rapid corrosion causes excessive hydrogen release at the implant site, which can have a negative effect on the surrounding tissue and prevent bone regeneration ,39,40. TIn summary, despite the great potential of magnesium and its alloys as materials for biodegradable implants, the main obstacle to their wider use consists of their rapid and uncontrolled degradation in the physiological environment, which is accompanied by the release of hydrogen . In someThe purpose of the present study was to assess the effectiveness of a new Mg alloy bioresorbable implantation system via an experimental study of laboratory animals to assess the biocompatibility, rate of resorption, and influence of the Mg alloy’s degradation products on the animal′s health.6. The resulting melt was purged with Ar before being poured into a preheated aluminum mold. The ingot was solution heat-treated at 300 °C for 15 h and then at 400 °C for 30 h and machined. Then, the billet was subjected to hot extrusion from 50 to 20 mm (at an extrusion ratio of 6). The pins with a diameter of 1.5 mm and a height of 5 mm were cut from the extruded rod and ground with emery bars. The full description of the alloy sample preparation can be found elsewhere [The Mg-2 wt.% Zn-2 wt.% Ga alloy samples were prepared using high-purity metals. Melting was carried out in a resistance furnace in a steel crucible coated with BN in a protective atmosphere of Ar plus 2 vol.% SFlsewhere .In the training vivarium of the Kuban State Medical University  in July 2021, an experimental study was conducted on laboratory animals (rats), which consisted of the installation of magnesium alloy implants (Mn-2 wt.% Zn-2 wt.% Ga) in the animal’s femoral bone, with further observation in the early post-operative period, X-ray examination, and histological examination. The experiment used randomly selected white laboratory rats of the Wistar line, of both sexes, aged from 6 months, with an average body weight of 340–400 g, as shown in The study protocol was approved by the interuniversity ethics committee (number 04 of 15 April 2021), and it complied with the principles of the “European Convention for the Protection of Vertebrate Animals Used for Experiments or for Other Scientific Purposes” dated 18 March 1986. The operation was performed under general anesthesia with an intramuscular injection of Flexoprofen  2.5% 10 mg per kg and Zoletil 100  20 mg per kg. Brilocaine  1:200,000 was used for the local anesthesia. Under the conditions of the experimental operating room and in compliance with the rules of asepsis and antisepsis, a skin incision was made in the area of the femur from the outside and the bone was isolated. Each animal underwent the installation of 3 implants in the body of the femur, each with a diameter of 1.7 mm and a length of 5 mm. The implants are shown in The wound was sutured with Vicryl 4-0 . The postoperative area was treated with the antibacterial aerosol Terramycin . Postoperative antibiotic therapy was performed using intramuscular injections of Convenia . The duration of the experiment was 6 months. A total of 6 animals were involved in the experiment. Each day, the animals were examined for their general condition and the condition of the postoperative area. Withdrawal from the experiment was carried out 1 month, 3 months, and 6 months after the operation. At the end of each study period, the animals were withdrawn from the experiment by an intramuscular injection and overdose of Telazol . Then, the femur was harvested for further X-ray and histological examination. The samples selected for histological examination were placed in a 10% neutral formalin. Before withdrawal from the experiment, blood and urine samples were taken to determine the concentration of magnesium ions in the blood serum, as well as the markers of inflammation. One animal was withdrawn from the experiment 1 month after a consolidated pathological fracture of the femur, with the fragments freely lying in the soft tissues being visualized. The installed pins were integrated into the bone tissue. Perhaps, during the osteotomy to form the implant bed, the strength of the femur had decreased due to its small size a,b.Before removing an animal from the experiment, an ultrasound examination was performed in the area of the femur. An ultrasound study was performed on days 7 and 14 and at 1 month, 3 months, and 6 months after implantation using a Philips Affiniti 70 device  with a surface sensor (L 12-3).2).At the Department of Radiation Diagnostics, MGMSU, named after A.I. Evdokimov, targeted radiography and cone beam computed tomography (CBCT) of the biopsy specimens were performed. Targeted X-ray examination was carried out using the intraoral X-ray apparatus “FOCUS” Kavo . After the animals were withdrawn from the experiment, the cone beam computed tomography of the femur was performed using the X-ray computed tomograph ORTHOPANTOMOGRAPH OP 3D Pro, KaVo  in the “endodontics” mode, i.e., at the maximum resolution  was performed. The micro-CT was carried out on the basis of the Saint-Petersburg Electrotechnical University ETU LETI . The voxel size was 50 µm. The resulting images were processed using CTVox software .The elemental analysis was performed according to the same protocol that was used in our previous study . FirstlyIn the laboratory of the Clinical Medical Center MSMSU, we conducted the histological analysis of the bone samples from each animal. The bone fragments were fixed in a buffered solution of 10% formalin  for at least 24 h. No pathological changes were visualized macroscopically. Decalcification was performed in all cases. The procedure was performed in a standard Biodek-R solution  for 1–3 days at room temperature. After neutralization of the decalcified residues with ammonia water, the specimens were forwarded for staged dehydration according to the following standard protocol: 95% ethanol, xylene, and paraffin. Paraffin sections of 3–4 μm thick were made and processed according to standard procedures and stained with hematoxylin and eosin. In addition to studying sections in a light microscope, all micropreparations were scanned using a Leica Aperio 1000 instrument .The animals were monitored daily in the early post-operative period to study their general condition. In the first days after the operation, slight edema and hyperemia were visualized in the postoperative area a,b.All clinical signs resolved within 2 weeks after surgery. Other clinical signs of local inflammatory reactions did not appear during the primary period after implantation. In addition, there were no significant gas cavities that could be detected by observation and palpation. According to the results of blood and urine tests, no deviations from the norm were revealed.The laboratory analyses of the rats 1 month after the installation of the bioresorbable pins showed no significant deviations from the reference values. We assume that those deviations of the indicators that were determined were associated with stress factors when taking blood and urine from the animals. It should be noted that according to the presented analyses, no inflammatory, allergic, or toxic components were determined.2 during the magnesium biodegradation. A gaseous layer was visualized in the soft tissues over the area of the installed implants after 3 and 6 months , the non-degraded implants were visualized a. AccordAccording to the CBCT data, implants with partial signs of bioresorption in the fragments of the femur were visualized after 1 month a,b.After 3 and 6 months, the implants were not visualized. The formed phenomena were well-visualized both 3 a,b and 6All implants examined appeared to be in contact with the surrounding bone without any evidence of foreign body reaction or fibrointegration. In addition, there were no osteolytic changes and no signs of bone irritation adjacent to the experimental implants.Micro-CT visualized increased density on the non-resorbed implant after 1 month a,b in coIn order to provide significant comparisons between each case, bones were extracted from similar locations in the rats’ bodies. 2 flat areas are summarized in 10(PO4)6(OH)2) is 1.67. In our study, we achieved a Ca/P of 0.4 at 1 month post-implantation and a Ca/P of >1.5 if the post-implantation time was more than 3 months. Thus, we can indirectly assume that the bioresorption process had completed and the HAp with the indicated composition had instead formed.A comprehensive article on the bone–remodeling interaction with Mg-based implants by SEM and EDX was successfully performed in our previous study . The devAfter 1 month, the “bed” of the implant was clearly visible. In one of the areas, a bone sequester was determined, and it was filled with a dense leukocyte infiltrate with the remains of a homogeneous eosinophilic substance, and perifocal bone resorption was determined with severe fibrosis in the inter-beam space. In other areas, the bone tissue in the area of the bed had not changed a–c.After 3 months, the “bed” of the implant could be traced throughout and filled with an internal “bone callus” consisting of an outer layer of fibrous tissue with an abundance of osteogenic cells and pronounced angiomatosis of the middle layer of the cartilage tissue (black arrow) and the inner layer of the emerging bone trabeculae (red arrow). In the bone tissue in the area of the bed with foci of incomplete osteogenesis in the form of osteoid formation, we found the presence of proliferating osteoblasts and increased cellularity in the inter-beam space. There was no inflammatory infiltration a–c.After 6 months, the “bed” of the implant was filled with fibrous tissue, with an abundance of capillaries and a ring-shaped area of compact mature bone. There was no inflammatory infiltration a,b.Plates, screws, nails, and meshes made of steel or titanium alloys are the gold standard for fracture treatment . AccordiThe composition of the subjects′ blood was analyzed to assess the level of released Mg ions and the markers of inflammation. We did not find a significant increase in serum magnesium levels compared with normal values. Magnesium is regulated in the kidneys, which reabsorb Mg and excrete the excess Mg in the urine . UrinalyThe biodegradation of the implants in vivo was assessed using micro-CT. All implants studied were in direct contact with the surrounding bone and did not show any signs of any adverse reactions. The micro-CT results showed a slight decrease in implant density compared with a non-corroded implant 1 month after implantation. Micro-CT did not reveal the shape of the implant 3 months after implantation. In particular, this study showed that nearly 50% of the implant had degraded after 3 months, and complete bioresorption occurred after 6 months, which was also confirmed by the SEM and EDX analyses. The bone formation around the implants was a very good sign of osseointegration. We can conclude that the post-implantation histological bone formation assessed by micro-CT demonstrated osseointegration and, hence, good biocompatibility with the surrounding bone tissue.5(PO4)3(OH), and calcium phosphate Ca3(PO4)2.The study of the implant–bone interface using SEM-EDX allowed us to study the interface on a microscopic scale and in terms of chemical composition. Regardless of the implantation period, a thin and compact phosphate-based oxide layer (3–5 µm) was found on the surface of the Mg-based implants. Calcium and magnesium were found in this layer, suggesting the formation of a complex or a mixture of Ca/Mg phosphates and hydroxyapatite under in vivo conditions. Similar results were described in our study, where the implant was in close contact with both the cancellous bone and the cortical layer. In the dynamics of our experiment, and especially after six months, the formation of young bone tissue in the osteotomy zone was visualized, which indicates the complete biodegradation of the installed pins. EDX analysis showed primarily C, Ca, P, and O at 3 and 6 months. We can assume that, 6 months after implantation, the remaining implant consisted primarily of substances similar to the formation of hydroxyapatite. We hypothesize that the carbon content was indicative of the standard mineral constituents of bone, hydroxyapatite CaThe interaction of the implant with the tissue was studied histologically, and no gas bubbles were observed. This negligible generation of hydrogen gas is a significant advantage over other Mg-based alloys. Hydrogen production is often accompanied by inflammatory reactions and the formation of cavities encapsulated by fibrous tissue . New bonThis study showed that the installation of an implant made of a magnesium alloy (Mg-2Zn-2Ga) did not lead to significant changes in blood parameters and did not lead to the formation of significant gas cavities, and, based on the studies carried out, it can be concluded that there was good biocompatibility and the osteoconductivity of the Mg-2Zn-2Ga was without acute, subacute, or chronic toxic effects. It should be noted that among the radiation methods used for examination, the most informative for assessing the level of resorption was the use of microfocus computed tomography. The next stage planned is to conduct an experimental study on larger animals.This research will allow various branches of medicine to create the most effective type of fixing structures made of bioresorbable materials consisting of bioneutral and low-toxic elements, which will make it possible to avoid repeated surgical interventions in the future.


Given that the heat treatment states of the base metal have a great influence on the surfacing repair layer, this paper carried out a feasibility study for the remanufacturing of the failed cutter rings of TBM disc cutters with uniform wear  using the gas metal arc welding technology (GMAW). Firstly, this paper developed a heat treatment process route for H13 steel cutter rings. Secondly, the heat treatment process is numerically analyzed based on the developed route, and the rationality of the route is verified from the distribution characteristics of temperature, phase, and stress fields. Subsequently, heat treatment tests were carried out, and the physical and mechanical properties of the base metal samples prepared under laboratory conditions were evaluated respectively and systematically. Based on the comprehensive performance evaluation value calculated by the weighted comparative analysis method, it was clear that the comprehensive performance of the quenched base metal samples was 7.6% higher than that of the engineering cutter ring interior. Therefore, it is reasonable to replace the failed engineering cutter rings repaired under laboratory conditions with the prepared samples as economical alternatives. Finally, the remanufacturing of the base metal samples using GMAW was carried out, and then the remanufacturing performance of the base metal samples was analyzed. The study concluded that the comprehensive performance of the surfacing repair layer was slightly lower than that of the engineering cutter ring edge (4.1%), thus proving that the idea of surfacing remanufacturing of the normally-worn ring proposed in this paper was basically feasible. As modern construction equipment, the full-face tunnel boring machine (TBM) integrates mechanical, hydraulic, electronic, control, and laser technologies . CompareUnder laboratory conditions, before economically and reasonably assessing the feasibility of remanufacturing failed cutter rings, the first task is to prepare the base metal samples that are close to the engineering reality. To ensure that the comprehensive performance of cutter rings satisfies the requirements of the geological conditions of the tunnelling stratum, the microstructures of the cutter rings can be properly regulated in engineering by planning the heat treatment process route. For example, since the cutters are normally subjected to heavy loads and impacts when tunneling in hard rock stratum, the heat treatment processes of quenching and tempering are usually used to prepare the cutter rings with high external hardness and optimal internal toughness. With the further increase of rock hardness, it is necessary to optimize the heat treatment process route and its parameters to improve the physical and mechanical properties of cutter rings  . In addiBefore reasonably assessing the feasibility of remanufacturing failed cutter rings, another key task is to put forward a comprehensive performance assessment method that matches the engineering reality for cutter rings. There are few comprehensive performance evaluation methods for cutter rings due to the fact that: (1) In general, the physical and mechanical properties of cutter rings used in different TBM tunneling projects vary greatly to cope with the different geological conditions; and (2) there are many performance evaluation indices for TBM cutters, such as indent depth, hardness, shear strength, and impact toughness; some of them are incompatible with each other while the others are compatible.Considering that H13 steel is widely used in the manufacture of cutter rings , this pasM and sB, are 352.3 °C and 508.2 °C, respectively. Since the tempering temperature should be higher than sB, it was set to 540 °C.Currently, the industry-accepted heat treatment process for cutter rings consists of no less than twice of preheating and tempering and once quenching . Compreht—the heating time during the quenching process (min), a—the heating coefficient after the second preheating process (0.4 min/mm), b—the heating coefficient during the first preheating process (2 min/mm), c—the heating coefficient during the second preheating process (1 min/mm), K—the correction coefficient (1), and D—the effective thickness of workpieces (76 mm).T—the heating time during the tempering process (min), A—the heating coefficient (2 min/mm), D—the effective thickness of workpieces (76 mm), and B—the additional time (10 min).The heating time is determined by the following two empirical formulas : (1)t=, a FE model was established to simulate the proposed heat treatment process and analyze the rationality of each parameter set for the heat treatment process route in terms of three aspects: temperature field, phase transition field, and stress field. The chemical composition of the simulated cutter ring is the same as that of the base metal samples shown in The simulated temperature change curves at the interior and exterior points of the cutter ring and the temperature difference curve between the interior and exterior points of the cutter ring are shown in This section analyzed the laws of phase transformation with time, starting from austenite, bainite, and martensite, respectively.8823 s (147 min)The temperature and microstructure cloud diagrams at 8823 s (the beginning of the heat preservation stage after the second preheating process) are shown in 2.30,000 s (500 min)The microstructure and temperature cloud diagrams at 30,000 s (the last second of the heat preservation stage during the quenching process) are shown in 3.30,030 s (500 min) and 30,033 s (500.5 min)sB and some austenite had begun to change into bainite. sM and some austenite had begun to change into martensite.The microstructure cloud diagrams at 30,030 s and 30,033 s  are depicted in 4.30,045 s (500.85 min)(1)sM; since sB is greater than sM, the austenite in these zones had not been converted to martensite, resulting in a wider distribution of bainite than martensite in the cutter ring.some zones inside the cutter ring had not been cooled below (2)sB~sM for a short time; additionally, because martensite forms extremely quickly, the maximum amount of martensite (43%) was higher than the maximum amount of bainite (36%).due to the high heat transfer coefficient of the quenching oil see , the coo(3)there was still a large amount of austenite that had not undergone phase transformation at this moment, and the quenching process will continue for some time.(4)bainite and martensite were generated inward from the edge angle of the cutter ring.(5)since there were chamfers at the cutter ring edge, the heat exchange area of the cutter ring edge was smaller than that of the ring root, which resulted in a relatively slow phase transformation speed of the ring edge.The microstructure and temperature cloud diagrams at 30,045 s  are shown in By comparing 5.30,960 s (516 min)The microstructure, temperature, and hardness cloud diagrams at 30,960 s (the last second of the cooling stage during the quenching process) are shown in 6.69,360 s (1156 min)The microstructure, temperature, and hardness cloud diagrams at 69,360 s (the last second of the cooling stage during the second tempering process) are shown in 30,000–30,960 s (approximately 500–516 min)(1)sB; significant transformation of austenite to bainite or martensite cannot be observed, only the effect of temperature change on stress variation needs to be considered. In addition, since the cooling rate of the interior point was faster than that of the exterior point, the surface of the cutter ring was in tension while the inside of the cutter ring was in compression. With the passage of time, the temperature difference between the interior and exterior points increased, and the tensile stress at the exterior point increased rapidly to 152.50 MPa, while the compressive stress at the interior point also rose rapidly to 19.57 MPa.0–59.03 s: during this period, the temperature inside and outside the cutter ring was higher than (2)sM; a gradual increase in the production of martensite and bainite on the surface of the cutter ring could be observed, combined with 59.03–77.42 s: during this period, the temperature inside and outside the cutter ring progressively falls below (3)77.42–83.17 s: With the elapse of time, the temperature inside and outside the cutter ring becomes lower and lower. On the one hand, a large amount of bainite was generated inside the cutter ring during the period, and the higher phase change expansion coefficient made the internal tensile stress decrease gradually; on the other hand, since the phase transformations on the surface of the cutter ring were almost complete, the stress variation of the cutter ring was mainly influenced by the internal phase change. The above two facts indicate that as the temperature dropped, the phase of the cutter ring transformed from the inside to the outside; during this period, the phase transformation in the subsurface layer reduced the compressive stress in the surface layer, causing the stress state of the exterior point to change to tensile stress eventually.(4)83.17–960 s: during this period, the phase transformation of the cutter ring had been basically completed, and the distribution of residual stress in the cutter ring was mainly affected by temperature. When combined with To facilitate the description, the start time of the cooling stage of the quenching process was set to 0 s , and the ending time was set to 960 s . 2.69,360 s (1156 min)This is the last second of the heat treatment process. The experimental tasks were set as follows:Task 1: engineering cutter ring sampling and performance testing to provide basic data for comparative analysis in Tasks 2 and 3.Task 2: firstly, the H13 steel cutter ring samples in the annealed state were treated according to the heat treatment process route developed in Task 3: the base metal samples prepared in Task 2 were remanufactured using GMAW, and then the remanufactured samples were obtained. The remanufactured samples were sampled, and performance tests were conducted. The feasibility of surfacing remanufacturing H13 steel cutter rings in the quenched state was evaluated by comparing the physical and mechanical properties of the base metal samples obtained in Task 2 with those of the engineering cutter rings obtained in Task 1.For Task 1, a certain type of 17-inch engineering cutter ring was selected as the test object, and its chemical composition is shown in For Task 2, According to the cutter ring heat treatment process route developed in For Task 3, as shown in All samples used for performance testing in Task 2 and Task 3 were prepared according to The shapes and dimensions of the samples prepared in Task 1 were the same as those of the samples in Tasks 2 and 3.Wear resistanceh and hardness H [h was as follows: using CFT-I friction tester, dry friction test was firstly carried out in which a standard steel ball with a diameter of 4 mm repeatedly rubbed the friction plane of the wear-resistant sample; secondly, the indent depth h of the worn wear-resistant sampling was measured using VHX-2000C super depth-of-field microscope.The wear-resistant performance was characterized by indent depth rdness H . The tes2.Shear strengthτ of the shear sample was tested using WAW-300 universal testing machine. During the test, the shear loading speed was set to 2 mm/min, and the maximum applied shear load was set to 25 kN.The shear strength 3.Impact toughnessa of the impact sample with a V-shaped fracture, as shown in The impact toughness H were relatively simple and will not be presented here.The test schemes for observing microstructure and measuring hardness h was inversely proportional to the hardness H. While the cutter ring, base metal samples, and surfacing repair layer were all made of H13 steel, their chemical compositions were different. The different chemical compositions led to different compatibilities between the friction object and the steel pellets used for friction testing. As the base metal samples and steel pellets were well-compatible, the indent depth on the base metal samples was greater. For materials with the same chemical composition, hardness was inversely proportional to impact toughness [The physical and mechanical properties of the engineering cutter ring samples, the base metal samples, and the surfacing repair layer samples are shown in oughness . The tesIf the radial wear of the cutter ring reaches 35 mm during engineering maintenance, the ring is considered failed . At this1.Single performance evaluationIt can be seen from Compared to the physical and mechanical properties of the engineering cutter ring samples sampled from each region, the base metal samples had both advantages and disadvantages. Therefore, it was not easy to determine which sample had the best performance. Only in terms of the number of advantageous items were the physical and mechanical properties of the base metal samples comparable to those of an engineering cutter ring interior. Compared with the engineering cutter ring interior, the base metal samples had better wear resistance and impact toughness but poorer shear strength.2.Comprehensive performance evaluationSi of the quenched samples relative to the engineering cutter ring samples sampled from each region was proposed based on the weighted comparative analysis method:i = 1, 2 and 3, corresponding to the cutter ring edge, the cutter ring interior, and the cutter ring root, respectively; h (μm), hardness H (HRC), shear strength τ (MPa), and impact toughness a (J/cm2) when the performance indicators of the quenched samples are compared with those of the engineering cutter ring samples sampled from a given region corresponding to i; as shown in x can refer to one of the characters h, H, τ, and a which denotes the test value of the corresponding performance index of the base metal samples; ix represents the test value of the corresponding performance index of the engineering cutter ring samples sampled from the given region corresponding to i.The formula for calculating the comprehensive performance evaluation value d is inversely proportional to the wear resistance of the cutter. The higher the comprehensive performance evaluation value iS, the better the comprehensive performance. Based on formula (3), the comprehensive performance evaluation value iS of the base metal samples obtained in Task 2 was calculated, and then a bar graph was plotted in S2 of the base metal samples was equal to 7.6%, which means that the comprehensive performance of the base metal samples was close to that of the engineering cutter ring interior. Therefore, the base metal samples prepared in Task 2 can be used in Task 3 as an economical alternative to the failed engineering cutter rings.It is worth noting that the negative sign is taken before the The performance of the surfacing repair layer prepared in Task 3 should be as close as possible to that of the engineering cutter ring edge. To thoroughly investigate the remanufacturing performance of the base metal samples, a single performance evaluation and a comprehensive performance evaluation were carried out.1.Single performance evaluationTo save space, the performance test results of the remanufactured samples obtained in Task 3 are also summarized in As can be seen from 2.Microstructure evolutionAs shown in As shown in As shown in 3.Comprehensive performance evaluationiS of the surfacing repair layer relative to the engineering cutter ring edge was calculated. As shown in iS was equal to −4.1%, which indicated that the comprehensive performance of the surfacing repair layer was slightly lower than that of the engineering cutter ring edge. Therefore, it would be feasible to employ GMAW to remanufacture the normally-worn ring, but the comprehensive performance of the surfacing repair layer still had room for improvement.Based on formula (3), the comprehensive performance evaluation value The simulation and experimental study of the heat treatment process of the H13 steel cutter ring were carried out in this paper. On this basis, considering the actual heat treatment state of the normally-worn ring, the feasibility of surfacing remanufacturing the cutter ring was further evaluated.The simulation analyses of the heat treatment process route show that the temperature distribution inside and outside was uniform; the microstructure was dominated by martensite, which ensured the high hardness of the base metal samples ; the temThe analyses of the physical and mechanical properties of the base metal samples show that, compared with the engineering cutter ring interior, the base metal samples had better indent depth, hardness, and impact toughness but poorer shear strength. As the comprehensive performance was similar to the engineering cutter ring interior, the base metal samples can be used to simulate the normally-worn ring.The analyses of the remanufactured properties of the base metal samples show that, compared with the engineering cutter ring edge, the surfacing repair layer had better indent depth but poorer hardness, impact toughness, and shear strength. The comprehensive performance of the surfacing repair layer was slightly lower than that of the cutter ring edge (4.1%), which preliminary verified the possibility of surfacing remanufacturing the normally-worn ring.In the future, the comprehensive performance of the surfacing repair layer would be further improved by optimizing the wire material composition and the surfacing remanufacturing process.


Tendinopathy is a broad term encompassing painful conditions occurring in and around tendons in response to overuse. The supraspinatus muscle is an important passive stabilizer of the shoulder joint, and it is responsible for shoulder extension and advancement of the limb. Although the cause of supraspinatus tendinopathy is unclear, suggested contributing factors include aging, overuse, chronic trauma and hypoxia secondary to hypovascularity of the supraspinatus tendon. Supraspinatus tendinopathy is a poorly described cause of shoulder lameness in dogs. Two forms of supraspinatus tendinopathy have been reported: mineralized and non-mineralized. While the diagnoses and the treatments of the mineralized form have been widely described in the literature, few scientific papers report the diagnoses, the treatments and the outcomes of the non-mineralized form. This retrospective study aimed to describe clinical, diagnostic imaging, surgical procedure, concomitant shoulder lesions and short and long-term follow-up of dogs with surgically treated non-mineralized supraspinatus tendinopathy. Obtained results indicate a good outcome with a low incidence of complication rate of the surgical treatment of the non-mineralized form of the supraspinatus tendinopathy.(1) Background: two forms of supraspinatus tendinopathy (ST) have been reported in dogs: mineralized and non-mineralized. Surgical treatment consists of longitudinal incisions (splitting) in the tendon of insertion of the supraspinatus muscle. The purpose of this retrospective study is to describe the diagnostic workout, the surgical procedure and the short and long term follow up of dogs treated for non-mineralized ST. (2) Methods: medical records (2010–2017) of dogs diagnosed with non-mineralized ST that underwent surgical treatment were reviewed. Data retrieved were: signalment, history, clinical signs, orthopaedic examination findings, diagnostic imaging findings, surgical treatment, histopathologic diagnosis and clinical outcome. (3) Results: A total of 27 dogs met the inclusion criteria. The most consistent clinical findings were intermittent lameness accompanied by pain on palpation of the insertion of the supraspinatus. Magnetic resonance imaging (MRI) of 27 shoulders distended sheaths of the biceps tendon (10/27), compression of the biceps brachii tendon sheaths (5/27) and enlargement of the supraspinatus tendon (3/27) were observed. The most prominent histologic finding was severe myxomatous degeneration in all 27 samples. Resolution of lameness was achieved in 80% of the cases surgically treated without any further lameness episodes in the long-term follow-up. (4) Conclusions: the surgical splitting of the non-mineralized supraspinatus tendon is an effective procedure with no intra-operative complications and a low incidence of minor (18%) and major (4%) complications. Tendinopathy is a broad term encompassing painful conditions occurring in and around the tendons in response to injury, especially overuse. The supraspinatus is an important passive stabilizer of the shoulder joint, and it is responsible for shoulder extension and advancement of the limb ,2. AlthoMedical records (2010–2017) of dogs diagnosed with nonmineralized supraspinatus tendinopathy that underwent surgical treatment were reviewed. All dogs at the time of presentation had mono-lateral forelimb lameness and were operated only on the clinically affected limb. Dogs without diagnostic imaging confirmation of supraspinatus tendinopathy, dogs with concurrent orthopedic disorders of the affected limb, and dogs with supraspinatus tendinopathy that were treated conservatively were excluded from the study.The data retrieved were signalment, history, clinical signs, the findings of the orthopedic examination, the findings of diagnostic imaging, surgical treatment, histopathologic diagnosis and the clinical outcome.The disease history was obtained by interviews with the owner, documenting time of onset, the characteristics of lameness, progression of clinical signs and the response to previous treatments.Complete physical and orthopedic examinations of all limbs were performed, including flexion and extension of the shoulder joint, the biceps tendon test in the German-speaking literature and deep palpation of the supraspinatus and biceps tendons after gait evaluation. Lameness was graded using a scale (0–5) where 0 indicated no lameness, 1 indicated slight lameness only after exercise, 2 indicated slight lameness without exercise, 3 indicated moderate lameness, 4 indicated severe lameness and intermittent non weight-bearing lameness, and 5 indicated non weight-bearing lameness .Pain evoked during the execution of passive movements of the shoulder joint were subjectively graded as 0, no pain; 1, faint; 2, mild; 3, severe. If conscious proprioceptive deficits were noted, a complete neurologic examination was performed, and the case was excluded from the study.Mediolateral and cranioproximal–craniodistal radiographic projections of both shoulders were obtained. During the same anesthetic episode, a synovial fluid sample was collected in cases affected by severe lameness in order to rule out inflammatory pathologies. Magnetic resonance images of both shoulders were acquired with a 0.23 T open unit , using the following sequences: FSE T2 and GFE STIR T2 on the sagittal and transverse planes, GFE T2 STIR on the dorsal plane and SE T1 on the sagittal plane. Images were obtained from the midscapula to midhumeral regions. The sagittal images were oriented parallel to the craniocaudal axis of the scapula and humerus, and the transverse images were oriented perpendicular to the axis of the biceps brachii tendon, proximal to the intertubercular groove. In order to avoid “magic angle” artifact all shoulders were positioned in a surface coil in slight extension, as described by Agnello . MRI cria at 0.15 mg/kg IM. Anesthesia was induced with propofolb at 2 mg/kg IV and maintained with isofluranec, aiming for a 0.8% minimal alveolar concentration after endotracheal intubation. Analgesia was provided by a target-controlled infusion of fentanyld at a plasma concentration of 1.2–1.6 ng/mL. Cefazolin sodiume was administered intravenously (20 mg/kg) 30 min before surgery.Surgery was performed only in the clinically affected shoulder. Dogs were premedicated with methadoneDogs were positioned in lateral recumbency with the affected limb uppermost. An arthroscopic portal was established cranial and distal to the acromium, and an egress needle was positioned cranially into the joint. A short arthroscope  was introduced into the joint through a 2.4 mm sleeve. Joint distention was maintained by an infusion of lactated Ringer’s solution with a lavage pump at 60 mmHg . The medf  were administered for 7 days. No antibiotics drugs were administered in the post-operative period. Dogs were discharged the day after surgery, with instructions to provide strictly restricted physical activity  and passive range-of-motion exercises of both shoulder joints (at least 10 min three times daily) for 3 weeks. During the subsequent 3 weeks, the owners were instructed to gradually increase the duration of the leash walks by 5 min per week. The need of physiotherapy was discussed with the owner and proposed if the clinical outcome was not judged satisfactory.Postoperative pain control was achieved by cold compression for 5 min 3–4 times a day for 48 h, and nonsteroidal anti-inflammatory drugs meloxicamAll dogs were clinically re-evaluated by one of the authors (XXX) 10, 30 and 60 days after surgery. The lameness evaluation score was compared between the entire population and different subgroups affected by only ST or ST with concomitant biceps brachii tendinopathy or ST with concomitant subscapularis tendon partial rupture. Complications were recorded and were either classified as major or minor . Long-te2, respectively. The velocity of each trial was measured by three photoelectric cells mounted 1 m apart on the force plate runway that were connected to a millisecond timer in a start–interrupt fashion. The dogs were walked over the force plates by a trained assistant, and the data were collected independently from the left and right side of the body. A valid trial consisted of a forelimb strike, with the complete foot striking the center of the plate and without another foot being on the plate at the same time, followed by an ipsilateral hind foot strike in the same fashion. A single observer (XX) evaluated each foot strike and determined whether a trial was valid or not by means of camera recordings and morphological evaluation of the curve. The trial was discarded if the paw hit the edge of the force plate, if the contralateral paw hit the force plate or if the dog was distracted during the measurements. The peak vertical force (PVF) from five footfalls for each limb was collected at a walk at all time points. The peak vertical force (PVF) was expressed as a percentage of body weight (%BW). Additionally, a corresponding symmetry index (SI) for the hind limbs was calculated for the abovementioned parameters. The symmetry index was calculated using the following formula [Computer-assisted force platform gait analysis was performed using two force platforms mounted in series  embedded in an 8 m walkway. Two cameras  connected to the acquisition software  were used to record each trial. The dogs were weighed on a calibrated scale immediately before collecting the force plate data. Each dog was allowed to acclimate to the room before data collection began. The dogs were walked across the force platforms until they appeared comfortable. The walking velocity and acceleration parameters were restricted to ranges of 1.1 to 1.3 m/s and ±0.5 m/s formula SI (%) =Twenty-seven dogs with nonmineralized (NM) supraspinatus tendinopathy met the inclusion criteria. The breeds included were Boxer (five), American Staffordshire Bull Terrier (four), Beagle (two), Labrador Retriever (two), Pitbull (two), Border Collies (two), Argentine Dogo (one), Rhodesian Ridgeback (one), Black Russian Terrier (one), Central Asian Shepherd Dog (one), Pyrenean Mastiff (one), German Shepherd (one), Samoyed (one), Tibetan Mastiff (one), Great Swiss Cowherd (one) and mixed breed (one).The patients’ ages ranged from 12 to 90 months (mean: 39.7 months). The patients included 18 males (1 neutered and 17 intact) and 9 females (7 spayed and 2 intact). The patients’ bodyweight ranged from 16 to 75 kg (mean: 33.5 kg).All dogs had unilateral thoracic limb lameness. The distribution of the affected limbs distribution was 16 on the right and 11 on the left. Intermittent or waxing–waning lameness was the admitting complaint for all dogs. The median lameness grade evaluated in the entire population was 3 (3.19 ± 0.62). The median duration of clinical signs was 4.7 months (range: 1.5–18 months). All dogs were previously treated with rest and administration of NSAIDs or corticosteroids for 7 to 14 days, without clinical improvement. Pain on flexion of the shoulder and on palpation of the insertion of the supraspinatus tendon was the most consistent finding during the orthopedic examination, occurring in every dog. Median pain grade was two (2.07 ± 0.55). The biceps tendon test in the German-speaking literature was subjectively graded as positive in 3 out of 27 and negative in 24 out of 27.The radiographs showed that 24 out of 27 pathologic shoulders had no radiographic abnormalities, 2 out of 27 had signs of slight shoulder osteoarthritis characterized by the presence of osteophytes in the caudal portion of the humeral head, 1 out of 27 had a deficit of the bicipital groove filling according to a positive-contrast radiographic study. Synovial fluid examination was performed in 16% of the cases and the results of the cytologic examination were compatible with degenerative joint disease.During the MRI evaluation, a marked hyperintense signal localized to the insertion of the supraspinatus muscle was found in all of the examined shoulders in the STIR images .The tendon of the supraspinatus muscle was severely enlarged in 3 out of 27 of the cases. Five MRI images revealed compression of the biceps brachii tendon sheaths, while 10 out of 27 of the biceps brachii tendon sheaths were distended. Moreover, an effusion was present in the sheath of the tendon of the infraspinatus muscle in 1 one out of 27 of the cases and in the sheath of the biceps brachii muscle in 1 out of 27 of the cases.MRI abnormalities of the tendon of the subscapularis muscle were detected in one dog. No MRI abnormalities of the medial and lateral glenohumeral ligament were detected.Signs of nonmineralized supraspinatus tendinopathy were present on the contralateral forelimb in 10 out of 27 dogs.In all the dogs, surgery was performed by the same surgeon only in the shoulder affected by lameness. Intra-articular abnormalities were arthroscopically observed in 13 out of 27 shoulders and consisted of fibrillation of the medial glenohumeral ligament in 3 out of 27 cases, partial rupture of the tendon of the subscapularis muscle in 7 out of 27 cases and laxity of the tendon of the subscapularis muscle in 3 out of 27 cases .The arthroscopic and MRI findings were in agreement about the absence of intra-articular shoulders abnormalities in 10 out of 27 shoulders. In 13 out of 27 shoulders, the ectasia of biceps brachii tendon was detected with MRI but was not recognized with arthroscopy. In 9 out of 27 shoulders, lesions of the subscapularis tendon, not previously established with MRI, were diagnosed by arthroscopy. In 3 out of 27 shoulders, laxity of the medial glenohumeral ligament, not previously diagnosed with MRI, was observed by arthroscopy. In 27 out of 27 shoulders, both MRI and arthroscopy were in agreement about the lateral glenohumeral ligament integrity. No intra-operative complications were reported. No dogs required physical rehabilitation in the post-operative period.A biopsy sample of the supraspinatus tendon from all 27 dogs was submitted for histological evaluation. The sample was collected from the area of maximum thickness of the tendon, at the musculotendinous junction. The histological examination of the tissue specimens revealed discontinuous and disorganized collagen fibers that lacked reflectivity under polarized light in all specimens. The most prominent finding was severe myxomatous degeneration, with the remaining collagen separated by a palely basophilic myxoid matrix and edema.On Day 10, 21 out of 27 cases showed a lower lameness score compared with the pre-operative values. Lameness was classified subjectively as Grade II in 21 out of 27 cases, Grade III in 5 out of 27 cases and Grade IV in 1 out of 27 cases. There was a lack of improvement in lameness in 6 out of 27 cases: in 4 out of 27 cases, the lameness remained the same, while worsening lameness from Grade III to Grade IV and from Grade II to Grade III was observed in 2 out of 27 cases. A fluctuant mass the size of a golf ball was detected under the healed incision in 5 out of 27 cases . It was On Day 30, lameness was graded as absent in 7 out of 27 cases, as Grade I in 5 out of 27, as Grade II in 11 out of 27 cases, as Grade III in 3 out of 27 and Grade IV in one dog. Dogs affected by co-existing supraspinatus tendinopathy and biceps brachii tendinopathy (T30 = 1.6 ± 0.9) showed longer functional recovery, characterized by higher mean values of lameness score, compared to the entire population (T30 = 0.74 ± 1.3), to dogs affected only by ST tendinopathy (T30 = 0.63 ± 1.4) or dogs affected by ST tendinopathy and concomitant subscapular tendon lesion (T30 = 1 ± 0.8) .The clinical outcome was judged to be unsatisfactory in the dog affected by Grade IV lameness, revision surgery was discussed with the owner, and supraspinatus tenectomy was performed.On Day 60, 17 out of 27 patients did not show any sign of lameness, 3 out of 27 still had Grade I lameness, 5 out of 27 had Grade II lameness, 1 out of 27 had Grade III lameness and I out of 27 had Grade IV lameness.All owners agreed to a telephone interview but only 13 out of 27 agreed to a clinical consultation, radiographic study of the shoulder joint and force plate analysis.Of the 13 dogs that had a long-term clinical evaluation, all had a complete range of motion of the joint and did not show any sign of pain during flexion or extension of the joint or under palpation of the supraspinatus tendon. The symmetry index was between 0.01 and 14.34, with a mean value of 3.19.A radiographic recheck of the surgically treated shoulder showed mild mineralization in 4 out of 13 dogs and mild degenerative joint disease in 2 out of 13 cases.Twenty-three owners declared that they were satisfied with the recovery of their dog after surgery, 2 out of 27 were mostly satisfied and 2 out of 27 remained unsatisfied.Twenty-two of the dogs did not show any sign of lameness on the treated limb, but 9 out of 27 showed some episodes of lameness, which were classified as mild.When the owners were asked if their pets presented any episodes of lameness on the other forelimb, 25 out of 27 owners answered that no alteration in the gait was noted in that limb.Gait was judged by the owners as normal in 19 out of 27 dogs, 3 out of 27 had a nearly normal gait, 3 out of 27 had slight but frequent difficulties, and in 2 out of 27 dogs, the difficulty was evident.The ability to stand up from a sitting position was normal in 12 out of 27 dogs, 8 out of 27 had slight and infrequent difficulties, 5 out of 27 had slight but frequent difficulties, and discomfort was evident in only one dog.The ability to run was normal in 19 out of 27 dogs, 3 out of 27 had slight and infrequent difficulties, 2 out of 27 had slight but frequent difficulties and 3 out of 27 owners were unable to answer this question.Nineteen of the dogs did not have difficulty during intense activity and play, 5 out of 27 had slight and infrequent difficulties, and only 3 out of 27 dogs had slight but frequent difficulties.Twenty-one dogs did not have any difficulty going downstairs and 5 out of 27 had slight and infrequent difficulties; one owner was not able to answer.After we added the scores of the different activities evaluated by the owners, the functional recovery was judged to be very good in 15 out of 27 dogs, good in 8 out of 27 and sufficient in 4 out of 27 dogs.In the literature, a breed-related predisposition to supraspinatus tendinopathy has been reported in Rottweilers and Labrador Retrievers ,3,7,9. ILafuente and colleagues  found a The dogs included in this study were affected by chronic lameness that was intermittent and worsened after physical activity. NSAIDs had been administered previously to all dogs, in association with steroids in some cases, for 7 to 14 days without clinical improvement. The cause of this nonresponse was associated with the degeneration and metaplasia of the tendon, without inflammation . In our The biceps test (in the German-speaking literature) was performed, and it was judged to be positive in 3 out of 27 cases but partial or complete rupture of the biceps brachii tendon was not subsequently confirmed neither by MRI nor arthroscopy. This can be explained by the fact that the biceps test is an extremely subjective evaluation, and the response can be operator-dependent. Moreover, many of the dogs included in our study had a straight poise of the forelimbs, so the flexion of the shoulder determined the extension of the elbow, even if the biceps tendon was intact. This can lead one to erroneously suspect its breakage.In human medicine, the Hawkins test is described as a specific test for evaluating the supraspinatus tendon. The patient first flexes her/his arm by 90 degrees, then flexes her/his elbow by 90 degrees and intrarotates his/her shoulder. Pain indicates that the test is positive, and the pain is due to the compression of the biceps tendon by the tendon of the supraspinatus . In our In adult patients referred for shoulder lameness, it is always necessary to carry out a orthogonal comparative radiographic study even if the majority of shoulder pathologies involve the tenoligamentous structures ,34. A raIn our study, we examined the synovial fluid in only 16% of the cases, but we considered this to be a mistake during the diagnostic process. It is advisable to include a cytologic examination of the synovial fluid in the diagnostic work out in order to rule out pathologies such as neutrophilic arthrosynovitis before considering MRI of the shoulder.In the dogs included in this study, given the negative results of the radiographic and synovial liquid exams, we advanced nonmineralized tendinopathy of the supraspinatus as a probable diagnosis, and we informed the owners that this diagnosis could be confirmed through ultrasound examination or magnetic resonance imaging . With thThe common alteration revealed by MRI in patients affected by nonmineralized tendinopathy is an enlargement and a marked increase in the signal in the insertion area of the supraspinatus tendon above the greater tubercle of the humerus in the STIR sequences. In a recent study, it was noticed that pathologic tendons, in addition to an alteration in the signal, also present an increase in volume . In our The alterations indicated by MRI must always be associated with the clinical data.In our case studies, it was interesting to note that there was some discrepancy in the evaluation of the shoulder joint when we compared the findings of MRI and arthroscopy in the biceps and subscapularis tendons and the medial collateral ligament. Regarding the biceps tendon, MRI highlighted an ectasia in 10 out of 27 cases that was not confirmed by arthroscopy. Arthroscopy indicated a partial rupture and laxity of the subscapularis tendon in 10 out of 27 cases that was not highlighted in 9 out of 27 cases through MRI. Finally, arthroscopy highlighted laxity of the medial collateral ligament in 3 out of 27 cases that was not displayed in MRI in 0 out of 3 cases. For this reason, as arthroscopy is a minimally invasive technique which requires a short prolongation of the patient’s anesthesia with a very low incidence of complications, it is considered useful to always carry it out before surgery, as it often provides useful information for understanding the pathology and the prognosis of the patient. As well as ultrasound, evaluation by MRI imaging presents minimal variability caused by the operator’s experience. Having a good evaluation of the means of intra-articular stability is also fundamental for evaluating the prognosis and for the functional recovery of the patients treated surgically. In our case studies, 37% of cases had a subscapularis tendon injury that can lead to the persistence of lameness in the post-operative period, which must be discussed with the owners.Dogs at our institution affected by supraspinatus tendinopathy had a mechanical alteration of the gait that led them to abduction of the limb. We argue that this gait alteration may be the cause of the torn subscapularis tendon or the partial rupture of the medial collateral ligament, which were often observed in our population; otherwise, these lesions can be considered to be concomitant to the nonmineralized supraspinatus tendinopathy. It is reasonable to consider those lesions as of lesser regard because the lameness often resolves after the treatment of the supraspinatus tendinopathy alone. Dogs included in this study that presented a concomitant injury to the subscapularis tendon or medial collateral ligament were treated in the post-operative period  using deIn our cases, slower functional recovery with a protracted lameness was reported in patients affected by concomitant supraspinatus and biceps brachii tendinopathy. It is supposed that, if not treated, the biceps brachii tendinopathy might have a consistent influence on the post-operative lameness score compared with the other concomitant lesions observed by means of arthroscopy or by MRI.In the literature, the craniomedial surgical approach has been reported for executing splitting of the supraspinatus tendon ,37. In oThe execution of tendon splitting is easy and involves making longitudinal release incisions at the level of the muscle–tendon junction ,37. ThisThe histopathologic examination of collected samples highlighted severe myxomatous degeneration, with the remaining collagen separated by a palely basophilic myxoid matrix and edema. Pownder et al.  suggesteThe visual and histological examination of some tendinous portions highlighted the presence of mineralized foci in the tendon samples of subjects affected by the nonmineralized form of the pathology. This may support the theory that the nonmineralized tendinopathy is an initial phase of the more common mineralized form, so we can suppose that in dogs with the nonmineralized form, the mineralized form could develop over time if surgery is not carried out. Some authors affirm that degeneration of the tendon can follow a cycle of degeneration and regeneration. Interruption of this cycle can cause the progressive formation of mineralized foci and the development of clinical signs ,39,40,41In 21 out of 27 (77%) patients, there was a marked improvement in lameness after the removal of stitches 10 days after surgery. The 30-day follow-up was satisfactory in 81% of cases, but in only one case, we decided, given the persistence of marked lameness, in favor of surgical re-intervention. During the surgery, fibrosis was observed in the portion where the tendon splitting had been performed, so we executed a partial tenectomy of the tendon, which led to rapid remission of the symptoms.To our knowledge, long-term follow-up of patients affected by the mineralized or nonmineralized forms of supraspinatus tendinopathy has never been reported in the literature. Anecdotally, according to some surgeons, it would be better to perform a complete tenectomy to avoid the risk of recurrence. In our study, we performed a long-term follow-up between 6 and 9 months after the surgery. The long-term follow-up included a telephone interview, and clinical and radiological examinations. In 85% of patients, the result was considered to be satisfactory by the owners and, in 81% of the cases, lameness was no longer reported. These data support the efficacy of the tendon splitting technique for the treatment of nonmineralized supraspinatus tendinopathy.Furthermore, the long-term follow-up allowed us to highlight how although the MRI had shown an alteration in the STIR signal in the contralateral limb in 11% of cases, none of these patients ever became symptomatic. This shows how the alterations found by MRI must always be supported by clinical data to have value; therefore, it is not necessary to perform surgery for preventive purposes in the absence of symptoms.For cases in which it was possible to execute the force plate examination in the long-term clinical examination, we observed a low symmetry index, with an average value of 1.58. As demonstrated by Grandjean e Fanchon, this value, being less than 3.2, can be considered physiological ,42,43.This study has the implicit limitations of retrospective studies. One limit is related to the fact that the information was extracted retrospectively from the medical records. Another limitation is related to the impossibility of executing a long-term clinical follow-up in some patients; therefore, the data obtained have a limited value because they are based on the subjective judgement of the owners. However, it is believed that the owners are able to effectively evaluate their dog in the home environment, which is why the owner’s opinion should not be underestimated as part of the evaluation of the results .In conclusion, we can affirm that supraspinatus tendinopathy is a common pathology in medium to large breeds of dog weighing more than 20 kg. The treatment of tendinopathy is a quick and easy procedure to perform, with no intra-operative complications and a low incidence of minor (18%) and major (4%) complications. In order to avoid complications and the necessity of revision surgery, it is considered fundamental to make the incisions of the splitting procedure exactly between the muscular and tendinous junctions of the supraspinatus muscle, taking care to avoid any damage to the tendon of the biceps brachii muscle. The dogs enrolled in the study showed a satisfactory functional recovery. The resolution of lameness was achieved in 80% of the cases without any further lameness episodes in the long-term follow-up.