Sheep Tibia Research Articles

RADIOGRAPHIC EVALUATION OF BONE DENSITY AFTER IMPLANTATION OF 3D BIPHASIC CALCIUM PHOSPHATE ALGINATE SCAFFOLD ON LOCAL SHEEP (OVIS ARIES)

This study aims to; 1) evaluate the osteogenesis ability of Biphasic Calcium Phosphate (BCP)-alginate 70/30 based on chages in size of defect and relative bone density, 2) implant response tissue based on relative muscle density peri implant. The BCP used in this study made from hydroxyapatite (HA) 70, tricalcium phosphate (TCP) 30 and alginate as porogen. The implant material made in 3D form and have diameter porous 200-400 ìm which similar size with the bone trabecula. This study used three local sheep (Ovis aries) male 1.5 years old, weight average 20 kg. The implant material is grown on the right sheep tibia. As a control, the left tibia is made defective with no implantable material. Evaluate osteogenesis and implant tissue responses using radiography and assess the grey values of a particular area. Osteogenesis is also assessed based on the size of the defect. Based on the size of the defect, the right defect shows no significant value. The size of the left defect shows a significant value between day 0 and day 30, and 90. The relative bone density of the right defect shows a significant value between day 7 and 30. In the left defect, the relative bone density shows the significant between 0 and 90. The relative density of the muscle does not show significant values either on the right or left defects.

Tissue deformation controlling fracture healing

To achieve optimal flexibility in biological internal fracture fixation two questions require clarification: which biomechanical parameter controls healing and what are the boundary conditions thereof? Fracture movement interacts with callus and local stress and strain are influencing the reaction of the tissue cells. A linear gradient of strain was created inside a sheep tibia osteotomy using an active external fixator. The effect of different amounts of strain applied at 10 stimulation cycles/day on the occurrence of callus and on enabling osseous connection of the fragments was evaluated using micro-radiology to determine the amount of calcified new bone formation and its quality of gap bridging.A strong relation between level of strain and amount of callus was observed. Depending on the strain level different pattern of connections were seen. At the lowest investigated gap strain level of about 7% direct connection of the fragments within the gap occurred. Beyond 13% the callus only connected indirectly outside the gap. At over 36% callus did not connect the fragments anymore comparable to a situation in hypertrophic non-unions.The observed strong relation between interfragmentary strain and reduced osseous bridging may support the hypothesis that the elongation at rupture of connecting tissue plays an important role defining the upper limit for solid bridging. In planning fracture treatment, the amount of fracture mobility resulting in interfragmentary strain may play a crucial role to achieve solid healing.

Investigation of a Prevascularized Bone Graft for Large Defects in the Ovine Tibia

In vivo bioreactors are a promising approach for engineering vascularized autologous bone grafts to repair large bone defects. In this pilot parametric study, we first developed a three-dimensional (3D) printed scaffold uniquely designed to accommodate inclusion of a vascular bundle and facilitate growth factor delivery for accelerated vascular invasion and ectopic bone formation. Second, we established a new sheep deep circumflex iliac artery (DCIA) model as an in vivo bioreactor for engineering a vascularized bone graft and evaluated the effect of implantation duration on ectopic bone formation. Third, after 8 weeks of implantation around the DCIA, we transplanted the prevascularized bone graft to a 5 cm segmental bone defect in the sheep tibia, using the custom 3D printed bone morphogenic protein 2 (BMP-2) loaded scaffold without prior in vivo bioreactor maturation as a control. Analysis by micro-computed tomography and histomorphometry found ectopic bone formation in BMP-2 loaded scaffolds implanted for 8 and 12 weeks in the iliac pouch, with greater bone formation occurring after 12 weeks. Grafts transplanted to the tibial defect supported bone growth, mainly on the periphery of the graft, but greater bone growth and less soft tissue invasion was observed in the avascular BMP-2 loaded scaffold implanted directly into the tibia without prior in vivo maturation. Histopathological evaluation noted considerably greater vascularity in the bone grafts that underwent in vivo maturation with an inserted vascular bundle compared with the avascular BMP-2 loaded graft. Our findings indicate that the use of an initial DCIA in vivo bioreactor maturation step is a promising approach to developing vascularized autologous bone grafts, although scaffolds with greater osteoinductivity should be further studied. Impact statement This translational pilot study aims at combining a tissue engineering scaffold strategy, in vivo prevascularization, and a modified transplantation technique to accelerate large segmental bone defect repair. First, we three-dimensional (3D) printed a 5 cm scaffold with a unique design to facilitate vascular bundle inclusion and osteoinductive growth factor delivery. Second, we established a new sheep deep circumflex iliac artery model as an in vivo bioreactor for prevascularizing the novel 3D printed osteoinductive scaffold. Subsequently, we transplanted the prevascularized bone graft to a clinically relevant 5 cm segmental bone defect in the sheep tibia for bone regeneration.

Axial Micromotion Locking Plate Construct Can Promote Faster and Stronger Bone Healing in an Ovine Osteotomy Model.

Fixing bone fractures with controlled axial interfragmentary micromotion improves bone healing; however, the optimal type of implant construct for this purpose is still lacking. The present study describes a novel axial micromotion locking plate (AMLP) construct that allows axial interfragmentary micromotion of 0.3 or 0.6 mm. We investigated whether the AMLP constructs enhance bone healing compared to an ordinary locking plate (LP) using an ovine osteotomy model. The stiffness of the constructs was tested under axial loading. We created a 3-mm osteotomy in the left hind leg tibia of sheep that was then stabilized with a 0.3- or 0.6-mm AMLP or LP construct (n = 6/group). Bone healing was monitored weekly by X-ray radiography starting from week 3 after surgery. At week 9, the specimens were collected and evaluated by computed tomography and torsional testing. We found that the AMLPs had a lower stiffness than the LP; in particular, the stiffness of the 0.6-mm AMLP construct was 86 and 41% lower than that of the LP construct for axial loads <200 and >200 N, respectively. In the in vivo experiments, tibial osteotomies treated with the 0.6-mm AMLP construct showed the earliest maximum callus formation (week 5) and the highest volume of bone callus (9.395 ± 1.561 cm3 at week 9). Specimens from this group also withstood a 27% greater torque until failure than those from the LP group (P = 0.0386), with 53% more energy required to induce failure (P = 0.0474). These results demonstrate that AMLP constructs promote faster and stronger bone healing than an overly rigid LP construct. Moreover, better bone healing was achieved with an axial micromotion of 0.6 mm as compared to 0.3 mm.

The investigation of bone fracture healing under intramembranous and endochondral ossification

After trauma, fractured bone starts healing directly through bone union or indirectly through callus formation process. Intramembranous and endochondral ossification are two commonly known mechanisms of indirect healing. The present study investigated the bone fracture healing under intramembranous and endochondral ossification by developing theoretical models in conjunction with performing a series of animal experiments. Using experimentally determined mean bone densities in sheep tibia stabilized by the Locking Compression Plate (LCP) fixation system, the research outcomes showed that intramembranous and endochondral ossification can be described by Hill Function with two unique sets of function parameters in mechanical stimuli mediated fracture healing. Two different thresholds exist within the range of mechanical simulation index which could trigger significant intramembranous and endochondral ossification, with a relatively higher bone formation rate of endochondral ossification than that of intramembranous ossification. Furthermore, the increase of flexibility of the LCP system and the use of titanium LCP could potentially promote uniform bone formation across the fracture gap, ultimately better healing outcomes.

BonoFill-II, from bench to bedside: A novel autologous cell-based, tissue-engineered product in line to replace bone autografts for large segmental bone defect applications

Background & Aim Significant losses of bone tissues that are often too large to heal occur in >10% of all open fractures and present an urgent clinical challenge associated with grave morbidities and huge healthcare costs. Bone autografting, the therapeutic standard in such cases, has a 50% complication rate, with persistent infection or non-union present in 18% of the patients, and further surgery required in 36% of them. Bone tissue engineering technologies have been widely suggested as an alternative to autografts. Such technologies were tested in segmental animal bone defects up to 5 cm long, with success reported mostly for defects under 2.5 cm. This size (or equivalent product volume) is also the upper limit for tissue-engineered bone grafts in clinical development. Considering that much larger defects, with a mean of 5.5 cm, are encountered in the clinic, Bonus is developing autologous tissue-engineered bone grafts for the treatment of defects larger than 2.5 cm. Methods, Results & Conclusion Bonus utilizes proprietary procedures to isolate adipose tissue-derived mesenchymal cells from patients’ lipoaspirates, seed them on mineral scaffold particles, and culture them in a specially designed bioreactor (Fig. 1). The expansion of the cells on this scaffold increases their osteo-inducibility, allowing a controlled osteoinduction process that possibly also retains some of these cells’ additional regenerative functions. This possibility is exemplified by the higher levels of osteogenic and other genes related to angiogenesis and ECM remodeling expressed by 3D-osteoinduced cells, compared to the 2D ones. After their osteoinduction, the cells and scaffold are washed and formulated into the final product—BonoFill-II. In a preclinical study, BonoFill-II applied to a 3.2 cm defect in a sheep tibia led to a full recovery in 12 weeks (N=7), as well as a full bridging of a 10.5 cm defect (Fig. 2). A phase I/II clinical trial is currently underway testing BonoFill-II in patients with bone defects ≥2.5 cm. So far, we have treated patients with defects up to 8.5 cm long and a history of 2-7 failed prior interventions, with a few representatives that can exemplify this study safety and efficacy (Fig. 3). The performance of BonoFill-II was also tested in Phase I/II trial in patients in need of a bone transplant in the upper maxilla with complete success reported. Overall, the solid underlying science and innovative technologies developed by Bonus position BonoFill-II as a promising alternative to bone autografts.

Evaluation of strontium-containing hydroxyapatite as bone substitute in sheep tibiae.

With the advancement of research in biomaterials, it has been suggested that the best osteoconductivity of hydroxyapatite would be achieved if its crystal were closer to the structure, size and morphology of biological apatite, that is why nano-hydroxyapatite (nano-HA) is of great importance. current interest. Strontium ions are known to reduce bone resorption, induce osteoblastic activity and stimulate bone formation. The aim of this study was to evaluate biocompatibility and osteoconduction in surgical defects filled with nano-hydroxyapatite microspheres containing 1% strontium (nano-SrHA), stoichiometric nano-HA microspheres (nano-HA) compared to the clot (control) . Four Santa Inês sheep, weighing an average of 32 kg, were anesthetized and submitted to three 2 mm diameter perforations in the medial face of the tibia. The surgical defects were filled with blood clot, microspheres of Sr-HA 1% and microspheres of HA. After 30 days the samples were drawn (6 mm), decalcified, processed for inclusion in paraffin and stained with hematoxylin and eosin (HE) for histological evaluation with light microscopy. All groups revealed bone neoformation from the periphery to the center of the defect, with the nano-SrHA group being less intense among those studied. Presence of a discrete mononuclear inflammatory infiltrate in all experimental groups. Giant foreign body cells were only observed in the HA group. Areas of bone neoformation were observed in close contact with both biomaterials. According to the results obtained, microspheres of HA and SrHA 1% are biocompatible and have osteoconductive properties.

Autologous cell-coated particles for the treatment of segmental bone defects\u2014a new cell therapy approach

BackgroundAdipose tissue-derived mesenchymal stem cells (AT-MSCs) are one of the most potent adult stem cells, capable of differentiating into bone, cartilage, adipose, muscle, and others. An innovative autologous AT-MSC-derived cell-based product (BonoFill-II) for bone tissue regeneration was developed to be suited as a bone graft for segmental bone defects.MethodsBonoFill-II was transplanted into 8 sheep with 3.2-cm full cortex segmental defect formed in the tibia. Bone regeneration was followed by X-ray radiographs for 12 weeks. At experiment termination, the healed tibia bones were analyzed by computed tomography, histology, and mechanical tests.ResultsOur results indicate that one dose of BonoFill-II injectable formula led to an extensive bone growth within the transplantation site and to a complete closure of the critical gap in the sheep’s tibia in a relatively short time (8–12 weeks), with no inflammation and no other signs of graft rejection. This new and innovative product opens new prospects for the treatment of long bone defects.ConclusionsInjection of BonoFill-II (an innovative autologous cell therapy product for bone tissue regeneration) into a critical size segmental defect model (3.2 cm), generated in the sheep tibia, achieved full bridging of the gap in an extremely short period (8–12 weeks).

Zooarchaeological Collection from Bolshepichuginsky Kurgan Burial Mound (According to the Excavations in 2013–2016)*

Numerous animal remains are part of burial practice in Tagar culture, therefore researches conducted to determine anatomic, specific, and age structure of zooarchaeological assemblages in certain tombs and whole cemeteries, their peculiarities and comparative analysis. The paper features an analysis of the faunistic collections from the kurgan burial mound of Tagar culture Bolshepichugino I (VI century – C.E.). In total, 75 samples from kurgan 13 were described and 2192 – from kurgan 16 have. The zooarchaeological assemblages consist of remains of a horse, cattle, and sheep, fox, doe, Asian badger, mountain hare, and birds. The peculiarities of the associated food were determined (scapula, 3–4 ribs, femur, and tibia of cattle and sheep). The use of right parts of animal bodies is discussed in the context of burial practice in the Early Tagar period. Remains of young animals (younger than 1 year) were also found in the materials. It is supposed that the burial mounds were made in winter time. Some domestic and wild bone assemblages located in different places of the kurgans are considered to belong to another period and culture or zoogenic processes. A special attention is paid to the doe and fox remains in the tombs since their carcasses might have been used in burial rituals. In total, the composition and specifics of zooarchaeological materials make it possible to speak about similarity of forest-steppe and steppe early Tagar assemblages in this aspect of burial practice.

Electroactive Nanocomposite Porous Scaffolds of PAPn/op-HA/PLGA Enhance Osteogenesis in Vivo.

The three-dimensional (3D) porous nanocomposite biomimic scaffolds with electroactivity and bioactivity were prepared as bone implants by a freeze-drying method using 1,4-dioxane as a solvent. The multiblock copolymer (PAPn) was synthesized by the condensation polymerization of hydroxyl-capped poly(lactide)(PLA) and carboxyl-capped aniline pentamer (AP), which were introduced as electroactive functional polymers. A bioactive component, hydroxyapatite (HA) grafting l-lactic acid oligomer (op-HA), showed a better interface compatibility with PAPn and poly(lactide-co-glycolide) (PLGA). Honeycomb-like and interconnected porous structures could be obtained as displayed by scanning electron microscopy (SEM). The intramuscular implants showed a good biocompatibility and higher osteogenetic activity by promoting cell ingrowth and collagen fibers forming as indicated by SEM, hematoxylin-eosin (H&E) staining, and Masson's trichrome staining. Implantation for the repair of rabbit radius defects under 5 V at 100 Hz with a 50% duty cycle for 30 min every other day was evaluated, and sheep tibia defects were also carried out. The composite scaffold with 1 wt % PAPn exhibited better behaviors, such as a distinct bone callus, bridging growth, vague borderlines between newly formed bone at the two defect ends, and increased bone density as indicated by radiographic images and micro-computed tomography (Micro-CT) images. Electricity stimulation could significantly accelerate the healing of a fracture. All in all, the stimuli-responsive electroactive nanocomposites showed a potential application in bone tissue engineering.

A Novel Bone Substitute with High Bioactivity, Strength, and Porosity for Repairing Large and Load-Bearing Bone Defects.

Achieving adequate healing in large or load-bearing bone defects is highly challenging even with surgical intervention. The clinical standard of repairing bone defects using autografts or allografts has many drawbacks. A bioactive ceramic scaffold, strontium-hardystonite-gahnite or "Sr-HT-Gahnite" (a multi-component, calcium silicate-based ceramic) is developed, which when 3D-printed combines high strength with outstanding bone regeneration ability. In this study, the performance of purely synthetic, 3D-printed Sr-HT-Gahnite scaffolds is assessed in repairing large and load-bearing bone defects. The scaffolds are implanted into critical-sized segmental defects in sheep tibia for 3 and 12 months, with bone autografts used for comparison. The scaffolds induce substantial bone formation and defect bridging after 12 months, as indicated by X-ray, micro-computed tomography, and histological and biomechanical analyses. Detailed analysis of the bone-scaffold interface using focused ion beam scanning electron microscopy and multiphoton microscopy shows scaffold degradation and maturation of the newly formed bone. In silico modeling of strain energy distribution in the scaffolds reveal the importance of surgical fixation and mechanical loading on long-term bone regeneration. The clinical application of 3D-printed Sr-HT-Gahnite scaffolds as a synthetic bone substitute can potentially improve the repair of challenging bone defects and overcome the limitations of bone graft transplantation.

Healing at sites prepared using different drilling protocols. An experimental study in the tibiae of sheep

The aim of the experiment was to study the healing at implants installed in site prepared in bone type 1 using different rotation speeds and cooling strategies. The tibiae of twelve sheep were used as experimental sites. Two implant sites were prepared in each tibia using drills either at a high or a mixed speed under irrigation. At the mixed-speed sites, 60 rpm without irrigation were applied for the last drill, the countersink and during implant installation. Biopsies representing the healing after 1, 2, and 6 weeks were obtained and ground sections were prepared. At the histological analyses, after 1 week of healing, no new bone was found at both high- and mixed-speed sites. After 2 weeks of healing, small amounts of newly formed bone were observed in the cortical layer, reaching percentages of 3.6±3.0% at the mixed-speed sites, and of 2.2±1.5% at the high-speed sites. An irrelevant quantity of new bone was seen in the marrow compartments of a few specimens. After 6 weeks of healing, new bone was found in higher quantity, reaching in the cortical compartment 66.9±6.8% and 67.3±17.7% at the mixed- and high-speed sites, respectively. The respective percentages in the marrow compartment were 23.2±13.0% and 30.6±29.2%. No statistically significant differences between high- and mixed-speed groups were found. It was concluded that the use of the last drill and the installation of the implant with or without irrigation yielded similar bone healing and osseointegration.

Effects of Material-Tissue Interactions on Bone Regeneration Outcomes Using Baghdadite Implants in a Large Animal Model.

Extensive bone loss due to trauma or disease leads to impaired healing. Current bone grafts and substitutes have major drawbacks that limit their effectiveness for treating large bone defects. A number of bone substitutes in development are undergoing preclinical testing, but few studies specifically investigate the in vivo material-tissue interactions that provide an important indicator to long-term implant safety and efficacy. This study is the first of its kind to specifically investigate in vivo material-tissue interactions at the bone-implant interface. Baghdadite scaffolds implanted in critical-sized segmental defects in sheep tibia for 26 weeks are analyzed by focused ion beam scanning electron microscopy, multiphoton microscopy, and histology. The scaffolds are seen to induce extensive bone formation that directly abut the implant surfaces with no evidence of chronic inflammation or fibrous capsule formation. Bone remodeling is influenced by slow in vivo degradation around and within the implant, causing portions of the implant to be incorporated into the newly formed bone. These findings have important implications for predicting the long-term effects of baghdadite ceramics in promoting defect healing, and support the translation of baghdadite scaffolds as a new generation of bone graft substitutes with improved properties for the repair of large bone defects.

Micromotion Phenomena at the Implant Bone Interface: A Biomechanical and Histomorphometric Study

Purpose: Excessive micromotion at the implant-bone interface may result in fibrous encapsulation instead of osseointegration of dental implants. This study quantified micromotion of implants placed in polyurethane foam and sheep tibia and tried to establish correlations with histologic parameters. Method: Dental implants (n=5) were placed in the tibiae of two sheep and allowed to heal for five and twenty weeks respectively (totalof 10 implants). Identical implants were placed in polyurethane foam with densities of 10 pcf and 20 pcf and a 3 mm thick cortical layer with a density of 40 pcf (n=5 per bone type; total of 10 implants). For determining micromotion at the implant bone interface, specimens were loaded in a universal testing machine and extensometers were used for recording implant displacement during loading. Implant stability, bone mineral density (BMD) and bone to implant contact (BIC) were determined additionally. Statistical analysis was based on Wilcoxon rank sum tests and Spearman rank correlation tests with the level of significance set at p&lt;=0.05. Results: An increase in trabecular bone density and healing time caused a basic trend towards greater implant stability (p&lt;0.05 for polyurethane foam; p&gt;0.05 for sheep) and less implant displacement as a consequence of loading. The histologic parameters BIC and BMD also increased with healing time, however, this effect was only significant for BMD in the cervical (p=0.02) and apical (p=0.05) part. No difference in micromotion was found between implants placed in sheep and those placed in polyurethane foam with trabecular density of 10 pcf. Only few and inconsistent correlations were found between the parameters evaluated. Conclusions: Bone quality seems to affect implant micromotion although the exact determinants remain unclear. Implants placed in cellular polyurethane foam with density 10 pcf combined with a 3 mm layer of solid foam with density 40 pcf showed biomechanical behavior comparable to implants placed in sheep tibia.

Biomechanical analysis of controlled tibial blunt force trauma

The analysis and interpretation of skeletal injuries caused by blunt force trauma (BFT) is often critical to reconstructing a victim’s osteological profile. The manner in which bone fractures in response to BFT is a complex multiphasic process that involves interactions between mechanical force, skin and the musculo-skeletal system. To further improve our understanding of how bone fractures under mechanical force, this study investigated whether a quantifiable relationship was discernible between force and specific fracture outcomes (maximum fracture length, total fragment count and total anterior/posterior radiating fracture lines) and how anatomical factors influenced those outcomes. Fleshed sheep tibiae (Ovis aries, n = 30) were subjected to three conditions of force (90 N, 112 N and 135 N), ten tibiae at each force. Results indicate that a significant relationship exists between force and fracture length with respect to 90 N and 112 N force outcomes. No significant relationship was discernible between the level of force and the outcome variables of total fragment count and total anterior/posterior radiating fracture lines. These preliminary results suggest there is potential for further analysis of bone fracture behaviour under mechanical force with consideration to a broader suite of soft tissue and skeletal variables.

Ugrađivanje navojnog šrafa u otvor zaključavajuće ploče na mestu preloma može povećati čvrstinu ploče na opterećenja - biomehanička studija

Objectives: This study aimed to evaluate whether placing a threaded plug in the hole of a locking plate at the fracture level is beneficial for increasing the resistance of the plate. Methods: This experimental study analyzed load and compression forces in sheep tibia bone models. The following groups were assessed: Group 1 (n = 4), control bone samples; Group 2 (n = 4), samples of screw plate fixation without threaded plug in the hole at the fracture level; and Group 3 (n = 4), samples of screw plate fixation with a threaded plug in the hole at the fracture level. Elastic force, bending moment, elastic compression, and rigidity were evaluated using a three-point bending test. Results: Group 1 showed the greatest elastic force and the least amount of compression. The rigidity and elastic force were better in Group 3 than in Group 2. The mean elastic force in Group 3 was 22.4% of that in Group 1, whereas the mean elastic force in Group 2 was 19% of that in Group 1. Rigidity in Group 3 was 24.7% of that in Group 1, whereas rigidity in Group 2 was 18.3% of that in Group 1. Improved results were obtained in Group 3 when compared with Group 2. Conclusions: Our results suggest that placing a threaded plug in the hole of the plate at the fracture level provides additional rigidity and stability by improving resistance to loading forces, but the differences were not statistically significant.

Novel systems for the application of isolated tensile, compressive, and shearing stimulation of distraction callus tissue.

BackgroundDistraction osteogenesis is a procedure widely used for the correction of large bone defects. However, a high complication rate persists, likely due to insufficient stability during maturation. Numerical fracture healing models predict bone regeneration under different mechanical conditions allowing fixation stiffness optimization. However, most models apply a linear elastic material law inappropriate for the transient stresses/strains present during limb lengthening or segment transport. They are also often validated using in vivo osteotomy models lacking precise mechanical regulation due to the unavoidable stimulation of secondary interfragmentary motion during ambulation under finitely stiff fixation. Therefore, in order to create a robust numerical model of distraction osteogenesis, it is necessary to both characterize the new tissue’s viscoelasticity during distraction and determine the influence of strictly isolated stimulation in each loading mode (tension, compression, and shear) to account for potential differences in mechanical and histological response.AimTwo electromechanical fixators with integrated load cells were designed to precisely perform and monitor in vivo lateral distraction and isolated stimulation in sheep tibiae using a mobile, hydroxyapatite-coated titanium plate. The novel surgical procedure circumvents osteotomy, eliminating the undesirable and unquantifiable mechanical stimulation during ambulation.MethodsAfter a 10-day post-surgery latency period, two 0.275 mm distraction steps were performed daily for 10 days. The load cell collected data before, during, and after each distraction step and was terminated after no less than one minute from the time of distraction. A 7-day consolidation period separated the distraction phase and 18-day stimulation phase. Stimulation was carried out in isolated tension, compression, or shear while recording force/time data. Each stimulation session consisted of 120 cycles with a magnitude of either 0.1 mm or 0.6 mm in the tension and compression groups and 1.0 mm in the shear group. The animals were euthanized after a 3-day holding period following stimulation.ResultsOur initial results show that the tissue progressively stiffens and maintains an increasingly large residual traction. The force curves during compressive stimulation show a progressive drift from compression toward tension. We hypothesize that this behavior may be due to the preferential flow of fluid outward from the tissue and a greater resistance to reabsorption during the plate’s return to the starting position.

Antibiotic-eluting orthopedic device to prevent early implant associated infections: Efficacy, biocompatibility and biodistribution studies in an ovine model.

Infection of orthopedic devices is a major complication in the postsurgical period generating important health issues and economic consequences. Prevention strategies could be based on local release of antibiotics from the orthopedic device itself to avoid adhesion and growth of bacteria. The purpose of this work is to demonstrate the efficiency to prevent these infections by a cefazolin-eluting, perforated stainless steel implant in an in vivo ovine model. The device was placed in the tibia of sheep, one group receiving cefazolin-loaded implants whereas the control group received empty implants. All implants were experimentally infected by direct inoculation of Staphylococcus aureus ATCC 6538. In vitro cytotoxicological studies were also performed to check the effect of antibiotic on cell viability, integrity, and cycle. Results showed that sheep receiving cefazolin-loaded devices were able to avoid implant-associated infections, with normal tissue healing process. The antibiotic release followed a local concentric pattern as demonstrated by high-performance liquid chromatography detection in tissues. The in vitro results indicate the lack of relevant cytotoxic effects for the maximum antibiotic concentration released by the device. These results demonstrate the efficiency and safety of cefazolin-eluting implants in an ovine model to prevent early postsurgical infections of orthopedic devices. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1976-1986, 2018.

Accelerated Healing Period with Hydrophilic Implant Placed in Sheep Tibia.

The objective of this study was to evaluate the early osseointegration of two different implants surfaces, a sandblasted and acid-etched surface (TN) compared with same geometry and surface roughness modified to be hydrophilic/wettable by conditioning in an isotonic solution of 0.9% sodium-chloride (TA) through histological and histomorphometric analysis after sheep tibia implantation. Forty dental implants, divided in two groups (TN and TA) were placed in the left tibia of twenty healthy, skeletally mature Santa Ines sheep (n=5/experimental period). After 7, 14, 21 and 28 days post-implantation, the samples were removed and the sheep were kept alive. Analysis of resin sections (30 μm) allowed the quantification of bone area (BA) and bone-to-implant contact (BIC). TA group presented nearly 50% increase in BA at 14 days (p<0.001, ANOVA - Tukey's post test) compared with 7 days. The TA presented higher values than the TN for BA and BIC at 14, 21, and 28 days after placement, stabilizing bone healing. TA hydrophilic surface promoted early osseointegration at 14 and 21 days compared to TN, accelerating bone healing period post-implant placement in sheep tibia.

Subchondral screw abutment: does it harm the joint cartilage? An in vivo study on sheep tibiae

PurposeSubchondral screw abutment in osteosynthesis of joint fractures is an effective method to achieve sufficient screw grip. In this study we investigated if subchondral screw placement is possible without harming the overlying subchondral plate and joint cartilage iatrogenic.Materials and MethodsA 3.5-mm conventional steel screw was placed in the tibia of ten sheep in distances between 1 and 7 mm beneath the joint cartilage. After a follow up of two and four months, evaluation of the subchondral bone and joint cartilage was performed by means of a histological osteoarthritis score, HRpQCT imaging and determination of the glycosaminoglycan content in the cartilage. The control group was the contralateral knee of the same animal.ResultsHistomorphometric evaluation of the Mankin osteoarthritis score revealed no significant difference compared to the control after two (p = 0.102) and four months (p = 0.429). No correlation between distance of the screw to the cartilage and histological scoring was found (p = 0.658, R2 = 0.04 after two months and p = 0.171, R2 = 0.18 after four months). HRpQCT measurements of the subchondral thickness between screw and cartilage after two (p = 0.05) and four months (p = 0.424) showed no significant difference. Mean glycosaminoglycan content in the treatment group compared to the control after two months (p = 0.25) and four months (p = 0.523) was not significant different.ConclusionIn conclusion subchondral screw abutment did not damage the joint cartilage after a two- and four-month follow up in this sheep model.