Empty Defects Research Articles

Physical, Chemical, and Mechanical Evaluation of Irradiated Xeno-Sheep Bony Implantation by Low-Level Laser Therapy of Long Bones Fractures in Rabbits.

Bone grafts/implantation is widely used in veterinary medicine. The present study aimed to evaluate the physical, chemical, and mechanical prosperities of irradiated xeno-sheepbony implantation(X-SBI) by low-level laser therapy (LLLT) implanted in the induced empty defect of the femoral bones in rabbits. A total of 10 adult rabbits were used to create a 1cm length of the femoral gab surgically; thereafter, the empty space was filled with X-SBI and internally fixed by intramedullary pinning with two femoral fragments. The operated rabbits were assigned to the un-irradiated control group 1 which was left without laser irradiation, and irradiated group (group 2) which was irradiated on a daily basis by a continuous diode laser, a single dose at four points at the lateral aspect of the X-SBI for 5 min at a period of 72 intervals for 14th days post-operation with a dosage of 850 nm, 148.4 J/cm2. The parameters which were used for the evaluation of results after 3rd-month post-operation were physical, chemical, and mechanical examinations. The physical examination revealed high bone density and hardness at the sites of X-SBI of the irradiated group, as compared to the un-irradiated animals. Moreover, the chemical analysis demonstrated an increment in the level of bone calcium and phosphorus elements, as well as a decrease in the level of magnesium, potassium, and sodium in the irradiated group, as compared to the un-irradiated group. The mechanical and fracture tolerance results demonstrated a gradually high resistance level of fracture tolerance of irradiated animals, as compared to un-irradiated rabbits. It can be concluded that the irradiated X-SBI by LLLT could be used strongly and successfully to fill the empty space in the femoral bone, supporting body weight better and faster than the control group, with no complications or body rejection.

Incorporation of hydroxyapatite into collagen scaffolds enhances the therapeutic efficacy of rhBMP-2 in a weight-bearing femoral defect model

Traditional methods to promote bone healing, such as autologous bone grafting, and therapeutic strategies involving recombinant bone morphogenetic proteins (BMPs), such as BMP-2 and BMP-7, have been associated with performance limitations and dose-related safety concerns, respectively. Thus, there is an unmet need for osteoinductive bone graft substitutes that can enhance the therapeutic efficacy of rhBMP-2 and facilitate dose-reduction approaches. This study aimed to determine the therapeutic efficacy of rhBMP-2 delivered using a collagen-only scaffold (CO) (representative of clinical standards), a collagen-hydroxyapatite scaffold (CHA), and a thermoresponsive hyaluronic acid hydrogel doped with gelatin and laminin (HyA-GL). Efficacy over 14 weeks was evaluated using 2 mm segmental femoral defects in skeletally mature female F344 rats, internally fixated using a 1.25 mm-thick polyetheretherketone plate. Empty defects failed to bridge but administration of rhBMP-2 using either CO or CHA scaffolds led to successful bridging, while using HyA-GL resulted in non-union. CHA scaffolds induced enhanced and stiffer new bone formation compared to both CO and HyA-GL scaffolds. Limited luminal remodeling occurred in both CO and CHA groups. Taken together, this study has determined that a collagen-hydroxyapatite scaffold can enhance the therapeutic efficacy of rhBMP-2 compared to collagen-only scaffolds routinely used in standard clinical practice.

Differences in platelet‐rich plasma composition influence bone healing

Platelet-rich plasma (PRP) is an autologous blood-derived material that has been used to enhance bone regeneration. Clinical studies, however, reported inconsistent outcomes. This study aimed to assess the effect of changes in leucocyte and PRP (L-PRP) composition on bone defect healing. L-PRPs were prepared using different centrifugation methods and their regenerative potential was assessed in an in-vivo rat model. Bilateral critical-size tibial bone defects were created and filled with single-spin L-PRP, double-spin L-PRP, or filtered L-PRP. Empty defects and defects treated with collagen scaffolds served as controls. Rats were euthanized after 2 weeks, and their tibias were collected and analysed using micro-CT and histology. Double-spin L-PRP contained higher concentrations of platelets than single-spin L-PRP and filtered L-PRP. Filtration of single-spin L-PRP resulted in lower concentrations of minerals and metabolites. In vivo, double-spin L-PRP improved bone healing by significantly reducing the size of bone defects (1.08 ± 0.2 mm3 ) compared to single-spin L-PRP (1.42 ± 0.27 mm3 ) or filtered L-PRP (1.38 ± 0.28 mm3 ). There were fewer mast cells, lymphocytes, and macrophages in defects treated with double-spin L-PRP than in those treated with single-spin or filtered L-PRP. The preparation method of L-PRP affects their composition and potential to regenerate bone.

Early Failure of a Polyvinyl Alcohol Hydrogel Implant With Osteolysis and Foreign Body Reactions in an Ovine Model of Cartilage Repair

Background: Hemiarthroplasty using a polyvinyl alcohol (PVA) hydrogel synthetic implant has been suggested as a good alternative to arthrodesis for the treatment of hallux rigidus. However, failure rates as high as 20% have been recorded. Purpose: To characterize the pathological processes in bone, cartilage, and the synovial membrane after PVA hemiarthroplasty in an ovine model with 6 months of follow-up. Study Design: Controlled laboratory study. Methods: A unilateral osteochondral defect (8-mm diameter × 10-mm depth) was made in the medial femoral condyle in 6 sheep. Animals were randomized to receive a PVA implant (n = 4) or to have an empty defect (n = 2) and were monitored for 6 months. Patellofemoral radiographs were obtained at monthly intervals, and quantitative computed tomography was performed at the end of the study. After death, the joints were macroscopically evaluated and scored. Osteochondral and synovial membrane histological findings were assessed using modified Osteoarthritis Research Society International (OARSI) and aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL) scoring systems. Immunohistochemistry using Iba1 was performed to evaluate activated macrophage infiltration. Results: Overall, 2 sheep with PVA implants were euthanized at 1 and 5 months because of uncontrollable pain and lameness (failed implants). Quantitative computed tomography showed that sheep with failed implants had 2.1-fold more osteolysis than those with successful implants. The sheep with failed implants had osteoarthritis with extensive glycosaminoglycan loss and cartilage fibrillation of the condyle and opposing tibial surface on histological examination. A foreign body reaction with severe chronic lymphoplasmacytic and granulomatous inflammation with giant cells was detected surrounding the implant. The synovial membrane ALVAL score was 9 of 19 and 14 of 19 in failed implants with synovial hyperplasia and lymphoplasmacytic and macrophage infiltration. In contrast, the synovial membrane in successful implants and empty defects was normal (ALVAL score = 0/19). Immunolabeling for Iba1 in failed implants confirmed extensive and dense macrophage infiltration within the condyle and synovial membrane, with the highest immunoreactive score (9/9). Conclusion: PVA hydrogel implants had a 50% failure rate with uncontrollable pain, severe osteolysis, inflammation, and foreign body reactions. Clinical Relevance: The failure rate and pathological characteristics of the PVA implants suggest that their use should not be continued in human patients without further in vivo safety studies.

Synthetic PVA Osteochondral Implants for the Knee Joint: Mechanical Characteristics During Simulated Gait

Background: Although polyvinyl alcohol (PVA) implants have been developed and used for the treatment of femoral osteochondral defects, their effect on joint contact mechanics during gait has not been assessed. Purpose/Hypothesis: The purpose was to quantify the contact mechanics during simulated gait of focal osteochondral femoral defects and synthetic PVA implants (10% and 20% by volume of PVA), with and without porous titanium (pTi) bases. It was hypothesized that PVA implants with a higher polymer content (and thus a higher modulus) combined with a pTi base would significantly improve defect-related knee joint contact mechanics. Study Design: Controlled laboratory study. Methods: Four cylindrical implants were manufactured: 10% PVA, 20% PVA, and 10% and 20% PVA disks mounted on a pTi base. Devices were implanted into 8 mm–diameter osteochondral defects created on the medial femoral condyles of 7 human cadaveric knees. Knees underwent simulated gait and contact stresses across the tibial plateau were recorded. Contact area, peak contact stress, the sum of stress in 3 regions of interest across the tibial plateau, and the distribution of stresses, as quantified by tracking the weighted center of contact stress throughout gait, were computed for all conditions. Results: An osteochondral defect caused a redistribution of contact stress across the plateau during simulated gait. Solid PVA implants did not improve contact mechanics, while the addition of a porous metal base led to significantly improved joint contact mechanics. Implants consisting of a 20% PVA disk mounted on a pTi base significantly improved the majority of contact mechanics parameters relative to the empty defect condition. Conclusion: The information obtained using our cadaveric test system demonstrated the mechanical consequences of femoral focal osteochondral defects and provides biomechanical support to further pursue the efficacy of high-polymer-content PVA disks attached to a pTi base to improve contact mechanics. Clinical Relevance: As a range of solutions are explored for the treatment of osteochondral defects, our preclinical cadaveric testing model provides unique biomechanical evidence for the continued investigation of novel solutions for osteochondral defects.

Ceramic composite with gentamicin decreases persistent infection and increases bone formation in a rat model of debrided osteomyelitis.

Introduction: Current methods of managing osteomyelitic voids after debridement are inadequate and result in significant morbidity to patients. Synthetic ceramic void fillers are appropriate for non-infected bone defects but serve as a nidus of re-infection in osteomyelitis after debridement. CERAMENT G (CG) is an injectable ceramic bone void filler which contains gentamicin and is currently being evaluated for use in osteomyelitic environments after debridement due to its theoretical ability to serve as a scaffold for healing while eliminating residual bacteria after debridement through the elution of antibiotics. The goal of this study was to evaluate (1) the rate of persistent infection and (2) new bone growth of a debrided osteomyelitic defect in a rat model which has been treated with either gentamicin-impregnated ceramic cement (CERAMENT G) or the same void filler without antibiotics (CERAMENT, CBVF). Methods: Osteomyelitis was generated in the proximal tibia of Sprague Dawley rats, subsequently debrided, and the defect filled with either (1) CG (), (2) CBVF (), or (3) nothing (). Each group was euthanized after 6 weeks. Infection was detected through bacterial culture and histology. Bone growth was quantified using microCT. Results: Infection was not detected in defects treated with CG as compared with 35 % of defects () treated with CBVF and 50 % () of empty defects (). Bone volume in the defect of CG-treated rats was greater than the CBVF (0.21 vs. 0.17, ) and empty groups (0.21 vs. 0.11, ) at 6 weeks after implantation. Conclusions: Ceramic void filler with gentamicin (CERAMENT G) decreased the rate of persistent infection and increased new bone growth as compared to the same void filler without antibiotics (CERAMENT) and an empty defect in a rat model of debrided osteomyelitis.

Performance of Calcium Phosphate Cements in the Augmentation of Sheep Vertebrae-An Ex Vivo Study.

Oil-based calcium phosphate cement (Paste-CPC) shows not only prolonged shelf life and injection times, but also improved cohesion and reproducibility during application, while retaining the advantages of fast setting, mechanical strength, and biocompatibility. In addition, poly(L-lactide-co-glycolide) (PLGA) fiber reinforcement may decrease the risk for local extrusion. Bone defects (diameter 5 mm; depth 15 mm) generated ex vivo in lumbar (L) spines of female Merino sheep (2–4 years) were augmented using: (i) water-based CPC with 10% PLGA fiber reinforcement (L3); (ii) Paste-CPC (L4); or (iii) clinically established polymethylmethacrylate (PMMA) bone cement (L5). Untouched (L1) and empty vertebrae (L2) served as controls. Cement performance was analyzed using micro-computed tomography, histology, and biomechanical testing. Extrusion was comparable for Paste-CPC(-PLGA) and PMMA, but significantly lower for CPC + PLGA. Compressive strength and Young’s modulus were similar for Paste-CPC and PMMA, but significantly higher compared to those for empty defects and/or CPC + PLGA. Expectedly, all experimental groups showed significantly or numerically lower compressive strength and Young’s modulus than those of untouched controls. Ready-to-use Paste-CPC demonstrates a performance similar to that of PMMA, but improved biomechanics compared to those of water-based CPC + PLGA, expanding the therapeutic arsenal for bone defects. O, significantly lower extrusion of CPC + PLGA fibers into adjacent lumbar spongiosa may help to reduce the risk of local extrusion in spinal surgery.

Reconstruction of Two-dimensional Image to Three-dimensional Point Cloud Data for Detection of Empty Rot Defects in Tree Growth

In the application of nondestructive detecting of trees, it is a technical problem to use radar waves to detect tree specimens with growth defects, how to segment defect areas after obtaining two-dimensional images, and reverse simulate the detection results with three-dimensional point cloud data. Therefore, the method of extracting boundary information according to color features is studied to extract the boundary curve of empty rot area, and the selection of higher precision extraction algorithm is determined by comparing the boundary extraction results of HSV color space and RGB color space in laboratory According to the extracted void boundary curve, the reverse modeling is carried out, and the mapping from 2D inspection gray image to 3D space is realized, The point cloud data reconstruction needed for 3D modeling of multi-curved surfaces is obtained in reverse. The boundary curve extraction algorithm in this study is used to process the images of nondestructive testing of trees. Through comparative experiments and error analysis, the accurate modeling conclusion from inversion of 2D images to 3D point cloud data reconstruction by radar wave detection is verified, and the Core issue problem of point cloud reconstruction in the ill-conditioned area of tree growth and decay detected by radar wave is solved.

Preclinical Testing of New Hydrogel Materials for Cartilage Repair: Overcoming Fixation Issues in a Large Animal Model.

Reinforced hydrogels represent a promising strategy for tissue engineering of articular cartilage. They can recreate mechanical and biological characteristics of native articular cartilage and promote cartilage regeneration in combination with mesenchymal stromal cells. One of the limitations of in vivo models for testing the outcome of tissue engineering approaches is implant fixation. The high mechanical stress within the knee joint, as well as the concave and convex cartilage surfaces, makes fixation of reinforced hydrogel challenging. Methods. Different fixation methods for full-thickness chondral defects in minipigs such as fibrin glue, BioGlue®, covering, and direct suturing of nonenforced and enforced constructs were compared. Because of insufficient fixation in chondral defects, superficial osteochondral defects in the femoral trochlea, as well as the femoral condyle, were examined using press-fit fixation. Two different hydrogels (starPEG and PAGE) were compared by 3D-micro-CT (μCT) analysis as well as histological analysis. Results. Our results showed fixation of below 50% for all methods in chondral defects. A superficial osteochondral defect of 1 mm depth was necessary for long-term fixation of a polycaprolactone (PCL)-reinforced hydrogel construct. Press-fit fixation seems to be adapted for a reliable fixation of 95% without confounding effects of glue or suture material. Despite the good integration of our constructs, especially in the starPEG group, visible bone lysis was detected in micro-CT analysis. There was no significant difference between the two hydrogels (starPEG and PAGE) and empty control defects regarding regeneration tissue and cell integration. However, in the starPEG group, more cell-containing hydrogel fragments were found within the defect area. Conclusion. Press-fit fixation in a superficial osteochondral defect in the medial trochlear groove of adult minipigs is a promising fixation method for reinforced hydrogels. To avoid bone lysis, future approaches should focus on multilayered constructs recreating the zonal cartilage as well as the calcified cartilage and the subchondral bone plate.

Early failure of a polyvinyl alcohol hydrogel implant with foreign body reaction and osteolysis in an ovine model of cartilage repair

Purpose: Hemiarthroplasty with polyvinyl alcohol hydrogel (PVA) cartilage implants in the treatment of hallux rigidus showed initial promise with a 90% success rate. However, recent studies suggest that the implant may shrink and subside, leading to higher than anticipated failure rates. The purpose of this study was to characterize the healing response to polyvinyl implantation by using an ovine model. Methods: An osteochondral defect was created unilaterally in the medial femoral condyle of six sheep and filled with a PVA implant (Cartiva, Wright Medical) (n=4) or left empty (n=2). Sheep were followed for six months. Post-mortem quantitative CT (qCT) evaluations were performed to measure bone density using 5mm-wide ROI delineated in 3D reconstruction around the defect/implant area. Joints were then dissected and evaluated using a modified International Cartilage Repair Society (ICRS) macroscopic score (I=best, IV=worst). Osteochondral sections were assessed using a modified Osteoarthritis Research Society International (OARSI) histopathology net score (0=best, 20=worst). Synovial membrane histology was scored using the aseptic lymphocyte-dominated vasculitis-associated lesions (ALVAL) scoring system for soft tissue reaction (0=best, 19=worst). Both the synovial membrane and osteochondral sections underwent immunohistochemistry with anti-ionized calcium-binding adapter molecule 1 antibody (Iba1) to identify macrophages. Results: Two of four sheep with the PVA implant showed unrelenting pain and lameness necessitating early euthanasia. These were considered failed implants. qCT scans revealed 2-fold more osteolysis around failed implants than the other two (successful) implants or empty defects (Figure 1A). Grossly, failed implant sheep had ICRS scores of III and IV/V. The two successful implant sheep had ICRS scores of II/V and both empty defect sheep had scores of III/V. Osteochondral histology of failed implants had a mean OARSI score of 13/20 with extensive GAG loss and a stromal inflammatory reaction surrounding the implant that was up to 5-fold wider than successful implants (Figure 1B). This reaction contained abundant fibrovascular tissue with aggregates of lymphocytes and plasma cells. Failed implants revealed strong and diffuse Iba1 staining of macrophages along the implant/bone interface with cells densely packed in multiple rows (Figure 1C). Multinucleated giant cells and macrophages were identified surrounding presumptive implant debris in one failed implant (Figure 1C, red arrow and X). Successful implants and empty defects had few Iba1 positive cells randomly distributed (Figure 1C). Mean synovial membrane ALVAL score for failed implants was 11/19 with presence of an adverse local tissue reaction with lymphocytes and macrophages, vascular reactivity, and synovial hyperplasia (Figure 1D, E). In contrast, synovial membrane in successful implants and empty defects were normal (ALVAL 0/19). Conclusions: Polyvinyl alcohol hydrogel implants had a 50% early failure rate with uncontrollable pain, severe osteolysis, inflammation and an adverse local tissue reaction. Furthermore, the recruitment of macrophages and multinucleated giant cells are evidence of a foreign body reaction typically associated with implant wear debris. Non-degradable biomaterials such as PVA will result in continuous infiltration by macrophages and secretion of proinflammatory cytokines, leading to periprosthetic osteolysis and ultimately implant failure. These Results suggest that the use of this PVA implant should not be continued in human patients without further in vivo safety studies.

Scaffold-Dependent Mechanical and Architectural Cues Guide Osteochondral Defect Healing in silico.

Osteochondral defects in joints require surgical intervention to relieve pain and restore function. However, no current treatment enables a complete reconstitution of the articular surface. It is known that both mechanical and biological factors play a key role on osteochondral defect healing, however the underlying principles and how they can be used in the design of treatment strategies remain largely unknown. To unravel the underlying principles of mechanobiology in osteochondral defect healing, i.e., how mechanical stimuli can guide biological tissue formation, we employed a computational approach investigating the scaffold-associated mechanical and architectural properties that would enable a guided defect healing. A previous computer model of the knee joint was further developed to simulate healing of an empty osteochondral defect. Then, scaffolds were implanted in the defect and their architectures and material properties were systematically varied to identify their relevance in osteochondral defect healing. Scaffold mechanical and architectural properties were capable of influencing osteochondral defect healing. Specifically, scaffold material elastic modulus values in the range of cancellous bone (low GPa range) and a scaffold architecture that provided stability, i.e., resistance against displacement, in both the main loading direction and perpendicular to it supported the repair process. The here presented model, despite its simplifications, is regarded as a powerful tool to screen for promising properties of novel scaffold candidates fostering osteochondral defect regeneration prior to their implementation in vivo.

A Novel Strategy to Enhance Microfracture Treatment With Stromal Cell-Derived Factor-1 in a Rat Model.

BackgroundMicrofracture is one of the most widely used techniques for the repair of articular cartilage. However, microfracture often results in filling of the chondral defect with fibrocartilage, which exhibits poor durability and sub-optimal mechanical properties. Stromal cell-derived factor-1 (SDF-1) is a potent chemoattractant for mesenchymal stem cells (MSCs) and is expressed at high levels in bone marrow adjacent to developing cartilage during endochondral bone formation. Integrating SDF-1 into an implantable collagen scaffold may provide a chondro-conductive and chondro-inductive milieu via chemotaxis of MSCs and promotion of chondrogenic differentiation, facilitating more robust hyaline cartilage formation following microfracture.ObjectiveThis work aimed to confirm the chemoattractive properties of SDF-1 in vitro and develop a one-step method for incorporating SDF-1 in vivo to enhance cartilage repair using a rat osteochondral defect model.MethodsBone marrow-derived MSCs (BMSCs) were harvested from the femurs of Sprague–Dawley rats and cultured in low-glucose Dulbecco’s modified Eagle’s medium containing 10% fetal bovine serum, with the medium changed every 3 days. Passage 1 MSCs were analyzed by flow cytometry with an S3 Cell Sorter (Bio-Rad). In vitro cell migration assays were performed on MSCs by labeling cells with carboxyfluorescein diacetate, succinimidyl ester (CFDA-SE; Bio-Rad). For the microfracture model, a 1.6-mm-diameter osteochondral defect was created in the femoral trochleae of 20 Sprague–Dawley rats bilaterally until bone marrow spillage was seen under saline irrigation. One knee was chosen at random to receive implantation of the scaffold, and the contralateral knee was left unfilled as an empty control. Type I collagen scaffolds (Kensey Nash) were coated with either gelatin only or gelatin and SDF-1 using a dip coating process. The rats received implantation of either a gelatin-only scaffold (N = 10) or gelatin-and-SDF-1 scaffold (N = 10) at the site of the microfracture. Femurs were collected for histological analyses at 4- and 8-week time points post-operatively, and sections were stained with Safranin O/Fast Green. The samples were graded blindly by two observers using the Modified O’Driscoll score, a validated scoring system for chondral repair. A minimum of 10 separate grading scores were made per sample and averaged. Quantitative comparisons of cell migration in vitro were performed with one-way ANOVA. Cartilage repair in vivo was also compared among groups with one-way ANOVA, and the results were presented as mean ± standard deviation, with P-values < 0.05 considered as statistically significant.ResultsMSC migration showed a dose–response relationship with SDF-1, with an optimal dosage for chemotaxis between 10 and 100 ng/ml. After scaffold implantation, the SDF-1-treated group demonstrated complete filling of the cartilage defect with mature cartilage tissue, exhibiting strong proteoglycan content, smooth borders, and good incorporation into marginal cartilage. Modified O’Driscoll scores after 8 weeks showed a significant improvement of cartilage repair in the SDF-1 group relative to the empty control group (P < 0.01), with a trend toward improvement when compared with the gelatin-only-scaffold group (P < 0.1). No significant differences in scores were found between the empty defect group and gelatin-only group.ConclusionIn this study, we demonstrated a simple method for improving the quality of cartilage defect repair in a rat model of microfracture. We confirmed the chemotactic properties of SDF-1 on rat MSCs and found an optimized dosage range for chemotaxis between 10 and 100 ng/ml. Furthermore, we demonstrated a strategy to incorporate SDF-1 into gelatin–collagen I scaffolds in vivo at the site of an osteochondral defect. SDF-1-treated defects displayed robust hyaline cartilage resurfacing of the defect with minimal fibrous tissue, in contrast to the empty control group. The results of the in vitro and in vivo studies together suggest that SDF-1-mediated signaling may significantly improve the quality of cartilage regeneration in an osteochondral defect.

Biological behavior of magnesium-substituted hydroxyapatite during bone repair.

The aim of this study was to analyze the biological behavior and osteogenic potential of magnesium (Mg) substituted hydroxyapatite (HA) microspheres, implanted in a critical bone defect, considering that this ion is of great clinical interest, since it is closely associated with homeostasis and bone mineralization. For the purpose of this study, 30 rats were used to compose three experimental groups: GI - bone defect filled with HA microspheres; GII - bone defect filled with HA microspheres replaced with Mg; GIII - empty bone defect; evaluated at biological points of 15 and 45 days. The histological results, at 15 days, showed, in all the groups, a discrete chronic inflammatory infiltrate; biomaterials intact and surrounded by connective tissue; and bone neoformation restricted to the borders. At 45 days, in the GI and GII groups, an inflammatory response of discrete granulomatous chronic type was observed, and in the GIII there was a scarce presence of mononuclear inflammatory cells; in GI and GII, the microspheres were seen to be either intact or fragmented, surrounded by fibrous connective tissue rich in blood vessels; and discrete bone neoformation near the edges and surrounding some microspheres. In GIII, the mineralization was limited to the borders and the remaining area was filled by fibrous connective tissue. It was concluded that the biomaterials were biocompatible and osteoconductive, and the percentage of Mg used as replacement ion in the HA did not favor a greater bone neoformation in relation to the HA without the metal.

Combination of a Collagen Scaffold and an Adhesive Hyaluronan-Based Hydrogel for Cartilage Regeneration: A Proof of Concept in an Ovine Model

ObjectiveHyaluronic acid–transglutaminase (HA-TG) is an enzymatically crosslinkable adhesive hydrogel with chondrogenic properties demonstrated in vitro and in an ectopic mouse model. In this study, we investigated the feasibility of using HA-TG in a collagen scaffold to treat chondral lesions in an ovine model, to evaluate cartilage regeneration in a mechanically and biologically challenging joint environment, and the influence of the surgical procedure on the repair process.DesignChondral defects of 6-mm diameter were created in the stifle joint of skeletally mature sheep. In a 3-month study, 6 defects were treated with HA-TG in a collagen scaffold to test the stability and biocompatibility of the defect filling. In a 6-month study, 6 sheep had 12 defects treated with HA-TG and collagen and 2 sheep had 4 untreated defects. Histologically observed quality of repair tissue and adjacent cartilage was semiquantitatively assessed.ResultsHA-TG adhered to the native tissue and did not cause any detectable negative reaction in the surrounding tissue. HA-TG in a collagen scaffold supported infiltration and chondrogenic differentiation of mesenchymal cells, which migrated from the subchondral bone through the calcified cartilage layer. Additionally, HA-TG and collagen treatment led to better adjacent cartilage preservation compared with empty defects (P < 0.05).ConclusionsThis study demonstrates that the adhesive HA-TG hydrogel in a collagen scaffold shows good biocompatibility, supports in situ cartilage regeneration and preserves the surrounding cartilage. This proof-of-concept study shows the potential of this approach, which should be further considered in the treatment of cartilage lesions using a single-step procedure.

Mechanical and structural peculiarities of tibia shaft nonunion and its influence for treatment

Objective. To study internal tensions in bone and soft tissues of shin at normal condition and at isolated tibia nonunion, the range of fragments displacement, callous structure and to sustain the conception of treatment. Methods. Due to finite element method we created three models: I — anatomic norm; II — transverse defect of 5 mm height on the middle-lower 1/3 border filled with collagen, III — as the second model with empty fibula defect of 10 mm height on the same level 2/3–1/3 border. In 45 patients with tibia shaft nonunion (term 4–18 months) we made resection of fibula fragment 10–15 mm on the same level of tibia nonunion with apparatus of external fixation. We studied the linear bone fragments displacement and callous structure. Results. At the axial loading in normal condition (I model) there was asymmetry of tensions in the lower part of shin bones on the lateral and medial sides. At the II model vertical tensions in the lower part of tibia decreased on the medial side up to 69 % and on the lateral side — up to 44 %, tensions increased in 5 times on the lateral side of fibula. The tangential stresses increased 3 times, their resulting force vector changed the outward direction and increased 7 times. In the III model tension distribution on the tibia surface became close to normal situation. In case of tibia nonunion there was fibrous-cartilages tissues, appeared because of transverse tensions. Patients walked with weight bearing from the first days after surgery, in 95.6 % bone fragments consolidation happened in 3.5–4 months. Conclusion. Excluding of fibula from bearing function due to its 10–15 mm resection on the level of nonunion will normalize the vector of loading in the tibia fragments and fibrous-cartilage regenerate and leads to it ossification.

Evaluation of single-dose applied teriparatide effect on bone healing with histomorphometric and micro-ct analysis

The aim of the present study was to evaluate the effects of a single dose of locally administered teriparatide (TP) on healing critical-sized defects in rat mandibles through histomorphometric and microcomputed tomography (micro-CT) analyses.In this study, 48 Sprague–Dawley rats were used. The experimental animals were divided into 4 groups as follows: Group 1 had empty defects, Group 2 received autografts, Group 3 received allografts, and Group 4 received allografts combined with 40 μg of TP. Eight weeks after the surgical procedure, all rats were sacrificed, and all specimens were evaluated using micro-CT and histomorphometric analyses.The results of the histomorphometric analysis showed that Group 4 had the most new bone area (0.85 mm2 ± 0.13 mm2) (p = 0.002) and the highest number of osteoblasts (86.61 ± 4.86) (p = 0.001). In addition, the results of the micro-CT analysis showed that Group 4 had the highest bone volume/total volume (23.27% ± 0.15%) (p = 0.001). The histomorphometric and micro-CT values of Group 2 were higher than those of Group 1 but lower than those of Group 3 and Group 4.The results of the study show that a single dose of locally administered TP has a positive effect on the integration of allografts. However, further studies are necessary to identify the mechanism of action and the effective minimum and maximum doses of locally administered TP.

Systematic Postoperative Assessment of a Minimally-Invasive Sheep Model for the Treatment of Osteochondral Defects

To assess the clinical course of a sheep stifle joint model for osteochondral (OC) defects, medial femoral condyles (MFC) were exposed without patella luxation using medial parapatellar skin (3–4 cm) and deep incisions (2–3 cm). Two defects (7 mm diameter; 10 mm depth; OC punch) were left empty or refilled with osteochondral autologous transplantation cylinders (OATS) and explanted after six weeks. Incision-to-suture time, anesthesia time, and postoperative wound or impairment scores were compared to those in sham-operated animals. Implant performance was assessed by X-ray, micro-computed tomography, histology, and immunohistology (collagens 1, 2; aggrecan). There were no surgery-related infections or patellar luxations. Operation, anesthesia, and time to complete stand were short (0.5, 1.4, and 1.5 h, respectively). The wound trauma score was low (0.4 of maximally 4; day 7). Empty-defect and OATS animals reached an impairment score of 0 significantly later than sham animals (7.4 and 4.0 days, respectively, versus 1.5 days). Empty defects showed incomplete healing and dedifferentiation/heterotopic differentiation; OATS-filled defects displayed advanced bone healing with remaining cartilage gaps and orthotopic expression of bone and cartilage markers. Minimally-invasive, medial parapatellar surgery of OC defects on the sheep MFC allows rapid and low-trauma recovery and appears well-suited for implant testing.

Chondrocyte-to-osteoblast transformation in mandibular fracture repair.

The majority of fracture research has been conducted using long bone fracture models, with significantly less research into the mechanisms driving craniofacial repair. However, craniofacial bones differ from long bones in both their developmental mechanism and embryonic origin. Thus, it is possible that their healing mechanisms could differ. In this study we utilize stabilized and unstabilized mandible fracture models to investigate the pathways regulating repair. Whereas fully stable trephine defects in the ramus form bone directly, mechanical motion within a transverse fracture across the same anatomical location promoted robust cartilage formation before boney remodeling. Literature investigating long bone fractures show chondrocytes are a direct precursor of osteoblasts during endochondral repair. Lineage tracing with Aggrecan‐CreERT2::Ai9 tdTomato mice demonstrated that mandibular callus chondrocytes also directly contribute to the formation of new bone. Furthermore, immunohistochemistry revealed that chondrocytes located at the chondro‐osseous junction expressed Sox2, suggesting that plasticity of these chondrocytes may facilitate this chondrocyte‐to‐osteoblast transformation. Based on the direct role chondrocytes play in bone repair, we tested the efficacy of cartilage grafts in healing critical‐sized mandibular defects. Whereas empty defects remained unbridged and filled with fibrous tissue, cartilage engraftment produced bony‐bridging and robust marrow cavity formation, indicating healthy vascularization of the newly formed bone. Engrafted cartilage directly contributed to new bone formation since a significant portion of the newly formed bone was graft/donor‐derived. Taken together these data demonstrate the important role of chondrocyte‐to‐osteoblast transformation during mandibular endochondral repair and the therapeutic promise of using cartilage as a tissue graft to heal craniofacial defects.

Autogenous bone particles combined with platelet-rich plasma can stimulate bone regeneration in rabbits.

Long-term bone defects are a key clinical problem. Autogenous bone graft remains the gold standard for the treatment of these defects; however, improving the osteogenic properties and reducing the amount of autogenous bone is challenging. Autologous platelet-rich plasma (PRP) has been widely considered for treatment, due to its potentially beneficial effect on bone regeneration and vascularization. The aim of the present study was to explore the effects of autogenous bone particles combined with PRP on repairing segmental bone defects in rabbits. Briefly, a critical-size diaphyseal radius defect was established in 45 New Zealand White rabbits. Animals were randomly divided into four groups, according to the different implants: Group A, empty bone defect; group B, PRP; group C, autogenous bone particles + bone mesenchymal stem cells (BMSCs) on the left radius; group D, autogenous bone particles + PRP + BMSCs on the right radius. Bone samples were collected and further analyzed using X-ray, histology and histomorphometry 4, 8 and 12 weeks post-surgery. In addition, the effect of PRP on cell proliferation was detected by Cell Counting Kit-8 and the concentrations of growth factors (GFs), transforming GF (TGF)-β1 and platelet-derived GF (PDGF), in PRP were verified by ELISA. X-ray, histology and histomorphometry data revealed that the fraction area of the newly formed bone was larger in group D. In addition, PRP could improve cell proliferation, osteogenic differentiation and the release of GFs, TGF-β1 and PDGF-AB. In conclusion, these findings indicated that an autogenous bone particle + PRP + BMSC scaffold may be used as a potential treatment strategy for segmental defects in humans.

Combinatorial fluorapatite-based scaffolds substituted with strontium, magnesium and silicon ions for mending bone defects

In bone tissue engineering, ionic doping using bone-related minerals such as magnesium (Mg) or strontium (Sr) is a promising strategy to make up for the inherent disadvantages (low solubility) of various apatite-based materials (such as fluorapatite (FAp) and hydroxyapatite (HA)). Therefore, some studies in recent years have tried to address the lack-of-methodology to improve the properties of bioceramics in the field. Even though the outcome of the studies has shown some promises, the influence of doped elements on the structures and properties of in-vitro and in-vivo mineralized FAp has not been investigated in detail so far. Thus, it is still an open question mark in the field. In this work, strontium modified fluorapatite (Sr-FAp), magnesium and silicon modified fluorapatite (Mg-SiFAp) bioceramics were synthesized using a mechanical alloying methodology. Results showed that the doped elements could decrease the crystallinity of FAp (56%) to less than 45% and 39% for Sr-FAp and Mg-SiFAp, respectively. Moreover, in-vitro studies revealed that Sr-FAp significantly enhanced osteogenic differentiation of hMSCs, after 21 days of culture, compared to Mg-SiFAp at both osteogenic and normal media. Then, in vivo bone formation in a defect of rat femur filled with a Sr-FAp and Mg-SiFAp compared to empty defect was investigated. Histological analysis revealed an increase in bone formation three weeks after implanting Sr-FAp compared to Mg-SiFAp and the empty defect. These results suggest that compared to magnesium and silicon, strontium ion significantly promotes bone formation in fluorapatite, making it appropriate for filling bone defects.