Demineralized Bone Matrix Fibers plus Allograft Bone for Multilevel Posterolateral Spine Fusion: A Game Changer?

Introduction: While autograft bone is the gold standard for multilevel posterolateral lumbar fusion, bone substitutes and graft extenders such as allograft bone, ceramics and demineralized bone matrix (DBM) have been used to avoid the morbidity and insufficient quantity associated with harvesting autologous bone. The primary objective of this retrospective study was to determine whether, in patients with increased risk of operative nonunion related to multilevel fusion, adding DBM fibers to mineralized bone allograft resulted in better fusion than using allograft alone. The secondary objectives were to evaluate how adding DBM fibers affects functional disability, low back pain, intraoperative blood loss and the nonunion rate. Methods: This retrospective study involved a chart review of consecutive patients who underwent multilevel lumbar spinal fusion and were operated on by a single surgeon. The patients were divided into two groups: 14 patients received mineralized bone allograft (control group) and 14 patients received a combination of mineralized bone allograft and DBM (experimental group). Patients were reviewed at a mean of 16.4 ± 2.2 months after surgery at which point CT scans were analyzed to determine whether fusion had occurred;Oswestry disability index (ODI) and pain were also evaluated. Results: A mean of 5 levels [min 2, max 13] were fused in these patients. Posterolateral fusion as defined by the Lenke classification was not significantly different between groups. The experimental DBM group had a significantly better composite fusion score than the control group (P Discussion: Adding DBM fibers to allograft bone during multilevel posterolateral spinal fusion was safe and produced better composite fusion than using allograft only as an autograft extender.

Efficacy of bone grafts in jaw cystic lesions:A systematic review

BACKGROUND Bone grafts have been applied for many years in orthopedic surgery to assist with bone repair for defects or bone discontinuity caused by trauma and tumors as well as periodontal defects.Jaw cysts are another common benign disease of the maxillofacial region which may lead to pathological bone fracture,loss of teeth,and infection.However,whether bone grafts are beneficial for bone regeneration in jaw cystic lesions and when bone grafts should be used remains unclear.AIM To study the efficacy of bone grafts compared to spontaneous healing in the treatment of jaw cystic lesions.METHODS A literature search was performed in Medline,Cochrane Library and Embase to identify related articles published in English in the last ten years.The following key words and Me SH terms were used:“jaw cyst”,“cystic lesion”,“odontogenic cyst”,“periapical cyst”,“dentigerous cyst”,“follicular cyst”,“keratocyst”,“treatment”,“surgery”,“bone graft”,“enucleation”,“cystectomy”,and“bone regeneration”.Case reports,clinical trials,clinical studies,observational studies and randomized controlled trials were included.Study quality was evaluated.RESULTS Ten studies(n=10)met the inclusion criteria.Five studies reported spontaneous bone healing after enucleation,three studies investigated the efficacy of various bone grafts,and two randomized comparative studies focused on the comparison between spontaneous healing and bone grafting.Over 90%of bone regeneration occurred within 6 mo after bone grafting.The bone regeneration rate after cystectomy showed great variation,ranging from 50%to 100%after 6 mo,but reaching over 90%after 12 mo.CONCLUSION While the long-term superiority of bone grafting compared with spontaneous healing after cystectomy is unclear,bone grafts accelerate the process of healing and significantly increase bone quality.

Evaluation of 4 different bone graft substitutes and autogenous bone grafting in root-end resection osteotomies after retrograde root-filling with Intermediate Restorative Material(IRM):An experimental study in dogs

Purpose: To investigate the periapical tissue response after root end filling with intermediate restorative material (IRM) and filling of the root-end resection bone defects with autogenous bone or a bone graft substitute in comparison to empty controls. Materials and Methods: Vital roots of the second, third and fourth mandibular premolars in six healthy mongrel dogs were apectomized. The root canals were prepared and sealed with IRM following a standardized surgical procedure. The resection bone defects were either filled with autogenous bone (PB) or one of the bone graft substitutes;CERAMENTTM|BONE VOID FILLER, ChronOS?, TigranTM PTG, Easygraft? CLASSIC or left empty. After 120 days the animals were sacrificed and the specimens were analyzed radiologically and histologically. Kruskal-Wallis and Mann-Whitney tests were performed for statistical evaluation. Results: 34 sections were analyzed histologically. The evaluation revealed a variation in the outcome amongst the tested options, regarding reestablishment of the periapical bone healing and inflammatory infiltration in the sections. According to the tested variables, there was no statistical significant difference between the materials when comparing all groups as a whole. When comparing individual materials to each other there was statistical differences among some of the tested materials. Conclusion: The healing outcome after periapical surgery of a five-wall resection defect could not be increased by infill with autogenous bone or bone graft substitutes. The most important factor for the healing outcome in periapical surgery is the quality of the root-end sealing. The healing outcome after some of the tested bone substitutes, might be improved by longer healing time.

Co-delivery of rhBMP-2 and zoledronic acid using calcium sulfate/hydroxyapatite carrier as a bioactive bone substitute to enhance and accelerate spinal fusion

Recombinant human bone morphogenetic protein-2(rhBMP-2)has been FDA-approved for lumbar fusion,but supraphysiologic initial burst release due to suboptimal carrier and late excess bone resorption caused by osteoclast activation have limited its clinical usage.One strategy to mitigate the pro-osteoclast side effect of rhBMP-2 is to give systemic bisphosphonates,but it presents challenges with systemic side effects and low local bioavailability.The aim of this in vivo study was to analyze if posterolateral spinal fusion(PLF)could be improved by utilizing a calcium sulfate/hydroxyapatite(CaS/HA)carrier co-delivering rhBMP-2 and zoledronic acid(ZA).Six groups were allocated(CaS/HA,CaS/HA+BMP-2,CaS/HA+systemic ZA,CaS/HA+local ZA,CaS/HA+BMP-2+systemic ZA,and CaS/HA+BMP-2+local ZA).10-week-old male Wistar rats,were randomly assigned to undergo L4-L5 PLF with implantation of group-dependent scaffolds.At 3 and 6 weeks,the animals were euthanized for radiography,μCT,histological staining,or biomechanical testing to evaluate spinal fusion.The results demonstrated that the CaS/HA biomaterial alone or in combination with local or systemic ZA didn’t support PLF.However,the delivery of rhBMP-2 significantly promoted PLF.Combining systemic ZA with rhBMP-2 didn’t enhance spinal fusion.Notably,the co-delivery of rhBMP-2 and ZA using the CaS/HA carrier significantly enhanced and accelerated PLF,without inhibiting systemic bone turnover,and potentially reduced the dose of rhBMP-2.Together,the treatment regimen of CaS/HA biomaterial co-delivering rhBMP-2 and ZA could potentially be a safe and cost-effective off-the-shelf bioactive bone substitute to enhance spinal fusion.

Decoding bone-inspired and cell-instructive cues of scaffolds for bone tissue engineering

Bone fractures are common occurrence in clinical settings,creating a high demand for effective repair material.Unfortunately,limited graft availability,donor site morbidities,unpredictable clinical outcomes,immunologic reactions,infection risks,and geometrical mismatching concerns hampered tissue graft use and underscored the need for scaffolds for more effective bone reconstructions due to their tunable properties.Significant progress has been carried out in past decade in the fields of nanoceramics synthesis,bioconjugate chemistry,and composite material processing.This review outlines hierarchical structures and biology of bone tissue,materialistic compo-nents of scaffolds(bioceramics,polymers,bioactive drugs),featured scaffolding strategies(nanofibers,hydrogels,aerogels,bioprinting,and fiber-reinforced composite),and emphasis that hierarchical and physiochemical char-acteristics of bone should be used as an inspiration for scaffold design.This review discussed how differences in materiobiological aspects of scaffolds,such as polymer/bioceramic nanocomposite,mineralized nanocomposite,matrix-rich nanocomposite,3D microenvironmental cues,pore space cues,mechanical cues,usage of physical stimulation(magnetic,electroactive,and photoactivated cues),surface cues(wettability,roughness,textured,and surface charge),and biointerface cues(cell-biomaterial interactions,cell-selective homing,and cell regula-tory strategies)modulate cellular and biological response for bone tissue engineering.This study further outlines the challenges and benefits of integrating materiobiological cues of scaffolds for bone tissue engineering.

Porous titanium granules in critical size defects of rabbit tibia with or without membranes

Recently, porous titanium granules （PTGs） have been indicated for the preservation of the dimensions of post-extraction sockets, as a filler in sinus lift procedures and for the treatment of peri-implant and periodontal defects, based on the osteoconductivity and dimensional stability of the titanium granules. However, there is a lack of information regarding the use of this material in larger defects and in conjunction with membranes. The objective of this study is to test the behavior of PTGs used to fill critical size defects in rabbit tibiae, with and without membranes. Critical defects were created in both tibiae of rabbits, divided randomly into three groups： Group A （defect filled with PTG）, Group B （defect filled with PTG＋collagen membrane） and a control group （empty defect）. After six weeks, histomorphometric analysis was performed. The results showed more defect closures at the cortical area （87.37%±2.2%） and more bone formation at the marrow area （57.6%± 1.3%） in Group B, in comparison with the other groups （P〈0.05）; the use of membranes improved the material stability expressed as more percentages of the original material when membranes were used （P〈0.05）. Finally, inflammatory reactions were observed when the granules were not protected by membranes. In spite of the limitations of this animal study, it may be concluded that PTG particles are osteoconductive and allow bone growth. The PTG particles must be covered by a membrane, especially when grafting larger defects, in order to control particle migration, promote clot stabilization and separate the PTG graft from undesired soft tissue cells.

Preparation of Hydroxyapatite Cement and Analysis as of its Disposition

Objective: To prepare hydroxyapatite cement (or calcium phosphate cement, CPC) and analyze its capability. Methods: Tetracalcium phosphate (TTCP) was prepared by the method of high heat. TTCP reacted with in simulated body situation and produced CPC, Its capability was analyzed by scanning electron microscopy (SEM) , X-ray diffraction(XRD). Its density, absorbing water coefficient, macroporosity and campressive strength were measured also. Results: The main element of CPC is hydroxyapatite (HA) , its microstructure comprised of needlelike or petal crystals. The diameter of micropore was 4-10 nm, density was 1.922 g/cm3, macroporosity was 29. 777% , absorbing coefficient was 15. 503%, compressive strength was 42. 70 Mpa. Conclusion: This CPC has three-dimensional spatial structure, its strength meets the need of cancellous bone grafting.

Minimally invasive maxillary sinus augmentation with simultaneous implantation on an elderly patient:A case report

BACKGROUND In this case study,a minimally invasive transalveolar approach using platelet-rich fibrin and bone substitute with simultaneous implantation was carried out in an elderly patient.We analyzed the cone-beam computed tomography(CBCT)findings to evaluate bone regeneration.CASE SUMMARY A 65-year-old female with no contraindications for dental implants and loss of maxillary bilateral molars is described.Examination by CBCT showed the available vertical bone height in the bilateral posterior maxilla was 0.5-6.8 mm in the left and 2.8-6.5 mm in the right.The patient underwent a transalveolar approach using platelet-rich fibrin and bone substitute with simulataneous placement of an implant 10 mm in length.Six months post-surgery,the implant showed excellent osseointegration with the bone graft.Thereafter,full-ceramic crowns were fitted.Follow-up at 2 years demonstrated satisfactory prognosis.CONCLUSION Platelet-rich fibrin and bone substitute can be used to augment the maxillary sinus with a vertical bone height less than 4 mm.

Culture of osteoblasts on bio-derived bones

OBJECTIVE: To study the effect of bio-derived bones, as substitutes of autogenous bone grafts and demineralized cadaver bones, on the attachment, spreading and proliferation of isolated osteoblasts. METHODS: Osteoblasts were isolated from the calvaria of a fetal rabbit through sequential collagenase digestion. In the attachment study, the osteoblasts labeled with 3H-leucine were incubated with the bio-derived bone materials in sterile microcentrifugable tubes for 15, 90 and 180 minutes, and 24 hours, respectively. The attached cells were collected and the radioactivity was measured with liquid scintillation spectrometry. In the proliferation study, the osteoblasts were cultured with the bio-derived bone materials for 24 hours and 3H-thymidine was added during the last 2 hours of the incubation. The attached cells were collected and the radioactivity was measured with liquid scintillation spectrometry. Osteoblasts were seeded on the bone graft materials for 60 or 120 minutes, 24 or 48 hours, and 3 or 7 days, then the co-culture was processed for scanning electron microscopy to observe the interaction of osteoblasts and the bio-derived bone materials. RESULTS: Osteoblasts attached to the bio-derived bone materials in a time-dependent manner. There were significantly (P

Bone grafts and biomaterials substitutes for bone defect repair:A review

Bone grafts have been predominated used to treat bone defects,delayed union or non-union,and spinal fusion in orthopaedic clinically for a period of time,despite the emergency of synthetic bone graft substitutes.Nevertheless,the integration of allogeneic grafts and synthetic substitutes with host bone was found jeopardized in long-term follow-up studies.Hence,the enhancement of osteointegration of these grafts and substitutes with host bone is considerably important.To address this problem,addition of various growth factors,such as bone morphogenetic proteins(BMPs),parathyroid hormone(PTH)and platelet rich plasma(PRP),into structural allografts and synthetic substitutes have been considered.Although clinical applications of these factors have exhibited good bone formation,their further application was limited due to high cost and potential adverse side effects.Alternatively,bioinorganic ions such as magnesium,strontium and zinc are considered as alternative of osteogenic biological factors.Hence,this paper aims to review the currently available bone grafts and bone substitutes as well as the biological and bio-inorganic factors for the treatments of bone defect.

Clinical evaluation following the use of mineralized collagen graft for bone defects in revision total hip arthroplasty

Revision total hip arthroplasty(THA)with massive bone loss has been a real challenge for orthopaedic surgeons.Here we describe an approach using mineralized collagen(MC)graft to reconstruct acetabulum and femur with massive bone defects.We identified 89 patients suffering acetabular or femoral bone defects after primary THA,who required revision THA for this study.During the surgery,MC was applied to reconstruct both the acetabular and femoral defects.Harris hip score was used to evaluate hip function while radiographs were taken to estimate bone formation in the defect regions.The average follow-up period was 33.662.4 months.None of the components needed re-revised.Mean Harris hip scores were 42.563.5 before operation,75.264.0 at 10th month and 95.063.6 at the final follow-up.There were no instances of deep infection,severe venous thrombosis or nerve palsy.The present study demonstrated that MC graft can serve as a promising option for revision THA with massive bone deficiency.Meanwhile,extended follow-up is needed to further prove its long-term performance.

Clinical observation of biomimetic mineralized collagen artificial bone putty for bone reconstruction of calcaneus fracture

This study investigated clinical outcomes of biomimetic mineralized collagen artificial bone putty for bone reconstruction in the treatment of calcaneus fracture.Sixty cases of calcaneal fractures surgically treated with open reduction and internal fixation in our hospital from June 2014–2015 were chosen and randomly divided into two groups,including 30 cases treated with biomimetic mineralized collagen artificial bone putty as treatment group,and 30 cases treated with autogenous ilia as control group.The average follow-up time was 17.263.0 months.The results showed that the surgery duration and postoperative drainage volume of treatment group were significantly lower than control group;there were no statistically significant differences in the fracture healing time,American Orthopaedic Foot and Ankle Society scores at 3 and 12 months after surgery,Bo¨hler’s angle,Gissane’s angle and height of calcaneus between the two groups.There were no significant differences in wound complication and reject reaction between the two groups,while significant difference in donor site complication.As a conclusion,the implantation of biomimetic mineralized collagen artificial bone putty in the open reduction of calcaneal fracture resulted in reliable effect and less complications,which is suitable for clinical applications in the treatment of bone defect in calcaneal fractures.

Nanocomposites and bone regeneration

This manuscript focuses on bone repair/regeneration using tissue engineering strategies, and highlights nanobiotechnology developments leading to novel nanocomposite systems. About 6.5 million fractures occur annually in USA, and about 550,000 of these individual cases required the application of a bone graft. Autogenous and allogenous bone have been most widely used for bone graft based therapies; however, there are significant problems such as donor shortage and risk of infection. Alternatives using synthetic and natural biomaterials have been developed, and some are commercially available for clinical applications requiring bone grafts. However, it remains a great challenge to design an ideal synthetic graft that very closely mimics the bone tissue structurally, and can modulate the desired function in osteoblast and progenitor cell populations. Nanobiomaterials, specifically nanocomposites composed of hydroxyapatite （HA） and/or collagen are extremely promising graft substitutes. The biocomposites can be fabricated to mimic the material composition of native bone tissue, and additionally, when using nano-HA （reduced grain size）, one mimics the structural arrangement of native bone. A good understanding of bone biology and structure is critical to development of bone mimicking graft substitutes. HA and collagen exhibit excellent osteoconductive properties which can further modulate the regenerative/ healing process following fracture injury. Combining with other polymeric biomaterials will reinforce the mechanical properties thus making the novel nano-HA based composites comparable to human bone. We report on recent studies using nanocomposites that have been fabricated as particles and nanofibers for regeneration of segmental bone defects. The research in nanocomposites, highlight a pivotal role in the future development of an ideal orthopaedic implant device, however further significant advancements are necessary to achieve clinical use.

Preparation and degradation characteristic study of bone repair composite of DL-polylactic acid/hydroxyapatite/decalcifying bone matrix

To explore the preparative method an d study the degradation characteristics of bone repair composite of DL polylac tic acid (PDLLA)/hydroxyapatite(HA)/decalcifying bone matrix (DBM) in vitro. Methods: An emulsion blend method was developed to prepare the composite of PDLLA/HA/DBM in weight ratio of PDLLA:HA:DBM= 1.5 2 : 1 1.5 : 1. The dynamic changes of weight, biomechanical property and pH value of PDLLA/ HA/DBM and PDLLA in phosphate buffered saline (PBS, pH 7.4 ) were studied re spectively through degradation tests in vitro. Results: Without being heated, PDLLA, HA and DBM could be synt hesized with the emulsion blend method as bone composite of PDLLA/HA/DBM, which had both osteoconductive and osteoinductive effects. The diameter of the apertu re was 100 400 μm and the gap rate was 71.3 %. During degradation, the pH v alue of PDLLA solution decreased lightly within 2 weeks, but decreased obviously at the end of 4 weeks and the value was 4.0 . While the pH value of PDLLA/H A/DBM kept quite steady and was 6.4 at the end of 12 weeks. The weight of PDLLA changed little within 4 weeks, then changed obviously and was 50% of its initia l weight at the end of 12 weeks. While the weight of PDLLA/HA/DBM changed little within 5 weeks, then changed obviously and was 60% of the initial weight at the end of 12 weeks. The initial biomechanical strength of PDLLA was 1.33 MPa, decreased little within 3 weeks, then changed obviously and kept at 0.11 MP a at the end of 12 weeks. The initial biomechanical strength of PDLLA/HA/DBM was 1.7 MPa, decreased little within 4 weeks, then changed obviously and kept at 0.21 MPa at the end of 12 weeks. Conclusions: The emulsion blend method is a new method to prepa re bone repair materials. As a new bone repair material, PDLLA/HA/DBM is more su itable for regeneration and cell implantation, and the environment during its de gradation is advantageous to the growth of bone cells.

Repair of radius defect with bone-morphogenetic-protein loaded hydroxyapatite/collagen-poly(L-lactic acid) composite

Objective: To explore the method to repair bone defect with bone-morphogenetic-protein loaded hydroxyapatite/collagen-poly(L-lactic acid) composite. Methods: 18 adult beagle dogs were randomly divided into 3 groups. In Group A, bone-morphogenetic-protein (BMP) loaded hydroxyapatite/collagen-poly(L-lactic acid) (HAC-PLA) scaffold was implanted in a 2 cm diaphyseal defect in the radius. In Group B, unloaded pure HAC-PLA scaffold was implanted in the defects. No material was implanted in Group C (control group). The dogs were sacrificed 6 months postoperatively. Features of biocompatibility, biodegradability and osteoinduction were evaluated with histological, radiological examinations and bone mineral density (BMD) measurements. Results: In Group A, the radius defect healed after the treatment with BMP loaded HAC-PLA. BMD at the site of the defect was higher than that of the contralateral radius. Fibrous union developed in the animals of the control group. Conclusions: BMP not only promotes osteogenesis but also accelerates degradation of the biomaterials. Optimized design parameters of a three-dimensional porous biomaterial would give full scope to the role of BMP as an osteoinductive growth factor.

Osteoinductive activity of demineralized bone matrix and deprotenized bone derived from human avascular necrotic femoral head

Objective： To observe the osteoinductive activity of demineralized bone matrix （DBM） and deprotenized bone （DPB） made from human avascular necrotic femoral head. Methods： The femoral head was cut into pieces with the size of 3 mm×3 mm×5 mm, which were made into DBM and DPB. These two kinds of biomaterials were cocultured with human bone mesenchymal stem cells （hBMSCs）. Monolayer cells without biomaterials were cultured as control. Proliferative activity ofhBMSCs was evaluated on days 1, 3, 5, 7 and 14. The concentration of alkaline phosphatase （ALP）, osteocalcin （OC）, and Ca^2＋ were detected on days 1, 7, 14 and 21. Results： Cells cultured in DBM showed higher proliferative activity than did in DPB and monolayer cells （F= 39.773, P〈0.01）. DBM and DPB also had osteoinductive activity. The concentrations of ALP （F=93.162, P〈0.01）, OC （F=236.852, P〈0.01）, Ca^2＋ （F=80.711, P〈0.01）of DBM group were significantly higher than that of DPB and control groups. Conclusions： In vitro, DBM and DPB made from avascular necrotic femoral head have osteoinductive activity when cocultured with hBMSCs, and the former is stronger than the latter.

Cytocompatible 3D chitosan/hydroxyapatite composites endowed with antibacterial properties:toward a self-sterilized bone tissue engineering scaffold

Bone tissue scaffolds based on bioactive polymer–hydroxyapatite composites have caused infections that seriously limit their extended application. In this study, we proposed a practical ion substitution method to synthesize in situ silver phosphate on the surface of a two-level, threedimensional chitosan/nano-hydroxyapatite scaffold. A release test of silver ions in a phosphate buffered saline(PBS) solution was performed to demonstrate that silver ions were released continuously from the silver phosphate during the initial 6 days of the study. The antibacterial property and cytocompatibility of the scaffolds treated with different concentrations of silver nitrate solution were assessed by in vitro assays with Escherichia coli and MC3T3-E1, respectively. The ability of the silver-containing scaffolds to induce bacteriostasis was confirmed by the inhibition zone(15 mm) and high bactericidal rate([99 %). Cell proliferation, morphology and the alkaline phosphatase activity of MC3T3-E1 cultured on the scaffold with low silver phosphate contents were comparable with those cultured on control samples.

Effects of pore interconnectivity on bone regeneration in carbonate apatite blocks

Porous architecture in bone substitutes,notably the interconnectivity of pores,is a critical factor for bone ingrowth.However,controlling the pore interconnectivity while maintaining the microarchitecture has not yet been achieved using conventional methods,such as sintering.Herein,we fabricated a porous block using the crystal growth of calcium sulfate dihydrate,and controlled the pore interconnectivity by limiting the region of crystal growth.The calcium sulfate dihydrate blocks were transformed to bone apatite,carbonate apatite(CO_(3)Ap)through dissolution–precipitation reactions.Thus,CO_(3)Ap blocks with 15%and 30%interconnected pore volumes were obtained while maintaining the microarchitecture:they were designated as CO_(3)Ap-15 and CO_(3)Ap-30,respectively.At 4 weeks after implantation in a rabbit femur defect,new bone formed throughout CO_(3)Ap-30,whereas little bone was formed in the center region of CO_(3)Ap-15.At 12 weeks after implantation,a large portion of CO_(3)Ap-30 was replaced with new bone and the boundary with the host bone became blurred.In contrast,CO_(3)Ap-15 remained in the defect and the boundary with the host bone was still clear.Thus,the interconnected pores promote bone ingrowth,followed by replacement of the material with new bone.These findings provide a useful guide for designing bone substitutes for rapid bone regeneration.

Powder metallurgy with space holder for porous titanium implants:A review

One of the biggest challenges in the biocompatibility of implantable metals is the prevention of the stress shielding effect,which is related to the coupling of the bone-metal mechanical properties.This stress shielding phenomenon provokes bone resorption and the consequent adverse effects on prosthesis fixation.However,it can be inhibited by adapting the stiffness of the implant material.Since the use of titanium(Ti)porous structures is a great alternative not only to inhibit this effect but also to improve the osteointegration of orthopedic and dental implants,a brief description of the techniques used for their manufacturing and a review of the current commercialized implants produced from porous Ti assemblies are compiled in this work.As powder metallurgy(PM)with space holder(SH)is a powerful technology used to produce porous Ti structures,it is here discussed its potential for the fabrication of medical devices from the perspectives of both design and manufacture.The most important parameters of the technique such as the size and shape of the initial metallic particles,the SH and binder type of materials,the compaction pressure of the green form,and in the sintering stage,the temperature,atmosphere,and time are reviewed according to the bibliography reported.Furthermore,the importance of the porosity and its types together with the influence of the mentioned parameters in the final porosity and,consequently,in the ultimate mechanical properties of the structure are discussed.Finally,a few examples of the PM-SH application for the manufacturing of orthopedic implants are presented.

Magnesium Alloy for Repair of Lateral Tibial Plateau Defect in Minipig Model

Bone graft substitutes are widely-studied as alternatives to bone grafts in the clinic. The currently available products are mostly ceramics and polymers. Considerable progress has been made in the study of the biodegradable magnesium alloys, which possess the necessary attributions of a suitable substitute, including an excellent mechanical property. In the present study, a minipig model of a lateral tibial plateau defect was used to evaluate the effectiveness of a magnesium alloy in the repair of a critical-sized defect. The micro-arc oxidation （MAO）-coated ZK60 alloy tablets and medical-grade calcium sulfate pellets were used as the test and control materials, respectively. Bone morphology was monitored by computed tomography after the implantation for 2 and 4 months. It was found that the bone morphology in minipigs following magnesium treatment was similar to that of the normal bone, whereas an abnormal and concave morphology was displayed following the calcium sulfate treatment. The average bone healing rate for the magnesium-treated defects was higher than that of the calcium sulfate-treated defects at the first 4 months following the implantation. Overall, magnesium treatment appeared to calcium sulfate treatment. Thus, the MAO-coated ZK60 al substitute, and further research on its biological activity in improve the defect repair as compared with the oy appears to be a useful biocompatible bone graft vivo is needed.