Introduction. Porous scaffolds for bone ingrowth have numerous applications, including correcting deformities in the foot and ankle. Various materials and shapes may be selected for bridging an osteotomy in a corrective procedure. This research explores the performance of commercially pure Titanium (CPTi) and Tantalum (Ta) porous scaffold materials for use in foot and ankle applications under simplified compression loading. Methods. Finite element analysis was performed to evaluate von Mises stress in 3 porous implant designs: 1) a CPTi foot and ankle implant (Fig 1) 2) a similar Ta implant (wedge angle = 5°) and 3) a similar Ta implant with an increased wedge angle of 20°. Properties were assigned per reported material and density specifications. Clinically relevant axial compressive load of 2.5X BW (2154 N) was applied through fixtures which conform to ASTM F2077–11. Compressive yield and fatigue strength was evaluated per ASTM F2077–11 to compare CPTi performance in design 1 to the Ta performance of design 3. Results. FEA results indicate peak stresses at fixture contact locations. Similar designs (CPTi design 1 and Ta design 2) resulted in similar von Mises stresses (Fig 1). Increasing the wedge angle (Ta design 3) increased stress by 15%. The static compressive yield strength of CPTi design 1 (20,560 N) was similar to the Ta design 3 (20,902 N), with yield manifesting as barreling and crushing of the components (Fig 2a). However, the fatigue strength of CPTi (6,000 N) was 40% lower than the Ta design 3 (9,500 N) (Fig 3). In both cases fracture initiated from regions of highest stress predicted in FEA. Fracture progression was not instantaneous and was characterized by an accumulation of damage (Fig 2b–c) leading to gross component fracture and loss of implant integrity. Discussion. FEA is a useful tool to determine stress variations and can be used to identify worst case within a material: in this case, a larger implant wedge angle leads to higher stresses. Additionally, FEA accurately predicted fracture initiation location. However, material selection plays a large role in porous implant performance: although FEA predicted higher stresses in a Ta component with a greater wedge angle than a similar sized CPTi component, static compressive strengths were nearly identical, and the Ta component had 58% higher fatigue strength. When selecting a material or geometry for an implant application, both FEA and static testing allow for rapid evaluation of designs. However, caution should be used in interpreting the results: the ultimate performance of an implant in-vivo will depend on its ability to maintain integrity over a long period of time, and should be characterized by dynamic testing

Bone marrow-derived mesenchymal stromal stem cells (BMSCs) are a promising cell source for treating articular cartilage defects. Quality of cartilaginous repair tissue following BMSC transplantation has been shown to correlate with functional outcome. Therefore, tissue-engineering variables, such as cell expansion environment and seeding density of scaffolds, are currently under investigation. The objectives of this study were to demonstrate chondrogenic differentiation of BMSCs seeded within a collagen I scaffold following isolation and expansion in two-dimensional (2D) and three-dimensional (3D) environments, and assess the impact of seeding density on in vitro chondrogenesis. It was hypothesised that both expansion protocols would produce BMSCs capable of hyaline-like chondrogenesis with an optimal seeding density of 10 million cells/cm3.

Ovine BMSCs were isolated in a 2D environment by plastic adherence, expanded to passage two in flasks containing expansion medium, and seeded within collagen I scaffolds (6 mm diameter, 3.5 mm thickness and 0.115 ± 0.020 mm pore size; Integra LifeSciences Corp.) at densities of 50, 10, 5, 1, and 0.5 million BMSCs/cm3. For 3D isolation and expansion, bone marrow aspirates containing known quantities of mononucleated cells (BMNCs) were seeded on scaffolds at 50, 10, 5, 1, and 0.5 million BMNCs/cm3 and cultured in expansion medium for an equivalent duration to 2D expansion. All cell-scaffold constructs were differentiated in vitro in chondrogenic medium containing transforming growth factor-beta three for 21 days and assessed with RT-qPCR, safranin O staining, histological scoring using the Bern Score, collagen immunofluorescence, and glycosaminoglycan (GAG) quantification.

Two dimensional-expanded BMSCs seeded at all densities were capable of proteoglycan production and displayed increased expressions of aggrecan and collagen II mRNA relative to pre-differentiation controls. Collagen II deposition was apparent in scaffolds seeded at 0.5–10 million BMSCs/cm3. Chondrogenesis of 2D-expanded BMSCs was most pronounced in scaffolds seeded at 5–10 million BMSCs/cm3 based on aggrecan and collagen II mRNA, safranin O staining, Bern Score, total GAG, and GAG/DNA. For 3D-expanded BMSC-seeded scaffolds, increased aggrecan and collagen II mRNA expressions relative to controls were noted with all densities. Proteoglycan deposition was present in scaffolds seeded at 0.5–50 million BMNCs/cm3, while collagen II deposition occurred in scaffolds seeded at 10–50 million BMNCs/cm3. The highest levels of aggrecan and collagen II mRNA, Bern Score, total GAG, and GAG/DNA occurred with seeding at 50 million BMNCs/cm3.

Within a collagen I scaffold, 2D- and 3D-expanded BMSCs are capable of hyaline-like chondrogenesis with optimal cell seeding densities of 5–10 million BMSCs/cm3 and 50 million BMNCs/cm3, respectively. Accordingly, these densities could be considered when seeding collagen I scaffolds in BMSC transplantation protocols.

Oxide ceramics, such as alumina and zirconia have been used extensively in arthroplasty bearings to address bearing wear and mitigate its delayed, undesirable consequences. In contrast to oxide ceramics that are well-known to orthopaedic surgeons, silicon nitride (Si. 3. N. 4. ) is a non-oxide ceramic that has been investigated extensively in very demanding industrial applications, such as precision bearings, cutting tools, turbo-machinery, and electronics. For the past four years, Si. 3. N. 4. has also been used as a biomaterial in the human body; specifically in spinal fusion surgery. As a implantable biomaterial, Si. 3. N. 4. has unique properties, such as high strength and fracture toughness, inherent chemical and phase stability, low wear, proven biocompatibility, excellent radiographic imaging, antibacterial advantages, and superior osteointegration. This property combination has proven beneficial and desirable in orthopaedic implants made for spinal fusion, spinal disc reconstruction, hip and knee arthroplasty, and other total joints (Fig. 1). The physical properties, shapes, sizes and surface features of Si. 3. N. 4. can be engineered for each application – ranging from dense, finely polished articulation components, to highly porous scaffolds that promote osteointegration. Both porous and polished surfaces can be incorporated in the same implant, opening a number of opportunities for arthroplasty implant design. Crack propagation modes for in situ toughened Si. 3. N. 4. differ favorably from those of conventional ceramics, rendering Si. 3. N. 4. extremely resistant to catastrophic failure in vivo (Fig. 2). Most significantly, our recent work has shown that Si. 3. N. 4. is resistant to bacterial biofilm formation, colonization and growth, when compared to medical-grade PEEK and titanium. These anti-infective characteristics are particularly valuable for in vivo implantation. We will present the unique properties and characteristics of Si. 3. N. 4. , and compare these to other ceramic and non-ceramic biomaterials. Si. 3. N. 4. was once used only in industrial applications, but early data show that this novel biomaterial is positively impacting orthopaedic care and will continue to do so into the future

Developing biomaterials for bone regeneration that are highly bioactive, resorbable and mechanically strong remains a challenge. Zreiqat's lab recently developed novel scaffolds through the controlled substitution of strontium (Sr) and zinc (Zn) into calcium silicate, to form Sr-Hardystonite and Hardystonite, respectively and investigated their in vivo biocompatibility and osteoconductivity. We synthesized 3D scaffolds of Sr-Hardystonite, Hardystonite and compared them to the clinically used tricalcium phosphate (micro-TCP) (6 × 6 × 6 mm) using a polyurethane foam template to produce a porous scaffold. The scaffolds were surgically implanted in the proximal tibial metaphysis of each tibia of Female Wistar rats. Animals were sacrificed at three weeks and six weeks post-implantation and bone formation and scaffold resorption were assessed by microcomputed tomography (micro-CT) histomorphometry and histology. Histological staining on undecalcified sections included Toluidine blue, tartrate-resistant acid phosphatase (TRAP) and alkaline phosphatase (ALP). The bone formation rate and mineral apposition rate will be determined by analysing the extent and separation of fluorescent markers by fluorescent microscopy micro-CT results revealed higher resorbability of the developed scaffolds (Sr-Hardystonite and Hardystonite) which was more pronounced with the Sr-Hardystonite. Toluidine blue staining revealed that the developed ceramics were well tolerated with no signs of rejection, necrosis, or infection. At three weeks post implantation, apparent bone formation was evident both at the periphery and within the pores of the all the scaffolds tested. Bone filled in the pores of the Sr- Hardystonite and Hardystonite scaffolds and was in close contact with the ceramic. In contrast, the control scaffolds showed more limited bone ingrowth and a cellular layer separating the ceramic scaffolds from the bone. By six weeks the Hardystonite and Sr Hardystonite scaffolds were integrated with the bone with most pores filled with new bone. The control scaffold showed new bone formation in the plane of the cortical bone but little new bone where the scaffold entered the marrow space. Sr Hardystonite showed the greatest resorbability with replacement of the ceramic material by bone. We have developed novel engineered scaffolds (Sr-Hardystonite) for bone tissue regeneration. The developed scaffolds resorbed faster than the clinically used micro- TCP with greater amount of bone formation replacing the resorbed scaffold

The spine is one of the most common sites of bony metastasis, with 80% of prostate, lung, and breast cancers metastasizing to the vertebrae resulting in significant morbidity. Current treatment modalities are systemic chemotherapy, such as Doxorubicin (Dox), administered after resection to prevent cancer recurrence, and systemic antiresorptive medication, such as Zolendronate (Zol), to prevent tumor-induced bone destruction. The large systemic doses required to elicit an adequate effect in the spine often leads to significant side-effects by both drugs, limiting their prolonged use and effectiveness. Recently published work by our lab has shown that biocompatible 3D-printed porous polymer scaffolds are an effective way of delivering Dox locally over a sustained period while inhibiting tumor growth in vitro. Our lab has also generated promising results regarding antitumor properties of Zol in vitro. We aim to develop 3D-printed scaffolds to deliver a combination of Zol and Dox that can potentially allow for a synergistic antitumor activity while preventing concurrent bone loss locally at the site of a tumor, avoiding long systemic exposure to these drugs and decreasing side effects in the clinical setting. The PORO Lay polymer filaments are 3D-printed into 5mm diameter disks, washed with deionized water and loaded with Dox or Zol in aqueous buffer over 7 days. Dox or Zol-containing supernatant was collected daily and the drug release was analyzed over time in a fluorescence plate reader. The polymer-drug (Dox or Zol) release was tested in vitro on prostate and lung cancer cell lines and on prostate- or lung-induced bone metastases cells. Alternatively, direct drug treatment was also carried out on the same cells in vitro. Following treatment, all cells were subject to proliferation assay (MTT and alamar blue), viability assay (LIVE/DEAD), migration assay (Boyden chamber) and invasion assay (3D gel matrix). 3D-printed scaffolds loaded with both Dox and Zol will also be tested on cells. We have established an effective dose (EC50) for prostate and lung cancer cell lines and bone metastases cells with direct treatment with Zol or Dox. We have titrated the drug loading of scaffolds to allow for a release amount of Dox at the EC50 dose over 7 days. In ongoing experiments, we are testing the release of Zol. We have shown Dox releasing scaffolds inhibit cancer cell growth in a 2D culture over 7 days using the above cellular assays and testing the scaffolds with Zol is currently being analyzed. 3D-printed porous polymers like the PORO Lay series of products offer a novel and versatile opportunity for delivery of drugs in future clinical settings. They can decrease systemic exposure of drugs while at the same time concentrating the drugs effect at the site of tumors and consequently inhibit tumor proliferation. Their ability to be loaded with multiple drugs can allow for achieving multiple goals while taking advantage of synergistic effects of different drugs. The ability to 3D-print these polymers can allow for production of custom implants that offer better structural support for bone growth

Introduction. Currently, there is a focus on the development of novel materials to articulate against cartilage. Such materials should either eliminate or delay the necessity of total joint replacement. While cobalt-chromium (CoCr) alloy is still a material of choice and used for hemi-arthroplasties, spacers, and repair plugs, alternative materials are being studied. Pyrolytic carbon (PyC) is a biocompatible material that has been available since the 1980s. It has been widely and successfully used in small joints of the foot and the hand, but its tribological effects in direct comparison to cobalt-chromium (CoCr) remain to be investigated. Methods. A four station simulator (Figure 1), mimicking joint load and motion, was used for testing. The simulator is housed in an incubator, which and provides the necessary environmental conditions for cartilage survival. Articular cartilage disks (14mm in diameter) were obtained from the trochleas of six to eight months old steer for testing and free-swelling controls. Disks (n=8 per material) were placed in porous polyethylene scaffolds within polypropylene cups and mounted onto the simulator to articulate against 28mm balls of either PyC or CoCr. Each ball was pressed onto the cartilage disk with 40N. In order to allow fluidal load support, the contact migrated over the biphasic cartilage with a 5.2 mm excursion. Concomitantly, the ball oscillated with ±30° at 1 Hz. Testing was conducted for three hours per day over 10 days in Mini ITS medium. Media samples were collected at the end of each three hour test. Upon test commencement, media was pooled (days 1, 4, 7, 10) and analyzed for proteoglycans/sGAGs and hydroxyproline. In addition, total material release into media was estimated by determining the dry weight increase of media samples. For this purpose, 1 ml aliquots of fresh and test media were dialyzed, lyophilized and weighed on a high precision balance. Disk morphology and cell viability were histologically examined. Results. During each day of testing, cartilage control, CoCr and PyC samples released an average of 0.236, 0.253, re 0.268 mg/mL of glycol-proteins into the medium. After running-in (day 1), the increase was highly linear (R. 2. >0.99) and similar for all three testing conditions. Proteoglycan/GAG (Figure 2) and hydroxyproline release (Figure 3) were also similar for both materials (p=0.46 re. p=0.12), but significantly different from control (p<0.01). Histological and cell viability images support the hypothesis of superficial zone damage of the cartilage disks for both materials. Cell viability was not different from control (p>0.33). Discussion. The performance of PyC and CoCr was comparable using this in vitro simulation model, however appears not optimal. The observed surface fibrillation may lead to tissue breakdown in the long-term. The wear mechanism has yet to be elucidated but appears to be of adhesive nature. The lack of proteins in the medium might have suppressed boundary lubrication and thus may have played a role in the non-optimal performance of these materials. In summary, a live tissue model of articular cartilage found no difference comparing pyrolytic carbon with the current clinical gold standard CoCr

Cell-scaffold based cartilage tissue engineering strategies provide the potential to restore long-term function to damaged articular cartilage. A major hurdle in such strategies is the adequate (uniform and sufficient) population of porous 3D scaffolds with cells, but more importantly, the generation of engineered tissue of sufficient quality of clinically relevant size. We describe a novel approach to engineer cartilage grafts using pre-differentiated micro-mass cartilage pellets, integrated into specifically designed 3D plotted scaffolds. Expanded (P2) human nasal chondrocytes (HNCs) or bone marrow-derived mesenchymal stem cells (MSCs) from 3 donors (age 47–62 years) were micro-mass cell pellet cultivated at 5 × 105 cells/pellet for 4 days. Subsequently, pellets were integrated into degradable 3D Printed polymer (PEGT/PBT) scaffolds with 1mm fibre spacing. Constructs were cultured dynamically in spinner flasks for a total of 21 days. As a pellet-free control, expanded HNCs were spinner flask seeded into PEGT/PBT fibre plotted scaffolds. Constructs were assessed via histology (Safranin-O staining), biochemistry (glycosaminoglycan (GAG) and DNA content) and collagen type I and II mRNA expression. After 4 days, micro-mass cultured pellets could be successfully integrated into the fibre plotted scaffolds. DNA content of pellet integrated constructs was 4.0-fold±1.3 higher compared to single seeded constructs. At day 21, cartilage tissue was uniformly distributed throughout pellet integrated scaffolds, with minimal cell necrosis observed within the core. GAG/DNA and collagen type II mRNA expression were significantly higher (2.5-fold±0.5 and 3.1-fold±0.4 respectively) in pellet versus single cell seeded constructs. Furthermore, compared to single cell, the pellet seeded constructs contained significantly more total GAG and DNA (1.6-fold±0.1 and 3.1-fold±1.0 respectively). We developed a novel 3D tissue assembly approach for cartilage tissue engineering which significantly improved the seeding efficiency (∼100%), as well as tissue uniformity and integrity compared to more traditional seeding approaches using single cell suspensions. Furthermore, the integration of micro-mass cell pellets into 3D plotted PEGT/PBT scaffolds significantly improved the amount and quality of tissue engineered cartilage

INTRODUCTION. The menisci play a fundamental biomechanical role in the knee and also help in the maintaining of the articular homeostasis; thus, either a lesion or the complete absence of the menisci can invalidate the physiological function of the knee causing important damages, even at long term. Unfortunately, meniscal tears are often found during the ordinary orthopaedic practice while the regenerative potential of this kind of tissue is very low and limited to its peripheral-vascularized part; this is why the majority of these common arthroscopic findings are not reparable and often the surgeon is almost forced to perform a partial, subtotal or even total meniscectomy, regardless of the well-known consequences of this kind of surgery. MATERIALS AND METHODS. Recently a porous, biodegradable scaffold made of an aliphatic polyurethane (Actifit(tm),Orteq Ltd) has been developed for the arthroscopic treatment of partial and irreparable meniscal tears; thanks to its particular structure, this scaffold facilitates the regeneration of the removed meniscal part, preventing the potential cartilage damage due to its complete or partial lack. We performed a prospective clinical study on 17 patients affected by a massive loss of meniscal substance either medial or lateral associated with intraarticular or global knee pain and/or swelling. We analyzed the patient both clinically and by using the International Knee Document Committee's (IKDC) Subjective and Objective Knee Evaluation Form. We also assessed the sport activity resumption by comparing the Tegner score at the time of the very first visit with the presurgery and prelesional ones. Finally, we also organized a control MRI at 6 and 12 months after surgery. DISCUSSION. Our preliminary results are encouraging and they confirm the clinical experiences of other study groups. Apparently, the properties of this scaffold help in vessels formation and tissue regeneration potentially allowing the restoration of the surgically removed portion and preventing, or delaying at least, both chondral and articular degeneration. We also performed some biopsy associated arthroscopic “second-looks” that reinforced the already good clinical results; the biopsies also confirmed the new tissue ingrowth into the biomaterial, potentially leading to the replacement of the previously removed damaged tissue. CONCLUSIONS. Preliminary results suggest that this surgical procedure can be considered a really promising method for the treatment of both inveterate and symptomatic meniscal tears; however, other randomized studies with a longer follow-up should be done to confirm its reliability and potentialities

Biomaterials used in regenerative medicine should be able to support and promote the growth and repair of natural tissues. Bioactive glasses (BGs) have a great potential for applications in bone tissue engineering [1, 2]. As it is well known BGs can bond to host bone and stimulate bone cells toward osteogenesis. Silicate BGs, e.g. 45S5 Bioglass® (composition in wt.%: 45 SiO. 2. , 6 P. 2. O. 5. , 24, 5 Na. 2. O and 24.5 CaO), exhibit positive characteristics for bone engineering applications considering that reactions on the material surface induce the release of critical concentrations of soluble Si, Ca, P and Na ions, which can lead to the up regulation of different genes in osteoblastic cells, which in turn promote rapid bone formation. BGs are also increasingly investigated for their angiogenic properties. This presentation is focused on cell behavior of osteoblast-like cells and osteoclast-like cells on BGs with varying sample geometry (including dense discs for material evaluation and coatings of highly porous Al. 2. O. 3. -scaffolds as an example of load-bearing implants). To obtain mechanically competent porous samples with trabecular architecture analogous to those of cancellous bone, in this study Al. 2. O. 3. scaffolds were fabricated by the well-known foam replication method and coated with Bioglass® by dip coating. The resulted geometry and porosity were proven by SEM and μCT. Originating from peripheral blood mononuclear cells formed multinucleated giant cells, i.e. osteoclast-like cells, after 3 weeks of stimulation with RANKL and M-CSF. Thus, the bioactive glass surface can be considered a promising material for bone healing, providing a surface for bone remodeling. Osteoblast-like cells and bone marrow stromal cells were seeded on dense bioactive glass substrates and coatings showing an initial inhibited cell attachment but later a strong osteogenic differentiation. Additionally, cell attachment and differentiation studies were carried out by staining cytoskeleton and measuring specific alkaline phosphatase activity. In this context, 45S5 bioactive glass surfaces can be considered a highly promising material for bone tissue regeneration, providing very fast kinetics for bone-like hydroxyapatite formation (mineralization). Our examinations revealed good results in vitro for cell seeding efficacy, cell attachment, viability, proliferation and cell penetration onto dense and porous Bioglass®-coated scaffolds. Recent in vivo investigations [3] have revealed also the angiogenic potential of bioactive glass both in particulate form and as 3D scaffolds confirming the high potential of BGs for bone regeneration strategies at different scales. Implant surfaces based on bioactive glasses offer new opportunities to develop these advanced biomaterials for the next generation of implantable devices and tissue scaffolds with desired tissue-implant interaction

Purpose. Traditionally, the gold standard for bone grafting has been either autografts or allografts. Whilst autografts are still widely used, drawbacks such as donor site morbidity are shifting the market rapidly toward the use of orthobiologic bone graft substitutes. This study investigated the in vivo performance of a novel (W02008096334) collagen-hydroxyapatite (CHA) bone graft substitute material as an osteoinductive tissue engineering scaffold. This highly porous CHA scaffold offers significantly increased mechanical strength over collagen-only scaffolds while still exhibiting an extremely high porosity (≈ 99%), and an osteoinductive hydroxyapatite phase [1]. This study assessed the ability of the CHA scaffolds to heal critical-sized (15 mm) long bone segmental defects in vivo, as a viable alternative to autologous bone grafts. Method. Collagen-HA (CHA) composite scaffolds were fabricated based on a previously-described freeze-drying technique [1]. After freeze-drying, these scaffolds were subjected to a dehydrothermal treatment and subsequently chemically crosslinked using EDAC. In vivo performance was assessed using a critical size segmental radial defect (15 mm) introduced into 16 young adult New Zealand White Rabbits under Irish Government license. Animals were divided into three groups; (i) an empty defect group (negative control), (ii) an autogenous bone graft group (positive control) and (iii) a CHA scaffold group (CHA). Segmental defect healing in all animals was assessed using plain X-Ray analysis, at four time-points (0, 6, 12 and 16 weeks). MicroCT and histological analysis were carried out at week 16. Results. Empty defect groups at all time points resulted in non-union of the segmental defect bone ends. Autogenous bone graft groups exhibited good filling of the segmental defect with extensive callus formation but even after 16 weeks showed poor remodelling. Although autogenous bone graft groups showed evidence of mineralized tissue within the defect, tissue healing appeared relatively uncontrolled (Figure 1a). CHA scaffold groups exhibited extensive bone healing as early as 6 weeks. By week 16, CHA defects showed complete bridging across the entire defect (figures 1b, 2b, 3b, 4b), development of a continuous marrow cavity (Figures 2b, 3b, 4b) and evidence of remodelling. Conclusion. The results of this study provide clear evidence that Collagen-HA scaffolds, can perform at least as well as autogenous bone grafts. This study provides strong evidence that after a relatively short time in vivo, CHA scaffolds can result in a more complete and homogenous bone healing response and have the potential to offer improved bone tissue formation above that of autogenous bone. More importantly, this study provides strong evidence that the use of low stiffness, organic, biodegradable scaffolds in fully load-bearing defects is not only successful but arguably produces significantly improved results when compared with the current Gold Standard, autogenous bone grafting