Aim. Biofilm-related infections represent a recurrent problem in the orthopaedic setting. In recent years, great interest was directed towards the identification of novel molecules capable to interfere with pathogens adhesion and biofilm formation on implant surfaces. In this study, two stable forms of α-tocopherol, the hydrophobic acetate ester and the water-soluble phosphate ester, were tested in vitro as coating for titanium prostheses. Method. Antimicrobial activity against microorganisms responsible of prosthetic and joints infections was assessed by broth microdilution method. In addition, α-tocopherol esters were evaluated for both their ability to hamper bacterial adhesion and biofilm formation on sandblasted titanium surfaces. Results. Only α-tocopheryl phosphate displayed antimicrobial activity against the tested strains. Both esters were able to significantly interfere with bacterial adhesion and to prevent biofilm formation, especially by Staphylococcus aureus and Staphylococcus epidermidis. The activity of α-tocopheryl phosphate was greater than that of α-tocopheryl acetate. Alterations at membrane levels have been reported in literature1 and may be likely responsible for the interference on bacterial adhesion and biofilm formation shown by α-tocopherol esters. Conclusions. Although further studies are needed to better investigate the mechanisms of action and the spectrum of activity of α-tocopherol esters, these characteristics, together with the positive effect on wound healing and immune response, make these molecules promising candidate for coating in order to prevent implant-associated infections

Introduction. Osteoporotic intertrochanteric fracture (ITF) is frequent injuries affecting elderly, osteoporotic patients leading to significant morbidity and mortality. Successful prognosis including union and alignment is challenging even though initial successful reduction with internal fixation. Although many factors are related to the patient's final prognosis. Well reduction with stable fracture fixation is still the goal of treatment to improve the quality of life and decrease morbidity in patients with hip fractures, but this in turn depends on the type of fracture and bone quality. Poor bone quality is responsible for common complications, such as failure of fixation, varus collapse and lag screw cut-out, in elderly patients. Kim et al. found that the complication rate when using conventional DHS in unstable ITFs can be as high as 50% because of screw cut-out. We used the dynamic hip screws (DHS) strengthened by calcium phosphate cement (CPC) for treatment femoral intertrochanteric fracture and review the prognosis of our patients. Materials and Methods. From January of 2011 to January of 2014, 42 patients with femoral intertrochanteric fracture underwent surgery with DHS strengthened by CPC. Comparisons were made between the DHS plus CPC group with the other patients with only DHS used in our department. All patients were followed up for an average time of 14.8(6 to 24) months. X-ray was reviewed for the conditions of union and implant failure. Results. In DHS group, fixation failure happened in 3 case, delayed union and coax varus deformity in 2 cases. IN DHS plus CPC group, all fractures healed uneventfully, there is no non-union or malunion in this group. There is only 1 fixation cut-out and 1 secondary lag screw sliding was noted, however, union was still well over fracture site in this case, the patient had no clinical symptoms. Discussion. Residual bony defects present after DHS fixation in intertrochanteric fracture may lead to postoperative complications, including nonunion or implant failure. DHS strengthened by CPC is reliable fixation for old patients with intertrochanteric fracture, We demonstrated that augmentation of the bony defect with dynamic hip screw by reinforced calcium phosphate cement significantly improved the strength of osteoporotic bone, prevent screw loosening, and promote early healing of fracture. The patients can be decreased the risk of refracture and allow early weight bearing, especially in elderly patients with osteoporotic bone

Aim. Chronic osteomyelitis often requires surgical debridement and local antibiotic treatment. Disadvantages of PMMA carriers include low dose release and the requirement of surgical removal in the case of PMMA-beads. Synthetic nanocrystalline calcium phosphate (nCP) materials, which mimic the chemical structure of the mineral composition of bone, have been well accepted as bone grafting materials due to their consistent osteoconductivity, ease of use, and mechanical properties. Such a material which remodels into native bone is a much more attractive option. The aim of this study is to investigate the release of gentamicin from CaP in vitro and in vivo when implanted in a rabbit femoral condyle defect. Method. Three formulations of nCP were evaluated in this study: putty, paste and porous. Four cylindrical dowels were made for each group with gentamicin sulphate at a concentration of 20mg/cc of paste. Material was eluted in PBS at 37C and pH 7.0 and elutions were tested every day up to 30 days. Eighteen New Zealand white rabbits will undergo surgeries. Briefly, a drill defect will be created in the metaphyseal bone of the lateral femoral condyle. The formulations will be implanted in the created defect at time of surgery and the wound will be closed. Blood will be collected regularly and analysed for gentamicin titers. Animals will be sacrificed at 6wk, 12wk or 24wk. Explanted femurs will be fixed, sectioned and stained. Results. At 7 days the in vitro elution, showed a continued release of gentamicin. A large amount of gentamicin is released within the first day followed by a slow controlled release. The nCP putty shows the slowest release, followed by the paste and porous formulations respectively. There is a significant increase in the elution with an increase in porosity of the material. We expect to observe a similar trend in the rabbit study with an improved healing. At 6wk we expect the implant material to be still present at the site of implantation, which would remodel by 12wk and 24wk to significant levels due to active ossification. Conclusions. nCP materials, which undergo remodelling, can be used an effective carrier for gentamicin or other antibiotic agents. Because of its potentially prolonged release of high levels of antimicrobial agents, this system could maintain long-term antibacterial effectiveness locally

Background. Calcium phosphate cement (CPC) is a promising biomaterial which can be used in numerous medical procedures for bone tissue repairing because of its excellent osteoconductivity. An injectable preparation and relatively short consolidation time are particularly useful characteristics of CPC. However, the low strength of CPC and its brittleness restrict its use. One method for toughening brittle CPC is to incorporate fibrous materials into its matrix to create a composite structure. Fibers are widely used to reinforce matrix materials in a variety of areas. Objective. We hypothesized that there must be an optimal fiber length and structure which can balance these conflicting aspects of fiber reinforcement. The purpose of this study is to prove our conjectures that adding a small amount of short fibers significantly improves the hardness and the toughness of CPC while maintaining its injectability with a syringe and that fiber morphologies that have crimps and surface roughness are favorable for reinforcing. Material and Methods. We used 3 types of short fibers of approximately 20–50 micrometer in diameter and 2 mm in length in this study: crimpy wool, crimpy polyethylene and straight polyethylene fibers. All of the materials were prepared by mixing a solvent with CPC powder with or without fiber. We grouped as follow, the control group, the wool group, the crimpy polyethylene group, the straight polyethylene group. After soaking in 37 degrees Celsius Simulated Body Fluid∗∗∗∗∗ for 1, 3, or 7 days, they were tested for each period. Impact strength test by the falling weight and compression test were performed. Result. In the impact strength test, after soaking for 1 day, impact resistance in the wool group was approximately 180 times greater than in the control group. When soaking for 3 days or more, impact resistance of wool group improve better than control group. The impact resistance of the wool group was the greatest among the four groups in soaking for 3 days. In the compression test, the yield strength and ultimate strength of the wool group were significantly higher than ultimate strength of the control group. The wool group has stress–strain curves that are typical of those of ductile materials, whereas the stress–strain curves of the control group resemble those of brittle materials. This indicates that fiber reinforcement drastically alters the physical properties of CPC converting it from brittle to ductile. Conclusion. In the present study, we sought to develop a method for producing injectable fiber-reinforced CPC. We focused on morphology and surface roughness of fiber in the reinforcement of CPC. This study clearly showed that CPC was substantially strengthened and toughened by crimpy short fiber reinforcement. CPC reinforced with short fibers which have morphology similar to wool should be a promising tool for orthopedic surgeons

Introduction. The ability of activated platelets to induce cellular proliferation is well recognised. In a previous diffusion model, platelets combined with Tri-calcium phosphate (TCP) led to an osteoprogenitor mitogenic response followed by cellular differentiation. This study was designed to look at osteoprogenitor responses when cultured directly onto TCP granules combined with activated platelets. Method. Human osteoprogenitors were loaded onto TCP with activated platelets at a low seeding density and high seeding densities. Cellular proliferation was assessed using the pico-green DNA content analysis. Differentiation towards osteoblastic phenotype was assessed using an alkaline phosphatase assay. RNA extraction, reverse transcription and quantitative real-time polymerase chain reaction was used to assess gene expression for type 1 collagen and osteocalcin. Histological assessment for live/dead staining and alkaline phosphatase was used on cultured granule samples. Results. In the low seeding density, platelets induced an early proliferative response compared with controls. After 14 days of culture the cells had not differentiated to an osteoblastic phenotype. When seeded at high densities, cellular differentiation was induced by the activated platelets. Significant cellular proliferation was not observed after seeding at high density. Conclusions. This study demonstrates that osteoprogenitors respond to the local environment which is modulated by both cell-cell contact factors and inflammatory cytokines from the platelets. This study helps to define the concentration of progenitors and platelets needed for further on-growth studies. It may also help define the optimal conditions for seeding cells and platelets for clinical use of composite bone graft substitutes

A novel injectable hydrogel based on DNA and silicate nanodisks was fabricated and optimized to obtain a suitable drug delivery platform for biomedical applications. Precisely, the hydrogel was designed by combining two different type of networks: a first network (type A) made of interconnections between neighboring DNA strands and a second one (type B) consisting of electrostatic interactions between the silicate nanodisks and the DNA backbone. The silicate nanodisks were introduced to increase the viscosity of the DNA physical hydrogel and improve their shear-thinning properties. Additionally, the silicate nanodisks were selected to modulate the release capability of the designed network. DNA 4% solutions were heated at 90°C for 45 seconds and cooled down at 37°C degree for two hours. In the second step, the silicate nanodisks suspension in water at different concentrations (0.1 up to 0.5%) were then mixed with the pre-gel DNA hydrogels to obtain the nanocomposite hydrogels. Rheological studies were carried out to investigate the shear thinning properties of the hydrogels. Additionally, the hydrogels were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron microscopy. The hydrogels were loaded with the osteoinductive drug dexamethasone and its release was tested in vitro in phosphate buffer pH 7.4. The drug activity upon release was tested evaluating the osteogenic differentiation of human adipose derived stem cells (hASCs) in vitro through analysis of main osteogenic markers and quantification of alkaline phosphatase activity and calcium deposition. Finally, the hydrogels were tested in vivo and injected into cranial defects in rats to assess their biocompatibility and bone regeneration potential. The inclusion of the silicate nanodisks increased the viscosity of the hydrogels and the best results were obtained with the highest concentration of the nanoclay (0.5%). The hydrogels possessed shear-thinning properties as demonstrated by cyclic strain sweep tests and were able to recover their original storage modulus G' upon removal of strain. Such improvement in the injectable properties of the formulated hydrogels was mainly attributed to the formation of electrostatic interactions between the silicate nanodisks and the phosphate groups of the DNA backbone as confirmed by XPS analysis of the O, N, and P spectra. Additionally, laponite was able to sustain the release of the osteoinductive drug dexamethasone which was instead completely released from the DNA-based hydrogels after a week. The drug after being released was still active and promoted the osteogenic differentiation of hASCs as confirmed by ALP expression and expression of main osteogenic markers including ALP and COLA1. Finally, the gels proved to be biocompatible in vivo when injected into cranial defects and promoted bone formation at the periphery of the defect after a month post-treatment. A novel injectable shear-thinning DNA-based hydrogel was characterized and tested for its drug delivery properties. The hydrogel can promote the sustain release of a small molecule like dexamethasone and be biocompatible in vitro and in vivo. Due to these promising findings, the designed system could find also applicability for the delivery of growth factors or other therapeutic molecules

Acrylic bone cements are used rather extensively in orthopedic and spinal applications. The incorporation of calcium phosphate additives to bone cements, to induce osteoconductivity, have typically resulted in increased cement viscosity, decreased handling, and detrimental effects of the mechanical performance of the cement. Additionally, bioactive bone cements are offered at a premium cost, which limits clinical use of these materials. The goal of this study was to examine and characterize an alternative two-solution poly (methyl Methacrylate) (PMMA) bone cement (referred to as TSBC), after incorporation of several calcium phosphate additives and antimicrobials. These bioactive and antimicrobial two-solution cements were designed to have adjustable properties that meet specific requirements of orthopedic applications. The addition of a bioactive agent would lead to increased levels of bone reformation after surgery, while an antibiotic within the cement would decrease the ability for pathogens to grow in the interface between the bone and new implant. TSBC is a pre-mixed bone cement that exhibits a combination of attractive properties including high strength, adjustable viscosity, adequate exothermal properties, as well as offering the possibility of using the same batch multiple times. The addition of antibiotics has not been previously explored in two-solution bone cements. Therefore, it is desirable to induce antibacterial activity with this formulation. Hydroxyapatite (Ca5(PO4)3(OH)), Brushite (CaHPO4•2H2O), and Tricalcium Phosphate (Ca3(PO4)2)(TCP) were incorporated into the TSBC in varying concentrations (25 and 50 wt%), and the rheological characteristics were examined to verify the feasibility of adding high concentrations of fillers to this cement formulation. Results demonstrated that unlike commercial powder-liquid formulations, calcium phosphate additives in TSBC do not detrimentally affect handling and the rheological properties of the material, while also providing maintenance of cement strength and other physical properties. TSBC material spends a dramatically increased amount of time in the swelling phase, as compared to powder-liquid formulations and thus is better suited to incorporate additives fully into its polymer matrix. Current two-solution bone cements do not contain any osteoconductive or antimicrobial agents. This study investigated the effects of addition of these bioactive agents in the physical and mechanical properties of the cement. Cement porosity was investigated to ensure that the porous nature of the bioactive cement does not damage the mechanical stability of the material. Further imaging will be conducted to demonstrate the improved osteointegration of these bioactive cement with osteoblasts (Figure 1). Degradation studies have been conducted to validate the biodegradable properties of the bioactive components and antibiotics release profile. It is further hypothesized that the degradation time will correlate to the antimicrobial activity. As the cement is replaced with natural bone, more and more antimicrobial will become exposed to the physiologic environment causing a continuous antimicrobial release as the material is partially replaced with new bone over time. Antimicrobial effectiveness and antimicrobial release studies are under-way to illustrate the cements ability to restrict growth at the cement surface, as well as show the antimicrobial release profile over time

Aim. The preparation of antibiotic-containing polymethyl methacrylate (PMMA), as spacers generates a high polymerization heat, which may affect their antibiotic activity; it is desirable to use bone cement with a low polymerization heat. Calcium phosphate cement (CPC) does not generate heat on polymerization, and comparative elution testings are reported that vancomycin (VCM)-containing CPC (VCM-CPC) exceeded the antibiotic elution volume and period of PMMA (VCM-PMMA). Although CPC alone is a weak of mechanical property spacer, the double-layered, PMMA-covered CPC spacer has been created and clinically used in our hospital. In this study, we prepared the double-layered spacers: CPC covered with PMMA and we evaluated its elution concentration, antimicrobial activity and antibacterial capability. Method. We prepared spherical, double-layered, PMMA-coated (CPC+PMMA; 24 g CPC coated with 16 g PMMA and 2 g VCM) and PMMA alone (40 g PMMA with 2 g VCM) spacers (5 each). In order to facilitate VCM elution from the central CPC, we drilled multiple holes into the CPC from the spacer surface. Each spacer was immersed in phosphate buffer (1.5 mL/g of the spacer), and the solvent was changed daily. VCM concentrations were measured on days 1, 3, 7, 14, 28, 56, and 84. Antimicrobial activity against MRSA and MSSA was evaluated by the broth microdilution method. After measuring all the concentration, the spacers were compressed at 5 mm/min and the maximum compressive load up to destruction was measured. Results. The VCM concentration of the CPC+PMMA spacer exceeded that of the PMMA spacer at all-time points; in particular, it was approximately 7.3 times (109.30 vs. 15.03 μg/mL) and approximately 9.1 times (54.47 vs. 6.50 μg/mL) greater on days 14 and 28, respectively. Using the broth microdilution method, we found that the CPC+PMMA spacer had higher antimicrobial activity than the PMMA model. On day 56, the PMMA spacer lost the capability to inhibit bacterial growth, but the CPC+PMMA spacer maintained this ability. The average maximum compressive load for the CPC+PMMA was 7.28 kN, and that of PMMA was 16.21 kN. Conclusions. The CPC+PMMA spacer was superior to PMMA alone in VCM elution volume and duration, so CP- C+PMMA may be effective for the treatment of MRSA and MSSA infection. The double-layered, antibiotic-loaded cement spacer may maintain antibacterial capability and sufficient strength

Bone is a dynamic organ with remarkable regenerative properties seen only otherwise in the liver. However, bone healing requires vascularity, stability, growth factors, a matrix for growth, and viable cells to obtain effective osteosynthesis. We rely on these principles not only to heal fractures, but also achieve healing of benign bone defects. Unfortunately we are regularly confronted with situations where the local environment and tissue is insufficient and we must rely on our “biologic tool box.” When the process of bone repair requires additional assistance, we often look to bone grafting to provide an osteoconductive, osteoinductive, and/or osteogenic environment to promote bone healing and repair. The primary workhorses of bone grafting include autogenous bone, cadaver allograft, and bone graft substitutes. Among the first types of bone graft used and still used in large quantities today include autogenous and cadaver allograft bone. Allografts are useful because it is present in multiple forms that conform to the desired situation. But autogenous bone graft is considered the gold standard because it possesses all the fundamental properties to heal bone. However, it has been associated with high rates of donor site morbidity and typically requires an inpatient hospitalization following the procedure only adding to the associated costs. The first bone graft substitute use was calcium sulfate in 1892, and over the past 122 years advancements have achieved improved material properties of calcium sulfate and helped usher in additional bioceramics for bone grafting. Today there are predominantly four types of bioceramics available, which include calcium sulfate, calcium phosphate, tricalcium phosphate, and coralline hydroxyapatite. They come in multiple forms ranging from pellets and solid blocks to injectable and moldable putty. In comparison to autogenous bone graft, the primary limitation of bioceramics are the lack of osteogenic and osteoinductive properties. Bioceramics work by creating an osteoconductive scaffold to promote osteosynthesis. The options of bone graft substitutes don't end with these four types of bioceramics. Composite bioceramics take advantage of the differing biomechanical properties of these four basis types of bioceramics to develop improved materials. To overcome the lack of osteoinductive and osteogenic properties growth factors or bone marrow aspirate can be added to the bioceramic. As a result, the list of combinations available in our “biologic tool box” continues to expand. More than 20 BMPs have been identified, but only BMP-2 and BMP-7 have FDA approval. As we look forward to areas of future research and need within orthobiologics, some will likely come in the near future while others are much further in the future. We will continue to strive for the ideal bone graft substitute, which will have similar osteoinductive properties as autograft. The ultimate bone graft substitute will likely involve stem cells because it will allow an alternative to autogenous bone with the same osteogenic potential

Aim. To evaluate bacterial adhesion and biofilm formation to metallic cerclage wire versus polymer cerclage system (SuperCable®). Methods. Experimental in vitro study to evaluate quantitative bacterial adherence to different cerclage wire materials. Two types of cerclage wires were compared: a metallic versus a polymer based wire (SuperCable®). A two-centimeter cerclage wire piece of each material was included in 2 mL of tryptic soy broth (TSB) culture media, inoculated with 10 microliters of a 0.5 McFarland of a Staphylococcus epidermidis strain and cultivated at 37°C during 2h for adhesion and 48h for biofilm formation. After this time, the cerclages were washed using a 1% phosphate buffered saline (PBS) and sonicated in new culture medium. After sonication, dilutions of each culture were spread in TSB agar and incubated 37°C during 24h. The number of colonies were counted and the cfu/cm2 was calculated. Results. There were no differences in the number of colonies counted at 2 hours. At 48 hours, the polymer cerclage system showed a clinically and statistically reduction of 95.2% in the biofilm formation of S. epidermidis. The highest bacterial counts were observed in metallic cerclages after 48h. Conclusion. In in vitro conditions, the polymer cerclage system may offer decreased biofilm formation compared with metallic cerclage wires. However, there are many other factors in in vivo conditions that could play a role in bacterial adhesion to cerclage wires. Further research is needed in order to recommend the use of polymer cerclage systems for septic revision surgery

Bone is a dynamic organ with remarkable regenerative properties seen only otherwise in the liver. However, bone healing requires vascularity, stability, growth factors, a matrix for growth, and viable cells to obtain effective osteosynthesis. We rely on these principles not only to heal fractures, but also achieve healing of benign bone defects. Unfortunately, we are regularly confronted with situations where the local environment and tissue is insufficient and we must rely on our “biologic tool box.” When the process of bone repair requires additional assistance, we often look to bone grafting to provide an osteoconductive, osteoinductive, and/or osteogenic environment to promote bone healing and repair. The primary workhorses of bone grafting includes autogenous bone, cadaver allograft, and bone graft substitutes. Among the first types of bone graft used and still used in large quantities today include autogenous and cadaver allograft bone. Allografts are useful because it is present in multiple forms that conform to the desired situation. But autogenous bone graft is considered the gold standard because it possesses all the fundamental properties to heal bone. However, it has been associated with high rates of donor site morbidity and typically requires an inpatient hospitalization following the procedure only adding to the associated costs. The first bone graft substitute use was calcium sulfate in 1892, and over the past 122 years advancements have achieved improved material properties of calcium sulfate and helped usher in additional bioceramics for bone grafting. Today there are predominantly 4 types of bioceramics available, which include calcium sulfate, calcium phosphate, tricalcium phosphate, and coralline hydroxyapatite. They come in multiple forms ranging from pellets and solid blocks to injectable and moldable putty. In comparison to autogenous bone graft, the primary limitation of bioceramics are the lack of osteogenic and osteoinductive properties. Bioceramics work by creating an osteoconductive scaffold to promote osteosynthesis. The options of bone graft substitutes don't end with these four types of bioceramics. Composite bioceramics take advantage of the differing biomechanical properties of these four basis types of bioceramics to develop improved materials. To overcome the lack of osteoinductive and osteogenic properties growth factors or bone marrow aspirate can be added to the bioceramic. As a result, the list of combinations available in our “biologic tool box” continues to expand. More than 20 BMPs have been identified, but only BMP-2 and BMP-7 have FDA approval. As we look forward to areas of future research and need within orthobiologics, some will likely come in the near future while others are much further in the future. We will continue to strive for the ideal bone graft substitute, which will have similar osteoinductive properties as autograft. The ultimate bone graft substitute will likely involve stem cells because it will allow an alternative to autogenous bone with the same osteogenic potential

The purpose of this study was to quantify tibial tunnel enlargement at 3-, 6- and 12-months post-anterior cruciate ligament reconstruction (ACLR), and evaluate the magnitude of tunnel widening with use of a Poly (L-lactic Acid) interference screw (PLLA (Bioscrew XtraLok, Conmed, New York)) compared to a Poly (L-lactic Acid) + tricalcium phosphate interference screw (PLLA+TCP (GENESYS Matryx screw comprised of microTCP and 96L/4D PLA, Conmed, New York)). This was a prospective randomized controlled trial with two parallel groups. Eighty unilateral ACL-deficient participants awaiting ACLR surgery were recruited between 2013 and 2017 from the clinic of a sole fellowship trained orthopaedic surgeon. Patients had to be skeletally mature and less than 45 years old, with no concomitant knee ligament injuries requiring surgery, chondromalacia, or previous history of ipsilateral knee joint pathology, surgery or trauma to the knee. Participants were randomized intra-operatively into either the PLLA or PLLA+TCP tibial interference screw fixation group. Study time points were pre-, 3-, 6-, and 12-months post ACLR. Participants underwent x-rays with a 25 mm calibration ball, IKDC knee assessment, and completed the ACL-Quality of Life score (ACL-QOL) at each visit. Measurement (mm) of the most proximal and distal extents as well as the widest point of the tibial tunnel were taken using efilm (IBM Watson Health) and were standardized relative to the calibration ball. A contrast inverter was used to determine clear borders based on contrast between normal and drilled bone. In addition, a subjective evaluation of the tunnel was conducted looking for bowing of the borders of the tunnel or change in tunnel shape, categorizing the tunnel as widened or not widened. Differences between groups at each time point were evaluated using independent t-tests corrected for multiple comparisons. Tunnel width was also compared as a percentage of actual screw size at 12-months post-operative. Categorical data were compared using Fisher's Exact Test. Forty participants were randomized to each group with mean age (SD) of 29.7 (7.6) and 29.8 (9.1), for PLLA and PLLA+TCP, respectively. There were no differences between groups in age, gender or ACL-QOL. There were no differences found between groups at any time point in either tunnel width measurements or tunnel width as a percentage of actual screw size. The greatest difference between groups was noted in the measurement of the widest point on lateral x-ray view with a mean difference of 11%. Based on subjective evaluation of tunnel shape, three participants had visible widening in the PLLA group, and two in the PLLA+TCP group (p=NS). No differences in tunnel widening were identified between ACL reconstruction patients using a PLLA interference screw compared to a PLLA+TCP screw for tibial fixation up to 12-months post-operative

Joint hemiarthroplasty replaces one side of a synovial joint and is a viable alternative to total joint arthroplasty when one side of the joint remains healthy. Most hemiarthroplasty implants used in current clinical practice are made from stiff materials such as cobalt chrome or ceramic. The substitution of one side of a soft cartilage-on-cartilage articulation with a rigid implant often leads to damage of the opposing articular cartilage due to the resulting reductions in contact area and increases in cartilage stress. The improvement of post-operative hemiarthroplasty articular contact mechanics is of importance in advancing the performance and longevity of hemiarthroplasty. The purpose of the present study was to investigate the effect of hemiarthroplasty surface compliance on early in-vitro cartilage wear and joint contact mechanics. Cartilage wear tests were conducted using a six-station pin-on-plate apparatus. Pins were manufactured to have a hemispherical radius of curvature of 4.7 mm using either Bionate (DSM Biomedical) having varying compliances (80A [E=20MPa], 55D [E=35MPa], 75D [E=222MPa], n=6 for each), or ceramic (E=310GPa, n=5). Cartilage plugs were cored from fresh unfrozen bovine knee joints using a 20 mm hole saw and mounted in lubricant-containing chambers, with alpha calf serum diluted with phosphate buffer solution to a protein concentration of 17 g/L. The pins were loaded to 30N and given a stroke length of 10 mm for a total of 50,000 cycles at 1.2 Hz. Volumetric cartilage wear was assessed by comparing three-dimensional cartilage scans before and during wear testing. A two-way ANOVA was used for statistical analysis. To assess hemiarthroplasty joint contact mechanics, 3D finite element modelling (ABAQUS v6.12) was used to replicate the wear testing conditions. Cartilage was modeled using neo-Hookean hyper-elastic material properties. Contact area and peak contact stress were estimated. The more compliant Bionate 80A and 55D pins produced significantly less volumetric cartilage wear compared with the less compliant Bionate 75D and ceramic pins (p 0.05). In terms of joint contact mechanics, the more compliant materials (Bionate 80A and 55D) had significantly lower maximum contact stress levels compared to the less compliant Bionate 75D and ceramic pins (p < 0 .05). The results of this study show a relationship between hemiarthroplasty implant surface compliance and early in vitro cartilage wear, where the more compliant surfaces produced significantly lower amounts of cartilage wear. The results of the joint contact mechanics analysis showed that the more compliant hemiarthroplasty materials produced lower maximum cartilage contact stresses than the less compliant materials, likely related to the differences in wear observed. More compliant hemiarthroplasty surfaces may have the potential to improve post-operative cartilage contact mechanics by increasing the implant-cartilage contact area while reducing peak contact stress at the implant-cartilage interface, however, such materials must be resistant to surface fatigue and longer-term cartilage wear/damage must be assessed

As the intervertebral disc is largely avascular, needle injection is the most practical method for delivery of therapeutic agents used in treatments for degenerative disc disease. Intradiscal pressure increases during injection, and insufficient recovery time prior to needle retraction may result in injectate leakage. In order to determine the maximum pressure and post-injection recovery time for a given injection volume and rate, an analytical model of intradiscal injection was developed and calibrated experimentally. A governing equation was derived defining intradiscal pressure as a function of effective permeability, initial elastic stiffness, nonlinear stiffness term, and injection rate. The equation was solved using a fourth order Runge-Kutta routine with a 0.05s time step and a ramp-dwell injection. The model was calibrated by performing controlled intradiscal injections on five bovine caudal intervertebral discs. Three had adjacent vertebrae intact, while two were separated from vertebrae and constrained between porous stainless steel platens. A syringe driven by a linear actuator was used to inject phosphate buffered saline through a 21g hypodermic needle inserted radially into the disc to a depth of one half of the disc diameter. Injection was performed at a rate of 75μL/s to a volume of 250μL followed by a 240s dwell. Fluid pressure was recorded during both the injection phase and subsequent recovery phase. For each experimental pressure vs time trace, model parameters were varied in order to obtain an optimal fit. The model was run with the average parameter values across a grid of possible injection protocols, with injection volume ranging from 30 to 300μL and injection time ranging from 0.1 to 5s. For each case, peak pressure and time required to reach a 1kPa threshold were recorded. Experimentally measured peak pressure ranged from 68 to 88kPa. Pressure at the end of the 240s dwell ranged from 49 to 69kPa. There was no apparent difference between discs with and without endplates. Leakage of fluid following needle retraction was observed in all specimens. Experimental data were well fit by the analytical model, which predicted higher peak pressure and longer recovery time with increasing volume, from approximately 1500s at 30μL to nearly 3000s at 300μL. The model was nearly insensitive to injection rate. The experimental data confirm pressurization of the disc during injection and injectate leakage resulting from insufficient recovery time. The model predicts that the time required to recover to below threshold leakage pressure is impractically long for both laboratory and clinical injection protocols. Similar behavior with and without endplates confirms that fluid flow is limited by permeability of the tissue itself, not the boundary conditions. Slow recovery is likely attributable to the fact that peak injection pressures were lower than the hydraulic swelling pressure of the nucleus pulposus, which has been reported to be approximately 140kPa. Due to the high swelling pressure of the nucleus pulposus, it is unlikely that intradiscal injection procedures can be performed without substantial injectate leakage following needle retraction

Summary. We report the first use of synchrotron xray spectroscopy to characterize and compare the chemical form and distribution of metals found in tissues surrounding patients with metal-on-metal hip replacements that failed with (Ultima hips) or without (current generation, large diameter hips) corrosion. Introduction. The commonest clinical category of failure of metal-on-metal (MOM) hip replacements is “unexplained” and commonly involved a soft tissue inflammatory response. The mechanism of failure of the Ultima MOM total hip replacement includes severe corrosion of the metal stem and was severe enough to be removed from clinical use. Corrosion is not a feature that we have found in the currently used MOM bearings. To better understand the biological response to MOM wear debris we hypothesized that tissue from failed hips with implant corrosion contained a different type of metal species when compared to those without corrosion. Method. Tissue from patients with two types of MOM hip arthroplasty were analysed: Ultima that failed with severely corroded femoral stems (n=12); and large diameter, current generation MOM hips that failed without visible corrosion (n=7). Comparison was also made to samples of cobalt, chromium and molybedanum standards. We used a high energy synchrotron xray beam to map and characterise the type of metal within the tissues. This enabled us to analyse the type of chemical in a situation that is as realistic as possible: without staining; without the use of a vacuum; and the use of fresh frozen tissue sections with metals at relatively low concentrations. This could not have been achieved without a synchrotron. Results. Comparison with standards revealed the chemical form of the chromium in the tissues surrounding metal-on-metal hip replacements was chromium (III). This was similar for both corroded (Ultima MOM) and non-corroded (large diameter, current generation MOM) hips. This was chromium (III) phosphate in the non-corroded hips but because the concentration of chromium was lower in the corroded hips it was difficult to differentiate chromium phosphate from oxide. There was some evidence of localistaion of cobalt and chromium, both in metallic form. One sample from corroded hips contained chromium (VI). Conclusion. Chromium (III) phosphate was the predominant metallic species in the tissues surrounding metal-on-metal hip replacements. This may have arisen from corrosion, wear or a combination of both

Introduction. Since the introduction of modular hip taper junctions, corrosion has been studied yet the clinical effect remains unclear. Mechanically assisted corrosion and crevice corrosion are thought to be the primary clinical processes driving taper corrosion. Like all corrosion reactions, these processes require the taper junction to be in contact with an electrolyte. This study investigates the effect of sealing the taper junction from the environment on the mechanically-induced corrosion of a modular hip taper junction. Methods. A short-term corrosion fatigue test was conducted with Ti6Al4V 12/14 taper coupons coupled with CoCrMo 12/14 taper 28mm+12 heads (DePuy Synthes, Warsaw, IN). Ten specimens were assembled with a 1.1 kN press load and sealed with silicone sealant (Dow-Corning 732 Multi-Purpose Sealant). Prior to assembly five of these specimens were assembled with the taper junction having been wetted with phosphate buffered saline before assembly; the rest were assembled dry. Specimens were then immersed in phosphate buffered saline and a potentiostat was used to maintain the potential of the specimen at −50mV vs. Ag/AgCl. Incrementally larger loads were applied to the head of the specimen until a 4000N maximum load was reached. The average currents generated during this test was used to assess the corrosion performance of the specimens. The data from the sealed specimens was compared to a control group, which were wetted before assembly but not sealed. Results. In all cases the corrosion of the sealed specimens did not appear to increase in response to the cyclic load; throughout the test, the corrosion did not increase over the baseline anodic current of roughly 0.25 μA. In contrast, the unsealed controls experienced average corrosion currents of around 5 μA at the maximum load, and an average current of 2.0±0.93 µA over the entire test. The wet and dry sealed assembly specimens both resulted in significantly lower average currents of 0.24±0.09 µA and 0.25±0.09 µA, respectively. Discussion. Test specimens with sealed taper junctions to prevent fluid and ion ingress and egress resulted in no measurably increased corrosion currents compared to the baseline currents in the ambient fluid. The wetted sealed specimens might possibly be subject to corrosion; however the corrosion process and effects in this case may be isolated within the taper junction. This test indicates mechanically assisted corrosion does not occur if the taper junction is not exposed to an electrolyte. Significance. This study demonstrates that mechanically induced corrosion can be greatly reduced or prevented by sealing the taper junction to prevent the ingress of electrolyte

The progressive kyphosis and pain in patients with acute thoracolumbar burst fractures treated conservatively so as the recurrent kyphosis after posterior reduction and fixation were associated to disc collapse rather than vertebral body compression. It depends on redistribution of the disc tissue in the changed morphology of the space after fractures of the endplate. The aim of this study is to evaluate the safety and the efficacy of balloon kyphoplasty with calcium phosphate, alone or associated to short posterior instrumentation, in the treatment of acute thoracolumbar burst fractures. Eleven fractures in ten consecutive patients with an average age of 48 years who sustained acute thoracolumbar traumatic burst fractures without neurological deficits were included in this study. The fractures were A1.2 (3), A3.1 (4) and A3.2 (4), according to AO classification. In 7 fractures (A1.2 and A3.1) the kyphopasty was performed alone in order to make the most of efficacy in fracture reduction, anterior and medium column stabilization and, as much as possible, segmental kyphosis correction. In the A3.2 fractures (4), that are unstable, the kyphoplasty was associated to a short posterior instrumentation. To avoid the PMMA long run complications in younger patients, we used a calcium phosphate cement. VAS, SF-36, Roland-Morris questionnaire (RMQ) and Oswestry low back pain disability questionnaire (ODQ) were used to evaluate pain, state of health, functional outcomes and spine disability. To the average follow-up time of 15.5 months (range 8–31) we did not observe statistically significant differences in 7 of 8 SF-36 domains in comparison to general healthy population of same sex and age. At the same follow-up, the spine disability questionnaire showed a functional restriction of 18% (ODQ) and 29,6% (RMQ) being 100% the maximum of disability. No bone cement leakage, no implant failure and no height correction loss were observed in any case. Our data confirm the safety and the efficacy of ballon kyphoplasty with calcium phosphate in the treatment of acute thoracolumbar burst fractures. In this way we can reduce the possible complications resulted from discal space collapse and obtain an early functional restoration. When performed alone, this mini invasive surgical technique offer the advantage of almost immediate return to daily activities. When associated to posterior instrumentation, it decreases the long run complications and allows to reduce the number of stabilized levels, maintaining, in part, the thoracolumbar junction movement

Trabecular bone is a multiscale hierarchical composite material that is known to display time-dependant properties. However, most biomechanical models treat this material as time independent. Time-dependant properties, such as creep and relaxation, are thought to play an important role in many clinically relevant orthopaedic issues: implant loosening, vertebral collapse, and non-traumatic fractures. In this study compressive multiple-load-creep-unload-recovery (MLCUR) tests were applied to human trabecular bone specimens. 15 female femoral heads were harvested, with full ethical approval and patient consent, at the time of total hip replacement. Central cores were extracted and cut parallel under constant irrigation. Specimens were embedded in end caps using surgical cement, an epoxy tube was secured around the end caps and filled with phosphate buffered saline (PBS) to ensure the specimens remained hydrated throughout. Embedded samples were scanned by microCT (SkyScan 1172, Bruker) at a resolution of 17µm to determine microarchitecture. Bone volume fraction (BVF) was used to represent microarchitecture. Specimens had an effective length of 16.37mm (±1.90SD) with diameter of 8.08mm (±0.05SD), and BVF of 19.22% (±5.61SD). The compressive MLCUR tests were conducted at 5 strain levels, 2000µε, 4000µε, 6000µε, 8000µε and 10000µε. At each strain level, the load required to maintain each strain was held for 200s (creep) then unloaded to 1N for 600s (recovery). The instantaneous, creep, unloading and recovered strains can be easily obtained from the strain-time curves. Stress-strain plots revealed the Young's modulus. Data was modelled using line of best fit with appropriate curve fitting. R2 values were used to indicate association. Mechanical testing demonstrated the expected time independent relationship between BVF and stiffness: higher stiffness was found for specimen with higher BVF and this was consistent for all strain levels. Creep strain was found to depend on instantaneous strain and BVF. At low levels of instantaneous strain, there was a greater amount of creep strain in low BVF samples (R2 = 0.524). This relationship was no longer apparent at higher strain levels (R2 = 0.058). Residual strain also depended on the applied instantaneous strain and BVF: at low levels of strain, residual strain was similar with all BVF (R2 = 0.108) and at high levels of strain, residual strain was greater in low BVF samples (R2 = 0.319). The amount of instantaneous strain applied to each sample is constant, variations in stiffness result in different applied loads. In low BVF bone, the stiffness is also low, therefore the stress required to reach designed strain is also lower: yet, there is more creep and less recovery. We have demonstrated that even at loads below recognised yield levels, time-dependence affects the mechanical response and residual strain is present. In cases of low BVF, deflection due to creep, and increased irrecoverable strain could have clinically relevant consequences, such as implant loosening and vertebral collapse. The role of time-dependant properties of bone is seldom considered. This data could be developed into a constitutive model allowing these time-dependant behaviours to be incorporated in finite element modelling, leading to better predictions of implant loosening, especially for lower quality bone

Bone is a dynamic organ with remarkable regenerative properties seen only otherwise in the liver. However, bone healing requires vascularity, stability, growth factors, a matrix for growth, and viable cells to obtain effective osteosynthesis. We rely on these principles not only to heal fractures, but also achieve healing of benign bone defects. Unfortunately we are regularly confronted with situations where the local environment and tissue is insufficient and we must rely on our “biologic tool box.” When the process of bone repair requires additional assistance, we often look to bone grafting to provide an osteoconductive, osteoinductive, and/or osteogenic environment to promote bone healing and repair. The primary workhorses of bone grafting include autogenous bone, cadaver allograft, and bone graft substitutes. Among the first types of bone graft used and still used in large quantities today include autogenous and cadaver allograft bone. Allografts are useful because it is present in multiple forms that conform to the desired situation. But autogenous bone graft is considered the gold standard because it possesses all the fundamental properties to heal bone. However, it has been associated with high rates of donor site morbidity and typically requires an inpatient hospitalization following the procedure only adding to the associated costs. The first bone graft substitute use was calcium sulfate in 1892, and over the past 122 years advancements have achieved improved material properties of calcium sulfate and helped usher in additional bioceramics for bone grafting. Today there are predominantly 4 types of bioceramics available, which include calcium sulfate, calcium phosphate, tricalcium phosphate, and coralline hydroxyapatite. They come in multiple forms ranging from pellets and solid blocks to injectable and moldable putty. In comparison to autogenous bone graft, the primary limitation of bioceramics are the lack of osteogenic and osteoinductive properties. Bioceramics work by creating an osteoconductive scaffold to promote osteosynthesis. The options of bone graft substitutes don't end with these four types of bioceramics. Composite bioceramics take advantage of the differing biomechanical properties of these four basis types of bioceramics to develop improved materials. To overcome the lack of osteoinductive and osteogenic properties growth factors or bone marrow aspirate can be added to the bioceramic. As a result, the list of combinations available in our “biologic tool box” continues to expand. More than 20 BMPs have been identified, but only BMP-2 and BMP-7 have FDA approval. As we look forward to areas of future research and need within orthobiologics, some will likely come in the near future while others are much further in the future. We will continue to strive for the ideal bone graft substitute, which will have similar osteoinductive properties as autograft. The ultimate bone graft substitute will likely involve stem cells because it will allow an alternative to autogenous bone with the same osteogenic potential

Bone is a dynamic organ with remarkable regenerative properties seen only otherwise in the liver. However, bone healing requires vascularity, stability, growth factors, a matrix for growth, and viable cells to obtain effective osteosynthesis. We rely on these principles not only to heal fractures, but also achieve healing of benign bone defects. Unfortunately, we are regularly confronted with situations where the local environment and tissue is insufficient and we must rely on our “biologic tool box.” When the process of bone repair requires additional assistance, we often look to bone grafting to provide an osteoconductive, osteoinductive, and/or osteogenic environment to promote bone healing and repair. The primary workhorses of bone grafting include autogenous bone, cadaver allograft, and bone graft substitutes. Among the first types of bone graft used and still used in large quantities today include autogenous and cadaver allograft bone. Allografts are useful because they are present in multiple forms that conform to the desired situation. But autogenous bone graft is considered the gold standard because it possesses all the fundamental properties to heal bone. However, it has been associated with high rates of donor site morbidity and typically requires an inpatient hospitalization following the procedure only adding to the associated costs. The first bone graft substitute used was calcium sulfate in 1892, and over the past 122 years advancements have achieved improved material properties of calcium sulfate and helped usher in additional bioceramics for bone grafting. Today there are predominantly four types of bioceramics available, which include calcium sulfate, calcium phosphate, tricalcium phosphate, and coralline hydroxyapatite. They come in multiple forms ranging from pellets and solid blocks to injectable and moldable putty. In comparison to autogenous bone graft, the primary limitation of bioceramics are the lack of osteogenic and osteoinductive properties. Bioceramics work by creating an osteoconductive scaffold to promote osteosynthesis. The options of bone graft substitutes don't end with these four types of bioceramics. Composite bioceramics take advantage of the differing biomechanical properties of these four basis types of bioceramics to develop improved materials. To overcome the lack of osteoinductive and osteogenic properties growth factors or bone marrow aspirate can be added to the bioceramic. As a result, the list of combinations available in our “biologic tool box” continues to expand. More than 20 BMPs have been identified, but only BMP-2 and BMP-7 have FDA approval. As we look forward to areas of future research and need within orthobiologics, some will likely come in the near future while others are much further in the future. We will continue to strive for the ideal bone graft substitute, which will have similar osteoinductive properties as autograft. The ultimate bone graft substitute will likely involve stem cells because it will allow an alternative to autogenous bone with the same osteogenic potential