Orthopaedic soft tissues, such as tendons, ligaments, and articular cartilage, rely on their unique collagen fiber architectures for proper functionality. When these structures are disrupted in disease or fail to regenerate in engineered tissues, the tissues transform into dysfunctional fibrous tissues. Unfortunately, collagen synthesis in regenerating tissues is often slow, and in some cases, collagen fibers do not regenerate naturally after injury, limiting repair options. One of the research focuses of my team is to develop functional fiber replacements that can promote in vivo repair of musculoskeletal tissues throughout the body. In this presentation, I will discuss our recent advancements in electrowriting 3D printing of natural polymers for creating functional fiber replacements. This manufacturing process utilizes electrical signals to control the flow of polymeric materials through an extrusion nozzle, enabling precise deposition of polymeric fibers with sizes that cannot be achieved using conventional extrusion printing methods. Furthermore, it allows for the formation of fiber organizations that surpass the capabilities of conventional electrospinning processes. During the presentation, I will showcase examples of electrowritten microfiber scaffolds using various naturally-derived polymers, such as gelatin (a denatured form of collagen) and silk fibroin. I will discuss the functional properties of silk-based scaffolds and highlight how they exhibit restored β-sheet and α-helix structures [1]. This restoration results in an elastic response of up to 20% deformation and the ability to withstand cyclic loading without plastic deformation. Additionally, I will present our latest results on the compatibility of this technique with patterning cell-laden fiber structures [2]. This novel biofabrication process allows for the printing of biomimetic microscale architectures with high cell viability, and offers a promising approach to understanding how shear and elongation forces influence cell development of hierarchical (collagen) fibers. Acknowledgements: The author would like to thank the Reprint project (OCENW.XS5.161) and the program “Materials Driven Regeneration” (024.003.013) by the Netherlands Organization for Scientific Research for the financial support

Introduction and Objective. Regeneration of cartilage injuries is greatly limited. Therefore, cartilage injuries are often the starting point for later osteoarthritis. In the past, various bioactive glass (BG) scaffolds have been developed to promote bone healing. Due to the fact that they induce the deposition of hydroxyapatite (HA) -the main component of bone matrix, these BG types are not suitable for chondrogenesis. Hence, a novel BG (Car12N) lacking HA formation, was established. Since BG are generally brittle the combination with polymers is helpful to achieve suitable biomechanic stability. The aim of this interdisciplinary project was to investigate the effects of biodegradable polymer Poly(D,L-lactide-co-glycolide) (PLLA) infiltration into a Car12N scaffold for cartilage tissue engineering. Materials and Methods. BG scaffolds were infiltrated with PLLA using phase separation within a solvent. Pure BG Car12N scaffolds served as control. To assess whether the polymer was homogeneously distributed the polymer to glass ratio and pore contents in the upper, middle and lower third of the scaffolds were examined by light microscopy. For a more precise characterization of the scaffold topology, the glass strut length, the glass strut diameter and the pore circumference were also measured. Leaching tests in 0.1M HCl solution over 8 days were used to allow a gel layer formation on the scaffolds surface. Non-leached and leached scaffolds were subjected to strength testing. Cytotoxicity of the scaffolds with and without polymer was tested according to standards. Scaffolds were colonized with 27.777.8 per cm. 3. primary porcine articular chondrocytes (pACs) or primary human mesenchymal stromal cells (hMSCs), respectively. After cultivation for up to 35 days, the vitality, quantitative DNA and sulfated glycosaminoglycan (sGAG) contents per scaffold were determined. Results. The polymer distribution was not homogeneous in the scaffolds. There were significant differences in glass strut length and pore size. Leaching increased the biomechanical strength. All scaffolds were not cytotoxic. pACs and hMSCs were able to adhere to the scaffold with and without polymer and remained viable during the whole culturing period of 35 d. The DNA content was higher in the pAC colonized scaffolds with polymer than without polymer. The sGAG content was higher in hMSCs seeded scaffolds with polymer than in pACs seeded ones with polymer. Conclusions. Polymer infiltration leads to an increase in mechanical stability of Car12N scaffolds and chondrogenic cells are able to colonize these composites suggesting them as a promising

Introduction. The incidences of fragility fractures, often because of osteoporosis, are increasing. Research has moved towards bioresorbable scaffolds that provide temporary mechanical stability and promote osteogenesis. This research aims to fabricate a 3D printed composite Poly (l-lactic-co-glycolic acid)-strontium doped tricalcium phosphate (PLGA-SrTCP) scaffold and evaluate in an in vitro co culture study containing osteoporotic donor cells. Method. PLGA, PLGA TCP, and PLGA SrTCP scaffolds were produced using Fused Filament Fabrication (FFF). A four-group 35-day cell culture study was carried out using human bone marrow derived mesenchymal stem cells (hMSCs) from osteoporotic and control donors (monoculture) and hMSCs & human monocytes (hMCs) (Co culture). Outcome measures were biochemical assays, PCR, and cell imaging. Cells were cultured on scaffolds that had been pre-degraded for six weeks at 47°C prior to drying and gamma sterilisation. Result. 3D printed scaffolds were successfully produced by FFF. All groups in the study supported cell attachment onto the scaffolds, producing extracellular matrices as well as evidence of osteoclast cell structures. Osteoporotic cells increased CTSK activity and CAII activity and decreased ALP activity compared to controls. In control cultures, the addition of bTCP and bTCP/Sr to the PLGA reduced TRAP5b, CAII and ALP activity compared to PLGA alone. The addition of Sr did not show any differences between donors. Conclusion. This study details suitability of 3D printed polymer scaffolds for use in bone tissue applications. Both composite and pure polymer scaffolds promote osteogenesis in vitro. The introduction of ceramic filler and ion doping does not beneficially effect osteogenic potential and can reduce its ability compared to pure polymer. This study suggests the behaviour of control and osteoporotic cells are different and that osteoporotic cells are more prone to bone resorption. Therefore, it is important to design bone scaffolds that are specific to the patient as well as to the region of fracture

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

Introduction: Acrylic bone cement (ABC) manufacturers vary their products by using different proportions of the principle ingredients to optimize handling time or mechanical properties. There is limited research showing the effect that varying the monomer to polymer ratio (independent from other constituents) has on thermal and mechanical properties of ABC. Materials and Methods: The formula for CMW1 (DePuy) was reproduced using original ingredients obtained separately from different suppliers. The commercially available CMW1 monomer/polymer ratio is approximately (0.6 ml/gm). Six variants of CMW1 bone cement were prepared with varying monomer/polymer ratio (0.4–1 ml/gm). The specimens were cured and aged in an incubator for 7 days at 37°C. Thermal characteristics of the polymerization reaction such as maximum polymerization reaction temperature (Tmax) and setting time (ts) were recorded using a Picolog digital data recorder. Compressive mechanical properties (Young’s modulus and yield stress) were measured using a TestexpertII Universal Testing System from Zwick Roell implementing ISO5833 test criteria. SPSS 14 for Windows software was used for calculating statistics and data analysis. Results: An increase in monomer/polymer ratio was associated with a significant (p= 0.00) increase in setting time (5.3–11.3 minutes) with a strong correlation (r2=0.988). However, there seemed to be no effect on Tmax (p=0.792). Compression tests showed a significant (p=0.022) decrease in E-modulus (2.63 to 2.22 GPa) with a strong Pearson correlation negative coefficient (r2= −0.827). Similarly, yield compressive stress showed a significant (p=0.002) decrease (121.83–101.19 MPa) with a strong negative correlation (r2= −0.93). Conclusion: This experimental study shows that varying the ratio of monomer to polymer independently from other constituents in acrylic bone cement significantly affects setting time and compressive mechanical properties. Setting time can be prolonged to increase handling time; however this will occur at the expense of a reduction in compressive stiffness and strength

Introduction. Stress shielding and wear induced aseptic loosening cause failure in total joint arthroplasty. To improve long-term outcomes in total knee arthroplasty (TKA), the use of a low modulus, low wearing biomaterial may be a suitable alternative to cobalt chromium (CoCr) femoral components. Based on its favorable mechanical properties and observed clinical success especially in spinal surgery, polyetheretherketone (PEEK) is investigated as a candidate material for a metal free TKA. An all polymer TKA has several theoretical advantages, these include a more physiological stress in the distal femur, elimination of biological reaction to metal, better radiographic visualisation of the bone implant interface especially with CT and MRI. In addition, polymers afford a cheaper option for the manufacture of prostheses. Aims and Hypothesis. This study investigated the wear performance of PEEK and carbon reinforced PEEK (CFR-PEEK) as bearing materials in an all polymer TKA using a unidirectional pin on plate test. Our hypothesis was that reduced wear is generated from PEEK or CFR-PEEK bearings when compared with metal on polyethylene (MoP) bearings and that this combination may provide a suitable alternative in TKA. Methods. A validated modification of ASTM F7321 was used as test protocol. Twenty millimeter diameter spherically ended pins with a radius of 25mm were articulated against 40mm diameter plates. A load of 1000N was applied to generate an initial contact stress of ∼70MPa similar to high contact stresses previously reported in non congruent knee designs2. Ten material combinations were tested as shown in Table 1. Table 1: Tribological couples tested (Pin vs. Plate) UHMWPE – ultrahigh molecular weight polyethylene, XLPE – highly cross-linked polyethylene). The lubricant used was 25% newborn calf serum containing 0.3% sodium azide to retard bacteria growth and 20mM EDTA to prevent calcium deposition. Three repeats of pin on plate combinations (including 2 passive soak controls) were tested for 2 million cycles at a cycle frequency of 1Hz and a cycle length of 20 mm. Gravimetric wear was analysed every 250,000 cycles and results converted to volumetric wear using material density. Results. All CFR-PEEK articulations were stopped due to excessive wear of the counter-surfaces. Results showed a linear wear rate of UHMWPE and XLPE plates over the test period. PEEK vs. XLPE showed similar wear rates to metal on polyethylene (MoP)bearings (Fig 1). Conclusion. At high stresses representative of non conforming knee designs, PEEK pins articulated against XLPE plates generated volumetric wear similar to that noted in MoP bearings. From these results, it may be possible to replace CoCr in TKR with PEEK which may be beneficial because of the low elastic modulus and elimination of biological activity to metal alloy

Introduction: Acrylic bone cement (ABC) manufacturers vary their products by using different proportions of the principle ingredients to optimise handling time or mechanical properties. Surprisingly, there is limited research showing the effect of varying monomer/polymer and initiator/activator ratios (independent from other constituents) on thermal and mechanical properties of ABC. Materials and Methods: The formula for CMW (DePuy) was reproduced using original ingredients obtained from different suppliers. The commercially available CMW monomer/polymer ratio is approximately (0.6 ml/gm). Six variants of CMW bone cement were prepared by varying the monomer/polymer ratio (0.4–1 ml/gm) and eight variants were prepared by varying the initiator/activator BPO/DMPT ratio (1.71–11.25). Specimens were stored in an incubator for 7 days at 37 °C. Thermal characteristics of the polymerisation reaction such as maximum polymerisation reaction temperature (Tmax) and setting time (Ts) were recorded using a thermocouple and Picolog digital data recorder. Compressive mechanical properties were measured using Zwick Roell All Round Testing System implementing ISO5833 recommendations. SPSS software was used to perform ANOVA and calculate Pearson correlation coefficient. Results: Increasing monomer/polymer ratio resulted in prolongation of setting time (5.3–11.3 minutes) displaying a significant (p= 0.000) correlation (r=0.988); however, there was no significant correlation with Tmax (r=−0.123, p=0.792). Increasing the monomer/polymer ratio resulted in a significant reduction in yielding compressive strength (F=110.97, p=0.000) and modulus (F=16.1, p=0.000). Pearson correlation test showed that monomer/polymer ratio had a significant correlation with yielding compressive strength (r= −0.930, p=0.002) and a significant correlation with the corresponding modulus of elasticity (r= −0.827, p=0.022). An increase in the BPO/DMPT ratio did not display a significant (p= 0.172) correlation (r=−0.535) with Tmax; however, the setting time was prolonged by increasing the BPO/ DMPT ratio with a significant (p=0.002) strong positive correlation (r=0.903). Compression tests showed a significant (F=13.45, p=0.000) reduction in yielding compressive strength with a significant (p=0.04) inverse (r=−0.729) correlation with the BPO/DMPT ratio. Modulus of elasticity followed a similar pattern to a lesser degree displaying a significant (F=5.123, p=0.001) reduction in values which was moderately correlated (r=−0.619), though insignificant (p= 0.101) with BPO/ DMPT ratio. Discussion and Conclusions: Varying the monomer/ polymer ratio independently from other constituents in acrylic bone cement significantly affects setting time and compressive mechanical properties. Setting time can be prolonged to increase handling time; however this will occur at the expense of a reduction in compressive stiffness and strength. Similarly, varying the BPO/DMPT ratio may result in optimised handling time; however, this will also cause a reduction in compressive strength and stiffness. These finding are paramount in clinical applications where compressive strength is essential e.g. percutaneous vertebroplasty

We performed a biomechanical study to compare the augmentation of isolated fractured vertebral bodies using two different bone tamps. Compression fractures were created in 21 vertebral bodies harvested from red deer after determining their initial strength and stiffness, which was then assessed after standardised bipedicular vertebral augmentation using a balloon or an expandable polymer bone tamp. The median strength and stiffness of the balloon bone tamp group was 6.71 kN (. sd. 2.71) and 1.885 kN/mm (. sd. 0.340), respectively, versus 7.36 kN (. sd. 3.43) and 1.882 kN/mm (. sd. 0.868) in the polymer bone tamp group. The strength and stiffness tended to be greater in the polymer bone tamp group than in the balloon bone tamp group, but this difference was not statistically significant (strength p > 0.8, and stiffness p = 0.4)

Bone grafting utilises tissue harvesting from second anatomic location of same patient (autograft) or from a human donor (allograft) to treat bone defects. Limited availability of bone grafts, donor site morbidity and risk of disease transmission led to an alternative strategy for bone grafting as synthetic materials that can promote bone regeneration. Engineered bone grafts are biocompatible and possess sufficient mechanical strength to support fractured bone. Polymer scaffolds lack mechanical stability whereas ceramic scaffolds are stiffer resulting in loosening of implants. Combining polymer and ceramic to form scaffolds can enhance the physical and mechanical properties and can be used for bone tissue engineering. We hypothesised that the nucleation of hydroxyapatite in carboxymethyl cellulose (CMC) matrix would improve scaffold properties physically and mechanically; thus, demonstrating CMC based biomimetic process to synthesise novel CMC/ HA scaffolds with suitable physical, mechanical and biological properties for bone tissue engineering. CMC/ HA scaffolds were synthesized by in situmethod at room temperature (RT) and 60°C and are labelled as CHRT and CH60 respectively, keeping the molar ratio of Ca/P as constant ∼1.6. The nucleation of hydroxyapatite (HA) from calcium chloride (CaCl. 2. ) and sodium dihydrogen phosphate (NaH. 2. PO. 4. ) was initiated inside carboxymethyl cellulose (CMC). CaCl. 2. solution was introduced gently in aqueous solution of CMC, thereafter; NaH. 2. PO. 4. solution was added dropwise and the mixture was stirred vigorously, kept overnight for aging at RT to obtain milky white slurry. The slurry was washed with distilled water to neutralize, cast into moulds and dried in hot air oven for 72 h to obtain scaffolds. Scanning electron microscopy (SEM) was performed to determine the surface topography of the scaffolds. Mechanical properties were tested with Universal Testing Machine (UTM) and cytotoxicity was performed by MTT assay using fibroblast cells (NIH 3T3). SEM images shows that HA aggregates like beads and knitted orderly over CMC backbone. There is an increase in HA agglomerates and decrease in bead size with increase in synthesis temperature from RT to 60°C. Scaffolds synthesized at 60°C show enhanced mechanical properties. Compressive strength of CHRT and CH60 are 0.68 MPa and 0.9 MPa respectively and compressive moduli of CHRT and CH60 are 33 MPa and 69 MPa respectively. MTT assay confirmed proliferation of fibroblast cells, hence; proved the non-toxic nature of the scaffolds. MTT assay reveals the cell viability (cell exoskeleton) on the scaffolds after 24 h incubation. In this study, CMC/ HA scaffolds were synthesised by in situmethod at RT and 60°C. Enhanced mechanical properties and cytocompatibility reveal the potentiality of the scaffolds for bone tissue engineering purposes

Introduction. Acetabular component loosening has been one of the factors of revision of total hip arthroplasty (THA). Inadequate mechanical fixation or load transfer may contribute to this loosening process. Several reports showed the load transfer in the acetabulum by metal components. However, there is no report about the influence of the joint surface on the load transfer. We developed a novel acetabular cross-linked polyethylene (CLPE) liner with graft biocompatible phospholipid polymer(MPC) on the surface. The MPC polymer surface had high lubricity and low friction. We hypothesized the acetabular component with MPC polymer surface (MPC-CLPE) may reduce load transfer in the acetabulum compared to that of the by CLPE acetabular component without MPC. Methods. We fixed the three cement cup with MPC-CLPE (Group M; sample No.1–3) and three cement cup with CLPE (Group C; sample No.4–6) placed in the synthetic bone block with bone cement with a 0.10mm thick arc-shaped piezoresistive force sensor, which can measure the dynamic load transfer(Tekscan K-scan 4400; Boston). (Fig 1) A hip simulator (MTS Systems Corp., Eden Prairie, MN) was used for the load transfer test performed according to the ISO Standard 14242-1. Both groups had same inner and outer diameter s of 28 and 50mm, respectively. A Co–Cr alloy femoral head with a diameter of 28 mm (K-MAXs HH-02; KYOCERA Medical Corp.) was used as the femoral component. A biaxial rocking motion was applied to the head/cup interface via an offset bearing assembly with an inclined angle of +20. Both the loading and motion were synchronized at 1 Hz. According to the double-peaked Paul-type physiologic hip load, the applied peak loads were 1793 and 2744 N described in a previous study. The simulator was run 3 cycles. We recorded both the peak of the contact force and the accumulation of the six times load in total. Secondly, we calculated the mean change of the load transfer. We used the Student t-test. P value < 0.05 was used to determine statistical significance. We used EZR for statistical analysis. Results. The mean of total accumulation of the load transfer in the group M is significantly lower than that of in the group C. (7037±508 N vs 11019±1290 N, P<0.0001). The peak of load in the group M was also significantly lower than that in the group C. (1024±166 N vs 1557±395 N) (Fig 2)The mean of the change of the load transfer in the group M is significantly lower than that of in the group C. (2913±112 N vs 4182±306 N) (Fig 3). Conclusion. The acetabular component with MPC surface could reduce and prevent the radical load transfer change toward to the acetabulum compared to CLPE acetabular component without MPC. For any figures or tables, please contact the authors directly

Background. Stress shielding and wear induced aseptic loosening cause failure in arthroplasty surgery. To improve survivorship, the use of a low modulus, low wearing biomaterial may be a suitable alternative to hard bearing prostheses, such as cobalt chromium (CoCr). There has been considerable research interest in the use of polyetheretherketone (PEEK) based on observed clinical success especially in spinal surgery. This study investigated the wear performance of PEEK, carbon reinforced PEEK (CFR-PEEK) and acetal as bearing materials in an all polymer total knee arthroplasty (TKA) using a unidirectional pin on plate test. Methods. The following material combinations were tested: PEEK vs. UHMWPE, CFR-PEEK vs. UHMWPE, PEEK vs. PEEK, CFR-PEEK vs. PEEK, CoCr vs. UHMWPE, PEEK vs. XLPE, CFR-PEEK vs. CFR-PEEK, PEEK vs. Acetal, Acetal vs. XLPE and CoCr vs. XLPE.Tribological couples tested (Pin vs. Plate) Using a previously validated modification of ASTM F732, 20mm diameter spherically ended pins with a radius of 25mm were articulated against 40mm diameter plates. A load of 1000N was applied to generate a contact stress of about 70MPa similar to contact stresses previously reported in the knee. The lubricant used was 25% newborn calf serum containing 0.3% sodium azide to retard bacteria growth and 20mM EDTA to prevent calcium deposition. Three repeats of pin on plate combinations (including 2 passive soak controls) were tested for 2 million cycles at a cycle frequency of 1Hz and a stroke length of 10 mm. Gravimetric wear was analysed every 250,000 cycles and results converted to volumetric wear using material density. Results. All CFR-PEEK articulations were stopped due to excessive wear of the counter-surfaces. Results showed a linear wear rate of UHMWPE and XLPE plates over the test period. PEEK vs. XLPE showed similar wear rate to metal on polyethylene (MoP) bearings. Conclusion. At stresses representative of the knee, PEEK pins when articulated against XLPE plates generated volumetric wear similar to that noted in MoP bearings

We developed a new porous scaffold made from a synthetic polymer, poly(DL-lactide-co-glycolide) (PLG), and evaluated its use in the repair of cartilage. Osteochondral defects made on the femoral trochlear of rabbits were treated by transplantation of the PLG scaffold, examined histologically and compared with an untreated control group. Fibrous tissue was initially organised in an arcade array with poor cellularity at the articular surface of the scaffold. The tissue regenerated to cartilage at the articular surface. In the subchondral area, new bone formed and the scaffold was absorbed. The histological scores were significantly higher in the defects treated by the scaffold than in the control group (p < 0.05). Our findings suggest that in an animal model the new porous PLG scaffold is effective for repairing full-thickness osteochondral defects without cultured cells and growth factors

Background. Impaction bone grafting with milled human allograft is the gold standard for replacing lost bone stock during revision hip surgery. Problems surrounding the use of allograft include cost, availability, disease transmission and stem subsidence (usually due to shear failure of the surrounding allograft). Aims. To investigate various polymers for use as substitute allograft. The ideal graft would be a composite with similar mechanical characteristics as allograft, and with the ability to form de novo bone. Methods. High and low molecular weight (MW) forms of three different polymers (polylactic acid (PLA), poly (lactic-co-glycolic) acid (PLGA) and polycaprolactone (PCL)) were milled, impacted into discs, and then tested in a custom built shear testing rig, and compared to allograft. A second stage of the experiment involved the addition of skeletal stem cells (SSC) to each of the milled polymers, impaction, 8 days incubation, and then tests for cell viability and number, via fluorostaining and biochemical (WST-1, DNA) assays. Results. The shear strengths of both high/ low MW PLA, and high/low MW PLGA were significantly higher than those of milled allograft but high and low MW PCL was poor to impact, and had significantly lower shear strengths. Fluorostaining showed good cell survival on high MW PLA, high MW PCL and both high and low MW PLGA. These findings were confirmed on both DNA and WST-1 assays. Conclusions. High MW PLA as well as high and low MW PLGA performed well both in mechanical testing and cell compatibility studies. These three polymers are good contenders to produce a living composite for use as substitute human allograft in impaction bone grafting

Aims. Impaction bone grafting with milled human allograft is the gold standard for replacing lost bone stock during revision hip surgery. Problems surrounding the use of allograft include cost, availability, disease transmission and stem subsidence (usually due to shear failure of the surrounding allograft). The aim of this study was to investigate various polymers for use as substitute allograft. The ideal graft would be a composite with similar mechanical characteristics as allograft, and with the ability to form de novo bone. Methods. High and low molecular weight (MW) forms of three different polymers (polylactic acid (PLA), poly (lactic co-glycolic) acid (PLGA) and polycaprolactone (PCL)) were milled, impacted into discs, and then tested in a custom built shear testing rig, and compared to allograft. A second stage of the experiment involved the addition of skeletal stem cells (SSC) to each of the milled polymers, impaction, 8 days incubation, and then tests for cell viability and number, via fluorostaining and biochemical (WST-1) assays. Results. The shear strengths of both high/low MW PLA, and high/low MW PLGA were significantly higher than those of milled allograft (P< 0.001, P< 0.001, P< 0.005 and P< 0.005) but high and low MW PCL was poor to impact, and had significantly lower shear strengths (P< 0.005, P< 0.001). Fluorostaining showed good cell survival on high MW PLA, high MW PCL and high MW PLGA. These findings were confirmed with WST-1 assays. Conclusions. High MW PLA as well as high MW PLGA performed well both in mechanical testing and cell compatibility studies. These two polymers are good contenders to produce a living composite for use as substitute human allograft in impaction bone grafting, and are currently being optimised for this use via the investigation of different production techniques and in-vivo studies

Impaction bone grafting with milled human allograft is the gold standard for replacing lost bone stock during revision hip surgery. Problems surrounding the use of allograft include cost, availability, disease transmission and stem subsidence (usually due to shear failure of the surrounding allograft). The aim of this study was to investigate various polymers for use as substitute allograft. The ideal graft would be a composite with similar mechanical characteristics as allograft, and with the ability to form de novo bone. High and low molecular weight (MW) forms of three different polymers (polylactic acid (PLA), poly (lactic co-glycolic) acid (PLGA) and polycaprolactone (PCL)) were milled, impacted into discs, and then tested in a custom built shear testing rig, and compared to allograft. A second stage of the experiment involved the addition of skeletal stem cells (SSC) to each of the milled polymers, impaction, 8 days incubation, and then tests for cell viability and number, via fluorostaining and biochemical (WST-1) assays. The shear strengths of both high/ low MW PLA, and high/low MW PLGA were significantly higher than those of milled allograft (P<0.001, P<0.001, P<0.005 and P<0.005) but high and low MW PCL was poor to impact, and had significantly lower shear strengths (P<0.005, P<0.001). Fluorostaining showed good cell survival on high MW PLA, high MW PCL and high MW PLGA. These findings were confirmed with WST-1 assays. High MW PLA as well as high MW PLGA performed well both in mechanical testing and cell compatibility studies. These two polymers are good contenders to produce a living composite for use as substitute human allograft in impaction bone grafting, and are currently being optimised for this use via the investigation of different production techniques and in-vivo studies

Reducion of friction between bearing surfaces in Total Hip Arthroplasty is a main target of biological tribology. MPC (2-Methacryloyloxyethyl phosphorylcholine) has a similar properties to those of cell membranes, and can reduce friction with fluid luburication. We have used crosslink polyethylene with MPC polymer coating for primary and revision THA since 2011. Eighty one cementless THA were performed with closslink polyethlene liner with MPC polymer in our hospital. We have examined 21 cases which were followed for more than one year. Eighteen cases for primary THA and three for revision THA, and 3 were male and 18 were female. Seventeen cases were osteoarthritis, two osteonecrosis of femoral head and two rheumatoid arthritis. Average age of patients at THA was 60.4 years old. In the OR, we have experienced a very wet and slippery feeling on the bearing surface of polyethylene liner every time. Surface touch is similar to skin with lotions. No wear were measured on the X-ray display and no infections and no fractures were occurred during follow up. MPC polymer coating in THA can be useful for reduction of friction and generation of wear debris

Objectives: Ex vivo biomechanical study to compare the properties of isolated, fractured, vertebral bodies after treatment by kyphoplasty with one of two bone tamps: a balloon bone tamp (Kyphon®) or an expandable polymer bone tamp (SKyBone®). Methods: Simulated compression fractures were created in 21 vertebral bodies (L3–5) harvested from red deer (sp. elaphus. elaphus), with initial strength and stiffness determined concurrently. Deer spine was selected as an alternative to human cadaveric spine due to its availability and its very similar bone density and morphological profile. Vertebral bodies were assigned to one of three groups: (1) unaugmented (control); (2) kyphoplasty using a balloon bone tamp (BBT); and (3) kyphoplasty using a polymer bone tamp (PBT). The kyphoplasty treatment consisted of deploying the bone tamp biped-icularly, then filling the created voids with standardised low viscosity cement. All vertebrae were then recom-pressed to determine their augmented strength and stiffness. Data was analysed using one-way analysis of variance test and paired samples T-Test. Result: Following fracture and subsequent kyphoplasty augmentation, the median strength of the BBT group was 6.71kN (± 2.71) vs 7.36kN (± 3.43) in the PBT group. Median stiffness in the balloon bone tamp group was 1.885 kN/mm (± 0.340) compared with 1.882 kN/ mm (± 0.868). Augmented strength tended to be greater in the PBT group than for BBT group, but this difference was not significantly different (p> .8). Significantly greater strength was obtained after kyphoplasty using BBT or PBT, compared with control group (p=.001 and .04, respectively). BBT and PBT groups were not statistically different for augmented stiffness (p=.4). Both BBT and PBT groups have greater augmented stiffness as compared to the control group (p=.007 and .005, respectively). Conclusions: The use of a polymer bone tamp creates similar augmented vertebral body strength and stiffness as compared with the widely used balloon bone tamp in a deer spine model. Similar results would be expected in human spine and consequently the polymer bone tamp may be used as an alternative bone tamp for kyphoplasty

Friction between bearing surfaces in Total Hip Arthroplasty has been a main target of applied tribology. MPC (2-Methacryloyloxyethyl phosphorylcholine) has a similar properties to those of cell membranes, and can reduce friction with fluid lubrication in wet environment. We have used crosslink polyethylene with MPC polymer coating for primary and revision THA since 2011. We have examined 19 cases which were followed for more than two years. Sixteen cases for primary THA and three for revision THA, and 3 were male and 16 were female. Sixteen cases were osteoarthritis, one osteonecrosis of femoral head and two rheumatoid arthritis. Average age of patients at THA was 60.1 years old. In the OR, we have experienced a very wet and slippery feeling on the bearing surface of polyethylene liner. Surface touch is similar to hard surface with oil or lotions. No PE wear were measured on the X-ray display and no infections and no fractures were occurred during follow up. MPC polymer coating in THA can be useful for reduction of friction and generation of wear debris

Polyetheretherketone (PEEK) is a thermoplastic polymer that is predominant in spinal surgery as the material of choice for spinal fusion cages, and is also used for bone anchors, cruciate ligament interference screws, and femoral stems. It has the distinct advantage of having similar mechanical properties to bone, but its clinical application as implant material is limited by a lack of bioactivity. This project aims to create an PEEK surface capable of osseointegration using a surface modification technique known as oxygen plasma treatment. PEEK surfaces were injection molded, washed and then treated in a plasma chamber for up to 10 min. Surfaces were characterised using atomic force microscopy (AFM), scanning electron microscopy (SEM), water contact angle measurements and X-ray photo-electron spectroscopy (XPS). Human bone marrow cells were cultured on the surfaces and assessed for calcium production (using alizarin red stain). Water contact angle measurements show that after plasma treatment, the surfaces become very hydrophilic, before developing a meta-stable state at approx. 6 weeks. AFM and SEM showed destruction of the nano-pits at treatment durations longer than 2 mins. XPS detected a progressive increase in the atomic proportion of oxygen at the surface with increasing plasma treatment duration. There was significantly less alizarin uptake (and hence calcium production) on the untreated PEEK compared to the plasma treated PEEK surfaces (p < 0.05). These results show that oxygen-plasma treatment can increase calcium production on PEEK surfaces and may improve long term osseointegration of PEEK implants

To improve the longevity of total hip replacements (THR), it is necessary to prevent wear of the ultra-high molecular weight polyethylene (UHMWPE) bearing, as wear debris can cause osteolysis and aseptic loosening. Highly cross-linked UHMWPE reduces wear, sometimes stabilized with vitamin E to preserve its mechanical properties and prevent oxidative degeneration. An extra novel solution has been grafting the surface of UHMWPE with poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC). This treatment uses a hydrophilic (wettable) phospholipid polymer to improve lubrication and reduce friction and wear of the bearing material. We set out to test the wear and friction of ceramic-on-polyethylene (COP) THRs that had the PMPC surface treatment, or left untreated for control. Four groups of UHMWPE bearings were tested against identical 40mm ceramic heads (zirconia-toughened alumina). The UHMWPE bearings were highly cross-linked with/without vitamin E (HXL Vit. E: 125 kGy radiation dose / HXL: 75 kGy). In each group, half underwent the PMPC treatment (n = 3 for all four groups). Testing was conducted on an AMTI hip simulator for 10 million walking cycles of ISO-14242-1, at 1 Hz, with diluted bovine serum (30 g/L protein concentration) as lubricant, at 37ºC, and with fluid absorption errors corrected with active soak controls. Using a previously published method, frictional torques and a frictional factor around three orthogonal axes about the femoral head were measured/computed, by data processing of the measurements of a 6-DOF load cell on each station of the hip simulator. Such friction measurements and stops for specimen weighing were carried out at regular intervals throughout the wear test. The HXL liners without and with the PMPC treatment wore at 5.86±0.402 mg/Mc and 1.70±1.36 mg/Mc, respectively (p=0.013) (Fig. 1). The HXL Vit. E liners without and with the PMPC treatment wore at 2.14±0.269 mg/Mc and 0.736±0.750 mg/Mc, respectively (p=0.035). The wear rates of the untreated HXL and HXL Vit. E liners were significantly different (p=0.0002) but no difference in wear rate was found between the two PMPC treated groups (p=0.179), although, as mentioned above, the PMPC treatment very significantly reduced wear in each case. The ceramic femoral heads showed little wear (weight loss) themselves. In general, the THRs showed decreasing friction over the 10 Mc, with the PMPC types showing a slight increase in friction towards the end of the test (Fig. 2). PMPC HXL liners showed the lowest friction factor (0.022±0.001) which was significantly lower (p<0.001) than the friction of the untreated liners (0.028±0.002) (Fig. 3). The PMPC HXL Vit. E liners showed lower friction factors than the untreated HXL Vit. E liners (0.034±0.002, 0.036±0.004, respectively), although this difference was not significant (p=0.116). Overall, the liners with the PMPC treatment displayed statistically significantly lower friction factors (p=0.003) than those untreated. The coincidence of some reduction of surface friction with larger wear reduction obviously suggests some but not necessarily full causality. PMPC successfully reduced both the friction and the wear in these COP THRs during this extended 10 Mc test. This likely would translate to improved implant longevity in patients. For any figures or tables, please contact authors directly (see Info & Metrics tab above).