Summary. Fifteen irradiated, vitamin E-diffused UHMWPE retrievals with up to three years in vivo service showed no appreciable oxidation, nor change in material properties from a never-implanted liner, and showed a 94% decrease in free radical content. Introduction. Radiation cross-linking, used to improve wear resistance of ultra-high molecular weight polyethylene (UHMWPE) bearings used in total joint arthroplasty, generates residual free radicals which are the precursors to oxidative embrittlement. First generation materials adopted thermal treatments to eliminate or reduce free radical content, but came with compromises in reduced mechanical properties or insufficient stabilization. A second generation alternative method infuses an antioxidant, vitamin E, into irradiated UHMWPE to stabilise free radicals while maintaining fatigue strength. In vitro studies predict excellent oxidation and wear resistance in vitamin E-stabilised bearings, but the long-term in vivo oxidation behavior, influenced by lipid absorption and cyclic loading, remains largely unknown. Our aim was to investigate in vivo changes in UHMWPE surgically-retrieved explants that were radiation cross-linked and stabilised by vitamin E. Patients & Methods. Fifteen surgically-retrieved irradiated, vitamin E-diffused and inert-gamma sterilised bearings (E1™, Biomet, Inc., Warsaw IN) with in vivo durations ranging from 3 days to 36.6 months were analyzed at unloaded rim/eminence and the articular surface along with one never-implanted component. Total lifetime of components was summed as shelf storage prior to implantation, in vivo duration and ex vivo duration in air. Fourier Transform Infrared Spectroscopy (FTIR) was used to measure carbonyl index (CI; per ASTM F2102-01ε1) both before and after 16 hour hexane extraction to. Extracted thin films were also reacted with nitric oxide to quantify hydroperoxides, an intermediate oxidation product associated with oxidation potential. Cross-link density was calculated from gravimetric swelling analysis per ASTM F2214. Crystallinity measurements were performed regionally using differential scanning calorimetry (DSC). Free radical content was measured by electron spin resonance (Memphis, TN). Results. Irradiated and vitamin E-diffused retrievals showed scratching at the articular surface, but retained machining marks up to three years in vivo, indicative of no measurable wear. Retrievals showed no significant oxidation at the time of surgical removal with maximum post-hexane carbonyl indices in the barely detectable range (MCI=0.029–0.154), located at the surface of retrievals. Ex vivo oxidation was not observed after 18 months of aging in air at room temperature. There was no increase in hydroperoxides (never-implanted HI=0.62±0.04; retrieval HI= 0.62±0.04), nor change in cross-link density (never-implanted: 0.275±0.015 mol/dm. 3. ; retrieval: 0.295±0.016 mol/dm. 3. ) or crystallinity (never-implanted: 58.3±1.4%; retrievals: 60.0±3.5%). Lipid penetration increased with time, showing a higher rate of diffusion in loaded regions. Free radical content was observed to decay with increasing in vivo duration (R. 2. =0.44; p<0.05), and by one order of magnitude (94%) by 36.6 months. A stronger negative correlation (R. 2. =0.65) was observed between the total lifetime of the liner and free radical content. Discussion/Conclusion. The free-radical scavenging activity of the vitamin E appears to successfully prevent both in vivo and ex vivo oxidation for short durations. Without an increase in hydroperoxides, the oxidation cascade initiated by radiation-induced and lipid-derived free radicals appears to have been halted. Retrievals also gave no indication of wear in this timeframe, similar to improved wear resistance seen in first generation materials. Continued monitoring will be necessary at longer implant durations

Summary. Understanding of the role of the radical-generating ability of wear particles of the existing and new implant materials as well as application of efficient antioxidants is one of the necessary conditions for improvement of the results of joint replacements. Introduction. Functioning of joint prostheses is accompanied by a continuous formation of wear particles and their accumulation in surrounding tissues. The impact of microroughnesses of joint prosthesis friction units may bring about chemical bond breakage and free-radical generation on a newly-formed wear surface. Wear particles of orthopedic alloys are capable to produce free radicals, and Co-Cr-Mo alloy particles are especially active. Free radicals generated by wear particles can cause oxidation and reduced wear resistance of polyethylene. Oxidised polyethylene particles stimulate the activity and release of bone-resorbing cytokines by human monocytes/macrophages. The ability of free radicals to cause damage to surrounding tissues and implant components makes it necessary to estimate comprehensively the radical-generating activity of wear particles of different orthopedic materials and develop the ways of its inhibition. Methods. Artificial Co-Cr-Mo alloy wear particles were obtained using dry friction of a ball against a disk. The radical-generating ability of orthopedic alloy wear particles was estimated by oxygen consumption using the model reaction of cumene oxidation. The radical-generating ability of wear particles was determined at different moments after their formation and storage at room temperature and humidity. In the experiments, a pro-inflammatory action of wear particles during their continuous formation was also simulated. Fresh cobalt alloy wear particles were used for a consecutive triple oxidation of 2 ml of cumene at a particle concentration of 0.3 mg/ml. After the first 40 min oxidation, a suspension of particles in cumene was centrifuged, and the used particles were removed. Fresh particles were added to oxidised cumene, and the second and third oxidations were carried out in a similar way. The ability of some antioxidants to inhibit the radical-generating ability of cobalt alloy wear particles was also determined. Results. Fresh cobalt alloy wear particles demonstrated an expressed radical-generating ability which remained practically at the initial level after a one-week storage. The ability gradually reduced in the process of storage. After a one-month storage the particles’ radical-generating ability decreased 2.6 times. A six-month storage of cobalt alloy particles resulted in a tenfold reduction of the radical-generating ability as compared to that of fresh particles. The intensification of radical formation was studied during three consecutive oxidations of cumene by wear particles. It was established that each consecutive oxidation of cumene by fresh wear particles occurred with a growing radical-generation ability. That parameter of the newly-formed particles increased more than two- and threefold during a consecutive double and triple cumene oxidation, respectively. Synthetic antioxidant BHT and natural antioxidant alpha-tocopherol were used for inhibition of wear particles-initiated free-radical reactions. Introduction of the antioxidants inhibited cumene oxidation with an antioxidant dose-dependent duration of this effect. In a mixture of alloy and orthopedic polyethylene particles, alpha-tocopherol completely inhibited the radical-generating activity of alloy particles thus preventing the polymer's oxidative destruction. Conclusion. The use of commercially available particles of orthopedic alloys with an uncontrolled duration storage in experiments considerably reduce or do not reveal the negative effects conditioned by their radical-generating ability. A proper study of the effect of the radical- generating ability of wear particles on the properties of implant components and surrounding tissues is possible only with the use of fresh particles. Permanent generation of free radicals in the process of wear of joint prosthesis metal components creates conditions for self-potentiation of negative free radical reactions during joint replacement. This requires the necessity of a preclinical estimation of the radical-generating ability of orthopedic materials and application of efficient antioxidants during the post-implantation period

Nitric oxide is a free radical which in vivo is solely produced during the conversion of the amino acid arginine into citrulline by nitric oxide synthase enzymes. Recently, the importance of nitric oxide on inflammation and bone metabolism has been investigated. However, the knowledge regarding possible in vitro effects of arginine supplementation on chondrogenic differentiation is limited. ATDC5, a cell line which is derived from mouse teratocarcinoma cells and which is characterized as chondrogenic cell line, were proliferated in Dulbecco's Modified Eagle Medium (DMEM)/F12 and subsequently differentiated in proliferation medium supplemented with insulin, transferrin and sodium-selenite and where arginine was added in four different concentrations (0, 7.5, 15 and 30 mM). Samples were harvested after 7 or 10 days and were stored at −80 °C for subsequent RNA isolation for qPCR analysis. To determine chondrogenic differentiation, Alcian Blue staining was performed to stain the proteoglycan aggrecan, which is secreted by differentiated ATDC5 cells. All measurements were performed in triplo. Alcian Blue staining showed a qualitative increase of proteoglycan aggrecan secretion in differentiated ATDC5 cells after treatment with 7 and 15 mM arginine, with additional increased expression of ColII, ColX, Bmp4 and Bmp6. Treatment with 30 mM arginine inhibited chondrogenic differentiation and expression of aforementioned genes, however, Cox-2 and Vegfa gene expression were increased in these samples. Bmp7 was not significantly expressed in any experimental condition. The obtained results are suggestive for a dose-dependent effect of arginine supplementation on chondrogenic differentiation and associated gene expression, with 7.5 and 15 mM as most optimal concentrations and implications for apoptosis after incubation with 30 mM arginine. A future recommendation would be to investigate the effects of citrulline in a similar experiment, as this shows even more promising results to enhance the nitric oxide metabolism in sepsis and bone healing

Abstract. Background. Progressive muscle ischaemia results in reduced aerobic respiration and increased anaerobic respiration, as cells attempt to survive in a hypoxic environment. Acute compartment syndrome (ACS) is a progressive form of muscle ischaemia that is a surgical emergency resulting in the production of Lactic acid by cells through anaerobic respiration. Our previous research has shown that it is possible to measure H+ ions concentration (pH) as a measure of progressive muscle ischaemia (in vivo) and hypoxia (in vitro). Our aim was to correlate intramuscular pH readings and cell viability techniques with the intramuscular concentration of key metabolic biomarkers [adenosine triphosphate (ATP), Phosphocreatine (PCr), lactate and pyruvate], to assess overall cell health in a hypoxic tissue model. Methods. Nine euthanised Wistar rats were used in a non-circulatory model. A pH catheter was used to measure real-time pH levels from one of the exposed gluteus medius muscles, while muscle biopsies were taken from the contralateral gluteus medius at the start of the experiment and subsequently at every 0.1 of a pH unit decline. The metabolic biomarkers were extracted from the snap frozen muscle biopsies and analyzed with standard fluorimetric method. Another set of biopsies were stained with Hoechst 33342, Ethidium homodimer-1 and Calcein am and imaged with a Zeiss LSM880 confocal microscope. Results. Our study shows that the direct pH electrode readings decrease with time and took an average of 69 minutes to drop to a pH of 6.0. The concentrations of ATP, pyruvate and PCr declined over time, and the concentration of lactate increased over time. At pH 6.0, both ATP and PCr concentrations had decreased by 20% and pyruvate has decreased by 50%, whereas lactate had increased 6-fold. The majority of cells were still viable at a pH of 6.0, suggesting that skeletal muscle cells are remarkably robust to hypoxic insult, although this was a hypoxic model where reperfusion was not possible. Conclusions. Our research suggests that histologically, skeletal muscle cells are remarkably robust to hypoxic insult despite the reduction in the total adenine nucleotide pool, but this may not reflect the full extent of cell injury and quite possibly irreversible injury. The timely restoration of blood flow in theory should halt the hypoxic insult, but late reperfusion results in cellular dysfunction and cell death due to localised free radical formation. Further research investigating the effects of reperfusion in vivo are warranted, as this may identify an optimal time for using pharmacological agents to limit reperfusion injury, around the time of fasciotomy to treat acute compartment syndrome. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Secondary sterilisation of allograft bone by gamma irradiation is common, but the conditions under which it is performed vary between tissue banks. Some do so at room temperature, others while the bone is frozen. Bone is made brittle by irradiation because of the destruction of collagen alpha chains, probably mediated by free radicals generated from water molecules. Freezing reduces the mobility of water molecules and may therefore decrease the production of free radicals. We found that bone irradiated at −78°C was less brittle and had less collagen damage than when irradiated at room temperature. These findings may have implications for bone-banking

Summary. Sequentially irradiated and annealed UHMWPE hip and knee retrievals showed subsurface in vivo oxidation in both the articular surface and unloaded surfaces, while three of four never-implanted shelf stored liners had oxidation in the bulk. Introduction. Highly cross-linked polyethylene was developed to improve the wear resistance of UHMWPE bearing surfaces in total hip arthroplasty. First generation irradiated and annealed polyethylene showed high oxidation in vivo, largely attributed to only the partial-quenching of free radicals, along with additional radicals generated during terminal gamma sterilization. A second generation, three-step sequential irradiation and annealing method was advanced with the promise of better oxidative stability and improved mechanical properties. We hypothesised that without the complete elimination of free radicals combined with gas plasma sterilization requiring oxygen-permeable packaging, that this second generation material would be prone to shelf-oxidation in addition to in vivo oxidation. Patients & Methods. Fifty surgically-retrieved sequentially irradiated and annealed, gas plasma-sterilised UHWMPE acetabular liners and tibial bearings (X3™, Stryker, Mahwah, NJ), with in vivo durations of 0.5–73 months, were analyzed at their articular surface and an unloaded surface, along with four never implanted acetabular liners. Infrared microscopy was used to evaluate lipid absorption, oxidation (per ASTM F2102-01ε1) and hydroperoxide levels after nitric oxide staining. Gravimetric swelling analysis assessed cross-link density (per ASTM F2214), and crystallinity measurements were performed using differential scanning calorimetry. Results. There was detectable oxidation (OI > 0.1) in 37 of the 50 components with as little as 2 weeks of in vivo service. Maximum oxidation values averaged OI = 0.30 ± 0.30 (range = 0.03–1.59). Oxidation profiles were predominantly characterised by subsurface oxidation peaks approximately 1–2 mm below the surface, in both the articular surface and rim, along with a pattern of embrittlement induced white banding in four and six year liners. Three short in vivo duration liners (0.1–15.5 month) showed oxidation and degradation of material properties throughout the bulk. Three of four never-implanted liners, with up to five years shelf storage, also showed bulk oxidation (Max OI ≤ 1.5), loss of cross-link density and increased crystallinity. Discussion/Conclusion. High levels of detectable oxidation, subsurface oxidation peaks, and white banding were all identified in sequentially irradiated and annealed UHMWPE retrievals with short in vivo durations. These results raise concerns about the long-term clinical performance of these materials. Oxidation measured in shelf-stored, never implanted liners also raises concerns that liners may already be oxidatively compromised before being implanted into patients. Due to gas plasma sterilization methods, these free-radical containing liners are packaged and stored in air, likely resulting in a pre-implantation oxidation effect similar to that historically reported in gamma-in-air sterilised UHMWPE. Longer-term retrievals are needed to better understand the progress of these in vivo changes and whether or not it will compromise the longevity of the implants

Healthcare associated infections (HAI) pose a major threat to patients admitted to hospitals, and infection rates following orthopaedic arthroplasty surgery are as high as 4%, while the infection rates are even higher after revision surgery. 405 nm High-Intensity Narrow Spectrum (HINS) light has been proven to reduce environmental contamination in hospital isolation rooms, and there is potential to develop this technology for application in orthopaedic surgery. Cultured rat osteoblasts were exposed to 405 nm light to investigate if bactericidal doses of light could be used safely in the presence of mammalian cells. Cell viability was measured by MTT reduction and microscopy techniques, function by alkaline phosphatase activity, and proliferation by the BrdU assay. Exposures of up to a dose of 36 J/cm. 2. had no significant effect on osteoblast cell viability, whilst exposure of a variety of clinically relevant bacteria, to 36 J/cm. 2. resulted in up to 100% kill. Exposure to a higher dose of 54 J/cm. 2. significantly affected the osteoblast cell viability, indicating dose dependency. Work also demonstrated that 405 nm light exposure induces reactive oxygen species (ROS) production in both mammalian and bacterial cells, as shown by fluorescence generated from 6-carboxy-2′,7′-dichlorodihydrofluorescein diacetate dye. The mammalian cells were significantly protected from dying at 54 J/cm. 2. by catalase, which detoxifies H. 2. O. 2. Bacterial cells were significantly protected by sodium pyruvate (H. 2. O. 2. scavenger) and by a combination of free radical scavengers (sodium pyruvate, dimethyl thiourea (·OH scavenger), catalase) at 162 and 324 J/cm. 2. Thus the cytotoxic mechanism of 405 nm light in mammalian cells and bacteria is likely oxidative stress involving predominantly H. 2. O. 2. generation, with other ROS contributing to the damage. Additional work describing the potential for incorporation of this antimicrobial light within operating theatre lighting systems will also be discussed, and this, coupled with the cell viability and cytotoxicity results, suggests that 405 nm light could have great potential for continual patient safe decontamination during orthopaedic replacement surgeries and thereby reduce the incidence of infections

Among plant derived molecules, polyphenols have antioxidant, anticancer and antibacterial ability [1,2]. Moreover, they can stimulate osteoblast differentiation and promote apoptosis of tumoral cells [3–4]. It's thus possible combine the properties of these molecules with those of bioactive materials trough surface functionalization. A silica-based bioactive glass and chemically treated bioactive Ti6Al4V were used as substrates while gallic acid and polyphenols extracted from green tea or red grape skin as biomolecules for functionalization. The surface functionalization procedure was optimized in order to maximize the grafting and investigated by means of the Folin&Ciocalteu method and X-Ray Photoelectron Spectroscopy (XPS) analyses. The in vitrobioactivity was studied by means of Field Emission Scanning Electron Microscopy (FESEM) and Fourier Transform Infrared Spectroscopy (FTIR) after soaking in simulated body fluid (SBF). Surface charge and isoelectric point were investigated by means of zeta potential measurements. Free radical scavenging activity evaluation was performed in order to investigate the antioxidant ability of glass samples. Finally, the functionalization selective killing activity towards osteosarcoma cells was in vitroassayed by the metabolic 3-(4,5-Dimethylthiazol-2-Yl)-2,5-Diphenyltetrazolium Bromide (MTT) test and compared with non-tumoral control bone cells. The presence of polyphenols on the surfaces was confirmed by XPS analyses by the appearance of characteristic peaks (C-O and C=O bonds) in the carbon and oxygen regions. The Folin&Ciocalteu test demonstrated the presence and activity of polyphenols on all the substrates and evidenced a clear relation between surface reactivity and grafting ability. The bioactivity tests showed the deposition of hydroxyapatite on the functionalized samples and an influence of biomolecules on its amount and shape for glasses. Zeta potential measurements evidenced a shift of the isoelectric point of glass samples after functionalization. A certain antioxidant activity of bare glass has been evidenced and it is improved by the grafting of tea polyphenols. Accordingly, MTT results confirmed polyphenols selective killer activity towards osteosarcoma cells whose viability was significantly decreased in comparison with safe bone cells. XPS analyses, zeta potential measurements and Folin&Ciocalteu tests showed the presence and the activity of the polyphenols on the surfaces. Bioactivity tests highlighted an improvement of the deposition of hydroxyapatite on the surface of the functionalized glass samples. Certain antioxidant ability has been evidenced for glass samples and was further improved by tea polyphenols. Moreover, a selective toxic activity towards tumor cells was in vitropreliminary confirmed. In conclusions polyphenols were successfully grafted to the surface of glass and Ti6Al4V samples maintaining their activity. Polyphenols improve in vitro bioactivity, antioxidant and anticancer ability of glass. The surface functionalization seems to be a good way to combine the properties of bioactive materials for bone contact applications with those of polyphenols

Sterilisation by gamma irradiation in the presence of air causes free radicals generated in polyethylene (PE) to react with oxygen, which could lead to loss of physical properties and reduction in fatigue strength. Tissue retrieved from failed total hip replacements often has large quantities of particulate PE and most particles associated with peri-implant osteolysis are oxidised. Consequently, an understanding of the cellular responses of oxidised PE particles may lead to clarification of the pathogenesis of osteolysis and aseptic loosening. We have used the agarose system to demonstrate the differential effects of oxidised and non-oxidised PE particles on the release of proinflammatory products such as interleukin-1β (IL-1β), IL-6, and tumour necrosis factor-α (TNF-α) from monocytes/ macrophages (M/M). Oxidised PE particles were shown to stimulate human M/M to phagocytose and to release cytokines. Oxidation may alter the surface chemistry of the particles and enhance the response to specific membrane receptors on macrophages, such as scavenger-type receptors

Summary. Arginine supplementation is helpful in treatment of osteoporosis. Introduction. Nitric oxide (NO) is a short-lived free radical involved in several biological processes as a bioregulator and as a second messenger. It inhibits osteoclastic bone resorption in vitro and regulates bone remodeling. Zolendronic acid has been established as a treatment for post menopausal osteoporosis. Study was done to compare the efficacy of Nitic oxide donor (L-arginine) with that of Zolendronic acid for the treatment of osteoporosis. Method. The study was not designed to compare these two drugs against a placebo, because the beneficial effects of Zolendronic acid in treatment of osteoporosis are well established. Institutional Review Board approvals were obtained. One hundred patients of osteoporosis having T score of −2.5 or more, were randomised to receive L-arginine) or Zolendronic acid. All patients received 1.0 g of calcium and 400 IU of vitamin D supplementation per day. In addition Group I patients received L-arginine (2 gm.) per day while Group II patients received zoledronic acid 5 mg i.v. over 15 min. Patient were followed at regular intervals clinically, by biochemical investigations and at one year for DEXA scan. Results. Patients in both groups improved clinically and bio-chemically over one year period. T score on DEXA scan at one year showed improvement in bone density. Average pretreatment T score was −3.65 in group I and −3.52 in group II. At one year followup average T score was −2.9 in group I and −2.6 in group II. Difference was not statistically significant. Discussion. Oral administration of L-arginine in pharmacological doses induces growth hormone and insulin like growth factor-1 responses and stimulates nitric oxide synthesis. Growth hormone and insulin like growth factor-1 are important mediator of bone turnover and osteoblastic bone formation. While nitric oxide is potent inhibitor of osteoclastic bone resorption because of this dual effect on physiological regulator of bone remodeling. L-arginine could potentially increase bone formation over bone resorption and consequently increase bone mass. Oral supplementation of L-arginine may be novel strategy in prevention and treatment of osteoporosis

INTRODUCTION. Highly cross linked polyethylenes (HXPE) have to be treated thermally after irradiation to eliminate residual free radicals. By adding vitamin E in the polyethylene powder a post-irradiation thermal treatment is not necessary. In this review the correlation between the intrinsic properties and the long-term stability of Vitelene® as a high performance material for artificial hip articulation will be displayed. MATERIALS & METHODS. Three different types of polyethylene (UHMWPE; GUR1020) were analyzed to compare mechanical properties as well as oxidative stability: PE. STD. (γ, 30 kGy, N. 2. ), HXPE. REM. (γ, 75 kGy, remelted, EO), Vitelene® (β, 80 kGy, 0.1% Vitamin E, EO). Artificial aging (ASTM F2003 − 70 °C, O. 2. at 5 bar) was used to simulate environmental damage. To evaluate the oxidation stability the Oxidation-Induction-Time (OIT) was measured by Differential Scanning Calorimetry (DSC - ASTM D3895) and the Oxidation Index (OI) was determined by Fourier-Transformation-Infrared-Spectroscopy (FTIR - ASTM F2102). The mechanical properties were analyzed by tensile- and impact investigations (ASTM D638 and ISO 11542-2) as well as by Small Punch Testing (SPT - ASTM F2183). The amount of wear was measured gravimetrically (ISO 14242-2). RESULTS. OIT [minutes], after 0, 14, 28, 42, 56 and 70 days aging, respectively 0.47, 0.41, 0.45, 0.42, 0.42 and not determined (nd) for PE. STD,. 0.46, 0.46, 0.47, 0.41, 0.41 and nd for HXPE. REM,. 12.09±0.50, 11.67±0.54, 10.78±0.25, 10.42±0.36, nd and 9.25±0.19 for Vitelene®. Cristallinity [%], after 0, 14, 28 and 42 days aging, respectively 55±2, 63±2, 79±4, 88±3 for PE. STD. , 47±2, 48±0, 50±1, 57±1 for HXPE. REM. , 52±1, 51±1, 53±14, 53±2 for Vitelene®. OI, after 0, 14, 28, 35 and 42 days aging, respectively 0.11±0.03, 0.67±0.15, 4.48±1.17 for PE. STD. , 0.07±0.05, 0.06±0.02, 0.09±0.02, 0.24±0.05, 0.69±0.36 for HXPE. REM. , 0.06±0.01, 0.08±0.01, 0.08±0.01, 0.09±0.01, 0.09±0.01 for Vitelene®. Tensile Strength [MPa], after 0 and 42 days aging, respectively 47.9±10, 0.7±0 for PE. STD. , 56.0±4.0, 25.0±2.0 for HXPE. REM. , 53.1±1.0, 52.0±4.3 for Vitelene®. Elongation [%], after 0 and 42 days aging, respectively 469±69 and 0 for PE. STD. , 343±14, 7±3 for HXPE. REM. , 372±11, 380±15 for Vitelene®. Impact Strength [kJ/m²], after 0 and 42 days aging, respectively 149±6, 4±1 for PE. STD. , 95±1, 5±1 for HXPE. REM. , 86±10, 91±7 for Vitelene®. SPT - Average Ultimate Load [N], after 0, 14 and 28 days aging, respectively 61.5±4.0, 56.3±5.3, 8.2±0.2 for PE. STD. , 71.4±2.2, 68.0±9.9, 64.4±8.2 for Vitelene®. Wear [mg/Mio cycles] (Ø36 mm Biolox® delta), after 0, 14 and 42 days aging, respectively 19.0±0.6, 30.3±3.1 and 365.8±37,2 for PE. STD. , 2.0±0.3, nd and 52.0±16.4 for HXPE. REM. , 2.5±0.5, nd and 2.3±0.7 for Vitelene®. CONCLUSION. The mechanical properties of Vitelene® are unchanged even after 42 days of artificial aging which is correlated to low wear in total hip arthroplasty. Vitamin E stabilization is effective in preventing oxidation and aging of the polyethylene after irradiation cross linking

Summary. Four highly cross-linked UHWMPEs except vitamin E-stabilised explants. Introduction. The development of both first and second generation highly cross-linked material focused on stabilizing radiation-induced free radicals as the sole precursor to oxidative degradation; however, secondary in vivo oxidation mechanisms have been identified in both conventional and highly cross-linked UHMWPE, induced by absorbed lipids and cyclic mechanical load. Retrieval studies are reporting in vivo oxidation highly cross-linked retrievals with up to ten year in vivo durations. Preclinical aging tests did not predict these in vivo material changes. With only a decade of these materials in clinical use, retrieval studies are limited to mid-term follow-up. In vitro studies face a challenge in effectively replicating the precise in vivo conditions that lead to this loss of oxidation resistance. In this study, we bypass replicating these in vivo variables by examining surgically-retrieved components, thereby testing material that has been affectively “pre-conditioned” by their in vivo service. After a preliminary post-operative analysis, we subjected retrievals to accelerated aging tests in order to predict the extent to which their oxidative stability had been uniquely compromised in vivo. Patients & Methods. Twenty-four highly cross-linked retrievals of four manufacturing methods (n=6 each of Longevity™, Prolong™, X3™ and E1™) and in vivo durations (1–4 years) were analyzed post-operatively and after accelerated aging (70°C, 5atm O. 2. for 2 weeks; ASTM F2003). Never-implanted components (n=1) of each material type were also aged. Infrared microscopy was used to evaluate lipid absorption, oxidation (per ASTM F2102-01ε1) and hydroperoxide levels after 16 hrs of nitric oxide staining for oxidation potential, and gravimetric swelling analysis assessed cross-link density (ASTM F2214). Results. All retrievals contained absorbed lipids penetrating below both loaded (penetration depth=1.3 ± 0.5 mm) and unloaded (0.6 ± 0.2 mm) surfaces. Each material type subset contained retrievals with and without detectable oxidation after in vivo service (Max OI=0.01–0.94). After aging, all post-irradiation thermally-treated, highly cross-linked retrievals, regardless of initial lipid levels or oxidation, showed oxidative degradation, demonstrated by subsurface oxidative peaks (MOI=0.30–2.63), increased hydroperoxides (3–5X), and decreased cross-link density (−34–90%). In contrast, vitamin E-stabilised retrievals showed below MOI<0.2 with no significant loss of cross-link density. Never-implanted controls for each material type showed no oxidative changes after accelerated aging. Discussion/Conclusion. Accelerating aging after in vivo service has shown oxidative instability characterised by high oxidation and material property loss in the three highly cross-linked materials without an incorporated antioxidant. This oxidative degradation took place regardless of post-operative oxidation levels, indicating that even without detectable oxidation the material had undergone changes during in vivo service, as compared to the lack of oxidative response in never-implanted controls. These findings also suggest that the presence of an antioxidant may be able to slow down and/or stabilise in vivo mechanisms compromising long-term oxidative stability and increase the longevity of highly cross-linked UHMWPE materials

Objectives

Recently, high failure rates of metal-on-metal (MOM) hip implants have raised concerns of cobalt toxicity. Adverse reactions occur to cobalt nanoparticles (CoNPs) and cobalt ions (Co²⁺) during wear of MOM hip implants, but the toxic mechanism is not clear.

We studied the effect of vitamin C on fracture healing in the elderly. A total of 80 elderly Osteogenic Disorder Shionogi rats were divided into four groups with different rates of vitamin C intake. A closed bilateral fracture was made in the middle third of the femur of each rat. Five weeks after fracture the femora were analysed by mechanical and histological testing. The groups with the lower vitamin C intake demonstrated a lower mechanical resistance of the healing callus and a lower histological grade. The vitamin C levels in blood during healing correlated with the torque resistance of the callus formed (r = 0.525). Therefore, the supplementary vitamin C improved the mechanical resistance of the fracture callus in elderly rats. If these results are similar in humans, vitamin C supplementation should be recommended during fracture healing in the elderly.

When transferring tissue regenerative strategies involving skeletal stem cells to human application, consideration needs to be given to factors that may affect the function of the cells that are transferred. Local anaesthetics are frequently used during surgical procedures, either administered directly into the operative site or infiltrated subcutaneously around the wound. The aim of this study was to investigate the effects of commonly used local anaesthetics on the morphology, function and survival of human adult skeletal stem cells.

Cells from three patients who were undergoing elective hip replacement were harvested and incubated for two hours with 1% lidocaine, 0.5% levobupivacaine or 0.5% bupivacaine hydrochloride solutions. Viability was quantified using WST-1 and DNA assays. Viability and morphology were further characterised using CellTracker Green/Ethidium Homodimer-1 immunocytochemistry and function was assessed by an alkaline phosphatase assay. An additional group was cultured for a further seven days to allow potential recovery of the cells after removal of the local anaesthetic.

A statistically significant and dose dependent reduction in cell viability and number was observed in the cell cultures exposed to all three local anaesthetics at concentrations of 25% and 50%, and this was maintained even following culture for a further seven days.

This study indicates that certain local anaesthetic agents in widespread clinical use are deleterious to skeletal progenitor cells when studied in vitro; this might have relevance in clinical applications.

Osteoarthritis (OA) is an important cause of pain, disability and economic loss in humans, and is similarly important in the horse. Recent knowledge on post-traumatic OA has suggested opportunities for early intervention, but it is difficult to identify the appropriate time of these interventions. The horse provides two useful mechanisms to answer these questions: 1) extensive experience with clinical OA in horses; and 2) use of a consistently predictable model of OA that can help study early pathobiological events, define targets for therapeutic intervention and then test these putative therapies. This paper summarises the syndromes of clinical OA in horses including pathogenesis, diagnosis and treatment, and details controlled studies of various treatment options using an equine model of clinical OA.

Platelet-rich plasma is a new inductive therapy which is being increasingly used for the treatment of the complications of bone healing, such as infection and nonunion. The activator for platelet-rich plasma is a mixture of thrombin and calcium chloride which produces a platelet-rich gel.

We analysed the antibacterial effect of platelet-rich gel in vitro by using the platelet-rich plasma samples of 20 volunteers. In vitro laboratory susceptibility to platelet-rich gel was determined by the Kirby-Bauer disc-diffusion method. Baseline antimicrobial activity was assessed by measuring the zones of inhibition on agar plates coated with selected bacterial strains.

Zones of inhibition produced by platelet-rich gel ranged between 6 mm and 24 mm (mean 9.83 mm) in diameter. Platelet-rich gel inhibited the growth of Staphylococcus aureus and was also active against Escherichia coli. There was no activity against Klebsiella pneumoniae, Enterococcus faecalis, and Pseudomonas aeruginosa. Moreover, platelet-rich gel seemed to induce the in vitro growth of Ps. aeruginosa, suggesting that it may cause an exacerbation of infections with this organism. We believe that a combination of the inductive and antimicrobial properties of platelet-rich gel can improve the treatment of infected delayed healing and nonunion.

The purpose of this study was to examine the effects of hyaluronic acid supplementation on chondrocyte metabolism in vitro. The clinical benefits of intra-articular hyaluronic acid injections are thought to occur through improved joint lubrication. Recent findings have shown that exogenous hyaluronic acid is incorporated into articular cartilage where it may have a direct biological effect on chondrocytes through CD44 receptors.

Bovine articular chondrocytes were isolated and seeded into alginate constructs. These were cultured in medium containing hyaluronic acid at varying concentrations. Samples were assayed for biochemical and histological changes.

There was a dose-dependent response to the exposure of hyaluronic acid to bovine articular chondrocytes in vitro. Low concentrations of hyaluronic acid (0.1 mg/mL and 1 mg/mL) significantly increase DNA, sulphated glycosaminoglycan and hydroxyproline synthesis. Immunohistology confirmed the maintenance of cell phenotype with increased matrix deposition of chondroitin-6-sulphate and collagen type II. These findings confirm a stimulatory effect of hyaluronic acid on chondrocyte metabolism.