Effect of gamma irradiation on the osteoinductivity of morphogenetic protein extract from reindeer bone

BACKGROUND: Bone morphogenetic proteins (BMPs), which are capable of stimulating the production of new bone, must be sterilized before preclinical and clinical use to reduce the risk of infections and associated complications. In this study, we investigated the effects of gamma sterilization on the osteoinductivity of native reindeer BMP extract in the Balb/C mouse thigh muscle pouch model. METHODS: 5 mg of native reindeer BMP extract and 5 mg of bovine serum albumin were administered separately either in gelatine capsules or mixed with gelatine as injections. The dose of gamma irradiation was 4.1 Mrad. Unsterile capsules and injections served as controls. New bone formation was evaluated based on the incorporation of Ca45 and also radiographically 3 weeks after implantation. RESULTS: Albumin-containing implants and injections did not induce new bone formation, as monitored in radiographs. Gamma sterilization did not reduce the osteoinductivity of native BMP extract in capsules, but a significant decrease in osteoinductivity--measured as area (50%) and Ca45 incorporation of new bone (27%)--was seen after injection. Gamma sterilization had no effect on the optical density of new bone induced by native BMP extract administered in capsules or by injection. INTERPRETATION: We conclude that, as gamma irradiation did not reduce the osteoinductivity of reindeer BMP extract in gelatine capsules, this method appears to be suitable for sterilization of BMPs to be given in capsule form. Native reindeer BMP extract was more sensitive to irradiation in soluble collagen (gelatine) than BMP in gelatine capsules. This finding must be given serious consideration regarding treatment of patients, but the remaining activity may be sufficient for the induction of bone formation in preclinical and clinical situations.     

Effect of gamma irradiation on the osteoinductivity of morphogenetic protein extract from reindeer bone

Background Bone morphogenetic proteins (BMPs), which are capable of stimulating the production of new bone, must be sterilized before preclinical and clinical use to reduce the risk of infections and associated complications. In this study, we investigated the effects of gamma sterilization on the osteoinductivity of native reindeer BMP extract in the Balb/C mouse thigh muscle pouch model.

Methods 5?mg of native reindeer BMP extract and 5?mg of bovine serum albumin were administered separately either in gelatine capsules or mixed with gelatine as injections. The dose of gamma irradiation was 4.1?MRad. Unsterile capsules and injections served as controls. New bone formation was evaluated based on the incorporation of Ca⁴⁵and also radiographically 3 weeks after implantation.

Results Albumin-containing implants and injections did not induce new bone formation, as monitored in radiographs. Gamma sterilization did not reduce the osteoinductivity of native BMP extract in capsules, but a significant decrease in osteoinductivity-measured as area (50%) and Ca⁴⁵incorporation of new bone (27%)-was seen after injection. Gamma sterilization had no effect on the optical density of new bone induced by native BMP extract administered in capsules or by injection.

Interpretation We conclude that, as gamma irradiation did not reduce the osteoinductivity of reindeer BMP extract in gelatine capsules, this method appears to be suitable for sterilization of BMPs to be given in capsule form. Native reindeer BMP extract was more sensitive to irradiation in soluble collagen (gelatine) than BMP in gelatine capsules. This finding must be given serious consideration regarding treatment of patients, but the remaining activity may be sufficient for the induction of bone formation in preclinical and clinical situations.     

Reindeer BMP extract in the healing of critical-size bone defects in the radius of the rabbit

Background?Native BMP extracts from reindeer effectively induce ectopic new bone formation in vivo, but their bone healing properties have not yet been evaluated. We investigated the effect of reindeer BMP extracts on the healing of long bone defects.

Methods?The implants tested contained 5?mg or 10?mg of unsterilized BMP extract from reindeer and 10?mg of gamma-sterilized BMP extract administered with collagen carrier (Lyostypt, B. Braun, Germany). 70 μg of rhBMP-2 with collagen carrier (InductOs; Wyeth Europa) served as positive control, and collagen implants (Lyostypt) and untreated defects served as negative controls. New Zealand White rabbits with 1.5?cm of critical-size radius bone defects were used, with 8 weeks of follow-up.

Results?Radiographic analysis showed bone formation (BF) to be higher in all groups containing BMPs than in the untreated controls. BF was also higher in the rhBMP-2 group, and marginally higher in the group treated with 10?mg of unsterilized reindeer BMP extract (p = 0.06) as compared to the collagen controls. Bone union (BU) was better in the unsterilized BMP extract groups and rhBMP-2 group than in the untreated controls. BU was also better in the implants with 10?mg of unsterilized reindeer BMP extract and rhBMP-2 than in the collagen-treated implants. The mean area of new bone at the site of the defect proved to be higher in all implants containing BMP than in the untreated defects. It was also higher in the groups with 10?mg of unsterilized reindeer BMP extract and rhBMP-2 than in the collagen-treated controls. Mechanical tests showed torsional stiffness of the bones to be higher in the group with 10?mg of unsterilized BMP extract than in the collagen group. The mean cross-sectional bone area measured by pQCT densitometry was higher in the rhBMP-2 group than in the collagen group. The mean bone density at the defect area was higher in the group with 10?mg of unsterilized BMP than in the rhBMP-2 group.

Interpretation?We conclude that both reindeer BMP extract and rhBMP-2 induced improved healing of the rabbit radius bone defects at the doses used. Gamma sterilization of reindeer BMP extract reduced osteoinductivity slightly, but not significantly.     

The effect of different mineral frames on ectopic bone formation in mouse hind leg muscles induced by native reindeer bone morphogenetic protein

Introduction Bone morphogenetic proteins (BMPs) require carrier material for slow release and framing material for osteoconduction.Materials and methods The effect of a frame on early bone formation induced by partially purified native reindeer BMP in composite implants containing 3 mg of BMP, type IV collagen and tricalcium phosphate (TCP/Col/BMP) or hydroxyapatite (HA/Col/BMP) or biphasic tricalcium phosphate-hydroxyapatite (TCP/HA/Col/BMP) or biocoral (NC/Col/BMP) was evaluated using a mouse hind leg muscle pouch model. Collagen with native reindeer BMP (Col/BMP) and corresponding implants without native reindeer BMP served as controls. Evaluation was done by incorporation of ⁴⁵Ca, radiographically and histologically 3 weeks after the implantation.Results None of the implants without native reindeer BMP were able to induce new bone visible on radiographs. The area of new bone formation in the Col/BMP (p=0.026) and TCP/HA/Col/BMP (p=0.012) groups was significantly greater than in the TCP/Col/BMP group. The optical density of the new bone area was significantly greater in the TCP/HA/Col/BMP group than in the TCP/Col/BMP (p=0.036) or Col/BMP (p=0.02) groups. ⁴⁵Ca incorporation was many times greater in all the groups containing native reindeer BMP than in the corresponding groups without BMP. In the Col/BMP (p=0.046) and TCP/HA/Col/BMP (p=0.046) groups, ⁴⁵Ca incorporation was significantly greater than in the TCP/Col/BMP group. No significant differences were found in any parameters between HA/Col/BMP and NC/Col/BMP groups and the other BMP-containing groups.Conclusions Hydroxyapatite, biocoral and biphasic tricalciumphosphate-hydroxyapatite are equally good as framing material for native reindeer BMP, while tricalciumphosphate is somewhat worse. Osteoinduction of native reindeer BMP works well with collagen alone.     

Effect of sterilization on bone morphogenetic protein

Demineralized bone matrix and bone morphogenetic protein have been used clinically to accelerate bone regeneration. However, the best method of sterilization has been the subject of controversy. Some investigators have used ethylene oxide, but others have reported that doses adequate for sterilization destroyed the osteoinductivity of demineralized bone matrix and that gamma irradiation was less harmful in this respect. We used partially purified bone morphogenetic protein and type-I collagen to investigate the effects of sterilization by ethylene oxide and gamma irradiation on the activity of bone morphogenetic protein. Osteoinductivity was reduced considerably after sterilization by gamma irradiation at 2.5 Mrad and by ethylene oxide at 37°C for 4 hours and at 55°C for 1 hour; however, the reduction induced by ethylene oxide at 29°C for 5 hours was about half of the control values. This study showed that ethylene oxide at 29°C for 5 hours can be used clinically for sterilization of bone morphogenetic protein. We also investigated the effect of gamma irradiation on bone morphogenetic protein and the collagen carrier separately and found that collagen was far more labile than bone morphogenetic protein.     

Influence of ethylene oxide sterilization on the activity of native reindeer bone morphogenetic protein

We studied the effects of ethylene oxide sterilization (Steri-Vac 4XL, temperature 29°C, exposure time 4 h 10 min, ethylene oxide concentration 860 mg/l) on the osteoinductivity of partially purified native reindeer bone morphogenetic protein (BMP) in a hind leg muscle pouch model of male NMRI mice. BMP was administered in implants containing 3 mg in a collagen carrier. Implants without sterilization and without BMP served as controls. New bone formation was evaluated based on the calcium yield, radiographic and histological examination 3 weeks after implantation. The implants without BMP were not able to induce new bone visible in radiographs. In the sterilized BMP group, the mean area of new bone was 35% (p=0.004) and density 32% (p=0.000) smaller than in the nonsterilized group. Calcium yield was 20% lower in the sterilized group than in the nonsterilized group, but this difference was not significant (p=0.22). It was many times lower in the group without BMP than in the above-mentioned groups (p=0,001). We conclude that ethylene oxide gas sterilization reduces the bone-forming activity of native reindeer BMP by one third.

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Résumé Nous avons étudié les effets de la stérilisation à loxyde déthylène (Steri-Vac 4XL, température 29ºC, temps dexposition 4 h, concentration de loxyde déthylène 860 mg/l) sur losteoinductivité de la proteine morphogénétique osseuse (BMP) du renne partiellement purifié dans un modèle fait par une bourse du muscle de la patte postérieure de la souris NMRI virile. La BMP a été administré par des implants qui contiennent 3 mg dans un porteur de collagène. Des implants sans stérilisation et sans BMP ont servi de contrôle. La néo- formation osseuse a été évaluée sur la formation de calcium, radiographiquement et histologiquement trois semaines après implantation. Les implants sans BMP nétaient pas capables dinduire un nouvel os visible sur les radiographies. Avec la BMP stérilisé la surface moyenne dos nouveau était 35% (p=0.004) et la densité 32% (p=0.000) plus petite que dans le groupe BMP non—stérilisé. La production de calcium était 20% inférieure dans le groupe BMP stérilisé que dans le groupe BMP non—stérilisé, mais cette différence nétait pas significative (p=0.22). Elle était plusieurs fois plus faible dans le groupe sans BMP que dans les groupes susmentionnés (p=0,001). Nous concluons que la stérilisation à loxyde déthylène réduit dun tiers lactivité ostéoformatrice de la BMP de renne.

     

The effect of various sterilization procedures on the osteoinductive properties of demineralized bone matrix]

To minimize potential infection following the transplantation of allogeneic bone, extremely rigorous selection of donors and careful processing and storage of samples are required. Other major problems related to allogeneic transplants, such as reduced osteogenic properties and immunological reactions, led to the development of demineralized bone matrix (DBM). This osteoinductive bone extract is largely free of antigens and is easy to produce. However, to eliminate the potential risk of infection, DBM should be sterilized prior to implantation. The purpose of this study was to investigate the influence of different sterilization techniques on the osteoinductive properties of DBM. A series of 76 cortical defects (drill holes) 0.6 cm in diameter in the tibiae of 11 Merino sheep were filled with DBM in addition to autogeneic and allogeneic cancellous bone. Prior to implantation DBM was sterilized by autoclaving, gamma irradiation, or application of ethylene oxide or ethyl alcohol. A further 12 drill holes were left empty as controls. The formation of new bone was examined 3 and 6 weeks postoperatively, using histological, fluorescent-optical and microradiographical techniques. The amount of newly formed bone was also quantified. Apart from autoclaved DBM all matrix grafts showed excellent new bone formation following sterilization, by far exceeding the formation with allogeneic cancellous bone.     

Fracture and fatigue properties of acrylic bone cement: the effects of mixing method, sterilization treatment, and molecular weight

The purpose of this study was to characterize the relative and combined effects of sterilization, molecular weight, and mixing method on the fracture and fatigue performance of acrylic bone cement. Palacos R brand bone cement powder was sterilized using ethylene oxide gas (EtO) or gamma irradiation. Nonsterile material was used as a control. Molecular weights of the bone-cement powders and cured cements were measured using gel permeation chromatography. Hand and vacuum mixing were employed to mold single edge-notched bend specimens for fracture toughness testing. Molded dog-bone specimens were used for fatigue tests. Electron microscopy was used to study fracture mechanisms. Analysis of variance and Student t-tests were used to compare fracture and fatigue performance between sterilization and mixing groups. Our results indicate that vacuum mixing improved significantly the fracture and fatigue resistance (P<.05, P<.07) over hand mixing in radiation-sterilized and EtO-sterilized groups. In vacuum-mixed cement, the degradation in molecular weight resulting from gamma irradiation decreased fracture resistance significantly when compared with EtO sterilization and control (P<.05). A corresponding decrease in fatigue resistance was observed in the cement that was degraded severely by a radiation dose of 10 MRad (P<.05). In contrast, EtO sterilization did not result in a significantly different fracture resistance when compared with unsterilized controls for vacuum-mixed cement (P>.1). For hand-mixed cement, fracture and fatigue resistance appeared to be independent of sterilization method. This independence is believed to be the result of higher porosity that compromised the mechanical properties and obscures any effect of sterilization. Our results indicate that a combination of nonionizing sterilization and vacuum mixing resulted in the best mechanical performance and is most likely to contribute to enhanced longevity in vivo.     

Ethylene oxide sterilization of bone grafts: Residual gas concentration and fibroblast toxicity

We examined the concentration of ethylene oxide in bone allografts after gas sterilization. Chips of the human femoral head were investigated. Residual gas concentration was determined by gas chromatography after the bone chips had been subjected to defatting and freeze-drying, followed by ethylene oxide gas sterilization. Bones were prepared in various ways in an attempt to reduce the concentration of residual ethylene oxide. The concentration was higher when gas sterilization was performed before freeze-drying than when it was done afterwards. An experiment performed with fibroblasts showed the high toxicity of residual ethylene oxide in bone chips, even when the concentration was very low. The growth of fibroblast was reduced more in medium which had been shaken with bones sterilized with ethylene oxide before freeze-drying than in medium which had been shaken with bones sterilized after freeze-drying. The higher residual ethylene oxide concentrations resulted in a decrease in fibroblastic culture activity. Our experiment showed the importance of reducing the residual ethylene oxide gas concentration. Defatting and freeze-drying result in lower residual ethylene oxide concentrations.     

Einfluss von Prozessierung und Sterilisation auf die Festigkeit von Pins aus boviner Tibiakompakta

In a biomechanical study pins made of xenogenous cortical bone were tested in vitro. Forty pins of 3 mm diameter and 60 mm length were made of eight different cattle tibiae and allocated to five different treatment groups. Freeze-dried pins served as control group. Pins of the second group were preserved in concentrated sodium chloride solution and defatted with acetone (Tuto-plast processing). Pins of groups three to five were treated with sodium chloride and acetone and afterwards sterilized by different means (ethylene oxide, autoclavation, or gamma radiation). All pins were subjected to a three-point-bending test and a shear test. We found that bending strength and shearing strength were most increased after sodium chloride and acetone treatment, whereas after sterilization with ethylene oxide or autoclaving, the stability of the pins was similar to the control group. The stability was considerably diminished after gamma radiation. Taking into account possible toxic side effects of ethylene oxide, we conclude that Tutoplast processing followed by autoclavation presents a reliable preparation method for the clinical use of implants made of bovine cortical bone.     

Reindeer bone extract can heal the critical-size rat femur defect

Bone extract from reindeer induces new ectopic bone formation (BF) in muscle pouches, but its feasibility in experimental bone lesions has not been evaluated. We investigated the effects of implants, containing 2, 5, 15, 20 or 50 mg of reindeer bone extract in a collagen carrier, on the healing of 8-mm femur defects in 78 rats. We used 30 μg of recombinant human bone morphogenetic protein-2 (rhBMP-2) in a collagen carrier, collagen and untreated defects as controls. Bone healing was evaluated with radiographs, peripheral quantitative computed tomography (pQCT), biomechanics and histology. In comparison with empty defects, the groups receiving bone extracts showed more BF at three weeks and had better bone union (BU), larger mean cross-sectional bone area at the defect site in groups receiving higher doses of extract, showed greater torsional stiffness of the bones and higher maximum breaking load of bones at six weeks. In comparison to all other groups, in the rhBMP-2 group, BF and BU were best at the three- and six-week follow-up, bone area was largest and mechanical test results were best. Although rhBMP-2 is superior for new bone regeneration, native reindeer bone extract is also effective in the six-week follow-up period.     

Fracture and fatigue properties of acrylic bone cement

The purpose of this study was to characterize the relative and combined effects of sterilization, molecular weight, and mixing method on the fracture and fatigue performance of acrylic bone cement. Palacos® R brand bone cement powder was sterilized using ethylene oxide gas (EtO) or gamma irradiation. Nonsterile material was used as a control. Molecular weights of the bone-cement powders and cured cements were measured using gel permeation chromatography. Hand and vacuum mixing were employed to mold single edge-notched bend specimens for fracture toughness testing. Molded dog-bone specimens were used for fatigue tests. Electron microscopy was used to study fracture mechanisms. Analysis of variance and Student t-tests were used to compare fracture and fatigue performance between sterilization and mixing groups. Our results indicate that vacuum mixing improved significantly the fracture and fatigue resistance (P < .05, P < .07) over hand mixing in radiation-sterilized and EtO-sterilized groups. In vacuum-mixed cement, the degradation in molecular weight resulting from gamma irradiation decreased fracture resistance significantly when compared with EtO sterilization and control (P < .05). A corresponding decrease in fatigue resistance was observed in the cement that was degraded severely by a radiation dose of 10 MRad (P < .05). In contrast, EtO sterilization did not result in a significantly different fracture resistance when compared with unsterilized controls for vacuum-mixed cement (P > .1). For hand-mixed cement, fracture and fatigue resistance appeared to be independent of sterilization method. This independence is believed to be the result of higher porosity that compromised the mechanical properties and obscures any effect of sterilization. Our results indicate that a combination of nonionizing sterilization and vacuum mixing resulted in the best mechanical performance and is most likely to contribute to enhanced longevity in vivo.     

聚羟基丁酸酯可吸收缝线灭菌方法的实验研究

目的：研究不同的灭菌方法对聚羟基丁酸酯（PHB）可吸收缝线的降解性和力学特性的影响。方法：将聚羟基丁酸酯（PHB）可吸收缝线进行酒精浸泡、环氧乙烷、紫外线照射三种方法进行灭菌处理后,用细菌培养检测灭菌效果,用粘度法测定聚合物分子量从而观察缝线的降解性,用拉伸试验测定缝线的力学特性。结果：①酒精浸泡灭菌组有10%检出细菌,环氧乙烷及紫外线灭菌组未检出细菌;②紫外线照射灭菌和酒精浸泡灭菌组可使缝线黏度下降并具有显著性差异,环氧乙烷对缝线黏度下降的影响没有显著性差异;③经酒精和紫外线灭菌后缝线的断裂强度降低明显,差异具有显著性,经环氧乙烷灭菌后缝线的断裂强度降低无显著性差异。经紫外线灭菌后缝线的断裂伸长率明显降低,差异具有显著性,经酒精和环氧乙烷灭菌后缝线的断裂伸长率无明显降低。结论：环氧乙烷灭菌对PHB可吸收缝线的降解性和力学特性影响较小,是PHB可吸收缝线较理想的灭菌方法。     

辐照中脱矿骨基质粒径对胶原结构影响的实验研究

目的探讨不同粒径大小对γ辐照中脱钙骨基质(demineralized bone matrix,DBM)中胶原结构的影响以及辐照保护剂的有效性。方法取同一供体的冻干皮质骨,依据Urist改良法制备不同粒径的(0.5~1.0 mm、1.2~2.8 mm、3.3~4.7 mm及5.7~7.0 mm)DBM样品,按照不同剂量分为:0 kGy、15 kGy、25 kGy及25 kGy(辐照保护剂),真空密封后储存于-80℃冰箱待用。通过扫描电镜观察胶原表面形态,大体观察胶原表面结构损伤的程度;将样品按照0.2 g/ml生理盐水比例在50℃条件下72 h,利用浸提液颜色深度观察胶原被辐照损伤的程度;使用2,4-二硝基苯肼(吸光光度计法)测定样品中羰基含量;十二烷基硫酸钠聚丙烯酰胺钠凝胶电泳法(Sodium dodecyl sulfatepolyacrylamide gel electrophoresis,SDS-PAGE)测定样品中胶原分子量的变化;利用差示热量扫描法(differential scanning calorimetry,DSC)检测样品热变性温度以观察胶原热稳定性。结果样品浸提液颜色与γ辐照剂量相关度较高,未辐照样品浸提液颜色清亮,而在同粒径下随辐照剂量加大浸提液黄色逐渐加深,5.7~7.0 mm粒径组颜色相对较浅;25 kGy组相比于25 kGy+保护剂组浸提液颜色加深。扫描电镜观察到γ辐照导致胶原结构紊乱,纤维断裂,随着辐照剂量增大损伤区域增多,当粒径增大时,损伤区域有减少的趋势;相比于25 kGy组,25 kGy+保护剂组胶原结构性破坏减少。差示热量扫描法得出样品热交换曲线,随着粒径增大,热变性温度有增高的趋势,粒径间对比有统计学差异(F=189.4,P<0.001);同粒径间差异不明显。SDS-PAGE发现同粒径下γ辐照剂量愈大,胶原分子量愈小;同辐照条件下随粒径较小,高分子量胶原含量减少明显;225 kGy+保护剂组相比于25 kGy组,高分子量增多。羰基含量结果显示在同一粒径下,γ辐照使羰基含量增多,0.5~1.0 mm组(F=13.631,P=0.002),1.2~2.8 mm组(F=6.390,P=0.016),3.3~4.7 mm组(F=5.630,P=0.023),5.7~7.0 mm组(F=4.150,P=0.048)的差异均有统计学意义,不同粒径间随着粒径增大羰基含量逐渐减小但差异统计学意义(F=0.560,P=0.650)。结论γ辐照与胶原的氧化损伤具有明显的剂量反应关系,随着γ辐照剂量的增加,胶原损伤程度逐渐增加;DBM的粒径大小影响着胶原对γ辐照的敏感度,随着粒径的减小,DBM颗粒更易被γ辐照损伤;辐照保护剂在辐照过程中对胶原有一定程度的保护作用。     

Mechanical strength of cortical allografts with gamma radiation versus ethylene oxide sterilization

We investigated the effects of gamma irradiation versus ethylene oxide (ETO) sterilization on the mechanical strength of cortical bone grafts. Tibias were collected from cadavers of mature goats. Sixty test specimens were randomized into four groups: fresh (no processing), frozen (freezing at -70 degrees C), gamma-irradiated, and ETO-sterilized specimens. Torsion, three-point bending, and compression testing were separately performed with a material testing machine. Parameters studied included maximum stress, strain, deflection, extension, load, shear modulus, and E-modulus. Compared with findings for the fresh specimens, findings were as follows for gamma-irradiated specimens: maximal shear modulus, reduced by 48%; shear stress, by 55%; deflection, by 71%; bending stress, by 51%; bending strain, by 74%; extension, by 60%; and compression strain, by 50%. However, there were no reductions in those parameters for the frozen specimens or the ETO-sterilized specimens. These findings confirm that shear, bending, and compression strength of cortical allografts are weakened by gamma irradiation at room temperature. To maintain optimum mechanical properties, ETO sterilization of allografts is better than gamma sterilization, especially for cortical bone, because it is usually used in load-bearing settings.     

Ethylene oxide does not extinguish the osteoinductive capacity of demineralized bone: A reappraisal in rats

We examined the influence of ethylene oxide (EO) and gamma irradiation on the osteoinductive capacity of demineralized bone. Demineralized bone powder prepared from Wistar rats was exposed to EO (55 °C or 40 °C) or gamma irradiation (25 KGy) or was preserved in ethanol. Sterilely-prepared bones served as controls. The powder was packed in a gelatin capsule and implanted for 6 weeks in muscles of 6-week-old female rats. Exposure of demineralized bone particles to EO 55 °C resulted in an almost complete loss of osteoinductivity. Irradiated bones lost about 40% of their osteoinductive capacity, while sterilization with EO at 40 °C resulted in only a slight alteration of the osteoinductivity, as assessed by the recovered weight ratio, calcium content, alkaline phosphatase activity measurements and histo-morphometry. Ethanol treatment had no influence on the new bone yield when compared to controls.

As EO exposure at 40 °C is a true sterilization procedure, it can be recommended in a clinical setting for its small effect on osteoinductive capacity as assessed experimentally in rats.     

Effect of hydrogen peroxide on osteoinduction by demineralized bone

The osteoinductive capacity of demineralized bone matrix (DBM) has led to wide use of this material for surgical reconstruction. Preparation of DBM often includes sterilization with ethylene oxide, disinfection with various chemical agents, or irradiation. Exposure to hydrogen peroxide (H2O2) is used for both sterilization and bleaching of bone, the latter primarily for cosmetic reasons. We investigated the effect of H2O2, on the osteoinductive capacity of DBM. Cortical bone implants prepared from rat femurs were placed into 3% H2O2 solution. Control specimens were not exposed to H2O2. Bones were then lipid-extracted, demineralized, sterilized with ethylene oxide, and freeze-dried in an identical manner. Allografts were implanted into rat hosts for 1 to 3 weeks. Osteoinduction proceeded rapidly in implants not exposed to H2O2, with chondrocytes and new bone appearing in the implant. After 3 weeks, perforations in the implant were largely replaced with new bone. In contrast, osteoinduction did not occur in implants treated with H2O2. Perforations in H2O2-treated implants were filled with vascularized fibrous tissue, but no cartilage or bone. These findings reveal that H2O2 used for disinfection or bleaching of DBM can abolish its osteoinductive capacity in rats.     

Increase in early polyethylene wear after sterilization with ethylene oxide

We evaluated polyethylene wear by measuring femoral head penetration in 201 THA (median age 62 (31-81) years, 117 women) extracted from 5 randomized studies aimed to assess various fixation principles. There were 30 cemented all-polyethylene Lubinus cups sterilized by gamma irradiation in a reduced oxygen environment, 65 porous-coated Trilogy cups with liners gamma-sterilized in inert gas. Moreover, 37 cemented cups were sterilized with ethylene oxide (Reflection all-poly) and 69 porous-coated cups had liners sterilized in ethylene oxide (Reflection). 28 mm femoral heads were used in all cups. The patients were followed with repeated radiostereometric measurements (RSA) up to 2 years. The activity level of the patients was evaluated by a questionnaire. After 2 years, cups with polyethylene sterilized in EtO had almost twice the proximal and 3D penetration rates, as compared with gamma-sterilized polyethylene. The penetration did not differ between the gamma-irradiated designs. Using stepwise linear regression analysis, we found that the type of sterilization, age and weight were the most important predictors and that they determined the direction of the proximal penetration rate. Activity score, male gender and proximal migration of the cup had little effect. The accelerated wear observed with the EtO-sterilized polyethylene causes concerns about long-term problems and especially in younger patients.     

Increase in early polyethylene wear after sterilization with ethylene oxide: radiostereometric analyses of 201 total hips

We evaluated polyethylene wear by measuring femoral head penetration in 201 THA (median age 62 (31-81) years, 117 women) extracted from 5 randomized studies aimed to assess various fixation principles. There were 30 cemented all-polyethylene Lubinus cups sterilized by gamma irradiation in a reduced oxygen environment, 65 porous-coated Trilogy cups with liners gamma-sterilized in inert gas. Moreover, 37 cemented cups were sterilized with ethylene oxide (Reflection all-poly) and 69 porous-coated cups had liners sterilized in ethylene oxide (Reflection). 28 mm femoral heads were used in all cups. The patients were followed with repeated radiostereometric measurements (RSA) up to 2 years. The activity level of the patients was evaluated by a questionnaire. After 2 years, cups with polyethylene sterilized in EtO had almost twice the proximal and 3D penetration rates, as compared with gamma-sterilized polyethylene. The penetration did not differ between the gamma-irradiated designs. Using stepwise linear regression analysis, we found that the type of sterilization, age and weight were the most important predictors and that they determined the direction of the proximal penetration rate. Activity score, male gender and proximal migration of the cup had little effect. The accelerated wear observed with the EtO-sterilized polyethylene causes concerns about long-term problems and especially in younger patients.     

Increase in early polyethylene wear after sterilization with ethylene oxideRadiostereometric analyses of 201 total hips

We evaluated polyethylene wear by measuring femoral head penetration in 201 THA (median age 62 (31-81) years, 117 women) extracted from 5 randomized studies aimed to assess various fixation principles. There were 30 cemented all-polyethylene Lubinus cups sterilized by gamma irradiation in a reduced oxygen environment, 65 porous-coated Trilogy cups with liners gamma-sterilized in inert gas. Moreover, 37 cemented cups were sterilized with ethylene oxide (Reflection all-poly) and 69 porous-coated cups had liners sterilized in ethylene oxide (Reflection). 28 mm femoral heads were used in all cups. The patients were followed with repeated radiostereometric measurements (RSA) up to 2 years. The activity level of the patients was evaluated by a questionnaire. After 2 years, cups with polyethylene sterilized in EtO had almost twice the proximal and 3D penetration rates, as compared with gamma-sterilized polyethylene. The penetration did not differ between the gamma-irradiated designs. Using stepwise linear regression analysis, we found that the type of sterilization, age and weight were the most important predictors and that they determined the direction of the proximal penetration rate. Activity score, male gender and proximal migration of the cup had little effect. The accelerated wear observed with the EtO-sterilized polyethylene causes concerns about long-term problems and especially in younger patients.