人工关节假体不同材料及材料表面粗糙度对表皮葡萄球菌粘附能力的影响

目的探讨人工关节假体材料及表面粗糙度对表皮葡萄球菌粘附能力的影响。方法制作超高分子聚乙烯、钛合金和钴铬钼合金试样，表皮葡萄球菌经FITC标记，人工关节材料试样消毒后接种FITC标记的表皮葡萄球菌，试样表面分为光滑表面和粗糙表面，每组各6个试样，将含有细菌和试样的24孔板在37℃下孵育30min后，用荧光显微镜观察，试样用扫描电镜观察。结果对于光滑的人工关节常用材料表面，表皮葡萄球菌对超高分子聚乙烯（UHMWPE）的粘附能力显著高于钛合金和钴铬钼合金（P〈0．001），对钴铬钼合金的粘附能力要高于钛合金（P〈0．05）；粗糙的超高分子聚乙烯和钴铬钼合金表面比光滑的表面更易引起表皮葡萄球菌的粘附（P〈0．01），而细菌对粗糙钛合金的粘附仅轻微高于光滑钛合金（P〉0．05）。荧光照相观察及扫描电镜观察显示细菌在粗糙表面的划痕内聚集粘附。结论本研究结果表明细菌对人工关节材料表面的粘附能力不但取决于细菌本身，也和材料性质和表面粗糙度有关。     

Adhesion of Staphylococcus to orthopaedic metals, an in vivo study.

This study describes a new model of biofilm study in rabbits. The primary focus of this study was to assess biofilm adhesion to orthopaedic metals in their first 48 h in a femoral intramedullary implantation model. Two previous inoculation methods i.e. that of pre- and direct inoculation were studied with two bacterial isolates namely Staphylococcus aureus and epidermidis, on titanium and stainless steel metallic implants. A method of sonication and log dilution/plating was used to assess biofilm bacteria adhering to implants. Silver coated metals were then compared with their respective control metals in the new model. The direct inoculation model gave larger and more reproducible biofilm adhesion to implanted metals. Staphylococcus epidermidis shows lower adhesion ability to metals, and biofilms adhere in greater numbers to stainless steel over titanium. Silver coated metals show no statistical difference over control metals when exposed to orthopaedic biofilms.     

Effect of surface topography on removal of cortical bone screws in a novel sheep model

Difficulty in removing implants used in trauma patients can be a complication, and increased bone–implant adhesion likely is a major contributing factor. In vitro studies have shown that surface morphology of implant materials has the ability to influence cellular responses, with polished surfaces decreasing the potential for mineralization. This study examined the effect of polishing commercially pure titanium (cpTi) and the titanium alloy TAN on the removal torque and percentage bone–implant contact in cortical and cancellous bone of sheep. Polishing had a significant effect on both removal torque and percentage bone–implant contact, with the polished implants demonstrating a lower removal torque in both cortical and cancellous bone. Polished cpTi and stainless steel were similar in terms of surface roughness and removal torque. However, polished TAN, which was not as smooth as polished cpTi, did not show the same low level for reducing removal torque. Improved polishing of TAN should reduce the removal torque further. The results of the study show that polishing is promising in improving the ease of implant removal after fracture fixation and repair. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:1377–1383, 2008     

Relative contributions of chemistry and topography to the osseointegration of hydroxyapatite coatings

The purpose of the current study was to ascertain the relative contributions of surface chemistry and topography to the osseointegration of hydroxyapatite-coated implants. A canine femoral intramedullary implant model was used to compare the osseous response to commercially pure titanium implants that were either polished, grit-blasted, plasma-sprayed with hydroxyapatite, or plasma-sprayed with hydroxyapatite and masked with a very thin layer of titanium using physical vapor deposition (titanium mask). The titanium mask isolated the chemistry of the underlying hydroxyapatite layer without functionally changing its surface topography and morphologic features. At 12 weeks, the bone-implant specimens were prepared for undecalcified thin section histologic evaluation and serial transverse sections were quantified with backscattered scanning electron microscopy for the percentage of bone apposition to the implant surface. Bone apposition averaged 3% for the polished implants and 23% for the grit-blasted implants. Bone apposition to the hydroxyapatite-coated implants averaged 74% whereas bone apposition to the titanium mask implants averaged 59%. Although there was significantly greater osseointegration with the hydroxyapatite-coated implants, 80% of the maximum bone forming response to the implant surfaces developed with the titanium mask implants. This simple, controlled experiment revealed that topography is the dominant factor governing bone apposition to hydroxyapatite-coated implants.     

Role of fibronectin in staphylococcal adhesion to metallic surfaces used as models of orthopaedic devices

Staphylococcal infection of various prosthetic and internal fixation devices is a major complication associated with orthopaedic surgery. This study investigated the role of the host protein fibronectin in promoting adhesion of Staphylococcus aureus and Staphylococcus epidermidis to metallic surfaces representing materials used for orthopaedic devices. Pure human fibronectin was adsorbed in vitro onto coverslips (0.8 × 0.8 cm) of stainless steel, pure titanium, or titanium-aluminum-niobium alloy. In vitro bacterial adhesion was promoted more strongly by the metallic surfaces coated with fibronectin than by albumin-coated controls for two strains of S. aureus and one strain of S. epidermidis. Furthermore, with the fibronectin-coated coverslips, bacterial adhesion to titanium alloy was significantly greater than adhesion to stainless steel. Adhesion of the three staphylococcal strains was promoted more strongly by coverslips explanted from the subcutaneous space of guinea pigs and tested under similar conditions than by albumin-coated controls. Incubation of either in vitro fibronectin-coated or explanted metallic coverslips with anti-fibronectin antibodies produced a significant decrease in staphylococcal adhesion. These results suggest that the presence of fibronectin on the surface of implanted metallic devices is an important determinant of colonization of orthopaedic biomaterials by staphylococi.     

脊柱结核内固定的生物学基础

目的观察结核杆菌与不同内固定材料的粘附情况,以期初步探讨在脊柱结核病灶清除后植入内固定选择何种材料的问题。方法在结核杆菌的菌液分别加入四种不同的内固定材料（不锈钢、钛、钛合金、聚醚醚酮）,通过碘-125标记测量,比较细菌与材料之间的粘附情况。结果四种材料中,细菌在聚醚醚酮上的粘附最多,在纯钛上粘附最少,在不锈钢的粘附多于钛合金（P〈0.05）。结论在脊柱结核患者内固定材料的选择上,以纯钛为首选,钛合金次之,碳纤维材料慎用。     

结核分枝杆菌对材料粘附能力的体外实验研究

目的：通过体外实验观察结核分枝杆菌对内植物材料的粘附情况，从细菌粘附角度出发探讨脊柱结核内固定术的安全性问题，方法：以表皮葡萄球菌为对照，在表皮葡萄球菌、结核分枝杆菌菌液中分别加人不同材料，扫描电镜观察，比较不同细菌对不同材料(钛合金、不锈钢)、不同表面(光滑面、粗糙面)的粘附情况。结果：结核分枝杆菌对两种材料的粘附均较表皮葡萄球菌少，粗糙表面所粘附的细菌量较光滑面多。结论：结核分枝杆菌对内植物材料的低粘附性可能是临床脊柱结核内固定术安全的原因之一。     

Difference in metallic wear distribution released from commercially pure titanium compared with stainless steel plates

INTRODUCTION: Stainless steel and commercially pure titanium are widely used materials in orthopedic implants. However, it is still being controversially discussed whether there are significant differences in tissue reaction and metallic release, which should result in a recommendation for preferred use in clinical practice. MATERIALS AND METHODS: A comparative study was performed using 14 stainless steel and 8 commercially pure titanium plates retrieved after a 12-month implantation period. To avoid contamination of the tissue with the elements under investigation, surgical instruments made of zirconium dioxide were used. The tissue samples were analyzed histologically and by inductively coupled plasma atomic emission spectrometry (ICP-AES) for accumulation of the metals Fe, Cr, Mo, Ni, and Ti in the local tissues. Implant corrosion was determined by the use of scanning electron microscopy (SEM). RESULTS: With grades 2 or higher in 9 implants, steel plates revealed a higher extent of corrosion in the SEM compared with titanium, where only one implant showed corrosion grade 2. Metal uptake of all measured ions (Fe, Cr, Mo, Ni) was significantly increased after stainless steel implantation, whereas titanium revealed only high concentrations for Ti. For the two implant materials, a different distribution of the accumulated metals was found by histological examination. Whereas specimens after steel implantation revealed a diffuse siderosis of connective tissue cells, those after titanium exhibited occasionally a focal siderosis due to implantation-associated bleeding. Neither titanium- nor stainless steel-loaded tissues revealed any signs of foreign-body reaction. CONCLUSION: We conclude from the increased release of toxic, allergic, and potentially carcinogenic ions adjacent to stainless steel that commercially pure Ti should be treated as the preferred material for osteosyntheses if a removal of the implant is not intended. However, neither material provoked a foreign-body reaction in the local tissues, thus cpTi cannot be recommend as the 'golden standard' for osteosynthesis material in general.     

Striated muscle microvascular response to implants with sol-gel calcium phosphate coating. A comparative in vivo study

AIM: Local microvascular perfusion plays an important role in reparative processes and the pathogenesis of infection. The impairment of skeletal muscle microcirculation by a biomaterial may therefore have profound consequences. The aim of our study was to determine whether the biological acceptance of the widely utilised implant material stainless steel can be improved by a coating of sol-gel calcium phosphate. METHODS: Using the hamster dorsal skinfold chamber preparation and intravital microscopy, we quantified nutritive perfusion and leukocyte-endothelium interaction in skeletal muscle after implantation of sol-gel calcium phosphate-coated stainless steel- and commercial pure titanium implants, and compared these results to those obtained with uncoated stainless steel and titanium. RESULTS: Within the first 24 h after implantation, animals with calcium phosphate coated stainless steel showed a significantly lower inflammatory response than did those with an uncoated stainless steel implant. After 24 h the quantified microcirculatory parameters deteriorated for animals with a calcium phosphate-coated stainless steel plate, indicating that, for as yet unknown reasons, the shielding mechanism of the calcium phosphate seems to deteriorate. Although not as inert as pure titanium, we found a relatively low inflammatory response for calcium phosphate coated titanium over the whole observation period, suggesting that the coating as such is well tolerated by the skeletal muscle microcirculation. CONCLUSIONS: Our in vivo results suggest that the biological acceptance of a conventional stainless steel implant can be improved over a short term by a sol-gel coating of calcium phosphate. Concerning tolerance by the local vascular system, commercially pure titanium currently remains unsurpassed.     

Osseointegration of metallic implants. I. Light microscopy in the rabbit

Thirty-eight adult albino rabbits received one implant of pure titanium and one implant of another, test, material in each tibia. The test materials were titanium-aluminum-vanadium alloy, chrome-cobalt alloy, and stainless steel. Observation times were 4 months and 11 months. Light microscopy of the interface revealed a direct contact between bone and implant surface (osseointegration) in 73 of the 76 cases. The exceptions were two implants of pure titanium and one of stainless steel. Thus, given identical healing conditions, the modern implant metals were accepted by the bone in the same way. It is suggested that osseointegration should be regarded not as an exclusive reaction to a specific implant material, but as the expression of a nonspecific and basic healing potential in bone.     

Osseointegration of metallic implants: I. Light microscopy in the rabbit

Thirty-eight adult albino rabbits received one implant of pure titanium and one implant of another, test, material in each tibia. The test materials were titanium-aluminum-vanadium alloy, chrome-cobalt alloy, and stainless steel. Observation times were 4 months and 11 months.

Light microscopy of the interface revealed a direct contact between bone and implant surface (osseointegration) in 73 of the 76 cases. The exceptions were two implants of pure titanium and one of stainless steel. Thus, given identical healing conditions, the modern implant metals were accepted by the bone in the same way.

It is suggested that osseointegration should be regarded not as an exclusive reaction to a specific implant material, but as the expression of a nonspecific and basic healing potential in bone.     

Osteoblast adhesion to orthopaedic implant alloys: Effects of cell adhesion molecules and diamond-like carbon coating

In total joint arthroplasty, long-term outcomes depend in part on the biocompatibility of implant alloys. This study analyzed effects of surface finish and diamond-like carbon coating on osteoblast cell adhesion to polished titanium-aluminum-vanadium and polished or grit-blasted cobalt-chromium-molybdenum alloys. Osteoblast binding was tested in the presence and absence of the cell adhesion proteins fibronectin, laminin, fibrinogen, and vitronectin and was quantified by measurement of DNA content. Although adherence occurred in serum-free medium, maximal osteoblast binding required serum and was similar for titanium and cobalt alloys at 2 and 12 hours. With the grit-blasted cobalt alloy, cell binding was reduced 48% (p < 0.05) by 24 hours. Coating the alloys with diamond-like carbon did not alter osteoblast adhesion, whereas fibronectin pretreatment increased cell binding 2.6-fold (p < 0.05). In contrast, fibrinogen, vitronectin, and laminin did not enhance cell adhesion. These results support the hypothesis that cell adhesion proteins can modify cell binding to orthopaedic alloys. Although osteoblast binding was not affected by the presence of diamond-like carbon, this coating substance may influence other longer term processes, such as bone formation, and deserves further study.     

Is galvanic corrosion between titanium alloy and stainless steel spinal implants a clinical concern?

BACKGROUND CONTEXT: Surgeons are hesitant to mix components made of differing metal classes for fear of galvanic corrosion complications. However, in vitro studies have failed to show a significant potential for galvanic corrosion between titanium and stainless steel, the two primary metallic alloys used for spinal implants. Galvanic corrosion resulting from metal mixing has not been described in the literature for spinal implant systems. PURPOSE: To determine whether galvanic potential significantly affects in vitro corrosion of titanium and stainless steel spinal implant components during cyclical compression bending. STUDY DESIGN/SETTING: Bilateral spinal implant constructs consisting of pedicle screws, slotted connectors, 6.35-mm diameter rods and a transverse rod connector assembled in polyethylene test blocks were tested in vitro. Two constructs had stainless steel rods with mixed stainless steel (SS-SS) and titanium (SS-Ti) components, and two constructs had titanium rods with mixed stainless steel (Ti-SS) and titanium (Ti-Ti) components. METHODS: Each construct was immersed in phosphate-buffered saline (pH 7.4) at 37 C and tested in cyclic compression bending using a sinusoidal load-controlling function with a peak load of 300 N and a frequency of 5 Hz until a level of 5 million cycles was reached. The samples were then removed and analyzed visually for evidence of corrosion. In addition, scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) were used to evaluate the extent of corrosion at the interconnections. RESULTS: None of the constructs failed during testing. Gross observation of the implant components after disassembly revealed that no corrosion had occurred on the surface of the implants that had not been in contact with another component. The Ti-Ti interfaces showed some minor signs of corrosion only detectable using SEM and EDS. The greatest amount of corrosion occurred at the SS-SS interfaces and was qualitatively less at the SS-Ti and Ti-SS interfaces. CONCLUSIONS: The results from this study indicate that when loaded dynamically in saline, stainless steel implant components have a greater susceptibility to corrosion than titanium. Furthermore, the galvanic potential between the dissimilar metals does not cause a discernible effect on the corrosion of either. Although the mixture of titanium alloy with stainless steel is not advocated, the results of this study suggest that galvanic corrosion is less pronounced in SS-Ti mixed interfaces than in all stainless steel constructs.     

Corrosion Behavior of Tantalum-Coated Cobalt–Chromium Modular Necks Compared to Titanium Modular Necks in a Simulator Test

This study compared the corrosion behavior of tantalum-coated cobalt–chromium modular necks with that of titanium alloy modular necks at their junction to titanium-alloy femoral stem. Tests were performed in a dry assembly and two wet assemblies, one contaminated with calf serum and the other contaminated with calf serum and bone particles. Whereas the titanium modular neck tested in the dry assembly showed no signs of corrosion, the titanium modular necks tested in both wet assemblies showed marked depositions and corrosive attacks. By contrast, the tantalum-coated cobalt–chromium modular necks showed no traces of corrosion or chemical attack in any of the three assemblies. This study confirms the protective effect of tantalum coating the taper region of cobalt–chromium modular neck components, suggesting that the use of tantalum may reduce the risk of implant failure due to corrosion.     

The effects of implant composition on extensor tenosynovitis in a canine distal radius fracture model

PURPOSE: Dorsal plating of distal radius fractures with titanium plates has resulted in clinically observed tenosynovitis and tendon rupture. The goal of this study was to investigate whether titanium-based implants result in more extensor tendon inflammation than matched stainless-steel implants in a canine fracture model. METHODS: An osteotomy was created in the distal radius of 18 beagles and fixed with 2.7-mm 4-hole plates composed of commercially pure titanium, titanium alloy (Ti-Al6-V4), or 316L stainless steel. Animals were killed at an average of 4 months. Tendon gliding was assessed by applying a force at the extensor musculotendinous junction and noting gliding. Histologic grading (mild, moderate, severe) was based on cellular hypertrophy, hyperplasia, and leukocytic infiltration. RESULTS: Tendons glided freely in 100% stainless-steel specimens, 75% of titanium alloy, and 43% of commercially pure titanium groups. A severe inflammatory reaction was identified in 60% of the titanium alloy (Ti-A16-V4) group, 57% of the pure titanium group, and 0% of the stainless-steel group. CONCLUSIONS: Dorsal plating of the canine radius with commercially pure titanium or titanium alloy implants produced a greater inflammatory peritendinous response than matched stainless-steel implants.     

Metallic biomaterials TiN-coated: corrosion analysis and biocompatibility

Corrosion processes due to contact with the physiological environment should be avoided or minimized in orthopedic implants. Four metallic substrates frequently used as biomaterials: pure Ti, Ti-6Al-4V alloy, ASTM F138 stainless steel, and Co-Cr-Mo alloy, were coated with TiN using the physical vapor deposition (PVD) technique. These coatings have been screened by polarization curves in physiological solutions. TiN prepared by PVD is efficient as coating for stainless steel. On titanium and alloy there are no benefits concerning the corrosion resistance compared to the bare Ti-materials. TiN coatings have been screened according to ISO 10993 standard tests for biocompatibility and exhibited no cytotoxicity, dermal irritation, or acute systemic toxicity response.     

A fatigue life analysis of small fragment screws

OBJECTIVES: To conduct a comparative fatigue analysis of several commonly used small fragment screws. DESIGN: Biomechanical laboratory study. SETTING: Research laboratory. MAIN OUTCOME MEASUREMENTS: A fatigue life analysis of seven different types of small fragment screws was conducted using a Wohler fatigue-testing machine. Four different types of 3.5-millimeter cortical screws were subjected to fatigue analysis. These included solid stainless steel screws from Synthes Ltd. (core diameter 2.4 millimeters), Zimmer Inc. (core diameter 2.4 millimeter), and Smith and Nephew Richards Inc. (core diameter 2.4 millimeters) and cannulated stainless steel screws from Synthes Ltd. (core diameter 2.5 millimeters). In addition, three types of 4.0-millimeter cancellous screws were tested. These included stainless steel screws from Synthes Ltd. (core diameter 1.9 millimeters), titanium screws from Synthes Ltd. (core diameter 2.0 millimeters), and titanium alloy screws from DePuy-Ace (core diameter 2.8 millimeters). Fatigue lives, as reflected by mean cycles to failure, were compared. RESULTS: The four types of cortical screws had longer fatigue lives than the Synthes cancellous screws did ( p < 0.001) but shorter fatigue lives than the DePuy-Ace cancellous screws did ( p < 0.0001). Among the cortical screws, the cannulated and solid Synthes screws and the solid Zimmer screws did not differ statistically. The Smith and Nephew Richards cortical screws failed at statistically fewer cycles than the Synthes solid and cannulated cortical screws did ( p < 0.003) but did not statistically differ from the Zimmer screws. The DePuy-Ace titanium alloy cancellous screw had the longest fatigue life of the tested implants by a large margin ( p < 0.0001). The Synthes pure titanium and stainless steel cancellous screws did not significantly differ. CONCLUSIONS: This analysis supports core diameter as the principal factor determining fatigue life as the results paralleled implant geometry. This design modification to improve bending and fatigue strength may come at a price to pullout strength, however, because of a decreased major-to-minor diameter and increased pitch. Cortical screws differed in fatigue performance despite identical dimensions, presumably highlighting the importance of implant processing and machining. Cannulated cortical screws performed well relative to solid screws, thereby supporting their clinical use. Pure titanium and stainless steel cancellous screws performed similarly in fatigue despite differing material properties, presumably because of geometric design differences. This report highlights some of the differences in the in vitro fatigue performance among several commonly used small fragment screws.     

Bacterial adherence to bioinert and bioactive materials studied in vitro

In vitro, bioinert stainless steel and titanium alloy, and bioactive sintered hydroxyapatite and hydroxyapatite-coated titanium materials were exposed to Staphylococcus epidermidis to study bacterial adhesion. Scanning electron microscopy showed that fibrous strands interconnected the adherent bacteria, and that background matrix enclosed bacterial colonies. This adherent mode of growth may reduce the susceptibility of the bacteria to host clearance mechanisms and antibiotic therapy. Adherence assays revealed that bacterial adherence to sintered hydroxyapatite was higher than to the other 3 materials.     

Removal torques of small screws of steel and titanium with different surfaces

This study was designed to investigate the relationship between metal surfaces and bone holding strength and the safety margin against breakage available in small screws at implant removal. Small cortical bone screws of 1.5 and 2 mm outer diameter (mini-screws) made of stainless steel or commercially pure titanium have been mechanically and chemically treated to give different surface conditions. They were implanted in randomized groups of four or five speciments into the proximal halves of rabbit tibiae. Tightening was performed with a standardized torque of 10 or 18 Ncm by means of an instrumented screwdriver. The animals were sacrificed after 12 weeks and screw removal torques were measured. Stainless steel screws used as reference screws were found to have loosened their seat by 27% compared with the original tightening torque. Titanium implants, in contrast, revealed improved bone contact with higher removal torques varying from 130% to 160%. No correspondence could be found between these values and the surface roughness of glass-ball-blasted versus polished screws.     

Engaging consumers living in remote areas of Western Australia in the self-management of back pain: a prospective cohort study

Background

In the present study, 4 different metallic implant materials, either partly coated or polished, were tested for their osseointegration and biocompatibility in a pelvic implantation model in sheep.

Methods

Materials to be evaluated were: Cobalt-Chrome (CC), Cobalt-Chrome/Titanium coating (CCTC), Cobalt-Chrome/Zirconium/Titanium coating (CCZTC), Pure Titanium Standard (PTST), Steel, TAN Standard (TANST) and TAN new finish (TANNEW). Surgery was performed on 7 sheep, with 18 implants per sheep, for a total of 63 implants. After 8 weeks, the specimens were harvested and evaluated macroscopically, radiologically, biomechanically (removal torque), histomorphometrically and histologically.

Results

Cobalt-Chrome screws showed significantly (p = 0.031) lower removal torque values than pure titanium screws and also a tendency towards lower values compared to the other materials, except for steel. Steel screws showed no significant differences, in comparison to cobalt-chrome and TANST, however also a trend towards lower torque values than the remaining materials. The results of the fluorescence sections agreed with those of the biomechanical test. Histomorphometrically, there were no significant differences of bone area between the groups. The BIC (bone-to-implant-contact), used for the assessment of the osseointegration, was significantly lower for cobalt-chrome, compared to steel (p = 0.001). Steel again showed a lower ratio (p = 0.0001) compared to the other materials.

Conclusion

This study demonstrated that cobalt-chrome and steel show less osseointegration than the other metals and metal-alloys. However, osseointegration of cobalt-chrome was improved by zirconium and/or titanium based coatings (CCTC, TANST, TAN, TANNEW) being similar as pure titanium in their osseointegrative behavior.