双平面导航机器人系统在不同骨科适应症中的应用研究

从双平面定位算法和模块化导航机器人两方面阐述了双平面导航机器人系统．该系统通过对映射算法和导航机器人结构的调整,来适应不同的骨科适应症．本文从工作空间、投影模型、定位算法、临床实验及评价指标等方面介绍了双平面导航机器人系统在胫骨髓内钉、股骨髓内钉、股骨颈空心钉和骨盆骶髂关节螺钉这四种不同的骨科手术适应症中的应用研究情况．     

Decreased Fibroblast and Increased Osteoblast Functions on Ionic Plasma Deposited Nanostructured Ti Coatings

Bioactive coatings are in high demand to control cellular functions for numerous medical devices. The objective of this in vitro study was to characterize for the first time fibroblast (fibrous scar tissue forming cells) adhesion and proliferation on an important polymeric biomaterial (silicone) coated with titanium using a novel ionic plasma deposition (IPD) process. Fibroblasts are one of the first anchorage-dependent cells to arrive at an implant surface during the wound healing process. Persistent excessive functions of fibroblasts have been linked to detrimental fibrous tissue formation which may cause implant failure. The IPD process creates a surface-engineered nanostructure (with features usually below 100 nm) by first using a vacuum to remove all contaminants, then guiding charged metallic ions or plasma to the surface of a medical device at ambient temperature. Results demonstrated that compared to currently used titanium and uncoated silicone, silicone coated with titanium using IPD significantly decreased fibroblast adhesion and proliferation. Results also showed competitively increased osteoblast (bone-forming cells) over fibroblast adhesion on silicone coated with titanium; in contrast, osteoblast adhesion was not competitively increased over fibroblast adhesion on uncoated silicone or titanium controls. In this manner, this study strongly suggests that IPD should be further studied for biomaterial applications in which fibrous tissue encapsulation is undesirable (such as for orthopedic implants, cardiovascular components, etc.).     

Synthesis and microstructural characterization of nano-size calcium phosphates with different stoichiometry

Calcium phosphates with Ca/P molar ratios of 0.5, 0.75, 1.33, 1.5, 1.55, 1.67, 2.0, and 2.5 were synthesized by a wet chemistry precipitation method and sintered at 500 °C, 700 °C, 900 °C, 1100 °C and 1300 °C for 2 h. Presence of phases and microstructures of calcium phosphates were determined by X-ray diffraction and scanning electron microscopy. In all different Ca/P ratios, the precipitated phase was always hydroxyapatite with very small size and/or partial disorderness regardless of the Ca/P ratios in the starting precipitating medium. For samples with 0.5 and 0.75 Ca/P ratios in starting solution, tricalcium phosphate and calcium pyrophosphate phases were observed. In contrast, for samples with 1.0 and 1.33 Ca/P ratios, the only stable phase was tricalcium phosphate. For the samples with Ca/P ratio of 1.5, the tricalcium phosphate phase was dominant. However, small amounts of hydroxyapatite started to appear. For samples with Ca/P ratio of 1.67, the hydroxyapatite phase was dominant. Lastly, for samples with the Ca/P ratios of 2.0 and 2.5, the CaO phase started to appear in addition to the hydroxyapatite phase which was the dominant phase. Moreover, the average grain size, porosity (%) and the average pore size decreased with increasing the Ca/P ratios.     

Effect of Water and Serum Absorption on Wear of Unirradiated and Crosslinked UHMWPE Orthopedic Bearing Materials

Abstract

In addition to confounding mass-based wear measurements in serum-lubricated hip simulator experiments, fluid absorption by the acetabular cups may simultaneously modify the wear resistance of the ultra-high molecular weight polyethylene (UHMWPE) from which they are composed. To decouple the fluid absorption and wear processes enabling clearer investigation of this effect, absorption was first imposed during an initial stage where UHMWPE was exposed to pressurized (10 MPa) fluid. This was followed by a second stage, where resultant wear behavior was assessed by a multidirectional pin-on-flat technique that, though still providing a serum-lubricating environment, does not promote the simultaneous fluid absorption occurring in hip simulator testing. Both unirradiated and highly crosslinked UHMWPE were investigated, each with both bovine calf serum and water soaking exposures of duration to 129 days. The pressurized soaking of a highly crosslinked UHMWPE decreased its wear resistance, causing an increase in wear rate by approximately 50% during subsequent serum-lubricated multidirectional pin-on-flat sliding tests as compared to non-soaked material. The magnitude of this effect did not appear to depend on whether the soaking fluid was water or serum, nor did it appear to depend on soak time provided it was at least of a 14-day duration, during which more rapid transient fluid absorption occurs. Such soaking did not produce as pronounced an effect on unirradiated UHMWPE, as its lack of wear resistance likely causes the absorption-affected surface region to be removed within the earliest stages of sliding contact.     

New material for orthopedic implants: Electrochemical study of nickel free P558 stainless steel in minimum essential medium

Nickel, a component of stainless steels (SS) applied in orthopedic implants may cause allergic processes in human tissues. P558 nickel free SS was studied to verify its viability as a substitute for stainless steel containing nickel. Its performance is compared to ISO 5832-9 and F138 most used nowadays grades in implants fabrications, in minimum essential medium, MEM, at 37 °C. Potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and “in vitro” cytotoxicity were used as techniques. From the electrochemical point of view P558 SS is comparable to ISO 5832-9 SS in MEM. It remains passivated until the transpassivation potential, above which generalized corrosion occurs. F138 presents pitting corrosion at 370 mV/SCE. The cytotoxicity results showed that P558, ISO 5832-9 and F138 do not present cytotoxic character. Therefore, these results suggest that P558 SS can be applied in orthopedic implants.     

Relationships between the fretting wear behavior and mechanical properties of thin carbon films

Mechanical load can drastically affect the properties of orthopedic implant materials. Damage of these materials usually occurs in contact surfaces, caused by abrasion, adhesion, fretting, delamination, pitting and fatigue depending on friction, lubrication, contact area, surface finish and level of loads (stresses).Carbon-based films are biocompatible with good bearing capacity, wear resistance, corrosion resistance and have a low coefficient of friction. However, great intrinsic stress prevents their wider application, mainly as implant coatings. To reduce this undesirable effect special deposition procedures are under development and/or the films are doped with suitable elements. It must be emphasized that DLC is not a material but a group of materials with a variety of properties. The relationships between the fretting wear behavior and mechanical properties of films based on carbon deposited by DC using the pulsed arc discharge PVD nitrogen doped (a-C) and the filtered pulsed arc discharge deposition system (ta-C) were tested.The composition of carbon films (sp³, sp²) was determined by Raman spectroscopy. Mechanical properties of elastic modulus and hardness were determined by a NanoTest apparatus with diamond Berkovich tip using the Oliver-Pharr procedure and adhesion was measured by nanoscratch tests. Tribological behavior was analyzed by fretting tests with a corundum ball under dry sliding lubricated conditions.The good performance of the hard carbon coatings is often discussed. Results from this study of fretting and the associated lubrication (bovine serum) show that ta-C coatings, despite their high hardness, have very low friction coefficients and low volume losses.     

Preparation and characterization of as-extruded Mg–Sn alloys for orthopedic applications

In this study, as-extruded Mg–Sn alloys with various Sn content were prepared and characterized for orthopedic applications. The results of microstructure observations and X-ray diffraction analysis showed that as-extruded Mg–Sn alloys were composed of α-Mg and Mg₂Sn phases, and the content of Mg₂Sn phase increased with increasing Sn content. The microstructure of as-extruded Mg–Sn alloy with 1 wt.% Sn was equiaxed grain, while the one with a higher Sn content was inhomogeneous microstructure and the grain size of the long elongated grains decreased with increasing Sn content. Tensile test revealed that the yield strength and ultimate tensile strength of as-extruded Mg–Sn alloys increased while the elongation decreased with increasing Sn content. Immersion and electrochemical tests indicated that the microstructure of as-extruded Mg–Sn alloys affected their corrosion properties, and the increase of Mg₂Sn phase resulted from the increase of the Sn content led to a higher corrosion rate. The cytotoxicity test showed that as-extruded Mg–1Sn and Mg–3Sn alloys met the requirement of cell toxicity for orthopedic applications. Our analyses showed that as-extruded Mg–1Sn and Mg–3Sn alloys were promising to be used as biodegradable orthopedic implants.     

基于骨科护理应用发展的新型材料制备研究

骨科护理应用发展中无卤涂料起着非常关键的作用。采用FRC-6替换实现小分子二醇扩链剂,实现新型的误无卤阻燃改性涂料的制备。实验结果表明:当P含量保持在一定范围内,预聚体中质量分数会很大程度的影响胶膜的耐水性;Pu乳胶粒子的粒径的减小影响了粒径分布;P含量影响了PU的热释放速率,即可以实现降低热释放量,增大LOI,提高阻燃性能。这一研究对于骨科护理应用发展中新材料应用具有一定的意义。     

第一性原理计算NbTaTiZr系多组元合金骨科植入物材料的力学性能

基于第一性原理密度泛函理论,结合广义梯度近似(GGA),对采用虚拟晶格近似(VCA)法建立的NbTaTiZr系体心立方结构模型,进行结构性质、弹性性质、各向异性以及硬度和耐磨性的计算,并结合骨科植入物材料的力学性能指标对计算结果进行了讨论。结果表明,Nb、Ta元素可以提高材料的延展性和金属键特性。Ti元素含量的增加有利于多组元合金杨氏模量和剪切模量的降低,显著提高合金的塑性,但考虑到泊松比与天然骨的匹配,应该严格控制Ti的含量。Ta、Nb、Zr、Ti对合金各向异性的影响依次增强。NbTa_1.4TiZr合金的泊松比与超高分子量聚乙烯(UHMWPE)人工髋关节相当,最接近人体皮质骨的显微硬度。