Finite element analysis of femoral components paper III – hip joints

Finite element analysis of the hip implant is conducted in this paper for representative femoral cross-section geometries and development of stress in the presence of bone cement is elucidated. Differences in cement stresses generated by varying implant cross-sections were compared with conventional features derived from representative implants. The analysis was performed under idealized implant assemblies by constraining the implant movement in the assembly. The cross-sections and implant geometries used are generic and intended to be representative of available geometries. This paper is a part of student research projects, prepared from a series of activities in biomedical implant research currently underway at Ohio Northern and Arkansas Tech Universities.     

钛合金植入物材料的表面改性研究进展

简介了钛合金植入物材料的开发及表面改性技术。     

A study on microstructure and properties of calcium phosphate coatings processed using ion beam assisted deposition on heated substrates

In this study a set of thin Hydroxyapatite (HA) [Ca₁₀(PO₄)₆(OH)₂] coatings was deposited on heated silicon and titanium substrates using Ion Beam Assisted Deposition (IBAD). The effects of substrate temperature and processing parameters on the microstructural properties and composition of the coatings are being studied. Analytical techniques include transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) with an energy dispersive X-ray spectroscopy (EDS), as well as scanning electron microscopy (SEM) with EDX, X-ray diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR). The current results indicate that as substrate temperature increases the Ca/P ratio of the coatings both on titanium and silicon substrates increases. The crystallinity of the coatings and the number of calcium phosphate compounds within the coating including HA also increases. STEM-EDS revealed an atomically diffused intermediate layer at the interface between the coating and substrate. XRD results along with TEM selected area diffraction (SAD) revealed that the coatings are composed of HA, other calcium phosphate, and calcium oxide compounds.     

Thick bone section preparation using a silicon-rubber-based sealant

A method has been developed, using a silicon-rubber-based sealant, which allows 2–3-mm-thick specimens to be maintained in a protected fluid environment for a number of months, without risk of dehydration. Following this, the specimen can be retrieved, stained, embedded and sectioned further. For example, 2-mm-thick sections of fixed unstained bone are easily examined by means of epi-illuminated polarized light and fluorescence microscopies using either conventional or confocal optics. The method could easily be extended to other tissues, for example brain tissue.     

The T Cell Repertoires from Nickel Sensitized Joint Implant Failure Patients

Nickel (Ni²⁺) is one of the most common allergens, affecting around 10–15% of the general population. As the demand for orthopedic implant surgery rises, the number of surgical revisions due to joint implant failure also increases. There is evidence that some patients develop joint failure due to an immune response to a component of the implant, and we have found that Ni²⁺ is an especially important cause. Hence, understanding the mechanisms by which Ni²⁺ allergy induces joint implant failure becomes a critical research question. The structural basis of Ni²⁺ activation of pathogenic T cells is still not clear. The purpose of this study was to characterize Ni²⁺-reactive T cell repertoires derived from the peripheral blood of joint failure patients due to Ni²⁺ sensitization using single-cell sequencing techniques. We stimulated the proliferation of Ni²⁺ -reactive T cells from two implant failure patients in vitro, and sorted them for single-cell VDJ sequencing (10× genomics). We identified 2650 productive V-J spanning pairs. Both TCR α chains and β chains were enriched. TRBV18 usage is the highest in the P7 CD4+ population (18.1%), and TRBV5-1 usage is the highest in the P7 CD8+ population (12.1%). TRBV19 and TRBV20-1 segments are present in a high percentage of both P7 and P9 sequenced T cells. Remarkably, the alpha and beta chain combination of TRAV41-TRBV18 accounts for 13.5% of the CD4+ population of P7 patient. Compared to current Ni specific T cell repertoire studies of contact dermatitis, the Vα and Vβ usages of these joint implant failure patients were different. This could be due to the different availability of self-peptides in these two different tissues. However, TRBV19 (Vβ17) was among frequently used TCR β chains, which are common in previous reports. This implies that some pathogenic T cells could be similar in Ni²⁺ hypersensitivities in skin and joints. The alignment of the TCR CDR3β sequences showed a conserved glutamic acid (Glu) that could potentially interact with Ni²⁺. The study of these Ni²⁺ specific TCRs may shed light on the molecular mechanism of T cell activation by low molecular weight chemical haptens.     

采用听觉外周模型改进电子耳蜗CIS方案

提出了一种改进的CIS电子耳蜗的脉冲刺激方案。利用听觉外周模型产生一种符合听神经发放机制的刺激脉冲序列来刺激电极,代替传统的均匀交替刺激方案,不仅可以通过包络而且可以通过脉冲间隔来传递语音信息,确保了语音的空间编码和时间编码。听觉仿真实验表明,相对于其他两种方案,方案可以有效地传递更多更丰富的语音信息,在汉语声调识别实验中至少提高19.2%识别率,在可懂度的对比实验中具有最高可懂度。     

隆鼻假体的数字化设计方法

为了摆脱传统假体制作工艺依赖经验、成品与患者特征不吻合、很难达到预期效果的缺陷,首先将数字化技术与整形理论相结合,以阈值法和灰度拉伸法分割出理想区域的数据,重建了患者鼻骨和鼻软骨的三维模型,并以内眦点等典型特征标志点为参考,建立了模型的对称性设计基准;然后依据隆鼻美学参数和患者要求,模拟了外鼻的整形效果;最后以"截面相似性"方法,设计出个性化数字假体.临床证明:由该设计方法制作的假体,凹面与患者鼻骨以及软骨紧密贴合,凸面线条流畅,实际手术效果与模拟效果一致.     

增加电极位置信息的电子耳蜗听觉仿真模型

为了改进以正弦信号合成的电子耳蜗听觉仿真模型在仿真电子耳蜗植入患者所感知的语音信息的缺陷,建立了增加电极位置信息的正弦信号合成的听觉仿真模型.通过大样本量的不同汉语语言材料的听觉仿真实验,其中包括按元音、辅音、数字、音调和单字词等5种汉语语言材料,研究了基于连续交叉采样算法的不同实验条件下电极位置对言语识别率的影响,得出了汉语元音和单字词对植入深度更加敏感的结论.为进一步将这一仿真模型应用到电子耳蜗研究上奠定了基础.     

计算机辅助插销试验裂纹评定系统的研制

播销试验是评估金属材料焊接裂纹倾向的试验方法。为了提高该试验方法的可靠性、精度和自动化程度。研制了一个以PCL-818LS数据采集卡为核心的计算机辅助智控系统。通过大量冷裂纹和再热裂纹插销试验表明，整个系统的可靠性和精度能满足试验要求。