镉染毒对大鼠骨生物力学性能的影响

目的: 探讨镉对大鼠股骨和腰椎生物力学性能的影响。方法: 24只8周龄雄性SD大鼠随机分成4组，分别背部皮下注射生理盐水0.5ml（对照组）和0.1mg/kg bw(低剂量组)，0.5mg/kg bw（中剂量组），1.5mg/kg bw（高剂量组）CdCl2，每周称体重，并根据体重调整注射量。染毒后第12周，收集全血、腰椎及股骨，分别用于血镉测定、骨镉测定、骨密度测定及生物力学测定。结果: 染毒组大鼠体内血镉及骨镉水平明显高于对照组，差异有统计学意义（P < 0.05）；中、高剂量染毒组大鼠骨密度较对照组显著下降（P < 0.05）；染毒组大鼠股骨和腰椎生物力学性能较对照组有不同程度的的降低，其中高剂量染毒组大鼠股骨生物力学性能的下降和对照组相比有显著差异（P < 0.01）；中剂量和高剂量染毒组大鼠腰椎生物力学性能和对照组相比差异有统计学意义（P < 0.01）。结论: 镉能影响大鼠股骨和腰椎的生物力学性能，并且腰椎生物力学性能的改变要早于股骨。     

基于CT和MRI膝关节有限元模型建立与不同载荷下生物力学特性分析

基于CT和MRI图像数据建立膝关节有限元模型,采用六面体网格对不同载荷系统下人体膝关节生物力学特性进行研究,并进行有效性验证。建立膝关节有限元模型包括:股骨、胫骨、髌骨、腓骨、股骨软骨、胫骨软骨、腓骨软骨、半月板、前后交叉韧带、内外侧副韧带、髌韧带和股四头肌腱等。对膝关节施加1 kN轴向压缩载荷、134 N后向抽屉力和5、10、15 N[?m内翻力矩和外翻力矩,分析膝关节内软骨和半月板的接触应力和接触面积,股骨内外翻倾角以及位移变化情况。在1 kN压缩载荷和134 N抽屉力作用下,股骨软骨、内外侧半月板和内外侧胫骨软骨的接触应力峰值分别为4.47、3.25、2.83、2.70、2.53 MPa,Von Mises应力峰值分别为2.22、2.44、2.25、2.07、1.64 MPa。股骨相对胫骨前向位移为4.19 mm。施加5、10、15 N[?m内翻和外翻力矩时,股骨内翻和外翻倾角分别为3.49°、4.48°、4.91°和3.22°、3.62°、4.01°。随着力矩的线性增大,膝关节各组成部分的应力呈非线性变化趋势。膝关节软骨、半月板和韧带的研究结果符合其生物力学特性,与前人数值分析和实验研究结果相一致,可为临床膝关节生理病理分析和治疗提供一定的理论依据。     

电针治疗膝骨性关节炎患者上下楼梯的三维有限元分析

针对电针治疗膝骨性关节炎患者上下楼梯运动生物力学特性改变进行有限元仿真研究,对比分析膝关节生物力学行为改变与电针治疗疗效的相关性。基于CT和MRI图像数据,结合Mimics和Geomagic医学图像处理软件,建立人体膝关节下楼梯屈曲15°和上楼梯屈曲50°时的三维有限元模型,模型包括股骨、胫骨、腓骨、内外侧半月板、股骨软骨、内外侧胫骨软骨结构等。通过临床力学实验,测取电针治疗前后膝关节所受支反力、力矩,并施加于所建立的有限元模型,对比分析治疗前后半月板及关节软骨的应力分布情况。膝骨性关节炎在电针治疗后,内外侧半月板、股骨软骨、内外侧胫骨软骨的应力均得到不同程度的恢复,与治疗前相比,下楼梯屈曲15°时最大应力值分别减小0.543、0.236、0.194、0.239和0.327 MPa,上楼梯屈曲50°时分别减少0.253、0.31、0.227、0.112和0.122 MPa,软骨的应力峰值趋向于正常值,应力分布范围也更接近于正常膝关节,且关节内侧软骨及半月板比外侧受到的负荷大,软骨应力比更接近于正常值,这与临床上内侧型膝骨性关节炎患者多于外侧型患者的现象相符合,从而证明电针治疗可影响膝关节中力的传递,使病变膝关节的应力吸收能力得到改善和提高。电针治疗膝骨性关节炎能有效改善关节软骨的压应力,使关节内力平衡得到恢复,延缓关节软骨退变,促进关节软骨的修复;电针治疗下膝关节生物力学特性的研究,可为膝关节临床治疗和评价提供理论依据。     

摆幅可调型足部康复机器人的生物力学特性分析

目的基于人机工程学和生物力学仿真技术,对人体肌肉进行生物学评价,研究摆幅可调型足部康复机器人的康复策略。方法在Any Body中建立人体和摆幅可调型足部康复机器人的人机耦合模型,并对耦合模型进行运动学仿真,将仿真结果与理论计算结果相比,验证耦合模型的可靠性;再利用Any Body中的参数研究机制对验证后的耦合模型进行生物力学仿真,以足部康复机器人的运动速度和摆幅为变量,分析在不同变量组合下的肌肉活动度和肌肉力。结果在康复运动中足部相关肌肉的拉伸性能得到有效训练,不同的运动速度和摆幅对肌肉的影响不同,并得出运动速度和摆幅调节的安全范围。结论实现了不同运动速度和摆幅下肌肉活动度和肌肉力的组合分析,研究结果对足部康复机器人的临床应用和被动康复模式下康复策略的制订具有一定指导意义。     

Human umbilical cord blood stem cells and brain-derived neurotrophic factor for optic nerve injury:a biomechanical evaluation

Treatment for optic nerve injury by brain-derived neurotrophic factor or the transplantation of human umbilical cord blood stem cells has gained progress, but analysis by biomechanical indicators is rare. Rabbit models of optic nerve injury were established by a clamp. At 7 days after injury, the vitreous body received a one-time injection of 50 μg brain-derived neurotrophic factor or 1 × 106 human umbilical cord blood stem cells. After 30 days, the maximum load, maximum stress, maximum strain, elastic limit load, elastic limit stress, and elastic limit strain had clearly improved in rabbit models of optical nerve injury after treatment with brain-derived neurotrophic factor or human umbilical cord blood stem cells. The damage to the ultrastructure of the optic nerve had also been reduced. These findings suggest that human umbilical cord blood stem cells and brain-derived neurotrophic factor effectively repair the injured optical nerve, improve biomechanical properties, and contribute to the recovery after injury.     

Analysis of the effects of irradiation in osseointegrated dental implants

Objective: The purpose of the present study was to evaluate the influence of radiation in osseointegrated dental implants installed in tibiae of rats. Material and methods: Screw‐shaped implants (2.5 mm diameter by 3.5 mm length) were custom made from commercially pure titanium bars. Titanium implants were blasted and sterilized before implantation. Animals were divided into two groups of 12 animals each and the rats were not paired after the groups' formation. The experimental group (group 1) received external irradiation 4 weeks after surgery while in the control group (group 2) animals were kept free of radiation. The shear strength required to detach the implant from bone was measured by push‐out testing and osseointegration was histologically evaluated. Results: Results showed that the compressive strength of irradiated implants (33.49 MPa) was significantly lower than the compressive strength of non‐irradiated implants (48.05 MPa). Conclusions: We concluded that the mechanical strength bonding between implants and host tissues decreased after irradiation. To cite this article:
Oliveira JAG, Escada ALA, Alves Rezende MCR, Mathor MB, Alves Claro APR. Analysis of the effects of irradiation in osseointegrated dental implants.
Clin. Oral Impl. Res. 23 , 2012 511–514.
doi: 10.1111/j.1600‐0501.2010.02149.x     

圆锥角膜快速跨上皮交联手术前后Corvis ST参数的重复性及差异性

目的:评估圆锥角膜快速跨上皮交联手术前以及术后1mo Corvis ST参数的重复性及差异性。方法:研究纳入了30例30眼圆锥角膜患者进行分析。圆锥角膜患者术前和术后1mo分别进行三次Corvis ST重复测量。采用组内相关系数(ICC)、克伦巴赫alpha系数(Cronbach'α)、可重复性系数(RC)和变异系数(CV)评估Corvis ST参数的可重复性。采用配对t检验或Wilcoxon秩和检验评估术前与术后Corvis ST参数的差异。结果:术前39个Corvis ST参数中,26个(66.67%)参数重复性较好,6个(15.38%)参数重复性中等,7个(17.95%)参数的重复性较差。交联术后1mo,34个(87.18%)参数的重复性较好,3个(7.69%)参数重复性中等,2个(5.13%)参数的重复性较差。与术前相比,交联术后1mo圆锥角膜患者的眼压、生物力学校正眼压、第一次压平时间、曲率半径、第一次压平时的形变幅度、最大压陷偏离长度、角膜硬度参数值增加;而陡峭曲率、平坦曲率、平均曲率、第二次压平时间、2 mm最大形变幅度比值和综合半径值降低(均P<0.05)。结论:交联手术前和术后1mo Corvis ST参数均具有较好的可重复性,术后1mo圆锥角膜患者的角膜硬度较术前增加。     

Postimplant Behavior of Lightweight Polypropylene Meshes in an Experimental Model of Abdominal Hernia

Background. Over the years, reticular prostheses have undergone changes in their structure and composition to give rise to today's partially absorbable lightweight meshes. This study was designed to assess the biological and biomechanical behavior of these prostheses to establish whether they offer any advantages over nonabsorbable lightweight polypropylene prostheses. Materials and Methods. 7 × 5 cm defects were created in the anterior abdominal wall of New Zealand White rabbits and repaired by securing different prostheses to the edges of the defect with a running 4/0 polypropylene suture. The lightweight biomaterials compared were two nonabsorbable meshes: Parietene® and Optilene elastic®, and two partially absorbable prostheses: Vypro II® and Ultrapro®. At 14 and 90 days postimplant, tissue/prosthesis specimens were subjected to histological, immunohistochemical, shrinkage, and biomechanical analyses. Results. Adhesion formation on the peritoneum-facing surface of the meshes was significantly less extensive in the meshes with absorbable components at 90 days postimplant. The newly formed tissue around the prosthetic filaments was comprised of collagen fibers, fibroblasts, blood vessels, and macrophages. The partially absorbable meshes showed higher macrophage proportions (due to remnants of absorbable material and their structure) than the nonabsorbable meshes at 90 days, although differences were not significant. At 90 days postimplant, similar tensile strengths were recorded for all the implants. Conclusions. All the prosthetic materials induced good host tissue ingrowth, with no significant differences in tensile strength observed. Our findings suggest that partially absorbable lightweight prostheses could offer advantages over nonabsorbable lightweight meshes since less foreign material persists in the recipient, improving abdominal wall compliance.     

Model for assessment of mobility of toes and healing of tendons in rabbits

Abstract

Repair of a transected flexor tendon will, despite careful technique and early rehabilitation, usually result in a restricted range of movement. This is mainly because adhesions form between the tendon and the surrounding structures. Our aim was to establish an experimental model in rabbits for future studies on new techniques to reduce the formation of adhesions after zone II repair of flexor tendons. In rabbits' hind paws the metatarsal bones II, IV, and V were removed and the flexor tendon was freed to the metatarsophalangeal (MTP) joint. The digits were secured in a specifically-designed biomechanical testing device comprising a servo-hydraulic actuator that was designed to apply controlled force or displacement. The tests were videotaped with a digital force-monitor behind the tested digit. Paper printouts from the recordings were obtained for 0, 0.5, 1, 2, 3, 4, and 5 Newton (N) and metatarsophalangeal, proximal interphalangeal, and distal interphalangeal, angles and distances between metatarsophalangeal joints and claws were measured. The tensile strength of the tendon was evaluated by a load-to-failure test. The continuous data obtained from the experiments were used to calculate functional stiffness at the selected forces. The model allows for unique continuous recordings of mobility of toes, thereby indirectly quantifying the presence of adhesions and the assessment of tensile strength. The data are reproducible, and there is little variation between the digits tested. The model is primarily intended to compare data among treated and non-treated digits of methods to limit the formation of adhesions after tendons have been repaired.