假体双延伸肩台拉力螺钉固位设计的生物力学评价

目的：对双延伸肩台拉力螺钉固位方式进行生物力学评价，探索合理的下颌骨假体固位方式。方法：选择1例华东地区正常成年男性，建立基于CT图像数据文件的下颌骨三维有限元模型，计算机模拟半侧下颌骨缺损．设计双延伸肩台拉力螺钉固位方式的下颌骨假体修复，分析4种工况条件下固位方式的应力分布特征。采用SAS6、12软件包进行t检验及方差分析。结果：4种工况条件下，双延伸肩台拉力螺钉固位结构应力完全呈等强度分布（P=0.2997）．平均受力值远低于钛材的许应力值；固位结构周围骨组织所承受的应力分布合理（P=0．9377），与正常松质骨最佳应力值间无统计学差异（P=0.7083）。结论：下颌骨假体双延伸肩台拉力螺钉固位方式应力分布合理，且有利于周围骨组织的改建。     

Comminuted olecranon fracture fixation with pre-contoured plate: Comparison of composite and cadaver bones

AIM: To determine whether use of a precontoured olecranon plate provides adequate fixation to withstand supraphysiologic force in a comminuted olecranon fracture model.METHODS: Five samples of fourth generation composite bones and five samples of fresh frozen human cadaveric left ulnae were utilized for this study. The cadaveric specimens underwent dual-energy X-ray absorptiometry (DEXA) scanning to quantify the bone quality. The composite and cadaveric bones were prepared by creating a comminuted olecranon fracture and fixed with a pre-contoured olecranon plate with locking screws. Construct stiffness and failure load were measured by subjecting specimens to cantilever bending moments until failure. Fracture site motion was measured with differential variable resistance transducer spanning the fracture. Statistical analysis was performed with two-tailed Mann-Whitney-U test with Monte Carlo Exact test.RESULTS: There was a significant difference in fixation stiffness and strength between the composite bones and human cadaver bones. Failure modes differed in cadaveric and composite specimens. The load to failure for the composite bones (n = 5) and human cadaver bones (n = 5) specimens were 10.67 nm (range 9.40-11.91 nm) and 13.05 nm (range 12.59-15.38 nm) respectively. This difference was statistically significant (P ˂ 0.007, 97% power). Median stiffness for composite bones and human cadaver bones specimens were 5.69 nm/mm (range 4.69-6.80 nm/mm) and 7.55 nm/mm (range 6.31-7.72 nm/mm). There was a significant difference for stiffness (P ˂ 0.033, 79% power) between composite bones and cadaveric bones. No correlation was found between the DEXA results and stiffness. All cadaveric specimens withstood the physiologic load anticipated postoperatively. Catastrophic failure occurred in all composite specimens. All failures resulted from composite bone failure at the distal screw site and not hardware failure. There were no catastrophic fracture failures in the cadaveric specimens. Failure of 4/5 cadaveric specimens was defined when a fracture gap of 2 mm was observed, but 1/5 cadaveric specimens failed due to a failure of the triceps mechanism. All failures occurred at forces greater than that expected in postoperative period prior to healing.CONCLUSION: The pre-contoured olecranon plate provides adequate fixation to withstand physiologic force in a composite bone and cadaveric comminuted olecranon fracture model.     

降钙素基因相关肽神经生长因子与失神经支配兔骨折愈合

背景：骨折不愈合严重影响患者生活质量,神经生长因子用于骨不连的防治是重建外科领域研究的重点和方向。 目的：观察神经生长因子降钙素基因相关肽对失神经支配兔骨折愈合的影响。 方法：构建大白兔失神经支配腓骨骨折模型后,实验组骨折端局部注射降钙素基因相关肽10 μg,每2 d一次;对照组骨折端局部注射等量生理盐水。术后2,4,6周分别测定静脉血中肾上腺素和去甲肾上腺素的水平,并进行生物力学和组织学分析。 结果与结论：术后两组血清肾上腺素和去甲肾上腺素水平均有显著增高,在术后第4周达到最高峰,比术前高出1倍以上,第6周时出现下降,但仍然显著高于术前;术后2,4,6周,实验组肾上腺素和去甲肾上腺素血清水平较对照组显著增高,差异具有显著性意义(P < 0.05~0.01)。在三点弯曲实验中,实验组骨痂的抗弯强度明显高于对照组(P < 0.05~0.001);术后第6周时苏木精-伊红染色可见实验组骨痂中的透明软骨细胞已被成骨细胞替代,对照组骨痂中的软骨细胞仍没有完全成骨细胞化。提示神经生长因子降钙素基因相关肽对失神经支配兔骨折愈合具有明显的促进作用。 关键词：神经生长因子;降钙素基因相关肽;骨折愈合;生物力学;生物化学     

Luque棒生理负荷下的实验应力分析

Luque棒断裂、旋转和错动导致治疗失败,已引起临床专家的重视,目前尚缺乏有关的生物力学实验和分析。本实验应用8具新鲜猪脊柱,分4级载荷(100N,200N,300N,400N)测试Luque棒的应力分布及其影响因素。结果表明:生理负荷下,Luque棒中段承力最大,应力随负荷增加而增大,在400N负荷下,应力接近316L不锈钢材料的疲劳限度。钢丝固定的松紧度影响Luque棒受力的均衡。根据研究结果,作者找出了Luque棒生理轴压下的应力分布及其影响因素。作者同时还指出:新型脊柱内固定结构的研究,应考虑固定结构受力后的应力分布情况,依据力学原理,使固定物应力分布均衡。同时,强调Luque系统的规范化操作是保障脊柱固定可靠和固定物力学稳定的重要环节。     

克氏针串接组合内固定治疗髌骨粉碎骨折的生物力学分析

目的：利用生物力学方法测试克氏针串接组合（CSKW）内固定治疗髌骨粉碎骨折的生物力学原理。方法：新鲜尸体膝关节，制成髌骨粉碎骨折模型，用CSKW法固定、单纯克氏针固定法、Magnuson法、钢丝环状缝扎法复位固定，应用实验力学方法测定，比较内固定后的生物力学性能。结果 CSKW复位内固定完全符合髌骨的生物力学性能，能满足膝关节锻炼时的钢度和强度。结论：CSKW固定治疗髌骨粉碎骨折，具有优越的力学和生物力学性能。     

Infrapatellar fat pad pressure and volume changes of the anterior compartment during knee motion: possible clinical consequences to the anterior knee pain syndrome

This biomechanical study was performed to measure tissue pressure in the infrapatellar fat pad and the volume changes of the anterior knee compartment during knee flexion–extension motion. Knee motion from 120° of flexion to full extension was simulated on ten fresh frozen human knee specimens (six from males, four from females, average age 44 years) using a hydraulic kinematic simulator (30, 40, and 50 Nm extension moment). Infrapatellar tissue pressure was measured using a closed cell sensor. Infrapatellar volume change in the anterior knee compartment was evaluated subsequent to removal of the fat pad using a water-filled bladder. We found a significant increase of the infrapatellar tissue pressure during knee flexion, at flexion angles of <20° and >100°. The average tissue pressure ranged from 343 (±223) mbar at 0° to 60 (±64) mbar at 60° of flexion. The smallest volume in the anterior knee compartment was measured at full extension and 120° of flexion, whereas the maximum volume was observed at 50° of flexion. In conclusion, the data suggest a biomechanical function of the infrapatellar fat pad at flexion angles of <20° and >100°, which suggests a role of the infrapatellar fat pad in stabilizing the patella in the extremes of knee motion.     

Anatomy of the proximal tibiofibular joint

This paper describes the anatomy and function of the proximal tibiofibular joint (PTFJ). The physical dimensions of the joint and the topology of the articular surfaces are described. It is noted that the inclination of the joint is variable, and that joints with a steeper slope away from the transverse plane are less mobile. The ligamentous and tendinous attachments are described. Finally, the histological features of the articular surfaces are presented. The clinical importance of the anatomical features is discussed.     

人体股前区皮肤生物力学特性的初步研究

采用ＨＬＣ－１型生物活组织力学试验机对正常成年人股前区皮肤进行生物力学测定。结果表明，股前区皮肤垂直于皮纹方向的应力与应变之间呈指数函数关系，当应变在１．２以内时，应变增加而应力增加不明显，而当应变大于１．２时，应力急剧增加。提示不论伤口缝合及植皮手术时皮肤应变范围应在１．２内为宜。     

Relation of intramuscular pressure to the force output and myoelectric signal of skeletal muscle

The force output of the biceps brachii muscle during static isometric contractions was studied in 26 arms of 23 subjects in relation to the simultaneously recorded level of the electromyogram (EMG) and the intra-muscular pressure (IMP). The EMG was picked up with wire electrodes and the IMP recorded through wick catheters or by infusion technique. The load at the wrist was monitored using a force transducer. A near linear relationship with correlation coefficients exceeding 0.96 was shown between the load on the wrist on the one hand and IMP and EMG on the other. The regression coefficients of the relation between the load and IMP or EMG varied considerably between individuals and between different measuring points in the same individual. In cases where the correlation between the wrist load on one hand and the IMP and EMG on the other was poor because of varying synergistic interaction between the flexor muscles, the EMG and IMP were always well correlated. This means that they change in the same way when the mechanical output of the muscle varies. This was also the case in three experiments where the IMP and EMG from all three elbow flexors were recorded while the subjects changed from a supinated to a pronated position supporting a constant load on the wrist. Considering these observations we present indirect evidence that IMP and the level of the EMG signal both are good estimators of isolated muscular force under isometric static conditions and over limited time.     

Physiopathological variations in the mechanical properties of skin

Summary An evaluation of the rheological properties of skin is provided by measuring in situ the ability of skin to withstand vertical forces of extension. In physiological conditions the biomechanical parameters are reproducible and related to age, sex, skin thickness and the microarchitecture of the connective tissue studied by scanning electron microscopy. These observations shed some light on the structure-function relationship of the fibrous framework of the connective tissue. Variation in the biomechanical parameters can be used to substantiate clinical diagnosis and to monitor the evolution and the therapy of various diseases of the connective tissue.Presented in part at the 3rd Meeting of the European Society for Dermatological Research, Amsterdam (1973) and at the Meeting on Measurement of Physical Properties of Skin, Miami (1976)