实验性髋臼横形骨折对髋关节接触特征的影响

目的了解不同平面髋臼横形骨折及内固定后髋关节接触压力、面积的变化,确定髋臼横形骨折手术指征,探讨髋臼横形骨折最可靠的内固定方式.方法采用24个髋关节标本制成30°、40°、50°、60°内侧顶弧角髋臼横形骨折模型,利用压敏片技术,对不同内侧顶弧角截骨前后及不同内固定后髋关节标本分别进行加载800 N,研究髋关节接触特征.结果30°内侧弧顶弧角组髋关节接触面积最小,接触压力最大.前柱螺钉加后柱钢板(S+P)、前柱钢板加后柱螺钉(P+S)较前柱单钢板(P/none)及后柱双钢板(none/P×2)内固定在降低接触压力、提高接触面积方面优越.结论30°内侧顶弧角髋臼横形截骨组需手术治疗,髋臼横形骨折内固定以S+P及P+S较为理想.     

微创动力髋螺钉的研制

研制一种固定坚强可靠,又能微创操作的内固定器械,用于治疗股骨粗隆间骨折。根据动力髋螺钉的结构进行改进,将1枚拉力螺钉改为2枚,增加固定强度;套筒钢板由一体改为可拆卸,便于微创操作;设计体外瞄准器,便于股骨干螺钉的固定,并将动力髋螺钉作为对照,比较两者的生物力学性能。生物力学测试结果表明,微创动力髋螺钉在载荷-应变变化,载荷-位移变化,股骨的强度和刚度,极限力学性能等方面,均优于动力髋螺钉。临床初步应用,取得满意效果,未出现并发症。     

兔盆底组织力学特性的实验研究

目的研究分娩与未分娩兔盆底组织的生物力学特性。方法以14只新西兰雌性大白兔盆底组织为拉伸试样，分娩与未分娩分组对照，用WDW4100微机控制电子万能实验机进行拉伸实验，测定其应力应变关系，蠕变和应力松弛特性。结果得到了闭孔内肌和孑子肌肌腱的极限强度、最大刚度、应力应变关系和粘弹性特征。结论分娩与未分娩兔盆底组织生物力学特性存在明显的差异，这对临床上研究人类盆底组织有一定的参考价值，有助于妇产泌尿科学的发展。     

新型陶瓷改善椎弓根螺钉稳定性的研究

为探讨添加新型陶瓷对改善椎弓根螺钉稳定性的影响，将椎弓根螺钉分别植入28个L3－L5椎体两侧椎弓根，随机在一侧加α-BSM^TM。16个椎体做螺钉轴向拔出试验，测试最大轴向拔出力（Fmax)和拔出过程中的能量吸收值E－Fmax和E－2mm。另外12个椎体做梯增负荷的螺钉周期抗屈试验。两组相比较发现，加入α-BSM^TM后，Fmax增加了66．8％，E－Fmax和E-2mm分别增加了169．5％和60．6％，差别有统计学意义（Wilcoxon′s检验，P＜0.01)。周期抗屈试验中，增加α-BSM^TM可使螺钉耐受更大的负荷或在同等负荷下仅产生较小的位移。结果表明：在椎弓根螺钉植入时添加α-BSM^TM能显著提高其初始的稳定性。     

Absorptiometry and “osteoporosis”: problems

connecting the dots between diverse clinical and other matters and an updated bone physiology reveals relationships that could modify some ideas about the roles and uses of absorptiometry in osteoporosis work. Herein, absorptiometry means that part of clinical densitometry that depends on X-ray absorption by bone and other tissues, thus excluding ultrasound methods and magnetic resonance imaging. The modifications concern, in part, some limitations of bone mineral density data, the kinds of physiological information that absorptiometry can and cannot provide, the relative importance of bone mass and whole-bone strength, how to define and study bone health and osteoporosis, and two kinds of osteoporotic fractures. As those modifications concern important national health care issues, they deserve answers based on hard evidence. Identifying those modifications might help others to evaluate them.     

Mechanical properties of acellular peripheral nerve

BACKGROUND: Acellular nerve has been used in experimental models as a peripheral nerve substitute. Our objective was to determine the difference in tensile strength between fresh and chemically treated acellularized peripheral nerve. MATERIALS AND METHODS: F344 rat sciatic nerves were either fresh or acellularized and tested either whole (Part A) or transected and repaired (Part B). For all constructs, the mean ultimate stress, mean ultimate strain, Young's modulus, and total mechanical work to fracture were calculated.The average ultimate strains for Groups A-1 and A-2 were 0.480 +/- 0.117 and 0.810 +/- 0.114, respectively. The Young's moduli in Groups A-1 and A-2 were 576 +/- 160 and 580 +/- 150 kPa, respectively. In Groups A-1 and A-2, the normalized work to failure was 0.35 +/- 0.14 and 1.11 +/- 0.38 N. The specimens in Group B-1 withstood an average ultimate stress of 780 +/- 280 kPa. The specimens in Group B-2 withstood an average ultimate stress of 405 +/- 20 kPa. RESULTS: The average ultimate strains for Groups B-1 and B-2 were 0.319 +/- 0.087 and 0.266 +/- 0.019, respectively. The Young's moduli in Groups B-1 and B-2 were 4,030 +/- 1360 and 2,290 +/- 280 kPa, respectively. The normalized work to failure in Groups B-1 and B-2 was calculated as 0.22 +/- 0.04 and 0.11 +/- 0.02 N. CONCLUSIONS: Although adequately robust for reconstructive procedures, the acellular peripheral nerve had decreased tensile strength compared with fresh nerve either when tested whole or when transected and repaired.     

Inferior mechanical properties of spastic muscle bundles due to hypertrophic but compromised extracellular matrix material

The passive mechanical properties of small muscle fiber bundles obtained from surgical patients with spasticity (n = 9) and patients without neuromuscular disorders (n = 21) were measured in order to determine the relative influence of intracellular and extracellular components. For both types of patient, tangent modulus was significantly greater in bundles compared to identical tests performed on isolated single cells (P < 0.05). However, the relative difference between bundles and single cells was much greater in normal tissue than spastic tissue. The tangent modulus of normal bundles (462.5 +/- 99.6 MPa) was 16 times greater than normal single cells (28.2 +/- 3.3 MPa), whereas the tangent modulus of spastic bundles (111.2 +/- 35.5 MPa) was only twice that of spastic muscle cells (55.0 +/- 6.6 MPa). This relatively small influence of the extracellular matrix (ECM) in spastic muscle was even more surprising because spastic muscle cells occupied a significantly smaller fraction of the total specimen area (38.5 +/- 13.6%) compared to normal muscle (95.0 +/- 8.8%). Based on these data, normal muscle ECM is calculated to have a modulus of 8.7 GPa, and the ECM from spastic muscle of only 0.20 GPa. These data indicate that spastic muscle, although composed of cells that are stiffer compared to normal muscle, contains an ECM of inferior mechanical strength. The present findings illustrate some of the profound changes that occur in skeletal muscle secondary to spasticity. The surgical implications of these results are discussed.     

A biomechanical analysis of two reconstructive approaches to the posterolateral corner of the knee

The objective of this study was to evaluate the effects of the biceps femoris tenodesis and popliteofibular ligament reconstruction on knee biomechanics. Ten human cadaveric knees were tested in the intact, posterolateral corner (PLC)-deficient, and PLC-reconstructed conditions using a robotic/universal force moment sensor testing system. The knees were subjected to: (1) a 134 N posterior tibial load, and (2) a 10 Nm external tibial torque applied to the tibia at full extension, 30° and 90° of flexion. External tibial rotation of the intact knee ranged from 18.3±4.6° at full extension to 27.9±4.6° at 30° under the 10 Nm external tibial torque. These values increased after sectioning the PLC by 2.8°–7.5° at 30° and 90° respectively. After the popliteofibular ligament reconstruction, external tibial rotation values were not significantly different from those for the intact knee at any angle tested, while values following the biceps tenodesis were as much as 5.7° greater than the intact knee. Under the 134 N posterior tibial load, there were minimal decreases in posterior tibial translation of up to 0.9 mm with the biceps tenodesis and up to 1.6 mm with the popliteofibular ligament reconstruction compared to the intact knee. The in situ forces in the biceps tenodesis were not significantly different than the intact PLC at full extension or 30°, while the in situ forces in the popliteofibular graft were not significantly different at any flexion angle. Our data suggests that by restoring external tibial rotation the popliteofibular ligament reconstruction more closely reproduces the primary function of the PLC as compared to the biceps tenodesis.     

五加皮对去卵巢大鼠骨质疏松防治作用的生物力学研究

目的：研究以五加皮防治骨质疏松的药效学基础，为临床应用提供实验依据。方法：SPF级雌性SD大鼠，4、5月龄，体重200-220g，采用手术去除双侧卵巢方法。建立骨质疏松实验动物模型，随机分组，给药12w。测定骨生物力学相关指标。结果：模型组下肢离体股骨骨生物力学指标均显著下降，表明实验动物模型成立。与钙尔奇D作用相似，五加皮具有明显改善骨生物力学性能。结论：五加皮对防治骨质疏松症具有良好的效果。