猪膝关节与人膝关节的对比及其在生物力学测试中的应用

人膝关节结构复杂,韧带较多,其中交叉韧带对维持膝关节的稳定性至为重要.后交叉韧带(posterior cruciate ligament,PCL)对于维持膝关节的后向稳定性和旋转稳定性具有至关重要的作用.PCL损伤后的主观不适症状要明显少于前交叉韧带损伤,所以过去对PCL的关注及研究要少于前交叉韧带.近年来高能量损伤致使PCL的损伤越来越多,学者们对PCL的关注度也在增加,进行了大量与PCL相关的实验,同时我们发现很多学者用动物的膝关节来代替人尸体进行体外生物力学实验,其中猪膝关节应用的最为广泛,基于这种情况,本文就猪膝关节的解剖结构与人的进行了比较,对其在体外生物力学实验中的应用进行了综述.     

Comparison of nonlinear mechanical properties of bovine articular cartilage and meniscus

Nonlinear, linear and failure properties of articular cartilage and meniscus in opposing contact surfaces are poorly known in tension. Relationships between the tensile properties of articular cartilage and meniscus in contact with each other within knee joints are also not known. In the present study, rectangular samples were prepared from the superficial lateral femoral condyle cartilage and lateral meniscus of bovine knee joints. Tensile tests were carried out with a loading rate of 5 mm/min until the tissue rupture. Nonlinear properties of the toe region, linear properties in larger strains, and failure properties of both tissues were analysed. The strain-dependent tensile modulus of the toe region, Young's modulus of the linear region, ultimate tensile stress and toughness were on average 98.2, 8.3, 4.0 and 1.9 times greater (p<0.05) for meniscus than for articular cartilage. In contrast, the toe region strain, yield strain and failure strain were on average 9.4, 3.1 and 2.3 times greater (p<0.05) for cartilage than for meniscus. There was a significant negative correlation between the strain-dependent tensile moduli of meniscus and articular cartilage samples within the same joints (r=−0.690, p=0.014). In conclusion, the meniscus possesses higher nonlinear and linear elastic stiffness and energy absorption capability before rupture than contacting articular cartilage, while cartilage has longer nonlinear region and can withstand greater strains before failure. These findings point out different load carrying demands that both articular cartilage and meniscus have to fulfil during normal physiological loading activities of knee joints.     

关节镜下多种移植物联合重建膝关节前、后交叉韧带

目的:评估关节镜下膝关节前交叉韧带(ACL)与后交叉韧带(PCL)同时重建的技术和临床效果。方法:自2003年6月～2009年10月,27例病人(28膝)经MRI检查及关节镜检查证实ACL和PCL均断裂,其中9膝伴内侧副韧带损伤(MCL),8膝伴后外侧角损伤(PLC),5膝伴内侧半月板破裂,4膝伴外侧半月板损伤。27例患者于伤后3～10周在关节镜下行膝关节前、后交叉韧带联合重建。结果:本组术后早期均未发生严重并发症。术后随访12～88个月,平均(42.67±3.34)个月,Lysholm膝关节功能评分为78～93分,平均(86.67±5.21)分。国际膝关节文件编制委员会(IKDC)综合评定由术前显著异常(D级)28膝,改进为随访时正常(A级)9膝、接近正常(B级)16膝、异常(C级)3膝。结论:关节镜下膝关节前交叉韧带(ACL)与后交叉韧带(PCL)同时重建创伤小、手术操作精细,术后膝关节功能恢复满意。     

Mechanical properties of anterior malleolar ligament from experimental measurement and material modeling analysis

In this paper, mechanical properties of the anterior malleolar ligament (AML) of human middle ear were studied through the uniaxial tensile, stress relaxation and failure tests. The digital image correlation (DIC) method was used to assess the boundary effect in experiments and calculate the strain on specimens. The constitutive behavior of the AML was described by a transversely isotropic hyperelastic model which consists of a first-order Ogden model augmented by a I (4)-type reinforcing term. The material parameters of the model were estimated and the viscoelasticity of the AML was illustrated by hysteresis phenomena and stress relaxation function. The mechanical strength of the AML was obtained through the failure test and the mean ultimate stress and stretch ratio were measured as 1.05 MPa and 1.51, respectively. Finally, a linear Young's modulus-stress relationship of the AML was derived based on constitutive equation of the AML within a stress range of 0-0.5 MPa.     

Mechanical properties of radiation-sterilised human Bone-Tendon-Bone grafts preserved by different methods

Patellar tendon auto- and allo-grafts are commonly used in orthopedic surgery for reconstruction of the anterior cruciate ligaments (ACL). Autografts are mainly used for primary reconstruction, while allografts are useful for revision surgery. To avoid the risk of infectious disease transmission allografts should be radiation-sterilised. As radiation-sterilisation supposedly decreases the mechanical strength of tendon it is important to establish methods of allograft preservation and sterilisation assuring the best quality of grafts and their safety at the same time. Therefore, the purpose of this study was to compare the tensile strength of human patellar tendon (cut out as for ACL reconstruction), preserved by various methods (deep fresh freezing, glycerolisation, lyophilisation) and subsequently radiation-sterilised with doses of 0, 25, 50 or 100 kGy. Bone-Tendon-Bone grafts (BTB) were prepared from cadaveric human patella tendons with both patellar and tibial attachments. BTB grafts were preserved by deep freezing, glycerolisation or lyophilisation and were subsequently radiation-sterilised with doses of 0 (control), 25, 50 or 100 kGy. All samples were subjected to mechanical failure tensile tests with the use of Instron system in order to estimate their mechanical properties. All lyophilised grafts were rehydrated before performing of those tests. Obtained mechanical tests results of examined grafts suggest that deep-frozen irradiated grafts retain their initial mechanical properties to an extent which does not exclude their clinical application. All conducted experiments were approved by the Local Ethical Committee.     

关节镜下多种移植物联合重建膝关节前、后交叉韧带

目的：评估关节镜下膝关节前交叉韧带（ACL）与后交叉韧带（PCL）同时重建的技术和临床效果。方法：自2003年6月～2009年10月,27例病人（28膝）经MRJ检查及关节镜检查证实ACL和PCL均断裂,其中9膝伴内侧副韧带损伤（MCL）,8膝伴后外侧角损伤（PLC）,5膝伴内侧半月板破裂,4膝伴外侧半月板损伤。27例患者于伤后3～10周在关节镜下行膝关节前、后交叉韧带联合重建。结果：本组术后早期均未发生严重并发症。术后随访12-88个月,平均（42．67±3．34）个月,Lysholm膝关节功能评分为78-93分,平均（86．67±5．21）分。国际膝关节文件编制委员会（mDC）综合评定由术前显著异常（D级）28膝,改进为随访时正常（A级）9膝、接近正常（B级）16膝、异常（C级）3膝。结论：关节镜下膝关节前交叉韧带（ACL）与后交叉韧带（PCL）同时重建创伤小、手术操作精细,术后膝关节功能恢复满意。     

Primary and secondary restraints of human and ovine knees for simulated in vivo gait kinematics

Knee soft tissue structures are frequently injured, leading to the development of osteoarthritis even with treatment. Understanding how these structures contribute to knee function during activities of daily living (ADLs) is crucial in creating more effective treatments. This study was designed to determine the role of different knee structures during a simulated ADL in both human knees and ovine stifle joints. A six degree-of-freedom robot was used to reproduce each species’ in vivo gait while measuring three-dimensional joint forces and torques. Using a semi-randomized selective cutting method, we determined the primary and secondary structures contributing to the forces and torques along and about each anatomical axis. In both species, the bony interaction, ACL, and medial meniscus provided most of the force contributions during stance, whereas the ovine MCL, human bone, and ACLs of both species were the key contributors during swing. This study contributes to our overarching goal of establishing functional tissue engineering parameters for knee structures by further validating biomechanical similarities between the ovine model and the human to provide a platform for measuring biomechanics during an in vivo ADL. These parameters will be used to develop more effective treatments for knee injuries to reduce or eliminate the incidence of osteoarthritis.     

关节镜下胫骨嵌入术治疗膝关节后交叉韧带损伤的临床效果及安全性分析

目的：探讨关节镜下胫骨嵌入术治疗膝关节后交叉韧带损伤患者的临床疗效及安全性。方法：回顾性分析2013 年2 月至 2014 年2 月在我院接受关节镜下胫骨嵌入术治疗的膝关节膝关节后交叉韧带损伤患者36 例的临床资料，比较手术前后 Lysholm 膝关节评分、KT-2000 关节测量值、后抽屉试验与Lachman 征的差异。结果：与手术前比较，手术后6 个月患膝Lysholm 膝关节评分、KT-2000 关节测量值及物理检查(后抽屉试验试验与Lachman 征)均明显改善，差异具有统计学意义(P<0.05)。全部患 者术后无韧带断裂、免疫排斥反应等现象。结论：关节镜下胫骨Inlay技术对膝关节PCL损伤患者的临床疗效显著，安全性高，值 得临床推广应用。     

New parameters describing how knee ligaments carry force in situ predict interspecimen variations in laxity during simulated clinical exams

Knee laxity, defined as the net translation or rotation of the tibia relative to the femur in a given direction in response to an applied load, is highly variable from person to person. High levels of knee laxity as assessed during routine clinical exams are associated with first-time ligament injury and graft reinjury following reconstruction. During laxity exams, ligaments carry force to resist the applied load; however, relationships between intersubject variations in knee laxity and variations in how ligaments carry force as the knee moves through its passive envelope of motion, which we refer to as ligament engagement, are not well established. Thus, the objectives of this study were, first, to define parameters describing ligament engagement and, then, to link variations in ligament engagement and variations in laxity across a group of knees. We used a robotic manipulator in a cadaveric knee model (n = 20) to quantify how important knee stabilizers, namely the anterior and posterior cruciate ligaments (ACL and PCL, respectively), as well as the medial collateral ligament (MCL) engage during respective tests of anterior, posterior, and valgus laxity. Ligament engagement was quantified using three parameters: (1) in situ slack, defined as the relative tibiofemoral motion from the neutral position of the joint to the position where the ligament began to carry force; (2) in situ stiffness, defined as the slope of the linear portion of the ligament force–tibial motion response; and (3) ligament force at the peak applied load. Knee laxity was related to parameters of ligament engagement using univariate and multivariate regression models. Variations in the in situ slack of the ACL and PCL predicted anterior and posterior laxity, while variations in both in situ slack and in situ stiffness of the MCL predicted valgus laxity. Parameters of ligament engagement may be useful to further characterize the in situ biomechanical function of ligaments and ligament grafts.     

Can altered neuromuscular coordination restore soft tissue loading patterns in anterior cruciate ligament and menisci deficient knees during walking?

Injuries to the anterior cruciate ligament (ACL) and menisci commonly lead to early onset osteoarthritis. Treatments that can restore normative cartilage loading patterns may mitigate the risk of osteoarthritis, though it is unclear whether such a goal is achievable through conservative rehabilitation. We used musculoskeletal simulation to predict cartilage and ligament loading patterns during walking in intact, ACL deficient, menisci deficient, and ACL-menisci deficient knees. Stochastic simulations with varying coordination strategies were then used to test whether neuromuscular control could be modulated to restore normative knee mechanics in the pathologic conditions. During early stance, a 3 mm increase in anterior tibial translation was predicted in the ACL deficient knee. Mean cartilage contact pressure increased by 18% and 24% on the medial and lateral plateaus, respectively, in the menisci deficient knee. Variations in neuromuscular coordination were insufficient to restore normative cartilage contact patterns in either the ACL or menisci deficient knees. Elevated cartilage contact pressures in the pathologic knees were observed in regions where cartilage wear patterns have previously been reported. These results suggest that altered cartilage tissue loading during gait may contribute to region-specific degeneration patterns, and that varying neuromuscular coordination in isolation is unlikely to restore normative knee mechanics.     

Influence of material properties and photocatalysis on phototrophic growth in multi-year roof weathering

Phototrophic growth on roofs leads to weathering and impacts their appearance. Roof tiles with various properties are available (natural clay, engobed, varnished or coated with photocatalytic TiO₂). The aim of this study was to examine the influence of materials on the development of phototrophic biofilms. Roof tiles were weathered in six climatic regions in Germany for several years. Phototrophic biomass was periodically determined by PAM-fluorometry, image analysis, and visual evaluation. Roof tiles of natural clay were the most heavily infested, while black varnished roof tiles were hardly covered with any phototrophs. This colonisation pattern was compared to water availability on roof tiles surfaces. In contrast to rough natural clay, varnished black tiles accumulated less water, dried quickly, and were rather resistant to phototrophs. The photocatalytic coating was not effective against phototrophic growth. Materials with appropriate properties may prevent phototrophic growth without biocides through reduced water absorption capacities and by avoiding radiation protected structures.     

Effect of arabinose substitution on the material properties of arabinoxylan films

This study was undertaken to investigate the effect of arabinose content on film properties. The substrate used was a rye arabinoxylan that had an Ara/Xyl ratio of 0.52 and an average number molecular weight of 305 kDa. Oxalic acid was used to attempt selective removal of the arabinose substituents on the xylan main chain. The debranching of the polymer was coupled with a decrease in molecular weight. The effect of reaction conditions on the decrease in arabinose content and loss of molecular weight was investigated. Optimal conditions were selected using an experimental design. Treatment at lower temperature for longer period of times resulted in debranching with less degradation of the main chain. As the Ara/Xyl ratio was lowered, aggregates began to form in an interval of the Ara/Xyl ratio between 0.31 and 0.23 in a water solution. Precipitation occurred below an Ara/Xyl ratio of 0.1. Thus, removal of arabinose substituents results in a gradual association of unsubstituted chains. There is a linear correlation between arabinose substitution and the moisture content of arabinoxylan at 98% RH. A decrease in arabinose content resulted in the loss of a plasticizing effect, as determined by dynamic mechanical analysis, which is correlated to water binding capacity.     

A comprehensive experimental study on material properties of human brain tissue

A comprehensive study on the biomechanical response of human brain tissue is necessary to investigate traumatic brain injury mechanisms. Published brain material property studies have been mostly performed under a specific type of loading, which is insufficient to develop accurate brain tissue constitutive equations. In addition, inconsistent or contradictory data in the literature made it impossible for computational model developers to create a single brain material model that can fit most, if not all, experimental results.     

The relationship of whole human vertebral body creep to geometric,microstructural, and material properties

Creep, the time dependent deformation of a structure under load, is an important viscoelastic property of bone and may play a role in the development of permanent deformity of the vertebrae in vivo leading to clinically observable spinal fractures. To date, creep properties and their relationship to geometric, microstructural, and material properties have not been described in isolated human vertebral bodies. In this study, a range of image-based measures of vertebral bone geometry, bone mass, microarchitecture and mineralization were examined in multiple regression models in an effort to understand their contribution to creep behavior. Several variables, such as measures of mineralization heterogeneity, average bone density, and connectivity density persistently appeared as significant effects in multiple regression models (adjusted r²: 0.17–0.56). Although further work is needed to identify additional tissue properties to fully describe the portion of variability not explained by these models, these data are expected to help understand mechanisms underlying creep and improve prediction of vertebral deformities that eventually progress to a clinically observable fracture.     

Macroscopic anisotropic bone material properties in children with severe osteogenesis imperfecta

Children with severe osteogenesis imperfecta (OI) typically experience numerous fractures and progressive skeletal deformities over their lifetime. Recent studies proposed finite element models to assess fracture risk and guide clinicians in determining appropriate intervention in children with OI, but lack of appropriate material property inputs remains a challenge. This study aimed to characterize macroscopic anisotropic cortical bone material properties and investigate relationships with bone density measures in children with severe OI. Specimens were obtained from tibial or femoral shafts of nine children with severe OI and five controls. The specimens were cut into beams, characterized in bending, and imaged by synchrotron radiation X-ray micro-computed tomography. Longitudinal modulus of elasticity, yield strength, and bending strength were 32–65% lower in the OI group (p < 0.001). Yield strain did not differ between groups (p ≥ 0.197). In both groups, modulus and strength were lower in the transverse direction (p ≤ 0.009), but anisotropy was less pronounced in the OI group. Intracortical vascular porosity was almost six times higher in the OI group (p < 0.001), but no differences were observed in osteocyte lacunar porosity between the groups (p = 0.086). Volumetric bone mineral density was lower in the OI group (p < 0.001), but volumetric tissue mineral density was not (p = 0.770). Longitudinal OI bone modulus and strength were correlated with volumetric bone mineral density (p ≤ 0.024) but not volumetric tissue mineral density (p ≥ 0.099). Results indicate that cortical bone in children with severe OI yields at the same strain as normal bone, and that their decreased bone material strength is associated with reduced volumetric bone mineral density. These results will enable the advancement of fracture risk assessment capability in children with severe OI.     

Comparison of elastic,viscoelastic and failure tensile material properties of knee ligaments and patellar tendon

The knee ligaments and patellar tendon function in concert with each other and other joint tissues, and are adapted to their specific physiological function via geometry and material properties. However, it is not well known how the viscoelastic and quasi-static material properties compare between the ligaments. The purpose of this study was to characterize and compare these material properties between the knee ligaments and patellar tendon.Dumbbell-shaped tensile test samples were cut from bovine knee ligaments (ACL, LCL, MCL, PCL) and patellar tendon (PT) and subjected to tensile testing (n = 10 per ligament type). A sinusoidal loading test was performed at 8% strain with 0.5% strain amplitude using 0.1, 0.5 and 1 Hz frequencies. Subsequently, an ultimate tensile test was performed to investigate the stress-strain characteristics.At 0.1 Hz, the phase difference between stress and strain was higher in LCL compared with ACL, PCL and PT (p < 0.05), and at 0.5 Hz that was higher in LCL compared with all other ligaments and PT (p < 0.05). PT had the longest toe-region strain (p < 0.05 compared with PCL and MCL) and MCL had the highest linear and strain-dependent modulus, and toughness (p < 0.05 compared with ACL, LCL and PT).The results indicate that LCL is more viscous than other ligaments at low-frequency loads. MCL was the stiffest and toughest, and its modulus increased most steeply at the toe-region, possibly implying a greater amount of collagen. This study improves the knowledge about elastic, viscoelastic and failure properties of the knee ligaments and PT.     

Cyclic cryopreservation affects the nanoscale material properties of trabecular bone

Tissues such as bone are often stored via freezing, or cryopreservation. During an experimental protocol, bone may be frozen and thawed a number of times. For whole bone, the mechanical properties (strength and modulus) do not significantly change throughout five freeze-thaw cycles. Material properties at the trabecular and lamellar scales are distinct from whole bone properties, thus the impact of freeze-thaw cycling at this scale is unknown. To address this, the effect of repeated freezing on viscoelastic material properties of trabecular bone was quantified via dynamic nanoindentation. Vertebrae from five cervine spines (1.5-year-old, male) were semi-randomly assigned, three-to-a-cycle, to 0–10 freeze-thaw cycles. After freeze-thaw cycling, the vertebrae were dissected, prepared and tested. ANOVA (factors cycle, frequency, and donor) on storage modulus, loss modulus, and loss tangent, were conducted. Results revealed significant changes between cycles for all material properties for most cycles, no significant difference across most of the dynamic range, and significant differences between some donors. Regression analysis showed a moderate positive correlation between cycles and material property for loss modulus and loss tangent, and weak negative correlation for storage modulus, all correlations were significant. These results indicate that not only is elasticity unpredictably altered, but also that damping and viscoelasticity tend to increase with additional freeze-thaw cycling.     

Effect of posterior cruciate ligament creep on muscular co-activation around knee: A pilot study

The effect of posterior cruciate ligament (PCL) on muscle co-activation (MCO) is not known though MCO has been extensively studied. The purpose of the study was to investigate the effect of PCL creep on MCO and on joint moment around the knee. Twelve males and twelve females volunteered for this study. PCL creep was estimated via tibial posterior displacement which was elicited by a 20 kg dumbbell hanged on horizontal shank near patella for 10 min. Electromyography activity from both rectus femoris and biceps femoris as well as muscle strength on the right thigh was recorded synchronically during knee isokinetic flexion–extension performance in speed of 60 deg/s as well as 120 deg/s on a dynamometer before and after PCL creep. A one-way ANOVA with repeated measures was used to evaluate the effect of creep, gender and speed. The results showed that significant tibial posterior displacement was found (p = 0.01) in both male and female groups. No significant increase of joint moment was found in flexion as well as in extension phase in both female and male groups. There was a significant effect of speed (p = 0.036) on joint moment in extension phase. Co-activation index (CI) decreased significantly (p = 0.049) in extension phase with a significant effect of gender (p ⩽ 0.001). It was concluded that creep developed in PCL due to static posterior load on the proximal tibia could significantly elicit the increase of the activation of agonist muscles but with no compensation from the antagonist in flexion as well as in extension phase. The creep significantly elicited the decrease of the antagonist–agonist CI in extension phase. MCO in females was reduced significantly in extension phase. It was suggested that PCL creep might be one of risk factors to the knee injury in sports activity.     

Quantifying differences in the material properties of the fiber regions of the pectoralis major using ultrasound shear wave elastography

The sternocostal and clavicular regions of the pectoralis major are independently harvested to provide shoulder stability, but surgical decision making does not consider the biomechanical consequences that disinsertion of one fiber region over the other has on shoulder function. Differences in material properties between the fiber regions could influence which tissue is more optimal for surgical harvesting. The current study utilized ultrasound shear wave elastography (SWE) to investigate whether the in vivo material properties differ between the fiber regions. Shear wave velocities (SWVs) were collected from the sternocostal and clavicular fiber regions of the pectoralis major from ten healthy young male participants. Participants produced isometric shoulder torques of varying magnitudes (passive, 15%, and 30% MVC) and directions (horizontal and vertical adduction). Four shoulder positions encompassing different vertical abduction and external rotation angles were examined. One-way ANOVAs tested the hypotheses that differences in SWVs during rest existed between the fiber regions as a function of shoulder position, and differences in SWVs during contraction existed as a function of shoulder position and torque direction. In all shoulder positions, the clavicular region exhibited greater SWVs during rest than the sternocostal region (P < 0.001). In shoulder positions that did not include external rotation, the clavicular region exhibited greater SWVs during contraction when producing horizontal adduction torques (P < 0.001), while the sternocostal region exhibited greater SWVs during contraction when producing vertical adduction torques at 30% MVC (P < 0.01). Our results suggest that each fiber region of the pectoralis major provides unique contributions to passive and active shoulder function.     

The evolution of tendon--morphology and material properties

Phylogenetically, tendinous tissue first appears in the invertebrate chordate Branchiostoma as myosepta. This two-dimensional array of collagen fibers is highly organized, with fibers running along two primary axes. In hagfish the first linear tendons appear and the myosepta have developed specialized regions with unidirectional fiber orientation-a linear tendon within the flat sheet of myoseptum. Tendons react to compressive load by first forming a fibrocartilaginous pad, and under severe stress, sesamoid bones. Evidence for this ability to react to load first arises in the cartilaginous fish, here documented in a tendon from the jaw of a hard-prey crushing stingray. Sesamoid bones are common in bony fish and also in tetrapods. Tendons will also calcify under tensile loads in some groups of birds, and this reaction to load is seen in no other vertebrates. We conclude that the evolutionary history of tendon gives us insight into the use of model systems for investigating tendon biology. Using mammal and fish models may be more appropriate than avian models because of the apparent evolution of a novel reaction to tensile loads in birds.