Ultrastructural visualization of carbohydrates in oxytalan fibers in monkey periodontal ligaments

Fullmer's oxytalan fibers appear to be special connective tissue fibers belonging to elastic system fibers. We have ultrastructurally examined carbohydrates in oxytalan fibers in monkey periodontal ligaments after glutaraldehyde fixation and ethylenediaminetetraacetic acid (EDTA) decalcification using: Thiéry's periodic acid-thiocarbohydrazide-silver proteinate (PA-TCH-SP) method for thin-section staining of vicinal glycol-containing complex carbohydrates, and the concanavalin A-ferritin (Con A-ferritin) and Con A-horseradish peroxidase (Con-A-HRP) en bloc staining methods specific for alpha-D-mannosyl and alpha-D-glucosyl groups. PA-TCH-SP stained collagen fibrils weakly to moderately and stained oxytalan fibers moderately. Con A-ferritin and Con A-HRP stained collagen fibrils weakly or moderately and stained oxytalan fibers intensely within the superficial region of specimen blocks. The penetration of staining reagents was improved by prior saponin treatment and/or chondroitinase ABC digestion. Thus, these studies demonstrate that PA-TCH-SP and Con A staining of carbohydrates is very useful in identifying oxytalan fibers at the ultrastructural level and that more carbohydrate components are present in oxytalan fibers than in collagen fibrils.     

Cutaneous ligaments of the human hand

A topographical study concerning the cutaneous ligaments of adult as well as human fetal hands was performed. In order to be able to preserve the cutaneous ligaments in their entirety two different methods, a careful dissection and a new histological technique, have been employed. The results of these methods are compared and the detailed topography of the different cutaneous ligaments is clarified. In addition to topographical details, the functional co-operation of the ligaments especially in regard to their clinical relevance is reported.     

Elastic fibers in the anulus fibrosus of the dog intervertebral disc

A light microscopic investigation of the anulus fibrosus in cervical intervertebral discs of the dog was conducted to ascertain the arrangement and distribution of elastic fibers. Elastic fibers were observed in all lamellae of the anulus fibrosus. However, collagenous fibers were the predominant type of connective tissue fiber, and elastic fibers were randomly dispersed among them. Intralamellar (collagenous and elastic) fibers were vertically and obliquely oriented in both superficial and deep lamellae of the anulus fibrosus. All intralamellar fibers were densely and regularly arranged in superficial lamellae, but they were more loosely organized in deep lamellae. A narrow border of interlamellar, elastic fibers was observed between broader, contiguous lamellae in the superficial zone of the anulus fibrosus. Interlamellar elastic fibers wer vertically and obliquely arranged in superficial lamellae; however, they were radially oriented in deep lamellae. The deepest lamella of the anulus fibrosus consisted of a loose, three-dimensional network of intermeshing collagenous and elastic fibers. These observations suggest that elastic fibers are integral components of the articular and shock absorption mechanisms of the anulus fibrosus, and the cervical intervertebral disc of the dog is a suitable model for experimental investigation of the role of elastic fibers in intervertebral disc herniation.     

A geometric theory of the equilibrium mechanics of fibers in ligaments and tendons.

This paper presents a theoretical analysis of the equilibrium mechanics of bending and twisting fiber geometries in ligaments and tendons. The theory predicts that the bending of loaded fibers is necessarily accompanied by large transverse pressures and pressure gradients. The predicted pressures are especially large at the bone tunnel entries of ligament grafts, where they can equal or exceed the applied tensile loads. Experimental measurements of internal pressures confirm these predictions.     

Deformation and stress distribution of the human foot after plantar ligaments release: A cadaveric study and finite element analysis

The majority of foot deformities are related to arch collapse or instability, especially the longitudinal arch. Although the relationship between the plantar fascia and arch height has been previously investigated, the stress distribution remains unclear. The aim of this study was to explore the role of the plantar ligaments in foot arch biomechanics. We constructed a geometrical detailed three-dimensional (3-D) finite element (FE) model of the human foot and ankle from computer tomography images. The model comprised the majority of joints in the foot as well as bone segments, major ligaments, and plantar soft tissue. Release of the plantar fascia and other ligaments was simulated to evaluate the corresponding biomechanical effects on load distribution of the bony and ligamentous structures. These intrinsic ligaments of the foot arch were sectioned to simulate different pathologic situations of injury to the plantar ligaments, and to explore bone segment displacement and stress distribution. The validity of the 3-D FE model was verified by comparing results with experimentally measured data via the displacement and von Mise stress of each bone segment. Plantar fascia release decreased arch height, but did not cause total collapse of the foot arch. The longitudinal foot arch was lost when all the four major plantar ligaments were sectioned simultaneously. Plantar fascia release was compromised by increased strain applied to the plantar ligaments and intensified stress in the midfoot and metatarsal bones. Load redistribution among the centralized metatarsal bones and focal stress relief at the calcaneal insertion were predicted. The 3-D FE model indicated that plantar fascia release may provide relief of focal stress and associated heel pain. However, these operative procedures may pose a risk to arch stability and clinically may produce dorsolateral midfoot pain. The initial strategy for treating plantar fasciitis should be non-operative.     

Trace elements in human tendons and ligaments

Tendons and ligaments are key structures in promoting joint movement and maintaining joint stability. Although numerous reviews have detailed their structure, molecular composition, and biomechanical properties, far less attention has been paid to their content of trace elements. Tendons and ligaments are generally rich in calcium, sulfur, and phosphorus, although there are intriguing differences between one tendon/ligament and another. Furthermore, there can be significant regional variations that correlate with the presence or absence of fibrocartilage in the “wraparound” regions of tendons or ligaments, where they change direction and press against bone. Here, their sulfate and calcium contents are particularly high. This is undoubtedly associated with the high levels of proteoglycans that are found in these cartilaginous tissues and the occasional presence of sesamoid bones within them.     

Rheological properties of the human lumbar spine ligaments

The purpose of this study is to provide a better understanding of the rheological properties of the lumbar spinal ligaments under subfailure physiological loads. Non-destructive tests including an hysteresis experiment, stress-relaxation and stepwise load-relaxation tests were used to investigate the time-dependent properties of the interspinous-supraspinous ligament complex. Using a reduced relaxation function, the viscoelastic behaviour over the experimental time-scale was described by a linear function of the logarithm of time. Internal damping of ligament substance dissipates about 36% of the mechanical energy applied during physiological loading. Local elastic stiffness is found to be two to four times global stiffness of the bone-ligament-bone complex. These physical parameters (stiffness, energy dissipation, hysteresis, relaxation, etc) can be used to improve computer models of the lumbar spinal column.     

Structure-function relationship of human spinal ligaments

A combination of light, scanning and transmission electron microscopy was used to investigate the morphology and ultrastructure of normal human spinal ligaments sampled from adult surgical specimens. The ligamenta flava consist mostly of dense elastic fibers, whereas the supraspinous and interspinous ligaments are preponderantly collagenous. In all ligaments, the collagen fascicles are characterized by a regular crimp structure. The inner collagen fibers of interspinous ligaments tend to be oriented parallel to the spinous processes while those of the peripheral layers run in postero-cranial direction. The presence of proteoglycan filaments is clearly demonstrated in all of the ligaments examined. They are mainly located at the d band of the collagen fibrils. These findings are discussed in relation to the function of the posterior ligamentous system. It is suggested that the interspinous ligaments are able to transmit tension from the thoracolumbar fascia to the spine. Finally, the spinal ligaments are thought to be involved in the control mechanism of the spine.     

Elastic properties of the hind foot of the Donkey, Equus asinus

The elastic properties of the hind feet of Donkeys, and of tendons removed from the feet, have been investigated by methods similar to those used in a previous study of the forefoot. The elastic strain energy stored in the foot, during a trotting step, is calculated to be approximately the optimum which would minimize the work required of the muscles in this gait.     

A biomechanical model of the foot: the role of muscles,tendons, and ligaments

A biomechanical model of the foot is developed and analyzed to determine the distribution of support under the metatarsal heads, the tension in the plantar aponeurosis, and the bending moment at each of the joints of the foot. This model is an extension of our earlier work to include the role of muscles, tendons, and ligaments. Two cases are presented: in the first the center of gravity of the body is over the mid foot, and in the second, the center of gravity is anterior, over the metatarsals, and no support is provided by the heel. The model shows the extent to which the muscles reduce the force in the supporting ligaments at each of the joints and decrease the tension in the plantar aponeurosis, and that this effect is more pronounced when the center of gravity of the body is moved forward.     

Stiffness of the ligaments of the human wrist joint.

In the present study the stiffness of the superficial ligaments of 14 human cadaver wrist joints have been determined. In these experiments the tested, fresh-frozen carpal joints are divided into a number of bone-ligament-bone complexes, which are loaded in a tensile testing machine at a rate of 66% of the ligaments' initial length per second to a maximal strain of 15%. From the force-elongation curves and ligament dimensions the tangent moduli for the ligament-bone strips are derived. The results show that, with regard to the tangent modulus, there is not a clear differentiation among ligament strips. Only the dorsal radiotriquetrum ligament (RTD) and the palmar radiocapitate ligament (RCP) appear to consist of a material of a relatively high tangent modulus, about 93 and 83 MPa, respectively. The other seven ligaments tested have similar tangent moduli, ranging from 25 to about 50 MPa.     

A framework for parametric modeling of ankle ligaments to determine the in situ response under gross foot motion

Ligament sprains account for a majority of injuries to the foot and ankle complex, but ligament properties have not been understood well due to the difficulties in replicating the complex geometry, in situ stress state, and non-uniformity of the strain. For a full investigation of the injury mechanism, it is essential to build up a foot and ankle model validated at the level of bony kinematics and ligament properties. This study developed a framework to parameterize the ligament response for determining the in situ stress state and heterogeneous force–elongation characteristics using a finite element ankle model. Nine major ankle ligaments and the interosseous membrane were modeled as discrete elements corresponding functionally to the ligamentous microstructure of collagen fibers and having parameterized toe region and stiffness at the fiber level. The range of the design variables in the ligament model was determined from existing experimental data. Sensitivity of the bony kinematics to each variable was investigated by design of experiment. The results highlighted the critical role of the length of the toe region of the ligamentous fibers on the bony kinematics with the cumulative influence of more than 95%, while the fiber stiffness was statistically insignificant with an influence of less than 1% under the given variable range and loading conditions. With the flexibility of variable adjustment and high computational efficiency, the presented ankle model was generic in nature so as to maximize its applicability to capture the individual ligament behaviors in future studies.     

Architecture of collagen fibers in the meniscus of the human knee joint, with special reference to the medial meniscus and its connection to the articular ligaments]

1. To understand the meniscus-tears the architecture of their collagenic fibers is of interest, particularly so the connection of the fibers of the medial meniscus with the collateral ligament. 2. The ligaments of 12 knee joints have been studied macroscopically and with the aid of thick serial sections under polarized light. 3. The main portion of the tibial collateral ligament passes the articular space without any connection with the capsule or the meniscus. The upper oblique portion of the ligament runs inside the external zone of the meniscus to the posterior attachment of the latter. Immediately inferior to the articular space the oblique fibers have another attachment. 4. The findings in respect of the arrangement of the fibers in the menisci differ from those in earlier studies. Only in the external zone the fibers run approximately parallel to the outer border. After leaving the external zone the fibers run in an arched way through the middle zone. In the internal zone these fibers have nearly a radial direction. 5. The architecture of the menisci is discussed under functional aspects. It does not correspond to a "spring" but to a tendon, which is extended over a hypomochlion. 6. Forms and localisations of meniscus-tears have been discussed under viewpoint of architecture and compared with clinical results: The typical tear of the posterior segment of the medial meniscus is the horizontal cleavage. The present opinion according to which longitudinal tears are the typical meniscus lesion, seems to be doubtful.     

Elastic fibers and biomechanics of the aorta: Insights from mouse studies

Elastic fibers are major components of the extracellular matrix (ECM) in the aorta and support a life-long cycling of stretch and recoil. Elastic fibers are formed from mid-gestation throughout early postnatal development and the synthesis is regulated at multiple steps, including coacervation, deposition, cross-linking, and assembly of insoluble elastin onto microfibril scaffolds. To date, more than 30 molecules have been shown to associate with elastic fibers and some of them play a critical role in the formation and maintenance of elastic fibers in vivo. Because the aorta is subjected to high pressure from the left ventricle, elasticity of the aorta provides the Windkessel effect and maintains stable blood flow to distal organs throughout the cardiac cycle. Disruption of elastic fibers due to congenital defects, inflammation, or aging dramatically reduces aortic elasticity and affects overall vessel mechanics. Another important component in the aorta is the vascular smooth muscle cells (SMCs). Elastic fibers and SMCs alternate to create a highly organized medial layer within the aortic wall. The physical connections between elastic fibers and SMCs form the elastin-contractile units and maintain cytoskeletal organization and proper responses of SMCs to mechanical strain. In this review, we revisit the components of elastic fibers and their roles in elastogenesis and how a loss of each component affects biomechanics of the aorta. Finally, we discuss the significance of elastin-contractile units in the maintenance of SMC function based on knowledge obtained from mouse models of human disease.     

Biomechanical properties of human lumbar spine ligaments.

Biomechanical properties of the six major lumbar spine ligaments were determined from 38 fresh human cadaveric subjects for direct incorporation into mathematical and finite element models. Anterior and posterior longitudinal ligaments, joint capsules, ligamentum flavum, interspinous, and supraspinous ligaments were evaluated. Using the results from in situ isolation tests, individual force-deflection responses from 132 samples were transformed with a normalization procedure into mean force-deflection properties to describe the nonlinear characteristics. Ligament responses based on the mechanical characteristics as well as anatomical considerations, were grouped into T12-L2, L2-L4, and L4-S1 levels maintaining individuality and nonlinearity. A total of 18 data curves are presented. Geometrical measurements of original length and cross-sectional area for these six major ligaments were determined using cryomicrotomy techniques. Derived parameters including failure stress and strain were computed using the strength and geometry information. These properties for the lumbar spinal ligaments which are based on identical definitions used in mechanical testing and geometrical assay will permit more realistic and consistent inputs for analytical models.     

Measurements of cross-sectional areas in selected human wrist-joint ligaments.

The cross-sectional area of a particular ligament is an important characteristic in order to establish the biomechanical properties of this ligament. Calculations of the cross-sectional areas of the ligaments of the wrist joint are made from two three-dimensional models. It is discussed that differences between the presented and the scarcely published data on cross-sectional areas are the result of different divisions of the wrist-joint ligamentous complex into separate ligaments.