Stiffness of canine stifle joint ligaments at relatively high rates of elongation.

A falling-weight impact tester was developed specifically to evaluate the tensile characteristics of animal joints at high elongation rates. The tensile force and elongation in the ligaments of the canine stifle joint were measured using a force transducer, a linear variable displacement transducer, and a digital storage oscilloscope. Stiffness and elongation rates were determined at 1 mm and at 2 mm elongation. The stiffness was calculated as the slope of the force-elongation curve, and the elongation rate was calculated as the slope of the elongation-time curve. Results demonstrated that stiffness in the canine stifle joints was not affected by the rate of elongation in the 0.1 to 1.0 m/s range.     

Distinguishing biomechanical properties of intrinsic and extrinsic human wrist ligaments

Two intrinsic (scapholunate and lunotriquetral) and two extrinsic (radiolunate and radiocapitate) wrist ligaments were studied at high and low elongation rates (1 and 100 mm/min). Statistically significant differences among all four ligaments were noted for the viscoelastic and elastic components of stress versus strain for the fully recoverable strain and early permanent deformation stress for all ligaments. Intrinsic ligaments became permanently deformed at statistically significantly higher strain levels than the extrinsic ligaments and accept larger permanent deformation at strain levels below evident fiber failure. Ultimate strength data demonstrated significant rate dependency for stress and strain for all ligaments. Intrinsic ligaments failed statistically greater stress and strain levels than the extrinsic group. Some clinical implications of these findings are discussed.     

New aspects of the morphology and function of the human hip joint ligaments.

The capsular ligaments of the human hip joint were submitted to exact morphological analysis, and they proved to be multiple and numerous. We have described various ligamentous systems and their interconnections, and have suggested new terminologies and systematics. The ligaments were subjected to functional analysis by means of measuring strips to determine the positions in which the ligaments are taut. The ligament systems were all found to serve a restrictive function, and various parts of the apparatus restricted all possible movements in the hip joint. Extension is restricted by the medial iliofemoral complex, abduction by the pubofemoral ligament, and adduction by the posterior coxal ligaments and by the superior ischiofemoral ligament. Flexion is restricted by the inferior ischiofemoral ligaments, inward rotation by the superior ischiofemoral ligament, and outward rotation by the lateral iliofemoral complex. Only the ligament of the femoral head is unable to exert a restricting function, despite reaching a state of tension in extreme adduction.     

Recruitment of knee joint ligaments

On the basis of earlier reported data on the in vitro kinematics of passive knee-joint motions of four knee specimens, the length changes of ligament fiber bundles were determined by using the points of insertion on the tibia and femur. The kinematic data and the insertions of the ligaments were obtained by using Roentgenstereophotogrammetry. Different fiber bundles of the anterior and posterior cruciate ligaments and the medial and lateral collateral ligaments were identified. On the basis of an assumption for the maximal strain of each ligament fiber bundle during the experiments, the minimal recruitment length and the probability of recruitment were defined and determined. The motions covered the range from extension to 95 degrees flexion and the loading conditions included internal or external moments of 3 Nm and anterior or posterior forces of 30 N. The ligament length and recruitment patterns were found to be consistent for some ligament bundles and less consistent for other ligament bundles. The most posterior bundle of each ligament was recruited in extension and the lower flexion angles, whereas the anterior bundle was recruited for the higher flexion angles. External rotation generally recruited the collateral ligaments, while internal rotation recruited the cruciate ligaments. However, the anterior bundle of the posterior cruciate ligament was recruited with external rotation at the higher flexion angles. At the lower flexion angles, the anterior cruciate and the lateral collateral ligaments were recruited with an anterior force. The recruitment of the posterior cruciate ligament with a posterior force showed that neither its most anterior nor its most posterior bundle was recruited at the lower flexion angles. Hence, the posterior restraint must have been provided by the intermediate fiber bundles, which were not considered in the experiment. At the higher flexion angles, the anterior bundles of the anterior cruciate ligament and the posterior cruciate ligament were found to be recruited with anterior and posterior forces, respectively. The minimal recruitment length and the recruitment probability of ligament fiber bundles are useful parameters for the evaluation of ligament length changes in those experiments where no other method can be used to determine the zero strain lengths, ligament strains and tensions.     

The contribution of the cruciate ligaments to the load-displacement characteristics of the human knee joint

Human knee specimens were subjected to anterior-posterior, medial-lateral, varus-valgus, and torsional displacement tests. Loads were recorded for the intact joint and for the joint with all soft tissues cut except for the cruciate ligaments. The effect of condylar interference was determined for anterior-posterior, medial-lateral, and torsional displacements. The variation in load with flexion angle was considerable for medial-lateral (0-90-deg flexion) displacements, and less for varus-valgus (0-45-deg flexion) displacements. The cruciates were found to carry almost the entire anterior-posterior load; they carried a significant percentage of the medial-lateral load which varied considerably with flexion angle. A small, but not insignificant percentage of the varus-valgus load was carried by the cruciates and the variations with flexion angle were small. In torsion, the cruciates resisted only internal rotation. In the tested displacement ranges, condylar interference had a small effect on the medial-lateral load but did not affect anterior-posterior or torsional loads.     

The hominoid wrist joint

In a previous study of the primate wrist joint the author has shown that this articulation is uniquely modified in the Pongidae by the interposition of a meniscus between the ulnar styloid process and the carpus. This meniscus (which in gibbons contains a bony lunula) partially isolates the ulnar styloid process in a proximal synovial compartment. The human wrist joint is clearly derived from such an articulation, the proximal synovial compartment persisting as the prestyloid recess. The present paper is concerned with observations on a wider range of hominoid material. A spectrum of variations is demonstrated, largely the result of a tendency for the neomorphic meniscus to be incorporated as an integral component of the proximal articular surface, thereby progressively excluding the ulnar styloid process from the wrist joint and constricting the entrance to the proximal synovial compartment. The unique construction of the hominoid wrist joint is considered to be a specialization facilitating pronation-supination. Such free rotatory movement is a necessary prerequisite for true brachiation, and the obvious phylogenetic implication is that Homo has shared a brachiating ancestry with the Pongidae. This is convincing evidence in favour of the view that a period of brachiation provided the essential apprenticeship for the complex locomotor activities of bipedal, tool-using man.     

Anatomy of the squirrel wrist: bones, ligaments, and muscles

Anatomical differences among squirrels are usually most evident in the comparison of flying squirrels and nongliding squirrels. This is true of wrist anatomy, probably reflecting the specializations of flying squirrels for the extension of the wing tip and control of it during gliding. In the proximal row of carpals of most squirrels, the pisiform articulates only with the triquetrum, but in flying squirrels there is also a prominent articulation between the pisiform and the scapholunate, providing a more stable base for the styliform cartilage, which supports the wing tip. In the proximal wrist joint, between these carpals and the radius and ulna, differences in curvature of articular surfaces and in the location of ligaments also correlate with differences in degree and kind of movement occurring at this joint, principally reflecting the extreme dorsal flexion and radial deviation of the wrist in flying squirrels when gliding. The distal wrist joint, between the proximal and distal rows of carpals, also shows most variation among flying squirrels, principally in the articulations of the centrale with the other carpal bones, probably causing the distal row of carpal bones to function more like a single unit in some animals. There is little variation in wrist musculature, suggesting only minor evolutionary modification since the tribal radiation of squirrels, probably in the early Oligocene. Variation in the carpal bones, particularly the articulation of the pisiform with the triquetrum and the scapholunate, suggests a different suprageneric grouping of flying squirrels than previously proposed by McKenna (1962) and Mein (1970). J. Morphol. 246:85-102, 2000. Published 2000 Wiley-Liss, Inc.     

Systematic nonlinear relations between displacement amplitude and joint mechanics at the human wrist

This study quantified the systematic effects on wrist joint mechanics of changes in amplitude of displacement ranging from within the region of short-range stiffness (0.2% of resting muscle length) up to 3% of resting muscle length. The joint mechanics were modelled using a second-order system from which estimates of joint stiffness, viscosity, inertia, natural resonant frequency and damping ratio were obtained. With increasing amplitude of displacement, the stiffness decreased by 31%, the viscosity decreased by 73%, the damping ratio decreased by 71% and the resonant frequency decreased from 10.5 to 7.3 Hz. The patterns of change in joint mechanics with displacement amplitude were nonlinear but systematic and were well described by power relationships with high R(2) values. These relationships provide normative data for the adult population and may be used in the modelling of human movement, in the study of neurological disorders and in robotics where human movement is simulated. The observed patterns of high initial stiffness and viscosity, decreasing progressively as displacement amplitude increases, may provide a good compromise between postural stability and liveliness of voluntary movement.     

Features of the prosimian wrist joint in relation to hominoid specializations.

The wrist joint of lemuroid and lorisoid prosimians is examined in relation to variations among higher primates, particularly the specializations characteristic of hominoids. The lorisines Nycticebus and Perodicticus share a metrically defined primitive morphopattern with other prosimians and cercopithecine monkeys, showing little convergence on apes in carpal bone and distal radius and ulna shape.     

Anatomy of the cruciate ligaments and their function in extension and flexion of the human knee joint

The areas of the femoral origin of the cruciate ligaments have approximately the shape of sectors of ellipses, the one for the anterior ligament on the lateral condyle posteroproximally and the one for the posterior ligament on the medial condyle distally. By means of a new technique of dissection, combined with the use of X-rays, the change in distance between the origin and insertion and so the change of tension of single bundles of the ligaments could be analyzed. Only a rather thin bundle in each cruciate ligament is in constant tension: "guiding bundles." The maximal diminution of distance between the origin and insertion for some bundles is 65%. In the anterior cruciate ligament the majority of fibres are taut in extreme extension: "limiting bundles." The same is true in the posterior cruciate ligament in extreme flexion. There are also some fibres, especially in the posterior cruciate ligament, that are taut only in an intermediate position. The geometric analysis of the function of different groups of fibers was performed by a modification of Menschik's concept of a four-bar link.     

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.     

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.     

Differential metabolic responses of periarticular ligaments and tendon to joint immobilization.

Parameters of collagen metabolic behavior were analyzed in the periarticular connective tissues, i.e., medial collateral ligament (MCL), anterior cruciate ligament (ACL), and patellar tendon (PT), of control and immobilized rabbit knees. Two periods of immobilization were studied: 9 and 12 wk. Collagen turnover and collagen cross-links were quantitatively assessed in the three tissues. The results showed that after 9 wk both synthesis and degradation were significantly increased in the MCL and ACL, whereas the PT showed lesser effects. After 12 wk all three tissues experienced significant losses of collagen mass, which resulted in tissue atrophy. The concentrations of the reducible collagen cross-links dihydroxylysinonorleucine and hydroxylysinonorleucine in the immobilized MCL and ACL were greater than their respective controls, indicating an increase in collagen synthesis, whereas concentrations of the nonreducible cross-link hydroxypyridinoline were observed to be decreased in these tissues. Of the reducible cross-links in the PT, only hydroxylysinonorleucine was found to be increased over control, whereas hydroxypyridinoline was slightly less concentrated. These results taken together have demonstrated that the ligamentous tissues are more susceptible to the effects of stress deprivation secondary to joint immobilization than the PT, and, in particular, the ACL of the three tissues studied appears to be most vulnerable.     

A three-dimensional finite element analysis of the combined behavior of ligaments and menisci in the healthy human knee joint

We present here a three-dimensional FE model of the healthy human knee that included the main structures of the joint: bones, all the relevant ligaments and patellar tendon, menisci and articular cartilages. Bones were considered to be rigid, articular cartilage and menisci linearly elastic, isotropic and homogeneous and ligaments hyperelastic and transversely isotropic. Initial strains on the ligaments and patellar tendon were also considered. This model was validated using experimental and numerical results obtained by other authors. Our main goal was to analyze the combined role of menisci and ligaments in load transmission and stability of the human knee. The results obtained reproduce the complex, nonuniform stress and strain fields that occur in the biological soft tissues involved and the kinematics of the human knee joint under a physiological external load.     

Intrinsic innervation of the rat knee joint articular capsule and ligaments

In spite of the practical importance of having a detailed knowledge of knee joint innervation to understand the pathophysiologic aspects, little information is now available concerning the density and pattern of the nerve fibres which are distributed to it. The present study has been designed to investigate the density and distribution of nerve fibres and receptor corpuscles in the knee joint articular capsule, cruciate and collateral ligaments in the rat, using the acetylcholinesterase (AChE) histochemical in toto staining technique. The investigation was performed on male Wistar rats of 3 months of age, some of which had been treated with capsaicin to deplete their afferent 'C' fibres of their content of neuropeptides. AChE-positive nerve fibres and different types of receptor corpuscle endings were found within articular capsule and ligaments. The highest density of AChE-positive nerve fibres was noticeable in the fibular collateral ligament followed by the tibial collateral ligament, the posterior cruciate ligament, the anterior cruciate ligament and the articular capsule. In the articular capsule the number of type I endings was higher than in the ligaments. The opposite is true for the other type of receptor corpuscles found as well as for nerve endings. Capsaicin treatment significantly reduced the density of AChE-positive nerve fibres in knee joint ligaments but did not affect nerve fibres in the articular capsule. Moreover, it caused the disappearance of some kind of receptor corpuscles within the collateral and cruciate ligaments. The above data collectively suggest that the AChE in toto staining technique may represent a good method for investigating joint innervation and that a significant percentage of nerve fibres supplying knee joint ligaments is represented by C fibre afferents.     

The ligaments of the fingers. Anatomical study of the Cleland ligaments

The aim of this study was to establish a precise architecture of the retinacular ligaments of human digits. Sixty selected digits from human cadavers aged 40-70 years were used in this study. We were able to identify, under the dissecting microscope, two distinct ligamentous complexes: one proximal of greater importance and the other distal of lesser importance. Both structures extend from the periosteum as well as from the fibrous part of the digital sheath to the skin. There are many variations in size and in shape of these structures but they are not related to a particular digit. The role of these ligaments is to prevent the 'effet de doigt de gant', to stabilize and to maintain the neurovascular bundle of the digit at the moment of the digital flexion.