A comparative study of vascular injection fluids in fresh-frozen and embalmed human cadaver forearms.

Over the years, various vascular injection products have been developed to facilitate anatomical dissections. This study aimed to compare the most commonly used vascular injection products in fresh-frozen and formalin-embalmed cadaver specimens. An overview of the properties, advantages and limitations of each substance was given, and a comparison of vascular infusion procedures in both preservation methods was made. A literature search was performed in order to identify the most commonly used vascular injection products. Acrylic paint, latex, gelatin, silicone, Araldite F and Batson's No. 17 were selected for the study. One fresh-frozen and one embalmed cadaver forearm were infused with each injection product according to a uniform protocol. The curing time, skin- and subcutaneous tissue penetration, degree of filling of the arterial tree, extravasations, consistency of the injected vessels during dissection, and the costs of each injection fluid were noted. There was a large variation between the injection fluids in processing- and curing time, colour intensity, flexibility, fragility, elasticity, strength, toxicity and costs. All fluids were suitable for infusion. The penetration of injection fluid into the skin and subcutaneous tissue was significantly better in fresh-frozen specimens (P = 0.002 and P = 0.009, respectively), with significantly smaller branches casted (P = 0.004). Vascular infusion of fresh-frozen cadaver specimens results in a significantly better filled coloured arterial tree, enabling more detail to be achieved and smaller branches casted. The biomechanical properties of fresh-frozen soft tissues are less affected compared with formalin fixation. All the injection fluids studied are suitable for vascular infusion, but their different properties ensure that certain products and procedures are more suitable for specific study purposes.

Functional evaluation of the TKA patient using the coordination and variability of rising.

A kinematic analysis of the knee function is important for the evaluation of total knee arthroplasties (TKA). We used the coordination and variability of rising from a chair as functional knee parameters. Twelve knee patients were measured prior to surgery (=pre-TKA group) and one year after surgery (=post-TKA group). A group of 15 healthy, age-matched subjects was selected as control group. The WOMAC questionnaire, frequently used by orthopaedic surgeons, was administered prior to the test. The test consisted of 10 times rising from a low chair and 10 times from a high chair. Knee and hip angles and angular velocities were measured with electrogoniometers. The relative phase (=MRP) between hip and knee was a measure for the coordination of rising and the standard deviation of the relative phase of the 10 trials (=SRP) was a measure for the variability. The coordination and variability of rising of the TKA patients were compared to the control group, and the relationship with the WOMAC questionnaire was calculated. The coordination of rising from a high chair and the variability of rising from both chair heights were significantly different for the pre-TKA group compared to the control group (p<0.05). The post-TKA group showed no significant differences with the control group, which indicates a functional recovery after TKA implantation. The functional parameters correlated adequately with the subjective WOMAC questionnaire. This study showed that our method is an objective measure of functionality and it will be worthwhile to use it as an additional evaluation tool.

The insertion geometry of the posterolateral corner of the knee.

We have quantitatively documented the insertion geometry of the main stabilising structures of the posterolateral corner of the knee in 34 human cadavers. The lateral collateral ligament inserted posterior (4.6 mm, sd 2) and proximal (1.3 mm, sd 3.6) to the lateral epicondyle of the femur and posterior (8.1 mm, sd 3.2) to the anterior point of the head of the fibula. On the femur, the popliteus tendon inserted distally (11 mm, sd 0.8) and either anterior or posterior (mean 0.84 mm anterior, sd 4) to the lateral collateral ligament. The popliteofibular ligament inserted distal (1.3 mm, sd 1.2) and anterior (0.5 mm, sd 2.0) to the tip of the styloid process of the fibula. The ligaments had a consistent pattern of insertion and, despite the variation between specimens, the standard deviations were less than the typical size of drill hole used in reconstruction of the posterolateral corner. The data provided in this study can be used in the anatomical repair and reconstruction of this region of the knee.

Gait and calf muscle endurance in patients with chronic venous insufficiency.

OBJECTIVE: To gain insight in gait and calf muscle endurance in patients with severe chronic venous insufficiency. METHODS: Fifteen patients with severe chronic venous insufficiency (healed or active ulcers) and 19 healthy controls were selected for this study. Subjects had to perform eight trials at preferred walking speed and eight trials at instructed walking speed (1.25 m/s) during which the gait parameters were recorded. The calf muscle endurance was tested by use of the heel-rise test. RESULTS: Patients had a significantly lower preferred walking speed (1.25 m/s +/- 0.31) compared with healthy controls (1.44 m/s +/- 0.0.15) (p = 0.039). During preferred walking speed patients had a wider base of support (p = 0.003), a bigger step time (p = 0.005), and a bigger stride time (p = 0.004) compared with healthy controls. At instructed walking speed only base of support was different between the two groups (p = 0.016). Patients had a significantly (p = 0.003) smaller number of heel rises (14.6 +/- 7.34), indicating decreased calf muscle endurance compared with controls (23.5 +/- 6.54). CONCLUSION: This study indicates a disturbed gait and decreased calf muscle endurance in patients with severe chronic venous insufficiency. The results of this study point to a possible role for gait and strength training in the rehabilitation process of patients with severe chronic venous insufficiency.

Coordination and stability of one-legged hopping patterns in patients with anterior cruciate ligament reconstruction: preliminary results.

OBJECTIVES: To investigate whether the intralimb coordination of the lower extremity during one-legged hopping in patients with anterior cruciate ligament reconstruction is different and less stable compared to control subjects. DESIGN: Measures of coordination dynamics are applied to study the coordination and stability of movement patterns of the knee and ankle in patients and control subjects. BACKGROUND: Due to several factors, such as loss of proprioceptive function and muscle weakness, the intralimb coordination of the lower extremity might be altered. METHODS: Seven patients and 13 healthy control subjects were instructed to hop in place on one leg for 10 seconds at a comfortable frequency for each leg separately. RESULTS AND CONCLUSIONS: The one-legged hopping movement pattern of patients with anterior cruciate ligament reconstruction one-year post-operative is different and less stable compared to healthy subjects, and thus is still impaired. RELEVANCE: This paper shows that patients, one year after reconstruction of the anterior cruciate ligament, have a different coordination pattern of the lower limb compared to a matched control group. Intersegmental coordination and stability, features that are often observed by eye during a rehabilitation process, are objectified in this study.

The role of afferent feedback in the control of hamstrings activity during human gait.

In vertebrates, possibly also in man, the pattern of activation of muscles during locomotion can be generated by the spinal cord (locomotor CPG, central pattern generator). However, sensory feedback is crucial to adapt the functioning of the CPG to the external requirements during gait. It is postulated that afferent input from skin and muscles can contribute to the EMG activation patterns as observed in various limb muscles during gait. The activity of the hamstrings at end swing may be partially due to stretch reflexes of these muscles. At end stance the hamstring activity may be assisted by reflexes from natural skin activation from the dorsum of the foot. In addition, more specific actions are also incorporated. For example, sural nerve stimulation induces an activation of biceps femoris (BF) whereas a suppression is usually obtained for semitendinosus (ST), indicating that the induced activation is aimed at exorotation of the lower leg. Similarly, the preferential activation of medial versus lateral gastrocnemius (GM versus GL) in sural nerve induced reflexes could favor such exorotation. It is concluded that the present evidence points towards a possible contribution of various reflexes to the motor output seen during gait for movements both inside and outside the sagittal plane.

An inverse dynamics modeling approach to determine the restraining function of human knee ligament bundles.

During knee motion, the fiber bundles of ligaments are nonuniformly loaded in a recruitment pattern which is different for successive knee-joint positions. As a result, the restraining functions of these ligaments are variable. To analyze the relative restraint contributions of the fiber bundles in different knee-joint positions, a new method was developed. Its application was illustrated for the cruciate ligaments of one knee-joint specimen. The methods developed to estimate bundle forces comprise five steps. First, the three-dimensional motions of a knee specimen are measured for anterior-posterior forces, using Röntgen Stereophotogrammetric Analysis. Second, bone-ligament-bone tensile tests are performed to evaluate the mechanical properties of these structures in several relative orientations of the bones. Third, multiple fiber bundles are identified in each ligament, based on the main fiber orientations. Fourth, the nonlinear force-length relationship of each functional bundle, as defined by a stiffness and a recruitment parameter, is determined by combining the multidirectional tensile tests with a multiline-element ligament model. Finally, the information obtained is combined in a whole-joint computer model of the knee, to determine the internal forces in the initial kinematic experiment, using an inverse dynamics approach. The technique appeared to be extremely time consuming and technologically involved. However, it was demonstrated to be useful and effective. The preliminary results reveal that the fiber bundle restraints are extremely sensitive to the knee flexion angle and the restraining forces are highly variable within the ligaments. For both cruciate ligaments, a gradual transition was demonstrated in load transfer from the posterior bundles to the more anteriorly positioned ones during knee flexion. Furthermore, it appeared that relatively high forces were carried by only a few fiber bundles at each flexion angle. Based on these preliminary results, it is concluded that the determination of forces in multiple ligament bundles is important for the understanding of failure mechanisms of ligaments. In particular, alternate loading of different fiber bundles suggests that successful operative reconstruction of the cruciate ligaments may not be achieved simply by a one-bundle preparation.

A global verification study of a quasi-static knee model with multi-bundle ligaments.

The ligaments of the knee consist of fiber bundles with variable orientations, lengths and mechanical properties. In concept, however, these structures were too often seen as homogeneous structures, which are either stretched or slack during knee motions. In previous studies, we proposed a new structural concept of the ligaments of the knee. In this concept, the ligaments were considered as multi-bundle structures, with nonuniform mechanical properties and zero force lengths. The purpose of the present study was to verify this new concept. For this purpose, laxity characteristics of a human knee joint were compared as measured in an experiment and predicted in a model simulation study. In the experiment, the varus-valgus and anterior-posterior laxities of a knee-joint specimen containing the ligaments and the articular surfaces only, were determined. From this knee-joint, geometric and mechanical parameters were derived to supply the parameters for a three-dimensional quasi-static knee-joint model. These parameters included (i) the three-dimensional insertion points of bundles, defined in the four major knee ligaments, (ii) the mechanical properties of these ligament, as functions of their relative insertion orientations and (iii) three-dimensional representations of the articular surfaces. With this model the experiments were simulated. If knee-model predictions and experimental results agree, then the multi-bundle ligament models are validated, at least with respect to their functional role in anterior-posterior and varus-valgus loading of the joint. The model described the laxity characteristics in AP-translation and VV-rotation of the cadaveric knee-joint specimen reasonably well. Both display the same patterns of laxity changes during knee flexion. Only if a varus moment of 8 N m was applied and if the tibia was posteriorly loaded, did the model predict a slightly higher laxity than that measured experimentally. From the model-experiment comparisons it was concluded that the proposed structural representations of the ligaments and their mechanical property distributions seem to be valid for studying the anterior-posterior and varus-valgus laxity characteristics of the human knee-joint.

Scapho-lunate dissociation and arthrodesis. An experimental study with lesions of the interosseous ligament and fusions with K-wires.

The carpal mechanism is studied during a sectioning of the ligament between the lunate and the scaphoid. A tear in this ligament is frequently observed in the clinic. After experimental lesions of this ligament, some authors say there is little effect while others report significant changes. We have conducted repetitions of these sectioning experiments using roentgen stereophotogrammetry to assess the kinematics of the carpal bones. We have found very little effect. We have also fused the scaphoid to the lunate to find out what happens to the carpal mechanism when the ligament between these bones is made stiffer. Fusion is carried out with K-wires and the effect upon the carpal mechanism is studied again. Our K-wiring of the scaphoid and lunate shows that the carpus starts to behave unpredictablely. The positions of the wires influence the outcome significantly. RELEVANCE--:The ligament between the scaphoid and the lunate has been assigned a main function in the carpal mechanism. It is still in debate, however, whether a lesion of this ligament by itself leads to the typical scapho-lunate dissociation pattern of the carpus. We have shown that a disruption of this ligament hardly influences the carpal mechanism. In time though, other ligaments may become overstretched so that finally the typical pattern may show up. K-wiring of the lunate and scaphoid to restore the connection between these bones results in a primarily unstable joint.

Characterization of the mechanical behavior of human knee ligaments: a numerical-experimental approach.

During knee-joint motions, the fiber bundles of the knee ligaments are nonuniformly loaded in a recruitment pattern, which depends on successive relative orientations of the insertion sites. These fiber bundles vary with respect to length, orientation and mechanical properties. As a result, the stiffness characteristics of the ligaments as a whole are variable during knee-joint motion. The purpose of the present study is to characterize this variable mechanical behavior. It is hypothesized that for this purpose it is essential to consider the ligaments mechanically as multi-bundle structures in which the variability in fiber bundle characteristics is accounted for, rather than as one-dimensional structures. To verify this hypothesis, bone-ligament-bone preparations of the ligaments were subjected to series of unidirectional subfailure tensile tests in which the relative insertion orientations were varied. For each individual test specimen, this series of tensile tests was simulated with a mathematical ligament model. Geometrically, this model consists of multiple line elements, of which the insertions and orientations are anatomically based. In a mathematical optimization process, the unknown stiffness and recruitment parameters of the line elements are identified by fitting the variable stiffness characteristics of the model to those of the test series. Thus, lumped parameters are obtained which describe the mechanical behavior of the ligament as a function of the relative insertion orientation. This method of identification was applied to all four knee ligaments. In all cases, a satisfactory fit between experimental results and computer simulation was obtained, although the residual errors were lower for the cruciate ligaments (1.0-2.4%) than for the collateral ligaments (3.7-8.1%). It was found that models with three or less line elements were very sensitive to geometrical parameters, whereas models with more than 7 line elements suffered from mathematical redundancy. Between 4 and 7 line elements little difference was found. It is concluded that the present ligament models can realistically simulate the variable tensile behavior of human knee ligaments. Hereby the hypothesis is verified that it is essential to consider the ligaments of the knee as multi-bundle structures in order to characterize fully their mechanical behavior.

The fibre bundle anatomy of human cruciate ligaments.

The cruciate ligaments of the knee consist of numerous fascicles, groups of which comprise fibre bundles. The stabilising function of these ligaments is established by changes in the lengths and orientations of the fascicles. Understanding the function of knee ligaments thus requires an understanding of their 3-dimensional fascicle architecture. Hitherto, the cruciate ligaments have been considered functionally as single-dimensional 'ropes' or, at the most, as consisting of anterior and posterior parts. It is evident from the appearance of these ligamentous structures, however, that fascicles in more than 2 directions are present. This study investigated how many and which fibre bundles are minimally needed to preserve the main fascicle directions in the ligaments. An anatomical analysis of the cruciate ligaments was performed using a 3-dimensional measuring device. Three anterior and 3 posterior cruciate ligaments were isolated and their fascicles measures. Based on the courses of the fascicles, fibre bundles were defined, dissected bluntly, and their corresponding insertion sites measured. Finally, the insertion sites of the bundles were connected into straight-line representations by a computer and transformed to the anatomical position of the knee, so as to be useful for functional analyses of the ligaments. It was found that 6-10 bundles are sufficient to represent the main fascicle directions of the ligaments. Although the number of fibre bundles is not identical for all ligaments, the femur and the tibia are connected in a consistent way by these bundles. Even the ways in which the fibre bundles change their interrelationship from the femoral to the tibial insertion sites are comparable. The results serve as a detailed anatomical basis for functional analyses of the cruciate ligaments.

The effect of variable relative insertion orientation of human knee bone-ligament-bone complexes on the tensile stiffness.

In order to evaluate the contribution of the knee ligaments to restrain joint motions, knowledge about their structural properties is required. Due to the variable relative insertion orientation of the ligaments during knee motion, however, different fiber bundles are recruited, each with their specific mechanical properties. Hence, the structural properties vary as a function of knee motion. For this reason, a relationship between the structural tensile properties and the relative insertion orientation is required in order to define the role of the ligaments in knee mechanics. In the present study, this relationship is determined by performing a series of tensile tests in which the relative orientations of the insertion sites of human knee bone-ligament-bone preparations were varied systematically. The experimentally obtained stiffness was significantly affected by the relative orientation of the insertion sites, but more profoundly for the anterior and posterior cruciate ligaments (ACL and PCL) as compared to the medial and lateral collateral ligaments (MCL and LCL). The average decreases in stiffness per 5 degrees tilt of the insertion sites were estimated at -11.6 +/- 3.5 N mm-1 (ACL), -20.9 +/- 2.7 N mm-1 (PCL), -2.6 +/- 0.9 N mm-1 (MCL) and -3.7 +/- 0.3 N mm-1 (LCL). For the PCL and the MCL these changes in stiffness with tilt were rather insensitive to the side of the femoral insertion site which was lifted. The ACL and the LCL, conversely, displayed significant differences in stiffness changes between the different tilt directions.(ABSTRACT TRUNCATED AT 250 WORDS)

Nonuniform distribution of collagen density in human knee ligaments.

It is generally recognized that the mechanical properties of soft connective tissues are affected by their structural components. We documented collagen density distributions in human knee ligaments to quantify differences in density within and between these ligaments. In order to explain the variations in mechanical properties within and between different knee ligaments as described in the literature, the distributions of collagen density were correlated with these biomechanical findings. Human knee ligaments were shown to be nonhomogeneous structures with regard to collagen density. The anterior bundles of all ligaments contained significantly more collagen mass per unit of volume than the posterior bundles did. The percentage differences between the anterior and posterior bundles, in relation to the posterior bundles, were about 25% for the anterior cruciate ligament (ACL) and the collateral ligaments and about 10% for the posterior cruciate ligament (PCL). Along the cruciate ligaments, the central segments had higher collagen densities than did segments adjacent to the ligament insertions (ACL 9%, PCL 24%). The collagen density in the ACL was significantly lower than that in the other ligaments. These variations within and between the ligaments correlate well with the variations in mechanical properties described in the literature; however, other structural differences have to be taken into account to fully explain the variations in mechanical properties from the structural components.

Effects of torsions in the wrist joint on carpal-bone behaviour and the radiotriquetral ligaments: an experimental study.

The orientations of the radiotriquetral ligaments in the wrist joint suggest the role of counteracting torsions in the radiocarpal joint. This is tested in a series of kinematic experiments with three specimens, the joints being forced to rotate about the longitudinal axis of the third metacarpal. The reorientations of the marked insertion sites of the dorsal and palmar radiotriquetral ligaments are assessed and related to the individual carpal-bone movements. The three specimens react similarly to the imposed torsions: a hyperpronation is related to a dorsal flexion and a hypersupination to a palmar flexion. The dorsal radiotriquetral ligaments are highly addressed during hypersupination, but the palmar ligaments show no significant elongations during hyperpronations. The mechanism of wrist joint injuries due to trauma like a fall on the outstretched hand is poorly documented. The torsions occurring during these trauma are simulated in cadaver experiments. Large effects upon the dorsal ligaments are found in comparison to the palmar ligaments. This indicates that the palmar radiotriquetral ligaments protect the joint against hyperpronations. Planning of the restoration of hand function in the injured hand should include the different roles of these two ligaments.

Carpal bone kinematics and ligament lengthening studied for the full range of joint movement.

Present data on carpal kinematics and carpal ligament behaviour are limited to flexion and deviation movements of the hand. These motions do not represent all the wrist-joint motions which are important for the activities of daily living. The goal of this project was to obtain insight into carpal kinematics and carpal ligament behaviour during motions of the hand covering the full range of motion of the wrist joint. The carpals and the ligaments of four wrist-joint specimens were provided with radiopaque markers. These joints were subjected to Röntgenstereophotogrammetric experimentation in a large number of hand positions to determine carpal positions and ligament lengths. The movements of the carpal bones were described by means of finite helical axes (FHA). It was found that the movements of the carpals in the distal row closely resemble those of the hand. Conversely, the motions of the carpals of the proximal row appeared not to be directly proportional to the hand motions and exhibited clear out-of-plane movements. Furthermore, it could be shown that movements of the hand into the ulnodorsal quadrant of the full range of hand motion corresponds to larger helical rotations and translations for most of the carpals than when the hand was moved into any other quadrant. The maximal ligament length changes determined did not exceed the length changes reported for pure flexion and pure deviation movements of the hand.

An indirect method to assess wrist ligament forces with particular regard to the effect of preconditioning.

A method has been developed to calculate the forces that are developed in the ligaments of a joint specimen during motions. This indirect method is needed since direct measurements fail in the case of small ligaments. As an example the small ligaments of the carpal joint are considered. The rationale of the method is that the force generated in a ligament depends on the amount of strain to which it is subjected and on its material characteristics. In the method presented the lengths of the ligaments are determined in vitro at several joint positions by means of röntgenstereophotogrammetry. The zero-force length and the force-elongation relationship are determined on the same ligaments isolated in a materials testing machine. Over a considerable part of the strain range the measurement errors are relatively small compared to the forces determined, less than 10%. The method is applicable to joints in situations where other measuring methods cannot be used. The present analysis shows, however, that the force values determined are susceptible to preconditioning of the ligaments. In preconditioned ligaments the forces could be up to 50% lower than in the non-preconditioned situation. This suggests that ligament forces may vary considerably in vivo, depending on the extent of preconditioning provoked by a particular function.

Strains and forces in selected carpal ligaments during in vitro flexion and deviation movements of the hand.

The forces induced in tiny wrist joint ligaments must be estimated in order to understand their role in the mechanism of the joint. We estimated forces in a number of selected ligaments in seven human wrist joint specimens, using a noninvasive method. The method is based on the rationale that the force generated in a ligament depends on its change of length with the joint under load. In vitro length changes of the ligaments were determined during flexion and deviation movements of the hand, using a roentgenstereophotogrammetric analysis technique. Subsequently, bone-ligament-bone (BLB) preparations were dissected from the specimens. From these BLB preparations the zero-force length and the force-elongation relationship were determined in a material testing machine. The forces generated in the ligaments during flexion and deviation were calculated by combining results on the in vitro ligament length changes, the zero-force length, and the force-elongation relationship. Large interspecimen variations of the force patterns were found. Due to this variability, it is not possible to obtain quantitative models for the kinetic behavior of the ligaments. However, qualitative trends could be distilled from the strain and force patterns. It is clear that for most ligaments, the zero-force lengths were not equal to the lengths they possessed in the neutral position of the hand. Furthermore, it could be shown which motions of the hand would most likely strain a particular ligament. It could be shown that the variations in the force patterns originate mainly from variations in the zero-force lengths, and from variations in the force-strain relationship between specimens.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

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.

Human carpal ligament recruitment and three-dimensional carpal motion.

In five fresh human cadaver wrist joints six carpal ligaments and seven carpal bones were marked with small, radio-opaque pellets. Using a roentgenstereophotogrammetric measuring system, the ligamentous length changes and the kinematics of carpal bones were determined in different flexion and deviation positions of the hand. The data generated by this method differ significantly from lengthening data predicted by current concepts on carpal ligament functioning. The motions of carpal bones and the lengthening of the carpal ligaments were related to each other. It appeared that most carpal ligaments lengthen only during one half of a full movement cycle. Hence, ligaments seem to constrain either a dorsal- or a palmar-directed motion of the hand, or an ulnar- or a radial-directed motion of the hand. When the hand is in maximal radial deviation or maximal palmar flexion, none of the ligaments has a greater length than in the neutral situation. The tested parts of the lunatotriquetrum palmar ligament do not lengthen during any movement of the hand. Significant lengthening relative to the neutral situation was found for the radiocapitate palmar ligament (6.5% in maximal ulnar deviation and 11.7% in maximal dorsal flexion of the hand), and for the distal string of the radiolunate palmar ligament (6.4% in maximal ulnar deviation). It was confirmed that the carpals, apart from moving in the plane in which the hand motion takes place, also execute considerable out-of-plane motions during hand motions. The combination of these experimentally and simultaneously determined data on length change and on the movements of carpal bones are found to be necessary in order to give suitable explanations for the observed separate kinematical phenomena.