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RESEARCH PAPERS

J Biomech Eng. 1980;102(4):277-283. doi:10.1115/1.3138223.

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.

Commentary by Dr. Valentin Fuster
J Biomech Eng. 1980;102(4):284-286. doi:10.1115/1.3138224.

Molds of arterial segments would be advantageous for in-vitro assessments of arterial flow dynamics. Previous techniques have been limited because of their technical difficulty or because they were limited to short planar segments. This paper presents a method, based on the lost wax technique, that is readily accomplished, and permits the fabrication of a mold of any arterial bed, irrespective of its complexity.

Commentary by Dr. Valentin Fuster
J Biomech Eng. 1980;102(4):287-293. doi:10.1115/1.3138225.

In this paper we consider an initially inhomogeneous adaptive elastic body subjected to a steady homogeneous stress state. The adaptive elastic body, which is a model for living bone tissue, is inhomogeneous in both its anisotropic elastic properties and its density. The principal result of the paper is the determination of the devolution of the initially inhomogeneous body to a homogeneous body under the influence of the steady homogeneous stress state. A cylindrical body that is inhomogeneous along the axis of the cylinder, but homogeneous in each transverse plane of the cylinder, is used as an example. This cylindrical body is loaded by a steady uniform stress directed along the cylindrical axis. The temporal devolution of an inhomogeneity in the initial shape of a sine wave is illustrated. As time progresses the amplitude of the sine wave decreases, rapidly at first and then more slowly. As time becomes very large the sine wave becomes a straight line signifying that the cylinder has become homogeneous.

Commentary by Dr. Valentin Fuster
J Biomech Eng. 1980;102(4):294-300. doi:10.1115/1.3138226.

Experimental data is compared with the simulated displacements from a computer program for the clinical activations of two separate orthodontic appliances undergoing a total of four separate loading conditions. Good agreement is shown over the entire range of activation. Suggestions for future strengthening of both the analytical and the experimental methods are given. An interactive design graphics system is shown to be imminently available to the research orthodontist.

Commentary by Dr. Valentin Fuster
J Biomech Eng. 1980;102(4):301-310. doi:10.1115/1.3138227.

Since the electrogoniometric method has been justified for the measurement of lower extremity joint motion, a similar device is developed for the measurement of elbow joint and forearm rotations. In this design, the axis of forearm rotation coincides with the anatomical axis which eliminates the cross talk existing in the regular triaxial goniometer. Although the axis of abduction-adduction is still offset from the elbow joint, special linkage arrangement was used to obtain equivalent motion. Experimental method was used to validate the accuracy of the device and model simulation was performed to emphasize the importance of accurate placement of the instrument on test subjects. Application of the present apparatus to normal subjects was studied to illustrate the range of elbow motion required in performing normal activities of daily living. This device is currently used in the functional evaluation of patients with elbow and forearm problems.

Commentary by Dr. Valentin Fuster
J Biomech Eng. 1980;102(4):311-317. doi:10.1115/1.3138228.

This paper describes a general technique for fitting a spatial kinematic model to an in-vivo anatomical joint under typical physiological loading conditions. The method employs a nonlinear least squares algorithm to minimize the aggregate deviation between postulated model motion and experimentally measured anatomical joint motion over multiple joint positions. Estimation of the parameters of a universal joint with skew-oblique revolutes to best reproduce wrist motion was used as an example. Experimental motion data from the right wrists of five subjects were analyzed. The technique performed very well and produced repeatable results consistent with previous biomechanical wrist findings.

Commentary by Dr. Valentin Fuster
J Biomech Eng. 1980;102(4):318-325. doi:10.1115/1.3138229.

In nonlinear mathematical models of the arterial circulation, the viscoelasticity of the vessel walls has generally been neglected or only taken into account in a highly approximate manner. A new method is proposed to simulate the nonlinear viscoelastic properties of the wall material with the aid of a convolution integral of the creep function and the pressure history. With this simulation it is possible to properly describe the measured characteristics of arterial viscoelasticity. Moreover, it is utilized in a mathematical model of arterial pulse propagation to study the influence of the internal wall friction on the shape, amplitude and mean value of pressure and flow pulses. The corresponding predictions are in much better agreement with in-vivo measurements, especially for the distal part of the circulation, than those obtained without viscoelasticity.

Commentary by Dr. Valentin Fuster
J Biomech Eng. 1980;102(4):326-331. doi:10.1115/1.3138230.

Active control of snow ski bindings is a new design concept which potentially offers improved protection from lower extremity injury. Implementation of this concept entails measuring physical variables and calculating loading and/or deformation in injury prone musculoskeletal components. The subject of this paper is definition of a biomechanical model for calculating tibia torsion based on measurements of torsion loading between the boot and ski. Previous control schemes have used leg displacement only to indicate tibia torsion. The contributions of both inertial and velocity-dependent torques to tibia loading are explored and it is shown that both these moments must be included in addition to displacement-dependent moments. A new analog controller design which includes inertia, damping, and stiffness terms in the tibia load calculation is also presented.

Commentary by Dr. Valentin Fuster
J Biomech Eng. 1980;102(4):332-339. doi:10.1115/1.3138231.

The rheological behavior of mammalian tendon is analyzed in terms of its constituents structure and their properties. The elastic fibers are assumed to be straight and linearly elastic. They are of predominant role in the low ranges of strain. The collagen fibers are nonuniformly undulated. Upon stretch they gradually become straight, thus increasing the stiffness of the tissue. They are assumed to be linearly viscoelastic with negligible bending strength. It is shown that the nonuniformity of the collagen fiber structure can account for the observed nonlinear load-strain relations as well as for the nonlinear viscoelastic behavior of the tendon. An experimental procedure is developed through which the material functions and parameters can be determined.

Commentary by Dr. Valentin Fuster

TECHNICAL BRIEFS

J Biomech Eng. 1980;102(4):340-342. doi:10.1115/1.3138232.

The purpose of this study was to investigate the characteristics of flow in a symmetrically branched tube that had an area ratio (0.8) and angle of branching (70 deg) that were comparable to the human descending aorta. Velocity profiles were measured in steady and pulsatile flow with a laser Doppler anemometer. A region of transient flow reversal was found along the outer wall during minimal flow in the pulsatile cycle. Flow separation did not occur. For both steady and pulsatile flow, the shear rates were higher along the inner wall and lower along the outer wall in the region of the vertex of the bifurcation.

Commentary by Dr. Valentin Fuster
J Biomech Eng. 1980;102(4):342-344. doi:10.1115/1.3138233.

Measurements of the steady-state leakage of the new Medical Incorporated Omniscience/tm cardiac valve prosthesis are presented. These results are compared to those obtained from the SJM bi-leaflet cardiac valve/tm. The new Omniscience/tm valve shows significantly less leakage than the bi-leaflet valve. Consideration is given to problems in similitude as well as to the general nature of the flow field.

Commentary by Dr. Valentin Fuster

BOOK REVIEWS

J Biomech Eng. 1980;102(4):345. doi:10.1115/1.3138234.
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Abstract
Commentary by Dr. Valentin Fuster
J Biomech Eng. 1980;102(4):345-346. doi:10.1115/1.3138235.
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Abstract
Commentary by Dr. Valentin Fuster

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