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RESEARCH PAPERS

J Biomech Eng. 1982;104(3):169-175. doi:10.1115/1.3138344.

The paper describes the results of in-vitro experiments to determine the contact areas in the elbow joint during different anatomical positions. The casting technique, using wax as a casting material, was used in this study. The shape and size of the contact areas change, in different elbow positions ranging from full extension to full flexion. The joint stability was preserved during the experiments. In full extension the area of contact was observed on the lower-medial aspect of the ulna while in other postures the pressure areas were found as a strip extending from posterolateral to anteromedial. The radio-capitulum joint also revealed contact during flexion under no externally applied loads.

Commentary by Dr. Valentin Fuster
J Biomech Eng. 1982;104(3):176-181. doi:10.1115/1.3138345.

The motion of the hand relative to a reference frame embedded in the radius is described using the screw displacement axis (SDA) concept. A three-dimensional sonic digitizer was utilized in a study of the dominant wrist of 15 normal subjects to determine the location and orientation of the SDAs based on the endpoints of flexion-extension motion (FEM) and radial-ulnar deviation (RUD) of the hand. The length of the common perpendicular between the SDAs of FEM and RUD was as large as 6 mm in some individuals; however, in some subjects the FEM SDA was distal of the RUD SDA while in others it was proximal. Considering the group of 15 subjects, the SDAs of FEM and RUD for the normal group nearly intersect in the head of the capitate in the neutrally positioned wrist and forearm.

Commentary by Dr. Valentin Fuster
J Biomech Eng. 1982;104(3):182-186. doi:10.1115/1.3138346.

Effects of the consistency variation on the peristaltic transport of a non-Newtonian power-law fluid fluid through a tube have been investigated by taking into account the existence of a peripheral layer. It is shown that the flow rate flux, for zero pressure drop, increases as the amplitude of the peristaltic wave increases but it decreases due to the pseudoplastic nature of the fluid. It is also noted that, for zero pressure drop, the flux does not depend on the consistency of peripheral layer while the friction decreases as this consistency decreases. However, for nonzero pressure drop, the flux increases and the friction force decreases as the consistency of peripheral layer fluid decreases.

Commentary by Dr. Valentin Fuster
J Biomech Eng. 1982;104(3):187-192. doi:10.1115/1.3138347.

Lateral, posterolateral, posterior, and end plate bulges in the intervertebral disks of 14 fresh human cadaver lumbar motion segments were measured. Loads were applied in compression of up to 800 N; and in right lateral bending, extension, flexion, and torsion of up to 12 Nm. Mean disk bulges up to 2.7 mm were found. Disk bulges differed little after fluid injection or after posterior element removal.

Commentary by Dr. Valentin Fuster
J Biomech Eng. 1982;104(3):193-201. doi:10.1115/1.3138348.

The in-vitro static load-displacement properties of the intact and the injured human lumber intervertebral joint have been investigated in a loading apparatus which allows entirely unconstrained relative displacement between the joint members. The spatial relative displacement produced by a given load, alone or in combination with another load (preload), were measured using 14 specimens and emphasizing strict control of the secondary variables which are known to affect the results. An attempt has been made to interpret the results in terms of the relative load-bearing roles of the disk, the facets and the posterior ligaments as a function of the type of load. The results indicate that the disk is the major load-bearing element in lateral and anterior (with respect to a fixed superior vertebra) shears, axial compression and flexion, while the facets play a major role in posterior shear and axial torque.

Commentary by Dr. Valentin Fuster
J Biomech Eng. 1982;104(3):202-208. doi:10.1115/1.3138349.

Numerical methods and the bio-heat transfer equation are employed to calculate temperature profiles in tissues subjected to nonuniform blood flow distributions, for initial and boundary conditions which simulate experimental physiological situations. Results indicate that one can infer, from sudden changes in temperature distribution, the occurrence of sudden changes in tissue blood flow. However, prediction of blood flow distribution from near equilibrium or steady-state temperature profiles is of poor resolution, and does not appear useful as a practical technique. The methods and results are useful for predictions of temperature profiles in the absence of significant endogenous or exogenous heating; they can be extended to such applications by straightforward methods.

Commentary by Dr. Valentin Fuster
J Biomech Eng. 1982;104(3):209-213. doi:10.1115/1.3138350.

I extend the theory of dash running by allowing resisting force to be proportional to any positive power of speed and by allowing the runner to be tractive-force-limited at the beginning of the dash and developable-force-limited subsequently. I solve the equation of motion and express the maximum value of developable force as a function of limiting dash velocity, resisting-force/velocity exponent, and indoor and outdoor-track asymptotic intercept times (the intercepts with the time axis of asymptotic lines that are fitted to the distance-time curves) and limiting tractive coefficients. For a 20-yr-mean world record limiting dash velocity of 10.33 m/s and indoor and outdoor asymptotic intercept times of 0.617 and 0.265 s, I find that a composite dash world record holder is tractive-force-limited on indoor tracks, that limiting indoor tractive coefficient is about 0.9, and that the maximum value of developable force exceeds 2.0 times the record holder’s weight.

Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J Biomech Eng. 1982;104(3):221-225. doi:10.1115/1.3138352.

The dynamics of retrograde coronary flow in aortic valvular stenosis was investigated in an in-vitro pulse duplicating system which had the capability of simulating coronary flow. The ventricular chamber of the pulse duplicator consisted of an opaque elastic sac molded from rubber in the shape of a left ventricle. The aortic test section consisted of an acrylic mold of the root of the aorta of a calf, which included the sinuses of Valsalva and the entrance region of both the left and right coronary arteries. Flow in the left coronary artery was modeled to deliver both a systolic and a diastolic component of flow. Studies were performed with normal porcine valves in the aortic and mitral positions and were repeated with a human stenotic valve in the aortic position. Pressures were measured in the aorta, left ventricle, and at the ostium of the left coronary artery with catheter-tip micromanometers. In the presence of a normal aortic valve, total coronary flow was adjusted to 120 ml/min of which 21 percent of the flow occurred during systole. The phasic pattern of coronary flow was similar to that shown in vivo. In the presence of a stenotic aortic valve, a small amount of retrograde coronary flow (<1 percent of total coronary flow) was observed; and this occurred during the initial phase of systole. Retrograde coronary flow during systole appears to have resulted from compression of the collapsible segment of the simulated coronary artery. This was caused by the elevated simulated intramural pressure.

Commentary by Dr. Valentin Fuster
J Biomech Eng. 1982;104(3):226-231. doi:10.1115/1.3138353.

A numerical technique is presented to evaluate and correct the zero-strain reference points determined experimentally for certain in-vivo strain rosette applications on long bones. The method is used to determine whether significant transverse stresses are present at the gage site during in-vivo activities. If transverse stresses are shown to be negligible, the experimentally determined zeroes can be appropriately adjusted to provide an increased accuracy of the strain measurements. In addition, the transverse Poisson’s ratio is calculated and can be incorporated in subsequent in-vivo stress calculations.

Commentary by Dr. Valentin Fuster
J Biomech Eng. 1982;104(3):232-237. doi:10.1115/1.3138354.

The error sensitivity in the determination of center and angle of rotations of a body joint performing planar motion is studied. A simple experiment is described to measure the errors in these two kinematic parameters as functions of errors in the input coordinates of markers. The effect of varying the marker locations and the size of motion-step is also studied. The errors in the center of rotation are found to increase dramatically when the two markers subtend angles of about 0 deg or 180 deg and when the motion step size decreases to 1 deg or less. Similar results are found for errors in the angle of rotation which, in addition, increase with decrease in the radius of the markers.

Commentary by Dr. Valentin Fuster
J Biomech Eng. 1982;104(3):238-244. doi:10.1115/1.3138355.

The specific features of turbulent flow that are likely to be damaging to the blood cells and platelets are the stresses which are intrinsic to turbulence, known as Reynolds stresses. These include normal stresses as well as shear stresses. The purpose of this study is to determine the magnitude of the turbulent stresses that may occur during ejection in the vicinity of normal and diseased aortic valves near normal pulmonary valves. Both Reynolds normal stresses and Reynolds shear stresses were calculated from velocities obtained in vitro with a laser Doppler anemometer in the region of two severely stenotic and regurgitant human aortic valves. Reynolds normal stresses were also calculated from velocities obtained with a hot-film anemometer in 21 patients in the region of normal and diseased aortic valves. In seven of these patients, it was calculated in the region of the normal pulmonary valve. The Reynolds normal stress in patients with combined aortic stenosis and insufficiency was prominently higher than in patients with normal valves. In the former, the Reynolds normal stress during ejection transiently reached 18,000 dynes/cm2 . This was in the range of the Reynolds normal stress observed in vitro. The Reynolds shear stress measured in vitro transiently reached 11,900 dynes/cm2 during ejection. Because the Reynolds normal stresses in the presence of the severely stenotic and regurgitant valves were comparable in vitro and in patients, it is likely that the Reynolds shear stress in patients is also comparable to values measured in vitro. These values were well above the stresses which, when sustained, have been shown to have a damaging effect upon blood cells and platelets.

Commentary by Dr. Valentin Fuster
J Biomech Eng. 1982;104(3):245-252. doi:10.1115/1.3138356.

The majority of twist drills used in orthopaedics are very similar to chisel pointed metal drilling bits. Modifications usually observed are reduction of the point angle to 90 deg and sometimes grinding of the entire cutting lip at 0 deg rake angle, which appeared to have been made arbitrarily without any advantage. We have attempted to design a surgical drill bit with the objective of minimization of the drilling thrust and temperature and effective removal of bone chips. Our results showed that the presence of the chisel edge was mainly responsible for increasing the thrust force and the temperature developed. The effects of a constant feed rate and thrust on the peak temperature were also examined. The combined effect of the helix and the point angles on the rake angle which in turn determines the cutting efficiency was analyzed for various types of surgical bits. Based on our results and previously published data from the literature an optimized drill bit was designed with a split point, a point angle of 118 deg, a parabolic flute, and a helix angle of 36 deg and its performance was compared with other existing surgical drill bits. For drilling in compact bone, the new design decreased the thrust load by 45 percent and the peak temperature rise by 41 percent. Simlar improvements were also recorded for drilling bone cement. The time of drilling a bone cortex was also significantly reduced and “walking” on the curved bone surface was eliminated and dimensional tolerance on hole sizes was improved. The new design is likely to reduce the time of surgery and also minimize the tissue damage.

Commentary by Dr. Valentin Fuster

TECHNICAL BRIEFS

J Biomech Eng. 1982;104(3):253-255. doi:10.1115/1.3138357.
Abstract
Topics: Muscle
Commentary by Dr. Valentin Fuster

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