scholarly journals An Experimental Approach to Evaluate the Dynamic Behavior of the Human Knee

1988 ◽  
Vol 110 (1) ◽  
pp. 69-73 ◽  
Author(s):  
H. W. J. Jans ◽  
L. J. M. G. Dortmans ◽  
A. A. H. J. Sauren ◽  
A. Huson
Keyword(s):  
Experimental Approach ◽  
Function Analysis ◽  
Measuring System ◽  
Dynamic Force ◽  
Force Transmission ◽  
Human Knee ◽  
Human Knee Joint ◽  
In Vitro Investigation ◽  
Transfer Function Analysis

An experimental approach for an in vitro investigation of some aspects of dynamic force transmission through the human knee joint is presented. Essentially, the behavior of the joint was analyzed by measuring the responses to low level random excitation of the tibia while the femur was clamped. A global equilibrium position of the joint was attained by exerting static forces on the tibia via three tendinous muscle attachments. The responses to the applied dynamic loads were measured using a multi-channel dynamic measuring system and quantified by means of transfer function analysis techniques. Some preliminary experimental results are presented to illustrate the effects of variation of the direction and the magnitude of the applied dynamic and static loads.

A New Load Application System for In Vitro Study of Ligamentous Injuries to the Human Knee Joint

1995 ◽  
Vol 117 (4) ◽  
pp. 373-382 ◽  
Author(s):  
J. M. Bach ◽  
M. L. Hull
Keyword(s):  
Knee Joint ◽  
Degree Of Freedom ◽  
Load Application ◽  
Accuracy Evaluation ◽  
Application System ◽  
Human Knee ◽  
Human Knee Joint ◽  
Flexion Extension ◽  
External Loads

This paper describes the design and accuracy evaluation of a new six degree of freedom load application system for in vitro testing of the human knee joint. External loads of both polarity in all six degrees of freedom can be applied either individually or in any combination while the knee is permitted to move unconstrained in response to applied loads. The flexion/extension degree of freedom permits the full physiological range of motion. In addition to external loads, forces of the three major muscle groups (quadriceps, hamstrings, gastrocnemius) crossing the joint can be developed. Full automation and rapid convergence of loads to programmed values are achieved through a computer which feeds command signals to servo controller/electro-pneumatic servo valves. The servo valves regulate pressure to pneumatic actuators which develop the various loads. Experiments undertaken to quantify the accuracy of both load and displacement measurements reveal that errors particularly in load measurement are effectively controlled through the apparatus design.

Foot Movement and Tendon Excursion: An In Vitro Study

1994 ◽  
Vol 15 (7) ◽  
pp. 386-395 ◽  
Author(s):  
Beat Hintermann ◽  
Benno M. Nigg ◽  
Christian Sommer
Keyword(s):  
Degrees Of Freedom ◽  
Function Analysis ◽  
In Vitro Study ◽  
Tibialis Posterior ◽  
Flexor Hallucis Longus ◽  
Moment Arms ◽  
In Vitro Investigation ◽  
Flexion Extension ◽  
Tendon Excursion

The purpose of this study was to determine tendon excursions resulting from selected foot movement and to derive moment arms with respect to the eversion-inversion and flexion-extension axes of the foot. A lower legholding device with 6 degrees of freedom was used for the in vitro investigation of 15 fresh foot-leg specimens. Although high variation among the subjects existed, there was a pronounced uniformity of tendon excursion throughout a given foot eversion-inversion or flexion-extension range of motion. With reference to the tibialis posterior (1.00), average inverter moment arms with respect to the foot eversion-inversion axis were found to be as follows: flexor digitorum longus, 0.75; flexor hallucis longus, 0.62; tibialis anterior, 0.59; soleus, 0.24; extensor hallucis longus, 0.22; extensor digitorum longus, −0.26; peroneus longus, −0.82; and peroneus brevis, −0.85. A trend toward decreasing evertor/invertor moment arms was observed during the ranges of foot eversion, as well as when the foot was in flexion. Flexor and extensor moment arms were found to be substantially dependent on foot flexion-extension angle. Increasing flexor moment arms were observed when rotating the foot throughout the range from extension to flexion. The obtained results may have significant implications in foot surgery, muscle function analysis, and general considerations of foot function.

scholarly journals Individual kinetochore-fibers locally dissipate force to maintain robust mammalian spindle structure

2019 ◽  
Author(s):  
Alexandra F. Long ◽  
Pooja Suresh ◽  
Sophie Dumont
Keyword(s):  
Polymerization Rate ◽  
Dynamic Force ◽  
Force Transmission ◽  
Physical Mechanisms ◽  
Engineering Principle ◽  
Spindle Microtubules ◽  
Structural Homeostasis ◽  
Spindle Structure

AbstractAt cell division, the mammalian kinetochore binds many spindle microtubules that make up the kinetochore-fiber. To segregate chromosomes, the kinetochore-fiber must be dynamic and generate and respond to force. Yet, how it remodels under force remains poorly understood. Kinetochore-fibers cannot be reconstituted in vitro, and exerting controlled forces in vivo remains challenging. Here, we use microneedles to pull on mammalian kinetochore-fibers and probe how sustained force regulates their dynamics and structure. We show that force lengthens kinetochore-fibers by persistently favoring plus-end polymerization, not by increasing polymerization rate. We demonstrate that force suppresses depolymerization at both plus- and minus-ends, rather than sliding microtubules within the kinetochore-fiber. Finally, we observe that kinetochore-fibers break but do not detach from kinetochores or poles. Together, this work suggests an engineering principle for spindle structural homeostasis: different physical mechanisms of local force dissipation by the k-fiber limit force transmission to preserve robust spindle structure. These findings may inform how other dynamic, force-generating cellular machines achieve mechanical robustness.

scholarly journals Frequency modulation of renal myogenic autoregulation by perfusion pressure

2007 ◽  
Vol 293 (3) ◽  
pp. R1199-R1204 ◽  
Author(s):  
Xuemei Wang ◽  
Rodger D. Loutzenhiser ◽  
William A. Cupples
Keyword(s):  
Perfusion Pressure ◽  
Function Analysis ◽  
Renal Perfusion ◽  
Tubuloglomerular Feedback ◽  
Operating Frequency ◽  
Systemic Injection ◽  
Transfer Function Analysis ◽  
Blood Flow Dynamics

Recent studies of renal autoregulation have shown modulation of the faster myogenic mechanism by the slower tubuloglomerular feedback and that the modulation can be detected in the dynamics of the myogenic mechanism. Conceptual and empirical considerations suggest that perfusion pressure may modulate the myogenic mechanism, although this has not been tested to date. Here we present data showing that the myogenic operating frequency, assessed by transfer-function analysis, varied directly as a function of perfusion pressure in the hydronephrotic kidney perfused in vitro over the range from 80 to 140 mmHg. A similar result was obtained in intact kidneys in vivo when renal perfusion pressure was altered by systemic injection of NG-nitro-l-arginine methyl ester (l-NAME). When perfusion pressure was not allowed to increase, l-NAME did not affect the myogenic operating frequency despite equivalent reduction of renal vascular conductance. Blood-flow dynamics were assessed in the superior mesenteric artery before and after l-NAME. In this vascular bed, the operating frequency of the myogenic mechanism was not affected by perfusion pressure. Thus the operating frequency of the renal myogenic mechanism is modulated by perfusion pressure independently of tubuloglomerular feedback, and the data suggest some degree of renal specificity of this response.

scholarly journals Use of Tekscan pressure sensors for measuring contact pressures in the human knee joint

2015 ◽  
Vol 6 (2) ◽  
pp. 7
Author(s):  
Stijn Herregodts ◽  
Patrick De Baets ◽  
Jan Victor ◽  
Matthias Verstraete
Keyword(s):  
Pressure Sensors ◽  
Fixation Method ◽  
Unintended Effects ◽  
Human Knee ◽  
Linear Behavior ◽  
Human Knee Joint ◽  
Optimal Accuracy ◽  
The Impact ◽  
Contact Pressures

The Tekscan pressure sensor is a common instrument to quantify in vitro tibiofemoral and patellofemoral contact pressures, which helps to understand the impact of surgical intervention such as total knee arthroplasty (TKA). As a result of the non-linear behavior of the sensor, the conditioning, normalization and calibration of the sensor are critical to achieve correct measurements. In this paper, a literature review is presented that provides insight in the correct use of these sensors, resulting in optimal accuracy. To guarantee the repeatability of the measurements, a secure and correct fixation of the sensor in the joint is required. Using the sensor for intra-articular measurements induces several unintended effects, which potentially lower the accuracy of the measurement. First, the uneven surface can result in wrinkling and destruction of the sensor, in turn leading to measurement results that can be corrupted. Second, the presence of shear forces on the sensor can lead to wear of the sensor and reduction in sensitivity with loss of accuracy as a result. Also the fixation method can worsen the accuracy. In literature, a deterioration of the accuracy from 3% under optimal conditions to errors of more than 50% are reported as a result of the aforementioned effects.

Investigation of Dental Biomaterials under Load Using a Digital Image Correlation System

2013 ◽  
Vol 633 ◽  
pp. 181-185
Author(s):  
Aleksandra Milic Lemic ◽  
Ljiljana Tihacek Sojic ◽  
Ivan Tanasic ◽  
Aleksandar Subic ◽  
Dragan Grubor
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Complete Denture ◽  
Image Correlation ◽  
Measuring System ◽  
In Vitro Investigation ◽  
Edentulous Mandible ◽  
Correlation System ◽  
Edentulous Patients

The digital image correlation method was used in this study to investigate heat polymerizable acrylic resin, which is the material of choice for prosthesis in edentulous patients. The aim was to analyze and determine the force-induced displacement and strain of a complete denture in the physiological force field of edentulous patients. An acrylic lower complete denture was made for the edentulous mandible, placed on the residual ridge of the macerated mandible bone, lacquered with spray, and exposed to a force of 300 N. The Digital Image Correlation system (DIC) (GOM, Braunschweig, Germany) was used to measure the strain in the complete denture, consisting of two digital cameras and the software ARAMIS (6.2.0, Braunschweig, Germany). Both fields indicated the maximum dimensional changes occurred just below the point of force incidence. The displacement field registered movements in the range from 0.165 to 0.782 mm and the principal strain field showed strain values between 1.25 and 18.94%. In vitro investigation of the dynamic behavior of the lower complete denture under load by using the optical measuring system-DIC demonstrated that the strain/displacement alterations were generally influenced by prosthesis movement toward the residual alveolar ridge.

scholarly journals Direct Validation of Human Knee-Joint Contact Mechanics Derived From Subject-Specific Finite-Element Models of the Tibiofemoral and Patellofemoral Joints

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Wei Gu ◽  
Marcus G. Pandy
Keyword(s):  
Finite Element ◽  
Knee Joint ◽  
Contact Mechanics ◽  
Contact Pressure ◽  
Weight Bearing ◽  
Human Knee ◽  
Human Knee Joint ◽  
Joint Contact ◽  
Joint Contact Pressure

Abstract The primary aim of this study was to validate predictions of human knee-joint contact mechanics (specifically, contact pressure, contact area, and contact force) derived from finite-element models of the tibiofemoral and patellofemoral joints against corresponding measurements obtained in vitro during simulated weight-bearing activity. A secondary aim was to perform sensitivity analyses of the model calculations to identify those parameters that most significantly affect model predictions of joint contact pressure, area, and force. Joint pressures in the medial and lateral compartments of the tibiofemoral and patellofemoral joints were measured in vitro during two simulated weight-bearing activities: stair descent and squatting. Model-predicted joint contact pressure distribution maps were consistent with those obtained from experiment. Normalized root-mean-square errors between the measured and calculated contact variables were on the order of 15%. Pearson correlations between the time histories of model-predicted and measured contact variables were generally above 0.8. Mean errors in the calculated center-of-pressure locations were 3.1 mm for the tibiofemoral joint and 2.1 mm for the patellofemoral joint. Model predictions of joint contact mechanics were most sensitive to changes in the material properties and geometry of the meniscus and cartilage, particularly estimates of peak contact pressure. The validated finite element modeling framework offers a useful tool for noninvasive determination of knee-joint contact mechanics during dynamic activity under physiological loading conditions.

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