人工髋关节外文文献翻译、中英文翻译

3.0 设计吧 2023-02-13 73 4 1.06MB 41 页 10光币

     Artificial hip joint
1. Introduction
It has been recognised by a good number of researchers that the computation of
the pressure distribution and contact area of artificial hip joints during daily activities
can play a key role in predicting prosthetic implant wear  [1],  [2],  [3]  and  [4]. The
Hertzian   contact   theory   has   been   considered   to   evaluate   the   contact   parameters,
namely the maximum contact pressure and contact area by using the finite element
method  [1]  and  [2]. Mak and his co-workers  [1]  studied the contact mechanics in
ceramic-on-ceramic   (CoC)  hip   implants   subjected   to   micro-separation   and   it   was
shown that contact stress increased due to edge loading and it was mainly dependent
on the magnitude of cup-liner separation, the radial clearance and the cup inclination
angle  [3]  and  [4]. In fact, Hertzian contact theory can captured slope and curvature
trends associated with contact patch geometry subjected to the applied load to predict
the   contact   dimensions   accurately   in   edge-loaded   ceramic-on-ceramic   hips  [5].
Although the finite element analysis is a popular approach for investigating contact
mechanics,   discrete   element  technique  has  also   been   employed   to predict  contact
pressure in hip joints  [6]. As computational instability can occur when the contact
nodes move near the edges of the contact elements, a contact smoothing approach by
applying   Gregory   patches   was   suggested  [7].   Moreover,   the   contributions   of
individual muscles and the effect of different gait patterns on hip contact forces are of
interest,   which   can   be   determined   by   using   optimisation   techniques   and   inverse
dynamic analyses [8] and [9]. In addition, contact stress and local temperature at the
contact region of dry-sliding couples during wear tests of CoC femoral heads can
experimentally be assessed by applying fluorescence microprobe spectroscopy  [10].
The   contact   pressure   distribution   on   the   joint   bearing   surfaces   can   be   used   to
determine  the heat  generated  by  friction   and  the volumetric  wear  of  artificial   hip
joints [11] and [12]. Artificial hip joint moment due to friction and the kinetics of hip
implant components may cause prosthetic implant components to loosen, which is one
of the main causes of failure of hip replacements. Knee and hip joints' moment values
during stair up and sit-to-stand motions can be evaluated computationally  [13]. The
effect of both body-weight-support level and walking speed was investigated on mean
peak internal joint moments at ankle, knee and hip  [14]. However, in-vivo study of
the friction moments  acting  on the  hip demands more research in order to assess
whether those findings could be generalised was carried out [15].
The   hypothesis   of   the   present   study   is   that   friction-induced   vibration   and
stick/slip friction could affect maximum contact pressure and moment of artificial hip
joints. This desideratum is achieved by developing a multibody dynamic model that is
able to cope with the usual difficulties of available models due to the presence of
muscles, tendons and ligaments, proposing a simple dynamic body diagram of hip
implant. For   this  purpose,  a cross section  through the  interface  of  ball,  stem  and

lateral soft and stiff tissues is considered to provide the free body diagram of the hip

joint. In this approach, the ball is moving, while the cup is considered to be stationary.

Furthermore, the multibody dynamic motion of the ball is formulated, taking the

friction-induced vibration and the contact forces developed during the interaction with

cup surface. In this study, the model utilises available information of forces acting at

the ball centre, as well as angular rotation of the ball as functions of time during a

normal walking cycle. Since the rotation angle of the femoral head and their first and

second derivatives are known, the equation of angular momentum could be solved to

compute external joint moment acting at the ball centre. The nonlinear governing

equations of motion are solved by employing the adaptive Runge–Kutta–Fehlberg

method, which allows for the discretisation of the time interval of interest. The

influence of initial position of ball with respect to cup centre on both maximum

contact pressure and the corresponding ball trajectory of hip implants during a normal

walking cycle are investigated. Moreover, the effects of clearance size, initial

conditions and friction on the system dynamic response are analysed and discussed

throughout this work.

2. Multibody dynamic model of the artificial hip joint

The multibody dynamic model originaly proposed by Askari et al. [16] has been

considered here to address the problem of evaluating the contact pressure and moment

of hip implants. A cross section A-A of a generic configuration of a hip joint is

depicted in the diagram of in Fig. 1, which represents a total hip replacement. Fig. 1

also shows the head and cup placed inside of the pelvis and separated from stem and

neck. The forces developed along the interface of the ball and stem are considered to

act in such a way that leads to a reaction moment, M. This moment can be determined

by satisfying the angular motion of the ball centre during a walking cycle. The

available data reported by Bergmann et al. [17] is used to define the forces that act at

the ball centre. This data was experimentally obtained by employing a force

transducer located inside the hip neck of a live patient. The information provided

deals with the angular rotation and forces developed at the hip joint. Thus, the

necessary angular velocities and accelerations can be obtained by time differentiating

the angular rotation. Besides the 3D nature of the global motion of the hip joint, in the

present work a simple 2D approach is presented, which takes into account the most

significant hip action, i.e. the flexion-extension motion. With regard to Fig. 2 the

translational and rotational equation of motion of the head, for both free flight mode

and contact mode, can be written by employing the Newton–Euler's equations [18]

and [19], yielding

equation(1)

<img height="40" border="0"

style="vertical-align:bottom" width="301" alt="View the MathML source"

title="View the MathML source" src="http://origin-ars.els-cdn.com/content/image/1-

s2.0-S0301679X13003034-si0001.gif">∑MOk=Iθ¨k,∑MO={Mk

(Rj)n×FPjtδ>0Mkδ≤0

equation(2)

<img height="41" border="0"

style="vertical-align:bottom" width="277" alt="View the MathML source"

title="View the MathML source" src="http://origin-ars.els-cdn.com/content/image/1-

s2.0-S0301679X13003034-si0002.gif">∑FX=mx¨,∑FX={fx+

(FPjt+FPjn)iδ>0fxδ≤0

equation(3)

<img height="47" border="0"

style="vertical-align:bottom" width="307" alt="View the MathML source"

title="View the MathML source" src="http://origin-ars.els-cdn.com/content/image/1-

s2.0-S0301679X13003034-si0003.gif">∑FY=my¨,∑FY={fy+

(FPjn+FPjt)jmgδ>0fyδ≤0

where <img height="18" border="0" style="vertical-align:bottom" width="16"

alt="View the MathML source" title="View the MathML source" src="http://origin-

ars.els-cdn.com/content/image/1-s2.0-S0301679X13003034-si0004.gif">FPjn and

<img height="19" border="0" style="vertical-align:bottom" width="16" alt="View

the MathML source" title="View the MathML source" src="http://origin-ars.els-

cdn.com/content/image/1-s2.0-S0301679X13003034-si0005.gif">FPjt denote the

normal and tangential contact forces developed during the contact between the ball

and cup, as it is represented in the diagram of Fig. 3. In Eqs. (1), (2) and (3), x, y and

θ are the generalised coordinates used to define the system's configuration. In turn,

variable m and I are the mass and moment of inertia of ball, respectively. The external

generalised forces are denoted by fx, fy and M and they act at the centre of the ball as

it is shown in Fig. 3. The gravitational acceleration is represented by parameter g, Rj

is the ball radius and δ represents relative penetration depth between the ball and cup

surfaces.

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摘要：

Artificialhipjoint1.IntroductionIthasbeenrecognisedbyagoodnumberofresearchersthatthecomputationofthepressuredistributionandcontactareaofartificialhipjointsduringdailyactivitiescanplayakeyroleinpredictingprostheticimplantwear[1],[2],[3]and[4].TheHertziancontacttheoryhasbeenconsideredtoevaluatethecont...

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