Analysis of Femur Models and Boundary Conditions
Added on 2020-09-03
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3rd - 3rd Combined Musculoskeletal andFinite Element Modelling ....
3. Review of musculoskeletal and finite element analysisof the proximal femurFor the purpose of relief in hip-pain, the most successful procedure in terms of surgeryaccounts to be Total hip arthroplasty. It also proves to be helpful in the restoring-function withrespect to joint and is further contributes in improving life quality (Bachmeier et al. 2001;Karrholm et al. 2008). Despite the factor of enhancement in population, a very large amount ofpatients are generally represented by even a small percentage of arthroplasty-surgeries thathave failed. From a total of 71,400 hip replacement which occurred in the year 2008, nearly6,600 surgeries went through revision. This however occurred in the england &Wales(National Joint Registry 2009). This obtained data is higher than the one recorded in theyear 2005 wherein from a total of 62,000 hip-replacements namely 5,800 revision wereobserved (National Joint Registry 2005) . With reference to this data, the amount of people inneed of arthroplasty surgery is expected to increase (Birrell et al. 1999). There has been asignificant increase in the weight (National Joint Registry 2009) of patients as an outcome ofwhich their demographics have also changed. They are gradually becoming more young(Karrholm et al. 2008) thereby tending to be rather active. There are namely three categories wherein hip implants could be analysed. They areclinical-trials in case of patients, modelling in computational style and in-vitro lab tests. Forthe purpose of comparing three diversified implants, fixation methods, levels of activitiescontextualising patients and even certain types of surgical procedures, gait analysis & reviewsthat assess arthroplasty throughout the entire lifetime of patient can be utilised under clinical-studies which are non-invasive. On the contrary, invasive processes like radiostereometricanalysis (RSA) wherein beads of tantalum are implanted as internal-markers around joint to bereplaced, can be of use for assessing patients as well as their implants. In order to obtain detailsabout the information regarding implant displacement , RSA can be referred. However, there isan associated limitation as well. Only a selected set of patients would be taken in considerationsince the processes is of invasive nature & additionally expensive as well. Due to the studyingof patients within in-vivo, very dependable outcomes are obtained by the aid of clinical study.Despite this, the flexibility of this clinical study is still in question due to the involvement ofample confounding-variables that have potential. Adding more detail, in every study, only onevariable would be taken in consideration for investigation. In order to provide significant
outcomes of research based on statistics, large amount of patients are required as an additionalrequirement. For the purpose of finding out overall performance by a prosthesis, procedure orhospital, the most suitable measure accounts to be revision of surgery. However, on thecontrary, in order to ascertain the entire performance of the hip that has been replaced, thisproves to be rather crude procedure. It has been found out that the life quality as well as pain-levels would be measured by the aid of clinical studies (Karrholm et al. 2008). Despite this, theprocess of assessing them is considered as very difficult. Whenever a person begins to walk, the positioning of their legs get recorded by the aid of gaitanalysis. By the utilisation of force-plate, the reaction of their foot upon ground gets recorded(Section 3.2). In the duration of entire gate-cycle, joint angles could be calculated by using thisrecorded data. Furthermore, to predict joint and muscle contact-forces, musculoskeletal modelcan be taken into account (Section 3.3). For the purpose of comparing diversified hipreplacement that have occurred in total, utilisation of joint & muscle force could be done.Despite this, another disadvantage is there that only a limited amount of individuals can beassessed during the monitoring procedure of study. Ample of patients can be considered forinvestigation for hip replacement since it is not an invasive study. In order for informingexperimental & computational analysation in hip replacements, a diversified range of forcesdetermined by musculoskeletal modelling in clinical study can be utilised.The investigation of stability in case of an implant & wear upon bearing-surface areassisted through laboratory experiments. A rather greater level of flexibility is aided throughthis type of analysation in comparison to clinical study. The reason behind this is that implantsare available along with ample conditions for loading. These conditions of loading that aregoing to be used in other tests need to be obtained from other study. Adding more to this, thephenomenon of testing tends to be very expensive as well as slower in comparison tocomputational-modelling. However, ample of design range, criteria for loading & scenariosthat have to be modelled is assisted by very flexible and quick in silica analyses (Section 3.2).In this also, only limited data can be utilised and hence their validity is directly proportional toload & input-geometry. Since vast of scenarios can be investigated by aid of this modellingprocess, it is considered as good approach to examine trends. This will further assist forinvestigation of the most appropriate and relevant situation. Afterwards these could be takeninto account for comparison with other experimental or clinical study. This is mainly forevaluation of modelling process's robust nature.
3.1.Musculoskeletal analysisFor the purpose of actual occurring forces around the hip, a technique calledinstrumented– hip prostheses is usually taken in consideration (Section 2.5). However, there isa very less amount of patients who might have undergone through total hip-arthroplasty.During the process of gate, angle as well as movement at the joint could be assisted from gateanalysis (Section 2.4.1). For the purpose of predicting movements at joints, gait analysis canbe utilised by the musculoskeletal analysis of dynamic nature. The already predicted internallevel forces can be used as an prediction element within forward dynamic musculoskeletalanalysis. Despite this, even torques can be utilised instead of gait analysis for validating theformulated assumptions in movement generation. Despite this, there is no accuracy in theprocess of determining the force-production though either methods or data. Difficulty isinvolved in this procedure with respect to accuracy which further adds up errors into theanalysis. Contextualising upon inverse dynamic musculoskeletal models, in the process of gaitanalysis , role of kinetics & kinematics is there. This is done within the motion equation fordetermination of net-force as well as torque which act around the joint (Erdemir et al. 2007).For the purpose of prediction in forces regarding joint contact & muscle, optimisation is highlyrequired as observed from the outcomes through inverse dynamic analysis. 3.1.1.Inverse dynamicsBy utilising anthropometric data with respect to every modelled segment of limb,external force and kinematic-data, joint moments as well as forces are calculated throughinverse dynamics (Robertson et al. 2004). Length, mass-centre, mass as well as property ofinertia is usually included within the anthropometric data in context to every limb. Scaling ofall of these is usually done from cadaver measurement towards the obtained data from gaitanalysis. This generally takes in consideration height and weight in relation to body of subject.For the purpose of measuring velocity, position & acceleration in case of individual-limb,kinematic data is obtained via aid of markers mounted on kin within the procedure of gaitanalysis (Section 2.4.1). In order to carry the inverse dynamic analysis of an individual's lowerlimb, forces from ground reaction are also taken in consideration. For calculating torque aswell as net-joint forces, the obtained equations of motion are utilised. There is an inclusion of 3 markers attached to each of the limb-segment for capturing theorientation as well as position. Adding more to this, there are only six degree offreedom(DOF) attached to each of modelled segment. With the addition of constraints uponthe joints, there is further reduction observed.
A few coordinates measured via marker are neglected by standardized kinematic-analysiswithin inverse dynamics for the purpose of reduction in this system that is over-determinant.For calculating of joint movement from the measured data of markers, approach based uponoptimisation can be taken into account when applying towards musculoskeletal-model withinthe constraints of joints as stated by Andersen et ai. (2009). As observed from the findings,trajectories in relation to measurable markers were followed by the optimised-marker. Incomparison to markers that have been modelled as per standardized approach, the optimisedmarker provided more closer perspective with reference to trajectories. In context toacceleration of markers, the root-mean-square that is RMS observed an reduction of nearly 60% by aid of approach based upon optimisation.3.1.2.Predicted muscle and joint contact forcesThrough the aid of establishing balance among the external force acting upon each of thesegments in limbs, forces of muscles as well as joint-contact can be easily calculated. On thecontrary, in comparison to dynamic equilibrium equations, this tends to have more inclusion ofmuscles. Henceforth, in the process of relating muscular forces with accelerations of limb-segment, involved system of equations tends to be indeterminate. The prediction of individualmuscular forces can be done via aid of two methods. These methods are either by reduction inmuscle numbers within models (Paul 1966) or via aid of utilising optimisation techniques(Seireg and Arvikar 1975; Johnston et al. 1979; Brand et al. 1 986; Brand et al. 1 994; Glitschand Baumann 1 997; Stansfield et al. 2003; Lenaerts et al. 2008). Assumptions regardingmanner as per which muscles are recruited by body for calculation of muscle-force, tend to beincluded within the optimisation approach. Within the literature, there has been inclusion ofsome of the suggested criteria for optimisation. The literature has been carried on the criteriafor minimisation which is attained by either muscle-stress (Johnston et al. 1 979; Brand et al. 1986; Brand et al. 1 994; Glitsch and Baumann 1 997; Stansfield et al. 2003; Lewis et al. 2007)or even through muscle-force (Seireg and Arvikar 1973; Seireg and Arvikar 1975;Crowninshield et al. 1978; Patriarco et al. 1981; Glitsch and Baumann 1997; Rasmussen et al.2001). PCSA is the responsible entity for its normalisation. Among most of these studies,optimisation is responsible for minimising the individual-level defined criterion's sum-total(Crowinshield et al. 1978; Johnston et al. 1979; Patriarco et al. 1981; Lenaerts et al. 2008).Despite this, ample of studies have observed a rise in terms of order which is further of power2 or 3. This can be more clearly understood by an example : the studies have observed a rise in
power raised to either cubed or squared muscle-force (Brand et al. 1 986; Glitsch and Baumann1 997; Hoek van Dijke et al. 1 999). Van Bolhuis and Gielen (van Bolhuis and Gielen 1999) carried out the study in whichcomparison was done of different techniques that are used for optimization. various models ofoptimization were investigated by them by making comparison of the results of patterns ofelectromyography (EMG) pertaining to the investigation of the arm that was carried outthrough an isometric experiment. It was inferred from their research that there was nosimilarity and association between the models investigated and the activation patterns derivedfrom EMG data. but, it was found that there was no fit between the minimization of eithermetabolic consumption pf energy or sum of forces. The best match that was found for theexperimental data was that of the second order. This comprise of minimizing the sum ofsquares of muscle activation, forces, stress.For the purpose of validating their musculoskeletal model, measured hip-contact forceswere utilised by Brand et ai. (1994), Stansfield et ai. (2003) and Heller et ai. (2001). Aninstrumented hip was utilised for comparison of hip-contact force with the separate gaitanalysis which was recorded as measured by Brand et al. This was basically obtained fromthe same patient as a result of which correlation of very good quality was able to be reported.The muscle recruitment was utilised by them that further minimised muscle stress sum tht wascubed. In comparison to the measured force upon heel-strike & peaks of toe-off, hip-contactforces were predicted to be higher by approximately 0.5BW. Despite this, it is quite difficult toassess the comparison's validity. The reason is due to the non-simultaneous hip-forcemeasurement as well as motion-capture. Adding more, there were also some recorded variationin between the gait cycles. The data in context to gait analysis which was recorded insimultaneous way along-with measured hip-contact forces by use of instrumented hip-implant(Bergmann et al. 1993; 2001) was used by Stansfield et al. and Heller et al. From both thestudies, a very good quality of comparison was determined among the predicted & measuredhip-contact forces. In order to minimise sum of muscle-forces, muscle recruitment was utilisedby Heller et al. On the contrary before the reduction of forces in context to joint & muscleforces, maximised muscle-stress was minimised by Stansfield et al. The hip-contact force isgenerally better in stance in comparison to swing-phase as predicted by Heller et al. Althoughslight overestimation was done in case of the predicted force. Nearly a deviation of 33% has
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