Ask a question from expert

Ask now

Total Hip Replacement Assignment

31 Pages14473 Words325 Views
   

Added on  2020-07-22

Total Hip Replacement Assignment

   Added on 2020-07-22

BookmarkShareRelated Documents
Medical Science and boneReplacement
Total Hip Replacement Assignment_1
Introduction Total Hip Replacement (THR) or Arthroplasty is the medical procedure whereindamaged cartilage and bone in the body is replaced with the prosthetic components. It is one ofthe successful surgical procedures in the field of orthopaedic surgery. Patients who are sufferinghealth issues due to osteoarthritis, congenital deformities, avascular neurosis, rheumatoidarthritis and post-traumatic disorder can get over rid of pain through hip joints restoration. THRnot only helps to reduce pain but also helps patients in better sleeping which helps in improvingtheir quality of life. Hip Joint is a kind of ball and socket (spheroidal) is a synovial joint wherein a ballshaped bone fits into another bone in cup like structure. The distal bone can easily move in allthe directions with a common center. Socket that is formed by acetabulum covers the ball shapedstructure beyond equator. Considering the structure, THR can be classified into two types; thatare cemented & cement less arthroplasties. Former consists of implant-bone fixation via usingbone cement whilst in the later, it is done through fibre-meshed and porous-coated surface. Boththe surgical procedure have their own benefits and shortcomings, still, in the practical world,THR(THA) gains high preference among surgical experts due to its biologic or natural implant-bone fixation procedure. Over last few decades, the hip replacement surgery showed an immensegrowth at the international level. Evidencing it, approximately 800,000 THR surgeries areundertaken every year around the world. During the period of 1967 to 2013, in Sweden, the datareported really high increase from only 6 to 16,330 operations whilst in US, THR surgeries
Total Hip Replacement Assignment_2
exceeded 285,000 surgeries per year however, total fractures reported by the end of year 2040 isforecasted to go beyond 500,000. Australia reported 46.50% in the hip joint surgeries from 2003and also projected the rate will go up in the forthcoming period. On the other side, in England &Wales, National Joint Registry stated 620,400 THR between the period of 2003 to 2013, whereasosteoarthritis reported 93% case. In this, the cement-less THR surgery reported increase from16.8% to 42.5% with the decline in cemented THR from 60.5% to 33.2%. In India, NationalInstitute of Arthritis reported 470,000 incidence rate per year. Out of these, 65% of the reportedsurgeries have been undertaken through cement-less. The surgical procedure reported a goodprogress and success in the past few decades at a failure estimation of 10%. The failed cases isfounded in the first revision surgery which requires revision surgery after 10 years taking intoaccount patient health conditions & implant used. Although, there are multiple of reasons behindsuch failure, still, most of the cases reported bio mechanical reasons for the same. Implantindulged adverse remodeling & excessive implant interface stress, which in turn, leads toprogressive interface debonding that have been discovered as two most important bio mechanicalreasons for failure that compromised cement fewer prostheses' durability. Besides this, lack ofstability due to excessive micro-motion has a strong influence over the cement-less arthroplastieswhich compromises biological attachment that took place between femur and implant. The mechanism's cumulative or individual effect may result in gross aseptic loosening of theimplant or in cases of extreme scenario, femur fracture. Keeping aside key aspects, including surgical procedure and patient conditions, the femoralimplant 's design or geometry is also known to be effective on these mechanisms (Huiskes andBoeklagen, 1988; Viceconti et al., 2001).Although a wide variety of cement-less femoral implants have a commercial availability in themarket (Fig. 1.1), for maximum of those the outcomes of design remain to be unexplored,primarily due to a lack in the clinical data. The mechanical designs of hip implant, thus, can beassessed preclinically and search for the optimal geometry may be conducted for theminimization of the effects of all the failure in the mechanisms.The solutions of the design of a prosthesis may be either structural or functional, or both.However, investigations of the prosthesis have been centralised mostly on the structural aspects.Considering the various structural aspects of hip prosthesis, its is determined that geometry ofthe femoral implant plays a critical role in the outcome of design. Although the gross appearanceof a femoral stem has changed hardly since it was mentioned for the first time (Gluck, 1891), theoverall shape being non-primitive hence offers a lot of scope for a complex study by profilealteration of stem transverse sections along the stem-length by usage of the state-of-the-art solidmodeling process and finite element (FE) analysis software.
Total Hip Replacement Assignment_3
Moreover, with the arrival of the technically advanced high-performance computers, largenumber of stem shapes may be assessed in a relatively small period, and one which is mostsuited may be selected on basis of its predicted outcomes of design. Therefore, a combination ofsuitable design optimization strategy with a solid modeling and FE analysis may result in a moreimproved prosthesis design.Optimization of shape (or geometry) is said to be a particular stage in structural optimization,which deals with the search of the design domain with optimal configuration of it. (Fraternali etal., 2011). In optimization of shape, introduction of design variables is done to control thegeometry of the structure and an FE model is required for methodology that changes duringoptimization process. The growth in interest of optimization of shapes reflects a realization madeby the effectiveness of changes in shape for improvement in the structural performance. Byemploying shape optimization as a design tool, evaluation of stem geometries can be done basedon bio-mechanical cost functions, framed on failure principles taken as a base. Therefore, asuitable cost function must be formed, representing the effects on global level of these failuremechanisms. It is necessary in order to search for optimal designs of the cement-less femoralimplant that would enhance prosthesis durability. However, for a priori and understanding thefailures associated with THA practically, a study on the hip joint's bio-mechanics is required.1.2.1 Anatomical planes and directionsHip joint bio-mechanics may form a basic understanding of the human anatomy. Typicalorientations of the human body of different anatomical planes are presented in the Fig. 1.2a. Thetransverse (axial or horizontal) plane which is noted to be parallel to the ground, apart thesuperior (top) from the inferior (bottom) part of the human body. The coronal (frontal) plane,with perpendicular anatomy towards the ground, separates the anterior (front) from the posterior(back).The sagittal (median) plane is noted to be perpendicular to the transverse and coronal plane, andit separates the left part of the body from the right part. The medial and lateral directions refers tothe direction towards and away from the mid-line of the body respectively (Fig. 1.2b). Thedirection towards the front and the back side of the body are termed as The ‘anterior’ and‘posterior’ directions respectively. The term ‘proximal’ describes the direction which is towardsthe limbs origin, while the part which is away from the origin of the limbs is known as the‘distal’. This clinical definition done is based on their proximity with their respect to the head. The‘superior’ and ‘inferior’ directions point towards the top and the bottom parts of the body,respectively.Fig. 1.2:1.2.2 Hip anatomyThe hip joint forms the primary connection between the bones of the lower and upper limbs ofthe human skeletal system, which is scientifically referred as the acetabulofemoral joint. Thehip-joint is said to support weight of the body and transfer load from upper limb to the lowerlimb. A ball (femoral head) and a hemi-spherical socket (acetabulum) (Fig. 1.3) form the mainparts of this joint.
Total Hip Replacement Assignment_4
Fig. 1.3:The femoral head is located at the top of the thigh bone (femur) and it is made to fit into theacetabulum in the pelvis by means ligaments (hip capsule), a band of tissue. The function ofligaments is also to provide stability to the joint. The movement process is facilitated by a smooth durable cover of articular cartilage (a proteinsubstance) which cushions the ends of the bones between the two bones ‘surfaces (femoral headand acetabulum).The hip joint's remaining surface is covered by a thin, smooth tissue called the synovialmembrane. In a healthy hip, this membrane's function is to generate a small amount of fluid thatlubricates and improves frictional resistance in the hip joint. All of these parts of the hip-jointwork in simultaneously, allowing easy, painless moving of hip.1.2.3 STRUCTURE OF FEMURIt is the longest and stronger bone in the human skeletal system. Body weight issupported by the femurs during many activities like running, jumping, walking, standing etc. Itconsists two part, the primarily part is diaphysis or central shaft and two wider and roundedbulges known as epiphyses (figure.1.4). Each epiphysis attach with diaphysis through conicalregions known as metaphysis. The diaphysis is generally belonged to hard cortical bone with asmall spongy core while the epiphyses and metaphysis contain mostly cancellous or spongy bonewithin a thin shell of cortical bone. A head, a neck, a greater trochanter and lesser trochanter arethe nearest part of the femur the transition area between the head and neck is quite rough due theattachment of muscles and hips joint capsule.(figure.1.4).The head is conducted upward, medial-ward, and a little ahead and it designs 2/3 of asphere and surface of it is smooth and cover with ossein tissue in the fresh condition excludingdepression, clinically known as fovea capitis femoris. The flattened pyramidal part of the bone isneck which connecting the head with femoral shaft and assemble with the recent wide corneropening medial ward. The angle of affection of neck to the pole in the front of plane is known asneck-shaft angle. The neck jutting a little ahead due to change in femur body by projectingupward and middle side. The angle of inclination of the neck shaft in cross plan is also known asthe angle of interversion. Femur bone of neck has an irregular cross-section and spheroid at theupper end and approximately ovoid with major and minor axes in the ratio about 1.6 at the lowerend which is close to femoral shaft. The body of femur is long, slender and almost cylindrical in form. It is little arched, to beconvex in front, and concave behind, where it is strengthened by a prominent longitudinal ridge.
Total Hip Replacement Assignment_5
Proximal the lateral ridge of the linear aspera becomes the gluteal tuberosity while the medialridge continues as the pectineal line. The shaft has two other bordes one is lateral and other ismedial border. Due to the vast musculature of the thigh the shaft can not be palpated.The femoral neck suffering regressive changes because of declining. The upper part of neck-shaft provides attachment sites for number of muscles and build most palpable part of the femursituated at the junction which torchanter is large, irregular, quadrilateral eminence. It dirtectedthe mini part which is about 10 mm lower than the head in adult. The minor trochanter is aconical eminence on the medial side of the femur (Fig.1.4)2.2.1 Human gait cycleIt is the way of motion which is achieved by power of body, while maintaining harmonywith the help of human limbs. Nature of gait follows common pattern when it varies fromindividual to individual. It is bipedal and biphasic. The two phases of gait cycle which are thestance phase and swing phase and this both are distinct and interconnected phase and this phasescan further subdivide into 8 different phases as described in terms of percentage of each gaitcycle. 60% of normal walking cycle in stance phase in this the foot remains in contact with theground that means it begins from heels and touch the start of foot.The right foot comes in flat contact with the ground before the heels rises. Lifting the toeoff the ground marks to the end in the stance phase. The remaining 40% is known as swing phasein this foot moves in the air during the right swing phase and the left legs solely supports thebody. This phase ends with the heel contact and the cycle repeats itself and vice versa. Theduration between feet and ground up to remain in contact is known as double support. A typicalcycle is presented in fig.1.5.3rd combined musculoskeletal and finite element modelling.2.REVIEW OF THE HIP JOINT2.1. AnatomyThe joint of hips made with the ilium, ischium, and pubis bones and the femur which is aball and socket comprising Figure 1. The femoral head act as a ball within the socket of theestablishes and formed at the joint between the three pelvis bones. This allows the to all threerational degrees of freedom ans restricted only by the capsular ligaments and the depth of the cupFigure 1.
Total Hip Replacement Assignment_6
The joint of the hips rotate in all three axes but does not allow translation between thefemur and pelvis. Fort the purpose of this study the y-axis lies parallel to the length of the femurshaft with the z-axis lies at 90 degree from femoral head to the greater trochanter and the axis isthe product of the two other axe. 2.2 OsteologyThe long bones have the unlike properties and the young modulus have an imaginary lineof 17.4GPa approximately, while at an angle of 90° the imaginary line is about 11.7GPaapproximately. The structure of the bone is divided into two types Cortical and the Cancellouswhich are not homogeneous. The majority of central part of the long bone is made by compactbone or by the cortical bone and the outer shell is at the end part of the bone. The lower densityspongy bone i.e. the Cancellous bone makes the major end part of the bone i.e. epiphyses. Thespongy structure of Cancellous bone is made up of bar forming a framework of the bones whichis known as the trabeculae. These trabeculars are in very close contact to the bones and theinternal blood supply.2.2.1. Bone propertiesCortical bone which is also known as Compact bone or Lamellar bone. The extremelyhard exterior is formed by the cortical bone which has a density of 1700-2100 kg/m-3approximately. Cancellous bone which also known as spongy or trabecular bone is full of tinyholes and has two types of bone tissues with highly changeable nature, its density can fall up to50 kg/m-3 and are found in human body. Through some studies it has been noted that it isdifficult to differentiate between both Cortical bone with a low density and Cancellous bone witha high density, the density of the Cancellous bones have the similar type of tiny holes as inCortical bones which other studies disagrees. With the growing age the density and strength ofthe bone increases till the maturity of the bone which is till the age of 35 years and then startsdeclining. The bones have the adaptive properties and can change them according to its densityand maturity. The general relationship of density of the bone and modulus density , i.e. thedensity of the bone (p, g/cm-3) is proportional to its modulus (E, GPa) is described in theequation 1.Equation 1The cubic relationship between the modules and the density was found by Carter and Hayes in
Total Hip Replacement Assignment_7
(1977). Rice et a. (Rice et al. 1988) a slightly better correlation was found with a squaredrelationship and also it was found in other studies the power, p, is slightly less than 2(Hodgskinson and Currey 1992 ; Morgan et al. 2003). According to the equation 2 it was alsofound by Carter and Hayes that the modulus – density was marked for a effect by the strain rate.Equation 2While it should be noted that this is one of the many relationships to found be between modulusand density. A large degree of variation between studies was found between variation and studieswhen a review of the potential relationship of modulus and density of bone was conducted byHelgason et al. 2008)The dependency of the bone density has been shown to depend on the tensile strength and yieldstrength of the bone (Figure 4) (carter and Hayes 1977; Kopperdahl and keaveny 1998; cowin2001). The bone strength is considered to be dependent on its density, whereas the yield strain isnoted to be independent of elastic modulus, yield stress and density (Cowin 2001; Morgan andkeaveny 2001), however a variation has been reported in the vaiues of yield strain. Acrossseverai anatomicai sites it researches conducted by kopperdahl et al. (1998) the yieldcompression for cancellous bone was found to be 8400pe (± 1000 s.d.) and between 7000pe(±500 s.d.) and 8500pe (±1000 s.d.) by Morgan rt al. (2001). kopperdahl et al. found the yieldstrain of cancellous bone to be 7800pe and for Morgan et al. it varied between 6100pe (±500 s.d.)and 7000pe (±500 s.d.) in tension. In Ebacher et al. (2007) research it was found that cancellousbone is more ductile than cortical bone with an Ultimate strain of approx 10000-15000pe. Thecortical bone was found to be having a yield strain of approx 4000pe in tension and yield strainwas higher and more variable in compression than in tension, between 6500pe and 10000pe.Figure 4Strain gauges were attached to human tibia by Lanyon et a. (1975) to measure the surface strainduring normal walking. A variation was noted in the surface strain through gait cycle from 640pe(±70) to 2370pe (±180) in tension and it peaked in the strain when the foot left the floor. Thecompressive strain measured a hike as the load carried by the subject was increased and strainhiked to highest when the subject was seen running on a treadmill 8470pe (±590). the bone on
Total Hip Replacement Assignment_8

End of preview

Want to access all the pages? Upload your documents or become a member.

Related Documents
Total Hip Replacement: Case Study Assessment
|11
|2866
|68

Combined Musculoskeletal and Finite Element Modelling of the Proximal Femur
|21
|9803
|188

Nursing Care During Total Hip Replacement
|8
|2384
|44