ENGINEERING MATERIALS IN MEDICINE ME6505 GROUP PROJECT Prof.

Added on - 03 Oct 2020

  • 12

    Pages

  • 5676

    Words

  • 18

    Views

  • 0

    Downloads

Trusted by +2 million users,
1000+ happy students everyday
Showing pages 1 to 4 of 12 pages
ENGINEERING MATERIALS IN MEDICINEME6505GROUP PROJECTProf. Seeram RamakrishnaAssoc Prof. Thian Eng SanTEAM 8: KNEE IMPLANTSubmitted by,Dai ZhenweiKalaiselvan VimareesanMullapudi Sneha SreePan BoRajagopalan EswaranRamasamy VigneshRaveendra RamgopalShi ZhiruiSuhail Mohammed HussainWang Haiming
1CONTENTS1. Introduction ........................................................................................................................................................21.1. Key functions of the Knee ...........................................................................................................................21.2. Need for Knee replacement ...........................................................................................................................22. Knee Replacement Prosthesis....................................................................................................................................... 32.1. Knee Implant Designs............................................................................................................................................... 32.2. Implant Fixation .............................................................................................................................................33. Bio-materials................................................................................................................................................................... 43.1. Requirements for Bio Material............................................................................................................................... 43.2. Selection of Material .....................................................................................................................................54. 3D printing of Knee implant ..............................................................................................................................74.1. Printing of Tibial Insert / Spacer and Patellar Component ..........................................................................74.2. Printing of Femoral and Tibial Component ..................................................................................................85. Issues ....................................................................................................................................................................95.1. Biocompatibility of Nitinol ..........................................................................................................................95.2. Issues in 3D printing NiTi using SLM ..........................................................................................................96.Medical Applications of Nitinol .......................................................................................................................107. Market Survey for 3D printed knee implants ...................................................................................................108. Conclusion ........................................................................................................................................................119. References .........................................................................................................................................................11
21. IntroductionThe knee joint is one of the most critical, largest and strongest joint in the human body. It helps in joining thelower leg with the thigh and enables the former to move relative to the latter while supporting the body’s weightat the same time. There are three bones which constitute a knee joint which are the femur, the patella, and thetibia. The patella is otherwise called as knee cap. The femur and the tibia are also referred to as thigh bone andthe main bone of the lower leg respectively. The meniscus, which is a layer of tough, rubbery fibrocartilagebetween tibia and femur, functions as a shock absorbing element for preventing collision between the leg bonesduring jumping, running and other activities. The joint capsule contains the synovial membrane which producesthe synovial fluid to lubricate the knee. [1]1.1.Key functions of the KneeThe knee is a joint comprising of complex movements in various directions with the help of multiple bones. Themovements include bending (flexion), straightening (extension), gliding of femur on top of the tibia in forwardand backward directions (translation) and also inward rotation of femur (internal rotation) or in outwarddirection (external rotation) with respect to the tibia.Range of motion (ROM) measurements helps to evaluatethe functioning of a joint and is measured with functional and passive measurements whichdiffer dependingupon gender and age.The ROM values for a normal knee are, flexion from 0 to 160oand extension up to 0oandin some cases up to -10owhich condition is referred to as hyperextension. The maximum patellar compressionforce generally is 7 fold of one’s body weight and the maximum compressive load on the tibial and femoralcomponent would be 5.6 times body weight (values taken during squatting activity). [6] [7]Figure 1. Knee joint and its parts1.2.Need for Knee replacementKnee replacement, otherwise termed as knee arthroplasty, is a surgery performed to relieve disability and painby replacing the weight bearing surfaces of the knee joint (Figure 2).Osteoarthritisis one of the most commonknee diseases which is caused by rubbing of the bones against one another resulting in severe knee pain. Kneedeformity, severe knee pain or stiffness, swelling and chronic knee inflammation do not become better withbasic treatments like lubricating injections, medications and physical therapies and thus requiring total kneereplacement. [2]Figure 2. Osteoarthritis causing bone spursFigure 3. Total knee replacement implant
32.Knee Replacement ProsthesisThe total knee replacement prosthesis or knee implant consists of three main components. They are the femoralcomponent, the tibial component and the spacing made of plastic (usually polyethylene) between the twocomponents, as shown in Figure 3. The femoral component is attached to the lower end of the femur and isgrooved to allow for smooth movement of knee cap against the bone. The tibial component, attached to the tibiaon its upper end, is basically a flat metal platform with a plastioc spacer as a cushion on the top and a stem atthe bottom that fits into the centre of the tibial bone. [3]2.1.Knee Implant DesignsThere are several knee implant designs in the market. But the most common knee implant designs are [4][5]:1.Posterior-Stabilized DesignsThis design is the most commonly used, which involves the removal of posterior cruciate ligaments andreplacing it with the parts of implant. The tibial component has a raised surface with an internal post that fitsinto the cam of the femoral component (Fig. 4a). This is usually prescribed for patients with knee capremoved previously, severe flexion contracture and severe deformity.2.Cruciate-Retaining DesignsThis design retains the posterior cruciate ligament and it involve the removal of anterior cruciate ligament(Fig. 4b). This type of implant design is prescribed for those patients with healthy posterior cruciateligament.3.Bicruciate-Retaining DesignsThe bicruciate-retaining design implant is a new implant design under study which involves the retaining ofboth the posterior and anterior cruciate ligament of the knee which is aimed to make the knee function like anormal and a non-replaced knee(Fig. 4c).4.Unicompartmental ImplantThe unicompartmental implant is used for partial knee replacement. This type of implant is used only whenone side of the knee joint is damaged and when that part alone has to be resurfaced (Fig. 4d).(a)(b)(c)(d)Figure 4. (a) Posterior-Stabilized Design, (b)Cruciate-Retaining Design, (c)Bicruciate-Retaining Design,(d)Unicompartmental Implant2.2.Implant FixationThere are basically three types of fixation to help in fixing knee implants to the bone [4]:Cemented Fixation-This type of fixation involves fixing the metal components to the respective bonesby means of fast-curing bone cement like polymethylmethacrylate.CementlessFixation-Thismethodinvolvestheusageofinterferencefitsorpressfitsorevenaugmenting with screws. Cementless implants are usually made of materials that initiate growing of newbones into the surface of implant to facilitate fixation.Hybrid Fixation-This is a combination of both cemented and cementless type of fixation. It involves thefemoral component inserted into the thigh bone without the use of cement whereas the patellar and thetibial components rely on cement for connecting them to their respective bones.
desklib-logo
You’re reading a preview
Preview Documents

To View Complete Document

Click the button to download
Subscribe to our plans

Download This Document