As seen in the previous section, hip joint replacement has become a highly popular and successful surgery. Orthopaedic surgeons have appropriately looked at other joints for similar replacement strategies (Chapman 1993). In some cases, a design philosophy similar to the total hip replacement is used. In others, somewhat different approaches are required. A popular generalization about joint replacement surgeries is that the difficulty of the surgery increases as one moves radially away from the hip joint. Closest to the hip, the knee has been the joint which has benefited most from the technology of the THR surgery. Knee replacement surgery is now widely practiced in the United States. Most prostheses are similar to THR’s in materials selection, with a femoral component made of either cobalt-chrome or titanium alloys and a high-density polyethylene (HOPE) for the wear surface connected to the tibia bone. The tibial HDPE component often has a metal backing. A unique
feature of the knee prosthesis is the need for a patella (knee cap), which is also made of HDPE but without a metal backing. A high frequency of patella failures was observed when a metallic component was included. Because of the different geometry of the knee replacement in comparison to the THR, there is not particular advantage of cobalt-chrome versus titanium alloy for the femoral component. The trade-off between the use of PMMA cement versus cement less fixation is similar to that for the THR, although the knee prosthesis is less forgiving to loosening due to the prosthesis being on the ends of the femur and tibia bones rather than inserted down a long femoral shaft. Once surgeons mastered the art of prosthesis alignment, cement fixation proved to be essentially as successful as cement less. One can assume that hydroxyapatite coatings for prosthesis fixation will have substantial promise in knee replacement surgery as it has in THR’s, although HA applications in hip surgery are much more widely used at this point in time. The total shoulder replacement also involves a design similar to the THR, with a metal alloy “head” attached to a stem which is implanted into the humeurs bone. The metal head mates to a HDPE “glenoid” which is sometimes metal backed.
Elbow reconstruction surgery involves a significantly different design.
Rather than a metal/polymer sliding joint, the elbow prosthesis is a coupled axle design joining the humerus an
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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