Tuesday 11 12 Bossone Office Hours Knee Implants Biomechanics how we exert forces the moments that we exert from the body and on the body sport motions understand and optimize motion to output artificial organs joints automotive crashes solid to fluid mechanics tissue engineering knee joint femur tibia patella 3 main bones fibula not a load baring bone transfers load from the ankle upward 2 main joints tibio tibia and femur patello patella and femur skin muscle joint capsule hematic seal that holds synovial fluid that lubricates joint area all bones are covered by articular cartlidge 3 5 mm the bone just under the cartilage is called subcondial bone distal further away from head proximal towards your head closer to head medial towards the midline lateral outside of the body Knee Stabilizers static stabilizes knee when your not moving ligament dynamic activietly stabilizing knee muscles fibular collateral ligament lateral collateral ligament tibular collateral ligament medial collateral ligament ACL ligament that restrains anterior drop rupturing an acl you have an unconstrained motion in the knee also has rotary stabilization needs to have surgery if completely ruptured knee has six degrees of freedom ability of a body to move about a given axis any object can have max 6 degrees of freedom 3 axis lateral and rotational movement on each axis more mobility lose stability limited mobility more stability rotation extension abductions adduction flexion Common Conditions that lead to TKR Osteoarthritis o Primary idiopathic wearing of cartilage over time o Secondary post traumatic arthritis Rheumatoid Arthritis o Immune disorder body attacks itself autoimmune disease Indications for surgery Bones begin to rub against each other due to cartridge degeneration bone spurs exposed bone form around the joint ligaments start to weaken pain causes people to alter weight limp to compensate for the change in structure pain this alters the ligaments muscles strengths and function around the joint overall weakens the joint More common than hip OA 80 are above the age of 75 55 more likely in women before its equal chances More likely with Increased age obesity gender female trauma infections repetitive occupational trauma Stages of OA 1 pain 2 loss of function usually when implant occurs 3 stiffness 4 swelling 5 deformity bow legged ness sometimes genuvadus 6 crepitus creaky noises from knee when moved before an implant some solutions are 1st try non pharmacologic solutions weight loss physical therapy knee braces pharmacologic therapy glucosamine sulphate NSAIDS proteoglycan absorbs water and cushions steroids FDA limits its to four year limits proteoglycan production Arthroscopy Minimally invasive surgery go through a port with a tube The cartridge starts looking like a carpet when it starts to wear out The tube removes shaves fuzzy cartilage out and makes it smooth Osteotomy less popular now Altered cartilage caused by pain in knee remove a wedge in the tibia to alter the pressure points on the tibia plateau Knee Replacement Partial and Total depending on current condition of the knee THeophilus Gluck performed the first knee athroplasty Implant designs UNCONSTRAINED o Cruciate retaining sparing posterior anterior ligaments o Cruciate substituting posterior stabilized PS knee most commonly used o Mobile bearing prosthesis tibial tray is supposed to move to allow for another degree of freedom thought more flexibity would allow for more load sharing not always the case o Constrained hinge the medial side of a knee replacement is larger than the lateral side screw home mechanism 20 degrees causes rotational and lateral movement in the joint The geometry prvides stability to a knee when walking on a hinge joint all rotation is occurring on a single axel uniaxilur 6 27 13 Unconstrained TKR design 3 parts tibial tray on surface of tibia section in femur plastic inset that slides into tibial tray Purpose of stem interacts with stop of femur piece Criteria for Materials used in TKR Biocompatible come up with list of materials that satisfy conditions choose the best cement less fixation relies on bone DESIGN PROCESS prevalence of the issue how many people are affected is their a need for a solution design need identify list of clinical needs conditions of problem come up with criteria to meet that need make up designs to meet criteria test designs final product of design cycle BEST MATERIAL DESING groove in center of implant allow for tracking alignment robotic knee surgery has become more popular reduces times minimally invasive more precise CT scans generate personalized replacement designs specific to to each patient R radius of curvature 1 R AC shows how curved something is TKR don t have the same R all the way around Unicentric designs stationary axis of rotation Polycentric moving axis of rotation moves at knee rotates and glides Technical goals of Knee Replacements Preservations of joint line Restoration of mechanical alignments Balance ligaments Maintaining or restoring normal Q angle 1 Coronal Plane 2 Sagittal Plane Tendons connect muscle and bone hip joints epiphysis diaphysis metaphysics Angle of the line of action of force of the quadriceps muscle group hip replacement failures 1 chronic pain 2 unequal leg lengths KNEE JOINT What are two joints in the knee Tibial femular joint Patella femular joint What is the screw home mechanism in the knee joint Rotation between the tibia and the femur in the last 20 degress of rotation It locks in place with the last 20 degrees of motion and allows the knee to move What are the four static stabilizers of the knee ACL PCL medial lateral What is the q angle Angle of line of action of force of the quadriceps and the longitudinal axis of the tibia 3 types of knee arthroplasty 1 constrained unconstrained moving platform unconstrained posterior stabilized knee two bones in the hip joint pelvis and femur what is the pelvis part of the hip joint called Accetabulum socket of the the ball and socket joint Metallic shell into the hip bone Insert of liner which is polyethelene or ceramic Femoral component of the hip implant is femoral stem that goes into femur Femoral head spherical ball that attaches to stem Vary in size depending on patient What materials are used in hip implants 1 metal 2 ceramics 3 chromium 4 cobalt 5 polyethelene Metalossis metal toxic to the body blood poisoning due to metal Most minimally invasive surgery is the anterial lateral surgery for