Key Bold terms to know Italics concepts to know Color will very likely be on the exam Outline for Quiz 1 Section 1 Biomechanics Background The study of structure and function of biological systems by methods of mechanics Concerns internal and external forces acting on the body o And the effects of these forces Wide reaching field o Solid and fluid mechanics o Motion sports mechanics o Automobile crash tests o Tissue engineering and biomaterials artificial organs and joints Orientation of the body o Proximal upward near head Superior o Distal downward near feet Inferior o Medial inward towards body o Lateral outward away from body o Anterior forward towards nose o Posterior backward towards buttocks Total Knee Replacement Anatomy of the knee o Three major components Femur superior portion Tibia inferior portion Patella knee cap o Three major joints Your quadriceps and tibia are connected by the patella tendon Patello femoral joint Tibio femoral joint Tibio fibula joint NO ARTICULATION Other two are more important o Meniscus tissue Deepens the socket of the tibia and cushions o Cartilage on cartilage articulation Less friction than bone on bone Lubricated with synovial fluid very slippery o Stabilizers Static ligaments muscle that connects bone to bone Primary restraint medial lateral anterior posterior o ACL cross shaped X Primary restraint to anterior subluxation Tears when you plant your foot and turn too quickly common in basketball and soccer Secondary rotary rotation There are 6 degrees of freedom in the knee x y z 3 lateral 3 rotational Conditions that lead to total knee replacement o Osteoarthritis Types Commonality Primary idiopathic Secondary post traumatic arthritis More common than hip osteoarthritis Affects 80 of people older than 75 Same risk in males and females until menopause then more common in females Risk factors Increasing age Gender female Obesity Trauma Infection Repetitive occupational trauma Symptoms Pain Loss of function Stiffness Swelling Deformity Crepitus Treatments Non operative o Non pharmacological Educational methods Weight loss Assistive devices Physical therapy Occupational therapy o Pharmacological NSAIDS Glucosamine sulphate Intra articular Corticoteroids cortisone shots Intra articular Hyluronic acid Operative o Arthroscopy arthroscopic debridement Shave off cartilage o Osteotomy 90 degree unrestricted knee flexion o Knee replacement surgery Partial knee replacement Total knee replacement o Rheumatoid arthritis Genetic Autoimmune Dissolves cartilage Similar symptoms as above because cartilage wear is similar to dissolving cartilage o Joint Capsule Rupture Stability is lost Arthritis is developed if untreated This is due to a change in load bearing Cartilage is wearing away Can lead to a joint replacement Even laproscopic minimally invasive procedures need to go through the joint capsule Indications for surgery o Cartilage breaks down bones start to rub against each other painful o Body spurs from around the joint and ligaments start to weaken History of knee replacements o Partial vs total o History of total Materials tried partial only replace one condyle the other is still intact total replaces both condyles Full tibial and femoral components Ivory started the idea of biocompatibility nylon pig muscle pig fat Ivory joint hinged with metal or plaster Metal on plastic o Materials used today Stainless steel Cobalt chromium alloys Metallosis and failure concerns Titanium Tantalum Titanium Tantalum into the trabecular bone porous spongey bone bone can better integrate into the device Zirconium UHMWPE plastic Ceramic Cemented Not common Expensive not strong enough Uses bone cement Not preferred For people with low bone density Cementless No bone cement preferred because if replacement surgery is needed cement removes extra bone which is undesirable Allows for bone integration Hybrid femoral has no cement tibial uses cement Winner of material combination metal on plastic The medial condyle is larger than the lateral Classifications o Unconstrained many types PS Middle stem in tibial component separating the two condyles most popular Cruciate retaining No middle stem stem is for posterior function of the ligament Mobile bearing prosthesis allows for motion non rigid load sharing failure likely motion of device allows for loosening 1 degree of freedom compensates for lack of dynamic restraint o Constrained o Unicondylar only replaces one of the two condyles Criteria o Biocompatible o Structurally and functionally similar Still has a range of motion and is similarly shaped Not a lot of friction o Long lasting Appropriate strength maintains shape The less surgeries the better Surgical o Goals Restore mechanical alignment Preserve the joint line Balance ligaments must be relaxed for surgery varus valgus Normal Q angle Quadriceps angle should be under 20 degrees o Otherwise risk of sports injuries specifically ACL tears Angle between the neck of the femur goes into hip and other side of the femur o Surgical Procedure Requires sawing of the femur and insertion of the new condyles via drilled holes and peg inserts Tibia also requires drilling down to create scaffold for the bottom component o Robotic More precise incisions Makes for a better positioned implant Reduce risk of future complications Hip Arthroplasty Hip Joint o Components Femoral head ball Can be cemented or uncemented Acetabulum socket Has a deep socket so that it doesn t dislocate Shell and liner o Shell metal bone anchor o Liner PE for low friction Can have replacement surgery to only replace the liner Stem Allows for height adjustment o Rotation 3 degrees o Types 3 1 Resurfacing Just replaces the ball and socket 2 Mini hip Has a small stem 3 Total hip Larger stem Implant o Surgery non ligament sparing because the socket is replaced o Surgery techniques Posterior Lateral Antero lateral Posterior direction of surgery Need to go through more muscle invasive Common Could cause dislocation abductor muscles minimally invasive Anterior Can cause numbness due to fermoral nerve 10 chance Minimally invasive via computer navigation o Risks dislocation most common usually occurs between 8 12 weeks osteolysis loosening causes infection inflammation body reacting to wear debris o fixed by using ceramic instead metal sensitivity more common in women starts with metal wear triggers an immune reaction can kill tissue metal toxicity metallosis harmful levels of metal ions in the blood stream can lead to