Joint replacement is a procedure of orthopedic surgery known also as arthroplasty, in which an arthritic or dysfunctional joint surface is replaced with an orthopedic prosthesis. Joint replacement is considered as a treatment when severe joint pain or dysfunction is not alleviated by less-invasive therapies. Joint replacement surgery is often indicated from various joint diseases, including osteoarthritis and rheumatoid arthritis. Joint replacement has become more common, mostly with knee and hip replacements. About 773,000 Americans had a hip or knee replaced in 2009.
Uses
Shoulder
For shoulder replacement, there are a few major approaches to access the shoulder joint. The first is the deltopectoral approach, which saves the deltoid, but requires the supraspinatus to be cut. The second is the transdeltoid approach, which provides a straight on approach at the glenoid. However, during this approach the deltoid is put at risk for potential damage. Both techniques are used, depending on the surgeon's preferences. The number of shoulder replacements carried out each year is increasing, but research looking into global records suggests that nine out of ten shoulder replacements last for at least a decade.
Hip
Hip replacement can be performed as a total replacement or a hemi (half) replacement. A total hip replacement consists of replacing both the acetabulum and the femoral head while hemiarthroplasty generally only replaces the femoral head. Hip replacement is currently the most common orthopaedic operation, though patient satisfaction short- and long-term varies widely. It is unclear whether the use of assistive equipment would help in post-operative care. Hip replacement surgery can be performed from three main directions, each with advantages and disadvantages The classical approach is the posterior, and requires dissection of the gluteus maximus and other large muscles of the back of the thigh to access the acetabulum. The anterior approach accesses the hip joint from the front, with less large muscle dissection but due to the proximity of the femoral artery, corresponding vein, and main nerve bundle for the leg lying just medial to the acetabulum the surgeon must exercise caution and maintain suitable landmarks. The lateral approach dissects smaller muscles than the posterior approach, but has similar navigation concerns as the anterior approach. Surgeon experience tends to determine the surgeon's preference, meaning that the surgeon will only rarely deviate from what method they were initially trained to use.
Knee
Knee replacement involves exposure of the front of the knee, with detachment of part of the quadriceps muscle (vastus medialis) from the patella. The patella is displaced to one side of the joint, allowing exposure of the distal end of the femur and the proximal end of the tibia. The ends of these bones are then accurately cut to shape using cutting guides oriented to the long axis of the bones. The cartilages and the anterior cruciate ligament are removed; the posterior cruciate ligament may also be removed but the tibial and fibular collateral ligaments are preserved. Metal components are then impacted onto the bone or fixed using polymethylmethacrylate (PMMA) cement. Alternative techniques exist that affix the implant without cement. These cement-less techniques may involve osseointegration, including porous metal prostheses. The operation typically involves substantial postoperative pain, and includes vigorous physical rehabilitation. The recovery period may be six weeks or longer and may involve the use of mobility aids (e.g. walking frames, canes, crutches) to enable the person's return to preoperative mobility.
Ankle
Ankle replacement has become a treatment of choice for people requiring arthroplasty, replacing the conventional use of arthrodesis, i.e. fusion of the bones. The restoration of range of motion is the key feature in favor of ankle replacement with respect to arthrodesis. However, clinical evidence of the superiority of the former has only been demonstrated for particular isolated implant designs.
Finger
Finger joint replacement is a relatively quick procedure of about 30 minutes, but requires several months of subsequent therapy. Post-operative therapy may consist of wearing a hand splint or performing exercises to improve function and pain.
Risks and complications
Medical risks The stress of the operation may result in medical problems of varying incidence and severity.
Heart Attack Stroke Venous Thromboembolism Pneumonia Increased confusion Urinary Tract Infection (UTI)
Intra-operative risks Mal-positioning of the components Shortening; Instability/dislocation; Loss of range of motion; Fracture of the adjacent bone; Nerve damage; Damage to blood vessels.
Immediate risks Infection, either Superficial or Deep Dislocation
Medium-term risks Dislocation Persistent pain; Loss of range of motion; Weakness; Indolent infection.
Long-term risks Loosening of the components: the bond between the bone and the components or the cement may break down or fatigue. As a result, the component moves inside the bone, causing pain. Fragments of wear debris may cause an inflammatory reaction with bone absorption which can cause loosening. This phenomenon is known as osteolysis. Polyethylene synovitis - Wear of the weight-bearing surfaces: polyethylene is thought to wear in weight-bearing joints such as the hip at a rate of 0.3mm per year. This may be a problem in itself since the bearing surfaces are often less than 10 mm thick and may deform as they get thinner. The wear may also cause problems, as inflammation can be caused by increased quantities of polyethylene wear particles in the synovial fluid. There are many controversies. Much of the research effort of the orthopedic-community is directed to studying and improving joint replacement. The main controversies are
the best or most appropriate bearing surface - metal/polyethylene, metal-metal, ceramic-ceramic; cemented vs uncemented fixation of the components; Minimally invasive surgery.
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