A total prosthesis is an artificial implant that is used to replace the articular surfaces of the knee when these have suffered a deterioration that produces pain and limitation of mobility that cannot be solved by medical treatment.
Generally it is produced by a degenerative process related to age, although it can also be due to trauma, rheumatic processes and certain diseases (vascular necrosis). They are composed of metal components for the articular surfaces of the femur and tibia and plastic components (polyethylene) for the patella and to promote movement between the femur and tibia. There are different types of prosthesis: cemented or not, with preservation of the posterior cruciate ligament, constrained, etc.
Treatment by surgery
The surgical intervention is intended to improve pain and limited mobility and thus increase the quality of life of the affected person. The surgery is usually performed under spinal anesthesia. Passive movements are started within the first 24 hours and assisted ambulation is resumed when the patient’s general condition permits, between 48 and 72 hours. Hospital admission usually lasts 3 to 5 days.
The main complications of total knee replacement surgery, independently of those inherent to any surgical intervention, are joint infection, instability and aseptic loosening.
Success and control
The total knee prosthesis achieves more than 90% success rate. Most patients have no pain or only some discomfort related to temperature or pressure changes. The remaining 10% continue with pain or present new discomfort such as stiffness or inflammation.
The main causes of revision before 2 years after prosthesis implantation are infection, instability and malposition of the components. The main causes of late revision, after 2 years, are polyethylene wear, loosening and instability. Correct identification of the factors that can lead to prosthesis failure and require prosthesis replacement are essential for its success. For this we rely on the anamnesis, a good physical examination and complementary tests, both imaging and laboratory.
In most cases, it is possible to identify the problem causing pain and malfunction of the prosthesis. When this is not possible, a meticulous discussion with the patient is essential to assess the risk/benefit of surgery.