Knee replacement is the treatment of gonarthrosis. If cartilage wear and tear has reached the bone, I cannot benefit for a long time from corrective osteotomy surgery, meniscus transplantation, or infiltrative therapies; in fact, in this case, to gain benefit from pain and recovery of knee function, knee replacement is the only solution.
types of knee replacements
Basically, there are two types of knee implants, both characterized by a femoral and a tibial component, with an insert sandwiched between the two:
1. Partial knee replacement or unicompartmental knee replacement in which only the damaged medial or lateral portion of the knee is reconstructed. Unicompartmental knee replacement is successfully performed if pain and cartilage wear are mainly located at a specific point in the knee.
2. Total knee replacement in which both compartments, medial and lateral, are reconstructed. A total knee replacement should be done in cases where cartilage wear affects both sides of the knee, medial and lateral. When the cartilage is particularly damaged, the patella is also replaced with a polyethylene component.
knee replacement: the materials
The femoral and tibial components of the knee prosthesis are made of metallic material, normally an alloy of chromium and cobalt. The interposed insert, on the other hand, is made of plastic material (high-molecular-weight polyethylene); this insert is intended to allow joint sliding and rolling motion.
If the patient reports allergies to metals such as Nickel, there are prostheses composed of hypoallergenic materials such as titanium orOxinium.
knee replacement models
Knee replacements have different degrees of internal constraint depending on the state of the Patient’s ligaments.
In most patients, the ligaments (especially the collaterals) are continual and prostheses with a low degree of constraint are, therefore, implanted; if, on the other hand, the patient has a highly unstable knee due to concomitant diseases or severe prior trauma, a constrained or semivinxed prosthesis will be used.
new technologies
In recent years, science has increasingly joined the work of surgeons, providing an ever-increasing choice of new technologies to improve clinical outcomes and enable the creation of prostheses tailored to the Patient.
Intraoperative navigation with GPS is increasingly reliable and quicker to use, and today bone cuts can also be performed using a robot.
Alternatively, innovative surgical techniques with calibrated cuts in the bone can be used, performing a knee resurfacing according to the principles of kinematic alignment.
In patients in whom there are synthetic means that prevent the placement of surgical instrumentation, three-dimensional planning with the construction of customized templates can be performed using a preoperative CT scan: this technique is called Patient Specific Instrumentation (P.S.I.).
the post-operative
As early as the first day after surgery, knee mobilization and verticalization with the help of crutches is started.
In the following days, one learns, with the support of a physical therapist, to walk and go up/down stairs with crutches. Loading is allowed immediately, and about 15-20 days after surgery, the patient is encouraged to abandon the first crutch.
Ambulation without crutches is usually achieved at one month after knee replacement surgery.
Discharge from the facility depends on the patient’s general condition: it occurs, generally, 4-5 days after surgery for younger patients; older patients who require more attention due to concomitant diseases remain hospitalized until general parameters stabilize.
rehabilitation
After knee replacement surgery, it is necessary to continue rehabilitation even after discharge from the facility, until the fifth to sixth week (approximately) after surgery.
The patient is advised to continue the exercises learned during the hospital stay to reactivate the muscles and achieve optimal knee flexion-extension.
A patient with no concomitant issues that limit his or her movement and travel, with supportive friends or family members, and living in a barrier-free home can safely return home, managing rehabilitation with a physical therapist or traveling to a nearby center.
For a patient who presents, however, with concomitant walking problems, no family or friends available, and who lives in a house with architectural barriers, it is preferable to continue rehabilitation with admission to a rehabilitation center.
duration of a knee replacement
Survival of hip and knee replacements have been studied for several decades, and the results are entered into national prosthetic registries. The first to introduce these registries, were the Scandinavians in the late 1970s, while, since 1990, a pilot registry project started within theRizzoli Orthopedic Institute.
In 2000, the following was born in Emilia-Romagna. R.I.P.O.(Register of Orthopedic Prosthetic Implantology), which allows the precise monitoring of all hip and knee prostheses implanted in the region.
Each year the registry produces a report in which the success of each type of prosthesis is analyzed, including in relation to patient characteristics (age, gender, diseases).
To date, knee replacements have a survival rate of about 94% at 17 years after implantation.
Surgeons can now use this report to guide their choices, implanting the type of prosthesis that has provided the best results over time.
In addition, the registry (which is based at the Rizzoli Institute’s Medical Technology Laboratory) provides patients with the certainty that they can be readily tracked should extraordinary checks of implanted prostheses become necessary.
Do you want to learn more about knee replacements? Please feel free to CONTACT ME.
