The knee is the largest joint in the human body, formed by the femur, tibia, and patella, enabling the flexion and extension of the leg.
Muscles and ligaments work together to provide stability to the joint and facilitate movement.
The joint surfaces of the three bones are covered with cartilage, which cushions the contact between joint surfaces and reduces friction during movement.
Irreversible damage to joint surfaces can be caused by certain diseases such as arthritis, osteonecrosis, rheumatoid arthritis, and post-traumatic arthritis.
Only through Total Knee Replacement can these conditions be definitively resolved.
In the initial stage, arthritis may improve with weight loss and rehabilitation. Cartilage supplements, pain management with ice and anti-inflammatories, and injections of medications into the joint can also be used.
Surgery is advisable when severe arthritis with bone-on-bone contact is evident in X-rays, accompanied by the following symptoms:
- Pain resistant to pain-relieving therapies
- Constant pain even at rest
- Difficulty standing for long periods
- Inability to perform daily activities such as walking or climbing stairs
- No benefit or limited benefit from physiotherapy and conservative treatments.
There are various types of knee prostheses: total covering prosthesis and partial or uni-compartmental prosthesis.
The choice of implant type is personalized based on the patient’s needs, considering the type of arthritis, age, activity level, and bone quality.
During the surgery, a small amount of bone is removed from the tibia, femur, and patella, eliminating damaged structures and creating high-quality bony surfaces for the prosthesis implant.
Most ligaments and tendons are left in place, allowing natural knee movement.
For patients with widespread arthritis or autoimmune diseases, total knee prosthesis is recommended, while patients with arthritis in a specific knee portion may benefit from a uni-compartmental prosthesis.
Identifying a knee prosthetic surgery specialist ensures a good outcome and is the first step in evaluating the need.
Not all patients require surgery, and not all pains can be cured by a prosthesis.
Knee Prosthesis Surgery
The procedure begins with anesthesia administration. The safest method is spinal injection, which can be combined with a sedative if the patient wishes to sleep.
Spinal injection is not painful and has many advantages: it reduces the risk of venous thrombosis, bleeding, and improves post-operative pain control.
The damaged parts are replaced with prosthetic components, and the surgery concludes with suturing the incision and applying a dressing.
The duration is about 1 hour, but from the time the patient enters the operating room to leaving the ward, approximately 2-3 hours pass. The duration of the waking phase varies.
The patient returns from the operating room without a bladder catheter and surgical drainage.
The Total Knee Replacement
In total knee prosthesis, the diseased bone and cartilage are removed and replaced with prosthetic components.
The total knee prosthesis consists of 4 components:
- The femoral shield is made of metal, coated with alloys that reduce friction and wear during movement. Once positioned, it wraps around the joint part of the femur.
- The tibial component is made of titanium and usually has a small stem that enters a few centimeters into the tibia bone for increased stability.
- An insert in polyethylene is placed on the tibial component, a material of high resistance that generates minimal friction during prosthesis movement.
- The patellar component is a polyethylene button applied to the patella when this bone is damaged by arthritis or in cases of rheumatologic joint diseases.
Each knee prosthesis procedure is tailored to the patient’s needs, and there may be variations case by case.
The general steps of the procedure include:
- Administration of anesthesia and, in agreement with the patient, sedation
- Surgical incision in front of the knee to access the joint
- Removal of damaged cartilage and bone to prepare the bone ends for implantation
- Ensuring that the prosthetic components are correctly positioned on the bone
- Testing the new joint
- Closure of the incision.
What is Uni-compartmental Knee Prosthesis?
Uni-compartmental knee prosthesis is the smallest implantable knee prosthesis: a device that respects anatomy and allows for quick healing.
There are diseases that exclusively affect a part of the joint, for which a partial prosthesis can be used, smaller and allowing for the preservation of all healthy portions of the knee.
The lower surgical trauma allows for rapid recovery. The patient walks with full weight on the operated limb just a few hours after the procedure, and the hospitalization duration is typically only about 3 days.
Partial prostheses have significant advantages, such as a smaller surgical incision, shorter procedure duration, less bleeding, less pain and swelling, and better joint stability.
Materials Used in Total Knee Prosthesis
In recent years, designs and the number of available sizes allow for true customization of the prosthesis.
The most commonly used metal is titanium, coated with a chrome-cobalt alloy that shows excellent durability over time. It contains nickel, to which certain patients may be allergic, but prostheses without nickel are also available.
Cross-linked polyethylene, the latest generation, is highly resistant to wear.
Typically, the knee prosthesis is fixed to the bone with cement: it ensures immediate and solid anchoring and has a very long lifespan.
In young patients with good bone quality, non-cemented prostheses can be used, composed of a material that integrates with the bone.
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