KNEE REPLACEMENT SURGERY
Joint replacement surgery is removing a damaged joint and putting in a new one. A joint is where two or more bones come together, like the knee, hip, and shoulder. The surgery is usually done by a doctor called an orthopedic surgeon. Sometimes, the surgeon will not remove the whole joint, but will only replace or fix the damaged parts.
The doctor may suggest a joint replacement to improve how you live. Replacing a joint can relieve pain and help you move and feel better. Hips and knees are replaced most often. Other joints that can be replaced include the shoulders, fingers, ankles, and elbows.
Knee replacement surgery may be an effective treatment. Some medical treatments for degenerative joint disease may include, but are not limited to the following:
- Anti-inflammatory medications
- Glucosamine and chondroitin sulfate
- Pain medications
- Limiting painful activities
- Assistive devices for walking (such as a cane)
- Physical therapy
- Cortisone injections into the knee joint
- Viscosupplementation injections (to add lubrication into the joint to make joint movement less painful)
- Weight loss (for obese persons)
Introduction to Knee Replacement Surgery
You need to have a clear idea about how your knee functions, and what might necessitate a knee replacement surgery – before actually opting to have the operation. Some basic concepts regarding knee replacement would be clarified over here:
How does the knee joint work?
The knee joint comprises the femur (the lower portion of the thighbone). The joint operates by rotating on the patella (kneecap), and the upper section of the tibia (shinbone). The articular cartilage ensures that the bone movements remain smooth and properly cushioned. The patella slides on to the lower portion of the articular cartilage.
What is the synovial membrane?
The synovial membrane is the smooth and thin line of tissues, which protects all the adjoining areas near the knee. The membrane also releases a synovial fluid, which acts as a lubricating agent for the knee joint.
When the very first knee replacement surgery was performed?
The first knee replacement operation was successfully carried out in 1968. Since then, the techniques of knee replacement have become a lot more sophisticated. Knee replacement operation is currently regarded as one of the breakthroughs in medical science, in the 20th century.
What factors can necessitate a knee replacement surgery?
Acute arthritis (general osteoarthritis) more common among elderly people or arthritis caused by rheumatism and/or post-accident trauma).
- Unbearable knee pains (generally stemming from arthritis).
- Torn knee ligaments
- Tears in the meniscus
- Problems in knee cartilages
- Significant deformity
- Stiffness in the knee area
- External injuries
N.B: Contrary to what many believe, osteoporosis DOES NOT require a knee replacement surgery.
What are the general effects of a knee deformity?
- Acute pain, even while you are lying on the bed, or sitting on a chair
- Problems in locomotion, particularly while climbing stairs
- Relapse of knee pains, even after taking medications and following physiotherapy sessions
What are the types of knee replacement surgery?
Knee replacement surgery can be of two types, which are:
- Partial knee replacement surgery
- Total knee replacement surgery
What is the objective of a knee replacement surgery?
This operation is performed to insert medically approved plastic/metal joints, in place of your defective knee joints. When done in the proper manner, the surgery helps you to recover your powers of pain-free locomotion, within a relatively short time-span.
When is Total Knee Replacement necessary?
- When your knee pains are not getting reduced by general medications.
- When you require a quick and seamless relief from deep-seated arthritis problems.
- For removal of knee stiffness and deformities.
- When you are intolerant/allergic to antibiotics for reducing knee inflammation.
- When partial knee replacement would not properly rectify your condition (as decided upon by surgeons, physiotherapists, and other qualified medical experts).
WORD OF CAUTION:
Total knee replacement cannot make you fit enough to take part in athletic events, or other such highly strenuous activities. You need to stay away from certain activities, for the rest of your life. We will come to that later.
What does the knee replacement surgery involve?
- Creating an incision along the middle portion of the affected leg(s)
- Analyzing the defective surfaces, to determine which parts of the knee joint have to be replaced
- Insertion of metal/plastic trough on the surface of the tibia
- Insertion of a stable metal shell, near the lower edge of the femur
- Protecting the kneecap with a plastic button (if required)
N.B: A standard knee replacement surgery requires a time of around two hours.
What are the types of knee prosthetics available?
- Prosthetics that are based on the natural ingrowths mechanism of bones
- Prosthetics that utilize medical cement to bind the joint components together
Note: Screws can be used with the first category of knee prosthetics, to keep the shinbone stabilized.
What are the basics of post-operative care after a knee replacement surgery?
- Continuous physical rehabilitation.
- Starting to walk with mobility supports (like canes, frames, and crutches).
- Gradual return to walking without external aids.
N.B: The total recovery process from a knee replacement operation takes a minimum of six weeks.
What are the activities you need to avoid after the surgery?
- High-impact sporting activities.
- Jogging and sprinting.
- Putting heavy pressure on the replaced joints in your knee.
You can, however, easily participate in light sporting activities, like bowling and playing golf. Have thorough knowledge about the knee replacement surgery, and the post-operative care required after the operation. Follow your doctor’s advice – and ensure that the artificial joint(s) last for many years.
Types of Knee Replacements
Many types of designs and materials are currently available. The knee joint is divided into three compartments for the purpose of description the medial [inner), the lateral [outer) and the kneecap compartments. Arthritis can affect one or more compartments of the knee joint. When two or all three compartments are damaged by arthritis, your surgeons will usually recommend a Total Knee Replacement.
There are two categories of Total Knee Replacement (TKR)
Fixed Bearing – the plastic cushion in this form of knee replacement is fixed to the metal tray on the tibial side of the knee joint.
Mobile Bearing – the plastic cushion is not firmly attached but is allowed to rotate on the tibial tray. This is a newer type of design. The wear rate of the plastic component is probably lower compared with fixed bearing design. However not all patients are suitable for a mobile bearing TKR.
Unicompartment – If only one compartment is affected by arthritis, your surgeon may recommend a Partial Knee replacement (Unicompartment knee Replacement). In this form of knee replacement, smaller components for the femur and tibia are used and the operation can be performed through a much smaller incision (Minimal Invasive Technique). Because of the less invasive nature of the operation, the recovery period after the surgery is much shorter and blood loss is significantly lower compared with a total knee replacement operation. Most patients are able to return home one or two days after the surgery.
Another advantage of Unicompartment knee replacement is that the range of the motion tends to be better than that after a total knee replacement. Unicompartment knee replacements are however less durable than total knee replacements.
Types of Implants
Each section has an ODEP rating listed. This is an rating issued by a group of medical professionals. The number refers to the minimum number of years that the implant has been around ( 3 being a low number of years and 10 being the highest) and the letter refers to the quality of published data that supports the implant (a. being the best c. being the worst).
Partial Knee Replacement (Uni Condular)
This type of treatment involves replacing just one side of the knee joint. Both the upper and lower parts of the knee are replaced, but unlike total knee replacement, just the worn out side is replaced. A metal implant is fixed (with or without bone cement) onto one of the upper side and on one side of the lower side of the knee; both of these articulate with a plastic material (polyethylene).
This is a popular type of replacement and has had good clinical results over the past 15 years with around 4,000 being implanted in the UK every year, these replacements usually last around 10 years.
Total Knee Replacement
Surgeons have performed total knee replacement surgery for over 40 years. Generally it is a very successful operation with over 80,000 being done every year, most total knee replacements last around 10-15 years. This surgery involves both sides of the knee joint being replaced, Both areas of bone are replaced with a metal implant and can be cemented or Uncemented. These metal surfaces articulate with a piece of plastic (polyethylene) which can be fixed to the lower metal implant (tibial tray) or move on the surface of the tibial tray, the latter are known as mobile bearing knee replacements. In terms of how well they do in patients – they both perform very well. In knee replacement surgery, it is important to protect the plastic from wearing out as much as possible, as this is the weak area of the replacement. If the plastic wears out then it is likely that it will need to be replaced in the future.
Partial Knee Replacement (Patello Femoral)
This operation involves replacing some of the kneecap and the area which the knee cap moves. The area in which the kneecap (patella) moves is known as the patella groove, it is this area where a normal knee has a layer of cartilage. If this cartilage has worn out it can be painful and can be replaced with a metal surface.
A plastic (polyethylene) disc is put on the back of the kneecap and articulates with the new metal surface. This type of operation has been conducted for over 15 years but in small numbers.
Re-do Knee (Revision Knee)
If you have had previous knee surgery, which needs to be replaced, this is called revision surgery. A revision knee replacement is much the same as a total knee replacement. The surgeon has to remove the old implant and replace it with a new one. Once the old prosthesis is removed, there is often less bone available for fixation of the new replacement. Therefore, additional metalwork is often added to ensure a good fixation of the new implant. This extra metalwork comes in the form of metal augments, wedges, and stems. The augments and wedges are usually fixed to the new implant around the upper and lower sides of the knee to make up for any bone loss. The stems are attached to the implants themselves, if necessary, and fixed within the shaft of the thighbone or shinbone, to ensure good fixation and stability of the prosthesis.
Dr Debasree Gangopadhyay currently working as Consultant Pediatric Cardiologist at Rabindranath Tagore International Institute of Cardiac Sciences, Kolkata. She is a specialist interventional Cardiologist and has expertise in fetal cardiac imaging (fetal echocardiography). She is also involved in teaching and training of doctors in the field of Pediatric Cardiology.
Rabindranath Tagore International Institute of Cardiac Sciences
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