“All you need to know about Knee Replacement Surgery”
— Get Well in India
Total knee replacement surgery, also called as Arthroplasty, is a surgical procedure which involves replacing damaged, worn or diseased joint with a functional and long-lasting artificial joint. The artificial joint is called a Prosthesis.
In the past many years, there have been several improvements in the surgical techniques and implant designs which has helped make Total Knee Replacement surgery as one of the most successful orthopedic procedures all over the world today.
If you are suffering from a chronic knee pain which keeps you from doing your everyday activities or if you are suffering from severe arthritis or any knee injury, Total knee replacement surgery is the recommended treatment. While the idea of getting the knee replaced can be daunting, it is one of the safest and most effective surgical procedures available.
The main aim of the Total Knee Replacement surgery is to resurface the part of the knee joint that is damaged. Damaging of knee joint happens because the cartilage in the knee stops providing the necessary cushion and support.
The largest joint in the body which is the Knee, is also one of the most complex. Joints are the areas where two or more bones meet. Knee is considered to be a complex hinge joint. In a simple language, it is similar to the hinge on the door. It not only helps you move back and forth, it also allows greater movement and flexibility.
The knee is composed of three bones:
- Femur or Thigh bone : It is the largest and the strongest bone of the body. It is the weight bearing bone of the thigh. It connects the hip to the knee.
- Patella or Kneecap : It is a small bone in front of the knee and rides on the knee joint as the knee bends.
- Tibia or Leg bone : It is the second largest bone of the body. It is the weight bearing bone of the leg. It connects the knee to the ankle.
The knee is a major weight-bearing joint that is held together by muscles, ligaments, and other important soft tissues. The ligaments hold the knee together and give it stability. The two ligaments, posterior and anterior cruciate ligaments (PCL and ACL) limit forward motion of the knee bones, keeping them stable.
Cartilage is the material inside the joint that absorbs shock to the knee during weight-bearing activities such as walking or stair climbing and also protects the knee. Two cartilage disks, called menisci, are located at the end of the tibia and act as shock absorbers when we walk or run.
The femorotibial joint is where the femur and tibia come together. The patellofemoral joint is where the patella and femur form a junction. These two joints work together to allow the knee to bend and straighten. If you have a Total Knee Replacement, it is these joints that are replaced.
When one or more parts of the knee are damaged the movement becomes restricted and over time the cartilage, which is the smooth covering at the ends of the bone in the joint, starts to crack or wear away. When this happens the surfaces of the bones rub together. This causes pain, swelling and stiffness which limits your day to day activities. This condition is called osteoarthritis, and it is one of the common reasons to have a knee replacement.
Some other causes of knee joint destruction are:
- Rheumatoid arthritis: This causes inflammation of the tissue around the joint, which in turn causes deterioration of the cartilage. It affects people of all ages but mostly occurs in women over the age of 30.
- Post-Traumatic arthritis: Arthritis may begin after an injury to the joint cartilage. It can develop in individuals of all ages after a serious knee injury. A knee fracture or severe torn ligaments can damage the cartilage over time. This can cause knee pain and limit function.
- Avascular necrosis: This results from an inadequate supply of blood to the end of the bone inside the joint. This can occur for no reason or can occur as a result of some other conditions such as alcohol addiction or prolong intake of steroids. It is basically due to loss of blood supply to the bone. If the bone dies (necrosis), the joint will become arthritic. This pain often comes on quite suddenly and may increase rapidly. It can happen in any age.
- Misalignment of the knee joint: It happens when the bones of the knee joint are not formed in the way that they should, the knee bows in or out, undue pressure is placed on the joint and, over many years, results in breaking down of the joint.
Knee osteoarthritis develops over a period of time and can sneak up on you. By the time you experience the symptoms, the damage may already be done. If you cannot carry out your everyday activities due to pain or discomfort in the knee, then you may have arthritis of some kind. In that case, you will experience difficulty in bending, squatting, kneeling and walking. It is advisable to see an orthopaedic doctor in such a scenario.
Most knee replacement patients are between the ages of 60 and 80 years old but in some cases, younger patients with knee injuries may also require a total knee replacement.
Your orthopaedic surgeon will take x-rays of your knee joint to see how much damage has occurred. There is no blood test to diagnose osteoarthritis. Depending on the extent of your knee problems, your doctor may also suggest treatments before concluding on to knee replacement surgery. Treatments may include medication, injections, or some physiotherapy. If none of these treatments allow you to recover, then knee replacement may be suggested.
Surgical Procedure Details
You will be admitted to the hospital one day prior to the surgery . The surgeon and anaesthetist will come and see you to discuss about the procedure and answer your queries, if any. You will be lying on your back, and tourniquet will be applied to your thigh to reduce blood loss.
Anesthesia will be given and an incision will be made upto eight inches along the affected area to expose the knee. The damaged joint surfaces from Femur and Tibia will be removed. The ends will then be precisely measured and shaped so as to fit the appropriately sized prosthetic replacement. A dummy joint is positioned to test that the joint is working properly. Adjustments are made, the bone ends are cleaned, and the final prosthesis is fitted.
The end of your Femur is replaced by a curved piece of metal, and the end of your Tibia is replaced by a flat metal plate. These are fixed using special bone ‘cement’. A plastic spacer is placed between the pieces of metal. This acts like a cartilage, reducing friction as your joint moves.
The wound is closed with either stitches or clips and a dressing is applied to the wound. In rare cases a splint is used to keep your leg immobile, but you are usually encouraged to move your knee as early as possible. The actual surgical procedure takes about 1 ½ to 2 hours.
Prosthetic implants vary greatly by design, fixation and materials. Metal is used extensively in orthopedic implants in a multitude of different forms. The choice of implants depends on factors such as the status of ligaments and the amount of deformity in the knee. There are a variety of different metal alloys used but a few of the more popular include the following:
- Titanium and its alloys: Titanium and Titanium alloys are corrosion resistant and this makes them inert biomaterial, which means they will not change or chemically react after implanting in the body. Hence, they are safe to use.
Titanium and its alloys have a very lower density compared to other metals used in knee implants. Moreover, the elastic modulus of titanium and titanium alloys is lower than the elastic modulus of the other metals in knee implants and so the implant is more like the natural joint, and so will not create much complications. The most used titanium alloy in knee implants is Ti6Al4V.
- Pure Titanium: Pure titanium is generally used in implants where high strength is not required. It is mostly used in making fiber metal, which helps the bone to grow into the implant and fix it better at the right position.
- Titanium alloy: Titanium alloys are biocompatible in nature, and they contain different amount of vanadium and aluminum.
- Tantalum: Tantalum is a type of pure metal, which has an outstanding biological and physical properties such as flexibility, corrosion resistant and biocompatibility. A new porous substance has been developed of tantalum recently called ‘Trabecular Metal’. It contains dodecahedron pores. The size of the pores makes this material very good for bone in growth.
- Zirconium: It is mostly used in the ceramic knee. It uses a combination of zirconium alloy and a plastic tibial component. It has replaced the cobalt chrome alloy used previously for knee implants. Zirconium has a life expectancy of about 20-25 years. Life expectancy can be considered as the key indicator in knee replacement. The wear and tear of the knee joint happens when the femoral and tibial parts rub against each other. Recently the designs are made in such a way that the wear and tear which arises from rubbing of femoral and tibial parts have considerably reduced. Zirconium has four major properties, one, it is scratch resistant, two, it is wettable, which results in a smoother and easier articulation through plastic, three, it is biocompatible and four, it does not contain nickel as many people are allergic to nickel.
- Oxinium oxidized zirconium: It is a transformed metal alloy that has a ceramic bearing surface. It contains zirconium and niobium alloy that is oxidized to convert the surface of the material into zirconia ceramic. Only the surface of the metal is changed, the rest of the implant component is purely metal which is high in strength. It is twice harder than cobalt chromium alloys, but provides half the friction of those alloys which means better performance and long lasting in nature.
- Cobalt Chromium: They are hard, tough, corrosion resistant and biocompatible metals. Adding various metals like molybdenum increases the strength of this alloy. Titanium and cobalt chrome are the two metals that are widely used in knee implants, however there is no conclusion as to which material is better and more suitable. One major disadvantage of it is when there is a rubbing of metal and plastic wear, some tiny particles are released which can cause harmful reactions in the body, especially to those patients who are allergic to nickel.
You may stay in the hospital for three days following your Knee Arthroplasty. You will be prescribed painkillers to reduce your pain and make you feel as comfortable as possible. Your orthopedic doctor may use several methods to prevent blood clots and swelling.
Walking, knee movements and exercise, as recommended by your surgeon or physiotherapist will play a major role in your recovery. You will probably begin physiotherapy the day after your surgery. You will need to use a walker or crutches while standing and walking. Your physiotherapist will help you learn ways to exercise to strengthen your knee.
You need to notify your doctor if you experience fever, redness, swelling, bleeding, or other drainage from the incision site or increased pain around the incision site or any other side-effect.
The success of your surgery will depend on how well you follow your diet and exercise regime during the first few weeks following your surgery. Majority of people experience a dramatic reduction of knee pain and resume functional activities after Knee Arthroplasty.
- No pain: Your new joint should allow you to be more active. Providing painless standing, sitting, walking. It should allow you to do your everyday activities with ease.
- Long-lasting relief: A replacement may not be permanent, but it is long lasting; mostly last from 15-25 years.
- Restore quality of life: Your ability to move again without pain will enhance your daily life, allowing you to resume activities, and improve your overall quality of life.
- Best Technology available: Best available technology has led to the development of long lasting material used in the surgery which lasts for 15+ years.
Majority of the Total Knee Replacement surgeries are successful, however, every surgical procedure has some risks attached to it and so complications might occur. Some complications might occur due to surgery, other may occur due to body’s reaction to a surgery. There may be other factors governing the complications such as age, general health of…