Chronic arthritis, injuries or severe infections can lead to painful stiff knees that can prevent daily functional movements and activities. Rheumatoid arthritis (RA) commonly affects mobility by affecting the knee joints. When all other medications and therapies fail that patient may consider a Total Knee Replacement or TKR.
The knees are the joints that bear the weight of the body. The knee joint is essentially made up of the thigh bone or femur that sits on the upper part of the shin bone or tibia. There is the knee cap or patella over the joint to assist in movement and provide stability to the joint. The joint space has cartilages to cushion and assist the smooth movement of the knee.
When is total knee replacement performed?
Some of the commonest indications for total knee replacement include pain, limitation of functions or movement, stiffness of the joint, advancing age and radiographic evidence.
Benefits of this operation are remarkable in terms of pain relief, improved range of movement of the knees, improved sleep and better quality of living.
In certain conditions this surgery may not be performed. This includes medical diseases and poor health that makes withstanding the surgery difficult, psychiatric disease, dementia, or systemic infections. Other relative causes of delaying and deliberating over TKR include obesity, skin ulcers, nerve damage around the knees etc.
A radiographic image is necessary to detect the extent of joint damage before undertaking the surgery. Usually TKR is done under general anesthesia where the patient is unconscious and the muscles are relaxed to facilitate surgical intervention.
The operation can also be performed under spinal or epidural anesthesia where the anesthetic medicine is injected into a space between the vertebrae in order to numb the legs during the operation without making one lose consciousness.
Intravenous fluids and antibiotics will be given before surgery and a catheter will be placed in the bladder to drain the urine.
A cuff like tourniquet is placed on the thighs just before the incision. This is then inflated. The tourniquet reduces the blood flow to the operative site and reduces the risk of bleeding.
If patient is at risk of developing blood clots or thromboembolism, then the tourniquet may not be applied.
Types of surgery
TKR can be performed with two major approaches:-
Traditional open surgery
In classical TKR an eight to twelve inch incision is made in the front or side of the knee. The muscles are cut open and the joint cavity is exposed. The damaged parts of the joint including the lower part of the femur, upper part of the tibia are removed by sawing them off.
The prosthesis or the artificial joint is a metallic or plastic replica of the lower part of the thigh bone and upper part of the tibia. These may be locked in over the stumps or may be cemented to the stumps. Prosthetic cartilage is placed between the prosthetic ends of the femur and tibia.
Minimally Invasive Surgery (MIS)
In this type of surgery a smaller incision of three to five inches is made. Here the surgeon works the implant through a smaller opening. This leads to less pain and more rapid recovery.
After surgery the tourniquet is removed or deflated before the incision is closed in order to check for any bleeding points. A tube like drain is left in the operative site to drain off the excess fluids.
The surrounding muscles and ligaments are sewn back together and these provide stability to the joint and assist it in movement. The skin incision is closed.
The knee is cast in a splint to aid recovery. The pulses of the feet are checked before removing the patient from the operative table to assess that the blood flow to the feet is intact after the cast.
Post operative recovery and complications
The patient is removed to the Highly Dependency ward from the operation theatre and given intravenous fluids, antibiotics and pain relieving medications.
After 24 hours patient will be transferred to the hospital bed from which they will be discharged in a week or two.
Early mobilization and movement is encouraged. This is done under the guidance of a physiotherapist. Patient may be allowed knee exercises under supervision or the use of Continuous Passive Motion (CPM) machine.
There are two major advantages of early mobilization. One is rapid return to functions and the second is prevention of formations of blood clots that can lead to life threatening condition of thromboembolism where this clots can move up to the lungs or block the blood flow to the heart or brain. Blood thinning medications are also prescribed if they are prone to develop blood clots and these may be continued even after the discharge.
The complications of TKR include infection, pain, blood clots, nerve damage and fractures of the bones during or after the operation.
Reviewed by April Cashin-Garbutt, BA Hons (Cantab)