Once preparations are complete, you will be transferred to the operating room
proper. You will be placed on the operating table and a tourniquet will be placed
around the thigh on the side to be operated upon. The tourniquet is like a large
blood pressure cuff which is inflated just prior to the operation to about 300
mm Hg. The normal 'higher' blood pressure is about 140 mm Hg and hence the tourniquet
stops blood from flowing into the leg. It enables the surgery to be carried
out in a clean bloodless field with all the tissues and structures clearly visible.
The surgeon does not have to concern himself with mopping the blood away during
the operation and can concentrate on the knee replacement proper. The whole
of the leg will then be cleansed with antiseptic and sterile drapes placed around
the knee. Your surgeon will then carry out the surgery with the help of one
or two assistants. The tourniquet is not used in patients with pre-existing
circulation problems.
Incision
A cut about 6-8 inches long is made through the skin on the front of the knee.
Soft tissue
The fat, muscles and deeper tissues are then carefully separated moving them
sideways to expose the bones of the knee. The cruciate
ligaments are removed along with the menisci
and the collateral ligaments are released
to allow correction of any pre-existent knock knee or bow leg deformity.
Bone work
The top of the shin bone (the tibia) is then moved forward from underneath the
thigh (femur) bone. A thin wafer of bone is then removed from the top of the
tibia and then a similar wafer from the lower end, the front and the back of
the femur. Finally a layer of bone is removed from the back of the knee cap.
Trial components are then placed on the cut surfaces and the working of the
knee joint checked by moving it through its range of motion to ensure that all
is satisfactory. The surgeon has to check that the bending and straightening
is satisfactory and that the knee cap is moving correctly in its groove in the
front of the knee. If this is not the case then appropriate remedial action
can be taken at this stage. On the other hand if all is well then exact replicas
of the trial components are implanted using bone
cement .
Finishing
The thigh tourniquet is let down so that the circulation can resume into the
leg. The surgeon stems any significant bleeding and after that is accomplished,
the soft tissue coverings of the knee joint are then stitched layer by layer.
Usually two plastic tubes are placed into the artifical knee joint space and
brought out through the skin and connected to plastic drainage bottles. Bulky
dressings are applied to the wound after which the patient is woken up and transferred
to the bed and taken to the Recovery area. Once awake and over the anaesthetic
safely, the patient is taken to the ward.