Total knee replacement surgery is usually very successful operation. Very few patients require a revision surgery. There is a misconception that revision of total knee replacement surgery will be required after ten or more years.
Australian Joint Replacement Registry data shows that less than 4% of knee replacements require revision at 10 years.
Causes of Failure of Knee Replacement
The most common site of loosening occurs where the tibial prosthesis is attached to the tibial bone. This may cause:
- Difficulty walking
- Deformity and swelling of the knee
This is the second most common cause of knee replacement failure. Most infections present early after surgery. However they may also occur some months or even years later and in this instance they are usually caused by infections elsewhere in the body.
Washing out the knee joint under anaesthetic is the first approach to managing infection. This may need to be repeated several times. Intravenous antibiotics are also administered. The length of antibiotic treatment will vary but may be continued for some months.
If this approach fails, further surgery is required and will involve a two stage revision.
Some patients develop laxity of the ligaments of the knee post operatively causing a feeling of instability and pain.
The Operative Procedure
The length of the procedure will be determined by the causes of the failure of the original knee replacement. The surgical options include the following:
- Simple exchange of the tibial plastic insert. This straightforward procedure would be indicated where there is excessive wear of the bearing surface but the remaining prosthesis remains well fixed to bone.
- Removal of the femoral and / or tibial component.
- Insertion of a new prosthesis. This will usually involve inserting a larger and longer prosthesis than the original. Sometimes the surgeon will use a prosthesis that is more constrained (more stable) than the primary prosthesis. This will be indicated in cases of knee instability.
- Bone graft. Allograft is occasionally used to make up for the damaged bone. It is procured from a bone bank and consists of bone taken from a bank that stores bone from organ donors. This bone is tested for communicable diseases (in a similar way to the management of blood donation) prior to insertion.
- Where there has been infection in the knee prosthesis it will involve 2 stages:
- The existing prosthesis will be removed along with all infected tissue. An antibiotic loaded cement spacer is inserted.
- Six to eight weeks later the spacer is removed and a new prosthesis inserted.
In most cases the patient will be mobilised out of bed the day following surgery. Due to the complexity of surgery the patient will have protected weight bearing for six weeks post operatively. Many patients will be transferred after four to five days to a rehabilitation hospital (Donvale or Vic Rehabilitation).
These can occur in the postoperative period. Revision knee replacement surgery is a major stress on the body, and if there are pre-existing medical conditions, the following complications may occur:
- Heart attack
- Short Term Confusion