What is revision total knee replacement?
A knee replacement will eventually fail. The majority (90-95%) of knee replacements will last between 15 to 20 years.
Knee replacements can fail for a number of reasons, the most common being, infection, aseptic loosening and instability. Fractures around the knee replacement are also becoming more common.
Revision knee surgery involves the removal of the failed implant and replacement by a new knee replacement.
The revision procedure is more complex than a total knee replacement. This is because the bone is not as strong when an implant is removed, and the ligaments supporting the knee may be damaged.
In performing a revision, a special implants such as components with a stem and metal “augments” are used to address these difficulties.
Most of the time all components are revised at the same time.
Special techniques may be required to gain access to the knee joint such an osteotomy of the tibial tuberosity. Although this is sometimes necessary it may slow down the rehabilitation of the patient following surgery.
The x-rays above of this patient showed “lucent lines” between the component and the bone, which is suggestive of loosening of the component. During a revision procedure the old components are removed and replaced by a system using stems and augments to accurately reconstruct the knee.
In certain situations bone graft will be used especially if the quality and quantity of bone remaining after removal of the implant has been reduced.
Like revision hip surgery this can be complicated surgery and the complication rate is higher than when performing a total knee replacement.
The hospital stay is often also longer for patients having a revision total knee replacement.
The recovery may be slower and the overall function obtained will be less than that of a primary total knee replacement.
Overall, the great majority of patients who have a revision total knee replacement are very happy with overall outcome.
What happens if my knee replacement gets infected?
Fortunately infection of a total knee replacement is quite rare. The infection rate for primary total knee replacement is less than 2%. Infection of a knee prosthesis is a serious issue. Very occasionally the infection can be treated with wound debridement (removal of non-viable tissue around the knee joint) and antibiotics.
In the majority of cases however the presence of the total knee replacement prevents the elimination of the bacteria causing the infection and removal of the implant is required in order to have a chance of curing the infection.
In certain cases the removal of the implant handy re-implantation of the new knee can all happen in one procedure. In the great majority of cases however the best success rate is achieved by using a two stage procedure.
After the components have been removed an antibiotic loaded articulating spacer can be used so that the patient has reasonable knee function whilst the infection is being treated with antibiotics.
Sometimes more than one debridement may be required to eliminate the infection.
When there is good evidence (blood tests and aspiration of the knee joint testing for bacteria) that the infection has been removed an attempt can be made at re-introducing a new revision total knee replacement. In the majority of cases the time to re-implantation is about 3 months but this time varies from patient to patient.
The x-rays below show this 71 year old gentleman had an infected total knee replacement. He was treated with a two stage revision. Antibiotic loaded spacers where used after the knee replacement was removed. 3 months later after the infection had settled a new revision total knee replacement was performed.