Types and Treatment of Infection After Knee Replacement
As the authors of this article point out, infection after total knee replacement is the most "dreaded and difficult" of all complications. Joint infection can be difficult to treat, requiring removal of the implant and revision surgery to put in a second implant.
According to their review of the literature, this problem is increasing not decreasing. Up to two per cent of all senior adults who have this surgery will end up with an infection that requires further treatment. The rate of failure due to infection is double that for revisions so having a second surgery doesn't necessarily mean the end of the problem. In fact, almost 17 per cent of revision total knee arthroplasty (TKA) procedures end in another surgery.
If this problem isn't turned around in the next 10 years, it is estimated that two-thirds of all revision procedures will be needed because of post-operative infection. Prevention is the key but today's bacteria are stronger and more resistant to antibiotics than ever before. Prevention strategies are not the focus of this article. Instead, surgeons treating patients with this problem will appreciate the review of treatment options provided.
The authors start out by classifying knee infections that occur after the primary (first) total knee replacement as one of four types: 1) infection present at the time of the primary total knee arthroplasty, 2) infection develops within the first 30-days after surgery, 3) infection goes into the blood but symptoms only last four-weeks, and 4) a chronic infection lasting more than 30-days.
Treatment is based on the infection type and condition of the patient. Treatment choices include: antibiotics, irrigation and debridement, removal and replacement of the implant, arthrodesis (fusion), and (worse case scenario): amputation. Who gets what treatment? That's the question these authors try to answer.
First, they suggest that antibiotics alone (called antibiotic suppression) is very ineffective (20 per cent success rate) and only used for a small number of patients. These are folks who are too sick for surgery, who have a stable implant (not loose), and a bacteria that is considered "low virulence" (in other words, not terribly strong or destructive).
The preferred treatment is actually more of a combined management approach. Open incision with irrigation and debridement works best for acute infections. But the surgeon must take into consideration several factors when using just this approach. For example, patient health, type of bacteria present, length of time since the primary surgery, and other patient risk factors must be reviewed and assessed before using this treatment option.
More often, it is necessary to remove the infected implant, clean out the joint, and replace some of the component parts of the implant. The replacement procedure is referred to as an exchange arthroplasty. The exchange arthroplasty can be a one-step or two-step process (also known as one-stage or two-stage exchange arthroplasty).
As the names suggest, in a one-stage procedure, everything is done in one surgery. In a two-stage exchange, the implant is removed but not replaced just yet. Instead a spacer that contains high-dose antibiotics is put in place instead.
Once the infection is under control, then the spacer is removed and the replacement implant installed. It is important to make sure the areas down into the bones (both the femur -- the thigh bone and the tibia -- the lower leg bone) are free of infection before putting the replacement implant in. Using long, thin antibiotic dowels down into the canals along with the spacer helps solve this problem.
When to reimplant the replacement parts is a challenge, too. Usually the antibiotics are used for at least six weeks with another four to six weeks time period off antibiotics before reimplantation can take place. Once the lab tests show the infection is cleared up, then the exchange can take place.
The more extreme options of joint fusion or even amputation are only considered when all other treatment methods have failed. Amputation may be necessary when the infection cannot be stopped and the patient is either in terrible pain or their life is threatened by the infection spreading throughout the body. In all cases, every effort is made to save the leg, save the joint, save the implant. Fusion and/or amputation are only considered when all else has failed.
In conclusion, with an expected rise in the number of older adults having a total knee replacement comes an expected increase in the number of cases of infection requiring follow-up treatment. The most common post-operative problems and complications encountered by patient and surgeon include infection, failure of the wound to heal, and loosening of the implant. The focus of this article is the management of acute and chronic cases of infection.
Bryan D. Springer, MD, and Bohannon Mason. Total Joint Arthroplasty. Management of Infection After Total Knee Arthroplasty. In Current Orthopaedic Practice. November/December 2012. Vol. 23. No. 6. Pp. 549-553.