Abstract
In years past, the most common reason for revision following knee replacement was polyethylene wear. A more recent study indicates that polyethylene wear is relatively uncommon as a cause for total knee revision counting for only 10% or fewer of revisions. The most common reason for revision currently is aseptic loosening followed closely by instability and infection. The time to revision was surprisingly short. In a recent series only 30% of knees were greater than 5 years from surgery at the time of revision. The most common time interval was less than 2 years. This is likely because of the higher incidence of infection and instability that occurs most commonly at a relatively early time frame. Evaluation of a painful total knee should take into account these findings. All total knees that are painful within 5 years of surgery should be assumed to be infected until proven otherwise. Therefore, virtually all should be aspirated for cell count, differential, and culture. Alpha-defensin is also available in cases in which a patient may have been on antibiotics within a month or less, as well as cases in which diagnosis is a challenge for some reason. Instability can be diagnosed with physical exam focusing on mid-flexion instability which can be usually determined with the patient seated and the knee in mid-flexion, with the foot flat on the floor at which point sagittal plane laxity can be discerned. This is also frequently associated with symptoms of giving way and recurring effusions and difficulty descending stairs. A new phenomenon of tibial de-bonding has been described, which can be a challenge to diagnose. Radiographs can appear normal when loosening occurs between the implant and the cement mantle. This seems to be more common with the use of higher viscosity cement. Obviously this is technique dependent since good results have been reported with the use of high viscosity cement. Component malposition can cause stiffness and pain and relatively good results have been reported by component revision when malrotation has been confirmed with CT scan. When infection, instability and loosening are not present, extra-articular causes should be ruled out including lumbar spine, vascular compromise, complex regional pain syndromes and fibromyalgia, and peri-articular causes such as bursitis, tendonitis, tendon impingement among others. One of the most common causes of pain following total knee is unrealistic patient expectations. Performing total knee replacement in early stages of arthritis with only mild to moderate symptoms and radiographic changes has been associated with persistent pain and dissatisfaction. It may be prudent to obtain the immediate preoperative x-rays to determine if early intervention was undertaken and patients have otherwise normal appearing total knee x-rays and a negative work up. A recent study indicated that this was likely a cause or a major contributing factor to persistent pain following otherwise a well performed knee replacement. A national multicenter study of the appropriateness of indications for TKA also indicated that early intervention was a major cause of persistent pain, dissatisfaction, and failure to improve following total knee replacement.
