Current Status of Revision Total Knee Arthroplasty: How Do We Assess Results?

Failure of primary total knee arthroplasty within five years after the operation most frequently occurs because of deep infection (38%), instability (27%), failure of bone ingrowth into a cementless implant (13%), patellar problems (8%), wear (7%), loosening (3%), or miscellaneous problems (4%)1. In contrast, in a series of 427 revision total knee arthroplasties, failure of fixation was the most frequent problem, followed by abnormal alignment, component malposition, osseous fracture, and patellar problems2. The results of revision total knee arthroplasty are difficult to assess because they are influenced by many factors: the etiology of failure, the extent of bone loss, the quality of the soft tissues, the technique of reconstruction, the adequacy of rehabilitation, patient compliance, the duration of follow-up, and the mode of assessment. Contemporary modular designs have provided good short-term results. A combined review of 161 revisions that had been performed with a modular constrained condylar knee or posterior stabilized design revealed an 80% rate of good or excellent results after an average duration of follow-up of 3.5 years, with a 33% prevalence of radiolucent lines and a 10% rate of complications3. The durability of the results will depend in part on the integrity of the locking mechanisms of the modular components, the quality of the polyethylene, and the load transfer conferred by modular stems and augments to the implants. Long-term studies will be necessary to determine if these modular designs are more durable than nonmodular prostheses.