Modes of Failure in Total Knee Arthroplasty

A knee replacement that has failed or is functioning at a level below the expectations of the patient is a difficult situation to address. The evaluation process must be individualized, and all potential causes for the failure or dissatisfaction must be considered. Knee replacement failure is usually multifactorial, and the evaluating surgeon must define the most likely cause while considering all other potentially contributing issues. The evaluation involves a complete history and exam followed by radiographic and often laboratory evaluations. A systematic approach is useful, but a diagnosis can remain elusive even in the hands of an experienced joint replacement surgeon. Defining the patient’s expectations and physical demands is as critical as gaining a thorough understanding of the patient’s medical, surgical, and social history. It is then important to appreciate what the patient perceives as the problem; in many situations, this will guide your focus. For example, patients may describe the knee as stiff, painful, or unstable. Though this does not seal the diagnosis, the patient’s perspective provides meaningful clues as to what needs to be addressed. Putting a time frame on when the patient began to have problems with the knee further focuses the problem solving. Some cases will have been problematic from the time of the index arthroplasty, which is concerning for indolent infection or component malposition. Other knees may have functioned well for a period of time before becoming problematic, as in the case of aseptic loosening from polyethylene wear. Simply performing a thorough initial history allows the surgeon to develop a context for this particular problematic knee. Addressing why the knee failed requires further investigation; a thorough musculoskeletal and neurovascular exam is warranted. Review of the operative record provides critical information on implants used and technical variables. Investigation of perioperative complications-such as persistent wound drainage or unexpected returns to the operating room-and postoperative rehabilitation protocols provides further useful data. The surgeon can build a differential diagnosis for the etiology of the failed knee arthroplasty by answering who, what, when, and why. The final step to fully define the problem requires an understanding of how knee replacements fail. That is the focus of this chapter.