Total Knee Arthroplasty (TKA), commonly known as total knee replacement, is a highly successful procedure designed to alleviate pain and restore function in a damaged knee joint. Over time, however, the artificial joint may fail, necessitating a second surgery called a Revision Total Knee Arthroplasty (RTKA). This revision is a more complex operation than the initial replacement, involving the removal and replacement of some or all of the implant components. If this revision fails, subsequent surgeries may be needed. There is no set number of revisions a person can undergo; instead, the physical limits are determined by the remaining quality and quantity of the patient’s bone structure.
Common Reasons for Revision Failure
A total knee replacement or a prior revision can fail for several distinct reasons, generally categorized by the time elapsed since the surgery. Early failures, typically within the first two years, are often related to technical issues or infection. Instability can arise from improper positioning or alignment of prosthetic components or inadequate balancing of surrounding soft tissues and ligaments. Periprosthetic joint infection (PJI) is a devastating cause of early failure and a leading cause for all revision surgeries.
Late failures, occurring many years after the initial procedure, are more frequently related to the long-term mechanics and materials of the implant. Aseptic loosening is a common late-stage problem where the bond between the implant and the bone fails without infection. Another element is polyethylene wear, where the plastic spacer between the metal components wears down, releasing microscopic debris that can trigger a bone-resorbing reaction called osteolysis. Malalignment can also contribute to mechanical failure over time by unevenly stressing the implant.
The Role of Bone Stock in Determining Limits
The ultimate constraint on the number of revision surgeries is the condition of the patient’s bone stock, which refers to the available bone structure needed to support and anchor a new implant. Each successive surgery requires the removal of the old components, often involving cutting away additional bone to access fixation points and prepare the surface for a new prosthesis. The failure of the previous implant itself, whether from infection or aseptic loosening, can also destroy significant amounts of bone tissue.
When substantial bone is lost, a standard replacement component cannot be used because it lacks stable fixation. To compensate for these defects, surgeons employ specialized components and techniques.
Specialized Implants and Grafting
These techniques include metal augments, which are wedge-shaped pieces of metal used to rebuild the joint line. Larger defects extending into the metaphysis may require highly porous metal cones or sleeves that are press-fit into the remaining bone for biologic fixation. These specialized implants often feature long, thick stems that extend deep into the bone canal for added stability, transferring stress away from the weakened joint area.
Bone grafting, using either the patient’s own bone (autograft) or donor bone (allograft), may be necessary to fill large voids and encourage structural support. Despite these advanced reconstructive options, the remaining bone structure may become too compromised to provide a stable foundation for a new implant. Once severe bone loss makes the joint non-reconstructible, the physical limit for further revision surgery is reached, forcing consideration of final, non-revision surgical alternatives.
Increased Risks Associated with Repeated Surgery
Beyond the anatomical limits of bone stock, the patient faces progressively higher clinical risks with each subsequent revision procedure. The complexity of the surgery increases dramatically, often leading to a longer operative time and greater blood loss, which increases the likelihood of requiring a blood transfusion. The risk of periprosthetic joint infection (PJI), already higher than the initial TKA, increases exponentially with every additional surgery due to scar tissue and prolonged exposure.
Furthermore, the functional outcomes of repeated revisions are generally less favorable than those of the primary surgery. Studies indicate that each successive revision tends to be less successful and the implant survival time is progressively shorter. For example, the expected lifespan of a second revision may be only half that of the first. Repeated manipulation of the surrounding tissues also increases the risk of damage to nearby nerves and blood vessels, and the joint is more likely to experience stiffness or a reduced range of motion after recovery.
Surgical Options When Revision is No Longer Possible
When a patient has exhausted the structural possibility for further revision or the associated risks become unacceptably high, the orthopedic team must turn to definitive salvage procedures. The most common final option is Knee Arthrodesis, or joint fusion, which surgically locks the femur and tibia together. This procedure eliminates all movement in the knee but provides a stable, pain-free limb that can bear weight without the need for an implant.
A less common alternative is a Resection Arthroplasty, sometimes referred to as a Girdlestone procedure, where the implant and infected or damaged bone are removed, and no new joint is implanted. This leaves a flail joint, which is a shortened and unstable limb, but it can be used as a last resort for severe, uncontrollable infection. Amputation is the most drastic final option, reserved for cases where infection cannot be eradicated, or the limb is so damaged that it is nonfunctional and a threat to the patient’s overall health.