Although knee replacements normally perform well for at least 20 years in more than 95 percent of patients, this figure is based on the data collected from follow-up of patients who have undergone Total Knee Replacements and have had successful outcome over the years and this figure will likely change as more and more data is available for research.
There are five primary reasons why a knee implant fails:
- Wear and loosening: Friction caused by joint surfaces rubbing against each other wears away the surface of the implant causing bone loss and loosening of the implants.
- Infection: Large metal and plastic implants can serve as a surface onto which bacteria can latch.
- Fracture: Fractures around the knee implant that disrupt its stability may require revision surgery.
- Instability: A sensation of the knee “giving away” may mean that the soft-tissue surrounding the knee is too weak to support standing and walking. Improperly placed implants may also cause instability.
- Stiffness: Loss of range of motion which causes pain and a functional deficit.
Failed knee implant is usually caused by wear and tear with subsequent loosening of the implant. Other causes are infection, instability, fracture, or stiffness. The most common symptoms of a failed knee implants are pain, instability, swelling and stiffness across the entire knee (generalized) or in a small section (localized).
Revision total knee replacement is a complex procedure that requires extensive pre-operative planning, specialized implants and tools. It usually takes longer to perform than the original knee replacement. Revision surgery needs thorough investigations including X-rays, laboratory tests, knee aspiration and in some cases additional assessments, such as bone scans, CT scans or magnetic resonance imaging (MRI). During a revision knee replacement surgery, the in-situ implant is removed and bone grafts may be used to fill larger areas of bone loss. In some cases, metal wedges, wires or screws may be used to strengthen the bone. Finally, specialized revision knee implants are inserted. Post-operative care is very similar to the care of the original knee replacement.
More than 75 – 80 percent of patients who went revision knee surgery can expect to have good to excellent results. With the right tools at hand, revision total knee replacements can deliver the best outcomes possible.