Part 2: Causes of failure of total knee replacement
Knee replacement surgeries are performed to help people with end-stage arthritis in their knees get rid of pain and return to an active lifestyle. Knee replacements can fail, and can fail from a myriad of reasons. The second cause of total knee replacement failure to be examined in this series is loosening.
Most knee replacements are cemented in place. When a cemented knee replacement debonds from the cement or the cement debonds from bone, it becomes a loose implant/ replacement. Any of the parts in a knee replacement can become loose, and cause pain. The typical patient has pain that worsens with bearing weight though pain can be present at rest; recurrent swelling can be present.
Grossly loose knee replacement parts can be readily identified on x-rays because these implants demonstrate progressive lucencies around the implants (or cement). Other x-ray findings can include the implants settling into bone. Cases of subtle loosening can be more difficult to diagnose. Some patients might require a bone scan to help make a diagnosis. With a good history and examination, x-rays, and knowledge of the track record of the implants in place, a fellowship trained joint replacement surgeon can readily diagnose a loose knee replacement.
The treatment for a loose knee replacement can be started conservatively with anti-inflammatory medications. Surgical management is indicated if the pain is not tolerable. Surgical management begins with ruling out an infection as an infection can be present even in the case of implant loosening and can be the reason for the loosening. Revisions/re-dos for loosening require careful planning, and depending on multiple factors (implant track record, physical exam findings, x-ray findings, surgeon and patient preference) can involve revision of the loose component only or revision of all the knee replacement components. The goal of re-do surgery is to restore good fixation to the revised component(s). This would usually result in improvement in functioning, and decrease in pain, but the results don’t always rival the results from a primary knee replacement.
Dr. Oluwaseun Akinbo M.D. is an orthopedic surgeon at HaysMed. For more information, see www.haysmed.com/oluwaseun-akinbo