Loosening as a cause of failure of total knee replacement
This is the second in a series of posts examining causes of failure of total knee replacement.
Primary total knee replacement surgeries are usually performed to help people with end-stage degenerative knee changes get rid of pain and return to a more active lifestyle. Knee replacement surgeries are generally successful and represent one of the most successful procedures in orthopedic surgery and medicine in general. However, knee replacements can fail. Knee replacements can fail from a myriad of reasons. The second cause of total knee replacement failure to be examined in this series is loosening.
Total knee replacement prostheses can be press-fitted or cemented in place. Most knee replacements are cemented in place, and this can be argued to be the gold standard of implanting knee replacement components. When a cemented knee replacement debonds from the cement or the cement debonds from bone, it becomes a loose implant/knee replacement.
A loose implant can cause pain. Any of the components in a knee replacement can become loose (femoral, tibial, or patellar components). The pain from a loose knee replacement can be debilitating or be tolerable. When tolerable and non-limiting, it can be managed without surgery as long as the affected bone has not been damaged by the loose implant. People with pain from a loose implant can present in different ways. People can have pain at rest or with activity though pain typically worsens with walking or standing. Some people have mechanical start up pain i.e. the pain is really bad with the first several steps, and then gets somewhat better albeit still present. Other complaints can include recurrent effusions (knee swelling).
Grossly loose knee replacement implants/components can be readily identified on x-rays because these implants might demonstrate progressive lucencies around the implants (or cement) on x-rays. Other x-ray findings can include subsidence. This is where the implant is collapsing or settling into bone. Diagnosis of loosening in these cases can be readily made. Cases of subtle loosening can be more difficult to diagnose especially when without obvious evidence of subsidence. Physical examination is not always diagnostic in these cases. Some patients might require a bone scan to help make a diagnosis. However, it must be noted that a bone scan is not exactly a very accurate test to diagnose a loose implant.
A fellowship trained joint surgeon can diagnose a loose knee replacement. Some knee replacement implants don’t have a good track record, and findings on x-rays for loosening might be subtle and lucencies around the implant might not even be progressive (increasing/worsening over a time period). 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. Conservative measures can include over the counter pain medications like Tylenol, Aleve, Advil etc. Other conservative measures can include physical therapy or benign neglect (no intervention). Benign neglect is certainly a viable option if the knee is not particularly bothersome. Surgical management is indicated if the knee pain is not tolerable, and is limiting. Surgical management usually begins with ruling out an infection as an infection could be present even in the case of knee replacement loosening and can actually be a reason for the loosening. Knee replacement 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. Revision implants would typically by-pass the length of the implants to be removed at the time of revision surgery. Knee revision surgery is more complex than a primary knee replacement surgery, and can be expected to take longer, involve more blood loss, and involve a more extensile surgical exposure. This can impact the rehabilitation process, and it might be slower when compared to rehabilitation from a primary knee replacement.
The goal of knee revision surgery for loosening 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. If you have a painful knee replacement and haven’t been able to figure out the cause, call Hays Orthopedic Institute at 785 261 7599 to schedule an appointment with Dr. Akinbo.