When a hip or knee replacement needs to be done again

My mother had hip replacement surgery during the COVID-19 pandemic, after a fall that broke her left hip. She was 93 years old. The hip replacement meant she would not have to suffer the ongoing pain of a fractured hip or the limitations that would hinder her independence. I was amazed at how well she did after the surgery with the support of physical therapy, which helped with her subsequent recovery.

Now 96, she reluctantly uses a walker to support her deteriorating bilateral total knee replacements that were done in the 1990s and have far outlived their warranties.

“It is amazing how many hip fractures we see in people in their 90s,” said Kevin Dwyer, MD, an orthopedic surgeon with Cape Cod Orthopaedics and Sports Medicine in Hyannis. “I have never seen as many active 90-year-olds as there are on Cape Cod.”

While Dr. Dwyer performs total hip replacement and total knee replacement surgeries, he also specializes in hip replacement and knee replacement revisions.

Total hip replacement and total knee replacements involve removing the joint that has deteriorated, due to osteoarthritis or injury, and replacing it with synthetic components to reconstruct the joint and provide mobility, according to The National Library of Medicine.

In total hip replacement surgery, the damaged joint and cartilage are removed and replaced with plastic and metal or ceramic components.

Total knee replacement surgery involves replacing the knee joint with an implant made of metal and plastic parts.

“Of all the hip and knee replacements we perform, 95 percent of hip replacements and 85 percent of knee replacements do very well and complications are very low,” said Dr. Dwyer.

When Revisions Are Necessary

When there are complications, revision surgery may be necessary. It is a reoperation of the original total joint replacement to treat infection and/or replace the affected parts that were placed during the original surgery.

The following are the top reasons for a hip replacement revision, according to Dr. Dwyer:

• Infection: This is one of the most common reasons for revision.
• The implanted parts loosen, which is called aseptic loosening.
• Wear
• Instability
• Hip popping out of place, also known as dislocation.
• Periprostatic fracture when a person falls and breaks the bone close to the metal or plastic parts of the hip replacement.

“Knee replacement revisions happen for similar reasons as the hip replacement revision,” he said. “The number one cause is an infection, second is loosening and wear, and the last is instability.”

With infection being the top reason for hip and knee replacement revisions, Dr. Dwyer stresses the importance of infection prevention.

“Anytime you have a hip or knee replacement, you should be concerned about infection,” he said. “Take care of any scrapes or cuts and urinary tract infections. Never let infections fester or get out of control and treat them quickly. There is always a risk of bacteria spreading into your blood and infecting your joint, which becomes a very big problem.”

How Hip and Knee Replacement Revisions Work

When a revision of the hip replacement or knee replacement is needed due to an infection, it depends on the type of infection as to what we do, Dr. Dwyer said. The infection can be in the surgical wound or deep in the joint around the metal or plastic implants. If the infection is from an acute infection, then surgery is performed to clean the implant, remove changeable parts and place spacers. The patient receives antibiotic therapy to treat the infection with the hope of replacing the joint, once the infection has resolved.

With a chronic or late infection for more than a month, the synthetic parts are removed and replaced with spacers until the infection is resolved with antibiotics. Once the infection has cleared, a new prosthetic can be implanted.

“If the revision needs to be done for loosening parts, we take out the loose parts and replace them with a different technology, such as a new piece that may be bigger than we used before and has a different way of fixing to the bone,” said Dr. Dwyer.

One of the reasons hip replacement revisions are more frequent on Cape Cod is due to periprosthetic fractures, said Dr. Dwyer. Older and even younger people who have had a total hip replacement and then have a fall can break the bone around the insertion of the thigh bone prosthetic piece, which makes the hip unstable and requires revision.

Dr. Dwyer foresees exponential growth in both the number of hip and knee replacements and revisions over the next 20-30 years. As the new technology continues to get better, 80 percent of the patients will still have their joint replacements 20 years from now, he said.