Positive Results for Hip Implants in Young and Old

Two studies found that people younger than 50 and older than 90 fare well with new hips.


Two studies presented at the American Academy of Orthopaedic Surgeons (AAOS) annual conference this month offer new assurances to younger and older people who are considering a new hip. One study found that many hip replacements implanted in adults younger than 50 are still performing well 35 years later. Another found that undergoing hip replacement surgery at age 90 or older is relatively safe.

Arthritis is the most common cause of hip pain and disability, according to the AAOS, and a new hip can often relieve the problem. Most people who undergo hip replacement surgery are between ages 50 and 80.

Keeping Older Patients Mobile

But doctors are seeing more older patients who might benefit from the surgery. “The number of 90-year-olds has tripled over last 30 years,” says Alexander Miric, MD, assistant chief of orthopaedic surgery at Kaiser Permanente in Los Angeles and lead author of the study on hip implants in older patients. “We thought it would be interesting to see how well patients in their 90s do after hip replacement surgery.”

Past studies of this age group showed high infection and mortality rates, but they involved only a small number of patients, and some studies were decades old, says Dr. Miric. “These numbers didn’t look very encouraging, but in our own personal experience, we saw patients do very well.”

Using Kaiser’s registry of joint replacement patients, started in 2001, Dr. Miric and his colleagues identified 183 patients who were 90 or older at the time of hip replacement surgery. They found that compared to people younger than 80, these patients stayed in the hospital only about half a day longer and were not significantly more likely to develop an infection of the joint. They did have a higher mortality rate within 90 days of the surgery – 2.7 percent versus 0.2 percent – but, says Dr. Miric, “you would expect that in this age group.”

“If you make it into your 90s, you must have something going for you that helps you do well with surgery,” says Dr. Miric. “I think you have to stop looking at age as an indicator and look at how robust the person’s health is.”

The oldest patients did have an almost 10 percent greater risk of being readmitted to the hospital within 90 days, either due to surgery complications (such as urinary tract infections) or other reasons, compared to patients younger than 80. “It may just take longer for them to recover from this surgery, and we have to keep a close eye for a longer period before we can conclude that they’ve successfully recovered,” says Dr. Miric.

Why would a surgeon put a new hip in someone nearing the end of life? “They have pain and disability and it can have a severe impact on their quality of life and their ability to take care of themselves,” says Dr. Miric. “They may need it in some cases even more than someone who’s younger.”

Michael Parks, MD, associate attending orthopaedic surgeon at the Hospital for Special Surgery in New York, agrees. “We’re really seeing more patients over 90 years old that come in and they’re in pretty good health, but they have an aching knee or hip. It’s a quality-of-life issue. There are people that may be otherwise functional, able to do things, care for themselves, and they’re becoming progressively less able to do those things because of a painful hip.”

Dr. Parks called the mortality rate in the study small. “I would agree with the author’s conclusion, and that’s what we can take away from [the study]: These patients can safely undergo total hip replacement when compared to younger groups of patients.”

An Implant May Last a Lifetime

The second study involved a group of people who got their hip implants when they were between ages 18 and 49. Researchers have been checking on them periodically for 35 years to see how they and their implants were faring.

“We’ve been following them throughout the years,” says study co-author Lucian C. Warth, MD, a senior orthopaedic surgery resident in the department of orthopaedic surgery at University of Iowa Health in Iowa City. “It’s the longest study as far as follow-up goes of any total hip replacement yet.” 

The original group consisted of 69 patients who received hip implants from the same surgeon in the 1970s. Today, among the patients still living, the researchers found that 46 percent of the original hip implants were still in place and functioning. In addition, many of the patients who died in the interim did so with their original implant in place. Overall, 63 percent of the original hip replacements were functioning at the latest follow-up or at the time of death.

Dr. Warth considers the results good news. “If I put a hip in someone who’s 50 years old, based on this study I can say with almost two-thirds probability that the hip will outlast them,” says Warth. “That’s a real win for us because we just don’t want these folks to have to go through another big operation.”

The reality is probably even more positive, says Dr. Warth. He notes that the implant used in the study has long since been replaced by newer implants and techniques, so today’s hip replacements should, in theory, perform even better.

The durability of hip implants in younger people is important not just because the patients will presumably live for many years with the hip, but also because they’ll be relatively active for many of those years. “We know that hip replacement works well and has long-lasting good results in patients who are in their 60s and 70s,” says Dr. Parks. “The problem is that hip replacements fail at higher rates in younger patients because of increased level of activity.”

But with the results from this long-term study, says Dr. Parks, “We can look at these patients and give them an idea of the success of the procedure. At 35 years, over half of [the hips] are still going to be functioning. I think that’s pretty good. It’s better than what we tell patients.”

And, Dr. Parks agrees, the real outlook may be rosier. “We use cementless implants, which we think are going to last longer.”

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