For more than four decades, total hip replacement has dramatically reduced pain and improved function in patients with severe joint damage from osteoarthritis, rheumatoid arthritis and other causes. But a new study aims to pinpoint how significant the improvement can be on an individual, patient level after the surgery – which is also called total hip arthroplasty (THA).

Researchers say most previous data has primarily compared outcomes on a group level between those that had the procedure and those that did not. “The study provides more insights and a clearer picture of what happens to people after the surgery at two and five years.” says lead author Jasvinder Singh, MD, an associate professor of medicine in the division of clinical immunology and rheumatology at the University of Alabama at Birmingham School of Medicine. “I think this study helps clarify for patients and their providers and policy makers what patients can expect in explicit terms.”

According to various estimates, approximately 430,000 total hip arthroplasties were performed in the United States in 2009 – and that number is expected to triple by 2030, according to a projection made by researchers at Exponent, an engineering and scientific consulting firm, published in The Journal of Bone and Joint Surgery in 2007. It is a common treatment for severe end-stage arthritis.

The study, published in the February issue of the journal Rheumatology, analyzed data from the Mayo Clinic Total Joint Registry, which contains information on nearly all of the joint replacement surgeries done at Mayo Clinic since it performed the first FDA-approved total hip replacement roughly 43 years ago. This research looked at 6,168 patients getting their first (or primary) total hip replacement and 2,063 getting revision surgery between 1993 and 2005.

Patients answered questionnaires (by mail, telephone or during a doctor visit) two and five years after surgery. Patients on average were in their mid 60s.

Researchers found that improvements were more significant in those getting their first surgery and those whose pain and limitations was “moderate” before the procedure rather than “severe.”

The researchers found, for primary THA patients, among those with “moderate” preoperative pain, 94 percent reported “mild” or “no” pain after 2 years and 91 percent reported “mild” or “no” pain after 5 years.

Among patients with “severe” preoperative pain, 91 percent reported “mild” or “no” pain after 2 years and 89 percent reported “mild” or “no” pain after 5 years.

For revision THA patients, among those with “moderate” preoperative pain, 84 percent reported “mild” or “no” pain after 2 years and 80 percent reported “mild” or “no” pain after 5 years.

Among those with “severe” preoperative pain, 77 percent reported “mild” or “no” pain after 2 years and 78 percent reported “mild” or “no” pain after 5 years.

“Patients can look at this and say – if I have severe pain before surgery, what are the chances I’ll end up with mild pain after. If your pain went from severe to moderate or moderate to mild, I don’t think there’s any question that you will perceive that as meaningful,” Dr. Singh explains. “This is an easier way for patients to look at the data and understand what will happen to them depending on their preoperative status.”