For people with severe symptomatic hip osteoarthritis, total hip replacement (THR) alleviates hip pain and improves function much more effectively than a resistance training program supervised by a physiotherapist, according to the results of a randomized controlled clinical trial.
In the PROHIP study, the mean increases in Oxford Hip Scores from baseline to 6 months were 15.9 points for THR and 4.5 points for resistance training. The 11.4-point difference in scores was both statistically and clinically significant, the study’s investigators reported in The New England Journal of Medicine.
“Our results are clear: Surgery is superior to exercise in patients who have hip osteoarthritis and indication for surgery, and now we have finally proven that with the highest level of evidence,” corresponding author Thomas Frydendal, PT, PhD, MSc, told this news organization.
Frydendal, who was involved in the study while working on his PhD at University Hospital of Southern Denmark – Lillebaelt Hospital, Vejle, Denmark, the primary center for the trial, is now a postdoctoral researcher at the Department of Clinical Medicine, Aarhus University, and Department of Orthopedic Surgery, Aarhus University Hospital.
“We believe that our findings are pretty robust,” Frydendal added. “I think if someone in the world conducts a trial similar to ours, they will find fairly close or consistent findings, no matter what type of exercise they choose.”
Charlotte Dahl, Lillebaelt Hospital–University Hospital of Southern Denmark, Vejle Hospital
Dr. Thomas Frydendal
The PROHIP Study
THR is routinely recommended for the management of severe hip osteoarthritis, but since there are no clinical trial data on the effectiveness of this procedure as compared with first-line treatment such as resistance training, the PROHIP study was conceived.
The trial was conducted at four Danish orthopedic centers and designed as a superiority study, the hypothesis being that THR would be better at alleviating self-reported hip pain and improving hip function than resistance training.
Of a possible 1474 individuals with a clinical suspicion of hip osteoarthritis, 791 were deemed eligible for inclusion in the trial. Inclusion criteria were being aged 50 years or older and having an indication for THR based on the presence of hip pain and clinical and radiographic findings.
However, the majority (86%) declined to enter the study, with almost half (43%) deciding to have a THR and enroll in a parallel observational cohort. This meant that only 110 (14%) individuals agreed to participate and underwent randomization, which does limit the study’s generalizability, the PROHIP investigators acknowledged.
Design and Study Population
The change in Oxford Hip Score from baseline to 6 months was selected as the primary outcome measure based on the findings of a prior qualitative study. This 12-item, patient-reported outcome measure gives a score ranging from 0 to 48, with higher scores indicating less hip pain and better hip function. The estimated minimal clinically important difference is a change of 5 points.
After a baseline assessment, 53 of 109 individuals were randomly assigned to undergo THR and 56 to participate in the resistance training program. Overall, the mean age of participants was 67.6 years, and half were women. The average duration of hip pain was a median of 1.7 years.
The median time to receipt of the allocated treatment was 2.8 months in the THR group and 0.5 months in the resistance training group.
Those allocated to the THR group also underwent a “fast track” program that involved patient education, pain management, and early mobilization.
The resistance training group received 12 weeks of exercise supervised by a physiotherapist and then offered 12 weeks of additional exercise conducted on their own. The physiotherapist-supervised exercise sessions were held twice weekly and lasted for 1 hour. These started with a 10-minute warm-up on a stationary bike, followed by a standard set of resistance-based exercises that included a leg press, hip extension, hip flexion, and hip abduction.