Hip Resurfacing Shows Narro...

AAOS SAN FRANCISCO, March 7, 2008 - Some of the purported advantages of hip resurfacing over standard arthroplasty, though not all, seem to be real, researchers found in a randomized trial.

But other pluses in activity and function can probably be chalked up to patient selection bias and expectations, reported Martin Lavigne, M.D., of the University of Montreal, and colleagues, at the American Academy of Orthopaedic Surgeons meeting here.

In the randomized trial, patients who had hip resurfacing were significantly more likely to return to work and sports and had better step and hop test scores than standard arthroplasty patients did.

But functional scores and range of motion were no better than with hip replacement, the investigators found.

Hip resurfacing gained popularity with patients and some orthopedic surgeons on the basis of assumptions about better clinical function and ability to return to a high level of activity.

While retrospective cohort studies reinforced this perceived benefit, Dr. Lavigne said, "obviously there was a bias in the patient selection for hip resurfacing." Patients who sought hip resurfacing tended to be younger, more active, healthier, and expected a more active life after surgery, he said.

The newer procedure is still controversial among orthopedic surgeons despite rapid increases, commented Tom Schmalzried, M.D., of the Orthopaedic Hospital in Los Angeles, in a press conference where there was debate over the two approaches.

"The results of good, modern total hip replacement are really, really good," he said. "So for resurfacing to have a favorable risk-to-benefit ratio, you have to show you are getting something you don't get with total hip replacement."

For a more objective answer to this issue, Dr. Lavigne's group randomized 210 patients who were candidates for either procedure to undergo either uncemented 28-mm metal-on-metal total hip arthroplasty or hybrid metal-on-metal hip resurfacing.

All procedures were done by the same three surgeons with a posterior approach. Patients were informed which surgery they underwent only afterward.

Patients had a mean age around 50. Body mass index was higher in the total hip arthroplasty group.

Functional scores were slightly worse in the hip replacement group at six months (17 versus 11 on the WOMAC scale) but identical by two years (5 for both).

At six months after surgery, hopping on the affected leg was significantly easier for resurfacing group patients ("easy" or "very easy" 91.7% versus 78.9% and "difficult" or "impossible" 8.3% versus 21.1%, P=0.023).

Likewise, climbing stairs in a step test was easier at six months in the resurfacing group compared with the replacement group ("easy" or "very easy" 94.4% versus 76.3% and "difficult" or "impossible" 5.6% versus 23.7%, P=0.015).

Hip resurfacing group patients were also more likely to return to their prior work (96% versus 83%, P=0.02).

The young age of the patients made this an important outcome, Dr. Lavigne said.

Among the patients, 152 had data on activity level pre- and post-procedure.

Despite similar activity levels before surgery (P=0.22), more hip resurfacing than hip replacement patients returned to sports activities by one year after surgery (15% versus 7% high impact and 38% versus 28% moderate impact activity, P=0.022).

On a scale that included activities of daily living as well as sports, the difference tended to favor hip resurfacing but was not significant at one year (P=0.074).

"Both groups returned to a high level of activity," Dr. Lavigne said. "Hip resurfacing patients seem to be more active, but not as much as expected."

Type of surgery had no significant impact on what factors patients reported as limiting their return to sports activities, including implant protection, discomfort, fear of instability, and thigh pain.

Hip range of motion -- including total arc, arc of rotation, flexion-extension arc, and abduction-adduction arc -- was also similar for both groups among the 122 patients with data on this outcome (P>0.05).

Satisfaction with the procedure was uniformly high over time and across treatments.

While resurfacing is a more aggressive technique, Dr. Lavigne said, the rate of complications was similar between groups.

Long-term follow-up will be important to determine whether there are differences in need for revision between the procedures, he concluded.

Dr. Lavigne reported receiving research or institutional support from Zimmer, Stryker Howmedica, Biomet, DePuy, and Smith & Nephew and consulting for Zimmer.

Dr. Schmalzried reported receiving research or institutional support from Stryker, DePuy, Johnson & Johnson, Corin, and Wright Medical Technology; receiving miscellaneous funding from Stryker, DePuy, Johnson & Johnson, Corin, Wright Medical Technology, Zimmer, and Smith & Nephew; receiving royalties from Stryker, DePuy, Johnson & Johnson, Corin, and Wright Medical Technology; holding stock options in Stryker, DePuy, Johnson & Johnson, Corin, Wright Medical Technology, Zimmer, Biomet, Bristol-Myers Squib, and Pfizer; and being a consultant for Stryker.

Primary source: American Academy of Orthopaedic Surgeons meeting
Source reference:
Lavigne M, et al "Range of motion after hip resurfacing and THA: A single-blind randomized clinical study" AAOS meeting 2008; Abstract 058.

Additional source: American Academy of Orthopaedic Surgeons meeting
Source reference:
Lavigne M, et al "A randomized study comparing surface replacement arthroplasty to total hip arthroplasty" AAOS meeting 2008; Abstract 056.

Additional source: American Academy of Orthopaedic Surgeons meeting
Source reference:
Lavigne M, et al "Return to sports after hip resurfacing and total hip arthroplasty: A randomized clinical trial" AAOS meeting 2008; Abstract 053.