SAN FRANCISCO, California—Studies presented at the AAOS 75th annual meeting suggest that gender-specific joint implants are not generally better than standard implants. A panel of orthopaedists debated in a press conference the merits of companies that are marketing gender-specific joint implants. They were defending against perceived industry influences and reaching a consensus that the joint should fit the body based on size and anatomy regardless of gender.¹

Orthopaedic surgeons replacing a joint usually chose from standard implants that are gender neutral. Yet more women than men will need joint replacement surgery, and manufacturers are enthusiastically marketing differently designed joints for men and women.

Robert Barry Bourne, MD, of London, Ontario, Canada and colleagues studied >3400 patients who underwent total hip replacement (THR) using a standard implant. The sampling included 1941 women whose implants lasted longer, but the study showed no statistically significant difference in clinical outcomes compared with men.

Minimum follow-up was 2 years. The only statistically significant difference was the WOMAC pain score with women scoring less pain (39.42 vs 36.13, P = .011). Cumulative revision rates were 8.3% for women and 9.3% for men. Outcome differences actually favored the women, Dr. Bourne pointed out. Women tend to wait a little longer for joint replacement surgery, he noted, whereas men tend to report more pain preoperatively.

Dr. Bourne, professor in the division of orthopaedic surgery at the University of Western Ontario, said that “despite what implant we use, the surgical technique will make the difference.” Another study he investigated shows no difference with use of gender-specific knee implants.

William Timothy Brox, MD, staff orthopaedic surgeon at the Fresno Kaiser Permanente Medical Center in California, said that “outcome data should justify the need for new implants,” gender specific or not. The Kaiser registry prospectively enrolls all joints operated on by Kaiser surgeons. Of 7468 knees replaced in men, 13250 replaced in women, and with >9 months of follow-up, women improved by 5.41 points on an analog scale of pain, whereas men improved 5.05 points, a statistically significant difference (P <.001). Revision need was not different, nor did the range of motion differ between men and women with total knee arthroplasty (TKA).

“We don’t feel the difference was clinically clear. I can’t advocate spending $1000 differential charge for 64% of our TKA surgeries,” Dr. Brox said.

Media panel participant, Andrew Glassman, MD, said that “in some instances gender-specific designs are useful, at the extremes of both [men’s and women’s anatomies]. We don’t have scientific data to demonstrate gender-specific differences in survivorship of THR, but we do have demonstrated differences in anatomy.” Dr. Glassman, associate professor of orthopaedic surgery at the Ohio State University College of Medicine, referred to women’s smaller metaphyses, head height, and offsets in their hips, “and all are increased by degenerative osteoarthritis.”

Dr. Glassman also emphasized that expertise determines the success of implant surgery, regardless of implant’s gender specificity. “If you don’t [replace many] hips, you are less confident of cutting extra bone” to fit a prosthesis to a patient.

Greater recognition of gender differences will educate surgeons to carefully consider the surgical plan and to greater postoperative surveillance, Glassman concluded.

Reference

1. X-why? The gender implant: Necessity or trend? Presented at: AAOS 2008 meeting; March 6, 2008; San Francisco, Calif. Press conference.