SAN FRANCISCO The panel title X-Why? The Gender Implant lured a considerable crowd of journalists to the media briefing room at the American Academy of Orthopaedic Surgeons (AAOS; Rosemont, Illinois) annual meeting last week. The discussion that followed lived up to the energy of the ongoing debate and the pre-briefing hype.

The panelists seemed mostly of one mind: the recent trend toward gender-specific implants by some orthopedic manufacturers is more marketing hype than a matter of clinical necessity.

One dissident, Andrew Glassman, MD, of the Ohio State University Medical Center (Columbus), held up the pro end of the discussion, saying, In some instances, gender-specific implants are useful.

He said that enormous strides have been made in sizing of implants to better accommodate the differences between men and women, but answered his rhetorical question, Does this mean we re done and should stop trying? with a resounding no.

We need greater recognition of the differences between male and female hips, and need more attention paid to pre-operative planning.

Glassman acknowledged: we don t have any scientific data to demonstrate gender-specific differences in the survivorship of THR [total hip replacement} implants, or widely recognized differences in the clinical outcome of THR in females versus males.

But, what we do have is indisputable scientific proof of significant differences between the male and female anatomy.

He said those patients at the periphery of anatomic norms would benefit most from gender-specific implants.

Taking a definitely opposing view was Robert Bourne, MD, of London Health Sciences Centre and the University of Western Ontario (London, Ontario), who cited results of a study of 1,735 patients to assess gender differences in implant size, neck length, offset and associated fractures.

Based on this study, he said, there seems to be little clinical need for gender-specific primary THRs.

Timothy Brox, MD, of Kaiser Permanente, said that at the 2007 AAOS meeting, we were told that women were not doing as well as men were with implants [but] it was our impression that this wasn t necessarily true.

He and his Kaiser Permanente orthopedic colleagues nationwide developed a registry modeled on the Swedish National Joint Registry, which has been in operation since 2001. The Kaiser registry potentially enrolls all patients for total knee implant procedures across the provider s nationwide facilities.

The primary role of the registry, Brox said, is to look at safety, quality and post-implant survival of the implant. The population was all TKR surgeries done in our facilities between 2001 and 2006.

That population totaled 13,250 women and 7,468 men.

Among complications studied, the researchers found there was no gender difference in deep infection rate and implant revision rate. Nor were the marked differences in range of motion between genders at greater than nine months follow-up.

And patient satisfaction between men and women was similar at greater than nine-month post-op, Brox said.

The conclusion, he said, was that we don t advocate use of gender-specific knee implants, which can run about $1,000 more than traditional unisex knees.

When I sit and talk with my patients, Brox said, I simply can t advocate spending $1,000 more for a gender-specific product.

Scott Sporer, MD, of Rush University Medical Center (Chicago), cited reports from an AAOS technology overview showing differences between male and female patients, including that men have larger femurs than women, that there are differences in the rotation of the trochlear groove in women, and that women have more laxity in their knee ligaments, along with a higher incidence of ACL injury, higher incidence of osteoporosis and osteoarthritis.

Can industry and physicians do better with development of knee implants? Yes, we can do better, Sporer said. The question is, If you change a variable [that is, add a gender-specific implant], is the outcome better?

Broader randomized studies are needed, he said, as well as outcome scales in order to measure subtle differences.