Zimmer (Warsaw, Indiana) focuses its gender-related hip research on what it says are three differences between male and female hips: femoral head center location, femoral canal shape and femoral canal size.

“Femoral head center location” is important, the company says, because traditional implants often don’t easily accommodate the shorter head heights and offsets in women. This increases surgical complexity, raising the risk of leg length discrepancy, impingement, and dislocation, it says.

Zimmer says its Gender Solutions M/L Taper Stem with Kinectiv Technology is designed to address the issues of offsets, head height and ante-version independently, such that an adjustment to one does not affect the others, offering the surgeon greater options in addressing specific patient anatomies.

“Canal shape” is important, it says, because many females have greater variation between the proximal and distal width of the femoral canal. This mismatch, it says, creates a “stove pipe” effect that forces the surgeon to use a larger diameter implant that also has more head height and more offset, “a common design philosophy in many of today’s implants. As a result, patients may suffer leg length discrepancies that hamper the restoration of proper joint kinematics.”

And it points to patient satisfaction research indicating that maintaining proper leg length is especially important for women compared to men. Thus, it says it is developing a gender-specific hip stem incorporating its Epoch composite hip technology “to address femoral canal size and shape differences.

“Because stems utilizing Epoch technology are made from medical grade PEEK, they are more flexible than traditional implants, the company said. Zimmer said it believes the reduced bending stiffness can be helpful in situations where more “canal fill” is needed but a large metal stem could pose stress shielding risks.