Total Knee Sizing FAQ's

Gender differentiated knee implant design is a new trend in Orthopaedics. Throughout the marketplace it is believed there are three main disparities between men and women relating to implant design:

women have a greater trochlear groove angle
women have a narrower distal femur
women are more prone to anterior overstuffing.

Review the differences below to learn if there is a stature difference or a gender difference. Several of the studies demonstrating an anatomic difference between men and women⁷⁷ have not taken into account the physical stature of individuals. Those studies that have examined other factors besides gender have found that stature patient size is more of a determinant of implant needs than gender.

Dispelling Myth #1 “Women have a greater trochlear groove angle”
Studies have shown the Q-angle is not different due to gender, but is actually dependent on the height of the individual. If a man and a woman of equal height were measured, their Q-angle would be the same. Studies showing a gender difference have not recognized that men are taller than women on average. They simply separate the sample by gender; not stature. Other studies have shown that there is no difference in the morphologies of the trochlear grooves of male and female fetuses and do not change in adulthood^{78, 79}. Differences are due to stature.

Dispelling Myth #2 “Women have a narrower distal femur”
One of the most referenced studies on gender sizing was performed by Kirby Hitt, MD. The study illustrates that most knee components were 5mm too wide for the female population. However, this study did not examine other factors such as patient height. The fact is some men need narrow implants as well. Differences are due to stature.

Dispelling Myth #3 “Women are more prone to anterior overstuffing”
Due to stature differences, it is common for the female patella to be thinner than the male. Once again, studies have found this is not due to gender, but are due to the differences in average height between men and women. Differences are due to stature.

Solution: ADVANCE STATURE™
The ADVANCE STATURE™ femoral component provides the same tried and true features and the regular ADVANCE® implants with some distinct sizing advantages for patients that need a narrower implant than the standard size. The components utilize the same ADVANCE® trochlear groove angle that replicates the sulcus morphology of both males and females⁸⁰. Furthermore, the trochlear groove has demonstrated excellent clinical results regardless of gender. The M/L dimension has been reduced by 5mm from the standard ADVANCE® Knee. In addition, the anterior flange has been contoured to resist anterior overstuffing.