The Issue is Gender Anatomy
The DePuy Response
"Our data doesn't really support that women need a different implant than a man."*
"There is no clinical support showing the need for a female-specific knee replacement implant."†
The Biomet Response
Biomet does not believe the differences between male and female anatomies are great enough to warrant a different product design.‡
The Scientific Evidence
Numerous scientific studies have concluded that there are significant differences between male and female knees.1-10 We believe that the three most important differences are:
- The prominence of the anterior condyles
- The Q-Angle
- The M/L-to-A/P aspect ratio of the femur
Some investigators call for manufacturers to design knee implants with distinct geometries to fit female and male knees.1
An Example
Surgeons sometimes must perform intraoperative adjustments to make a traditional implant fit the anatomy of a female patient.4 For example, when faced with the problem of M/L overhang of the femoral component, it is not uncommon for surgeons to downsize.4 With most knee systems, downsizing changes the A/P dimension of the implant, which could have an unintended impact on joint kinematics. Downsizing requires recutting the femur, which can increase total surgery time, as well as increase the risk of notching the anterior cortex for posterior referencing surgeons, or loosening the flexion space for anterior referencing surgeons.4
1. Hitt K, Shurman II J, Greene K, et al.
Anthropometric measurements of the human knee: correlation to the sizing of
current knee arthroplasty systems. J Bone Joint Surg.
2003;85:115-122.
2. Poilvache PL, Insall JN, Scuderi GR, Font-Rodriguez DE. Rotational landmarks and sizing of the distal femur in total knee arthroplasty. Clin Orthop. 1996;331:35-46.
3. Vaidya SV, Ranawat CS, Aroojis A, Laud NS. Anthropometric measurements to design total knee prostheses for the Indian population. J Arthroplasty. 2000;15(1):79-85.
4. Chin KR, Dalury DF, Zurakowski D, Scott RD. Intraoperative measurements of male and female distal femurs during primary total knee arthroplasty. J Knee Surg. 2002;15(4):213-217.
5. Mahfouz M, Booth R Jr, Argenson, J, Merkl, BC, Abdel Fatah EE, Kuhn MJ. Analysis of variation of adult femora using sex specific statistical atlases. Presented at: Computer Methods in Biomechanics and Biomedical Engineering Conference; 2006.
6. Aglietti P, Insall JN, Cerulli G. Patellar pain and incongruence. I: measurements of incongruence. Clin Orthop. 1983;176:217-224.
7. Hsu RWW, Himeno S, Coventry MB, Chao EYS. Normal axial alignment of the lower extremity and load-bearing distribution at the knee. Clin Orthop. 1990;255:215-227.
8. Woodland LH, Francis RS. Parameters and comparisons of the quadriceps angle of collegeaged men and women in the supine and standing positions. American Journal of Sports Medicine. 1992;20(2):208-211.
9. Livingston LA. The quadriceps angle: a review of the literature. J Orthop Sports Phys Ther. 1998;28(2):105-109.
10. Csintalan RP, Schulz MM, Woo J, McMahon PJ, Lee TQ. Gender differences in patellofemoral joint biomechanics. Clin Orthop. September 2002;402:260-269.* Monika Gibson, DePuy spokeswoman. As reported by Reuters. March 22, 2006. Orthopedic companies seek to woo women with new knee implant. by Debra Sherman.
* Monika Gibson, DePuy spokeswoman. As reported by Reuters. March 22, 2006. Orthopedic companies seek to woo women with new knee implant. by Debra Sherman.
†KneeReplacement.com. Women and Knee Replacement. Women's Resource Center. Gender Specific Knees: Frequently Asked Questions. Available at: www.kneereplacement.com
‡Dane Miller, former CEO, Biomet. As reported by Reuters. March 22, 2006. Orthopedic companies seek to woo women with new knee implant. by Debra Sherman.
