Knee Implants Designed for Women May Not Improve Outcomes

Anatomic differences between the knees of men and women have resulted in the creation and regular use of gender-specific implants. However, a study presented at the AAOS 2013 annual meeting found that a specialized prosthesis may not improve overall outcomes in women total knee replacement (TKR) patients.

"While female knees are often more narrow with larger valgus angles, it is unknown whether changes to the femoral prosthesis leads to improved outcomes," explained study authors Alexander P. Sah, MD, and John T. Dearborn, MD, from Freemont, California. These knee components are used frequently in TKR procedures in women, who represent 60% of all TKR patients.

In their study, the researchers evaluated 1957 TKRs between 2006 and 2010 in women with 1515 (77.4%) using female specific implants, compared with 771 TKRs from 2002 to 2006 prior to the availability of the gender component. Radiographs were reviewed for component fit, and clinical outcomes.

While there was less overhang of the knee implant with use of the female-specific prosthesis, improvements in patient knee range of motion, knee flexion, lateral release rates, and pain scores were comparable in each of the two groups. Specifically, lateral releases in gender-specific knees was 102 out of 1515 (6.7%), compared with 58 out of 1007 (5.8%) for flex knees. Furthermore, the authors found that radiographic evaluation of patellar tracking was similar between both groups.

"While we certainly use [the female components] frequently [in surgery], we don't detect any objective improvement in clinical outcomes, including pain scores and range of motion," Sah stated. "At the same time, there was no detectable disadvantage of using the implant, such as increased blood loss or component migration.

"Benefits of using the gender-specific component may not be detectable by current measures, or may not exist at all. However, the additional size option definitely provides the surgeon with more flexibility during surgery and that is useful."