New total knee arthroplasty designs: do young patients notice?

Although the volume of total knee arthroplasties (TKAs) performed in the United States continues to increase, recent reports have shown the percentage of patients who remain "unsatisfied" is as high as 15% to 30%. Recently, several newer implant designs have been developed to potentially improve patient outcomes.

The purpose of this study was to determine the impact of high-flex, gender-specific, and rotating-platform TKA designs on patient satisfaction and functional outcomes.

A four-center study was designed to quantify the degree of residual symptoms and functional deficits in patients undergoing TKA with newer implant designs compared with a 10-year-old, cruciate-retaining (CR) TKA system introduced in 2003. Each contributing surgeon was fellowship-trained and specialized in joint replacement surgery. Only patients younger than 60 years old were included. Data were collected by an independent, third-party survey center blinded to the implant type, who administered questionnaires about patient satisfaction, residual symptoms, function, and pre- and postoperative activity levels using previously published survey instruments. Two hundred thirty-seven CR, 137 rotating-platform, 88 gender-specific, and 65 high-flex TKAs were included in the analysis. Differences in baseline demographic variables were accounted for using multiple logistic regression statistical analyses.

Patients who received certain newer designs reported more residual symptoms (grinding, popping, and clicking) in the 30 days before survey administration than the group receiving a 10-year-old CR design (CR, 24% [57 of 237 patients] versus gender-specific, 36% [32 of 88 patients]; odds ratio [OR], 2.1; 95% confidence interval [CI], 1.1-3.8; p=0.03; and rotating-platform, 43% [59 of 137 patients]; OR, 2.2; 95% CI, 1.3-3.7; p<0.001). They also reported more functional problems, including getting in and out of a chair (CR, 19% [46 of 237 patients] versus gender-specific, 37% [32 of 88 patients]; OR, 1.0; 95% CI, 1.1-3.5; p=0.001). Patients with newer TKA designs did not demonstrate any improvements in function or patient satisfaction versus those who received the 10-year-old CR design.

When interviewed by an independent, blinded third party, the use of newer implant designs did not improve patient satisfaction and the presence of residual symptoms when compared with patients who received the 10-year-old CR design. Future studies should prospectively determine whether the purported benefits of newer implant designs improve patient-perceived outcomes.

Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.