Validity of preoperative demand matching as an indicator of activity after TKA.

We questioned whether our current preoperative demand matching accurately predicted patient activity after TKA. From a prospective database we reviewed 511 patients who had unilateral, primary TKA from 1994 to 1999 and who were preoperatively assessed for five patient characteristics: age, weight, expected postoperative activity, health status, and bone stock. We assigned each knee to one of four demand categories. Knee implant selection was based on the patient's demand category. Other preoperative patient characteristics that could be associated with postoperative activity were recorded. The reported postoperative patient activity after TKA was determined, and was correlated with each patient variable and the demand category. Five hundred eleven TKAs were distributed among four demand categories: 39 (7.6%) demand I (high); 156 (30.5%) demand II; 294 (57.5%) demand III; and 22 (4.3%) demand IV (low). Age, gender, expected postoperative activity, bone stock, health status, preoperative activity, Knee Society Function Score, and the Hospital for Special Surgery Knee Score correlated with postoperative patient activity. The demand category was more predictive than any individual variable. The data suggest preoperative demand matching a valid approach to predict patient reported activity after TKA. Because patient activity is correlated with wear, implant selection and resource allocation can be targeted to those patients who may benefit from presumed improvements in implant technology.