A group of 417 total knee arthroplasties were assessed for clinical and radiographic follow-up at three institutions between August 1, 2006 and August 1, 2007. The primary purpose of this study was to analyze the weighted activity score for these patients and correlate these to objective and functional outcomes. The activity survey was utilized a cross-sectional assessment of patients who were returning for follow-up for a minimum of 12 months following TKA. All patients who enrolled in this study had Institutional Review Board approval from each center.
There were 162 men and 255 women who had a mean age of 69 years (range, 35 to 95 years). The group consisted of only patients with primary osteoar-thritis and excluded any patients with osteonecrosis or post-traumatic arthritis, rheumatoid arthritis or other diagnoses. Patients had a mean body mass index of 31 (range, 17 to 51). Patients were followed for a mean of 36 months (range, 12 to 116 months).
Patients were evaluated with a new weighted activity questionnaire which can be found in Appendix I. A previously reported questionnaire included a listing of activities, frequencies of the activity participation per week, month, and years, and a series of patient-related questions that had to do with activity level, competitiveness, and satisfaction.10
The activities were then given scores of 1 to 3 points based on a previous Knee Society survey. Activity scores were calculated using frequency times weighted points. The new weighted activity score utilizes all of these questions with some small modifications, but added further information concerning time of involvement per day. In addition, changes were made for the stratification of the sports on the 3-point scale to reflect recent recommendations based on impact level.12
provides the weighted score for each of the sports. Sports listed by the patient on their survey in the “Other” category were assigned a weighted score based on the surgeon assessment of impact level and whether they recommend the activity for their patients. Patients were administered pre- and post-operative activity questionnaires and the change in weighted activity score was determined for each patient.
Impact scores for each activity listed on the sports activity questionnaire
All the knees were evaluated using the Knee Society objective and functional scores.8
As previously noted, the activity questionnaire was also used to collect data concerning patient satisfaction using a Likert 10-point scale.13
Various demographic variables were collected for all of the patients which included age, gender, body mass index, Charnley class,14
as well as American Society of Anesthesiologists (ASA) classification.
All of the data for weighted activity scores, as well as demographic data and Knee Society objective and functional scores and satisfaction indices, were collected using a Microsoft Access Database (Microsoft Corporation, Seattle, Washington). Data was exported to SPSS version 13.0 software (SPSS Incorporated, Chicago, Illinois) for statistical analysis. An initial power analysis indicated our sample size was sufficient to answer our primary research questions at a power of 80% (alpha = 0.05) for an effect size of 0.2 for the correlation coefficients assessed. All correlations were assessed by Spearman's rank coefficient. Linear regression analysis was used to analyze the correlation of change in functional and objective outcomes and the corresponding change in weighted activity score. Based on initial survey results suggesting a large proportion of patients reporting no change in activity level, we re-assessed the linear correlations after excluding patients who had less than plus or minus one point change in their activity scores. In addition to evaluating the change in scores, we also compared the final outcomes based on post-operative Knee Society objective and function scores with the final weighted scores. In order to assess which demographic factors may have affected the weighted activity score as well as the functional and objective outcomes, we conducted a stepwise regression analysis including age, gender, BMI, Charnley class, and ASA classification as potential predictors of change in activity and final activity scores. Additionally, the data was stratified by each of these variables and a Chi-square analysis was used to compare the proportions of patients who had a decrease in activity level, no change, or an increase in activity level.