Patient-reported outcome measures in total joint arthroplasty: defining the optimal collection window

The purpose of this study was to determine the optimal window for collection of patient-reported outcome measures (PROMs) after total joint arthroplasty (TJA).

Our prospectively collected institutional joint registry was queried for patients who underwent primary, unilateral TJAs. The primary outcomes were the net changes in WOMAC, SF-12 MCS, SF-12 PCS, OHS, KSCRS, and UCLA activity rating system at 6, 12, and 24 months postoperatively. Secondary outcomes were data acquisition costs and follow-up attrition rates.

Eight hundred sixty-six procedures (450 total hip arthroplasties, 416 TKAs) were analyzed. A consistent plateau in all PROMs was noted by 6 months postoperatively-except for SF-12 MCS which showed no significant changes at any time interval. For TKA, the percentage of overall improvement achieved by 6 months was 88.7%, 84.5%, 100%, and 90.5% for the WOMAC, SF-12 PCS, UCLA, and KSCRS, respectively. For total hip arthroplasty, these values were 92.7%, 83.5%, 88.0%, and 89.8% for WOMAC, SF-12 PCS, UCLA, and OHS, respectively. There were marginal improvements from 6 to 12 months and no improvement from 12 to 24 months. Follow-up rates at 6, 12, and 24 months were 85%, 69%, and 40%, respectively. Our institutional costs for collecting a complete data set per patient were $128, $158, and $272 for 6, 12, and 24 months, respectively.

Most of the improvement in PROMs after primary TJA occurs within the first 6 months. In addition, limiting PROMs collection to 6 months appears to be cost-efficient owing to increased attrition rates beyond this time interval.