Clinical Predictors of the Forgotten Joint Score 12 in Total Knee Arthroplasty.

Abstract

Background: Patient-reported outcomes (PRO) have become a key criterion for determining patient satisfaction following orthopaedic procedures like total knee arthroplasty (TKA). The Forgotten Joint Score 12 (FJS-12) is designed to evaluate if a patient is aware of their replaced joint. Little literature exists surrounding the predictive power of other metrics on the FJS-12. In this paper, differences in these clinical metrics were assessed between groups of patients who scored above the FJS-12 cutoff and those who did not after TKA.

Methods: Patients who underwent primary elective TKA and answered all required PROs during the designated study period were included. Using an established cutoff of 33.3, patients were put in a "Forgotten Joint Group" or a "Remembered Joint Group." This study included 672 patients who fit the criteria. Of these, 508 (76%) forgot their joints and 164 (24%) remembered their joints at twelve months. Differences in clinical metrics between the two groups were assessed for significance using univariate analyses (t-test, Chi-square, Fisher's Exact). Receiver operating characteristic (ROC) curve analysis was then used to determine the predictive value of metrics that showed these significant differences.

Results: Early results from the Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS-JR) and Numeric Pain Scale (NPS) were strongly correlative of the twelve-month FJS-12 score, rather than patient demographics. Patients who scored above 65.1 or 72.1 on the KOOS-JR three and six months after surgery, respectively, or below a 3 on the NPS three and/or six months after surgery were also favored to forget their replaced joint at twelve months.

Conclusion: Identifying predictors of the FJS-12 allows for the recognition of at-risk patients before the twelve-month time point, facilitating earlier intervention and improving care after surgery. The scope of this analysis may be broadened in the future to include other arthroplasty procedures, such as for the hip and shoulder.