Total knee arthroplasty survivorship and outcomes in young patients: a review of the literature and 40-year update to a longitudinal study.

Introduction: Growing numbers of younger patients are electing to undergo total knee arthroplasty (TKA) for end-stage osteoarthritis. The purpose of this study was to compare established literature regarding TKA outcomes in patients under age 55, to data from an ongoing longitudinal young patient cohort curated by our study group. Further, we aimed to provide a novel update on survivorship at 40 years post-TKA from our longitudinal cohort.

Methods: A literature search was conducted using the electronic databases PubMed, Embase, and Cochrane Library, using terms related to TKA, patients under age 55, and osteoarthritis. Demographic and outcome data were extracted from all studies that met the inclusion criteria. Data were divided into the "longitudinal study (LS) group," and the "literature review (LR) group" based on the patient population of the study from which it came.

Results: After screening, 10 studies met the inclusion criteria; 6 studies comprised the LR group, and 4 studies comprised the LS group. 2613 TKAs were performed among the LR group, and 114 TKAs were longitudinally followed in the LS group. The mean patient ages of the LR and LS groups were 46.1 and 51, respectively. Mean follow-up was 10.1 years for the LR group. Mean postoperative range of motion was 113.6° and 114.5° for the LR and LS groups, respectively. All-cause survivorship reported at 10 years or less ranged from 90.6% to 99.0%. The LS cohort studies reported survivorship ranges of 70.1-70.6% and 52.1-65.3% at 30 and 40 years, respectively.

Conclusions: Young TKA patients demonstrated improved functionality at each follow-up time point assessed. Survivorship decreased with increasing lengths of follow-up, ultimately ranging from 52.1-65.3% at 40 years post-TKA. The paucity of literature on long-term TKA outcomes in this patient population reinforces the necessity of further research on this topic.