Radiolucent Lines Do Not Affect Short-term Outcomes of a Novel Fixed-bearing Cementless Total Knee Arthroplasty System

Background: Cementless total knee arthroplasty (TKA) is becoming increasingly common, and new systems warrant continued investigation. In this study, early functional and patient-reported outcome measures (PROMs) were investigated as they relate to the presence of radiolucent lines (RLL) in patients who underwent TKA using a novel cementless fixed-bearing system. Materials and Methods: An institutional database was retrospectively reviewed from November 1, 2022, to April 1, 2024, for primary TKA patients using a novel cementless TKA system. Demographics, range of motion, alignment, PROMs, and radiographs were collected and summarized for the cohort. Postoperative bone length, anteroposterior, and lateral weight-bearing–calibrated radiographs were evaluated for the presence of RLL by two reviewers. Patients were subsequently stratified by presence of RLL, and their functional and PROMs were compared. Results: A total of 262 TKAs were performed by a single surgeon during the study period. Of these, 36 (13.7%) patients met inclusion criteria. Median Patient-Reported Outcomes Measurement Information System pain interference, physical function, and depression scores, as well as Knee Injury and Osteoarthritis Outcome Score, Joint Replacement, scores all improved 1 year postoperatively compared to preoperatively. Cohen's kappa was 0.34, indicating fair agreement between reviewers in radiographic analysis of RLL. Agreement was greatest for zones 1, 4, 10, 11, and 12. In total, there was at least one RLL detected by both reviewers in the same zone in 66.7% of knees, most commonly in zone 1. Lines were all <2 mm in depth, and no cases of aseptic loosening or revisions were noted. Conclusion: Our results showed that this novel cementless system is a viable option for cementless TKA. Although RLL were present in the majority of patients in our cohort, all lines were <2 mm in depth and there were no cases of loosening or needing revision surgery. As expected, all PROMs improved at 1 year postoperatively. Further research is needed to investigate the mid- and long-term outcomes of this implant.