Older age at anterior cruciate ligament reconstruction associates with a lower systemic inflammation response index after surgery.

Abstract

The purpose of this study was to investigate the association of age at anterior cruciate ligament reconstruction (ACLR) with systemic indices of the immune system and inflammation after surgery. This study consisted of a retrospective, cohort design. Patients (male and female, ≥18 years) that underwent ACLR at a single academic institution and with complete blood cell (CBC) count data obtained ≥ 1-year after surgery were included. Patients with a documented diagnosis of knee osteoarthritis (OA) before ACLR were excluded, while those with a documented diagnosis of knee OA after ACLR were included in this study. The systemic inflammation response index (SIRI), systemic immune-inflammatory index (SII), neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and monocyte-to-lymphocyte ratio (MLR) were calculated from the CBC data. Patients (n = 198) were separated into groups based on age at ACLR: (1) 18-29 y (n = 96), (2) 30-39 y (n = 50), or (3) ≥40 y (n = 52). Subject characteristics (patient sex, height, body mass, and body mass index), follow-up interval, time from ACLR to CBC assessment, and concomitant procedures performed at ACLR were not significantly different between age groups. The PLR, NLR, MLR, and SII were not significantly different between groups, while the SIRI was significantly lower in the 30-39 (p < 0.01) and ≥40 y (p < 0.01) groups compared to the 18-29 y group. An older age at ACLR (i.e., 30-39 y and ≥40 y) was associated with an increased occurrence (11.5 and 12 %, respectively) of a knee OA diagnosis following surgery compared to that in the younger age group (18-29 y, 1.0 %; p = 0.04). We conclude that an older age at ACLR associated with a lower systemic inflammatory response index at a minimum of 1-year following surger. Level III.