Predicting pain and function with the neutrophil-to-lymphocyte ratio in patients following primary reverse total shoulder arthroplasty

Background: Glenohumeral joint osteoarthritis is prevalent in the middle-aged and elderly population, affecting approximately 16%-20% of individuals. Total shoulder arthroplasty has become a common treatment for osteoarthritis, with a notable rise in the use of reverse total shoulder arthroplasty (rTSA) over the past decade. Despite improvements in surgical technique and prostheses, 22% of patients continue to experience chronic pain following shoulder arthroplasty. Currently, medical practitioners lack a reliable method for identifying which patients will suffer from persistent pain and functional limitations after surgery. In this context, the neutrophil-to-lymphocyte ratio (NLR), known for measuring immune-inflammatory reactions and neuroendocrine stress, has gained significant attention. Therefore, the purpose of this study was to explore the predictive potential of the NLR in identifying patients who will experience elevated pain and functional limitations after primary rTSA. Methods: This study was a retrospective cohort design. Patient data were collected retrospectively between 2019 and 2021 and grouped based on preoperative NLR (≥2.5 and <2.5). Primary outcome measures assessed were the American Shoulder and Elbow Surgeons (ASES) score, visual analog scale (VAS), Pittsburgh Sleep Quality Index, and Single Assessment Numeric Evaluation score. Secondary outcomes included active shoulder elevation and external rotation range of motion. Outcome measures were captured before surgery and at 6 and 12 months after surgery. Results: At 6 months following surgery, patients with an NLR ≥2.5 scored significantly worse on the VAS (P = .0171), ASES (P = .0015), and Single Assessment Numeric Evaluation (P = .0226). Differences in Pittsburgh Sleep Quality Index scores were not significant (P = .2705). Forward elevation and external rotation range of motion were similar between groups at 6 months (P = .7777 and P = .2630, respectively). There was no statistically significant difference between groups at 12 months across all variables. Multivariate analysis showed that an NLR <2.5 had a significant positive effect on the ASES score (P = .0011) at 6 months after adjusting for age, gender, body mass index, depression, low back pain, and diabetes. Conclusions: Management of patients with chronic pain continues to be challenging with limited high-value interventions. Early identification of patients likely to have a protracted recovery following rTSA would allow for a multidisciplinary approach earlier in the recovery phase. Based on our results, patients who had a preoperative NLR value greater than 2.5 reported higher levels of pain, more functional limitations, and perceived poorer function at 6 months following rTSA. However, these effects were relatively small and not observed at the 12-month mark.