High pretreatment systemic immune-inflammation index values are associated with diminished short-term success after temporomandibular joint arthrocentesis procedure

Background: The systemic immune-inflammation index (SII) has been demonstrated to be a valid biomarker of a patient's immunological and inflammatory state, with the ability to accurately predict outcomes in a variety of disease conditions. In the absence of comparable studies, we intended to examine the relevance of pretreatment SII in predicting the success rates of temporomandibular joint arthrocentesis (TMJA) at 1-week, 1-month, and 6-month periods, defined as maximum mouth opening (MMO) > 35 mm and VAS ≤ 3. Methods: A sum of 136 patients with disc displacement without reduction (DDwo-red) who underwent TMJA was included. For each patient, pre-TMJA SII was calculated as; SII = Platelets × neutrophils/lymphocytes. Additionally, baseline MMO and VAS measurements were recorded for each patient. The success criteria of TMJA included MMO > 35 mm and VAS ≤ 3. The optimal pre-TMJA SII cutoff that predicts TMJA success was determined using receiver operating characteristic (ROC) curve analysis. The primary endpoint was the link between the pre-treatment SII and TMJA success (simultaneous achievement of MMO > 35 mm and VAS ≤ 3). Results: The median pre-TMJA jaw locking duration, maximum mouth opening (MMO), and visual analog score (VAS) were 7 days, 24 mm, and 8, respectively. The overall TMJA success rates were determined as 80.1%, 91.9%, and 69.1% at 1-week, 1-month, and 6-months, respectively. The results of ROC curve analysis exhibited the optimal SII cutoff at 526 (AUC: 67.4%; sensitivity: 66.7%; specificity: 64.2%) that grouped the patients into two subgroups: Group 1: SII ≤ 526 (N = 81) and SII > 526 (N = 55), respectively. Spearman correlation analysis revealed a strong inverse relationship between the pretreatment SII values and the success of TMJA 1-week (r_s: − 0.83; P = 0.008) and 1-month, (r_s: − 0.89; P = 0.03). Comparative analyses displayed that TMJA success rates at 1-week (87.7% vs. 69.1%; P = 0.008) and 1-month (96.2% vs. 80%; P = 0.03) were significantly higher in the SII ≤ 526 than SII > 526 group, respectively, while the 6-month results favored the SII ≤ 526 group with a trend approaching significance (P = 0.084). Conclusion: The current study's findings suggested the SII as a unique independent prognostic biomarker that accurately predicts treatment outcomes for up to 6 months. Trial registration The results of this research were retrospectively registered.