Prospective clinical trial analyzing serum mast cell tryptase levels and arthrofibrosis rates after total knee arthroplasty.

Aims: Arthrofibrosis affects a notable percentage of patients after total knee arthroplasty (TKA). Elevated serum mast cell tryptase (SMCT) levels have been linked to fibrosis, suggesting that SMCT could serve as a biomarker for arthrofibrosis. As such, the aims of this study were to assess SMCT levels in TKA patients, and their possible association with arthrofibrosis and clinical outcomes in a prospective clinical trial. Methods: We conducted a prospective study involving 219 patients undergoing primary TKA at a single academic medical centre between January 2018 and December 2022. SMCT levels were measured preoperatively, immediately postoperatively, and at six weeks, three months, and one year postoperatively. Secondary outcomes included revision rates, complications, and Knee Society Scores (KSSs). Allergic and inflammatory conditions were assessed for their influence on SMCT levels. Results: At one year postoperatively, eight patients had developed arthrofibrosis (4%), and three (1.5%) had undergone manipulation under anaesthesia. The mean preoperative SMCT level was 5.6 µg/L (SD 3.4), which decreased significantly to 4.1 µg/L (SD 2.7) immediately postoperatively (p < 0.001). At six weeks the mean SMCT level was 6.4 µg/l (SD 4.1), and was 6.1 µg/l at both three months (SD 4.1) and one year (SD 4.0). Elevated preoperative SMCT levels were not significantly associated with the risk of arthrofibrosis development (OR 3; p = 0.370), nor were immediate postoperative levels (OR 2; p = 0.754) or those at six weeks (OR 1; p = 0.989). Of note, elevated SMCT levels at three months (OR 5; 95% CI 0.4 to 64; p = 0.191) and one year (OR 13; 95% CI 1 to 232; p = 0.077) trended toward an increased risk of arthrofibrosis development, without reaching significance. Conclusion: In patients undergoing TKA, with the numbers included in this study, there was no significant difference in SMCT levels between patients who did and did not develop arthrofibrosis at any timepoint. However, there was a trend towards elevated SMCT levels at three months and one year in those who developed arthrofibrosis, which merits further study.