Background: The risk of venous thromboembolic events (VTE) increases in patients undergoing total shoulder arthroplasty (TSA). However, there is no guidelines for prophylaxis. A decreased ratio of ADAMTS13 to VWF has been reported in patients with VTE. This study evaluates how TSA affects this ratio to better characterize timing of VTE risk and develop better guidelines for prophylactic treatment. Methods: Patients receiving TSA between 2016 and 2019 were recruited for this study following informed consent. Blood samples were collected at the clinic visit prior to surgery, postoperatively within one hour, at 24 h, 48 h, 2 and 6 weeks. Plasma levels of ADAMTS13 activity and VWF antigen were determined with a FRETS-VWF73 and an enzyme-linked immunoassay, respectively. Results: Of 22 patients included in the study, the mean age (± SD) was 68 ± 11 years. The most common diagnosis and surgery were osteoarthritis (68%) and reverse TSA (77%), respectively. Plasma ADAMTS13 activity was reduced immediately following surgery and remained lower than the baseline until postoperative day 2 (POD-2) (93.7 ± 28.5 IU/dL, p = 0.009). VWF antigen was the highest on POD-2 (253.2 ± 101.0%, p = 0.0034). The ADAMTS13/VWF ratio followed the same pattern, lowest on POD-2 (0.41 ± 0.20, p = 0.0016). All levels returned to baseline by two weeks. Conclusions: TSA resulted in low ADAMTS13 activity and high VWF acutely post-surgery day 2, suggesting that risk for VTE may be the highest during this period. ADAMTS13/VWF ratio is a useful marker to identify patients who may need proper anticoagulation after TSA.
Keywords: ADAMTS13; arthroplasty; surgery; von Willebrand factor.