# Antiphospholipid Syndrome in Orthopaedic Foot and Ankle Surgery: A Propensity-Matched Analysis

## TL;DR

This study examines how antiphospholipid syndrome affects outcomes after foot and ankle surgery, finding higher blood clot risks and lower anemia rates in patients receiving anticoagulation.

## Contribution

The study provides new insights into postoperative outcomes for APS patients in orthopedic surgery, highlighting differential risks with and without anticoagulation.

## Key findings

- APS patients receiving VTE prophylaxis had higher deep vein thrombosis rates but lower anemia rates compared to controls.
- APS patients without anticoagulation had higher pulmonary embolism rates than controls.
- Anticoagulation-naïve APS patients showed significantly altered preoperative lab values compared to controls.

## Abstract

Antiphospholipid syndrome (APS) is a systemic autoimmune disorder associated with a heightened risk of thromboembolic events. The purpose of this study is to evaluate the impact of APS on medical and surgical postoperative outcomes following foot and ankle surgery.

Using the TriNetX Research Network, we identified patients undergoing foot and ankle surgery between 2004 and 2024. APS patients with and without postoperative venous thromboembolism (VTE) prophylaxis were matched 1:1 with controls based on demographics and comorbidities. Outcomes within 30 and 90 days postoperatively were compared, including thromboembolic events. Preoperative laboratory test values were also assessed in a subset of APS patients not on anticoagulation.

At 90 days postoperatively, APS patients receiving VTE prophylaxis (APS+VTE) (n = 524) had significantly higher rates of deep vein thrombosis (13.4% vs 9.0%, P = .024), but similar rates of stroke and pulmonary embolism compared to patients without APS receiving VTE prophylaxis (Control+VTE). Anemia was significantly less common in the APS+VTE group at 30 days (14.7% vs 22.3%, P = .001) and 90 days (16.4% vs 23.9%, P = .003). APS patients without postoperative anticoagulation (APS–VTE) (n = 932) had a higher rate of pulmonary embolism at 90 days (5.8% vs 3.3%, P = .011) compared to patients without APS and VTE prophylaxis (Control–VTE). Anticoagulation-naïve APS patients demonstrated significantly higher preoperative International Normalized Ratio (1.64 vs 1.09, P < .001), prothrombin time (17.7 vs 12.3, P < .001), activated partial thromboplastin time (38.6 vs 29.2, P < .001), serum creatinine (1.08 vs 0.94, P < .001), estimated dry weight (14.3 vs 13.7, P < .001), along with urea nitrogen (17.0 vs 15.9, P < .001), sodium (139.13 vs 139.25, P = .001), potassium (4.14 vs 4.10, P = .012), and bicarbonate (26.2 vs 25.8, P < .001) compared with matched controls.

APS patients undergoing foot and ankle surgery had significantly higher thromboembolic event rates than controls, even with anticoagulation, and those who received anticoagulation had lower anemia rates, suggesting differential bleeding risk.

Level III, retrospective cohort study.