Table 1 Predictors of venous thromboembolism after foot and ankle fracture surgery
Source: Brennan JC, et al., “A Predictive Model for Identifying Patients at Risk for Venous Thromboembolism after Foot and Ankle Fracture Surgery.”

AAOS Now

Published 3/25/2022
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Brandon May

Advanced Age and Bleeding Disorders Predict VTE Risk after Foot and Ankle Fracture Surgery

Advanced age and bleeding disorders are independent risk factors for venous thromboembolism (VTE) following foot and ankle fracture surgery, a study suggests. The findings of the study will be presented by Jane Brennan, orthopaedic clinical outcomes research analyst at Anne Arundel Medical Center in Mountain Lakes, N.J.

According to Ms. Brennan and colleagues, the study is potentially the first piece of research to produce and test a model that identifies patients at risk for VTE following fracture surgery. The researchers explained that a predictive model that incorporates age and bleeding disorders may help surgeons prospectively in their ability to identify high-risk patients who may require pharmacologic VTE prophylaxis.

VTE, including deep vein thrombosis and pulmonary embolism, is a rare yet serious complication following foot and ankle fracture surgery. Although prior studies have identified various risk factors for VTE, the researchers acknowledged, a consensus definition for high-risk patients has not yet been established, consequently resulting in “significant variability in the use of pharmacologic agents for VTE prophylaxis.”

To improve prevention efforts in this population, the researchers sought to develop and test a usable and scalable model capable of predicting VTE risk in patients who undergo foot and ankle fracture surgery.

The study was a retrospective review of patients (n = 15,342) from the American College of Surgeons National Surgical Quality Improvement Program database who underwent surgical repair of foot and ankle fractures between 2015 and 2019. Bimalleolar, calcaneal, talus, distal tibia, and trimalleolar fractures were included.

The investigators examined the prevalence and demographics associated with corticosteroid use, current bleeding disorders, diabetes, dyspnea, independent functional status, history of chronic obstructive pulmonary disease (COPD), history of congestive heart failure (CHF), disseminated cancer, smoking status, and infection at the time of surgery. The surgeries performed were classified as either bimalleolar/talus/calcaneal fracture repairs or trimalleolar/distal tibia repairs.

Demographic and comorbidity differences between patients who experienced postoperative VTE versus patients who did not experience postoperative VTE were assessed in a univariate analysis. The investigators also divided the cohort into a development group (60 percent) and test cohort (40 percent). After the univariate analysis, risk factors for VTE were evaluated in a multivariate logistic regression.

The investigators then produced a model that incorporated demographics and comorbidities and tested its performance in the test cohort. To investigate the accuracy of the model in predicting VTE within 30 days after operation, the investigators generated a receiver operator curve and calculated the area under the curve (AUC).

In the overall cohort, 1.2 percent (n = 184) of patients experienced VTE. Approximately 52.7 percent of patients with VTE were aged 65 years or older, compared with 25.8 percent of patients who did not experience VTE (P <0.001). additionally, patients who had vte had a significantly higher comorbidity burden, evident by greater rates of diabetes (36.4 percent versus. 13.0 percent,>P <0.001), dyspnea (16.9 percent versus 2.9 percent,>P <0.001), history of copd (17.4 percent versus 3.8 percent,>P <0.001), history of chf (7.7 percent versus 0.7 percent,>P <0.001), infection at the time of surgery (15.2 percent versus 3.3 percent,>P <0.001), corticosteroid use (5.4 percent versus 2.0 percent,>P = 0.004), and bleeding disorders (16.8 percent versus 3.5 percent, P <0.001), as well as lower levels of independent functional status (82.6 percent versus 95.4 percent,>P <0.001).>

The researchers noted that, in contrast to previous studies, this study found that smokers had lower rates of VTE (16.8 percent versus 24.3 percent, P = 0.023). There were no significant differences between the VTE and non-VTE groups in terms of types of surgeries performed (P = 0.456). Patients who had VTE after surgery had 10.5 more minutes in the OR compared with patients who did not experience VTE (P = 0.029).

Following risk adjustment, the investigators identified two independent risk factors for postoperative VTE: age 65 years and older (adjusted odds ratio [OR] = 2.08, P = 0.041) and bleeding disorders (OR = 7.24, P = 0.015) (Table 1). The model, when applied to the test cohort, generated an AUC of 0.710, which the researchers stated was indicative of the model’s predictive accuracy.

Given the study finding that older age and bleeding disorders independently increased the risk for VTE after foot and ankle fracture surgery, the authors concluded, “Utilization of this model may help surgeons prospectively identify high-risk patients who may benefit from pharmacologic VTE prophylaxis.”

The study will be on display as Poster P0658 on Friday in Academy Hall from 7 a.m. to 5 p.m.

Ms. Brennan’s coauthors of “A Predictive Model for Identifying Patients at Risk for Venous Thromboembolism after Foot and Ankle Fracture Surgery” are Edward S. Holt, MD, and Justin Turcotte, PhD.

Brandon May is a freelance writer for AAOS Now.