Incidence of venous thromboembolism in fracture below the knee with and without chemical thromboprophylaxis: a systematic review and meta-analysis

Introduction: Low rates of venous thromboembolism (VTE) have been found in patients with isolated orthopaedic trauma below the knee. Many surgeons routinely provide chemical thromboprophylaxis in these injuries, however. This is not without inherent risks, and this remains a controversial topic in perioperative care in orthopaedic trauma. This systematic review and meta-analysis was performed to look at rates of VTE in patients with isolated orthopaedic fractures below the knee, grouped by whether they received chemical prophylaxis versus no chemical prophylaxis.

Methods: A systematic review was performed comparing VTE with and without chemical thromboprophylaxis following isolated orthopaedic fracture below the knee. A chi-square analysis was then performed on data including patients who received chemical prophylaxis versus those who did not from all 25 included articles. The articles were grouped according to type of study, such as observational versus randomized controlled trial (RCT), and then further subdivided according to surgical intervention status, and whether routine screening for thromboembolism was utilized to diagnose. Risk of bias assessment was performed using the ROBINS-I criteria for cohort studies and the Cochrane RoB 2 tool for randomized controlled trials. A random effects pooled logistic regression and Fisher's exact tests were then performed.

Results: 222,188 patients were found from 25 articles. Chemical prophylaxis was given to 8,666 patients, and VTE was reported in 347 cases (4.0%). 213,522 patients did not receive chemical prophylaxis, and VTE was reported in 2,185 (1.02%) (χ² (1, n = 222,188) = 656.8, p < .00001). Pooled logistic regression revealed that patients receiving prophylaxis were 0.5 times less likely to develop VTE. With a calculated population baseline risk of 1.5% for developing VTE, the number needed to treat (NNT) with chemical prophylaxis is 134 to prevent 1 VTE after fracture below the knee.

Conclusions: In patients with isolated orthopaedic trauma below the knee, indiscriminate use of chemical VTE prophylaxis is not recommended due to the lack of significant benefit and high NNT.

Level of evidence: Level III.