Venous thromboembolism prophylaxis after ambulatory arthroscopic knee surgery: a systematic review and meta-analysis of incidence and risk factors (109)

OBJECTIVES: Over 100,000 anterior cruciate ligament (ACL) reconstructions are performed in the United States annually, yet the reported incidence of venous thromboembolism (VTE) and the use of VTE thromboprophylaxis after ACL reconstruction and other arthroscopic knee surgeries still varies widely. Current VTE risk assessment scores, for example the Caprini score, incorporate arthroscopic surgery as a known risk factor but were not developed for stratification of an outpatient ambulatory surgical patient population. There is no current consensus to guide the orthopedic surgeon in prescribing chemoprophylactic agents after arthroscopic knee surgery. The objectives of this study were to determine the incidence, efficacy, and risk factors for VTE specifically following knee arthroscopic procedures. The null hypotheses of this study was that previously defined risk factors for VTE after ambulatory knee arthroscopy (age over 60 years, BMI greater than 30 kg/m(2), tobacco use, prior VTE, malignancy, coagulopathy, oral contraceptive use, family history of coagulopathy, and prolonged tourniquet time greater than 90 minutes) would not reach statistical significance when compared across multiple cohorts. Our hypothesis is that a systematic review and meta-analysis of these variables will reject the null hypotheses with a significance of level of p < .05. METHODS: A systematic review and meta-analysis was performed using data collected from 30 cohort and therapeutic trials (721,005 patients) published between January 2000 and April 2020 to compare both the incidence of deep vein thrombosis (DVT) and/or pulmonary embolism (PE) and associated risk factors after knee arthroscopy with or without thromboprophylaxis in adults. Ultrasound, venography, and International Classification of Diseases, 10(th) Revision (ICD-10) diagnosis codes were deemed acceptable detection methods for VTE. We also performed a meta-analysis of published patient characteristics and risk factors in developing VTE after arthroscopic knee procedures. Individual studies were not evaluated for symptomatic versus asymptomatic VTE detection criteria or methods. RESULTS: Of 331 eligible articles, 6 therapeutic RCTs and 24 cohort studies met the inclusion criteria. Overall incidence of DVT and PE was found to be 0.97% and 0.03% respectively. Analysis of the RCTs was found to support the use of prophylactic anticoagulation in preventing DVTs (relative risk: 0.24, 95% confidence interval [CI]: 0.13-0.44). After analysis of the cohort studies, age greater than 60 years was found to be a statistically significant risk factor for VTE (OR: 1.84, 95% CI: 1.03 – 3.29; p=.04) while a history of malignancy (OR: 2.61, 95% CI: 0.97 – 7.00; p=.06), and history of previous VTE (OR: 4.14, 95% CI: 0.90 – 19.14, p=.07) trended toward significance. Other factors such as BMI greater than 30 kg/m(2), tobacco use, tourniquet time, personal or family history of coagulopathy, and oral contraceptive use were not found to be statistically significant risk factors for VTE after knee arthroscopy, however there were limited studies (one to three studies per risk factor) available to distinguish of a majority of these variables. CONCLUSIONS: Our results show that the overall incidence of DVT in adults after arthroscopic knee surgery is approaching 1% and that of PE is exceedingly rare, however this may be underestimated if asymptomatic VTE is not identified. Despite a low incidence of VTE after knee arthroscopy, thromboprophylaxis is effective in preventing VTE and trends in risk factors exist in ambulatory sports medicine patients diagnosed with VTE post-operatively. The risk for adverse bleeding events while taking chemoprophylaxis and requires further research. Only rejection of the null hypothesis on age over 60 years was statistically significant, however other defined risk factors may be clinically significant. With these results, we conclude that a preoperative assessment may be warranted in identifying at-risk, high risk, or multi-risk patients for which prophylactic anticoagulation postoperatively after knee arthroscopic procedures may be beneficial. A modified version of the Caprini score specifically stratifying these risk factors in an ambulatory sports medicine population may be valuable to the practicing orthopedic arthroscopic surgeon. More research is warranted for identifying risk factors to better stratify this unique patient population.