Abstract: Objective:To explore Clinical effects of low molecular weight heparin for preventing venous thromboembolism after posterior lumbar interbody fusion.Methods:68 patients from January 2015 to January 2017 who had undergone posterior lumbar interbody fusion by the same surgeon group were included in this study.According to the risk factors for deep vein thrombosis（DVT），patients can be divided into highrisk group（29 cases）and lowrisk group（39 cases）.The patients of VTE high risk group were given LMWH as a prophylaxis modality against VTE measures.Lower limb vascular doppler ultrasonography was used to monitor DVT preoperatively and postoperatively.The incidence of DVT in both groups was observed.and wound drainage，epidural and wound hematomas，and neural injury symptoms of the patients in the second group were studied.Results:DVT  incidence of the highrisk group was 3.4％（1/29），and this case was found DVT without symptom by Doppler Ultrasound 1mouth after surgery.There were no patients suffered from DVT in lowrisk group.There was no significant difference in amount of wound drainage between highrisk and lowrisk groups（P＞0.05）.No case caught epidural or wound hematoma，thrombocytopenia caused by low molecular heparin or nerve damage caused by extradural hemorrhage.〖WTHZ〗Conclusion:Individual DVT prophylaxis was taken According to the risk factors after PLIF.There are no complications from prophylaxis happened in two groups.Low molecular weight heparin for preventing venous thromboembolism after PLIF is effective and safe.

Key words: deep venous thrombosis, low molecular weight heparin, interbodyfusion