In recent years, many literatures have reported the incidence of perioperative DVT in fracture patients, and there are differences in the incidence of DVT in different regions, races and populations.The incidence of VTE after total knee arthroplasty was 20.67% in the United States after aspirin and barotherapy with multimodal prophylaxis[3].Yukizawa,s prospective, single-center study reported that the preoperative and postoperative VTE rates of 419 total hip replacement patients in Japan were 11.4% and 10.5%, respectively[4].However,a retrospective study of 1825 lower limb fractures in China found that the preoperative and postoperative DVT rates were 30.0% and 43.4%, respectively[5].The results showed that the incidence of DVT before and after femoral and pelvic fractures was 26.71% and 17.22%, respectively.Currently, the incidence of DVT in fracture patients has not been significantly reduced by "more aggressive" anticoagulant regimens.
Drug prevention is the main measure for the prevention and treatment of DVT, but there are controversies about the indications, drug selection, starting and ending time, safety and effectiveness of anticoagulation.The results of this study showed that the risk of DVT increased to 2.31-fold in patients with femoral and pelvic fractures without anticoagulation before surgery.Contrary to Liu’s conclusion, preoperative anticoagulation in patients with hip fractures does not significantly reduce the risk of postoperative DVT or PE[6].Haut et al. found that approximately 50% of VTE occured in patients receiving "optimal prevention[7].Many problems of anticoagulation are still inconclusivet, but it is still advocated that anticoagulation should be actively used in patients with high risk of perioperative bone trauma who have no anticoagulation contraindications.As for the timing of preventive anticoagulation, our results were consistent with Xia[8].Delayed anticoagulation 24 h after trauma was positively correlated with the occurrence of VTE, and the correlation between the two was more significant when the delayed anticoagulation time exceeded 48 h.In this study, it was found that delayed anticoagulation over 24 h and 48 h after trauma was 1.80 times and 2.65 times of the risk of DVT before surgery and 1.61 times and 2.09 times of the risk of DVT after surgery, respectively, in patients with early anticoagulation.We further found that 12–24 h, 24–72 h, and > 72 h after admission were 1.31 times, 2.01 times, and 2.02 times of the risk of DVT before anticoagulation in the patients within 12 h after admission, respectively.The risk of postoperative DVT was 1.38 times, 2.20 times and 2.18 times.The early stage of trauma patients is hypercoagulable, and early anticoagulation after admission without contraindications can reduce the risk of DVT.Interruption of preventive anticoagulation is common in trauma and in patients undergoing major surgery, and is associated with patient rejection, surgical timing, and nursing errors.Louis et al. confirmed that anticoagulation interruption is an independent risk factor for DVT in trauma patients aged ≥ 50 years[9].However, we found no correlation between anticoagulation interruption and DVT, which may be related to the risk of bleeding associated with anticoagulation interruption in this study.For patients hospitalized for total knee and hip replacement within 5 days, Samama, Petersen and other large-sample, multi-center studies have confirmed that anticoagulation in these patients is safe only in the hospital[10, 11].However, there are few studies on the timing of anticoagulation after surgery. This study found that 12–24 h and 24 h after surgery were 1.78 times and 1.65 times of the risk of DVT in patients who started anticoagulation within 12 h after surgery, respectively.Therefore, starting anticoagulation within 12 h after surgery can reduce the risk of DVT, but the benefits of early anticoagulation after surgery should be weighed against the increased risk of bleeding.
Among fracture patients, the current routine anticoagulant regimens are used for the prevention and treatment of DVT in patients with different risks, which does not change the current situation that the incidence of DVT is still relatively high.It is particularly important to further clarify independent risk factors for DVT to identify high risk groups.The occurrence of DVT was significantly correlated with the fracture site. Similar to the results of Adam and Zhang[12, 13], the incidence of hip fracture (74.90%) was relatively high. Considering that the three risk factors of Virchow were mostly present in the patients with hip fracture[14].We should pay attention to the screening of DVT in these patients with fractures at specific sites, and formulate reasonable individualized prevention and treatment strategies.Meizoso et al. used RAP score in a retrospective cohort study of 1233 trauma patients and found that transfusion of more than 4 units was an independent risk factor for DVT[15].The preoperative, intraoperative and postoperative blood transfusion rates of 569 patients in this study were 8.44% (48/569), 29.70% (169/569), and 13.88% (79/569), respectively.It was further found that intraoperative blood transfusion and postoperative blood transfusion were independent risk factors for postoperative DVT, while preoperative blood transfusion was not correlated with DVT.Perhaps we should reconsider the indications and necessity of blood transfusion in practice.Song et al. reported that most patients with postoperative DVT had complicated DVT before surgery[16],In this study, preoperative DVT occurred in 26.71% of the patients, which was considered to be related to the longer average preoperative waiting time.Most of the current recommendations are that surgery should be performed as soon as possible within 48 hours after trauma to reduce the incidence of VTE[17].But in practice, 66 percent of patients with hip fractures delayed surgery[18].The reasons for delayed surgery may be as follows. 67.66% (385/569) of the patients were transferred to our hospital from other hospitals due to serious illness or limited medical conditions.Preoperative preparation for patients with medical diseases and routine preoperative examinations such as DVT screening will also delay surgery.Recently, Luksameearunothai et al. confirmed that Caprini score ≥ 12 points should be used for preoperative ultrasound examination in elderly patients with hip fracture and patients with Wells score ≤ 1 points can be safely operated immediately[19].There is a conflict between adequate preoperative preparation and early surgery and how to achieve a comprehensive and scientific evaluation of severe patients is the key to avoid unnecessary delay in surgery.Brill and Parvizi reported that chronic pulmonary disease is associated with postoperative DVT in patients with fracture[20, 21].We further found that COPD was an independent risk factor for preoperative DVT and pulmonary infection, and COPD was an independent risk factor for postoperative DVT.Systemic inflammation, hypoxemia, oxidative stress, endothelial dysfunction, and prethrombotic status would increase the risk of VTE in patients with COPD[22].Elderly fracture patients with COPD may be chronically hypoxic for a long time.Lying in bed and immobilization after a fracture would increase the risk of pulmonary infection, as well as limited mobility and lack of muscle pumping, leading to venous stasis and hypercoagulability in the lower extremities[23].Therefore, active prevention and treatment of pulmonary diseases in patients with fractures may reduce the incidence of perioperative DVT.The European Guidelines for the prevention of perioperative VTE indicate that correcting preoperative anemia could reduce the incidence of postoperative VTE in elderly patients[24].Both we and Feng found that preoperative anemia was an independent risk factor for perioperative DVT in fracture patients, which may be associated with increased D-dimer caused by anemia[26].C-reactive protein levels on the first and third days after surgery were independent risk factors for postoperative DVT, and acute inflammation reflected by high levels of C-reactive protein was considered as the trigger factor for VTE[27].The timing and necessity of perioperative anti-infective therapy need to be further validated.Hypoproteinemia is another independent risk factor for DVT. It may be that the swelling of the lower extremities leads to weakened muscle pumping and slow blood flow, and the pain caused by swelling also reduces the active activity of the lower extremities.Many studies have confirmed that hypertension, hyperlipidemia, diabetes and other chronic diseases were risk factors for DVT. This result was not obtained in this study, which may be related to the small sample size and missed diagnosis of doctors in this single center study.Drinking history, advanced age,high-energy trauma, multiple injuries, and comminuted fracture are independent risk factors for DVT. Although these factors cannot be optimized, they are helpful for early identification of high-risk groups.D-dimer detection with high sensitivity and low specificity is mostly used to exclude patients with suspected VTE, and its increased level is related to the degree of trauma, fracture site, degree of inflammatory response, pregnancy, etc.In this study, although the increase of D-dimer was not found to be an independent risk factor for DVT, the postoperative d-dimer level of the DVT group was significantly higher than that of the non-DVT group, and the D-dimer test of almost all patients was positive.This is consistent with Wang's view that D-dimer detection has poor specificity in trauma patients and its significance is limited[28].Neither Tyagi nor we found the correlation between intraoperative tourniquet use and DVT,considering that short duration of tourniquet use could not significantly affect the blood status of lower extremities.But Tyagi still believes that patients with higher VTE risk should consider using a tourniquet during surgery[29].Whether this simple, low-cost, low-risk intraoperative method can reduce the risk of postoperative DVT remains to be further studied.The results showed that the average preoperative DVT formation was 6.55 ± 0.47 days after the trauma and 6.67 ± 0.48 days after the surgery, which may be related to the peak time of blood hypercoagulability. The d-dimer level reached its peak on the 1st and 7th days after the fracture surgery[30].This study reviewed the changes in the types of DVT during the perioperative period,54.55% (6/11) complicated with distal thrombosis, 18.18% (2/11) complicated with proximal thrombosis, and 27.27% (3/11) complicated with mixed thrombosis. The incidence of distal thrombus progression to PE is relatively high, so thrombus type should not be our sole criterion for screening high-risk populations.The therapeutic anticoagulation of intermuscular vein thrombosis of the calf is controversial,Recent studies have shown that the absence of preoperative anticoagulation does not increase the risk of progression of intermuscular vein thrombosis in the calf and may aggravate postoperative anemia[8].In this study, 11.21% of the intermuscular venous thrombosis of the calf showed progressed, and it seems that therapeutic anticoagulation is necessary for such patients.
Venography is the gold standard for the diagnosis of VTE, but its application is limited due to its invasiveness, unrepeatability and possible renal and venous injuries caused by contrast agents.Noninvasive and repeatable ultrasound examination has been widely used in clinical practice in recent years. Abe's study confirmed that the dilatation of plantarum vein during ultrasound examination is an independent predictor of DVT after major orthopaedic surgery[31].However, lower extremity ultrasound examination is not suitable for patients with partial fractures. For example, patients with hip fracture cannot change the body position examination, and it is difficult to form a clear image for those with severe limb swelling and thick surgical area covered by dressings.The diagnostic examination of DVT is mainly to avoid the occurrence of fatal VTE, but how to identify early and prevent the occurrence of DVT is a more important goal. It is valuable to analyze the risk factors of DVT during the whole perioperative period for femoral and pelvic fractures.
We analyzed the correlation between anticoagulation regimen, perioperative blood transfusion, pulmonary disease and other perioperative influencing factors and DVT.However, this study has the following limitations:Firstly, this is a single-center, retrospective case-control study, which is prone to confounding factors. For example, the influencing factors not included in the study may be potential risk factors for DVT, and the study subjects were not operated by the same surgeon.Secondly, only color Doppler ultrasonography was used to determine DVT, and potential DVT patients with clinical symptoms such as lower limb swelling, pain and elevated skin temperature were not included in the case group, which reduced the effectiveness of the result data.Thirdly, all patients received lower extremity venous ultrasound examination after admission. However, there may be a deviation between DVT formation time and ultrasonic examination time in some patients with delayed admission.Fourthly, this study only reviewed the clinical medical records of the patients during their hospitalization, and did not follow up the patients after discharge, which may have omitted the occurrence of DVT after discharge, thus underestimating the incidence of DVT.