DVT is a prevalent complication due to traumatic fracture, which is mostly found in lower extremity fractures[5]. Previous studies have reported that the incidence of DVT in lower extremity fractures is 32%[7, 14, 15]. The incidence of upper extremity fracture DVT is lower but can easily cause PE if it occurs[15, 16]. PE is a serious complication in patients with trauma, with a high mortality rate[17]. Most cases of PE occur within 72 hours post-injury. Previous studies have reported that the incidence of early post-traumatic PE is as high as 10%–42%, with a mortality rate of approximately 50%[10, 18] . Elderly patients with fractures have a higher risk of developing DVT; therefore, early prediction and intervention of DVT in elderly patients with upper extremity fractures is of immense significance.
Venography is considered the gold standard diagnostic procedure for venous thrombosis[19]; however, it is complicated, expensive, and invasive. Therefore, color Doppler vascular ultrasound is gradually being considered the diagnostic method of choice.
In this study, the incidence of DVT in upper limb fractures was 10.58%, which was higher than the 1.6% incidence reported by Rafael S[20] and the 0.66% incidence reported by Davide[21] . This can be because only elderly patients were included in this study, and there exists a strong correlation between advanced age and thrombosis. Some researchers have reported that there is no direct correlation between DVT of upper limb fractures and medical complications[21] . The results of this study revealed that upper limb fracture thrombosis exhibits the highest incidence of periprosthetic shoulder fractures. Univariate analysis showed no significant difference in the history of hypertension between the two groups. We hypothesize that most hypertensive patients may be taking antihypertensive drugs, which can decrease their blood pressure levels to normal levels. Therefore, we measured the blood pressure of patients with high blood pressure again, with systolic blood pressure ≥ 140mmHg or diastolic blood pressure ≥ 90mmHg as the standards. Univariate analysis was again performed and found that smoking, indwelling needle, comorbid high blood pressure, hyperlipidemia, diabetes mellitus, atrial fibrillation, anemia, BMI >25 kg/m2, and fracture site were risk factors for DVT, but smoking, indwelling needle, atrial fibrillation was not an independent risk factor in the multivariate analysis.
Excessive blood pressure
Unlike other studies, the present study reports that there is no direct correlation between the history of hypertension and thrombosis. However, excessive blood pressure increases the risk of thrombosis, which might be because high blood pressure leads to a collision of blood cells in the bloodstream with the vessel wall. This disrupts some of the blood cells and stimulates the coagulation mechanism.
Hyperlipidemia
Plasminogen activator inhibitor-1 (PAI-1), a marker of fibrinolytic activity, is produced and retained by vascular endothelial cells. Elevated levels of PAI-1 increase the risk of thrombosis[22, 23]. The content of PAI-1 in plasma of patients with hyperlipidemia are higher than that of patients without hyperlipidemia[24], so patients with hyperlipidemia have a tendency to thrombosis. At the same time, trauma causes endothelial cell injury and releases more PAI-1, both of which raise the risk of thrombosis.
Diabetes
Diabetes, as is well known, can impact lipid metabolism, and dyslipidemia can result in aberrant fibrinolysis and coagulation, which raises the risk of thrombosis. Diabetes induces hypercoagulability in the blood, one of the three major risk factors for thrombosis. The blood coagulation system may be impacted by diabetes-related vascular inflammation, and the combination of these variables raises the risk of thrombosis.
Anemia
Unifactorial and multifactorial analyses revealed that anemia increases the risk of thrombosis. Virchow proposed the following three important factors for thrombosis: stagnant blood flow, hypercoagulable state of blood, and vascular endothelial damage[25] . Our study reports that anemia may slow down blood flow in the body, causing thrombosis.
D-dimer
Previous studies have reported that in lower extremity fractures, increased levels of D-dimer indicate the increased activity of coagulation and fibrinolysis. Furthermore, the blood is in a hypercoagulable state, which increases the risk of thrombosis[26, 27] . In this study, the D-dimer levels were not statistically different between the two groups. D-dimer elevation is related to thrombosis, diabetes, infection, malignant tumors, and advanced age can cause D-dimer elevation; therefore, the prediction of DVT by D-dimer has a certain value and warrants further studies.
BMI
Obesity is not recognized as an independent risk factor for DVT, but studies have proved that there is a causal relationship between obesity and DVT. Reducing BMI can decrease the probability of DVT[28]. In this study, BMI > 25kg/m2 was an independent risk factor for DVT in patients with upper limb fractures. First, obesity increases the risk of type 2 diabetes. Secondly, adipokines in adipose tissue affect glucose and lipid metabolism, increase coagulation activity, reduce fibrinolytic activity, and induce chronic inflammation, thereby increasing the risk of thrombosis.
Smoking
Smoking is a well-established risk factor for atherosclerotic disease, but its role as an independent risk factor for VTE remains controversial[29]. In our study, smoking increased the risk of DVT after upper limb fracture in the elderly, but it was not identified as an independent risk factor. Then we found that in male patients, there was no significant difference in smoking habits between male patients in the DVT group and those in the non-DVT group (p > 0.05). However, among female patients, there was a significant difference in smoking habits between the two groups (p < 0.05). This is consistent with the study by Regina[30]. We only collected data on the presence or absence of smoking behavior, and did not include specific details such as smoking time, number of cigarettes, etc., which may also have an impact on thrombosis.
Indwelling needle
The main risk factors for deep vein thrombosis of the upper extremity (DVT-UE) are central venous catheter(CVC), peripherally inserted central venous catheters (PICC), and cardiac pacemakers[31]. Foreign bodies in the vascular system represent the most significant independent risk factor for DVT-UE[32]. Therefore, patients with intravenous catheters should undergo regular testing for upper and lower extremity thrombosis, irrespective of the presence of fractures. The incidence of upper extremity deep venous thrombosis is increasing, which may be related to the rise in CVC, PICC, and pacemaker implantation[33-35]. In this study, the use of an indwelling needle is identified as a risk factor for DVT in upper limb fractures, but it is not considered an independent risk factor. On one hand, the presence of the needle inserted into the vein as a foreign object will increase the risk of thrombosis. On the other hand, when compared to CVC, PICC, and pacemaker, an indwelling needle has a smaller volume, causes less trauma, and has a shorter retention time, so it cannot be considered an independent risk factor.
The incidence of thrombosis in patients with malignant tumors is 2–3 times higher than that in non-tumor patients[16, 36, 37]. Therefore, more attention should be paid when there is a combination of malignant tumors or pathologic fractures. In elderly patients with lower extremity fractures, the incidence of DVT increases as the preoperative waiting time increases. Therefore, the preoperative waiting time, such as most prolonged surgical timing due to glycemic problems, should be minimized in elderly patients with upper extremity fractures, which requires the extensive experience of clinicians in regulating blood glucose levels to normal levels as quickly as possible. In 38 cases of DVT, 12 cases have occurred in the lower extremities. It is possible that the pain caused by fractures led to their refusal to walk around. None of the patients reported experiencing pulmonary embolism. However, this does not necessarily mean that pulmonary embolism did not occur. Due to financial constraints, CT scans are not performed when there are no significant symptoms.
This study has some limitations. The sample size included in this study was small, and we only included elderly patients with fractures. Since we excluded patients with malignant tumors and all of the patients in our study did not have cardiac pacemakers, PICCs, or CVCs prior to surgery, more research is required to understand the DVT circumstances in these patients.
To summarize, the incidence of DVT in patients with upper limb fractures is lower than that of lower limb fractures; however, its risk should not be underestimated. For elderly patients with upper limb fractures, especially peri-shoulder fractures, as well as those with hyperlipidemia, diabetes mellitus, high blood pressure, anemia, obesity, and internal medicine diseases, such as malignant tumors, the clinical testing should be strengthened. Furthermore, anticoagulant drugs should be given when necessary to prevent the risk of PE and decrease the clinical sequelae associated with thrombosis.