Patient characteristics
In total, 1454 patients suffering a lower extremity fracture were screened. After excluding, 334 patients suffering uninjured limb DVT. Of these patients, 269 fractures happen above the knee, 37 fractures happen around the knee, 28 fractures happen below the knee. All the patients underwent surgery. The procedures included: open reduction with internal fixation in 284 patients, hemiarthroplasty in 3 patients, total hip replacement in 1 patient, and closed reduction in 46 patients. All patients were treated with low-molecular-weight heparin at admission. On average, all the patients were aged 71.43 (standard deviation [SD] 13.86) years range from 17 to 95 years old. Of these patients, 218 (65.27%) were female and116 (34.73%) were male. No fatal bleeding events or bleeding into a critical site was found in this study.
The incidence of uninjured limb DVT in preoperative ultrasound
The preoperative ultrasound data for patients with a lower extremity fracture with or without a thrombosis in the uninjured limb was compared in the patients’ characteristics (Table 1). All the patients were diagnosed busing ultrasound to identify the thrombosis in lower limbs. There were 140 patients with a thrombosis to the uninjured limb (9.63%) and 1314 patients without a thrombosis to the uninjured limb (90.37%). There were 9.01% peripheral DVT, 0.07% central DVT, and 0.55% mixed DVT. Peripheral DVT constituted 93.57% (131/140) of all DVTs.
Importantly, there were 50 patients with a left lower extremity fracture who suffered a DVT in both lower extremities (3.44%), 22 with a left lower extremity fracture who suffered a right lower extremity DVT (1.51%), 34 with a right lower extremity fracture who suffered a left lower extremity DVT(2.34%) and 34 with right lower extremity fractures who suffered a DVT in both lower extremities (2.34%).
Univariate analysis of preoperative uninjured limb DVT
There were no statistically significant differences between the two groups in: medical morbidity excluding hypertension and coronary heart disease, Body Mass Index, days between fracture and hospitalization, D-dimer at admission, preoperative D-dimer, or CRP at admission. However, in the thrombosis group, female patients, patients with a fracture located above the knee, and patients classified as stage Ⅱ of American Society of Anesthesiologists Physical Status Classification System (ASA) were statistically different than the no thrombosis group. In addition, more patients in the thrombosis group suffered hypertension and coronary heart disease than in the no thrombosis group. (32.86% vs. 21.91%, P=0.003; 32.86% vs. 21.76%, P=0.003), Age (72.42±13.57 vs. 60.98±19.38, P=0.000) was found to be another vital factor contributing to thrombosis (Table 1).
Multivariate analysis of preoperative uninjured limb DVT
Multivariate analysis was used to detect the risk factors by entering age, sex, types of fracture, hypertension, coronary heart disease and ASA classification. The results showed that age (OR=0.965, 95 CI%: 0.954 - 0.977; P=0.000) and sex (OR=0.667, 95% CI: 0.451-0.986, P=0.042) were independent risk factors for preoperative DVT.
The incidence of uninjured limb DVT in postoperative ultrasound
All patients underwent ultrasonography postoperatively to identify the thrombosis in lower limbs. Thrombosis was found in the uninjured limb of 295 patients (20.29%) and 1159 patients did not have a thrombosis in the uninjured limb (79.71%). There were 19.33% peripheral DVT, 0.21% central DVT, 7.57% mixed DVT. Peripheral DVT constituted 95.25% (281/295) of all DVTs (Table 2).
Importantly, there were 127 patients with a left lower extremity fracture who suffered a DVT in both lower extremities (8.73%), 25 with a left lower extremity fracture who suffered a DVT in the right lower extremity (1.72%), 33 with a right lower extremity fracture who suffered a DVT in the left lower extremity (2.27%) and 110 with a right lower extremity fracture who suffered a DVT in both lower extremities (7.56%).
Univariate analysis of postoperative uninjured limb DVT
In two groups, there was no statistically significant difference in the medical morbidity excluding hypertension, coronary heart disease and stroke, Body Mass Index, length of hospital stay, days between fracture and hospitalization, days between fracture and operation, duration of operation, liquid transfusion, preoperative D-dimer values, C-reactive protein at admission and at postoperative day 5. However, in the thrombosis group, more patients were female (P=0.000), fracture above the knee (P=0.000), and ASA stage Ⅱ (P=0.000) compared to the no thrombosis group. Similar to the preoperative ultrasound data, age is a contributing factor to postoperative thrombosis (71.76±13.42 vs. 59.62±19.66, P=0.000). Coronary heart disease, stroke, and hypertension were also important factors contributing to postoperative thrombosis (P=0.003, P=0.017, P=0.009). In addition, blood loss was another factor that contributed to postoperative thrombosis (P=0.000). In the serum markers, D-dimer at admission, at postoperative day 1, at postoperative day 3, at postoperative day 5 were higher in the thrombosis group (Table 2).
Multivariate analysis of postoperative uninjured limb DVT
Multivariate analysis was used to detect the risk factors by entering age, gender, types of fracture, hypertension, coronary heart disease, stroke, ASA classification, blood loss, D-dimer at admission, D-dimer at postoperative day 1, D-dimer at postoperative day 3 and at D-dimer at postoperative day 5. The results show that D-dimer at admission (OR=0.941, 95 CI%: 0.887-0.999; P=0.045), D-dimer at postoperative 5 day (OR=0.889, 95 CI%: 0.819-0.965; P=0.005), and blood loss (OR=0.997, 95 CI%: 0.995-1.000; P=0.020) were independent risk factors for postoperative DVT.
The dynamic changes of uninjured limb DVT before and after operation
There were 334 patients suffering uninjured limb DVT in 1454 patients. There was a total of 53.60% (0.90%, 52.40%, 0.30%) patients without changes during the hospital stay. There were 5.39% of patients who went from having a preoperative peripheral DVT to no thrombosis postoperatively. Conversely, 34.73% (33.83%, 0.30%, 0.60%) of patients changed from having no preoperative thrombosis to developing a peripheral, central, or mixed DVT postoperatively (Figure 1).