Symptomatic DVT One Month After TKA Was Associated With Tourniquet Reuse During Operation

Background: DVT (Deep vein thrombosis) was one of the most common and sever complications after TKA (total knee arthroplasty). When tourniquet use and sometime the reuse was performed for surgery convenient of TKA. There was not sure if tourniquet use or reuse during operation would increase DVT after TKA. Methods: A retrospective study was performed about primarily TKA in our institute continuous 5 years. Univariate analysis was performed and potential intervention variables (P ≤ 0.1) were included in multiple factor analysis to certain the independent risk factors. Results: 807 patients (431 females and 376 males) were included with mean age was 65 years old. 3.84% (31 patients) were occurred sym-DVT (symptomatic DVT) one month after TKA with median time of diagnosis was 17 days. Incidence of sym-DVT after tourniquet reuse was signicant high than once use and no use (7.25% versus 2.54% and 1.86%, P = 0.014 and 0.072), mean time of tourniquet use was 90.46 ± 14.28 mins in once and 106.58 ± 16.13 mins in reuse (P = 0.045). After multiple analysis, independent risk factors were revealed as history of tumor (P = 0.021), history of DVT (P < 0.001) and tourniquet reuse (P = 0.005). Conclusions: Tourniquet reuse was associated with highly incidence of sym-DVT other than history of tumor and DVT. There should be once use of for prevent

The sym-DVT which were needed treatment account almost 70% of all DVT patients. (7) If the sym-DVT was not acceptted proper treatment, half of them would ended with PE.(8) DVT prophylaxis as routine anticoagulation has bene t of low related complications after TKA. (9) TKA was an operation after thorough preoperative assessment, so the surgery technic had a big deal with DVT after procedure. (10) And when tourniquet was used in TKA for better exposure frequently, hemodynamic changes and endothelial injury were theoretically being considered as iatrogenic injuries.
Literatures were not sure if tourniquet reuse (once more tourniquet use in operation) was the risk factor of sym-DVT. So, we performed a retrospective study to evaluate if tourniquet reuse was one of the risk factors.

Methods
Total knee arthroplasty patients in our institution from 1 January 2010 to 31 December 2016 were reviewed retrospectively. Inclusion criteria: adult patients (≥ 18 years), rst time of TKA, inexistence of DVT preoperative (determined by lower extremity deep venous of ultrasonography). Exclude criteria: haemophiliac, revision surgery, limb activity limitation for stroke, sym-DVT occurred at health extremity, and loss to follow-up. The follow-up owchart was showed in gure 1.
Thrombo-prophylaxis was included chemoprophylaxis and physical prophylaxis. LMWH (low molecular weight heparin) 4000 U was used 12 hours after surgery and once daily last hospitalization. LMWH was used as bridging therapy if patient was used antiplatelet drug. In the meanwhile, pump treatment was used one day after surgery until full weight bearing.

Fellow-up and diagnosis of symptomatic DVT
If the patient occurred low leg pain and tenderness with swelling, or calf circumference (10 cm under tibia tuberosity) was increased over 2 cm than health limb, or swelling was severing. Statistical method Student t-tests or Wilcoxon rank sum tests were used to compare numerical variables between groups, and chi-square tests were used in categorical variables. Repeated Measures were used to analyze BP parameter at different period. One-sample t-tests were used to analyze outlier from base line. Multivariate Covariance analyses were used in variation of BP parameter during procedure. Pearson Correlation analyses were used in two numerical variables. Variables with P ≤ 0.1 were considered as covariates (potential risk factors) and K-Independent Samples tests were used to analyze correlation between groups. ROC analyses were used in numerical variables (if P ≤ 0.1) to assess tness cut-off value, then rounded to the nearest whole number and transform numerical variables to binary variables. Variables with P ≤ 0.1 enter in multiple logistic regression analysis (choose Forward: Conditional method). The independent risk factors were showed as OR (odds ratio, 95% CI). P values < 0.05 were considered statistically signi cant. The statistical analyses were performed using SPSS version 17.0 (SPSS Inc., Chicago, Illinois).
The ethics committee approved the study and each participant provided verbal consent.
Operation factors between sym-DVT and non-DVT patients was showed in Table 2. The potential intervention variables (P ≤ 0.1) were as follows: tourniquet use (P = 0.065), tourniquet reuse (P = 0.043), length of operation (P = 0.093), length of tourniquet use (P = 0.080), length of tourniquet reuse (P = 0.008). Incidence of sym-DVT after tourniquet reuse was signi cant high than once use and no use (7.25% versus 2.54% and 1.86%, P = 0.014 and 0.072). Length of operation and tourniquet use were ROC analysis was used to evaluate the cutoff value of numerical variables (P ≤ 0.1) and transformed to binary variables (showed in Table 3) as follows: age, BMI, length of operation and so on. The incidence difference of sym-DVT between them were also estimated and showed that each P < 0.1. Then these binary variables were moved to multiple logistic regression analysis. And independent risk factors were displayed as follows (showed in Table 4): history of tumor (P = 0.021, OR = 2.073), history of DVT (P < 0.001, OR = 5.078) and tourniquet reuse (P = 0.026, OR = 2.436). ( gure 1).

Discussion
This study found that tourniquet reuse was one of independent risk factors of sym-DVT one month after TKA (OR was 2.43), along with factors of history of tumor and history of DVT. Sym-DVT was more likely had longer tourniquet use (93.46 ± 16.75 versus 88.71 ± 14.28, P = 0.060) and longer operation time (75.37 ± 14.39 versus 60.12 ± 13.81, P = 0.073). Longer use of tourniquet had positive correlation with high lactic, CRP (C-reactive protein), D-dimer, low limb swelling and negative correlation with albumin.
Studies were found many risk factors of VTE in TKA patients (1,11,(13)(14)(15)(16). Longer procedure was markedly associated with more complications, VTE was one of them (1,17,18). Operation length was related with VTE, but without statistics difference (11). Meanwhile, tourniquet was normally used around TKA operation and would increase incidence of VTE (19). Sym-DVT was found higher in patients with longer operation and tourniquet reuse. The reason might be the pathological factors of Virchow's triad were aggravated and eventually caused DVT.
Obesity patients were at risk of increased operation di culty, prolong procedure time and more possibly had complications (20). VTE event would increase 2.0-3.3% more in obese patients six month after TKA (14). The increased relevance with the BMI was showed in our study, and the independent risk factor was found obesity over II grade. History of VTE was considered increase VTE markly after TKA (15,21), but studies were not always in the same opinion (22)(23)(24). In our study, patients with history of DVT were at almost 4 times higher risk of sym-DVT. Also old age was a high risk factor for sym-DVT (11,13), especially when patient was older than 80 years, there would be 1.58 times more than under 55 years (11).
Old age patients were showed more likely occurred sym-DVT in this study, but it was not an independent risk factor.
Charlson index was indicated internal medical condition and higher score would cause 1.4-1.73 times more VTE (11,15), especially the history of cardiovascular disease (7,25) and tumor (26,27). These patients might be in irritable state and more susceptible to thromboembolism. For studies considered that VTE after operation was strongly associated with in ammatory state, for brinolysis activity was decreased under in ammation and increased VTE(28-30). And this study indicated tourniquet used in patients with history of tumor and DVT were caused signi cant more sym-DVT.
There were some limits that need further research. First of all, for the disadvantage of retrospective study, the awareness of low limb swelling and medical knowledge of patient might cause some arti cial bias. Secondly, some inappropriate daily activity or living habit might in uence the occurrence of sym-DVT.
Thirdly, prothrombin or clotting factor gene mutation might crucial in thrombosis, and it was designed to measure it in further research.

Conclusions
Tourniquet reuse was associated with highly incidence of sym-DVT other than history of tumor and DVT.
Longer tourniquet use was associated with more possibility of sym-DVT. There should be once use or no use of tourniquet would be helpful for prevent DVT after TKA operation.

Consent for publication
We declaring our consent for the manuscript to be considered for publication. There had no personal medical information in the text or images of this manuscript.

Availability of data and materials
Not applicable

Competing interests
This manuscript is not currently under consideration by any other journal. None of the authors have interests in any company or institution that might bene t from the publication of this manuscript.

Funding
We are con rming that this study was supported by National Natural Science Foundation of China (No. 81974576) and Zhejiang Chinese Medical University scienti c research (No. 2019ZG07).

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Each author was equal contributed to the manuscript.