Venous thromboembolism (VTE) is a serious condition that often presents as deep venous thrombosis (DVT) and/or pulmonary embolism (PE). VTE is a concerning medical complication after surgical procedures, causing significant morbidity.1 In England 25,000 people die every year because of VTE. Mortality from VTE is considered to be more than breast cancer, road traffic accidents, and acquired immune deficiency syndrome all combined together.2 An imbalance in thrombin activity might be the underlying mechanism for VTE that can be expressed through Virchow’s triad, which has three elements: venous stasis, endothelial injury, and hypercoagulability.3,4 Postoperative immobilization decreases the venous backflow in lower extremities, and use of an intraoperative tourniquet might also aggravate the venous stasis. The nature of surgical procedures interferes with the vascular endothelium, and hypercoagulability can exist due to several factors, such as the stress of the surgery, bedrest after the surgery, or even the trauma itself.5–8 Lower extremity surgeries are a potential risk factor for developing VTE, and the literature regarding hip and knee surgeries is well-researched in terms of postoperative VTE incidence and its related risk factors and the role of prophylaxis.9–11 However, in the field of foot and ankle surgery, the literature about the incidence of VTE after surgery and the related risk factors is still unclear.
The aims of this study were to determine the incidence of clinically symptomatic VTE after foot and ankle surgery in two tertiary medical centers and to review the most recent literature regarding VTE incidence, risk factors, and prophylaxis after foot and ankle surgery.
MATERIALS AND METHODS
Ethical Review and Study Design
This study has two parts: a retrospective review of patients and a literature review. Ethical approval to conduct the retrospective case series was obtained from the Institutional Review Board (IRB) at the College of Medicine at King Xaud University, Riyadh, Saudia Arabia (approval no. 18/0081/IRB). Consent was obtained from all patients prior to the start of the study.
Patient Inclusion Criteria and Characteristics
Medical charts of patients who had foot or ankle surgery between 2016 and 2018 at two tertiary medical centers in Riyadh City, Saudi Arabia were reviewed. The sample size was estimated by considering the previous literature (level of confidence=0.95, margin of error=0.05, previous proportion=0.8%), which suggested that 114 participants should be included. We included all patients who were 18 yr of age or older. The patients’ demographic data (age, gender, and body mass index [BMI]), medical comorbidities (diabetes mellitus [DM] and hypertension [HTN]), and prescription of thromboprophylaxis were collected from our electronic medical records. The names of the procedures were documented and categorized as follows: forefoot, midfoot, hindfoot, ankle, and combined deformity. The type of procedure (elective or emergency) also was documented. VTE diagnosis was determined based on the 90-day postoperative follow-up through the medical records with or without radiographic reports of symptomatic VTE. These data, including VTE diagnosis, were also double-checked by calling each patient on the phone to ensure capture of patients who were diagnosed somewhere other than the primary center.
Data were entered and analyzed by the Statistical Package for Social Sciences (version 22.0; SPSS, Chicago, IL). Continuous variables were presented as means and standard deviations, while categorical variables were demonstrated as numbers and percentages.
The second part of this study was to review the current literature of major level II and III studies between 2017 and 2018. Studies that highlighted the incidence of VTE after foot and ankle surgery were reviewed for risk factors and recommendations regarding the use of prophylaxis. The terms (venous thromboembolism OR DVT) in (foot and ankle surgery OR foot and ankle procedures) were searched on PubMed.
Retrospective Chart Review
In the review of 125 patients, 56 (44.8%) were male and 69 (55.2%) were female. The age of the patients ranged from 15 to 93 yr, with a mean of 38.7 yr, and their BMIs ranged from 15 to 50 kg/m2, with a mean of 28 kg/m2. Patient clinical characteristics are summarized in Table 1.
A total of 85 patients (68%) were discharged on thromboprophylaxis after the procedure. Names of procedures are shown in Table 2. Of 125 patients, one patient (0.8%) developed postoperative symptomatic VTE. The patient, a 39-year-old male with a BMI of 27, medically cleared and a nonsmoker, underwent ankle arthroscopy for ankle ligament repair and presented 14 days after the surgery with a symptomatic infrapopliteal deep vein thrombosis (DVT) that was confirmed by a radiographic study. Two patients (1.6%) had a history of VTE before surgery; however, neither of them developed VTE after the surgery. No complications were encountered in patients who were receiving chemoprophylaxis such as bleeding, hematoma at the surgical site, allergic reactions, or others.
Incidence and Risk Factors
The most recent studies done in different populations considered symptomatic VTE after foot and ankle surgery as a rare event, and a very low incidence rate was reported as well (Table 3).
Huntley et al.12 conducted a retrospective cohort study from 2006 to 2015 to estimate the incidence of VTE from more than 400 hospitals nationwide. Patient demographics, comorbidities and postoperative complications including VTE were assessed. The overall risk of symptomatic VTE was 0.6%. Of 23212 patients, 87 (0.4%) developed a DVT and 55 (0.2%) developed pulmonary embolism, with eight patients diagnosed with both DVT and PE (8/142, 5.6%). The average period of VTE development was not specified. The identified risk factors (P value <0.05%) were age older than 60 yr, female gender, obesity (BMI >30), inpatient status, and nonelective surgery. Furthermore, the development of postoperative pneumonia was significantly associated with VTE events.
Richey et al.13 reported 173 VTE cases among 22486 patients (0.8%) that developed within an average period of 6 wk after surgery. This was a retrospective cohort study with a 6-month clinical and radiographic postoperative follow-up for patients who underwent foot and ankle surgery. It excluded patients with a history of polytrauma, or those who underwent other orthopaedic, cardiac, or general surgery. In the second part of the study, the author randomly assigned 90 age-matched and sex-matched case-control pairs to compare patients with VTE (cases) to those without VTE (controls) to estimate the possible risk factors. Interestingly, the use of anticoagulation was significantly associated with an increased risk of VTE events (P-value=0.03); this was based upon bivariate analysis, and the small sample size in both groups could have had an effect. Other identified risk factors were obesity, a previous history of VTE, hormonal therapy, immobilization of more than 2 wk but no more than 8 wk, a history of trauma, midfoot or rearfoot surgery, procedure duration of 60 min or more, and general anesthesia. However, after multivariable regression analysis, obesity, previous history of VTE, hormonal therapy, and immobilization were the only remaining significant factors with an adjusted odds ratio (AOR) of 6.1, 15.7, 8.9, and 9, respectively. This risk of VTE incidence was even higher if three or more risk factors were present (P-value=0.001).
An incidence rate of 0.8% was also concluded in another study conducted by Ahmed et al.14 They reported 14 infrapopliteal DVTs, one suprapopliteal DVT, and seven PE cases in 2774 patients that developed within 90 days after foot and ankle surgery. In that retrospective cohort analysis, the author excluded patients with coagulopathy, a history of previous VTE, and patients on anticoagulants as a way to control confounding factors. Asymptomatic cases of VTE were not discussed by the author.
Although most recent studies suggested a VTE incidence of less than 1.0%, Blanco et al.15 reported a higher VTE incidence of 3.0%, although they did have a small sample size. This was a prospective cohort study in three parts. One part of the study followed a total of 199 surgically managed ankle fractures. All patients underwent VTE risk assessment; only two of 199 were classified as high-risk patients, and chemoprophylaxis was prescribed for them. DVT developed in five of 199 patients. One patient experienced PE. None of the six was on prophylaxis. The results did not show a significant difference in the VTE incidence between surgically and conservatively treated ankle fractures.
The American College of Foot and Ankle Surgeons (ACFAS) reviewed the published literature on chemoprophylaxis after foot and ankle surgeries.16 They concluded that routine chemoprophylaxis should not be administered, and the primary physician should try to assess the risk of VTE for each patient. In addition to chemoprophylaxis, the ACFAS recommended the use of different preventive models like early mobilization, mechanical compression, and correcting any modifiable risk factors to minimize the risk of subsequent VTE. Harms and benefits of each VTE-preventive model should be explained to the patient, and the final decision must involve both the primary physician and the patient.
Our study was designed to estimate the incidence of clinically symptomatic VTE after foot and ankle surgeries at our institutions. Only one case of symptomatic infrapopliteal DVT was identified and confirmed, which resulted in an incidence of 0.8% of the total population. Our findings support the data previously published in several studies.12–14 It is possible that this low incidence of VTE can be explained by the less invasive nature of foot and ankle surgeries leading to less damage to blood vessels and minimal interruption of hemostasis, all of which are crucial precipitating factors for subsequent VTE development as considered by Virchow’s triad. Determining the risk factors in our study was not possible because of the low incidence rate of VTE in our sample.
Recent studies also show a very low incidence rate of VTE after foot and ankle surgery, with a higher risk being reported in patients with certain risk factors. Huntley et al.12 identified age older than 60 yr, female gender, obesity, inpatient status, nonelective surgery, and postoperative pneumonia as significant risk factors for VTE. Although their sample size was large, patients with coagulopathy or thromboprophylaxis could not be determined. In addition, the 142 recorded cases of VTE were all symptomatic patients, and no screening test was used to identify asymptomatic patients, which might have resulted in underestimation of the correct incidence. In the study by Richey et al.,13 multivariable regression analysis showed obesity, previous history of VTE, hormonal therapy, and immobilization as significant risk factors, and this was even higher if three or more risk factors were present. Ahmed et al.14 reported a less than 1% incidence in the 90 days after foot and ankle surgery, with obesity being the only factor of statistical significance; however, this study did exclude patients with coagulopathy, previous VTE, and patients on anticoagulant, and they did not discuss asymptomatic VTE patients, which could have underestimated the incidence of VTE. Blanco et al.15 reported the highest incidence at 3%; however, the small sample size may have caused an overestimation in this case. Their results also did not show a significant difference in the VTE incidence between surgically and conservatively managed ankle fractures, which might indicate that the surgery and related operative factors, such as the type of anesthesia and tourniquet duration have only a minimal impact on VTE risk after ankle fracture management.
Prescribing chemoprophylaxis after foot and ankle surgery has seen growing interest in the last decade. The decision-making for prescribing or not is a life-saving challenge for the treating physicians, as anticoagulants could play a role in protecting patients from VTE but could also expose patients to life-threatening events. Until now, there have been no clear guidelines for the processes of chemoprophylaxis prescription to be followed in the management of patients who underwent foot and ankle surgeries. The ACFAS16 recommended making the decision for prophylaxis in patients individually. Recognizing the precipitating risk factors in an individualized method with or without the use of a specified VTE-risk stratification tool (e.g., Well’s criteria) is the only way to decide on prophylaxis use and this has been agreed upon by most recent studies. For our patients, identifying high-risk patients and the decision to give chemoprophylaxis after the surgery was determined by the primary treating physician after taking into consideration the individual preoperative and postoperative assessments of each patient. No complications were encountered in our patients who were receiving chemoprophylaxis.
The limitations of this study included the small sample size, although the incidence of VTE was comparable to the published literature. Also, the nature of the retrospective design has its own inherent limitations.
As compared to previous literature, the incidence of clinically symptomatic VTE after foot and ankle surgery appeared to be low, with less than a 1% rate identified in our patients. For the present time, a proper assessment of patients individually before, during, and after the surgery, with careful stratification of risk level in terms of prophylaxis consideration is advisable. For future purposes, developing a well-organized and strict guideline for VTE prophylaxis in foot and ankle surgeries is recommended.
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