Daniel Guss, Christopher W. DiGiovanni, Steven M. Raikin.
Response/Recommendation: There is insufficient data to characterize foot and ankle surgical procedures as either major or non-major risk with regard to postoperative venous thromboembolic (VTE) event risk. Certain diagnoses, such as achilles rupture, do seem to demonstrate a higher rate of VTE, but this may be independent of surgical or non-surgical management and instead relate to impaired venous return. Patient-specific risk factors are critical towards understanding the risk of VTE after foot and ankle (F&A) surgery and may include age > 50 years, splint or cast immobilization, Charlson Comorbidity Index (CCI) > 2, varicose veins, history of VTE, hypercoagulability disorder, and inflammatory arthritis.
Strength of Recommendation: Limited.
Rationale: Historically, discussion regarding the incidence of VTE disease in orthopaedic surgery—and the concordant use of chemoprophylaxis to prevent deep venous thrombosis (DVT) and pulmonary embolism (PE) has revolved around VTE risk inherent to a given procedure. Procedures such as total hip arthroplasty (THA) or total knee arthroplasty (TKA), as well as hip fracture surgical fixation, have uniformly high rates of VTE in the absence of preventative measures1. Professional societies such as the American College of Chest Physicians (ACCP) have thus explicitly recommended administering chemoprophylaxis “for patients undergoing major orthopedic surgery (THA, TKA, hip fracture surgery [HFS])”2. In defining a subset of orthopaedic procedures as major, however, the ACCP guidelines did not conversely define other procedures as minor. They only noted that chemoprophylaxis was unnecessary in “in patients with isolated lower-leg injuries requiring leg immobilization”. Indeed, while the word “major” appears 201 times in the 2012 ACCP guidelines, the word “minor” appears only twice, and specifically pertaining to minor bleeding events.
The challenges providers face when addressing VTE among F&A patients are manyfold. First, while the rate of VTE is much lower amongst F&A patients than after THA or TKA patients, it is certainly neither zero nor uniform across all patients and procedures3. This makes any risk-benefit analysis of using chemoprophylaxis far more nuanced, as one weighs the risk of DVT and PE against adverse outcomes such as bleeding events, wound ooze, and even heparin-induced thrombocytopenia4. Second, without overwhelming implications of any procedure itself determining use of chemoprophylaxis, patient-specific risk factors play an increasingly important role, undermining a “one size fits all” approach to VTE prevention5,6. Lastly, it may not be a procedure per se that provokes a DVT or PE, but rather the pathologic condition itself (e.g., achilles tendon rupture with gastrocsoleus retraction), often independently of operative versus nonoperative management, as well as the requisite period of non-weight bearing and/or immobilization7,8.
The confusion shared by F&A clinicians and patients alike is reflected by the diverse clinical practice guidelines put forth by multiple professional societies pertaining to surgery of the lower extremity, including F&A procedures. As noted, for example, the ACCP does not recommend use of chemoprophylaxis after F&A surgery2. In contrast, the National Institute for Health and Care Excellence (NICE) in the United Kingdom does recommend that surgeons use of chemoprophylaxis after lower extremity procedures other than THA, TKA, or HFS when patients have one or more risk factors, but conflates risk factors such as a prior history of VTE in an individual or first-degree relative with more ubiquitous risk factors such as age > 60 years, lower limb procedures lasting > 60 minutes, and body mass index (BMI) > 30 kg/m2 9 Moreover, the American Orthopaedic Foot & Ankle Society (AOFAS) has stated that there is insufficient data for it to recommend for or against the use of routine VTE prophylaxis after F&A surgery, and that further research is necessary10.
Thus, the decision to use chemoprophylaxis after F&A surgery must integrate not only the nature of the procedure, but also patient-specific risk factors, many of which have yet to be defined. Validated risk assessment tools do exist, but have been honed around non-orthopaedic procedures such as general or vascular surgery11,12. Among the most commonly used risk assessment scales is that purported by Caprini, which assigns a point value to each of forty elements that allow clinicians to stratify patients by risk status, with ≥ 5 total points considered “highest risk”13. It does distinguish between minor and major surgery, but does so based on whether the time of surgery crosses a threshold of 45 minutes; any surgery of > 45 minutes duration is considered major. In practice, patients aged 41-60 years (1 point) undergoing a minor surgical procedure (1 point) who have a BMI > 25 kg/m2 (1 point) would be considered “high-risk” (3-4 points), making it difficult to know how to apply this instrument to the F&A population. A recent study by Dashe et al., retrospectively compared the incidence of DVT and PE among 300 orthopaedic patients with pelvic or acetabular fractures, empirically deemed to be at “high-risk”, to the incidence among 548 patients with foot and ankle fractures deemed to be at “low-risk”14. It found that those patients with pelvic and acetabular fractures did indeed demonstrate a higher rate of VTE (8% vs. 1.6%, p < 0.0001), but the traditional Caprini score threshold of 5 did not appropriately differentiate those at “highest risk” between the two groups, and the authors instead recommended a threshold of 10 points. Unfortunately, even this latter score threshold loses utility when applied to F&A patients without fractures, because it largely emanates from the 5 points assigned to “hip, pelvis or leg fracture (< 1 month)”13.
Complicating matters is the fact that certain specific diagnoses within F&A surgery do seem to correlate with a heightened risk of VTE. Achilles tendon ruptures have been reported to have a rate of DVT ranging from 0.4% to 34%15,16. This reported wide variability emanates largely from whether patients in a given study are routinely screened with ultrasound, or whether only symptomatic patients are imaged. Studies, however, have highlighted rates of symptomatic DVT as high as 23.5% and, most notably, have not necessarily found a difference between operatively versus nonoperatively treated patients8,17,18. Thus, rather than achilles tendon repair being considered a “major surgery”, it may be that achilles ruptures as a whole are better identified as a “major diagnosis”. Even more confusing, it is not entirely clear that chemoprophylaxis effectively lowers the rate of VTE after achilles rupture based on prospective, randomized study16.
Extrapolating the idea that more proximal procedures in the lower extremity have higher rates of VTE than those performed more distally, it intuits that within F&A specifically, one might find a progressive increase in the rate of postoperative VTE when moving from the forefoot to the hindfoot/ankle to the lower leg. A study by Hejiboer et al., compared the rate of VTE and adverse bleeding events among two separate, matched cohorts of 5,286 patients undergoing below-knee procedures with and without chemoprophylaxis using propensity score matching4. The authors did identify an increase in the rate of VTE as one moved more proximally within the F&A, including the forefoot (0.8%), hindfoot/ankle (1.4%), and lower leg (3.4%) among patients who did not receive chemoprophylaxis. The study also found an analogous increase among patients receiving chemoprophylaxis who underwent procedures to the forefoot (0.2%), hindfoot/ankle (0.4%), and lower leg (1.0%), and was able to demonstrate a 3-fold reduction in the rate of VTE when using chemoprophylaxis but a 2-fold increase in bleeding events. This finding highlights the inherent tradeoffs of preventative measures.
Ultimately, in F&A surgery, as compared to THA and TKA, patient risk factors play a disproportionate role in precipitating a higher rate of VTE. Risk factors in the literature have included age > 50 years, splint or cast immobilization, achilles tendon ruptures, increased comorbid burden as reflected in a CCI > 2, varicose veins, history of VTE, either in a given individual or first-degree relative, a known hypercoagulability disorder and inflammatory arthritis5,6,19–22. This must be kept firmly in mind when interpreting studies. For example, a recent meta-analysis that incorporated six prospective randomized controlled trials (RCT) comprising 1,600 patients undergoing isolated F&A surgery found a rate of VTE of 8.3% among patients with chemoprophylaxis as compared to 11.7% without (relative risk [RR] 0.72, 95% confidence interval [CI] 0.55-0.94, p = 0.02)23. It concluded that, while chemoprophylaxis is efficacious, “event rates are low and symptomatic events are rare”. On the other hand, the authors highlight that the average age of patients in all six RCT was < 50 years. Separately, all six studies excluded patients with a prior history of VTE. Both are likely contributing risk factors for VTE after F&A surgery, limiting the ability to extrapolate their findings to broader populations.
In summary, there is insufficient data to characterize F&A surgical procedures as either major or non-major as this pertains to the risk of postoperative VTE. Certain diagnoses such as achilles rupture do seem to demonstrate a higher rate of VTE, but patient risk factors are especially critical as compared to patients undergoing THA and TKA or HFS. Large scale, prospective, RCT are necessary to define subpopulations of patients at heightened risk, as well as to elucidate the relative utility of various chemoprophylactic strategies.
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2. Falck-Ytter Y, Francis CW, Johanson NA, et al. Prevention of VTE in orthopedic surgery patients: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest. 2012;141(2 Suppl):e278S-e325S. doi:10.1378/chest.11-2404
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