Venous thromboembolism (VTE) can result in significant morbidity and mortality. Despite identification by healthcare initiatives as a preventable clinical event, data indicate that neither increased awareness nor more recent prophylactic regimens have resulted in a significant change to the overall incidence and mortality from VTE. Deep vein thrombosis (DVT) accounts for most thrombotic events, but prevention of clinically significant pulmonary embolus (PE) is the primary goal of prophylaxis. Various recommendations have been generated to help guide VTE prophylaxis in the orthopaedic patient1-5 (Table 1). Unfortunately, little high-level evidence is available on the topic, especially with regard to the orthopaedic trauma patient. In addition, there is little evidence to help practitioners decide which orthopaedic trauma patients require prophylaxis and the duration of treatment. Initiation of pharmacologic prophylaxis in the trauma patient must also balance the benefits of therapy with the risk of bleeding. The advent of more recent anticoagulants has increased the pharmacologic options available to the orthopaedic surgeon, but their comparative efficacy has been incompletely evaluated.
The incidence of DVT in trauma patients without prophylaxis is cited to be as high as 80%. Stannard et al6 reported that initiation of chemical prophylaxis in orthopaedic trauma patients reduced the overall rate of DVT to 11% and of nonfatal PE to 1%. The reported incidence of DVT varies with method of detection, mode of prophylaxis, location of thrombus, and sample size, thus resulting in a wide range of numbers in the literature. Interestingly, evidence of peripheral DVT by venous ultrasonography or postmortem analysis is not always present in those who develop a symptomatic PE. Although it has been thought that all PEs are the result of distal thrombi that travel proximally, the findings of Stannard et al6 question this relationship. The use of pharmacologic prophylaxis has been shown to significantly lower the rate of DVT formation, but PE-related morbidity and mortality remain high, indicating an important clinical disparity.
The development of VTE is not unique to any specific patient type or injury pattern. No one prophylactic protocol has been found to demonstrate superior results with regard to the reduction of both DVT and PE in hospitalized patients. Unfortunately, evidence has shown that even across surgical intensive care units at major academic medical institutions in the United States, adherence to VTE prophylaxis guidelines is poor.7 As such, the Agency for Healthcare Research and Quality now ranks VTE prophylaxis as among the most important interventions to improve patient safety.8 Despite all the attention given to preventing VTE in hospitalized trauma patients, however, there is little in the way of strong evidence-based recommendations to guide the orthopaedic surgeon.
Pathophysiology and Risk Factors
Virchow’s triad of venous stasis, endothelial injury, and hypercoagulability is traditionally considered the harbinger of thrombus formation. Major trauma is believed to lead to one, if not all three, risk factors. Specific risk factors, including but not limited to spinal cord injury, pelvic fractures, lower extremity fractures, high injury severity, and longer ventilation times, place these patients at increased risk for symptomatic VTE. Recent studies have explored the effects of circulating procoagulant and thrombogenic microparticles, as well as a decrease in antithrombin III levels, on thrombus formation in an effort to better understand the pathophysiology behind clot formation and embolization.9 Basic science investigators will continue to explore the potential modifiable factors involved in both in vitro and in vivo clot formation.
The diagnosis of VTE remains a challenge. Clot formation is often a clinically silent or subtle event. The Wells criteria have been used to determine the pre-test probability of PE before diagnostic testing is performed. The scoring system was first reported in nontrauma patients and has not been validated outside this population. Young et al10 recently evaluated alternative and standard interpretations of the Wells criteria in a large number of orthopaedic trauma patients and found no predictive relationship between the test scores and the development of PE.
Routine venous ultrasonography has been used in an effort to capture early peripheral DVT. A positive result obtained from a screening study performed in an asymptomatic person places the practitioner in a position to decide whether therapeutic anticoagulation is required. Although therapeutic anticoagulation may prevent progression of thrombotic disease, the physician and patient assume the responsibility of increased medical costs and the risk of bleeding. Recent literature has shown that sequential duplex ultrasonography screening does not decrease the rates of PE in orthopaedic trauma patients.11 In fact, recent recommendations from both the American Academy of Orthopaedic Surgeons and Orthopaedic Trauma Association recommend against the use of duplex ultrasonography to screen asymptomatic orthopaedic joint arthroplasty and trauma patients, respectively, for peripheral VTE.1,3 Use of duplex ultrasonography is therefore recommended when the physician identifies patient or injury-related risk factors or specific clinical signs or symptoms of VTE.
CT pulmonary angiography is used as a definitive diagnostic tool when PE is suspected; it has no role as a screening tool. The examination is expensive and requires the use of potentially nephrotoxic intravenous contrast material. The study has the ability to locate and characterize clots but cannot determine or predict their clinical significance. For this reason, injudicious use can result in unnecessary cost, morbidity, and use of pharmacologic anticoagulation.
A recent systematic review demonstrated that both pharmacologic and mechanical prophylaxis reduces the risk of DVT in trauma patients.5 The decision to begin pharmacologic prophylaxis must frequently balance the benefits of early therapy with the concern for complications related to bleeding, specifically in the setting of concurrent solid organ, intracranial, or spinal injury. A recent study by Phelan et al12 evaluated early versus delayed administration of VTE prophylaxis in patients, with a subset of patients with small traumatic brain injuries who had stable head CT scans 24 hours following injury. The authors found that early use of enoxaparin did not place patients at increased risk for intracranial bleeding compared with placebo.
A recent study looking at complications associated with anticoagulant administration in orthopaedic trauma patients with diagnosed pulmonary emboli demonstrated a 10% and 6% rate of surgical site and “other” site bleeding, respectively. The authors did identify the various anticoagulants used but did not stratify results between each type. The authors concluded that anticoagulant use in the orthopaedic trauma patient with a diagnosed PE should take into consideration the risk and size of the PE and that further work was needed to refine treatment algorithms.13
Nonpharmacologic interventions include inferior vena cava filters and static compressive or intermittent pneumatic compression devices. Vena cava filters are frequently placed in high-risk patients when pharmacologic prophylaxis is contraindicated. A recent systematic review and meta-analysis by Haut et al14 demonstrated a consistent reduction in PE and fatal PE with inferior vena cava filter placement, without reduction in DVT or mortality. Compression stockings and intermittent pneumatic compression devices are most often used in conjunction with pharmacologic prophylaxis. The National Institute for Health and Clinical Excellence guidelines recommend the use of combined mechanical and pharmacologic agents.15 The use of compressive stockings alone has been shown to reduce the risk of DVT compared with no intervention; their addition to pharmacologic prophylaxis resulted in overall lower DVT rates but did not affect the development of PE.5
The duration of prophylaxis in orthopaedic trauma patients is also poorly defined. Sobieraj et al8 compared standard versus prolonged thromboprophylaxis after total knee and hip replacement surgery, as well as hip fracture surgery, in a recent systematic review. Although prolonged therapy was beneficial (ie, reduction in PE and symptomatic VTE) in patients following total hip arthroplasty, data were insufficient to draw the same conclusions in hip fracture patients. Further studies are needed to identify the optimal therapy and duration of prophylaxis in orthopaedic trauma patients with the various treatment options available.
Standard pharmacologic interventions include low-dose unfractionated heparin, low-molecular-weight heparin (LMWH), such as enoxaparin and dalteparin, as well as aspirin and warfarin. These medications have been well studied, but new drugs are being developed and tested. The ultra-LMWH semuloparin has been recently studied in both joint arthroplasty and hip fracture patients.16 Another recent study assessed the efficacy and risk profile of the factor Xa inhibitor rivaroxaban in patients with hip and lower extremity fractures. The authors found no difference in regard to major bleeding events between patients treated with LMWH and Xa inhibitors, but they did report statistically lower rates of symptomatic VTE and distal VTE in patients treated with rivaroxaban.17 Unfortunately, the few studies evaluating these more recent medications specifically in orthopaedic trauma or fracture patients are insufficient to draw definite conclusions from; more data are needed to evaluate their efficacy and adverse effect profiles. The ideal prophylactic medication must demonstrate superior efficacy in clot prevention, be easy to administer and reversible, require minimal follow-up, be available at a low cost, and be associated with minimal unwanted events.
Lower Extremity Trauma
VTE can occur following isolated lower extremity injuries, including those treated without surgery. Small clinical series show that the rate of DVT with lower extremity cast and brace immobilization is between zero and 17%; in these series, all diagnoses were made by screening asymptomatic patients.18 A recent Cochrane review demonstrated that outpatient prophylactic LMWH significantly reduced or eliminated the number of VTE which occurred during cast or brace immobilization.18 Significant variation exists in the use of VTE prophylaxis in immobilized patients. In a study by Batra et al,19 62% of physicians reported using no prophylaxis at all and only 41% reported continuing prophylaxis until immobilization was finished.
Multiple studies have evaluated VTE in patients following lower extremity trauma. Sems et al20 reported a DVT incidence of 2.1% in patients treated with a joint-spanning external fixator who had been placed on LMWH within 24 hours of admission. A retrospective review of more than 57,000 ankle fractures treated with surgery revealed a 0.05% readmission rate as a result of DVT; no record of the use or type of DVT prophylaxis was recorded in this study.21 Smith et al22 reported in a prospective study of patients with operative hip and femur fractures that 10% developed a DVT. All patients had been treated initially with pharmacologic prophylaxis. The study also showed that delay in surgical care increased the rate of DVT. Pelvic and acetabular injuries have historically been associated with increased rates of VTE. A large systematic review by Slobogean et al23 on thromboprophylaxis in pelvic and acetabular surgery concluded that strong evidence-based recommendations could not be made based on the available literature. In their review, early administration of LMWH was the only intervention that decreased both DVT and PE. The preference of these authors is to manage patients with an isolated lower extremity injury with both mechanical and pharmacologic prophylaxis while the patients are hospitalized. Continuation of therapy following discharge is based on each patient’s risk factors and degree of mobility.
Upper Extremity Trauma
Few prospective studies have evaluated the prevalence of VTE in patients with isolated fractures of the upper limb. Despite limited evidence, the incidence of VTE in patients who have sustained an isolated upper extremity injury is estimated to be 1% to 5%. A recent retrospective study by Hsu et al24 at a level I trauma center showed that the rate of VTE in upper extremity trauma patients was 4.95%, identical to the rate of VTE in all trauma patients in the study. In addition, when upper extremity surgery for acute trauma is compared with elective surgery, no significant increase in VTE rates has been found. These data suggest that not only is the presence of upper extremity trauma not an independent risk factor for VTE, but also that the presence of upper extremity trauma does not necessitate more aggressive anticoagulation, nor does it confer additional risk of VTE beyond those risks stemming from individual patient-related factors. The authors suggest that patients with upper extremity trauma not receive additional VTE prophylaxis unless they have increased risk factors, such as positive history of VTE, a known clotting disorder, concurrent injuries that would otherwise require VTE prophylaxis, or a known catheter-related upper extremity VTE that may necessitate treatment.
Patients who have sustained traumatic orthopaedic injuries are at risk for developing VTE. Prevention of VTE, specifically symptomatic and fatal PE, is a preventable cause of morbidity and mortality. Despite various attempts at early VTE detection and pharmacologic programs, rates of symptomatic and fatal PE remain relatively unchanged. Although administration of pharmacologic prophylaxis has been shown to decrease the development of DVT, there is little consensus on the optimal prophylactic regimen. The American Academy of Orthopaedic Surgeons has provided recommendations for VTE prophylaxis in the orthopaedic patient, but there is limited high-quality evidence available to help formulate these guidelines.
We recommend initiation of VTE prophylaxis as early as possible in patients following orthopaedic trauma, with consideration given to the severity of injury, associated nonorthopaedic injuries, and overall risk-benefit assessment. LMWH has been recommended by both the Orthopaedic Trauma Association and well as the American College of Chest Physicians. The use of mechanical prophylaxis should be used when possible to supplement any regimen. Duration of therapy is based on the severity of the injury as well as the patient’s associated VTE risk factors. Further studies and multicenter trials are needed to help refine these guidelines.
Evidence-based Medicine: Levels of evidence are described in the table of contents. In this article, reference 6 is a level I study, reference 12 is a level II study, and reference 13 is a level III study.
References printed in bold type are those published within the past 5 years.
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