Orthopedics

The Risk of Venous Thromboembolism in the Orthopedic Patient: Epidemiological and Physiological Data

Guy D Paiement, MD; Cerrah Mendelsohn, BA

Abstract

Venous thromboembolism is responsible for 500,000 deaths annually in industrialized countries. It is probably the most common preventable cause of death in elective orthopedic surgery patients. Rates of deep vein thrombosis (DVT) and fatal pulmonary embolism (PE) in unprotected orthopedic patient populations are high. The overall DVT rate is >40% in patients undergoing hip or knee arthroplasty or suffering from multiple injuries. The proximal DVT rate for these patients is ≥15%, and the fatal PE rate is ≥1%. Risk factors associated with venous thromboembolism are related to the vascular injury, activation of blood coagulation, and venous stasis. Lower extremity orthopedic procedures carry a risk greater than that of surgery itself. Thus, orthopedic patients are at high risk for venous thromboembolic conditions. A systematic assessment of this risk should be performed in every patient, and an appropriate management plan should be implemented.

Abstract

Venous thromboembolism is responsible for 500,000 deaths annually in industrialized countries. It is probably the most common preventable cause of death in elective orthopedic surgery patients. Rates of deep vein thrombosis (DVT) and fatal pulmonary embolism (PE) in unprotected orthopedic patient populations are high. The overall DVT rate is >40% in patients undergoing hip or knee arthroplasty or suffering from multiple injuries. The proximal DVT rate for these patients is ≥15%, and the fatal PE rate is ≥1%. Risk factors associated with venous thromboembolism are related to the vascular injury, activation of blood coagulation, and venous stasis. Lower extremity orthopedic procedures carry a risk greater than that of surgery itself. Thus, orthopedic patients are at high risk for venous thromboembolic conditions. A systematic assessment of this risk should be performed in every patient, and an appropriate management plan should be implemented.

Venous thromboembolism is a pressing public health problem that is responsible for about 500,000 deaths each year in industrialized countries. Estimates indicate that half of these people have an otherwise good prognosis.1 Large autopsy series from general acute-care hospitals in many Western countries have consistently reported that pulmonary embolism (PE) is the primary cause of about 10% of all hospital deaths and is a contributing factor in another 10% of all hospital deaths.2-4

The epidemiology of venous thromboembolism is becoming more difficult to study due to the significant decrease of autopsy rates in most Western countries during the last decade. Venous thromboembolic disease is comprised of a cluster of related conditions of variable severity including the following: fatal PE; nonfatal symptomatic PE; asymptomatic PE; proximal deep vein thrombosis (DVT); distal DVT (symptomatic or not); and post-phlebitic syndrome.

Clinical signs and symptoms of some of these conditions, such as nonfatal PE or DVT, are non-specific, giving rise to a long differential diagnosis, especially in surgical patients. Clinical diagnosis of DVT is difficult. Even in high-risk patients, it has a sensitivity and a specificity of <50%. As a result, the true incidence of some of these conditions can only be estimated because accurate diagnosis requires invasive procedures.5

EPIDEMIOLOGY

Venous thromboembolism is an unusual condition in the community (Table 1). The incidence of symptomatic acute DVT is very low in those aged <50 years old in the general population. It increases to 5.11 episodes per year per 1000 males aged >50 years living in the city.3

Venous thromboembolism primarily occurs in hospitalized patients, generally as a complication of another clinical condition or its treatment. It is a major cause of death and morbidity in these hospitalized patients, and is probably the most common preventable cause of death in elective orthopedic surgery patients.

Many factors are contributing to the increasing prevalence of the problem. First, because age is such an important factor, demographics have a large influence on the magnitude of the problem. Increased life expectancy, improved living standards, and older people comprising a larger segment of the population, result in more orthopedic implant procedures every year. Recent United States statistics illustrate these global trends (Table 2).6 Moreover, an increasing proportion of these patients have other medical conditions that put them at even higher risk for problems.

Table

TABLE 1Prevalence (episodes per 1000 people per year) of symptomatic proximal DVT in the community

TABLE 1

Prevalence (episodes per 1000 people per year) of symptomatic proximal DVT in the community

Table

TABLE 2Number of orthopedic implant procedures performed in the United States during 1993 and 1994

TABLE 2

Number of orthopedic implant procedures performed in the United States during 1993 and 1994

Table

TABLE 3Disposition of joint replacement patients after discharge in the United States during the period 1981 to 1994

TABLE 3

Disposition of joint replacement patients after discharge in the United States during the period 1981 to 1994

Table

TABLE 4Thromboembolic disease rates in unprotected orthopedic populations

TABLE 4

Thromboembolic disease rates in unprotected orthopedic populations

In today's changing healthcare environment, delivery systems are under enormous pressure to become more "cost effective." This impetus to improve efficiency has translated into, among other things, shorter hospital stays and early transfer to facilities providing less intensive levels of care. These changes have had a particular impact on joint replacement patients. For example, in 1985, the average length of stay for knee replacement in the United States was 13.8 days; in 1995, it was 6.6 days. The disposition of these patients has also changed, with half of them going directly home after a short hospital stay (Table 3).6 This has effectively resulted in a decreased duration of inpatient prophylaxis. It is now unclear whether the entire postoperative risk period for thromboembolism is covered.

Venous thromboembolism is a major problem common to many categories of orthopedic patients. A review of the world literature from the last 30 years supports this observation and reveals the magnitude of the problem (Table 4).7-12 Some of these studies, especially those in joint-replacement patients, were performed several decades ago when postoperative rehabilitation protocols were more conservative and physical interventions, such as elastic stockings, were not routinely used. There is, however, no evidence of a spontaneous decrease in the rate of thromboembolic disease in unprotected patients. Indeed, a recent Canadian study of young multiple-trauma patients (Injury Severity Score >9) has demonstrated a 58% DVT rate using routine bilateral venography as a diagnostic end-point. It is estimated that 20% of the polytrauma patients who died >24 hours after their admission succumbed to PE.8

Recent advances in resuscitation techniques have increased the immediate survival of a large proportion of polytrauma patients. More rigid enforcement of road transport laws (ie, speed limitations, drunk driving) and more widespread use of safety devices (ie, helmets, seat belts, air bags) have reduced the incidence of immediately fatal injuries. As a result, more severely injured and immobilized patients survive, thereby increasing their risk of thromboembolic disease complications. It is important to keep in mind that only 30% of the patients found to have a fatal PE at autopsy have evidence of previous thromboembolic disease.6 This observation makes a strong case for prevention.

PATHOGENESIS

Blood coagulation is a very complex process that has not been completely elucidated. Clot formation and fibrinolysis are in dynamic equilibrium. This delicate balance prevents an individual from dying due to excessive bleeding or coagulation when the structural integrity of the vascular system is compromised. Numerous factors affect this delicate equilibrium, but they can be grouped under three general headings known as the Virchow triad: vascular injury (endothelial damage); activation of blood coagulation (hypercoagulability); and venous stasis.

Many risk factors have been associated with venous thromboembolism. Risk factors are conditions that have been found to statistically increase the risk of venous thromboembolism compared to the general population. Some of these factors are intrinsic to the patient (ie, age and inherited coagulation disorders), while other factors are more amenable to some form of control by the surgeon (ie, immobilization, estrogen supplementation). In addition, some factors have a synergistic effect on each other (ie, previous DVT and immobilization) while others have an additive effect (ie, age and protein C deficiency).

Lower extremity orthopedic procedures carry a risk of venous thromboembolism that is greater than the risk associated with the surgical procedure itself because of anatomical and physiological reasons. The following risk factors are specific to these procedures.

Twisting and kinking. The maneuver of twisting and kinking the common femoral vein during dislocation of the hip distends and breaks the endothelial intercellular bridges, exposing collagen and other pro-coagulant substances to the blood flow.

Retractors and surgical manipulations. Retractors and surgical manipulations may cause extensive venous endothelial damage.

Increase in thromboplastin antigens. A large increase in thromboplastin antigens has been observed with reaming and preparation of the bone (joint replacement) and impaction of various implants.

Heat. Heat generated during the polymerization of methacrylate may also cause some venous endothelial damage.

Immobilization and bed rest. Immobilization and bed rest, which are inevitable after many lower extremity orthopedic procedures, cause significant venous stasis.3,12,13

Patient-related factors are also important, and the effect of some of these factors on venous thromboembolism rates have been documented. Age, for example, has been well documented as a very significant risk factor for venous thromboembolism, even in the community. The incidence of thromboembolic disease increases progressively with age. Previous history of DVT or PE, metastatic malignancy, venous disease, tobacco use, and hormonal therapy (estrogen) are also significant for increased risk of venous thromboembolism in surgical patients. Research is being conducted regarding genetic risk factors such as resistance to activated protein C, a condition present in 2% to 5% of the healthy population. It is believed that this condition is associated with a seven-fold increase in the risk of DVT.

CONCLUSION

Venous thromboembolism is a serious public health problem. As the literature and statistics indicate, the majority of orthopedic patients are at significant risk of developing a venous thromboembolism that can ultimately result in death. With this knowledge, the strongest effort should be made to assess every orthopedic patient's risk for thromboembolic disease, and to implement an appropriate management plan for each patient to address the problem.

REFERENCES

1. Alpert JS, Dalen JE. Epidemiology and natural history of venous thromboembolism. Prog Cardiovasc Dis. 1994; 36:417-422.

2. Anderson FA, Wheeler HB, Goldberg RJ, et al. A population based perspective of the hospital incidence and case fatality rates of deep vein thrombosis and pulmonary embolism. Arch Intern Med. 1991; 151:933-938.

3. Bergqvist D, Linblad B. A 30-year survey of pulmonary embolism verified at autopsy: an analysis of 1,274 surgical patients. Br J Surg. 1985;72:105-108.

4. Morrell NP, Dunhill MS. The postmortem incidence of pulmonary embolism in a hospital population. Br J Surg. 1968; 55:347.

5. Goldhaber SZ, Hennekens CH, Evans DA, et al. Factors associated with correct antimortem diagnosis of major pulmonary embolism. Am J Med. 1982; 73:822-826.

6. Orthopedic Network News. Ann Arbor MI: Mendenhall Associates Ine; 1996; 7:1-5.

7. Coventry, MB, Nolan, BR, Beckenbaugh RD, et al. Delayed prophylactic anticoagulation: a study of results and complications in 2, 1 12 total hip arthroplasties. J Bone Joint Surg. 1973; 55 A: 1487-1492.

8. Geerts WH, Code KI, Jay RM, Chen E. Szalai JR A prospective study of venous thromboembolism after major trauma. N Engl J Med 1994;321:1601-1606.

9. Haake DA, Berkman SA. Venous thromboembolic disease after hip surgery, Clin Orthop. 1989; 242:212.

10. Johnson R, Green RJ, Charnley J. Pulmonary embolism and its prophylaxis following the charnley total hip replacement. Clin Orthop. 1977; 127:123-132.

11. Paiement GD, Schutzer SF, Wessinger SJ, Harris WH. Influence of prophylaxis on proximal venous thrombus formation after total hip arthroplasty. J Arthroplasty. 1992; 7:471-478.

12. Sevitt S, Ghallegher M. Venous thrombosis and pulmonary embolism: a clinical pathologic study in injured and burned patients. Br J Surg. 1961;45:475-489.

13. Planes A, Vochelle N, Fagola M. Total hip replacement and deep vein thrombosis: a venographic and necropsy study. J Bone Joint Surg. 1990, 72B:9-13.

TABLE 1

Prevalence (episodes per 1000 people per year) of symptomatic proximal DVT in the community

TABLE 2

Number of orthopedic implant procedures performed in the United States during 1993 and 1994

TABLE 3

Disposition of joint replacement patients after discharge in the United States during the period 1981 to 1994

TABLE 4

Thromboembolic disease rates in unprotected orthopedic populations

10.3928/0147-7447-19970202-05

Sign up to receive

Journal E-contents