Minor leg injuries associated with increased risk of venous thrombosis, study finds

Partial ruptures of either leg muscles or leg ligaments were more strongly associated with venous thrombosis compared to other injuries, such as sprains and contusions.

Minor leg injuries that do not require surgery, plaster casting or extended bed rest are still associated with an increased risk for venous thrombosis, according to a study by researchers in the Netherlands.

The association between leg injury and venous thrombosis was particularly strong in patients with a genetic predisposition to thrombosis, the study authors noted.

Frits R. Rosendaal, MD, PhD, and colleagues at Leiden University Medical Center conducted a large, population-based, case-control study evaluating risk factors and causes of venous thrombosis. They published their findings in Archives of Internal Medicine.

The study recruited all consecutive patients at six anticoagulation clinics who experienced a first episode of venous thrombosis from March 1999 through August 2004. The control group included either the partners of patients or individuals identified using random-digit-dialing.

All participants completed a standardized questionnaire to report injuries, surgical procedures, plaster casting and immobilizations for 1 year before the index date. They also reported sporting activities, standing height and weight, and family history of venous thrombosis, according to the study.

Investigators defined the index date as the date a thrombotic event was diagnosed or, for controls, as the date the questionnaire was completed.

After applying exclusion criteria, the study included 2,471 patients and 3,534 control subjects.

Overall, 289 patients (11.7%) and 154 controls (4.4%) sustained a minor injury within 3 months before the index date, the authors reported.

"Thrombosis was more strongly associated with injuries that occurred during the previous 4 weeks than with less recent injuries. Among patients, most injuries occurred in the 2 to 3 weeks before the venous thrombosis diagnosis, while fewer events occurred in the week directly before the venous thrombosis," the investigators wrote.

"Of the 289 patients with a minor injury, 237 (82%) had their injury located in the leg, compared with 78 of 154 injuries (50.6%) among controls. Therefore, thrombosis was more strongly associated with injury in the leg than with injury located in other body parts," they added.

Leg injuries were also mainly associated with a greater relative risk of an isolated deep venous thromboembolism (DVT), with an adjusted odds ratio (OR) of 6.3. However, there was also a greater relative risk for an isolated pulmonary embolism (PE), with an adjusted OR of 2.4, and for a combination of PE and DVT, with an adjusted OR of 5.3, according to the study.

Partial ruptures of either leg muscles or leg ligaments were more strongly associated with venous thrombosis compared to other injuries, such as sprains and contusions.

"Specific injuries most strongly associated with thrombosis were ruptures of the sural muscle ('tennis legs') and knee ligament ruptures, while knee and ankle sprains were associated to a lesser extent with venous thrombosis," the authors noted.

Investigators also found that, among individuals with a first-degree family member who had a history of venous thrombosis, leg injury was associated with an estimated 12-fold relative risk of venous thrombosis compared to those without such family history.

"This finding suggests a joint effect with genetic factors. The estimated relative risk in carriers of the factor V Leiden mutation with an injury compared with noncarriers without an injury was almost 50," the authors wrote.

For more information:
Van Stralen KJ, Rosendaal FR, Doggen CJM. Minor injuries as a risk factor for venous thrombosis. Arch Intern Med. 2008;168:21-26.