Is chronic spinal cord injury associated with increased risk of venous thromboembolism?

To determine the incidence of symptomatic thromboembolism in patients with chronic spinal cord injury, a retrospective review of patients followed in a Veteran's Affairs Spinal Cord Injury Unit was conducted. Followed for a mean of 13.7 years after injury, 287 patients were reviewed. Forty events were identified, an incidence of 10 percent. Thirty-three (83 percent) occurred in the first 6 months following injury. The remainder occurred at 1, 1.5, 7, 9, 10, 12, and 14 years after injury, an incidence of 0.17 percent per year. The incidence of clinically significant thromboembolism in spinal cord injury decreases dramatically after the first 6 months to a level similar to that in the general population (0.18 percent). Possible explanations for this include: 1) immobilization by itself may not be a risk factor for thromboembolism; 2) physiologic adaptations in the chronic state may protect against thromboembolism; and, 3) thromboembolism occurs, but remains subclinical in most patients.