Incidence of DVT has been examined in-depth in the literature with the incidence in patients with acute SCI to be very high, more than 50% in early prospective studies (Joffe 1975; Todd et al. 1976; Brach et al. 1977; Rossi et al. 1980; Becker et al. 1987). However, more recent and widespread reports, according to Aito et al. (2000), Li et al. (2012), and Sasa et al. (2012) place the incidence of DVTs at between 10% and 30%.
Incidence rates have been shown to depend on the nature of the SCI. Verschueren et al. (2011) noted that 9.8% of non-traumatic SCI patients and 22.8% of traumatic SCI patients had DVTs. No significant difference has been noted in the incidence of DVT based on AIS scores (p=0.58, Sugimoto et al. 2009). However, the time post SCI seems to impact DVT incidence. Rates of DVTs are highest two to three weeks after SCI (Hagen et al, 2012; Lo et al. 2013; Thumbikat et al. 2002) and there is a reoccurring spike three months post SCI (Hagen et al, 2012; Thumbikat et al. 2002); during the chronic phase, the incidence of thromboembolism is reported to be less than 2% (Hagen et al, 2012).
In an analysis by Cao et al. (2013) examining risk factors for mortality, the authors did not find that DVT was significantly associated with future mortality. The study was based on evidence from 22 studies and provides insight into the methodological issues noted by studies when reporting incidence rates. Current findings suggest that early recognition of DVT and successful treatment are necessary in reducing the likelihood of mortality.
The high risk of DVT in acute SCI patients is due to the simultaneous presence of three factors of Virchow’s triad: hypercoagulability, stasis, and intimal (inner vessel layer) injury (Aito et al. 2000). Venous thromboembolism usually begins with a calf DVT (Nicolaides et al. 1971; Philbrick et al. 1988; Cogo et al. 1998). Approximately 20% of DVTs extend into the proximal veins (Kakkar et al. 1969; Lagestedt et al. 1985; Brandstater et al. 1992); over 80% of symptomatic DVTs involve the popliteal or more proximal veins (Kearon et al. 1998). Non-extending distal (i.e., calf) DVTs rarely cause PEs and as such are rarely worrisome (Kakkar et al. 1969), although they may account for over 80% of the incidence of DVT (Germing et al. 2010). Proximal (i.e., knee or above) DVTs often lead to PEs and are a cause for concern (Kakkar et al. 1969). Selassie et al. (2013) noted that patients who developed a pulmonary embolism had a twofold increase in the risk of in-hospital death compared to those who did not develop a DVT.
Pulmonary emboli (PE) are not uncommon post SCI and most are asymptomatic or unrecognized. Symptomatic PEs are large and if they are fatal, death occurs within a few minutes.
Deep venous thrombosis is common in SCI patients not receiving prophylactic treatment.
Deep venous thrombosis is common in spinal cord injured patients not receiving prophylaxis.