Overall, DVT is considered to be a complication occurring at a variable rate in acute SCI, with incidence rates depending on several factors including diagnostic methods used, study population, characteristics (e.g., age, acuity of injury, location of SCI), associated risk factors, and modality of thromboprophylaxis (Chung et al. 2014; Merli et al. 1993). There are inconsistencies in the scientific literature regarding the incidence of this complication as most occurrences of DVT are asymptomatic. Thus, the use of various diagnostic imaging screening methods is of utmost importance as clinical criteria alone are insufficient (Meissner, 1998). However, the incidence of DVT varies even with the use of non-clinical methods of detection (Winemiller et al. 1999). Nevertheless, DVT in acute SCI has been reported as having the highest rate of incidence within the first 3 months following injury (Chung et al. 2014), with a variable incidence rate reported in older studies ranging from 49% to 100% during the first 12 weeks (Merli et al. 1993); however, most DVT events occur within the first 2 weeks (Chen & Wang, 2013; Merli et al. 1993). More recent reports place the incidence of DVT in individuals with acute SCI between 1.3% and 28%; this range is based on studies in which SCI individuals did not use any form of thromboprophylaxis, used only mechanical compression or were given an unspecified form of treatment (Aito, 2003; Do et al. 2013; Selassie et al. 2011; Sugimoto et al. 2009).
The formation of venous thrombosis has been reported to occur as early as 72 hours post injury, peaking between day 7 and 10, as detected by impedance plethysmography, venous flow dopplers, and lung scanning. However, this statistic is also based on some studies which did not indicate a specific method of assessment, and as such should be interpreted with caution (Merli et al. 1993). Using color duplex sonography, Germing et al. (2010) detected the formation of DVT even sooner, reporting that 38% of individuals in their study developed DVT within the first 36 hours after hospitalization following injury. However, the occurrence of DVT and PE is rare within the first three days after injury (Raslan et al. 2010). PE has also been reported to have the highest likelihood of occurrence within the first 3 months following SCI (Chung et al. 2014); however, fatal PEhas been found to be a rare occurrence after the initial 3 month duration following SCI (Sugimoto et al. 2009).Interestingly, some studies have shown that the incidence of DVT seems to be lower in Eastern (e.g., India and Pakistan) SCI populations compared to those in the West, possibly due to a difference in diet and genetic risk factors (Rathore et al. 2008; Saraf et al. 2007). Despite prophylaxis being widely used since the 1980s to prevent and treat occurrences of VTE, it still remains a major health complication for acute SCI individuals that results in significant morbidity and mortality (Furlan & Fehlings, 2007).