In this study the authors determine whether isolated lower limb injuries treated operatively cause a significant risk of deep vein thrombosis (DVT), and whether that risk can be reduced by the administration of low-molecular-weight-heparin (LMWH) thromboprophylaxis. This is an important question, for two opposing reasons. Firstly, thromboprophylaxis with a chemical agent carries a theoretical risk of bleeding which may provoke not only wound failure but also compartment syndrome. Secondly, safely-avoidable thromboembolism carries a personal morbidity to the patient and a cost to the health care system.
The authors’ data suggest that the benefits of thromboprophylaxis may be limited, in as much as they could not demonstrate a significant reduction in the frequency of venographic DVT. Nor, however, did they find that chemical thromboprophylaxis was associated with bleeding complications. Their data confirm the existing guideline recommendations from both the American College of Chest Physicians1 and the International Consensus Statement2 that thromboprophylaxis should not be routinely given to those with isolated lower limb fractures but that thromboprophylaxis should be considered for those with additional risk factors.
This study is underpowered because it was stopped well before an adequate sample size was reached. The data are consistent with a 30% reduction in venographic DVT in those given LMWH. This is perhaps unlikely to reflect in a clinically-relevant (or cost-effective) improvement for most patients. However, the authors have excluded, for correct ethical reasons, those with the most potent risk factors - a personal history of thromboembolism and a delay to mobilisation. It would be reasonable to give LMWH to patients with these risk factors as the chance that the potential 30% reduction reduces their personal risk of thrombosis is probably greater than the chance of undue risk or unwarranted cost.
The study also produces other interesting data. A total of 20% to 25% of the venographic thrombi were on the unoperated leg. A similar proportion is found after joint replacement surgery. This reflects the generalised thrombophilia that is induced by trauma and surgery (rather than the local stasis and venous manipulation in the affected leg). The duration of this increased generalised thrombophilia after trauma is not known which means that the required duration of prophylaxis, in those deemed at risk, is not known either. In hip arthroplasty that risk continues for at least four weeks and it may be that in subsets of the trauma group, extended duration prophylaxis is needed.
As ever, a good randomised trial such as this generates the inevitable conclusion that more epidemiological data and subsequent trials are needed.
1. Geerts WH, Bergqvist D, Pineo GF, et al. Prevention of venous thromboembolism: American College of Chest Physicians evidence-based clinical practice guidelines (8th edition). Chest 2008;133(Suppl):381S-453S.
2. Cardiovascular Disease Educational and Research Trust, Cyprus Cardiovascular Disease Educational and Research Trust; European Venous Forum, et al. Prevention and treatment of venous thromboembolism. International Consensus Statement (guidelines according to scientific evidence).
Int Angiol 2006;25:101-61.
Warwick D, Reader in Orthopaedic Surgery
Southampton, United Kingdom