Whither thromboprophylaxis after total hip replacement

The unwillingness of many orthopaedic surgeons to use prophylactic anticoagulant drugs in patients undergoing total hip replacement (THR) remains something of a mystery to non-surgeons. The reasons for this are probably complex, and undoubtedly vary from surgeon to surgeon, but it is clear that one important aspect is disagreement about the extent to which postoperative thromboembolism poses a significant hazard. The published assessments of risk of death from pulmonary embolism (PE) vary by at least an order of magnitude (below 0.1% to 1.0% or more), with some of the earlier literature quoting a rate of fatality after THR much higher than is experienced today. Opinions range from those who hold that it is close to malpractice not to use some form of prophylaxis, which has been demonstrated in good clinical trials to be effective, to those who maintain that there is no convincing evidence of the need for prophylaxis with anticoagulant drugs. Both these viewpoints seem extreme and, although no final answers are yet available, there is clearly a need for a reasonable compromise which will appeal to most clinicians. Two crucial issues need to be addressed. Is there still a small, but appreciable, morbidity and mortality from venous thromboembolism after THR? If there is, what is the best form of prophylaxis? The two methods currently favoured are anticoagulant drugs and mechanical methods to reduce stasis. Both of these raise further questions. If anticoagulants are used do the complications outweigh the benefits? If mechanical methods are employed, how good is the evidence that this non-pharmacological approach is effective? Retrospective studies have claimed that the incidence of PE is now much lower than is stated in the older literature because of modern surgical techniques, better anaesthesia and earlier mobilisation of patients. Such arguments are plausible, and probably true to some extent, but do they warrant the claim that the risk is now so low that routine prophylaxis is unnecessary? It is suggested that using demonstrable deep-vein thrombosis (DVT) as an endpoint in clinical trials tends to exaggerate the risk of clinically significant thromboembolism. Clearly, radiologically demonstrated DVT does not equate to subsequent clinically significant PE. Nevertheless, the presence of overt thrombosis, however demonstrated, must be considered to be a manifestation of a thrombotic state, which has the potential to cause serious illness. The fact that many postoperative DVTs undergo spontaneous thrombolysis, and small emboli are tolerated by the pulmonary circulation with minimal symptoms, are indeed important safety factors, but should they be relied upon? Patients undergoing THR may not have the profound hypercoagulability often associated with malignant disease, but inevitably there is considerable tissue damage, and these patients are usually Current concepts