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General Orthopaedics: C. Howie, H. Hughes, A. C. Watts Scottish Arthoplasty Project Venous thromboembolism associated with hip and knee replacement over a ten-year period: A POPULATION-BASED STUDY J Bone Joint Surg Br 2005; 87-B: 1675-1680 [Abstract] [Full text] [PDF]

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Colin R Howie   (7 February 2006)

No difference in mortality with increased use of chemothromboprophylaxis

K C Kong   (12 December 2005)

Author's reply: 7 February 2006
Colin R Howie, Consultant Orthopaedic Surgeon New Royal Infirmary of Edinburgh Send letter to journal: Re: Author's reply: colin.howie{at}luht.scot.nhs.uk Colin R Howie	Sir, We welcome the comments of Dr K.C. Kong. The main issue which he identifies, well recognised by epidemiologists, is the distinction between efficacy and effect. Trials of thromboprophylaxis adopt surrogate endpoints, in many cases demonstrating adequate efficacy - a reduction in the primary endpoint of radiographically-proven venous thromboembolism (VTE) at the time of discharge. However, population studies such as ours, looking for an effect of treatment (or in this case prophylaxis) on the overall incidence of an event, fail to show any significant impact. A possible reason for this is that confounding variables are not controlled in the same way in the population as they may be in a randomised controlled trial. In addition, the present study is unusual in the length of follow-up of cases after discharge. Most randomised trials follow patients to cessation of chemoprophylaxis. This will fail to identify cases of VTE occurring after the cessation of chemoprophylaxis. In our study most patients suffered their thromboembolic event after discharge when presumably conventional prophylaxis would have been discontinued. Analysis has been performed on the length of hospital stay for lower limb arthroplasty in Scotland between 1995 and 2004.1 This has determined a significant reduction in length of stay for both primary hip and knee arthroplasty patients from a median stay of approximately 14 days to 8 days. We are not aware of any studies that demonstrate convincing evidence that such a reduction will decrease the incidence of VTE. In our cataract group we were comparing an in-patient group to an ambulatory(day-case) group. Intuitively this should have a more significant effect on VTE. C.R. Howie, Consultant Orthopaedic Surgeon, New Royal Infirmary of Edinburgh, Edinburgh, UK. 1.Scottish Arthroplasty Project. Annual Report 2005. http://www.show.scot.nhs.uk/arthro/Reports/Scottish_Arthroplasty_Final_Report_2005_Web.pdf (accessed 07/02/06).
No difference in mortality with increased use of chemothromboprophylaxis 12 December 2005
K C Kong, Consultant Orthopaedic Surgeon Send letter to journal: Re: No difference in mortality with increased use of chemothromboprophylaxis kck{at}doctors.org.uk K C Kong	Sir, I read this article with interest. The authors have found no evidence of improvement in the incidence of venous thromboembolism or of fatal pulmonary embolism with the increased use of DVT chemoprophylaxis in hip and knee arthroplasty. The authors suggest that their data do not imply that anti-thrombotic prophylaxis and earlier mobilisation regimens have no effect. Their data must also imply that the ever-increasing use of chemoprophylaxis has made no difference to the rate of fatal pulmonary embolism. Is the data on length of stay for the hip and knee replacement procedures available over the ten-year period? Their data on day-case and in-patient cataract surgery have shown a significant difference in the venous thromboembolic rate with early mobilisation and discharge. Early post-operative mobilisation after hip and knee replacements has been accepted as the reason for the decrease in incidence of venous thromboembolic disease. Is it possible therefore, with the data available so far, that we need to pause and review our continuing use of routine DVT chemoprophylaxis for hip and knee replacement surgery? K.C. KONG, Consultant Orthopaedic Surgeon