Abstract
Introduction and Aims: While clinical variables are considered important risk factors for post-arthroplasty VTE, the role of common genetic thrombophilic factors is less clear. The aims of this study were to determine if common thrombophilic genetic polymorphisms are independent risk factors for VTE post-arthroplasty; and if clinical variables are equally or more important.
Method: A prospective study of consecutive patients undergoing elective total hip or knee arthroplasty at a single institution, involving two surgeons. Patients were interviewed to assess clinical risks. Pre-operative blood samples were taken for Factor V Leiden (FVL), Pro-thrombin G20210A (PTH) and Methylenetetrahydrofolate reductase C677T (MTHFR) testing. All patients received routine enoxaparin prophylaxis and compression stockings. Intermittent pneumatic calf compression was also used by one surgeon. Presence of DVT was assessed using bilateral lower limb duplex ultrasonography (seven ± two days post-operatively) in all patients and performed in a vascular laboratory. Symptoms suggestive of pulmonary embolism were investigated by ventilation/perfusion lung scanning.
Results: A total of 569 patients were recruited with a median age of 67 years (range 20–90). Osteoarthritis was the main surgical indication. The overall incidence of post-operative venous thromboembolism (VTE) was 26%. Of thromboembolic events, 15% VTE were proximal DVT; 84% VTE were distal DVT and only one percent were pulmonary emboli. Prevalence of the thrombophilic genotypes was: 4.6% (heterozygous FVL mutation); 2.1% (heterozygous PTH); and 10.4% (homozygous C677T MTHFR mutation). Using univariate analysis, older age (p < 0.0005), total knee arthroplasty (p < 0.0005), recent surgery (p = 0.002), general anaesthesia (p = 0.013), operation time in minutes (p < 0.0005) and use of blood transfusions (p < 0.0005) were significantly associated with post-operative DVT. None of the thrombophilic genotypes were found to be significantly associated with post-operative DVT, however the frequency of FVL and PTH was highest in patients with proximal DVT and total hip arthroplasty patients with DVT. In multivariate analysis of both genetic and clinical thrombophilic factors, only age (p=0.02) and total knee arthroplasty (p< 0.0005) were found to be significant independent risk factors for post-operative VTE.
Conclusion: We conclude that clinical factors such as age and type of surgery (total knee arthroplasty) are independent risks for post-operative VTE in patients undergoing lower limb arthroplasty. FVL, PTH and MTHFR are not significant risk factors for post-operative VTE and screening for these mutations is not indicated.
These abstracts were prepared by Editorial Secretary, George Sikorski. Correspondence should be addressed to Australian Orthopaedic Association, Ground Floor, The William Bland Centre, 229 Macquarie Street, Sydney, NSW 2000, Australia.
One or more of the listed authors are receiving or have received benefits or support from a recognised academic body for the pursuance of the study.
