Abstract
Chemical prophylaxis is known to reduce the venographic prevalence of deep-vein thrombosis (DVT) after total knee replacement (TKR), but it is uncertain whether this affects the incidence of symptoms. Further analysis depends on the basic epidemiology of thromboembolic symptoms. We therefore studied the pattern of such symptoms in a consecutive series of 1000 patients with primary TKR, with particular reference to risk factors and prophylaxis.
We reviewed all the clinical records and contacted all the patients individually, noting risk factors, prophylaxis, symptomatic pulmonary embolus (PE) or DVT and its timing, death and its causes, and all complications. All the patients wore antiembolism stockings, 83% had regional anaesthesia and 33.9% had chemical prophylaxis.
One patient died from PE on the day of surgery, having had no prophylaxis giving a rate of 0.1% (95% CI 0.003% to 0.56%). Symptomatic, radiologically confirmed thromboembolism (VTE) was common with a rate of 10.6% (95% CI 8.7% to 12.5%). There was a similar incidence of VTE in those with and without chemical prophylaxis (10.1% v 10.5%, RR 0.96, NS). VTE was more common in patients with risk factors (15.1% v 9.5%, RR 1.59, p = 0.02) and tended to occur earlier in this group (median day of onset 5 v 7, p = 0.01). Chemical prophylaxis did not reduce the frequency of symptomatic thromboembolism in either those with risk factors (RR 0.81, p = 0.5) or those without them (RR 0.94, p = 0.8). Haematoma or wound dehiscence was more common in those having chemical prophylaxis (11.9% v 6.9%; RR 1.73 95% CI 1.16 to 2.60). Readmission for symptomatic, radio-logically confirmed thromboembolism involved 1.1% of patients (95% CI 0.55% to 2.1%). Four patients were readmitted with proven non-fatal PE and six with proven DVT (the latest on day 40).
Our results show that the main risk factor for thromboembolism was TKR itself; chemical prophylaxis did not reduce the incidence of symptomatic thromboembolism but gave an increased perception of side-effects. New prophylactic methods or combinations of methods are needed, with their efficacy compared by randomised controlled studies of both the clinical and the radiological effect.
