***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: BACKGROUND Warfarin , which requires coagulation monitoring , is associated with relatively high rates of thromboembolism despite providing adequate prophylaxis . This study compared an oral direct thrombin inhibitor , ximelagatran , with warfarin in order to evaluate the safety and efficacy of the medication for the prevention of venous thromboembolism in patients undergoing total knee arthroplasty . METHODS Following surgery , patients were r and omly assigned to fixed-dose oral ximelagatran ( 36 mg twice daily ) or warfarin ( target international normalized ratio , 2.5 ) , both administered for seven to twelve days in a double-blind , double-dummy design . Warfarin was initiated on the evening of the day of surgery , and ximelagatran , on the morning after surgery . The primary efficacy end point was the incidence of asymptomatic deep-vein thrombosis determined by bilateral venography , objective ly confirmed symptomatic deep-vein thrombosis or pulmonary embolism , and death from all causes during treatment . RESULTS Adequate venograms or confirmed symptomatic events ( efficacy population ) were obtained for 1949 patients .  Venous thromboembolism and death from all causes occurred in 22.5 % ( 221 ) of 982 ximelagatran-treated patients and in 31.9 % ( 308 ) of 967 warfarin-treated patients ( p < 0.001 ) . Proximal deep-vein thrombosis and pulmonary embolism were observed in 3.1 % ( thirty ) and 0.2 % , respectively , of the patients in the ximelagatran group and in 3.4 % ( thirty-three ) and 0.4 % , respectively , of the patients in the warfarin group . The six deaths from all causes included 0.3 % ( four ) of the ximelagatran-treated patients and 0.2 % ( two ) of the warfarin-treated patients . Major bleeding was noted in 1 % ( twelve ) of the ximelagatran-treated patients and in 0.4 % ( five ) of the warfarin-treated patients ( p = 0.09 ) . CONCLUSIONS Oral ximelagatran ( 36 mg twice daily ) , administered without coagulation monitoring or dose adjustment and started the day after total knee arthroplasty , demonstrates superior efficacy compared with warfarin prophylaxis , with no wound complications and no significant difference with respect to bleeding events , although the rate of major bleeding events was greater with ximelagatran than with warfarin . LEVEL OF EVIDENCE Therapeutic Level One hundred forty-nine consecutive patients requiring lower extremity total joint arthroplasty were r and omized to either coumadin ( 52 patients ) or intermittent pneumatic compression ( 48 patients ) as prophylaxis against deep vein thrombosis ( DVT ) .  Forty-nine patients were excluded . When fully ambulatory , the presence or absence of DVT was diagnosed by ascending venography ( 90 % of patients ) , nuclear venography , venous dopplers , or impedence plethysmography . The two groups were similar in average age ( 64 years ) , indication for arthroplasty ( pain because of arthritis in 90 % ) , gender ( 98 % male ) , and average number of risk factors ( 2.4 ) . Twenty-five percent of patients on coumadin and 25 % of patients on intermittent pneumatic compression ( IPC ) developed DVT .  IPC was more effective than coumadin following primary total hip arthroplasties ( THAs ) ( 16 % versus 24 % incidence DVT ) ; coumadin was more effective than IPC following primary total knee arthroplasties ( TKAs ) ( 19 % versus 32 % incidence of DVT ) . DVT developed in 36 % of patients following revision arthroplasty . Seventy-five percent of all thrombi were proximal . Both IPC and coumadin were found to be safe ; there was no increased perioperative bleeding in the coumadin group . Of three postoperative deaths , one was possibly due to pulmonary embolism ( PE ) The effect of the pneumatic tourniquet on the incidence of postoperative deep venous thrombosis  is uncertain . We carried out a controlled study comparing the incidence of  deep venous thrombosis  when a tourniquet was used with the incidence when a  tourniquet was not used . Thrombosis was detected by radioisotope venography . The results of the study showed no difference in incidence and we concluded that the pneumatic tourniquet has no influence on the formation of a thrombus in a deep vein In a r and omized , prospect i ve trial of 100 patients , we have studied the safety and efficacy of warfarin sodium in comparison with that of dextran 40 in the prevention of  venous thrombosis in patients at high risk for deep vein thrombosis after elective total hip or knee replacement .  Warfarin was given in a new two-step regimen design ed to avoid bleeding complications while still preventing venous thrombosis . A low dose of warfarin was started ten to 14 days preoperatively , and the prothrombin time was regulated to between 1.5 and 3 seconds longer than control at the time of surgery ; immediately after surgery , the dose was increased to prolong the prothrombin time to 1.5 times control . The overall incidence of venous thrombosis as documented by venography was less in the 53 patients treated with warfarin than in the 37 treated with dextran ( 21 % v 51 % ) , as was the incidence of thrombi in the femoral or popliteal veins ( 2 % v 16 % ) . Objective measures of blood loss showed no difference between patients treated with warfarin or dextran , and excessive postoperative bleeding was infrequent and similar in both treatment groups . This study demonstrates that two-step warfarin therapy provides highly effective prophylaxis of postoperative venous thrombosis after elective hip or knee prosthetic surgery without excessive risk of perioperative bleeding The authors undertook a r and omised prospect i ve study to investigate the contribution of thigh tourniquets to the formation of intra-operative venous emboli during lower limb surgery . Patients were r and omised to have a thigh tourniquet or no tourniquet and transoesophageal echocardiography was used to detect embolic signals in the right heart during and after knee arthroscopy . Three physicians blinded to patient demographics and tourniquet status separately assessed videotapes of the echocardiograms for evidence of emboli . Of the 32 patients r and omised , 18 underwent knee arthroscopy with and 14 without tourniquet .  Emboli were seen in 72 % ( 95 % CI 55 to 84 ) of patients , in 14 patients with tourniquet and in 9 patients without tourniquet . There was an estimated 13 % greater incidence of emboli in the tourniquet group compared to the non-tourniquet group , a difference which was not statistically significant ( Fisher 's Exact Test , p = 0.45 ) . No patients suffered symptoms or signs attributable to a pulmonary embolus We assessed the safety and efficacy of the novel low molecular weight heparinoid Lomoparan ( Org 10172 ) for the prevention of deep-vein thrombosis in patients undergoing elective total hip replacement in a r and omized , placebo-controlled , double-blind trial in 197 consecutive patients . The heparinoid ( 750 anti-factor Xa-units , s.c . , b.i.d . ) was administered to 97 patients and 99 patients received placebo .  Study medication was started preoperatively and continued for 10 days . Efficacy was assessed by bilateral phlebography  at day 10 , postoperatively . The incidence of deep-vein thrombosis was 56.6 % and 15.5 % respectively in the placebo and heparinoid treated patients ( incidence reduction : 74 % ; P less than 0.001 ) . This reduction was observed both for proximal-vein thrombosis ( 25 % to 8 % ; P less than 0.005 ) and isolated calf-vein thrombosis ( 31 % to 7 % ; P less than 0.001 ) . No major hemorrhage was observed . The number of red-cell units transfused and drain-fluid loss were comparable for the two study groups . Six patients in the heparinoid group and none in the control group developed minor wound hematomas ( P less than 0.05 ) . During an 8-week post-discharge follow-up period three patients with a normal venogram at day 10 developed clinical ly apparent venous thromboembolism , which was confirmed by objective testing . All three patients belonged to the heparinoid-treated group . We conclude that 750 anti-factor Xa units Org 10172 s.c . twice daily starting preoperatively is safe and effectively reduces early deep-vein thrombosis following elective total hip replacement . Further studies on the incidence of post-discharge thromboembolism are required The scientific community 's quest for unbiased research received a strong boost from a recent policy amendment on r and omised controlled trials ( RCTs ) in this journal . Henceforth , the status of allocation concealment will be clearly indicated in the abstract s along with that of blinding . Thus , readers will have additional information by which to judge the internal validity of trials . In this editorial I address the background and rationale for these enhancements . R and om allocation to intervention groups remains the only method of ensuring that the groups being compared are on an equivalent footing at the outset of the study , thus eliminating selection and confounding biases . This has allowed RCTs to play a key part in advancing medical science . The success of r and omisation depends on 2 interrelated processes.1 , 2 The first entails generating a sequence by which the participants in a trial are allocated to intervention groups . To ensure unpredictability of that allocation sequence , investigators should generate it by a r and om process . The second process , allocation concealment , shields those involved in a trial from knowing upcoming assignments in advance.3 , 4 Without this protection , investigators and patients have been known to change who gets the next assignment , making the comparison groups less equivalent.5 , 6 For example , suppose that an investigator creates an adequate allocation sequence using a r and om number table . However , the investigator then affixes the list of that sequence to a bulletin board , with no allocation concealment . Those responsible for admitting participants could ascertain the upcoming treatment allocations and then route participants with better prognoses to the experimental group and those with poorer prognoses to the control group , or vice versa . Bias would result . Inadequate allocation concealment also Tourniquet time and its relationship to blood loss and deep vein thrombosis were studied in 80 cases of unilateral total knee arthroplasty . These data were part of a prospect i ve multicenter double-blind study on thromboprophylaxis for knee surgery . This study reports on the cases done at one institution in which the tourniquet was used in three different ways : group 1 ,  no tourniquet use ; group 2 ,  limited tourniquet use for cementing time only ; group 3 , tourniquet use throughout the whole case .  Blood loss was significantly related to tourniquet time ( P = .0001 ) . The incidence of deep vein thrombosis was not related to the tourniquet group ( P = .9 ) We performed a prospect i ve r and omized clinical study to determine whether use of a thigh tourniquet influences the incidence of deep venous thrombosis . The lower limbs of patients who were scheduled for elective surgery on the fore part of the foot were r and omized and assigned to one of three treatment categories : Group I , no tourniquet ; Group II , exsanguination by an Esmarch b and age before tourniquet application ; and Group III , exsanguination by elevation of the extremity prior to application of a tourniquet . The 117 limbs of seventy-one patients included in this study were evaluated preoperatively and twenty-four and seventy-two hours postoperatively with 125I-labeled fibrinogen , and preoperatively and seventy-two hours postoperatively with  Doppler ultrasound studies and phleborheography .  The findings in all of the Doppler ultrasound studies and all of the phleborheograms were normal . Two of the 125I-fibrinogen studies were positive , but subsequent contrast venography revealed that these were false-positive findings . We therefore concluded that the use of a thigh tourniquet does not increase the risk of deep venous thrombosis in patients who have had an operation on the fore part of the foot The effects of using a tourniquet during total knee arthroplasty were studied in 80 patients r and omly allocated to two groups , either with or without a tourniquet . The groups were similar in mean age , gender , preoperative knee score and radiographic grading and the patients were all operated on by the same surgeon using one type of prosthesis . There was no significant difference between the two groups in operating time or total blood loss but postoperative pain was less in the patients in whom a tourniquet had not been used . They achieved straight-leg raising and knee flexion earlier and had fewer superficial wound infections and deep-vein thromboses . Total knee arthroplasty can be safely performed without the use of the tourniquet with the benefit that several adverse effects associated with its use can be avoided OBJECTIVE To compare efficacy , safety , and feasibility of adjusted-dose oral anticoagulants ( OAC ) versus fixed-dose subcutaneous low molecular weight heparin ( LMWH ) for the prevention of deep venous thrombosis ( DVT ) in 
    Output:
    
The incidence of DVT in patients undergoing elective TKA appears to have declined in patients receiving warfarin thromboprophylaxis