An interventional study of Apixaban and Rivaroxaban in Total Knee Arthroplasty and Venous Thromboembolism, sponsored by Military Hospital of Tunis. Recruiting at 1 site in Tunisia. Open to participants aged 18 Years to 80 Years. Per ClinicalTrials.gov, last updated 2026-10-16.
Sponsored by Military Hospital of Tunis · Not applicable, Interventional, and Prevention
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1. Brief Summary
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This study aims to compare three thromboprophylaxis regimens in adults undergoing primary total knee arthroplasty: rivaroxaban 10 mg once daily, apixaban 2.5 mg twice daily, and low-molecular-weight heparin (LMWH) once daily. The study will assess venous blood flow in the lower limbs using Doppler ultrasound and determine whether blood flow differs between the three treatment groups. Participants will be randomly assigned to one of the three treatment groups and followed for 28 days after surgery. Doppler ultrasound examinations will be performed at baseline and on Days 7, 15, 21, and 28. Additional assessments will include rehabilitation progress, postoperative bleeding, suspected venous thromboembolism, cardiovascular complications, and other postoperative complications. The study is being conducted at the Department of Anesthesiology, Principal Military Hospital of Instruction of Tunis.
Total knee arthroplasty is associated with a substantial risk of venous thromboembolism, and pharmacological thromboprophylaxis is routinely used after surgery. This study aims to compare three thromboprophylaxis strategies and their effects on postoperative venous hemodynamics following primary total knee arthroplasty.
Eligible adults undergoing elective primary unilateral total knee arthroplasty will be enrolled after providing written informed consent. Participants will be randomly assigned to one of three treatment groups: apixaban 2.5 mg twice daily, rivaroxaban 10 mg once daily, or weight-adjusted enoxaparin 40-60 mg once daily. According to the study protocol, patients receive an initial LMWH prophylactic treatment 6 hours after surgery and subsequently receive the randomized thromboprophylaxis regimen 24 hours after surgery. Treatment is planned for 14 days.
The primary objective is to compare peak systolic velocity (PSV) in major lower-limb veins between the three thromboprophylaxis groups using duplex Doppler ultrasound during the 28-day postoperative period. Additional Doppler parameters will include time-averaged mean velocity, vessel diameter, venous flow volume, respiratory phasicity, distal augmentation, and visible intraluminal sludging.
Secondary assessments will include postoperative rehabilitation, level of immobilization, articular stiffness, range of motion, static and dynamic pain, postoperative bleeding, anticoagulation-related adverse effects or overdose, suspected venous thromboembolism, return to the operating room, infections, and other postoperative complications.
Doppler assessments will be performed at baseline and on Days 7, 15, 21, and 28. The Doppler examiner will be blinded to the assigned anticoagulation regimen. Measurements will be performed using spectral Doppler ultrasound at the common femoral and popliteal veins.
The study plans to recruit at least 138 participants, with a minimum of 46 participants in each treatment group. The sample size was calculated to detect a 15% difference in the mean peak systolic velocity of the common femoral vein, with a two-sided alpha level of 0.05 and 80% statistical power.
708 studies on the registry are indexed under Venous Thromboembolism; 152 are open to participants now.
This study's planned enrollment of 138 is below the median of 257 across 390 interventional studies indexed under Venous Thromboembolism.
Browse Venous Thromboembolism studies →Military Hospital of Tunis is the lead sponsor of 13 studies on the registry; 2 are open to participants now.
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Exclusion Criteria:
Participants receive apixaban 2.5 mg twice daily for 14 days.
Drug: Apixaban
Participants receive rivaroxaban 10 mg once daily for 14 days.
Drug: Rivaroxaban
Participants receive enoxaparin 40-60 mg once daily, weight-adjusted, for 14 days.
Drug: Enoxaparin (LMWH)
Apixaban 2.5 mg twice daily, starting 24 hours after surgery, for 14 days. Participants receive initial LMWH prophylaxis 6 hours after surgery before starting the assigned regimen.
Rivaroxaban 10 mg once daily, starting 24 hours after surgery, for 14 days. Participants receive initial LMWH prophylaxis 6 hours after surgery before starting the assigned regimen.
Enoxaparin 40-60 mg once daily, weight-adjusted, starting 6 hours after surgery, for 14 days.
Mean Peak Systolic Velocity of the Common Femoral Vein at Postoperative Days 0, 7, 15, 21, and 28
Peak systolic velocity (PSV) of the common femoral vein will be measured using duplex Doppler ultrasound at baseline (postoperative day 0) and on postoperative days 7, 15, 21, and 28. Results will be expressed in centimeters per second (cm/s) and summarized as mean and standard deviation at each time point for the three thromboprophylaxis groups: apixaban 2.5 mg twice daily, rivaroxaban 10 mg once daily, and enoxaparin once daily. The mean PSV will be compared between groups.
Time frame: Postoperative day 0 through day 28.
Mean Time-Averaged Mean Velocity of the Common Femoral and Popliteal Veins
Time-averaged mean blood flow velocity will be measured separately in the common femoral and popliteal veins by duplex Doppler ultrasound at postoperative days 0, 7, 15, 21, and 28. Results will be expressed in centimeters per second (cm/s) and summarized as mean and standard deviation for each vein, treatment group, and time point.
Time frame: Within 28 days after surgery
Mean Diameter of the Common Femoral and Popliteal Veins
The diameter of the common femoral vein and popliteal vein will be measured separately by duplex Doppler ultrasound at postoperative days 0, 7, 15, 21, and 28. Results will be expressed in millimeters (mm) and summarized as mean and standard deviation for each vein, treatment group, and time point.
Time frame: Within 28 days after surgery
Mean Venous Blood Flow Volume in the Common Femoral and Popliteal Veins
Venous blood flow volume will be measured separately in the common femoral and popliteal veins by duplex Doppler ultrasound at postoperative days 0, 7, 15, 21, and 28. Results will be expressed in \[confirmed unit\] and summarized as mean and standard deviation for each vein, treatment group, and time point.
Time frame: Within 28 days after surgery
Number of Participants with Normal Respiratory Phasicity in the Common Femoral and Popliteal Veins
Respiratory phasicity will be assessed separately in the common femoral and popliteal veins at postoperative days 0, 7, 15, 21, and 28. Findings will be classified as normal or reduced/blunted. The number and percentage of participants with normal respiratory phasicity will be reported for each vein, treatment group, and time point.
Time frame: Within 28 days after surgery
Number of Participants with Preserved Distal Venous Flow Augmentation
Distal venous flow augmentation will be assessed separately in the common femoral and popliteal veins at postoperative days 0, 7, 15, 21, and 28 and classified as present or absent. The number and percentage of participants with augmentation present will be reported for each vein, treatment group, and time point.
Time frame: Within 28 days after surgery
Number of Participants with Visible Intraluminal Venous Sludging
Visible intraluminal venous sludging will be assessed separately in the common femoral and popliteal veins by duplex Doppler ultrasound. Findings will be classified as present or absent. The number and percentage of participants with visible sludging will be reported for each vein, treatment group, and assessment time point.
Time frame: Days 7, 15, 21, and 28
Number of Participants with Postoperative Complications
The number and percentage of participants experiencing clinically relevant postoperative bleeding, anticoagulation-related adverse events or overdose, suspected venous thromboembolism, return to the operating room, or postoperative infection will be reported during the 28-day follow-up. Each complication will be reported separately.
Time frame: During the 28-day follow-up
Number of Participants with Postoperative Cardiovascular Complications
The number and percentage of participants experiencing cardiovascular complications during the 28-day postoperative follow-up will be reported. The specific cardiovascular events assessed will be defined according to the study protocol.
Time frame: During the 28-day follow-up
Plan to share: No — Individual participant-level data will not be shared with other researchers because the study protocol does not include a plan for external IPD sharing. Participant data will be anonymized and securely stored for the purposes of the study.
No publications or documents are linked to this record.
Started Sep 2026 (actual). Primary completion is estimated for Apr 2027, 7 months after the start.
Of 64 non-industry interventional studies with no phase under Venous Thromboembolism, half reached primary completion within 30 months of starting (the median), counting those still running; a quarter within 19 and three quarters within 46. This study's planned 7 months is below that.
Counting every sponsor, half of 69 studies reached it within 30 months; a quarter within 19 and three quarters within 46.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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Studies of the drugs tested here: Apixaban · Rivaroxaban
Military Hospital of Tunis