Effect of Two Limb Positions on Venous Hemodynamics and Hidden Blood Loss following Total Knee Arthroplasty.

This study assessed the effects of limb position on venous hemodynamics and blood loss after primary total knee arthroplasty (TKA). First, the venous blood flow velocity was detected by color Doppler flow imaging in seven young volunteers after the leg was elevated 25 cm with the knee in full extension or mild flexion. Next, 108 consecutive TKA patients were randomized into flexion or extension groups. Both groups had the leg elevated 25 cm at the ankle over a specific backing pad for 72 hours postoperatively. In the flexion group, the knee was flexed mildly (< 30 degrees) during this period. In the extension group, the knee was extended fully. Perioperative total blood loss, hidden blood loss (HBL), knee swelling, range of motion (ROM), straight-leg raising action, and postoperative complications within 6 weeks of surgery were measured. Venous blood flow velocity in the mild flexion position was significantly faster than that in knee full extension position. Postoperative HBL and knee swelling were significantly lower in the flexion group than in the extension group, and ROM and straight-leg raising actions were significantly higher during early follow-up. No significant difference was observed in perioperative total blood loss or in ROM at 6 weeks postoperatively. The findings of this study indicate that elevating the leg with the knee flexed mildly can promote venous return and decrease the HBL and knee swelling following TKA.