Background: Tourniquet pressure inflation is commonly selected between 100 and 150 mm Hg above the systolic blood pressure (SBP). Given the lack of evidence to support a given inflation pressure, our study aimed to ascertain the lowest tourniquet pressure that facilitated total knee arthroplasty (TKA) and resulted in the least postoperative pain and complications.

Methods: In a double-blind, randomized controlled trial of patients scheduled for unilateral primary TKA, 150 were assigned to use tourniquet pressures of SBP + 75 mm Hg (group I), SBP + 100 mm Hg (group II), and SBP + 150 mm Hg (group III). The quality of the bloodless field, total blood loss, and limb swelling were determined perioperatively. Clinical outcomes were evaluated by visual analog scale for pain at thigh and surgical site, serum creatinine phosphokinase levels, wound complications, range of motion, and Knee Society Score.

Results: Visual analog scale for pain at thigh and surgical site were lowest in group I (P < .01) and highest in group III (P < .01). However, the quality of bloodless field at the tibial cutting surface was significantly better in group III compared to group I/II but not at the femoral cutting surface. The total blood loss and limb swelling showed no difference among 3 groups. Postoperative serum creatinine phosphokinase levels at 24 and 48 hours and wound complications in group III were significantly higher than group I (P < .01) and group II (P < .01). Nevertheless, postoperative knee range of motion and Knee Society Score were not significantly different among 3 groups.

Conclusion: Post TKA, the lowest tourniquet pressure was associated with significantly less postoperative tourniquet and surgical site pain, muscle damage, and wound complications.