A meta-analysis of the randomized
controlled trials showed that the clamping methods could reduce the true blood loss only
when the drain was clamped for four hours or more.(Tai et al. 2010b) We found three trials
dealing with the two-hour, one-hour, and half-hour clamping methods and then showing no
reduction in true blood loss.(Kiely et al. 2001; Eum et al. 2006; Tsumara et al. 2006) These
findings suggest that when using the clamping methods to manage the drainage system
after TKA, the ideal clamping period should be four hours or more. However, the patients
managed with the longer duration of drain-clamping may have less blood loss but may also
eliminate the potential advantages of the drainage. In addition, the situation of long
clamping is similar to that of non-drainage; therefore, it is not logical for clinical practice