Herbert total knee prosthesis. Combined laboratory and clinical assessment

The authors tested the Herbert knee prosthesis, which was designed to restore intrinsic stability with limited degrees of freedom for rotation to severely damaged or deformed knees, in a knee simulator. These tests indicated a tendency for the prosthesis to fracture through the medial femoral housing after cycling for the equivalent of 1 to 3 years of normal use. In a clinical series of 35 knees treated with the prosthesis, there were 5 failures similar to those produced by laboratory testing. On the basis of this combined study, the Herbert prosthesis appears to have design characteristics that seriously limit its usefulness for long-term knee replacement. Testing in a knee simulator in this case appeared to be a valid predictor of clinical failure.