“The lysis threshold”: an erroneous and perhaps misleading concept?

The “lysis threshold” concept suggests that a lower limit of particle generation exists in total hip arthroplasty (THA) below which lysis will not occur or is tolerable. Although this concept is appealing at first, serious reservations arise with more detailed analysis. Five major points challenge this concept: (1) For many of the reports, the duration too short. Ten years is not the goal for most patients. (2) The definition of lysis is inadequate, listing only “balloon” lysis or endosteal erosion. (3) In most reports of 100 μm/y, lysis does occur. (4) Plain radiographs are not adequate for detection of lysis. (5) Other factors can overwhelm the role of particle volume, such as patch-porous cementless femoral designs. These 5 observations seriously challenge the lysis threshold concept.