The apparent volume of interdigitation: a new parameter for evaluating the influence of surface topography on mechanical interlock.

A new parameter has been defined to estimate the apparent volume of interdigitation (V(i)) that is available from a surface to support mechanical interlock. The parameter is estimated in terms of the core roughness parameters, which can be obtained from the material ratio curve of a representative surface profile. A verification of the definition for V(i) is performed with the use of ideal surface profiles consisting of Gaussian and skewed height distributions. In contrast to conventional surface roughness parameters, the expression for V(i) is capable of differentiating between positive and negative skewed surfaces with the same average surface roughness. It is expected that V(i) will be a useful tool for optimization of the prosthesis and bone surface topographies, which are essential to the long-term success of cemented total joint replacements. Copyright 2001 John Wiley & Sons, Inc.