Journal of Bone and Joint Surgery. American volume vol:80 issue:11 pages:1710
I read with interest “Porous-Coated Metal-Backed Patellar
Components in Total Knee Replacement. A Postmortem Retrieval
Analysis” (80-A: 518-528, April 1998), by Bloebaum et al.
The authors reported a mean appositional bone index of 86 percent, as measured on contact radiographs of three-millimeter-thick sections.
However, this is probably a gross overestimation of the real
amount of bone apposition because of the superposition effect of contact radiographs on such thick sections.
A realistic assessment of bone apposition is only possible on sections with a thickness of thirty micrometers or less9,10. This is 100 times thinner than the sections analyzed by Bloebaum et al. The techniques used to obtain and analyze sections of this thickness are readily available2. It is therefore very likely that the actual bone
apposition for these patellar components was much smaller than that reported.