Effects of particulate high‐density polyethylene and titanium alloy on tissue ingrowth into bone harvest chamber in rabbits

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Abstract
The purpose of this study was to determine whether small, phagocytosable particles of titanium alloy (Ti) and high‐density polyethylene (HDPE) have an adverse effect on bone ingrowth. The bone harvest chamber (BHC) was implanted bilaterally in the proximal tibial metaphysis of six mature rabbits. The BHC has a transverse 1‐mm wide pore providing a continuous canal through the chamber for tissue ingrowth. After an initial 6‐week period for osseointegration of the BHC, the contents of the canal were harvested repeatedly at 3 weekly intervals. This could be done with the chamber in place, without disturbing its exterior surface or the surrounding bone. The carrier solution, 1% sodium hyaluronate (Healon) was implanted first. In subsequent implantations, Healon was mixed with particles of HDPE or Ti averaging 4.7 ± 2.1 and 3.0 ± 2.6 μm, respectively. The contralateral chamber was left empty and served as a control. The chambers were harvested repeatedly, alternating experimental and control sides. The sections from the control side, and those containing Healon alone demonstrated extensive trabecular bone in a fibrovascular stroma. The sections containing Ti alloy particles were qualitatively and quantitatively similar to the control sections and those containing Healon, except for the presence of small black granules of Ti alloy, dispersed in the fibrovascular stroma or phagocytosed by scattered macrophages. The sections containing HDPE particles were infiltrated and engulfed by mononuclear and multinuclear histiocytic cells in a highly fibrous stroma. The majority of the multinucleated cells present were interpreted as being foreign body giant cells. Less trabecular bone was seen in the HDPE group compared to the other groups. Using the parameters chosen for this experiment, it would appear that small, phagocytosable HDPE particles are more deleterious to net formation of bone compared to particles of Ti alloy. © 1995 John Wiley & Sons, Inc.