HCl-demineralized mid-diaphyseal allogeneic segments of tibia were
implanted in the lumbar muscles of rats fed either a magnesium-deficient or
a magnesium-supplemented diet for one week prior to implantation and for
three weeks thereafter. Histological studies, histochemical
mucopolysaccharide determinations, tests for protease content of
undemineralized bone tissue, and microradiography showed that in the normal
hosts mostly trabecular bone grew into the heterotopic site, whereas in the
deficient rats a large fibrous covering formed about the implant and in
many instances cartilage was present in multiple locations under the
fibrous coat. In some instances cartilage wedges, not preceded by
multinucleated giant cells (matrixclasts), invaded the implant. This
fibrocartilaginous response to an exogenous inductor resembled the modified
growth pattern of bone recently reported in magnesium-deficient rats.