A study was done to evaluate the effect of a system for the local
delivery of indomethacin on demineralized bone-induced formation of
heterotopic bone in the abdominal muscles of rats. Two separate
investigations were conducted on a total of forty-eight Wistar rats. In
both series, two types of implants were used: polyorthoester and
demineralized bone (Group A, the control group) and polyorthoester with 5
per cent indomethacin and demineralized bone (Group B, the experimental
group). In the first series, host-tissue responses and osteoinduction were
evaluated histologically at two, three, and four weeks after the
implantation. In the second series, the formation of bone was quantified on
the basis of uptake of 85Sr at four weeks after the implantation. The
polyorthoester system for the local delivery of indomethacin significantly
inhibited demineralized bone-induced heterotopic formation of bone, as
demonstrated by light microscopy and by uptake of 85Sr. The polyorthoester,
with or without the drug, caused little tissue reaction and was resorbed
almost completely at four weeks.