Missing osteoconductive effect of a resorbable PEO/PBT copolymer in human bone defects: A clinically relevant pilot study with contrary results to previous animal studies

PEO/PBT 70/30 (POLYACTIVE(R) 70/30), a degradable porous copolymer,vith ela stic properties, was found to be osteoconductive in many animal studies. Th e aim of this study was to determine the osteoconductive effect in a human paired control iliac defect model. In seven patients undergoing anterior sp inal interbody fusion surgery, two bicortical iliac defects for autograft h arvesting were created, The defect size was identical for both defects meas uring about 40 x 15 mm (group I). One defect was filled with the degradable implants, whereas the remaining one was left untreated as a control, The d efect site for treatment was chosen randomly. In three further patients, on ly one defect measuring about 40 x 35 mm was created (group II), All patien ts were examined clinically and radiologically by spiral-CT after 1, 6, 12, 24, and 52 weeks, Three-dimensional reconstructions as well as CT-volumetr ic measurements using 1 mm sections mere used as evaluation methods. In gro up I, a two-tailed paired t-test showed that the treated defects had signif icantly less formation of new bone than the untreated ones (p < 0.05 after 12 weeks, p < 0.01 after 52 weeks). Also, in group II, not much bone ingrow th could be observed. The histological evaluation of one patient in group I revealed no bone within the pores, and a fibrous layer between bone and im plant was always present. Therefore, PEO/PBT 70/30 cannot be recommended as a bone substitute for clinical use. Differences in bone regeneration betwe en humans and certain animal species as well as inapplicable defect models in previous animal studies are discussed as possible reasons for the failur e. (C) 2000 John Wiley & Sons, Inc.