Tissue responses to molecularly reinforced polylactide-co-glycolide implants

Plates for internal fixation fabricated from biodegradable polymers degrade via an autocatalytic route. When they are used in bone implants of signifi cant size and thickness, hollowing of the implant may occur while the overa ll dimensions appear unchanged. We hypothesized that incorporation of a cro ss-linked polypropylene fumarate matrix into polylactide-co-glycolide bone plates may provide an internal molecular network which prevents implant col lapse. Cross-linking reagents of varying hydrophilicity including N-vinylpy rrolidone (VP), hydroxyethylmethacrylate (HEMA), and ethyleneglycol dimetha crylate (EGDMA) were employed. With the objective of determining the most b iocompatible and structurally sound composition for molecular reinforcement , we investigated tissue responses in both subcutaneous and orthotopic rode nt implantation models in relation to maintenance of implant integrity by h istologic, histomorphometric, and stereomicroscopic analysis. Results showe d that tissue responses were correlated with dimensional stability of the i mplants. The most favorable results were seen with the hydrophobic cross-li nker EGDMA; this may have been related to the initial reduction of the wate r uptake by the implant. Cross-linking of polypropylene fumarate with EGDMA within a polylactide-co-glycolide bone plate may offer a means to maintain excellent biocompatibility while improving dimensional stability of biodeg radable bone plates.