Long-term in vivo biomechanical properties and biocompatibility of poly(2-hydroxyethyl methacrylate-co-methyl methacrylate) nerve conduits

Artificial grafts are promising alternatives to nerve grafts for peripheral nerve repair because they obviate the complications and disadvantages associated with autografting such as donor site morbiditv and limited tissue availability. We have synthesized poly (2-hydroxyethyl methacrylate-co-methyl methacrylate) (PHEMA-MMA) porous tubes and studied their efficacy in vivo. Specifically, we studied the short- and long-term stability and biocompatibility of 12 mm long tubes for the repair of surgically created 10mm nerve gaps in rat sciatic nerves. Prior to implantation, tubes were analyzed in vitro using a micro-mechanical tester to measure displacement achieved with load applied. These results served as a calibration curve, y = 6.8105 x -0.0073 (R-2 = 0.9750,n = 28). for in Nivo morphonneiric tube compression measurements. In vivo, most of the PHEMA-MMA conduits maintained their structural integrity up to S weeks. but 29% (4/14) of them collapsed by 16 weeks. Interestingly, the tube wall area of collapsed 16-week tubes was significantly lower than those of patent tubes. Tubes were largely biocompatible; however, a small subset of 16-week tubes displayed signs of chronic inflammation characterized by finger-like tissue extensions invading the inner tube aspect, inflammatory cells (some of which were EDI divided by macrophages) and giant cells. Tubes also demonstrated signs of calcification. which increased front 8 to 16 weeks. To overcome these issue, future nerve conduits will be re-designed to be more robust and biocompatible. (C) 2004 Elsevier Ltd. All rights reserved.