In vivo evaluation of poly(L-lactic acid) porous conduits for peripheral nerve regeneration

The present study provides in vivo trials of poly(L-lactic acid) (PLLA) as a porous biodegradable nerve conduit using a 10 mm sciatic nerve defect mod el in rats. The PLLA conduits, fabricated by an extrusion technique, had an inner diameter of 1.6 mm, an outer diameter of 3.2 mm, and a length of 12 mm. They were highly porous with an interconnected pore structure (of 83.5% porosity and 12.1 mu m mean pore size). The conduits were interposed into the right sciatic nerve defect of Sprague Dawley rats using microsurgical t echniques; nerve isografts served as controls. Walking track analysis was p erformed after conduit placement monthly through 16 weeks. At the conclusio n of 6 and 16 weeks, sections from the isograft/conduit and distal nerve we re harvested for histomorphometric analysis. The right gastrocnemius muscle was also harvested and its weight was determined. All conduits remained in tact without breakage. Moreover, no conduit elongated during the 16 weeks o f placement. Walking track analysis and gastrocnemius muscle weight demonst rated increasing regeneration over the 16 weeks in both the conduit and iso graft control groups, with control values significantly greater. The nerve fiber density in the distal sciatic nerve for the PLLA conduits (0.16 +/- 0 .07) was similar to that for the control isografts (0.19 +/- 0.05) at 16 we eks. The number of axons/mm(2) in the distal sciatic nerve for the PLLA con duits was lower than that for the isografts (13 800 +/- 2500 vs. 10 700 +/- 4700) at 16 weeks. The results for PLLA were significantly improved over t hose for 75:25 poly(DL-lactic-co-glycolic acid) of a previous study and sug gest that PLLA porous conduits may serve as a scaffold for peripheral nerve regeneration. (C) 1999 Elsevier Science Ltd. All rights reserved.