Superior muscle reinnervation after autologous nerve graft or poly-L-lactide-epsilon-caprolactone (PLC) tube implantation in comparison to silicone tube repair

Abstract

Recovery after peripheral nerve injury depends not only on the amount of reinnervation, but also on its accuracy. The rat sciatic nerve was subjected to an 8 mm long gap lesion repaired either by autograft (AG, n = 6) or tubulization with impermeable silicone tube (SIL, n = 6) or permeable tube of poly-L-lactide-epsilon-caprolactone (PLC, n = 8). Recordings of the compound muscle action potential (CMAP) from gastrocnemius (mGC), tibialis anterior (mTA) and plantar (mPL) muscles were performed 90 days after injury to assess the amount of muscle reinnervation. The CMAP amplitude achieved in mGC, mTA and mPL was similar in after nerve autograft (39%, 42%, 22% of control values) and PLC tube implantation (37%, 36%, 24%) but lower with SIL tube (29%, 30%, 14%). The nerve fascicles projecting into each of these muscles were then transected and retrograde tracers (Fluoro Gold, Fast Blue, DiI) were applied to quantify the percentage of motoneurons with single or multiple branches to different targets. The total number of labeled motoneurons for the three muscles did not differ in autografted rats (1186 +/- 56; mean +/- SEM) with respect to controls (1238 +/- 82), but was reduced with PLC tube (802 +/- 101) and SIL tube (935 +/- 213). The percentage of neurons with multiple projections was lower after autograft and PLC tube (6%) than with SIL tube (10%). Considering the higher CMAP amplitude and lower number of neurons with multiple projections, PLC nerve conduits seem superior to SIL tubes and a suitable alternative to autografts for the repair of long gaps.