Functional analyses prior to and 1, 2, 3, and 4 months after surgery were carried out. Animals were trained and tested in a walkway (length, 95 cm; width, 12 cm) as previously described.14 Using 3 to 6 footprints per animal/time point/group, the sciatic functional index (SFI) score was calculated. The extensor postural thrust (EPT) measures the amount of force that a rat can exert onto a digital scale as it extends its hind limb and is an indication of the performance of the soleus and gastrocnemius muscles. The thrusts from the uninjured limb and the injured limb were determined, and the percentage of motor deficit was calculated as previously described.14 Sensory evaluation was achieved by testing the withdrawal response mediated by myelinated Aδ fibers in response to mechanical stimulation on the plantar skin. A withdrawal reflex of less than 1 second in response to pinprick was recorded as a positive result. At the same time points, 4 animals in groups 2 through 5 and 2 animals in group 1 were harvested to evaluate the wet weights of the gastrocnemius and soleus muscles. Because these muscles atrophy without innervations by the sciatic nerve, the ratios of harvested wet muscle weights of the injured leg to those of the uninjured leg indicated the degree of muscle atrophy.14 All animals were functionally tested (SFI, EPT, and sensory evaluation) during baseline measurements (n = 20), but owing to harvest at 7, 14, and 21 days and 2 months, n = 12 for each group for functional testing at 1 month, n = 8 at 2 months, and n = 4 at 3 and 4 months. For end points regarding harvested tissue (muscle weights and histomorphometry), n = 4 for all times consistently.