Functional and morphological assessment of a standardized rat sciatic nerve crush injury with a non-serrated clamp

Peripheral nerve researchers frequently use the rat sciatic nerve crush as a model for axonotmesis.Unfortunately, studies from various research groups report results from different crush techniquesand by using a variety of evaluation tools, making comparisons between studies difficult. The pur-pose of this investigation was to determine the sequence of functional and morphologic changes af-ter an acute sciatic nerve crush injury with a non-serrated clamp, giving a final standardized pres-sure of p9 MPa. Functional recovery was evaluated using the sciatic functional index (SFI), theextensor postural thrust (EPT) and the withdrawal reflex latency (WRL), before injury, and thenat weekly intervals until week 8 postoperatively. The rats were also evaluated preoperatively andat weeks 2, 4, and 8 by ankle kinematics, toe out angle (TOA), and gait-stance duration. In addi-tion, the motor nerve conduction velocity (MNCV) and the gastrocnemius-soleus weight parameterswere measured just before euthanasia. Finally, structural, ultrastructural and histomorphometricanalyses were carried out on regenerated nerve fibers. At 8 weeks after the crush injury, a full func-tional recovery was predicted by SFI, EPT, TOA, and gait-stance duration, while all the other pa-rameters were still recovering their original values. On the other hand, only two of the histomor-phometric parameters of regenerated nerve fibers, namely myelin thickness/axon diameter ratio andfiber/axon diameter ratio, returned to normal values while all other parameters were significantlydifferent from normal values. The employment of traditional methods of functional evaluation inconjunction with the modern techniques of computerized analysis of gait and histomorphometricanalysis should thus be recommended for an overall assessment of recovery in the rat sciatic nervecrush model