Type grouping in rat skeletal muscle after crush injury

Object. Accuracy of reinnervation is an important factor that determines outcome after nerve injury and repair. Type grouping-the clustering of muscle fibers of the same type after reinnervation-can be used to investigate the accuracy of reinnervation. In this study, the degree of type grouping after crush injury in rats was compared with the clustering of muscle fibers after autografting or single-lumen nerve grafting. Methods. Twelve weeks after sciatic nerve crush injury in rats, clustering of Type I muscle fibers was analyzed in the target muscle with adenosine 5'-triphosphatase staining. In addition, the number of regenerated axons was determined in the nerve distal to the crush injury. Results were compared with that of the authors' previous study. Results. Type grouping was more abundant after crush injury than after autograft or single-lumen nerve graft repair. Conclusions. Crush injury leads to more clustered innervation of muscle fibers, probably because the Schwann cell basal lamina tubes are not interrupted as they are in autograft or artificial nerve graft repair. This finding adds to understanding the processes playing a role in nerve regeneration. (DOI: 10.3171/2010.9.JNS091656)