Experimental study of denervated muscle atrophy following severance of posterior rami of the lumbar spinal nerves.

Abstract

The morphologic changes in denervation atrophy of paravertebral muscles after severance of the posterior rami in cats were investigated, using histochemical methods and electromyography. Using a paraspinal approach, three branches of the posterior rami on the left side were cut under microscopy at one, two, or three levels (L2 approximately L4). Muscle atrophy was evaluated, using the percent wet weight and the percent diameter of muscle fibers as parameters. Myosine ATPase stain was used to observe reinnervation. Four weeks after surgery, the range and severity of muscle atrophy increased proportionally to the number of posterior rami severed. Muscle atrophy was revealed at one or two levels caudal to the injured nerve level. At 12 and 24 weeks, muscle atrophy recovered gradually. In more than two-level injury groups, however, recovery of percent wet weight reached up to 80% even after 24 weeks, despite the fact of reinnervation demonstrated in some parts of the denervated muscles.