Morphologic and functional study of rat median nerve repair by terminolateral neurorrhaphy of the ulnar nerve.

While it has been shown that terminolateral (end-to-side) neurorrhaphy leads to successful functional motor reinnervation of the peripheral territories belonging to the severed nerve, data on the morphology of terminolateral sprouting and on the voluntary control of the motor function restored by terminolateral neurorrhaphy are still partial. In this study, the severed rat median nerve was sutured in an end-to-side fashion to the intact ulnar nerve. The progression of recovery of the flexion of the fingers was assessed by means of the grasping test. Seven months after surgery, the rats were sacrificed, and morphologic and morphometric analysis was performed on the regenerated median nerve and on the donor ulnar nerve. Results of the functional assessment showed that voluntary motor control of the muscles innervated by the median nerve was partially and progressively recovered by terminolateral neurorrhaphy, with a mean strength in the flexion of the fingers that reached about 20 percent of normal before sacrifice. Morphologic and morphometric analysis showed that nerve-fiber regeneration occurred in all repaired median nerves. Signs of nerve fiber atrophy were detected in the ulnar nerve distal to the point of suture, suggesting the possible occurrence of secondary damage to the donor nerve after terminolateral neurorrhaphy that should be taken into consideration in a clinical perspective.