Comparison of long - term outcome of nerve regeneration between two methods of lengthy vascularized ulnar nerve grafting: an experimental study

Abstract

Objective To compare the long - term experimental results in nerve regeneration between two methods of lengthy vascularized ulnar nerve grafting. Methods Nine New Zealand rabbits were used. The ulnar nerves of bilateral sides were dissected and cut at the wrist and at the point where the superior ulnar collateral artery (SUCA) originated from the brachial artery, and repaired in situ. The ulnar nerve was vascularized by SUCA onn the right side, and by SUCA and the ulnar artery (UA) on the left side. Seven months later, electromyography of the ulnar nerve was recorded. The number of regenerated myelinated nerve fibers and its cross - sectional area, the thickness of the myelin sheath (mt), the ratio (d/D) of axonal diameter (d) to total fiber diameter (D), and muscle histology were analyzed. Results The front foot ulcer of the 9 rabbits healed 7 months after the operation. Nerve action potential amplitude and motor nerve conduction velocity of the ulnar nerve of the right side were inferior to those of the left side. As for the number and cross - sectional area of regenerated myelinated nerve fibers, no difference was found at the level 3 cm proximal to the suture site at the wrist between the two sides. When compared at the level 1cm proximal to and 0.5 cm distal to the suture site at the wrist, the ones of the left side were superior to those of the right side. There was no difference considering the wet muscle weight and muscle fiber cross - sectional area of the hypothenar muscles, myelin sheath thickness and d/D ratio at two sides. Conclusions Both methods of lengthy vascularized ulnar nerve grafting can obtain satisfactory results. Difference of regenerated nerve fiber count between the two procedures was found at the distal part of nerve graft. Therefore it is recommended to elongate dissection length of the graft above elbow and to shorten the graft below elbow in the clinical applications of ulnar nerve grafting with SUCA.