Application Of Helix Water Jet In Dissecting The Facial Nerves: An Experimental Study On Dogs

PurposeThe objective of this study was to evaluate the suitable water pressure when using water-jet in dissecting the facial nerves, and demonstrate whether the water-jet is more safe during the operation by comparing with routine scalpels.Materials and methodsWe selected 12 dogs, and averagely divided them into two groups. Total parotidectomy with retention of the facial nerve was performed on the bilateral parotids of all the dogs. In the first group, 6 canine total bilateral parotids were dissected by water-jet (Andreas Pein Medizintechnik Company, Schwerin, Germany) with the use of the same nozzle type (120 in micron diameter), but different levels of water jet pressure (30-50 bars in the left side of parotids and 50-60 bars in another side). Local status of facial palsy was documented daily. Reactions of the facial nerve were detected by electrophysiological monitor before and after parotidectomies. In a second phase, the dissected nerves were resected and the animals were killed. Samples of water-jet-dissected nerve branches underwent histological examination and were compared with clinical and electrophysiological findings. According to the result brought back by the first group, In another group the right side of canine parotids were excised by routine scalpels, the left side of parotids was dissected by water-jet using 120 in micron diameter jet and 50-60 bars water pressure. Others processes were as same as the first group.ResultsIn the first group, operations were easily performed on all parotid glands by means of the Water-jet, using different levels of water jet pressure (30-50 bars in the left side of parotids and 50-60 bars in the other). No significant symptoms of facial palsy were observed before and after the operations. There was no significant difference in the nerve conduction velocities between the different water jet pressures (P>0.05) after operations. Also, histological examination showed no obvious difference (both hadâ… -â…¡degree damages).In another group the left sides of canine parotids were excised by routine scalpels, the other sides of parotids were dissected by water-jet using 120 in micron diameter jet and 50-60 bars water pressure. After operations the nerve conduction velocities in the water jet group were higher than those of routine scalpels group (control group) (P<0.05), and local facial palsy occurred in the latter group. Also, according to the histological examination the facial nerves in the water jet group hadâ… -â…¡degree damages while the control group hadâ… -â…£degree damages with the facial nerves.ConclusionsThe study has shown that it is possible to perform tissue-selective operations on the parotid gland by means of the Water-jet, and ensuring safe, the operating pressures of 50 to 60 bar was recommended. Besides, the advantages of the new water-jet offer a valuable alternative compared with the normal dissection methodsadopted in parotid surgery.