OBJECTIVETo Compare the curative effects between titanium mesh coated with or without silk fibroin and in the treatment of larger trachea circumferential defects. To explore the merits of titanium mesh coated with silk fibroin in promoting mucous healing and decreasing related complications.

METHODSTwenty-five New Zealand white rabbits were chosen , divided randomly as follows: group one: titanium mesh coated with silk fibroin (n = 12), group two: pure titanium mesh without silk fibroin (n = 12); Titanium mesh coated with silk fibroin and those titanium without silk fibroin were embedded in the anterior of 7-12th tracheal rings respectively, in 2 weeks we removed the anterior and lateral wall of 7-12th tracheal rings about 8 mm x 6mm (more than half ring) and used the two different materials to reconstruct tracheal defects. All these rabbits were euthanized in 4, 8 and 12 weeks and tracheal CT scan, tracheal endoscopy, histopathological examination and scanning electron microscopic examinations were performed. All complications such as death, local inflammation, tracheal stenosis were documented. Group three, leave one normal rabbit as controlled study , removed the anterior and lateral wall of 7-12th tracheal rings, and histopathological examination, scanning electron microscopy were performed as controlled study.

RESULTSThe CT scan, tracheal endoscopy of those with silk fibroin showed there was no apparent tracheal stenosis. Histopathological examination showed there was no obvious granulation tissue and scar. The mucous membrane and cilia grow normally. The silk fibroin was not entirely absorbed and the remains showed good biocompatibility. The scanning electron microscopy showed that the cilia grew better and more orderly than that of group two, and in 12 weeks, the cilia became normal. In group two, there were 5 rabbits died in succession from suffocation in 4, 5, 7, 17, 60 days after surgery. All rabbits had local or general subcutaneous emphysema. The CT scan, tracheal endoscopy and pathological examination showed that there were apparent granulation tissue, scar hypertrophy, and tracheal stenosis. The mortality of group two (41.7%) for suffocation compare to that of group one (0), the incidence rate of subcutaneous emphysema in group two (100%) to that of group one (25.0%) and the average cross section stenosis area in group two (18.15 +/- 7.85) mm2 to that of group one (3.15 +/- 1.58) mm2, there are significant statistically differences in these postoperative complications (P <0.05) and stenosis degree (P <0.05) between the two groups. In addition, there was one rabbit died of diarrhea in each group except group three.

CONCLUSIONSSilk fibroin and titanium mesh coated with silk fibroin showed good biocompatibility. Titanium mesh coated with silk fibroin used in tracheal reconstruction of rabbits can promote agglutination of mucous membrane and decrease postoperative complications, such as subcutaneous emphysema, tracheostenosis. It may be a prospective biomaterial which can be used in clinical circumferential trachea defect reconstruction.