Abstract
Objective: To compare absorbable gelatin sponge (AGS) with polyurethane foam (PUF) as middle ear packing material after mucosal trauma. Method: Controlled animal experiment. Thirty-six guinea pigs underwent middle ear surgery with mucosal trauma performed on both ears. One ear was packed with either PUF or AGS. Contralateral ears were used as nonpacked paired controls. Auditory brainstem response (ABR) thresholds were measured preoperatively and repeated at 1, 2, and 6 weeks postoperatively. Histological analysis was done by a pathologist blinded to the type of packing using hematoxylin and eosin staining to measure inflammatory reaction and trichome staining to measure fibrosis in each group. Results: ABR recordings demonstrates that threshold level changes from baseline were minor in the PUF and the control groups. Threshold levels were higher in the AGS group compared with both control groups and the PUF group for the 1 KHz and 0.5 KHz frequencies. Macoscopic analysis showed no tympanic membrane perforation and packing material was absorbed in all groups at 6 weeks postoperatiely. The histological analysis showed normal mucosal healing in the PUF and control groups. There was more packing retention, inflammation, and osteoneogenesis in the AGS group than the PUF or either control group. Conclusion: Following surgical trauma, the middle ear mucosa healed well without packing or with PUF packing material, and hearing was not affected. In contrast AGS packing material showed hearing loss at low frequencies and osteogenesis.