Middle ear packing: comparison of materials in an animal model of mucosal trauma.

Objective: To compare absorbable gelatin sponge (AGS) with an injectable esterified hyaluronic acid (EHA) as middle ear packing material after mucosal trauma.

Study Design: Randomized, blinded, and controlled study.

Setting: Tertiary university-based hospital.

Subjects And Methods: Twenty-three guinea pigs underwent middle ear surgery with mucosal trauma performed on both ears and one ear packed with either EHA 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. Macroscopic and microscopic analysis measured inflammatory reaction in each group.

Results: ABR threshold changes from baseline in the EHA and both control groups were minor. Threshold levels were higher in the AGS group compared with the AGS control group. This trend was seen in each frequency tested at each time interval. Macroscopic analysis showed tympanic membrane perforation was rare, effusions were common in the AGS group, mucosal edema was most frequent in the AGS group, and unabsorbed packing was usually detected in the AGS group with little EHA detectable at 6 weeks. Microscopic analysis showed normal mucosal healing in all groups. Two AGS ears demonstrated excessive middle ear packing with exuberant osteoneogenesis.

Conclusions: Middle ear function and mucosal healing after surgery occurred similarly between the EHA control group and the EHA group. In contrast, the AGS group demonstrated worse hearing and a greater level of osteoneogenesis compared with the AGS control group. These results support EHA as an alternative middle ear packing material in otologic surgery.