Antiadhesive effect of polyurethane foam packing in the guinea pig middle ear

The effects of different packing materials on healing and hearing after trauma to middle ear mucosa, an experimental study in rats

PURPOSE

To compare the performance of Spongostan, Otopore, Spongostan soaked with dexamethasone and Spongostan soaked with Hyaluronic acid (HA) as middle ear packing material after mucosal trauma.

METHODS

Twenty rats were divided into 4 groups. In control group (group 1), the middle ear cavities of animals were bilaterally packed with Spongostan; in group 2, with Otopore; in group 3, with Spongostan soaked with dexamethasone; and in group 4, with Spongostan soaked with HA. Auditory brainstem responses (ABRs) were performed preoperatively and 1 and 6 weeks postoperatively. Histological analyses were performed to evaluate the inflammatory reaction and wound healing in the middle ear cavity.

RESULTS

ABR recordings demonstrate that threshold level changes from baseline were minor in Otopore and Spongostan soaked with dexamethasone packed ears. Threshold levels were higher in the Spongostan and Spongostan soaked with HA packed ears compared with both Otopore and Spongostan soaked with dexamethasone packed ears. Histological analyses showed that Spongostan caused inflammation more intense than Otopore and Spongostan soaked with dexamethasone. Residual material at postoperative week 6, new bone formation and adhesion were common in the Spongostan group compared with other groups. Fibrosis was more common in Spongostan group compared with other groups but the difference was not significant.

CONCLUSION

Otopore appears to be safe and effective for use in otologic surgery. The inflammation, adhesion and new bone formation decreased when Spongostan was used with steroid or HA, when compared to Spongostan alone.

Comparison of packing material in an animal model of middle ear trauma

PURPOSE

To compare the performance of absorbable gelatin sponge (AGS) with polyurethane foam (PUF) as middle ear packing material after mucosal trauma.

MATERIALS AND METHODS

Using a randomized, controlled and blinded study design fifteen guinea pigs underwent middle ear surgery with mucosal trauma performed on both ears. One ear was packed with either PUF or AGS while the contralateral ear remained untreated and used as non-packed paired controls. Auditory brainstem response (ABR) thresholds were measured pre-operatively and repeated at 1, 2, and 6weeks postoperatively. Histological analysis of middle ear mucosa was done in each group to evaluate the inflammatory reaction and wound healing. Another eighteen animals underwent middle ear wounding and packing in one ear while the contralateral ear was left undisturbed as control. Twelve guinea pigs were euthanized at 2weeks postoperatively, and six were euthanized at 3days post-operatively. Mucosal samples were collected for analysis of TGF-β1 levels by enzyme-linked immunosorbent assay.

RESULTS

ABR recordings demonstrate that threshold level changes from baseline were minor in PUF packed and control ears. Threshold levels were higher in the AGS packed ears compared with both control and PUF packed ears for low frequency stimuli. Histological analysis showed persistence of packing material at 6weeks postoperatively, inflammation, granulation tissue formation, foreign body reaction and neo-osteogenesis in both AGS and PUF groups. TGF-β1 protein levels did not differ between groups.

CONCLUSION

PUF and AGS packing cause inflammation and neo-osteogenesis in the middle ear following wounding of the mucosa and packing.