Structural Integrity of Absorbable Gelatin Sponges for Middle Ear Packing in Otologic Surgery

Abstract

This study investigates the physical properties upon immersion of two gelatin sponges commonly used in otologic surgery. Absorbable gelatin sponges are often used in middle ear surgery to achieve hemostasis and, perhaps more importantly, to provide a "scaffolding" to support ossicular chain and/or tympanic membrane reconstructions. Their rate of dissolution may therefore affect the success of tympanic membrane closure. An in vitro study was conducted to quantify the material changes of two absorbable gelatin sponges, a standard-density sponge and one with fewer collagen cross-linkages (low-density sponge). Volume loss (%) in 0.9% saline, 0.3% ciprofloxacin, and/or 0.1% dexamethasone as single-agent otic drops in a combination formulation was measured at 15-minute intervals for the first hour and at days 1, 3, and 5 postimmersion. Secondary end points included compressibility, porosity under microscopy, and infrared spectroscopy analysis. The low-density sponge immersed in any of the three otic solutions showed a statistically significant greater volume loss at all time points when compared with the standard-density sponge (27.2% ± 5.4% vs. 15.4% ± 6.0% at 15 minutes and 44.8% ± 5.1% vs. 34.6% ± 2.9% at 5 days, p < 0.001). Interestingly, both sponges immersed in normal saline had lost almost half of their original volume after 15 minutes when compared with samples immersed in an otic solution (48.3% ± 4.6% vs. 21.3% ± 8.3%, respectively, p < 0.001). The standard-density sponge immersed in an otic solution of ciprofloxacin, dexamethasone, or a combination formulation best maintained its structural integrity. Ancillary in vivo studies are required to assess the hemostatic properties, surgical outcomes, and middle ear synechiae of the above study conditions. Foundational evidence.