Cross-Linked Hydrogels for Middle Ear Packing

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Abstract
To develop an ideal supportive packing material for ossiculoplasty, tympanoplasty, or other otologic procedures. Several materials, namely, Carbylan-SX (P-C; Sentrx Surgical, Inc., Salt Lake City, UT), Gelfoam (P-GF; Pharmacia & Upjohn, Kalamazoo, MI), and Merogel (P-MG; Medtronics, Inc., Minneapolis, MN), were prepared and then placed into a Hartley guinea pig's (Elm Hill, Chelmsford, MA) middle ear cavities through a large myringotomy incision. The contralateral ear underwent a large myringotomy without packing material being placed. Preoperative and posteroperative auditory brainstem response studies were performed using Intelligent Hearing system software. The animals were examined weekly. Two weeks after packing placement, the animals were killed, and the temporal bones were harvested. Whole temporal bone sectioning was performed to analyze the presence of implant, surrounding inflammation, presence of osteoneogenesis and fibrosis, or adhesions. All the materials, except the P-MG, were easy to place into the middle ear cavity. The P-MG contains woven strands that are difficult to trim into the small sizes needed for placement. The P-MG group had a smaller average amount of implant present compared with the other groups at 2 weeks. The degree of osteoneogenesis was similar among the P-GF, P-C, and P-MG groups. The P-MG and P-C groups contained the lowest amount of fibrosis between the implant and surrounding middle ear structures. This study demonstrates promising results with P-C as a potential supportive packing material for otologic procedures. P-C compares favorably with P-MG and P-GF in a guinea pig model with respect to ease of placement and amount of fibrosis.