Tympanic membrane healing process and biocompatibility of an innovative absorbable ventilation tube.

Objective: To investigate tympanic membrane healing process and biocompatibility of pressure-equalizing (PE) tubes, made of a novel biodegradable, absorbable material, in an animal model.

Background: Myringotomy and pressure-equalizing tube insertion is a frequent otologic procedure in children. However, results may vary because of the unpredictable extrusion rate of tubes. Furthermore, tubes that are no longer required need a surgical procedure to be removed. The ideal pressure-equalizing tube should remain in place for the time selected by the otologist, with no need for subsequent removal. This objective could be met with pressure-equalizing tubes made from a self-disintegrating material.

Methods: Pressure-equalizing tubes, made of poly-bis(ethylalanate)phosphazene, were inserted in 55 ears of 28 Hartley guinea pigs, with survival times of 10, 30, and 60 days after tube insertion. In vivo reactions between the poly-bis(ethylalanate)phosphazene pressure-equalizing tubes and the tympanic membrane were studied. Tympanic membranes, middle ears, and tubes were examined by scanning electron microscopy.

Results: There was neither infection nor inflammatory reaction to the tube in any animal. The healing process of tympanic membranes revealed neither residual perforation nor inward spread of skin epithelium into the middle ear cavity. At 30 days, 53% of the tubes had disintegrated. At 60 days, tubes were functioning in 25% of ears.

Conclusion: These new poly-bis(ethylalanate)phosphazene pressure-equalizing tubes are promising. The healing process of tympanic membranes is excellent, with no complications. The tube disintegration rate can be controlled by varying the formulation of the polymer, obtaining tubes with predictable resorption rates, to adapt treatment to the needs of each single patient.