The extrusion rate of grommets.

A prospective study was performed to determine the factors influencing the extrusion rate of tympanostomy tubes. Nine hundred thirty-nine tubes were inserted in 589 patients and the extrusion of these tubes was reviewed up to a period of 27 months. The eight tubes used in the survey were the Shepard, Exmoor, Bobbin, Armstrong, Paparella, Shah, Arrow, and collar button. These tubes were inserted in strict rotation, the operator using the designated tube. The position, type of incision, presence of fluid, quality of tympanic membrane, and degree of difficulty of insertion were all recorded at operation. The sex, age, side of operation, and any simultaneous operative procedures were also recorded. The patients were reviewed the day after operation and then every 3 months thereafter until the tube was extruded. A definite pattern was identified for the extrusion of each type of tube. At one end of the spectrum, Exmoor and Shepard tubes were, for the most part, extruded between 6 and 9 months after insertion, while at the other end, most of the collar button tubes were still functioning at 18 months. The design of the tube was the only factor found to be a significant determinant of the extrusion of the tube, although the experience of the surgeon affected the extrusion rate of the Arrow tube. The different dimensions of the Exmoor and collar button tubes are examined and compared.