[Movements of the ossicular chain during changes in static pressure]

The effects of static pressure on the movements of the ossicles have been a neglected aspect of reconstruction of the ossicular chain. The pattern and the magnitude of the movement of the intact ossicular chain during changes in static pressure described. Displacement of the handle of the malleus was also measured in three points after removing of the incus. Experiments were carried out on 7 fresh human temporal bones. Digital photographs were taken during incremental changes of static pressure from -500 to +500 daPa. Digital videos were recorded to analyse the pattern of the movement. Minimal displacement of the handle of the malleus for negative pressure was 108 microm for -100 daPa and 200 microm for -500 daPa. Maximal displacement for negative pressure was 209 microm for -100 daPa and 439 microm for -500 daPa. Minimal displacement for positive pressure was 82 microm for 100 daPa and 150 microm for 500 daPa. Maximal displacement for positive pressure was 126 microm for 100 daPa and 237 microm for 500 daPa. Malleus displacements were greater for negative pressure changes than positive pressure (p<0.01). When 500 daPa was applied medial displacement of the middle of the handle of the malleus was smaller for 30 microm and the displacement of the region of lateral process of the malleus was smaller for 94 microm than the displacement of the umbo of the drum. The lateral to medial movement of the malleus during changes in static pressure is converted into a predominantly superior to inferior movement of the incus.