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Tympanosclerosis, grommets and shear stresses
T H Lesser1, K R Williams, D W Skinner
1Department of Otolaryngology, University Hospital of Wales, Heath Park, Cardiff.
Clinical Otolaryngology and Allied Sciences
|October 1, 1988
Summary
Grommets used for glue ear treatment can cause tympanosclerosis, a condition affecting the eardrum. Finite element modeling suggests grommet weight increases stress, potentially leading to this condition.
Area of Science:
- Otolaryngology
- Biomedical Engineering
- Pathology
Background:
- Glue ear (otitis media with effusion) is common in children.
- Grommets (ventilation tubes) are frequently inserted to treat persistent glue ear.
- Grommet insertion can lead to tympanosclerosis, a condition characterized by calcified deposits on the eardrum.
Purpose of the Study:
- To investigate the long-term incidence and distribution of grommet-induced tympanosclerosis.
- To identify the biomechanical factors contributing to tympanosclerosis development after grommet insertion.
- To explore potential modifications in grommet design to mitigate this complication.
Main Methods:
- Retrospective review of patients from a controlled trial 15 years after unilateral grommet insertion for bilateral glue ear.
- Computer graphics analysis to map tympanosclerosis distribution.
- Finite element modeling of the tympanic membrane to simulate shear stress distribution.
- Histological review of lamina propria structure and tympanosclerosis changes.
Main Results:
- Tympanosclerosis was observed in specific anterior and posterior regions of the tympanic membrane, forming a characteristic horseshoe shape inferiorly.
- Finite element analysis identified maximal shear stress areas in identical locations to tympanosclerosis.
- The weight of an in-situ grommet was predicted to exacerbate these shear stresses, potentially damaging the tympanic membrane's fibrous layers.
Conclusions:
- Grommet-induced tympanosclerosis appears to be linked to biomechanical stress concentrations on the tympanic membrane.
- The distribution of tympanosclerosis correlates with areas of maximal shear stress.
- Further research into lighter grommet designs may be warranted to reduce the incidence of tympanosclerosis.