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Hypothesis: In the literature several surgical methods have been reported that aim to improve hearing in patients with isolated malleus fractures; however, it is still not clear which method gives the best results. Background: In this study, laser Doppler vibrometry (LDV) was used to compare the outcome of different surgical methods on malleus fractures in fresh frozen human temporal bones. Methods: Fractured malleus shafts of defrosted human temporal bones were repaired with bone cement, with a malleus prosthesis from cortical bone, or with a partial ossicular replacement prosthesis (PORP) from cortical bone, and LDV measurements were obtained for analysis. Results: The best result was achieved with the bone cement only, applied directly at the site of the fracture. The malleus prosthesis and the PORP gave similar results. Conclusion: All three surgical methods gave good results, but when the distal end of the fractured malleus can be attached close to the proximal end, the technique using only cement tends to be the best option. If the parts are too far apart, a malleus prosthesis or a PORP would be good options.

Udgivelsesdato: 2010 HYPOTHESIS:: Middle ear pressure (MEP) is actively regulated by both the Eustachian tube and the mastoid air cell system. BACKGROUND:: MEP is a highly significant factor involved in many clinical conditions related to otitis media. Basic knowledge on its overall regulation remains insufficient, but the Eustachian tube and mastoid gas exchange are important factors. The main focus has been aimed at the tube; however, evidence points to the mastoid as equally important. More detailed methods are demanded to study their complementary functions. METHODS:: A catheter was inserted into the mastoid of 12 human volunteers (patients for parotidectomy). This enabled monitoring MEP directly, and experiments were performed with volume displacements of +/-50, 100, and 200 mul resulting in a range of overpressure and underpressure. The following counter-regulation was recorded over 10 minutes. RESULTS:: In some cases, MEP counter-regulation presented as Eustachian tube openings with steep and fast pressure changes toward 0 Pa, whereas in others, gradual and slow pressure changes presented related to the mastoid; these changes sometimes crossed 0 Pa into opposite pressures. In many cases, combinations of these distinct mechanisms were found. CONCLUSION:: The human mastoid as well as the Eustachian tube was capable of active counter-regulation of the MEP in short-term experimental pressure changes in healthy ears. Thus, these 2 systems seemed to function in a complementary way, where the mastoid was related to continuous regulation of smaller pressures, whereas the tube was related to intermittent regulation of higher pressures.

Hypothesis: The short-term healing scar that forms after experimental laser myringotomy will revert to a normal lamina propria in the long run. The mechanical stiffness will stay normal. Background: Recent studies have shown severe structural changes in the fibrous layer in the early course after experimental laser myringotomy, whereas the scar quickly restored the strength of the tympanic membrane (TM). A reorganization of the fiber layer is expected to occur. Methods: Potassium titanyl phosphate laser myringotomy was made on one side of the TM in Sprague-Dawley rats. The ear of the other side was untouched and used for control. After half a year of observation, the stiffness and strength of the healed TNls were measured with moire interferometry and examined with otomicroscopy and light and electron microscopy. Results: The interferometry readings showed a slightly reduced strength in the myringotomized and healed TMs. After half a year, still there were immense structural changes including increased thickness over a wide area of the pars tensa with increased amounts of fibers. An obvious reorganization of the fiber layer was lacking. Conclusion: Laser myringotomy causes profound, long-standing, or permanent structural changes in the lamina propria of the pars tensa, whereas the strength of the TM may become slightly reduced.

Hypothesis: Our hypothesis is that otitis media with effusion causes stiffness loss in the pars flaccida of the tympanic membrane. This loss of stiffness may be persistent and may trigger the development of retraction pockets and cholesteatoma. Background: Otitis media with effusion is a very common disease in childhood. It can cause minor to moderate hearing loss and delayed speech development. Otitis media with effusion is a risk factor for retraction pocket formation. Methods: Otitis media with effusion was induced unilaterally in 15 gerbils by obstructing the eustachian tube with glue. The contralateral ears served as normal controls. As a measure of mechanical stiffness, pars flaccida peak displacement versus pressure was used. The displacement measurements were made with moire interferometry. This is a noncontacting optical technique with which the displacement of an object can be measured in real time. Results: The mean peak displacement of the pars flaccida in the group with otitis media with effusion was increased threefold as compared with normal controls. This difference was statistically significant. Conclusion: There was a loss of mechanical stiffness in the pars flaccida caused by otitis media with effusion. This loss of stiffness may be persistent and may predispose for retraction pocket formation and cholesteatoma development.

The aim of the current study was to assess the mechanical stiffness properties of the normal pars flaccida and to compare the results with those obtained in earlier studies on the pars tensa.Postinflammatory changes such as retraction pockets and cholesteatoma develop in the pars flaccida as well as in the pars tensa of the tympanic membrane. In these authors' previous experimental studies, stiffness changes are shown to develop early in the pars tensa in response to purulent otitis media and otitis media with effusion. These changes are suggested to be precursors to a later development of retraction pockets and cholesteatoma. In the clinical situation, retraction pockets are often found in the pars flaccida only. This study will establish the stiffness properties of the normal pars flaccida and form a base for forthcoming studies of the pars flaccida in response to otitis media with effusion and purulent otitis media, as well as retraction pocket formation and cholesteatoma.A measure for the mechanical stiffness properties of the normal pars flaccida in the gerbil was assessed as its displacement for a given transtympanic pressure. The method used was moiré interferometry, which is a noncontacting optical technique to measure the shape of the surface of an object.The displacement of the pars flaccida was a nonlinear and asymmetric function of pressure. The displacement per pressure unit rose steeply at low middle ear pressures to level out and reach a steady state at higher pressures. The displacement versus pressure characteristics for the pars flaccida strongly differed from those of the pars tensa. The pars tensa seemed more elastic.Reference values for displacement versus pressure characteristics of the normal gerbil pars flaccida were obtained using a moiré interferometry method. The mechanical stiffness properties of the normal pars flaccida were strongly different from those of the pars tensa.