[The biomechanical prerequisites for the preservation of stapedius muscle tendon during stapedoplasty].

The objective of the present biomechanical and clinical study was to evaluate the consequences of the preservation of stapedius muscle tendon during stapedoplasty. The biomechanical investigations included mathematical simulation with the construction of the model based on the kinematic approach. The comparative clinical study of the results of stapedoplasty carried out between 2001 and 2010 involved 340 patients (77 men and 263 women) at the mean age of 48.18 years. Twenty patients underwent piston stapedoplasty by the method of Shi, 320 ones were treated by stapedoplasty with the preservation of stapedius muscle tendon. The state of speech hearing and the audiometric air-bone gap (ABG) were deduced from the audiograms. The biomechanical study demonstrated a significant increase in the range of the movements of the long crus of the incus, after the removal of the stapedius tendon muscle and the preservation in part of the acoustic reflex in case of tendon preservation. The preservation of the tendon partly dampened excessive sound vibrations. The clinical study revealed the improvement of speech hearing parameters throughout the three-year postoperative follow-up period; it was especially pronounced within the first year after surgery with the preservation of stapedius muscle tendon. The size of ABG at a the frequencies falling in the 0.5-1 kHz and 6-8 kHz ranges after surgery with the preservation of stapedius muscle tendon was smaller than after the removal of the tendon during the three-year follow-up (p<0.005). The difference was especially well-apparent within the first year after stapedoplasty. The difference in this parameter between the interventions with the preservation of stapedius muscle tendon and with its removal was insignificant (p>0.05).

[Peculiarities of stapes functioning in the patients presenting with otosclerosis from the standpoint of biomechanical modeling].

The objective of the present study was to elucidate, in the framework of a biomechanical model, the biomechanical prerequisites for the development of osteodystrophic changes in stirrup bones in the case of their osteodystrophic fixation. The comparative analysis of the biomechanical models of mobile and ankylotic stapes demonstrated that the mild enough strain-stress state under the normal conditions turns into the rigid state in otosclerosis. The main dampher in case of load application to the adequately mobile stapes footplates is the round ligament. If the stapes footplates are fixed in the oval window of the labyrinth the conditions for the functioning of this bone change drastically. Variations of the strain-stress state of the ankylotic stapes footplates undergoing the acoustic impact promotes the development of dystrophic processes in the bone structures in response to the altered conditions of functioning and the appearance of supraphysiological strains and stresses.