Numerical Analysis of Stapes Prosthesis Constraining in the Case of Otosclerosis

In the case of otosclerosis, it has been noticed that even though there are a variety of different prostheses on the market, due to the anatomical characteristics, it is not always possible to restore excellent mobility to the ossicles and the prosthesis. On the one hand, this happens because the incus long process and the prosthesis create difficult angles. On the other hand, incus necrosis is among the most common causes of the loss of stability to the prosthesis and stapedectomy failure. The aim of this research is to suggest an improvement for stapes prosthesis stability and numerically evaluate the impact of the prosthesis constraining to its dynamical behavior. Numerical 3D models of a standard as well as a modified (adjustable angled) stapes prosthesis were created in order to achieve this aim. Consequently, the modal analysis has been performed to evaluate the mechanical behavior of the prosthesis, assuming that the piston (thick part) would be made of Teflon, and the thin part, fixated on the incus long process, would be made from titanium alloy. Finally, the numerical analysis has been conducted by changing the boundary conditions in respect of the prosthesis constraining, where the attached stapes prosthesis connects to the ossicular chain. Subsequently, there were two hypotheses raised for the prosthesis loop constraining. The first is that during the surgery, the prosthesis is perfectly crimped with certain looseness. The second is that the prosthesis is outgrown by the tissues over time and thus becomes over-constrained. Then, the analyzed standard stapes prosthesis does not fulfil its functions because of the over-constraining that develops over time. An improvement for the standard stapes prosthesis, i.e., a modified stapes prosthesis (adjustable angled), that has been proposed in this research allows avoidance of the negative effects of the over-constrained standard stapes prosthesis that appear over time. Moreover, the proposed modified prosthesis helps to regain hearing when the angle between the incus long process and prosthesis is unfavorable.

Stapes Prosthesis Length: One Size Fits All?

Background: The insertion of the stapes piston into the vestibule provides the physical basis for a successful stapedotomy. In routine clinical practice, two different ways to handle prosthesis length are performed: (1) an individualized measurement of the stapes prosthesis length or (2) a standard prosthesis length for all cases. Objective: The objective of this study was to compare both ways of handling prosthesis length and the effect of these methods on insertional prosthesis depth. Material and Method: We retrospectively evaluated 39 patients after performing a stapedotomy for radiologically estimated vestibular stapes prosthesis insertion depth. The individual measured length data were hypothetically changed to a standard length of 4.75, 5, 5.25, and 5.5 mm, and the insertion depths were compared. Results: The individually measured prosthesis lengths led to an insertion depth between 0.2 and 1.6 mm (mean 0.74 mm). The ratio of insertion depth/vestibular depth was between 8 and 59.1% (mean 26.6%). The different assumed standard lengths led to different rates of the vestibulum positions and possible bony contacts at the vestibulum floor. Conclusion: The individual measurement led to a zero rate of the vestibulum positions of stapes prosthesis pistons with a low insertion depth/vestibular depth ratio.

Applied Force during Piston Prosthesis Placement in a 3D-Printed Model: Freehand vs Robot-Assisted Techniques

Objectives To describe a 3D-printed middle ear model that quantifies the force applied to the modeled incus. To compare the forces applied during placement and crimping of a stapes prosthesis between the Robotic ENT Microsurgery System ( REMS) and the freehand technique in this model. Study Design Prospective feasibility study. Setting Robotics laboratory. Subjects and Methods A middle ear model was designed and 3D printed to facilitate placement and crimping of a piston prosthesis. The modeled incus was mounted to a 6–degree of freedom force sensor to measure forces/torques applied on the incus. Six participants—1 fellowship-trained neurotologist, 2 neurotology fellows, and 3 otolaryngology–head and neck surgery residents—placed and crimped a piston prosthesis in this model, 3 times freehand and 3 times REMS assisted. Maximum force applied to the incus was then calculated for prosthesis placement and crimping from force/torque sensor readings for each trial. Robotic and freehand outcomes were compared with a linear regression model. Results Mean maximum magnitude of force during prosthesis placement was 126.4 ± 73.6 mN and 105.0 ± 69.4 mN for the freehand and robotic techniques, respectively ( P = .404). For prosthesis crimping, the mean maximum magnitude of force was 469.3 ± 225.2 mN for the freehand technique and 272.7 ± 97.4 mN for the robotic technique ( P = .049). Conclusions Preliminary data demonstrate that REMS-assisted stapes prosthesis placement and crimping are feasible with a significant reduction in maximum force applied to the incus during crimping with the REMS in comparison with freehand.

Successful hearing improvement with direct acoustic stimulation in a patient with schizophrenia

ObjectiveA direct acoustic cochlear implant provides its power directly to the inner ear by vibrating the perilymph via a conventional stapes prosthesis. Our experience with a patient with severe mixed hearing loss due to otosclerosis is described.Case reportThe patient, a 47-year-old male, had a pre-operative speech recognition score of 10 per cent and had been treated for many years for schizophrenia, both of which made him a poor candidate for a direct acoustic stimulation device. Nevertheless, the surgery was performed, which preserved the pre-operative bone conduction level and significantly improved hearing. His speech recognition score rose to 100 per cent. He uses the device all day and his auditory hallucinations have subsided. Improvement of schizophrenia symptoms has enabled the patient to reduce his psychiatric medications intake.ConclusionHearing restoration was the main reason for the reduction of auditory hallucinations in our patient. Hearing loss is a potentially reversible risk factor for psychosis, but this association is often overlooked.