Force prediction in the cylindrical grip for a model of hand prosthesis.

The aim of this paper is to present an analytical method of calculating forces acting on the thumb, index, middle finger, and metacarpal part of a hand prosthesis in a cylindrical grip. This prehension pattern represents a common operation of grabbing and manipulating everyday life objects. The design process assumed that such a prosthesis would have 5 fully operating fingers and 18 total degrees of freedom: three for each finger including the thumb, and another three for the wrist. The assumed load was 1 kg and the diameter equaled 70 mm, representing a water bottle. The method was based on analytical mechanics and as opposed to experiments or numerical methods does not require many resources. The calculations involved solving a system with seven unknown forces using an equilibrium equation for forces and moments in all three axes. The resulting equations were presented in a matrix form and solved using MATLAB software. The validation of the method with an experiment using FSR sensors and comparing it to other reports showed differences in index and middle finger involvement. However, the total sum of forces was similar, therefore it is reasoned that the grip can be performed and the prediction was accurate for the thumb and metacarpal. When using the model, the friction coefficient must be chosen with a safe margin as it influences the grip force. The presented method can be used for other models and designs by inserting their dimensions into the equations and solving them numerically to obtain forces useful in mechatronics design.

Muscle Force Patterns in Lower Extremity Muscles for Elite Discus Throwers, Javelin Throwers and Shot-Putters - A Case Study.

Optimal release variables, as well as the kinematics and kinetics of athletes, are crucial for the maximization of throwing distance in athletics. Mathematical models and simulations allow throwing techniques to be studied. However, muscle force patterns and the contribution of specific muscle groups in athletics throwing events are not well understood and require detailed research. In this study, important variables of the muscle force generated during the javelin, discus and shot put events were determined using OpenSim software. Musculoskeletal simulations were carried out based on kinematic and kinetic data collected using the Vicon system and Kistler plates with the help of nine top Polish athletes (three in each event). OpenSim software was used to calculate muscle forces and joint velocities. For each discipline, it was found that the main muscle groups involved in the throwing movement were better at distinguishing throwers than joint velocities. The contribution of right ankle plantar flexors at the beginning of the final acceleration phase as well as left hip extensors at the end of the final acceleration phase was given special attention. This work provides a better understanding of the techniques used in athletics throws. Musculoskeletal simulations of throwing styles might help coaches analyze the techniques of individual athletes, resulting in better adjustment of training programmes and injury prevention protocols.

Effectiveness of Bone Conduction Stimulation Applied Directly to the Otic Capsule Measured at Promontory: Assessment in Cadavers.

INTRODUCTION: The aims of this study included: (a) to develop a method of direct acoustic bone conduction (BC) stimulation applied directly to the otic capsule, (b) to investigate the effect of different stimulation sites on the promontory displacement amplitude, and (c) to find the best stimulation site (among 2 located directly on the otic capsule and 1 standard site approved for clinical use) that provides the greatest transmission of vibratory energy. METHODS: Measurements were performed on 9 cadaveric whole human heads. A commercial scanning laser Doppler vibrometer was used. The promontory displacement was recorded in response to BC stimulation delivered by an implant at 3 sites: BC1 on the squamous part of the temporal bone, BC2 on the ampulla of the lateral semicircular canal, and BC3 between the semicircular canals. The displacement of the promontory was analyzed in detail. RESULTS: The results show that BC1 caused an overall smaller promontory displacement than both sites BC2 and 3. BC3 stimulation is more efficient than that at BC2. CONCLUSIONS: BC is an effective method of acoustic stimulus delivery into the inner ear, with the effectiveness increasing when approaching closer to the cochlea. Placing the implant directly on the labyrinth and thus applying vibrations directly to the otic capsule is possible and very effective as proved in this study. The results are encouraging and represent the potential of new stimulation sites that could be introduced in the field of BC hearing rehabilitation as the possible future locations for implantable BC hearing devices.

Bone Conduction Stimulation Applied Directly to the Otic Capsule: Intraoperative Assessment in Humans.

OBJECTIVES: Aim was to investigate the innovative method of direct acoustic bone conduction (BC) stimulation applied directly to the otic capsule and measured intraoperatively by promontory displacement in living humans. The objective was to find the best stimulation site that provides the greatest transmission of vibratory energy in a living human and compare it with the results previously obtained in cadavers. DESIGN: The measurements were performed in 4 adult patients referred to our department for vestibular schwannoma removal via translabyrinthine approach. The measurements were performed in the operated site. The cadaver data were obtained in our previous study and here they are reanalyzed for comparison. Promontory displacement was measured using a commercial scanning laser Doppler vibrometer. The laser Doppler vibrometer points located on the promontory were used to analyze the promontory displacement amplitude. Cochlear stimulation was induced with BC stimulation through an implant positioned at three sites. The first site was on the skull surface at the squamous part of the temporal bone (BC No. 1), the second at the bone forming the ampulla of the lateral semicircular canal (BC No. 2), and the third between the superior and lateral semicircular canals (BC No. 3). BC No. 2 and BC No. 3 were located directly on the otic capsule. Four frequencies in total were tested (500, 1000, 2000, and 4000 Hz), one at a time. RESULTS: In patients, the detailed analysis of promontory displacement amplitudes revealed the BC No. 1 magnitude to be the smallest and significantly different from BC No. 2 and No. 3 at all measured frequencies. Transmission of vibratory energy at BC No. 2 and BC No. 3 was the most effective and similar with a small and insignificant difference at 500, 1000, and 4000 Hz, and a significant difference at 2000 Hz. The results observed in cadavers were similar to those in living humans. However, a few differences were observed when comparing patients and cadavers. Small and insignificant differences were found for BC No. 1. Almost the same results were obtained for BC No. 2 and BC No. 3 in cadavers as in living humans, with only BC No. 3 measurements results at 500 Hz at the limit of statistical significance, with no other significant differences observed. CONCLUSIONS: The results of this study indicate that the promontory vibration amplitude increases when the BC stimulation location approaches the cochlea. BC No. 1 stimulation located on the squama caused overall smaller displacement than both BC No. 2 and No. 3 screwed to the ampulla of the lateral semicircular canal and to the midpoint between the semicircular canals, respectively. In our opinion, the results of BC stimulation applied directly to the otic capsule present a potential new stimulation site that could be introduced in the field of BC hearing rehabilitation.

Bone conduction stimulation of the otic capsule: a finite element model of the temporal bone.

PURPOSE: Bone conduction stimulation applied on the otic capsule may be used in a conductive hearing loss treatment as an alternative to the bone conduction implants in clinical practice. A finite element study was used to evaluate the force amplitude and direction needed for the stimulation. METHODS: A finite element model of a female temporal bone with a precisely reconstructed cochlea was subjected to a harmonic analysis assuming two types of stimulation. At first, the displacement amplitude in the form of air conduction stimulation was applied on the stapes footplate. Then the force amplitude was applied on the otic capsule in the form of bone conduction stimulation. The two force directions were considered: 1) the primary direction, when a typical opening is performed during mastoidectomy, and was coincident with the axis of an imaginary cone, inscribed in the opening, and 2) the direction perpendicular to the stapes footplate. The force amplitude was set so that the response from the cochlea corresponded to the result of air conduction stimulation applied on the stapes footplate. RESULTS: The amplitude and phase of vibration and the volume displacement on the round window membrane were considered as well as vibrations of the basilar membrane, spiral lamina, and promontory. CONCLUSIONS: The cochlear response was comparable for the two types of stimulation. The efficiency of bone conduction stimulation depended on the force direction. For the primary direction, the force was a few times smaller than for the direction perpendicular to the stapes footplate.

Round Window Membrane Motion Induced by Bone Conduction Stimulation at Different Excitation Sites: Methodology of Measurement and Data Analysis in Cadaver Study.

OBJECTIVES: The aim of this study was to investigate the following: (1) the vibration pattern of the round window (RW) membrane in human cadavers during air (AC) and bone conduction (BC) stimulation at different excitation sites; (2) the effect of the stimulation on the fluid volume displacement (VD) at the RW and compare the VD between BC and AC stimulation procedures; (3) the effectiveness of cochlear stimulation by the bone implant at different excitation sites. DESIGN: The RW membrane vibrations were measured by using a commercial scanning laser Doppler vibrometer. The RW vibration amplitude was recorded at 69 measurement points evenly distributed in the measurement field covering the entire surface of the RW membrane and a part of the surrounding bony surface. RW vibration was induced first with AC and then with BC stimulation through an implant positioned at two sites. The first site was on the skull surface at the squamous part of the temporal bone (implant no. 1), a place typical for bone-anchored hearing aids. The second site was close to the cochlea at the bone forming the ampulla of the lateral semicircular canal (implant no. 2). The displacement amplitude (dP) of the point P on the promontory was determined and used to calculate the relative displacement (drRW) of points on the RW membrane, drRW = dRW - dP. VD parameter was used to analyze the effectiveness of cochlear stimulation by the bone implant screwed at different excitation sites. RESULTS: RW membrane displacement amplitude of the central part of the RW was similar for AC and BC implant no. 1 stimulation, and for BC implant no. 2 much larger for frequency range >1 kHz. BC implant no. 2 causes a larger displacement amplitude of peripheral parts of the RW and the promontory than AC and BC implant no. 1, and BC implant no. 1 causes larger than AC stimulation. The effect of BC stimulation exceeds that of AC with identical intensity, and that the closer BC stimulation to the otic capsule, the more effective this stimulation is. A significant decrease in the value of VD at the RW is observed for frequencies >2 kHz for both AC and BC stimulation with BC at both locations of the titanium implant placement. For frequencies >1 kHz, BC implant no. 2 leads to a significantly larger VD at the RW compared to BC implant no. 1. Thus, the closer to the otic capsule the BC stimulation is located, the more effective it is. CONCLUSIONS: Experimental conditions allow for an effective acoustic stimulation of the inner ear by an implant screwed to the osseous otic capsule. The mechanical effect of BC stimulation with a titanium implant placed in the bone of the ampulla of the lateral semicircular canal significantly exceeds the effect of an identical stimulation with an implant placed in the temporal squama at a conventional site for an implant anchored in the bone. The developed research method requires the implementation on a larger number of temporal bones in order to obtain data concerning interindividual variability of the observed mechanical phenomena.

Design of a resilient ring for middle ear's chamber stapes prosthesis.

This paper presents the process of designing a new elastic element replacing a membrane in the chamber stapes prosthesis (ChSP). The results of the study are volume displacement characteristics obtained for the prosthesis and physiological stapes. Simulation tests on a 3D CAD model have confirmed that a properly designed ring can stimulate perilymph with the same or greater efficacy as the physiological stapes footplate placed on the elastic annular ligament. The ChSP with a new elastic element creates a good chance of improving hearing in patients suffering from otosclerosis.

New chamber stapes prosthesis - A preliminary assessment of the functioning of the prototype.

Piston-stapedotomy is the most common method for hearing restoration in patients with otosclerosis. In this study, we have experimentally examined a prototype of a new chamber stapes prosthesis. The prototype was implanted in a human cadaver temporal bone. The round window vibrations before and after implantation were measured for the acoustic signal (90 dB SPL, 0.8-8 kHz) in the external auditory canal. In comparison with a 0.4-mm piston prosthesis, the chamber prosthesis induced significantly higher vibration of the round window, especially for frequencies above 1.5 kHz. Based on the results, it can be surmised that stapedotomy with a chamber stapes prosthesis could provide better hearing results in comparison with the piston-stapedotomy.

Biocompatible membrane of PDMS for the new chamber prosthesis stapes.

Stapes protheses are designed for patients with otosclerosis resulting immobilization or significant reduction of the stapes mobility. All currently used prostheses are called - piston prosthesis. However, its use to stimulate the cochlea is still imperfect. New chamber stapes prosthesis allows the perilymph excitation more effective than the piston prothesis. Moreover, the chamber prosthesis eliminates the common causes of piston-stapedotomy failures. The most important element of the new prosthesis is a flexible membrane. The membrane stiffness should be close to the stiffness of normal annular ligament. This work presents the process of selection of the membrane's thickness and its manufacturing technology. Method A 3D model of the chamber stapes prosthesis was build using Autodesk Inventor 2015. The model was imported to Abacus 6.13 computing environment. During numerical simulations, displacements corresponding to applied loads were calculated and the membrane thickness was adjusted so that its stiffness was the same as the ligament stiffness (~ 120 N/m). The compliance ratios calculated from the load-displacement curves for the membrane and the annular ligament were verified using linear regression analysis. After determining the thickness, the manufacturing technology of the membrane was developed. Results The best similarity between the membrane's and annular ligament's stiffness was achieved for PDMS membrane with the 0,15- mm thickness (similarity ratio R2=0,997752). In this work, the technological parameters of spin-coating process for membrane manufacture are also presented. Summary The proper functioning of the chamber stapes prosthesis requires the PDMS membrane with a thickness of 0,15 mm. The 0,15-mm membrane has the tiffness close to the stiffness of the normal annular ligament. Therefore, the chamber stapes prosthesis provides the perilymph stimulation at the level comparable to the healthy ear. New prosthesis is currently under pre-clinical investigation to optimize the shape of the inner chamber's surface.

Elastic Properties of the Annular Ligament of the Human Stapes--AFM Measurement.

Elastic properties of the human stapes annular ligament were determined in the physiological range of the ligament deflection using atomic force microscopy and temporal bone specimens. The annular ligament stiffness was determined based on the experimental load-deflection curves. The elastic modulus (Young's modulus) for a simplified geometry was calculated using the Kirchhoff-Love theory for thin plates. The results obtained in this study showed that the annular ligament is a linear elastic material up to deflections of about 100 nm, with a stiffness of about 120 N/m and a calculated elastic modulus of about 1.1 MPa. These parameters can be used in numerical and physical models of the middle and/or inner ear.

Effect of different stapes prostheses on the passive vibration of the basilar membrane.

The effect of different stapes prostheses on the basilar membrane (BM) motion was determined. To that end, a three dimensional finite element (FE) model of the passive human cochlea was developed. Passive responses of the BM were found based on coupled fluid-structure interactions between the cochlear solid structures and the scala fluids. The passive BM vibrations in normal (healthy) cochlea were compared with vibrations in the cochlea in which a 0.4-mm piston or a proposed new type of prosthesis was implanted. The proposed chamber prosthesis was not experimentally implanted, but only numerically simulated. Design of the new chamber stapes prosthesis is presented for the first time in this paper. The simulation results showed 10-20 dB decrease in BM displacement amplitude in the case of the piston. In contrast, the BM responses in the cochlea with the new prosthesis are higher with respect to the healthy ear. The results obtained in this study are promising for further research to optimize the design of the new chamber stapes prosthesis.

A three-dimensional finite element model of round window membrane vibration before and after stapedotomy surgery.

Piston stapes prostheses are implanted in patients with refractory conductive or mixed hearing loss due to stapes otosclerosis to stimulate the perilymph with varying degrees of success. The overclosure effect described by the majority of researchers affects mainly low and medium frequencies, and a large number of patients report a lack of satisfactory results for frequencies above 2 kHz. The mechanics of perilymph stimulation with the piston have not been studied in a systematic manner. The objective of this study was to assess the influence of stapedotomy surgery on round window membrane vibration and to estimate the postoperative outcomes using the finite element (FE) method. The study hypothesis is that the three-dimensional FE model developed of the human inner ear, which simulates the round window (RW) membrane vibration, can be used to assess the influence of stapedotomy on auditory outcomes achieved after the surgical procedure. An additional objective of the study was to enable the simulation of RW membrane vibration after stapedotomy using a new type of stapes prosthesis currently under investigation at Warsaw University of Technology. A three-dimensional finite element (FE) model of the human inner ear was developed and validated using experimental data. The model was then used to simulate the round window membrane vibration before and after stapedotomy surgery. Functional alterations of the RW membrane vibration were derived from the model and compared with the results of experimental measurements from temporal bones of a human cadaver. Piston stapes prosthesis implantation causes an approximately fivefold (14 dB) lower amplitude of the RW membrane vibrations compared with normal anatomical conditions. A satisfactory agreement between the FE model and the experimental data was found. The new prosthesis caused an increase of 20-30 dB in the RW displacement amplitude compared with the 0.4-mm piston prosthesis. In all frequencies, the FE model predicted a RW displacement curve that was above the experimental curves for the normal ear. The stapedotomy can be well simulated by the FE model to predict the auditory outcomes achieved following this otosurgery procedure. The 3D FE model developed in this study may be used to optimize the geometry of a new type of stapes prosthesis in order to achieve a similar sound transmission through the inner ear as for a normal middle ear. This should provide better auditory outcomes for patients with stapedial otosclerosis.

Differences in the perilymph fluid stimulation before and after experimental stapedotomy.

A stapedotomy surgery using a piston stapes prosthesis significantly modifies the perilymph fluid stimulation level and always leads to alteration of conditions in sound transmission through the cochlea. This paper shows the results of non-contact measurements of the stapes head velocity, a Teflon piston stapes prosthesis velocity and round window velocity conducted in freshly harvested human cadaver temporal bone specimens. The vibration patterns were measured within the frequency range of 0.4-10 kHz at the sound pressure level of 90 dB administered to the external auditory canal in the same specimen before and after experimental stapedotomy. It was shown that the vibrations of the stapes Teflon piston prosthesis and the physiological stapes are similar and approximately five-fold lower amplitude of the round window membrane vibrations compared to a physiologic situation is caused by piston shape of the stapes prosthesis. The results in this report are the part of a larger study designed to develop a new type of chamber stapes or whole middle ear prosthesis.

Round window membrane motion before and after stapedotomy surgery - an experimental study.

This paper presents the results of non-contact measurements of the human ear round window (RW) membrane motion in freshly harvested human cadaver temporal bone specimens. A PSV 400 Scanning Laser Vibrometer system (Polytec, Waldbronn, Germany) was used to determine the effect of stapedotomy on the sound-induced displacement amplitude of the RW membrane. The vibration patterns were measured in the frequency range of 0.4-10 kHz in four specimens with air conduction stimulation at 90 dB SPL applied to the external auditory canal. It was shown that the vibration amplitude of the RW membrane after stapes piston prosthesis implantation, in comparison with a physiological specimen, was reduced several times. The motion of the RW membrane can be used to determine the cochlear stimulation for the evaluation of middle ear ossicle reconstruction, especially in the case of otosclerosis surgery.

Comparison of round-window membrane mechanics before and after experimental stapedotomy.

BACKGROUND: Surgical intervention within the area of the middle ear always leads to alteration of conditions in its biomechanical system. This fact may provide an explanation for the lack of expected auditory outcome, although an apparently good anatomic outcome was obtained. In the case of stapedotomy, the majority of patients report lack of satisfactory results for frequencies above 2,000 Hz. The effect has not been experimentally investigated yet. METHODS: This study, conducted in four human temporal bones, yielded a record of round-window membrane vibration amplitude and phase in the frequency function (400 Hz-10 kHz) at the sound intensity level of 90 dB administered to the external auditory canal in a physiologic condition and following implantation of a Teflon piston stapes prosthesis. The procedure of experimental stapedotomy was performed with the tympanic membrane preserved from the maximally dilated approach through the posterior tympanotomy. RESULTS: Stapes Teflon piston prosthesis implantation was found to cause approximately fivefold lower amplitude of round-window membrane vibrations compared to a physiologic situation for frequencies above 2 kHz in particular. CONCLUSIONS: After stapedotomy, with the use of a Teflon piston prosthesis, stimulation of inner ear structures diminishes, especially in higher frequencies.