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Frontiers in Bioengineering and... 2022The middle ear is part of the ear in all terrestrial vertebrates. It provides an interface between two media, air and fluid. How does it work? In mammals, the middle ear... (Review)
Review
The middle ear is part of the ear in all terrestrial vertebrates. It provides an interface between two media, air and fluid. How does it work? In mammals, the middle ear is traditionally described as increasing gain due to Helmholtz's hydraulic analogy and the lever action of the malleus-incus complex: in effect, an impedance transformer. The conical shape of the eardrum and a frequency-dependent synovial joint function for the ossicles suggest a greater complexity of function than the traditional view. Here we review acoustico-mechanical measurements of middle ear function and the development of middle ear models based on these measurements. We observe that an impedance-matching mechanism (reducing reflection) rather than an impedance transformer (providing gain) best explains experimental findings. We conclude by considering some outstanding questions about middle ear function, recognizing that we are still learning how the middle ear works.
PubMed: 36299283
DOI: 10.3389/fbioe.2022.983510 -
Advances in Oto-rhino-laryngology 2018Middle ear hearing reconstruction is unpredictable. Difficulties arise because of host factors, such as ventilation or scarring, surgical technique factors, such as... (Review)
Review
Middle ear hearing reconstruction is unpredictable. Difficulties arise because of host factors, such as ventilation or scarring, surgical technique factors, such as prosthesis placement and stabilization, and design and mechanical factors influencing the properties of the prosthesis. Often there is a balancing act between choosing optimal stability, and maximizing the mechanical vibrations of the prosthesis. We review our and other investigators' work, in design and ideal placement of middle ear prostheses. Middle ear prostheses need to be rigid enough to deliver acoustic forces without bending. Prosthesis mass has a modest effect at higher frequencies. A key point is that rotational movements of the prosthesis have to be constrained. Prosthesis head size and cartilage interposition, within reason, have little effect on vibration transmission. Reconstruction to the malleus may have some small mechanical advantage; however this is not clearly proven. Similarly, there is no proven advantage in reconstructing to the stapes head instead of the footplate. The most important factor for good long term results is probably the stability of the prosthesis, both to acute inertial forces such as trauma, and to slower term changes such as tympanic membrane position and scarring contractures.
Topics: Humans; Ossicular Prosthesis; Ossicular Replacement; Prosthesis Design
PubMed: 29794433
DOI: 10.1159/000485545 -
Clinics in Podiatric Medicine and... Jan 2016Hallux malleus is a deformity of the great toe. There is a dorsiflexion contracture at the metatarsophalangeal joint and plantar flexion of the interphalangeal joint.... (Review)
Review
Hallux malleus is a deformity of the great toe. There is a dorsiflexion contracture at the metatarsophalangeal joint and plantar flexion of the interphalangeal joint. The deformity is commonly attributed to muscular imbalances of the various structures acting on the great toe. Jones tendon transfer is a procedure used to remove the deforming force to the clawed hallux. It is most often performed in conjunction with a hallux interphalangeal joint fusion. Typically there is a neurologic component causing a deformity to the entire foot, necessitating adjunct procedures. The Jones tendon transfer has shown to have reproducible results.
Topics: Hammer Toe Syndrome; Humans; Tendon Transfer
PubMed: 26590724
DOI: 10.1016/j.cpm.2015.06.004