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PubMedDate not supplied

Thoughts on bone biomechanics.

Simple simulations of stresses and strains in several types of localised anatomical features have been modelled using basic biomechanical thinking, experimental stress analysis employing photo-elastic methods and theoretical stress and strain analysis using a finite elements approach where the computational program utilises fast LaGrangian analysis of continua. The studies are providing results showing that, for given load proportions, the particular forms of some bones and bony architectural features seem related to stresses and strains that are relatively evenly distributed across surfaces (and therefore mechanically optimal). The results particularly show how apparently opposite (paradoxical) situations can readily occur within anatomical systems. They also provide strong biological information relevant to the assessment of such features of bone architecture in phylogenetic investigations. They even give information relevant to clinical problems.

Animals↗
PubMed1976

Further observations on the ear in fossorial mammals with special considerations of Chlamyphorus truncatus (Harlan).

The morphology of the external and the middle ear (auditory ossicles) in Chlamyphorus truncatus is influenced by its fossorial life. The external auditory canal consists of three parts. The most distal part is a short (cartilaginous) auricle which reaches anteriorly close behing the eye. Posteriorly to the auricle is a long, thin bony duct which consists of two segments, movable against each other. This tube leads through a narrow porus into the third part of the canal, the recessus meatus, which is enclosed in the bulla. The recessus with the narrow porus is characteristic for many fossorials and has a morphology with physical chracteristics of a resonator (HELMOHOLTZ). The malleus and the stapes in Ch. truncatus are also influenced by fossorial life. Based on the dorsal view of the malleus head, the Xenarthra can be divided into two groups. To the first division belong the Dasypodidae with Chlamyphorinae and Dasypodinae, to the second the Myrmecophagidae and Bradypodidae. The malleus of Cyclopes, a myrmecophagid, differs from that in the other Mymecophaginae and is similar to the malleus in the Dasypodinae. Two kinds of experiments should be undertaken: (a) physiologic-acoustic experiments in a fossorial to determine the effect of the recesses and (b) acoustic experiments varying the dimensions and positions of a tube and a porus leading into a resonator.

Acoustic Stimulation↗
PubMed1988

Morphological variations of human ossicula tympani.

In a series of 100 cases, morphological variations of human ossicula tympani were studied. These have seldom been considered either in classic or recent descriptions. Among them, the malleus and stapes are the most variable ones. A geometric model is proposed to systematically study any variation from the typical ossicles. These morphological variations of ossicles could be related to age, sex, race, and could bring out peculiarities in acoustic transmission.

Ear Ossicles↗
PubMed1992

Functional structure of human auditory ossicles.

In a series of 52 auditory ossicles, their structure and functional significance were studied, with special reference to the patterns of force transmission. The significance of the different degrees of cavitation in the ossicles as well as their eventual pathological significance are also discussed.

Humans↗
PubMed2001

Changes in permeability of strial vessels following vibration given to auditory ossicle by drill.

We produced drill-induced damage of the auditory ossicles of guinea pigs to study changes over time in the permeability of the blood vessels of the stria vascularis to horseradish peroxidase (HRP). In group A, the stimulus was applied for 10 seconds after intravenous injection of HRP. In group B, it was applied for 30 seconds, and in group C, for 60 seconds. The cochlea was fixed with 2% glutaraldehyde perfused through the round window, and the guinea pigs were then decapitated. The stria vascularis of the basal and third turns was examined. The leakage of HRP from the blood vessels of the stria vascularis significantly increased in relation to the duration of the stimulus in both the basal and third turns. The damage to intermediate cells also tended to be in relation to the duration of the stimulus. Extravascular permeation of HRP took place through the tubules in the endothelial cytoplasm. The vibratory stimulation presumably opened channels that are not normally open.

Animals↗
PubMedDate not supplied

Grafting materials and methods in reconstructive ear surgery.

The evolution of tympanic membrane grafting over the past 20 years has been based on biologic tissues of mesodermal origin which contain a collagen matrix. The dominant theme of this evolution has been the modification of these collagen membranes by physical and chemical agents to achieve a more ideal graft. The graft material and the operation should be suited to specific problems. Current operative techniques and graft materials are discussed. It is believed that there will be continued modification and manipulation of collagen in the future to achieve a more ideal graft for tympanic membrane restoration.

Ear Diseases↗
PubMedDate not supplied

Stapedectomy. Postmortem findings.

Histological studies were made of 16 temporal bones of 13 subjects who had stapedectomy operations. Photographs of the prostheses in situ are a special feature of the studies. It was found that prostheses which overlap the margins of the oval window cause incomplete closure of the air-bone gaps. Fibrous adhesions were a common consequence of trauma to the mucous membrane of the middle ear. Gelfoam implantation promotes the formation of thin oval window membranes which tend to bulge out of the oval window. Most incudes show small areas of cortical bone resorption. In at least half the cases the surgical technique of stapedectomy, as judged from these studies, was less than ideal. Surgeons who perform stapedectomy should be cognizant of the relevant surgical pathology and adopt methods which will optimize functional results and minimize complications.

Adult↗
PubMedDate not supplied

Dynamics of otosclerosis-like lesions in LP/J mice.

The LP/J inbred mouse is the first known animal to spontaneously develop otosclerosis-like bone lesions in the middle and inner ear. These abnormal bone foci resemble human otosclerotic lesions, are inherited, and produce a progressive hearing loss. On the basis of histological evaluation alone, it was unclear whether these otosclerosis-like lesions in LP/J mice develop suddenly or gradually as in human otosclerosis. To study the dynamics of lesion formation, four different colored fluorochrome bone labels were given in sequence to postpubertal LP/J mice and CBA/J mice as normal controls. All of the otosclerosis-like lesions incorporated at least one fluorochrome, and half were labeled with two or more markers indicating continuous lesion growth over many weeks. It appears that otosclerosis-like lesions in LP/J mice develop during early adulthood and progress gradually as in human otosclerosis.

Animals↗