Biomedical subjects
Publications and source records attributed to T H Lesser.
Dyskeratosis congenita is a multisystem disorder with an increased incidence of neoplasia and opportunistic infections. A case is reported as a cause of complete nasopharyngeal atresia.
Alloplastic materials have been used in middle ear reconstruction since 1952. Biologically, biomaterials and specifically ceramics can be defined as being bioinert, bioactive or biodegradable; these terms being descriptive of the biochemical response provoked by the material in the host tissue. Various ceramics, carbons and polymers and their reactions have been studied by the author and his colleagues over the past 5 years utilising animal implantation and fibroblast culture studies aligned with experience from clinical usage. The qualities of the ideal alloplastic implant namely: biocompatibility, stabilisation and incorporation, the consistency of the implant and bioactive bonding and the biofunctionality or mechanics, are applied to the materials currently available. No single alloplastic material fulfills all criteria, the problems encountered in relation to the biomaterials are reported. A better understanding of the microstresses, fatigue and microfractures is necessary, before the ideal alloplastic biomaterial becomes available.
The recent introduction of the Fisch II spandrel total ossicular replacement prosthesis (TORP), has provided impressive initial hearing benefits in patients. The design, based on a combination of soft plastic and a highly flexible metal shaft, has been analysed in terms of its sound collecting and conducting behaviour using the finite element method. The analysis has examined the mode shapes, displacements and natural frequencies of the prosthesis for a variety of material properties and geometries. The results indicate the optimum vibration characteristics are obtained with a Polycell elastic modulus of 100 N/mm2, with the natural frequency independent of modulus above this value. Furthermore, the diameter of the spandrel shaft is crucially important, with an increase in magnitude of the first natural frequency of 54% for a 25% increase in shaft diameter. At a Polycell membrane thickness of 0.07 mm and a shaft diameter of 0.12 mm, the tympanic membrane and Fisch II prosthesis have almost identical frequencies over the 1st to 6th frequency range. This fact, together with the flexibility of clinical procedures involved in its use, may be the reason for its success.
The normal anatomy and physiology of the middle ear is not reproduced in ossiculoplasty and an artificial mechanism for the transmission of sound results. This is true for all types of graft, be they of natural or man-made material. There are, therefore, 2 areas for consideration when looking at the problems encountered in such reconstructions: first, the materials' biocompatability and, secondly, the mechanical effects of the positioning of the graft in the reconstructed ossicular chain. The present work examines these mechanical effects using the finite element method to determine stress and displacement levels in the reconstructed ossicular chain. It is found that the stress levels at the implant-stapedial joint increases as the implant is gradually moved down the malleus. In contrast there is thought to be an increase in sound transmission as the implant is moved down the malleus. Changes in rigidity and hardness of the implant appear to make only modest stress attenuations at the implant-stapes interface.
A tumour of the singular nerve was found on examination of the temporal bones of a child who died 13 months after meningitis. The tumour consisted of a main mass with the appearance of an acoustic neuroma but close by and not connected were some nests of tumour cells inside the vestibule. This very unusual finding raises questions of the aetiology of this tumour which may have a bearing on the aetiology of other tumours of the VIIIth. nerve.
The manifestations of Lyme disease as they may present to the ENT surgeon are discussed. The most important ENT symptom is facial palsy. Particularly when combined with other cranial palsies, systemic illness or signs of meningeal irritation, the diagnosis must be considered. Three case reports are used to illustrate the presentation and diagnosis and treatment of Lyme disease. The characteristics of the disease are reviewed and the limitations of serological testing outlined. The literature has concentrated on bilateral or relapsing facial palsy. A review of palsies in Zurich that presented to the ENT clinic found only unilateral and partial palsies. The diagnosis should be considered in every case of facial palsy of unknown aetiology especially in children.
The present work examines the natural frequencies of vibration of the decoupled human tympanic membrane using the finite element method. A model comprising 49 isoparametric semi-loof thin shell elements was built, based on shape measurements of Kirikae (1960) and our own measurements on several local cadaver ears. A range of material data input was used similar to that assessed earlier by Funnell and Laszlo (1978). The present results indicate the natural vibration mode shapes are simple at low frequencies, but become more complex at higher values as found earlier (Tonndorf and Khanna, 1972; Funnell and Laszlo, 1978), but at reduced frequencies. Data input of the real drum thickenesses and dimensions considerably increases the natural frequencies by about 50% above those for a uniformly thick membrane. It is suggested that realistic eardrum natural frequencies may result from the use of a membrane internal stress parameter in the data file in order to simulate the interplay between radial and circular fibres resulting in the observed drum curvature.
This study presents the results of a 20 year review of maxillary sinus wash-outs performed on children. The results show a decreasing incidence of purulent sinusitis over the study period. Only 17 per cent of antral wash-outs undertaken yielded pus, indicating that surgical practice has failed to adequately take account of the changing disease incidence.
The laryngograph was used to record and compare the voice changes in 11 thyroidectomy patients and 14 controls. The frequency histogram was studied and the change in its spread following surgery used to identify abnormal vocal fold movements due to recurrent laryngeal nerve damage. It also demonstrated changes which occur in thyroidectomy patients and not in patients having other operations. The possible causes include external laryngeal nerve damage.
Patients presenting with sharp pain in their throat after eating fish were studied to determine the site and frequency of impacted fish bones. In 79% no fish bone was demonstrated despite careful follow up. In those proven to have a fish bone 93% were in the oropharynx. The role of X-rays and the indications for referral for endoscopy are discussed.
This paper applies the technique of finite element analysis to the tympanic membrane. A two-dimensional cross-sectional model of the tympanic membrane and malleus is described. A variety of experiments have been performed on this model, and the displacements under a uniform load are analysed. The shape of the displaced membrane and the movement of the umbo were found to be sensitive to a number of factors. These include the elastic modulus of the membrane, the presence and position of the axis or rotation of the malleus, and the size of the pars flaccida. Some implications of these results are discussed.
The long-term natural history of secretory otitis media and the changes induced in the middle ear following grommet insertion are of importance. We report the results 15 years following the unilateral insertion of a Shepard grommet and adenoidectomy for bilateral secretory otitis media. The results suggest that grommets do not protect against attic disease of late onset and induce atrophic scars which do not resolve. Grommets confer no long-term advantages to the hearing when used in the management of childhood secretory otitis media.
This paper deals with grommet induced tympanosclerosis. In the first part, patients from a controlled trial of the treatment of bilateral glue ear using unilateral grommet insertion are reviewed 15 years later. Tympanosclerosis due to grommet insertion is summated using computer graphics. Two areas of maximal tympanosclerosis are found, anteriorly and posteriorly midway between the annulus and the umbo. These maximal areas join inferiorly in the classical horse shoe shape. In an attempt to identify reasons for this distribution, the structure of the lamina propria is reviewed, and the changes that occur in tympanosclerosis considered. With this in mind, the tympanic membrane is modelled using finite element methodology to determine the areas of maximal shear stresses. These are found to be in the same position as tympanosclerosis. Such stresses would be increased by the weight of a grommet in situ. These stresses will damage the fibrils interconnecting between the fibrous layers of the lamina propria and this may lead to tympanosclerosis. This raises the question of whether a lighter grommet would decrease the incidence of grommet-induced tympanosclerosis.
This paper reports a multicentre, controlled, blind, prospective, randomized study into the use of prophylactic systemic antibiotics in myringoplasty surgery. A total of 130 individuals were randomly allocated to either an antibiotic or a non-antibiotic group. Each individual was clinically and audiometrically assessed preoperatively, and 8 weeks postoperatively. It was found that systemic prophylactic antibiotics did not influence either the success rate of myringoplasty surgery or the audiometric result.
In recent years endotracheal tubes with low pressure cuffs have become available with the aim of reducing trauma to the trachea and larynx. This paper uses laryngographic methods to analyse intubation trauma in 20 short to medium term intubations. No difference in laryngeal trauma was found between low pressure, large diameter cuffs when compared to standard cuffs.
The frequency histograms of six patients' laryngographs were studied pre- and post-endotracheal intubation. The changes were correlated with the length of intubation. The post-operative hoarse voice was seen as an increase in the spread of the lower frequencies, and an increase in the fundamental frequency. The latter change was thought to be a subconscious compensation for the hoarseness. The increased lower frequency spread as measured by standard deviation was directly proportional to the length of intubation.
This paper reports a multicentre, controlled, blind, prospective, randomized study into the use of prophylactic systemic antibiotics in myringoplasty surgery. Seventy-one individuals were clinically and bacteriologically assessed both preoperatively, and for a period of 8 weeks postoperatively. The results showed that antibiotic prophylaxis did not eradicate bacterial pathogens already present in preoperative ears, nor did it prevent their development during the postoperative period. The observation that an ear was wet or dry gave no indication of the actual presence or absence of pathogenic organisms.
The role of radiographs in the management of nasal fractures is assessed. The injury is common and the total cost of radiographs significant. A retrospective study concluded that radiographs were not definitive in the management of nasal fractures. This prompted a prospective study, in which 54 patients were assessed clinically, radiologically and under anaesthesia. At each stage they were grouped into treatment and pathological categories and the contribution of each type of assessment studied. Radiographs were not found to be useful in the routine management of nasal fractures.