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Biomedical subjects

M M Maassen

Publications and source records attributed to M M Maassen.

At least 19 recordsLinked to original sources
PubMed2006

[Laser-based quality assurance for robot-assisted milling at the base of the skull].

BACKGROUND: Implanting active hearing devices in the lateral base of the skull requires high-precision, secure fixation of the electromagnetic transducer and long-life anchorage using osteosynthetic fixation plates referred to as mountain brackets. Nonlinear distortion in the acoustic signal path and consecutive implant loosening can only be avoided by exact osseous milling to create the necessary cavity bed while avoiding excessive milling. Robot technology is ideal for high-precision milling. However, safety measures are necessary in order to prevent errors from occurring during the reduction process. Ideally, a robot should be guided by a navigation system. However, robotic systems so far available do not yet have an integrated global navigation system. MATERIALS AND METHODS: We used an animal model under laboratory conditions to examine the extent to which the semiautomatic ROBIN assistant system developed could be expected to increase osseous milling accuracy before implanting active electronic hearing devices into the recipient tissue in the cranium. An existing prototype system for robot-assisted skull base surgery was equipped with laser sensors for geometric measurement of the operation site. The three-dimensional measurement data was compared with CT simulation data before, during, and after the robot-assisted operation. The experiments were conducted on test objects as well as on animal models. RESULTS: Under ideal conditions, the operation site could be measured at a spatial resolution of better than 0.02 mm in each dimension. However, reflections and impurities in the operation site from bleeding and rinsing fluids did have a considerable effect on data collection, necessitating specialised registering procedures. Using an error-tolerant procedure specifically developed, the effective registering error could be kept under 0.3 mm. After milling, the resulting shape matched the intended form at an accuracy level of 0.8 mm. CONCLUSION: The results show that robot systems can reach the accuracy required for reliable microsurgery on the cranial base. High-resolution laser-based geometric measurement of the operation site enables head registration without additional artificial landmarks. During the navigated operation, the procedure can be used to ensure that the resulting cavity matches the intended shape as determined in the preoperative planning phase. This will enable quantitative analysis of, and improvement in the quality of robot-assisted surgery in the future.

Animals↗
PubMed2006

[Quality of life in patients with oropharyngeal carcinoma. Gender influences the subjective evaluation].

BACKGROUND: The purpose of this study was to evaluate the impact of patient characteristics and surgical interventions on quality of life (QoL) after primary surgery and postoperative irradiation in patients with oropharyngeal carcinoma. PATIENTS AND METHODS: Between January 1997 and February 2002, 169 patients with carcinoma of the oropharynx were treated with curative intent. In September 2002, a total of 88 disease-free survivors were identified and included in this study. A retrospective chart review was performed and patient responses to the SF-36 Health Survey, EORTC QLQ-C30 and EORTC QLQ-H&N35 questionnaires were evaluated. The questionnaires were completed by 34 patients (39% response rate). RESULTS: All patients were treated with primary surgery followed by postoperative irradiation. The median follow-up was 2.3 years (range 0.5-4.9 years). Using Bonferroni-Holm adjustment for alpha, gender was found to be an important factor in QoL. Females scored significantly worse than males in all three questionnaires. We could not identify other factors influencing QoL. CONCLUSION: The impact of gender on QoL must be considered as very significant.

Adult↗
PubMed2006

[Variable length titanium prostheses for type III tympanoplasty. Intraoperative length adjustment and fixation of the cartilage overlay].

INTRODUCTION: For type III tympanoplasty by partial ossicular replacement prosthesis (PORP) or total ossicular replacement prosthesis (TORP), the length of the prosthesis must match the individual intraoperative anatomical and physiological characteristics. MATERIALS AND METHODS: Databanks were used to determine the necessary sizer length of the sizer disc. The measurement template for the size of the cartilage to overlay the prosthesis headplate was derived from the headplates of the Tübinger titanium prostheses (TTP) and the Dresdener titanium prostheses. Finally all functions were integrated into a synthetic plate. RESULTS: The result was a simple and reasonably priced disposable multifunctional instrument (Tübinger sizer disc TSD) which allowed an exact measurement for every prosthesis in TORP and PORP. For the TTP-Variac, the TSD enabled the simple intraoperative production of prostheses with the length desired by the surgeon. For PORP the TSD enabled an adaptation of the diameter of the prosthesis foot for TTP, TTP-Vario and TTP-Variac and provided a template for the size determination of the cartilage overlay of the titanium prosthesis head. The sizers and the resulting prostheses were used for initial tympanoplastic operations. Audiometric investigations carried out 6 weeks postoperatively gave results corresponding to those previously obtained in a study with TTP and TTP-Vario using the old instrumentation. CONCLUSIONS: The new instrumentation leads to an improvement of the intraoperative practicability and a simplification. The audiological results remain the same.

Disposable Equipment↗
PubMed2004

[Waardenburg syndrome. A heterogenic disorder with variable penetrance].

BACKGROUND: Waardenburg syndrome (WS) is an autosomal dominant disorder characterised by pigmentary anomalies of the skin, hairs, eyes and various defects of other neural crest derived tissues. It accounts for over 2% of congenital hearing impairment. At least four types are recognized on the basis of clinical and genetic criteria. PATIENTS AND METHODS: Based on a screening of congenitally hearing impaired children, 12 families with WS type II were detected. Of special interest was the phenotype of these families, in particular the reduced penetrance of hearing impairment within the families. RESULTS AND CONCLUSION: In all cases a high variability of the disease phenotype was detected and the penetrance of the clinical traits varied accordingly. Therefore, it is not possible to predict the clinical phenotype even in a single family. Based on these studies, we plan to identify the pathogenetic cause of the disease in order to perform a detailed genotype/phenotype analysis.

Genetic Heterogeneity↗
PubMed2002

[Pharyngeal reconstruction after salvage pharyngolaryngectomy in recurrent tumors].

BACKGROUND: Total pharyngeal reconstruction after salvage pharyngolarynectomy in recurrent tumors after primary surgery or radiation therapy may be performed by ENT surgeons in the oncologic field. PATIENTS: We report on six patients that underwent salvage pharyngolaryngectomy and total pharyngeal reconstruction. METHODS: In three cases pharyngeal reconstruction was performed as a two-stage procedure with deltopectoral flaps. One of these patients died before the completion of reconstruction. In three other patients the reconstruction was performed with a tubed pectoralis major myocutaneous flap including one patient after a failed reconstruction with a jejunum segment. or fistula prevention we applied silicon stents in three patients and self-expanding Nitinol stents in three other patients. RESULTS: Of five successfully reconstructed patients two fed orally, one fed combined orally and via PEG and two fed via PEG. CONCLUSIONS: Summarizing our experiences the use of silicon tubes and nitinol stents has proved its worth. Experiences with a larger number of patients must be collected in the future.

Adult↗
PubMed2002

[Recovery of hearing: results of delayed medical treatment in patients with idiopathic sudden hearing loss].

For the treatment of idiopathic sudden sensorineural hearing loss (ISSNHL), a variety of studies about intravenous drug administration with the beginning of treatment in the early period of less then one week after the onset of hearing loss have been performed. In contrast, very little information is available about the efficacy of intravenous drug therapy for ISSNHL with the beginning of treatment later than four weeks after the onset of hearing loss. In a retrospective chart review we studied the treatment results of 57 patients with ISSNHL with beginning of treatment later than four weeks after the onset of hearing loss with no spontaneous recovery of hearing. Patients received a treatment with intravenous administration of Dextran (concentration 40 g/l with NaCl 0.9%) and Procain-HCl (a derivative of the local anaesthetic lidocaine,400-800 mg in a 500 ml rheologic infusion of Dextran 40). 25% of the patients showed a significant improvement of 10 dB or more in hearing threshold at 1000 Hz measured in bone-conducted pure tone audiometry. In a subjective evaluation 53% of the patients noticed a subjective improvement of their individual hearing thresholds.

Adolescent↗
PubMed2001

Expression of Ca(2+)-activated K(+) channel subunits and splice variants in the rat cochlea.

The recently manifested important role of the Ca(2+)-activated K(+) channels, especially of the Slo gene-coded channels, for the cochlea function of the chicken raised the question of homolog expression in mammalian inner ear tissue. Molecular biological methods were used to demonstrate the expression of Ca(2+)-activated K(+) channel subunits and splice variants of the Slo gene in the rat organ of Corti. RT-PCR experiments for the detection of rat Slo alpha subunit mRNA revealed the presence of several already known splice variants including variants which appeared to be typical for the organ of Corti (+58 aa) and for the brain (+61 aa). To detect the accessory beta subunit we used Southern blot hybridization. Our data support the hypothesis that Ca(2+)-activated K(+) channel subunits (i.e. Slo variants) are also involved in the hearing of mammals in the organ of Corti.

Amino Acid Sequence↗
PubMed2001

Total implantation of the active hearing implant TICA for middle ear disease: a temporal bone study.

A subpopulation of hearing-impaired patients has conductive hearing loss that cannot be improved by classic tympanoplasty. Other patients have a mixed hearing loss and cannot be helped by present forms of ear surgery or by hearing aids. Possible help for some patients may come from current implantable hearing devices if these are modified for the patient's specific anatomic situation. The TICA LZ 3001 is a hearing implant for total implantation used to treat moderate to severe sensorineural hearing loss. Most patients who use it have a normal ossicular chain that allows coupling of the implant to the incus. The present temporal bone study demonstrates that the TICA can also be used in patients with an interrupted ossicular chain. If the incus long process shows a defect, the TICA may be coupled to the incus body, and connection between the stapes and the long process of the incus can be achieved with a commercially available titanium-angle prosthesis or liquid ionomeric cement. In cases of an absent incus, the coupling axis of the transducer may be coupled to the stapes head via a modified coupling element. With an absent stapes, the coupling axis may be coupled directly to the perilymph by a coupling element similar to a gold stapes prosthesis.

Ear, Middle↗
PubMed1998

[Cold deformation elements for attaching an implantable hearing aid transducer to ear ossicles or perilymph].

Development and short-term implantation results of the Tübingen implantable hearing aid (TI = Tübingen implant) have been presented. The TI is designed for patients with sensorineural hearing loss due to a malfunction of the cochlear amplifier. This can be identified by the presence of positive recruitment and the absence of TEOAE (transitory evoked otoacoustic emissions). The Tübingen implant functions in two ways: it allows electronic amplification of the auditory signal and electromechanical signal transduction into a micromechanical vibratory stimulus. There are two paths by which vibratory stimulus reaches the cochlea: (1) directly through a perforation in the stapes foot plate into the perilymph or (2) via the ossicular chain. Made of pure titanium, the casing of the helium-tight welded transducer includes the piezoelectric actuator. An implantable manipulator device is designed for transducer positioning and anchoring in the mastoid cavity. Usually, the transducer probe tip is directly coupled to the body of the incus. This functions without a special coupling device by utilization of an Erbium-YAG laser. Special anatomical situations or the loss of incus and/or stapes suprastructure, however, requires coupling of the vibratory signal to other points of the ossicular chain or to the perilymph. A major problem, however, was an intraoperative, irreversible link between the titanium probe tip and coupling elements. To overcome this problem, the coupling elements were made of gold. A crimp technique was developed, allowing the surgeon to induce cold deformation of the gold. The cold deformation technique (crimp) results in an irreversible coupling between the titanium probe tip and the golden coupling element.

Cochlear Implantation↗
PubMed1998

[Value of Schüller conventional roentgen diagnosis and computerized tomography of the temporal bone in preoperative diagnosis of the Tübingen implantable cochlear amplifier].

Recently, the transducer and microphone of a cochlea amplifier implant (CAI) for the treatment of sensorineural cochlear hearing loss have been developed further for implantation into the mastoid cavity. At present, the University of Tuebingen implantable cochlea amplifier consists of an implantable microphone and an implantable piezoelectric transducer. It has been implanted into the first patients. Successful future application of this new implant depends on the suitable fit of the CAI within a patient's mastoid cavity. Using conventional X-ray and CT scans, we analyzed 50 cadaver specimens of the temporal bone before total mastoidectomy. After total mastoidectomy, the volume of the mastoid cavity was measured using CT scans and water volume determination. Finally, the CAI was implanted into those temporal bones that were large enough to house it. Our results demonstrate that the degree of pneumatization in the conventional Schüller X-ray is already a good parameter for preoperative evaluation.

Cochlear Implantation↗
PubMed1998

[An osseointegrated micromanipulator as anchor for implantable hearing aid transducers. 1: Fitting to the surgical anatomy of the temporal bone and surgical technical properties].

The first electronic implantable hearing aids for patients with hearing loss are coupled to the ossicular chain or perilymph during implantation and are now available. Our new Tübingen implant designed for sensorineural hearing loss (SNHL) is the combination of an implantable microphone and piezotransducer. To avoid hearing losses during implantation, the Tübingen piezotransducer will be (1) fixed to the mastoid cavity and (2) positioned to one of the ossicular target points. This can be done with a micromanipulator which will be implanted together with transducer and microphone in the mastoid cavity. The manipulator weights 0.7 g. With four degrees of freedom, it allows highly secure and safe positioning of the transducer's probe tip to the ossicular chain under close to stereotactic conditions. The main advantages of the present micromanipulator are (1) easy handling during surgery, (2) the transducer's precise positioning to the ossicular target point with sufficient degrees of freedom, and (3) the transducer's stable fixation in the mastoid cavity in the final position. Following integrated safety as the leading principle, ossicular or inner ear injuries caused, e.g., by the patient's head movement or unintentional manual contact by the surgeon, are minimized. The micromanipulator is, as it were, the surgeon's vibration-free "artificial hand". The manipulator's development and its optimization to the mastoid cavity by test implantation in 50 human temporal bones are shown in detail. While coupling the transducer to the body of the incus, transducer, microphone, and micromanipulator can be implanted into 76% of all mastoid cavities without protrusion. In the case of transducers coupling to the long process of the incus, the protrusion-free implantation rate of the above-mentioned three implant modules is 78%.

Bone Plates↗
PubMed1998

[A micromanipulator for intraoperative vibratory hearing assessment with an implantable hearing aid transducer].

First concepts of implantable hearing aids to be coupled to the ossicular chain are available for patients with combined or sensorineural hearing loss (SNHL). To ensure that hearing can be improved intraoperative coupling of a test transducer to the ossicular chain is mandatory for allowing surgical anatomy to be checked and vibratory hearing tests to be performed. To achieve this, the test transducer has to be held and positioned securely in situ for some minutes, avoiding risks for middle or inner ear structures. This is not possible using conventional surgical instruments. Thus, a micromanipulator to hold the test transducer during intraoperative hearing tests was developed. This surgical device allows the surgeon safe, risk-free, and controlled coupling of the test transducer to the ossicular chain with one axial and three rotational degrees of freedom. With the aid of a conventional ear retractor (2x2 prongs), the manipulator is fixed at the patient's ear. In conjunction with a piezoelectric test transducer, the manipulator was used in nine patients during local anesthesia. The test transducer is part of an electronic hearing implant (Tübingen implant) specifically designed for SNHL that may be coupled to a middle ear ossicle or the perilymph of the cochlea. The micromanipulator was easy to handle. It allowed accurate positioning of the test transducer in the ear and the desired coupling of the transducer's probe tip to the ossicular chain during auditory tests. According to the principles of integrated safety, the intraoperative risk of ossicular or inner ear injuries caused, for instance, by the patient's head movement is minimized. The design of the manipulator system is universal, also allowing its use for other electronic hearing implants or minimal invasive surgery after minor modifications.

Ear Ossicles↗