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Biomedical subjects

J Helms

Publications and source records attributed to J Helms.

At least 55 records · Page 3Linked to original sources
PubMed1998

Epidural application of ionomeric cement implants. Experimental and clinical results.

During setting and hardening, the hybrid bone substitute ionomeric cement (Ionocem) achieves a stable and durable bond with the apatite of the adjacent bone without interpository soft tissue. Fluid contact during setting results in the release of aluminium ions which may reach critical levels as high as 3000 micrograms/l. On epidural application it is, therefore, essential to prevent cement constituents from gaining access to the intradural space. After the cement has hardened, the presence of aluminium is demonstrable in the adjacent bone to a maximum depth of 20 microns (EDX microanalysis). In rabbits, epidural placement of freshly mixed cement causes slight thickening of the dura. There is reason to believe that human dura, with a thickness 10 times greater, is impermeable to components of the cement. After epidural application of the freshly mixed cement in the frontobasal and laterobasal regions and at the skull cap and petrous apex, 76 patients in all have been followed for up to 6.5 years. During this period no complications have arisen and functional (and cosmetic) results are promising. The availability of preformed implants (Ionoroc, Ionocast) permitted the peridural placement of minimal quantities of freshly mixed cement. These implants were fixed to localized sites on the adjacent calvarial bone by use of Ionocem. Notwithstanding the stringent manufacturer guidelines, there have been reports in the literature that during the vulnerable stage of setting neurotoxic aluminium ions were released into the dural space with a fatal outcome in two cases. In view of potential intradural complications, such as may occur in case of dural leaks, it was considered that further application of the material adjacent to the dura was no longer warranted. The production of Ionocem was discontinued in May 1995.

Aluminum Silicates↗
PubMed1998

[Postoperative results of stapes revision].

BACKGROUND: In this retrospective study indications, intraoperative findings, reconstruction techniques and postoperative hearing results in revision stapes surgery were evaluated. PATIENTS: Between March 1988 and January 1996, 150 patients underwent stapes revision. Indications for surgery were the presence of conductive hearing loss (132), dizziness (12), sensorineural hearing loss (3), deafness (2), and tinnitus (1). RESULTS: Intraoperative findings were lateral migration of the implant, regrowth of bone in the oval window niche, erosion of incus, cholesteatoma, and others. In most cases a new prosthesis (gold piston) was inserted between incus and vestibulum. In cases with incus erosion, a malleovestibulopexy was performed. Seventy-three percent of patients who underwent revision stapes surgery because of conductive hearing loss showed a hearing improvement of 20 dB or more. All patients who underwent revision stapes surgery because of dizziness reported an improvement of their symptoms postoperatively. CONCLUSIONS: Revision stapes surgery should be approached by experienced surgeons, because the risk of severe sensorineural hearing loss is higher than at the time of primary stapedectomy. Informed consent is mandatory.

Adolescent↗
PubMed1998

[Reliable fixation of cochlear implant electrode mountings in children and adults--initial experiences with a new titanium clip].

BACKGROUND: There is a reported 1% incidence of delayed migration of extrusions of the electrode arrays out of the cochlea. METHODS: A titanium clip to fix the electrode array of the MED EL Combi 40 Cochlear Implant System is described. The clip is designed and shaped in a double U configuration. The clip material allows easy adaption to the individual anatomical situation. The clip is fixed to a bony bridge at the incus bar and fixes the electrode in a plane parallel to the chorda facial angle. It is closed around the electrode similarly to a stapes piston around the incus. Additional tests which examined the possible risk of damaging the electrode carrier and clinical findings are described. RESULTS: The clip was used in 23 cases with a follow-up period up to 1 year. No signs for dislocation of the electrode were found. In one revision case the clip was covered with a thin mucosal layer. The electrode array showed no signs of damage. Intraoperative findings confirmed the experimental tests on the electrode fixation. CONCLUSION: The titanium clip facilitates safe and quick fixation of the electrode array and prevents dislocation. its flexibility and shape minimizes the risk of damage.

Adult↗
PubMed1998

[Long-term outcome after reconstruction of the cranial base with ionomer cement].

BACKGROUND: Congenital, posttraumatic, inflammatory or tumours skull base lesions with CSF leakage require reconstruction to mechanically stabilize the CNS and to securely seal the CSF space. PATIENTS AND METHODS: Ionomeric cement was used from 1988 until 1994 in 44 patients for skull base reconstruction at the Department of Otolaryngology-Head and Neck Surgery, University of Würzburg. Thirty-five patients were reexamined. The longest follow-up time was 8 years. The program for the present follow-up study comprised a general ENT and neurological examination as well as CT scans of the skull base, MRI tomography of the CNS, and the determination of the aluminium plasma concentration. RESULTS: None of the patients reexamined presented with complaints. Neurological examinations and MRI tomography in all patients did not reveal any pathological finding related to ionomeric cement application. Aluminium plasma concentrations in patients who received ionomeric cement implantations were not significantly elevated when compared to controls. General ENT examinations and CT scans in thirty-two patients demonstrated regular postoperative findings. The cement at the anterior skull base was not covered completely by mucosa in three patients. In one these cases, CT scans revealed dislocation of the ionomeric cement so that revision surgery was performed for removal. None of the patients to date presented with a CSF leak. CONCLUSION: Long-term results of the present study show that ionomeric cement is a suitable material for closure of osseous skull base lesions to permanently seal the CSF space. These results, however, can only be obtained when handling and application of the material is adequate. Unfortunately, the production of ionomeric cement has been stopped since 1995 following four cases of aluminium encephalopathy reported in the literature.

Adult↗
PubMed1997

Stapes surgery in osteogenesis imperfecta patients.

Osteogenesis imperfecta (OI), or the Van der Hoeve-de Kleyn syndrome, is a heterogeneous group of connective tissue disorders. The key features in this disease are bone fragility with a tendency to spontaneous fractures and deformations. The classical traid of symptoms involves a conductive and/or sensorineural hearing impairment together with a tendency to spontaneous bone fractures and blue sclerae. Between January 1988 and December 1994, ear surgery was performed on eight ears of six OI patients who presented with mixed hearing loss preoperatively. Pathological changes observed in the middle ear were atrophy and/or fractures of the stapedial crura in combination with thickening and fixation of the stapes footplate. Partial stapedectomy was performed in seven cases and a neo-window was created in the promontory of one patient when an overhanging facial canal obscured visualization of the oval window niche. Pre- and postoperative bone conduction thresholds did not differ in any of the patients. Postoperatively, mean values of the air-bone gap in the main speech frequency range were below 10 dB. Functional results following stapes surgery in patients with otosclerosis during the same time interval (n = 857) did not differ significantly. These data indicate that stapes surgery in OI patients can be performed with the same functional predictability as in otosclerosis patients, even though the underlying etiology is considerably different.

Adult↗
PubMed1997

[Ionomer cement prostheses in reconstructive middle ear surgery].

Animal experiments with microbiologic examinations and studies in cell cultures have shown that ionomer cement is a biocompatible and biostable bone replacement material in the head and neck region. Clinical and functional results of its use in the human middle ear have proven to be satisfactory during a maximal period of 2.5 years observation. The present trial was continued in order to determine the long-term behavior of ionomer cement (Ionos partial and total ossicles) after reconstruction of the ossicular chain. The ossicular chain was reconstructed in 343 cases and included various losses of one or more of the ossicles (i.e., incus, incus and malleus, incus and stapes superstructure, and malleus, incus and stapes superstructure). Follow-up extended over a maximum period of 5.5 years. Patients were examined under a surgical microscope and a pure-tone audiogram was performed at regular intervals. Clinical and audiological results were obtained 3 months postoperatively in all reconstructive procedures performed (partial and total ossicular replacement prostheses). These were mainly stable but revision surgery was necessary in 9% of the cases. In 5% the prosthesis was displaced and in 3% the prosthesis had partially migrated through the eardrum. Complete rejection of the implants was observed in the course of infections in 1% of the cases. Ionomer cement as a bone replacement material was found to have all required criteria for its use in the middle ear (biocompatibility, biostability, stable audiologic results and easy workability). These findings show that ionomer cement can be recommended in all cases of ossicular reconstruction.

Adolescent↗
PubMed1997

Performance of ionomeric cement (Ionocem) in the reconstruction of the posterior meatal wall after curative middle-ear surgery.

The hybrid bone-substitute ionomeric cement is suitable for restoring the original anatomy of the posterior canal wall. During a four-year period the posterior meatal wall was rebuilt with ionomeric cement in 74 patients. The canal wall was totally rebuilt in 38 patients, two-thirds rebuilt in 22 cases, and one-third rebuilt in 14 cases. On the meatal side, the canal wall was covered by a musculo-periosteal (Palva) flap. In the majority of cases, the drum was closed with (cartilage)-perichondrium. Revisions were performed in 27 patients (due partially to cholesteatoma, and/or poor visualization of radical mastoidectomy cavities). The ears were non-infected at the time of operation. Permanent epithelialization of the bone replacement material was achieved in 57 cases, with secondary closure of a cutaneous defect of the meatal wall being required in six cases. The auditory canal wall had to be removed in 17 patients owing to deficient soft-tissue coverage, persistent inflammation, and/or partial adhesive processes with development of cholesteatoma. In terms of surgical technique, utilization of the material over a follow-up period of maximally seven years proved it to be a sophisticated procedure for reconstructing the meatal wall. Despite the finesse of the surgical technique employed, the overall failure rate of 31 per cent was inadmissibly high. Implantation of the material should therefore be restricted to middle ears with permanent ventilation and no trace of infection.

Adult↗