Encephalopathy with seizures after use of aluminium-containing bone cement

Influence of the thermal treatment on the characteristics of porous geopolymers as potential biomaterials

Highly porous sodium geopolymer structures were successfully produced through the chemical direct foaming approach at ambient temperature. The impact of the thermal treatment, as well as the influence of various additions of hydrogen peroxide, as a foaming agent, on the porosity, microstructure and mechanical characteristics of the produced geopolymers was investigated. The evaluation of bioactivity was carried out by assessing the formation of an apatite layer on the samples' surface, using scanning electronic microscopy and inductively coupled plasma spectrometry for the simulated body fluid solution, in which the geopolymer samples were kept up to 28 days. In addition, the biodegradability was estimated through the weight change of the samples and pH-measurements. The results demonstrated that the geopolymer foams, produced using 4.5 vol% H₂O₂ and heat-treated at 500 °C for 1 h, possessed a high open porosity (71 vol %), excellent compressive strength (3.56 ± 0.27 MPa), and suitable chemical stability. The pH value of SBF solutions, in which these geopolymers were immersed for 28 days, remained close to the physiological one. The in vitro study indicated that the developed geopolymer foams possessed bioactivity, as demonstrated by the formation of apatite particles on their surface after immersion in the simulated body fluid solution for 28 days.

Ossiculoplasty with hydroxyapatite bone cement: our reconstruction philosophy

The main objective of this study is to analyze results obtained with hydroxyapatite bone cement (HABC) ossiculoplasties. This is a retrospective study of a case series. This study was conducted in an academic hospital and tertiary referral center. A total of 127 ossiculoplasties using HABC were evaluated. Ears were divided into three groups according to procedure: group 1 involved reinforcement of the incudostapedial joint with cement and reconstruction of an incus long process defect with cement. Group 2 involved partial ossicular reconstruction between the stapes and malleus handle with HABC. Group 3 was divided into two subgroups. Group 3B entailed reconstruction of the stapes with a mobile footplate (Austin-Kartush type B = group 3B) and group 3F with a fixed footplate (Austin-Kartush type F = group 3F) using a K-Helix piston (Grace Medical, Memphis, TN, USA) or a classical titanium piston (Kurz, Fuerth, Germany) glued to the incus remnant or malleus handle with cement. Anatomical and pre- and postoperative audiological results were assessed. The mean follow-up was 26 ± 14 months. Percentages of average postoperative air-bone gap ≤ 20 dB were 95, 82.5, 50 and 83.3%, and for air-bone gap ≤ 1 0 dB, 80, 50.9, 16.6 and 50% for groups 1, 2, 3B and 3F, respectively. No complications related to the cement or extrusion occurred. Hearing outcomes also remained stable over time. In our experience, ossiculoplasty with cement provides good and stable functional results, is safe, cost effective, and easy to use. HABC with or without biocompatible ossicular prostheses allows repair of different types of ossicular defects with preservation of the anatomical and physiological ossicular chain, as well as improved stability. Reconstruction of the incus long process or incudostapedial joint defect with cement is preferred over partial ossicular reconstruction.

Novel adaptations to zinc-silicate glass polyalkenoate cements: the unexpected influences of germanium based glasses on handling characteristics and mechanical properties

Aluminum-free glass polyalkenoate cements (GPC) have been hindered for use as injectable bone cements by their inability to balance handling characteristics with mechanical integrity. Currently, zinc-based, aluminum-free GPCs demonstrate compression strengths in excess of 60MPa, but set in c. 1-2 min. Previous efforts to extend the setting reaction have remained clinically insufficient and are typically accompanied by a significant drop in strength. This work synthesized novel glasses based on a zinc silicate composition with the inclusion of GeO2, ZrO2, and Na2O, and evaluated the setting reaction and mechanical properties of the resultant GPCs. Germanium based GPCs were found to have working times between 5 and 10 min, setting times between 14 and 36 min, and compression strengths in excess of 30 MPa for the first 30 days. The results of this investigation have shown that the inclusion of GeO2, ZrO2, and Na2O into the glass network have produced, for the first time, an aluminum-free GPC that is clinically viable as injectable bone cements with regards to handling characteristics and mechanical properties.

[Principles of cholesteatoma surgery]

As a potentially life-threatening disease, cholesteatoma of the petrous bone generally requires a surgical approach. Surgery aims to produce an ear that is easy to care for and is free of recurrent or residual cholesteatoma. Hearing improvement is of secondary importance. Nevertheless the sound conduction system is generally reconstructed as a single-stage procedure. There are various possible methods of dealing with a cholesteatoma: (i) preserving or reconstructing the posterior meatal wall with an aerated mastoid (closed technique) or obliteration of the mastoid completely or partially after removal of the posterior wall (closed technique); and (ii) leaving the cavity open for inspection (open technique). In our opinion any technique where the mastoid is not open for inspection should be called a closed technique. Both techniques have their specific advantages and disadvantages.

An X-ray micro-fluorescence study to investigate the distribution of Al, Si, P and Ca ions in the surrounding soft tissue after implantation of a calcium phosphate-mullite ceramic composite in a rabbit animal model

Synthetic calcium phosphates, despite their bioactivity, are brittle. Calcium phosphate- mullite composites have been suggested as potential dental and bone replacement materials which exhibit increased toughness. Aluminium, present in mullite, has however been linked to bone demineralisation and neurotoxicity: it is therefore important to characterise the materials fully in order to understand their in vivo behaviour. The present work reports the compositional mapping of the interfacial region of a calcium phosphate--20 wt% mullite biocomposite/soft tissue interface, obtained from the samples implanted into the long bones of healthy rabbits according to standard protocols (ISO-10993) for up to 12 weeks. X-ray micro-fluorescence was used to map simultaneously the distribution of Al, P, Si and Ca across the ceramic-soft tissue interface. A well defined and sharp interface region was present between the ceramic and the surrounding soft tissue for each time period examined. The concentration of Al in the surrounding tissue was found to fall by two orders of magnitude, to the background level, within ~35 μm of the implanted ceramic.

In silico evaluation of stress distribution after vertebral body augmentation with conventional acrylics, composites and glass polyalkenoate cements

There exists clinical evidence of fractures in adjacent vertebrae subsequent to vertebral augmentation procedures, such as vertebroplasty (VP) and kyphoplasty (KP). A potential contributory factor to such fractures may be the excessive mismatch of mechanical properties between contemporary bone cements (i.e. polymethyl methacrylate (PMMA) and bisphenol-a-glycidyl dimethacrylate (BIS-GMA)) and bone. Aluminum-free glass polyalkenoate cements (GPCs) present an interesting alternative to conventional bone cements. GPCs adhere to the philosophy that implant materials should have mechanical characteristics similar to those of the bone, and also offer chemical adhesion and intrinsic bioactivity. However, their influence on the loading patterns of augmented vertebrae (as compared with conventional bone cements) is not available in the literature. The present work investigates how the moduli of PMMA, BIS-GMA and GPC implants affect the stress distribution within a single, augmented vertebra, in both healthy and osteoporotic states. Using a finite element model of the L4 vertebra derived from computed tomography data, with simulated augmentation, it was found that, as cement stiffness increased, stress was redistributed from the cortical and trabecular bone to the cement implant. The GPC implant exhibited the least effect on stress redistribution in both the healthy and osteoporotic models compared to its acrylic counterparts. The significance of this work is that, under simulated physiological loading conditions, aluminum-free GPCs exhibit stress distribution throughout the vertebral body similar to that of the healthy bone. In comparison to conventional augmentation materials, the use of aluminum-free GPCs in VP and KP may help to ameliorate the clinical complication of adjacent vertebral body compression fractures.

Passive and active middle ear implants

Besides eradication of chronic middle ear disease, the reconstruction of the sound conduction apparatus is a major goal of modern ear microsurgery. The material of choice in cases of partial ossicular replacement prosthesis is the autogenous ossicle. In the event of more extensive destruction of the ossicular chain diverse alloplastic materials, e.g. metals, ceramics, plastics or composits are used for total reconstruction. Their specialised role in conducting sound energy within a half-open implant bed sets high demands on the biocompatibility as well as the acoustic-mechanic properties of the prosthesis. Recently, sophisticated titanium middle ear implants allowing individual adaptation to anatomical variations are widely used for this procedure. However, despite modern developments, hearing restoration with passive implants often faces its limitations due to tubal-middle-ear dysfunction. Here, implantable hearing aids, successfully used in cases of sensorineural hearing loss, offer a promising alternative. This article reviews the actual state of affairs of passive and active middle ear implants.

The effect of glass synthesis route on mechanical and physical properties of resultant glass ionomer cements

Glass ionomer cements (GICs) have potential orthopaedic applications. Solgel processing is reported as having advantages over the traditional melt-quench route for synthesizing the glass phase of GICs, including far lower processing temperatures and higher levels of glass purity and homogeneity. This work investigates a novel glass formulation, BT 101 (0.48 SiO(2)-0.36 ZnO-0.12 CaO-0.04 SrO) produced by both the melt-quench and the solgel route. The glass phase was characterised by X-ray diffraction (XRD) to determine whether the material was amorphous and differential thermal analysis (DTA) to measure the glass transition temperature (T (g)). Particle size analysis (PSA) was used to determine the mean particle size and X-ray photoelectron spectroscopy (XPS) was used to investigate the structure and composition of the glass. Both glasses, the melt-quench BT 101 and the solgel BT 101, were mixed with 50 wt% polyacrylic acid (M (w), 80,800) and water to form a GIC and the working time (T (w)) and the setting time (T (s)) of the resultant cements were then determined. The cement based on the solgel glass had a longer T (w) (78 s) as compared to the cement based on the melt derived glass (19 s). T (s) was also much longer for the cement based on the solgel (1,644 s) glass than for the cement based on the melt-derived glass (25 s). The cements based on the melt derived glass produced higher strengths in both compression (sigma(c)) and biaxial flexure (sigma(f)), where the highest strength was found to be 63 MPa in compression, at both 1 and 7 days. The differences in setting and mechanical properties can be associated to structural differences within the glass as determined by XPS which revealed the absence of Ca in the solgel system and a much greater concentration of bridging oxygens (BO) as compared to the melt-derived system.

Comparison of an experimental bone cement with a commercial control, Hydroset

Glass polyalkenoate cements based on strontium calcium zinc silicate glasses (Zn-GPCs) and high molecular weight polyacrylic acids (PAA) (MW; 52,000-210,000) have been shown to exhibit mechanical properties and in vitro bioactivity suitable for arthroplasty applications. Unfortunately, these formulations exhibit working times and setting times which are too short for invasive surgical applications such as bone void filling and fracture fixation. In this study, Zn-GPCs were formulated using a low molecular weight PAA (MW; 12,700) and a modifying agent, trisodium citrate dihydrate (TSC), with the aim of improving the rheological properties of Zn-GPCs. These novel formulations were then compared with commercial self-setting calcium phosphate cement, Hydroset, in terms of compressive strength, biaxial flexural strength and Young's modulus, as well as working time, setting time and injectability. The novel Zn-GPC formulations performed well, with prolonged mechanical strength (39 MPa, compression) greater than both vertebral bone (18.4 MPa) and the commercial control (14 MPa). However, working times (2 min) and rheological properties of Zn-GPCs, though improved, require further modifications prior to their use in minimally invasive surgical techniques.

Partial ossicular reconstruction: comparison of three different prostheses in clinical and experimental studies

OBJECTIVE

To compare the reconstruction results of a long incus process defect using 3 different partial ossicular replacement prostheses (PORP).

STUDY DESIGN

Temporal bone experiments and retrospective case review.

SETTING

Tertiary referral center. EXPERIMENTAL MATERIAL AND PATIENTS: The experimental study was performed on 18 temporal bones; 66 patients with retraction pockets, chronic otitis media with or without cholesteatoma.

INTERVENTIONS

Ossiculoplasty using 3 different PORP: titanium angle prosthesis, autologous incus interposition, and titanium clip prosthesis.

MAIN OUTCOME MEASURES

Laser Doppler vibrometry in temporal bones measured transmission properties of the PORP. Patients were retrospectively assessed up to 5 years after surgery. Audiologic data were analyzed for preoperative and postoperative air conduction and air-bone gap at 0.5, 1, 2, 3, and 4 kHz. Statistical analyses compared the outcome in the experimental and clinical setting.

RESULTS

Experimentally, the titanium PORP showed similar transmission properties because the overall difference to the intact specimen was -4.14 +/- 0.59 dB for the titanium angle prosthesis and -4.61 +/- 0.57 dB for the titanium clip prosthesis. The transmission after an autologous incus interposition was significantly worse (-9.32 +/- 0.39 dB, p < or = 0.001) compared with the other prostheses. Patients' mean postoperative air-bone gap was 25.5 +/- 1.2 dB and less than 20 dB in at least 66% of cases without any significant differences between the groups.

CONCLUSION

In the clinical setting, the confounding factors that influence the acoustic outcome after partial ossiculoplasty obscure the prosthesis-related transmission factors that can otherwise be derived in the experimental setting. The results do not generally favor the use of 1 specific prosthesis, rather they suggest that the correct choice of a prosthesis be based on the anatomic and pathophysiologic conditions found in the individual patient.

Aluminum Toxicity Following IV Use of Oral Methadone Solution

BACKGROUND

Aluminum toxicity has been reported in renal failure patients exposed to aluminum-contaminated dialysate and oral phosphate binders. We report a case of significant aluminum toxicity in a non-hemodialysis patient.

CASE REPORT

A 43-year-old male IV drug user presented to the hospital with a seizure disorder of recent onset, progressive cognitive decline, ataxia, and dysarthria. The serum aluminum concentration was 180 micrograms/L (6.65 micromol/L). For 3 to 4 years prior, the patient had injected 'cooked' oral methadone. The methadone solution was heated in an aluminum pot to reduce the volume and then injected intravenously (IV). He was treated with IV deferoxamine over 9 months until he failed to return. Serum aluminum level after 9 months of treatment was 64.5 microgram/L (2.39 micromol/L). Neurological symptoms were partially improved.

CONCLUSION

Chronic IV injection of oral methadone solution heated in an aluminum-based cooking utensil may result in significant aluminum toxicity.

Bioactive sol-gel glass added ionomer cement for the regeneration of tooth structure

Dental cements including the glass ionomer cement (GIC) have found widespread use in restoring tooth structures. In this study, a sol-gel derived glass (SG) with a bioactive composition (70SiO(2).25CaO.5P(2)O(5)) was added to the commercial GIC (GC, Fuji I) to improve the bioactivity and tooth regeneration capability. The SG powders prepared with sizes in the range of a few micrometers were mixed with GIC at SG/GC ratios of 10 and 30 wt%. The setting time, diametral tensile strength, and in vitro bioactivity of the GC-SG cements were examined. The setting time of the GC-SG cements increased with increasing amount of SG. However, the addition of SG did not significantly alter the diametral tensile strength of the GC. GC-SG induced the precipitation of an apatite bone-mineral phase on the surface after immersion in a simulated body fluid (SBF), showing in vitro bone bioactivity. However, no mineral induction in SBF was observed in the commercial GIC after the immersion. The in vitro cell assay confirmed that the GC-SG samples produced higher cell viability than the GC sample with cell culturing for up to 7 days.

Comparison of an experimental bone cement with surgical Simplex P, Spineplex and Cortoss

Conventional polymethylmethacrylate (PMMA) cements and more recently Bisphenol-a-glycidyl dimethacrylate (BIS-GMA) composite cements are employed in procedures such as vertebroplasty. Unfortunately, such materials have inherent drawbacks including, a high curing exotherm, the incorporation of toxic components in their formulations, and critically, exhibit a modulus mismatch between cement and bone. The literature suggests that aluminium free, zinc based glass polyalkenoate cements (Zn-GPC) may be suitable alternative materials for consideration in such applications as vertebroplasty. This paper, examines one formulation of Zn-GPC and compares its strengths, modulus, and biocompatibility with three commercially available bone cements, Spineplex, Simplex P and Cortoss. The setting times indicate that the current formulation of Zn-GPC sets in a time unsuitable for clinical deployment. However during setting, the peak exotherm was recorded to be 33 degrees C, the lowest of all cements examined, and well below the threshold level for tissue necrosis to occur. The data obtained from mechanical testing shows the Zn-GPC has strengths of 63 MPa in compression and 30 MPa in biaxial flexure. Importantly these strengths remain stable with maturation; similar long term stability was exhibited by both Spineplex and Simplex P. Conversely, the strengths of Cortoss were observed to rapidly diminish with time, a cause for clinical concern. In addition to strengths, the modulus of each material was determined. Only the Zn-GPC exhibited a modulus similar to vertebral trabecular bone, with all commercial materials exhibiting excessively high moduli. Such data indicates that the use of Zn-GPC may reduce adjacent fractures. The final investigation used the well established simulated body fluid (SBF) method to examine the ability of each material to bond with bone. The results indicate that the Zn-GPC is capable of producing a bone like apatite layer at its surface within 24 h which increased in coverage and density up to 7 days. Conversely, Spineplex, and Simplex P exhibit no apatite layer formation, while Cortoss exhibits only minimal formation of an apatite layer after 7 days incubation in SBF. This paper shows that Zn-GPC, with optimised setting times, are suitable candidate materials for further development as bone cements.

Biocompatibility of glass-ionomer bone cements

Glass-ionomer cements (GIC) have been extensively used in dentistry for over 30 years. Due to their excellent biocompatibility in dental applications GIC have been formulated for medical applications. The past decade has seen some impressive advances in the development of medical GICs, however these advances have been matched by serious critical problems. This review examines the properties of GICs, which can influence their behaviour in a biological environment. The progress made and the problems encountered in the development of these bone cements will also be addressed. The review will conclude with the research currently being employed to optimise the biocompatibility of these important biomaterials. There is little doubt that GICs compare favourably with alternative bone cements for specific applications, based on in vitro and in vivo studies. There is however, a degree of risk inherent in the use of any medical device or biomaterial. GICs must therefore be used carefully and in accordance with the instructions that are based on a significant body of research data.

In vitro biocompatibility of a novel Fe2O3 based glass ionomer cement

INTRODUCTION

Since their invention in the late 1960s, glass ionomer cements (GICs) have been used extensively in dentistry but recently they have also been utilised in ear nose and throat (ENT) surgery. Unfortunately, Al3+, a component of conventional ionomer glasses, has been linked to poor bone mineralisation and neurotoxicity.

OBJECTIVE

The aim of the research was to modify a commercial ionomer glass composition by substituting Al2O3 with Fe2O3.

METHODS

Glasses with the following molar compositions were fabricated: 4.5SiO2*3M2O3*XP2O5*3CaO*2CaF2 (M = Al or Fe, X = 0-1.5). The glasses were characterised using X-ray fluorescence (XRF) and X-ray powder diffraction (XRD). Cements were prepared using a standard ratio of; 1 g of glass powder: 0.2 g of dried polyacrylic acid: 0.3 g of 10% tartaric acid solution. Cement formation was assessed using a Gilmore needle and in vitro biocompatibility was investigated for novel cement formulations.

RESULTS

XRF revealed that the Fe2O3-based glasses had Al2O3 contamination from the crucibles and also had undergone substantial F- losses. XRD gave peaks that corresponded to magnetite Fe3O4 (JCPDS # 19-629) in all compositions. Apatite Ca5(PO4)3(OH,F) (JCPDS # 15-876) was identified in P2O5 containing glasses. It was possible to fabricate cements from all of the Fe2O3-based ionomer glasses. Good in vitro biocompatibility was observed for the Fe2O3-based cements.

CONCLUSION

Ionomer glasses may be prepared by entirely replacing Al2O3 with Fe2O3. Cement setting times appeared to be related to P2O5 content. Fe2O3-based cements showed good in vitro biocompatibility.

Novel Fe2O3-Containing Glass Ionomer Cements: Glass Characterisation

Glass-ionomer cements (GIC) have been used in dentistry for over 30 years. In the past ten years they have also been developed for use as medical grade bone cements. However, concerns have been raised over the biocompatibility of GIC’s in non-dental applications. The release of Al3+ ions from the cement has been related to localized poor bone mineralisation and neurotoxicity. There is a need therefore to develop Al2O3-free cements. One potential route is the substitution of Al2O3 with Fe2O3 in the glass. An Fe2O3-based glass for use in GIC‘s was fabricated. The glass was found to differ considerably compared to the traditional amorphous Al2O3-based glasses. XRD demonstrated a highly crystalline morphology containing magnetite and apatite which was confirmed using electron microscopy. It was predicted that the reduction in Al concentration in the glass would improve the biocompatibility of the resulting cement.

Fehlerm�glichkeiten bei der Ossikelkettenrekonstruktion

Today, the reconstruction of the ossicular chain is standard in middle ear surgery. It is performed as a one step procedure in cases of non-inflamed middle ears, as well as in cases of chronic ear diseases. In contrast to the past, a large tympanic cavity is today regularly reconstructed, which contributes to a normally ventilated middle ear. Reconstruction of the ossicular chain is necessary to keep the tympanic membrane in its normal position.However, many modern prostheses are available with different designs and material properties. This article aims to give an overview of the acusto-mechanical and surgical aspects of ossicular chain reconstruction. After a description of normal middle ear vibration, the biomechanical background of the reconstructed middle ear (incus reconstruction, stapes reconstruction) is discussed.

Devitrification of ionomer glass and its effect on the in vitro biocompatibility of glass-ionomer cements

The effects of devitrification of an ionomer glass with a molar composition 4.5SiO(2).3Al(2)O(3).1.5P(2)O(5).3CaO.2CaF(2) on cement formation and in vitro biocompatibility were investigated. Differential thermal analysis was used to study the phase evolution in the glass, and to determine the heat treatments for production of glass-ceramics. X-ray diffraction patterns from glass frit heat-treated at 750 degrees C for 2h contained peaks corresponding to apatite (JCPDS 15-876), whereas for samples heat-treated at 950 degrees C for 2h apatite and mullite (JCPDS 15-776) were the major phases detected. Transmission electron microscopy (TEM) confirmed that apatite and apatite-mullite phases were present after heat treatments at 750 degrees C and 950 degrees C respectively. Glass and glass-ceramics were ground to prepare <45microm powders and glass ionomer cements were produced using a ratio of 1g powder: 0.2g PAA: 0.3g 10% m/v tartaric acid solution in water. In vitro biocompatibility was evaluated using cultured rat osteosarcoma (ROS) cells. Scanning electron microscopy (SEM) showed that cells colonised the surfaces of cements prepared using untreated ionomer glass and glass crystallised to form apatite (750 degrees C/2h). However, quantitative evaluation using MTT and total protein assays indicated that more cell growth occurred in the presence of cements prepared using ionomer glasses crystallised to apatite than cements prepared using untreated glass. The least cell growth and respiratory activity was observed on cements made with crystallised glass containing both apatite and mullite. It was concluded that the controlled devitrification of ionomer glasses could be used to produce GIC bone cements with improved biocompatibility.

Aluminum: impacts and disease

Aluminum is the most widely distributed metal in the environment and is extensively used in modern daily life. Aluminum enters into the body from the environment and from diet and medication. However, there is no known physiological role for aluminum within the body and hence this metal may produce adverse physiological effects. The impact of aluminum on neural tissues is well reported but studies on extraneural tissues are not well summarized. In this review, the impacts of aluminum on humans and its impact on major physiological systems are summarized and discussed. The neuropathologies associated with high brain aluminum levels, including structural, biochemical, and neurobehavioral changes, have been summarized. In addition, the impact of aluminum on the musculoskeletal system, respiratory system, cardiovascular system, hepatobiliary system, endocrine system, urinary system, and reproductive system are discussed.

Subacute fatal aluminum encephalopathy after reconstructive otoneurosurgery: a case report

We report a 52-year-old woman who underwent otoneurosurgery to resect acoustic neurinoma. Bone reconstruction was performed with an aluminium (Al)-containing cement. Six weeks later the patient suffered from loss of consciousness, myoclonic jerks, and persistent grand mal seizures, clinical symptoms that resembled those of lethal dialysis encephalopathy of the 1960s and 1970s. She died 6 months later because of septic complications. Light- and electron-microscopic investigation of the central nervous system (CNS) showed pathognomonic Al-containing intracytoplasmic argyrophilic inclusions in choroid plexus epithelia, neurons, and cortical glia. These changes are characteristics of dialysis-associated encephalopathy (DAE), induced nowadays by long-term ingestion of Al-containing drugs (and with benign clinical courses). Atomic absorption spectrometry showed an increase of mean bulk Al concentration of the cortex and subcortex up to 9.3 microg/g (normal range <2 microg/g); laser microprobe showed the increase of Al in subcellular structures. This unique case again shows the extraordinary neurotoxicity of Al, which was, in our patient, initiated by an amount of about 30 mg Al and apparently caused by direct Al access to the brain parenchyma via a cerebrospinal fluid leakage.

Ultrastructural study of rat hippocampus after chronic administration of aluminum L-glutamate: an acceleration of the aging process

An ultrastructural study of rat hippocampus was performed on young (group 1) and old (group 4) rats receiving daily subcutaneous injections of aluminum L-glutamate and on old untreated rats (group 5). Young controls were treated with sodium L-glutamate (group 2) and physiological saline (group 3). Group 1 showed vacuolated astrocytes with numerous lipofuscin deposits, mitochondrial swelling, a thinning of the myelin sheath, and many multivesicular bodies invading the cytoplasm. Cellular structure did not appear to be affected in groups 2 and 3. Group 4 showed swollen mitochondria, a demyelination process in axonal regions, sizable perivascular oedema with vessel retraction and gliofilament bundles. In this group, lipofuscin deposits in astrocytes were associated with multivesicular bodies that thinned the myelin sheath to the breaking point; however, no excitotoxic glutamate-induced effects were observed. In group 5, extreme cytoplasmic vacuolation was observed, with massive mitochondrial swelling, considerable thinning of the myelin sheath (at times to the breaking point), sizable vacuolar degeneration and gliofilament bundles. These results indicate that ultrastructural alterations in the hippocampus, such as cell vacuolization, massive mitochondrial swelling and the demyelination process, occur with aging and independently of aluminum intoxication. Similar alterations were observed in aluminum L-glutamate-intoxicated young rats, but not in controls. These results are consistent with aluminum-induced acceleration of the aging process.

Facial Nerve Paralysis following Repair of the External Ear Canal with Ionomeric Cement

A 20-year-old man developed a complete facial nerve paralysis following surgical reconstruction of the posterior ear canal with ionomeric cement. The paralysis developed gradually during the second and third postoperative weeks. Six weeks following the complete removal of the cement, the facial nerve recovered completely. The literature contains reports of diffusion of aluminum ions, which can reach toxic levels in tissue fluid and adjacent bone as the cement hardens. This side effect has been reported to cause an inflammatory response in the dura and brain and has led to fatalities. To our knowledge, there has been no other report of an ionomeric cement having a direct toxic effect on peripheral nerve transmission. Because ionomeric cements are used routinely in otosurgery, especially in canal reconstructions where the proximity to the facial nerve is evident, it is important to use caution when introducing ionomeric cements into near-nerve anatomic locations.

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.

Biological levels of aluminium after use of aluminium-containing bone cement in post-otoneurosurgery

Use aluminium-containing biomaterials in otoneurosurgery for reconstitution of bone in contact with cerebrospinal fluid (CSF) also led to cases of encephalopathy and death. We report aluminium (Al) concentrations in the biological fluids of six French patients following use of Al-containing bone cement in otoneurosurgery. In five patients, the mean plasma Al levels (microgram/L) were: 1.20 +/- 0.05 (case 2), 9.20 +/- 0.10 (case 3), 1.00 +/- 0.05 (case 4), 2.80 +/- 0.05 (case 5) and 2.00 +/- 0.05 (case 6). In case 1, Al concentrations were 176 micrograms/L in the postauricular CSF accumulation, 34 micrograms/L in the pontocerebellar angle and 4 and 6 micrograms/L in the lumbar shunt. As a precautionary measure, in the first three cases the biomaterial was removed soon after the intervention, and no increase in plasma or CSF Al was observed. In the other cases, absence of neurobiological symptoms and normal concentrations of Al in plasma led neurosurgeons not to extract this biomaterial. Al assay thus may be considered to be a complementary and at times a decision-generating factor. Care is needed at all stages from sampling through analysis because Al is ubiquitous and factually high results may be clinically misleading. Herein, such considerations are discussed in conjunction with the neurotoxicity of this metal in man. In addition, the authors call for in-depth preliminary trials of these biomaterials in animals prior to introduction on the market.

Bone replacement by ionomer cement in osteoplastic frontal sinus operations

Ionomer-based cement is a new bone replacement material. After promising results in middle ear and skull base surgery, we started to use Ionocap as an alternative to metal osteosynthesis material. Between 1992 and 1995, 20 men and 9 women were treated with an osteoplastic approach for complicated frontal sinus diseases at Johann Wolfgang Goethe University. Ionocap as bonding material for bone was used in 22 of the patients. The indications for osteoplastic surgery were recurrent frontal rhinosinusitis, mucoceles, skull base fractures, osteomas and meningocele. The surgical procedure using bone cement was found to be much easier and shorter, the functional stability achieved was at least equal and the cosmetic outcome was clearly superior when compared to cases done with metal osteosynthesis. No rejection of the material or osteonecrosis was observed. In no case was the cement placed in direct contact to dura mater. Our findings show that ionomer-based cement can be recommened in osteoplastic frontal sinus surgery, but Ionocap should only be used strictly according to the guidelines of the supplier.