Electrocautery-induced molten metal particle generation from total joint replacements: Morphology and chemistry.

Electrosurgical techniques are used during surgery to cauterize, and their damaging effects have primarily been documented in terms of tissue necrosis, charring, and localized heat accumulation. Metallic implants as well as the surgical blade can experience incidental electrosurgical current arcing that results in the generation and transfer of melted metallic particles. This work examines the composition, particle size distribution, and chemical state of the melted alloy surfaces and particles produced in vitro. Using scanning electron microscopy and energy dispersive spectroscopy, a flash-melting particle generation phenomenon between source 304 SSL blades and polished cobalt-chromium-molybdenum (CoCrMo) and titanium-6-aluminum-4-vandaium (Ti6Al4V) surfaces was documented where 304 SSL mixed heterogeneously with the CoCrMo and Ti6Al4V ejecting "splatter" particles from the cautery site. The spherical micron-sized particles were embedded with sub-micron-sized particles with 42% of the total sample population measuring between 0.25 and 0.35 µm in diameter. CoCrMo-304 SSL particles were principally made of high concentrations of iron, oxygen, and nickel with embedded sub-micron-sized particles containing oxygen, chromium, and cobalt with lower concentrations of iron and molybdenum. Ti6Al4V-304 SSL interactions resulted in similar micron-sized particles made up of high concentrations of iron, nickel, and chromium with embedded sub-micron-sized particles containing titanium, oxygen, and small amounts of aluminum. X-ray photoelectron spectroscopy of damaged CoCrMo surfaces confirmed the presence of chromium (VI) following dry electrocautery contact in coagulation mode. The structural effects of electrocautery-induced damage are becoming visible in retrieval analysis, but the long-term physiological implications during the lifetime of the implant from this damage mode have yet to be defined.

Synthetic periprosthetic synovial fluid development for in vitro cell-tribocorrosion testing using the Taguchi array approach.

Synovial fluid is dynamic in vivo with biological components changing in ratio and size depending on the health of the joint space, making it difficult to model in vitro. Previous efforts to develop synthetic synovial fluid have typically focused on single organic-tribological interactions with implant surfaces, thus ignoring interplay between multiple solution components. Using a Taguchi orthogonal array, we were able to isolate the individual effects of five independent synovial fluid composition variables: ratios of (1) hyaluronic acid to phospholipids (HA:PL) and (2) albumin to globulin (A:G), and concentrations of (3) hydrogen peroxide (H2 O2 ), (4) cobalt (Co2+ ) and (5) chromium (Cr3+ ) ions on macrophage viability and reduced glutathione production, local solution pH and the comprehensive CoCrMo alloy electrochemical response. While no single synovial fluid variable significantly affected the collective response, HA:PL ratio resulted in the largest impact factor (Δ) on 12 of the 13 measured responses with significant effects (p < .05) on the average macrophage survival rate and electrochemical capacitive state of the CoCrMo surface. Cluster analysis separated significant responses from all trials into three groups, corresponding to healthy, mild, or severely inflamed fluids, respectively; with the healthy synovial fluid composition having mid-range HA:PL ratios with no Co2+ ions, and the severely inflamed fluids consisting of low and high HA:PL ratios with H2 O2 and Co2+ ions. By utilizing the Taguchi approach in combination with cluster analysis, we were able to advance our knowledge of complex multivariate synthetic synovial fluids influence on macrophage and electrochemical behavior at the cell-solution-metal interface.

Sensing Localized Surface Corrosion Damage of CoCrMo Alloys and Modular Tapers of Total Hip Retrievals Using Nearfield Electrochemical Impedance Spectroscopy.

Wear and corrosion damage of biomedical alloys alters the structure and electrochemical properties of the surface heterogeneously. It was hypothesized that local regions on the same surface systematically differ from one another in terms of their impedance characteristics. To test this hypothesis, CoCrMo disks exposed to electrosurgical and inflammatory-species-driven damage were characterized using a localized impedance technique, nearfield electrochemical impedance spectroscopy (NEIS), to assess point-specific surface integrity in response to applied damage. It was found that electrosurgical damage, as may arise during primary arthroplasty and revision surgeries, and hydrogen peroxide concentrations of 5-10 mM significantly alter the corrosion susceptibility of the local surface compared to the as-polished CoCrMo surface. A CoCrMo retrieved neck taper (Goldberg score of 4) was scored in different local regions on the basis of visual appearance, and it was found that there is a direct relationship between increasing debris coverage and decreasing impedance, with the global surface impedance closest to the most severely scored local region. This noninvasive method, which uses a millielectrode configuration to test localized regions, can measure the heterogeneous electrochemical impedance of an implant surface and be tailored to assess specific damage and corrosion mechanisms revealed on retrieval surfaces.

A fluorescent approach for detecting and measuring reduction reaction byproducts near cathodically-biased metallic surfaces: Reactive oxygen species production and quantification.

During tribocorrosion of biomedical alloys, potentials may shift cathodically across the metal-oxide-electrolyte interface resulting in the increased reduction of local oxygen and water molecules. The products of reduction are thought to include reactive oxygen species (ROS) as well as hydroxide ions. Using fluorescent probes, developed for labeling intracellular ROS-based hydroxyl radicals (OH·) and hydrogen peroxide (H2O2), ROS generation due to reduction reactions at cathodically biased CoCrMo alloy surfaces was measured directly. Using terephthalic acid (TA) and pentafluorosulfonylbenzene-fluorescein (PFF) as fluorescent dosimeters, it was found that OH· and H2O2 concentrations increased up to 16 h and 2 h, respectively. Decreases in fluorescence past these time points were attributed to the continuous onset of reduction reactions consuming both the ROS and/or dosimeter. It was also found that voltages below and including -600 mV (vs. Ag/AgCl) produced measurable quantities of H2O2 after two hours of polarization, with concentrations increasing with decreasing potentials up to -1000 mV. The detection and quantification of ROS in a clinical setting could help us better understand the role of ROS in the inflammatory response as well as their impact on corrosion behavior of biomedical alloys.

Enhancing mechanical properties of an injectable two-solution acrylic bone cement using a difunctional crosslinker.

Two-solution bone cements modified with ethylene glycol-dimethacrylate (EG-DMA) as a crosslinker have been developed as an attempt to further improve the mechanical properties of acrylic bone cement. The result of this study shows that EG-DMA can increase the mechanical properties and fractional monomer conversion while preserving the thermal characteristics. The strength and bending modulus increase with EG-DMA concentrations at 5-10 vol % EG-DMA. Substituting the EG-DMA content past 10 vol % decreases the bending properties due to the effects of reduced monomer concentrations. Strengthened EG-DMA samples demonstrated an increase in ductility with noticeably different fracture surface morphologies than the control samples, indicated by microtroughs and ridge formation caused by excessive plastic strain. This work provides insight into the effect of substituting a crosslinker for MMA monomer in an injectable two-solution system and lays out the ideal concentrations of EG-DMA for superior mechanical or fractional monomer conversion properties. © 2018 Wiley Periodicals, Inc. J. Biomed. Mater. Res. Part B, 2018. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 783-790, 2019.

Electrochemical potential zone of viability on CoCrMo surfaces is affected by cell type: Macrophages under cathodic bias are more resistant to killing.

Electrochemical interactions at the cell-metal interface determine cell viability and influence behavior in response to different electrode potential conditions, specifically cathodic biases. Mechanically assisted crevice corrosion, for example, induces cathodic potentials and the associated electrochemical consequences of increased reduction reactions at the implant surface may affect cell viability in a manner that is different for various cell phenotypes. Monocyte macrophage-like U937 cells were cultured on cobalt-chromium-molybdenum (CoCrMo) metal surfaces in vitro for 24 h to assess cell behavior in response to sustained applied voltages. The electrochemical zone of viability for U937 cells polarized for 24 h in vitro was -1000 ≤ mV < +500, compared to -400 < mV < +500 for MC3T3-E1 preosteoblast-like cells cultured under the same conditions, likely as a result of intrinsic apoptosis. Voltages above +250 mV had a lethal effect on U937 cells that was similar to that seen previously for MC3T3-E1 cells on biased CoCrMo surfaces. It appears that cell phenotype directly influences behavior in response to cathodic electrochemical stimuli and that the monocyte macrophage-like cells are more resistant to cathodic potential stimuli than preosteoblasts. This may be due to a glutathione-based increased ability to quench reactive oxygen species and inflammatory-associated radicals hypothesized to be generated during reduction of oxygen. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 526-534, 2019.

Prospective Study on Salivary Evening Melatonin and Sleep before and after Pinealectomy in Humans.

Melatonin is secreted systemically from the pineal gland maximally at night but is also produced locally in many tissues. Its chronobiological function is mainly exerted by pineal melatonin. It is a feedback regulator of the main circadian pacemaker in the hypothalamic suprachiasmatic nuclei and of many peripheral oscillators. Although exogenous melatonin is approved for circadian rhythm sleep disorders and old-age insomnia, research on endogenous melatonin in humans is hindered by the great interindividual variability of its amount and circadian rhythm. Single case studies on pinealectomized patients report on disrupted but also hypersomnic sleep. This is the first systematic prospective report on sleep with respect to pinealectomy due to pinealocytoma World Health Organization grade I without chemo- or radiotherapy. Before and after pinealectomy, 8 patients completed questionnaires on sleep quality and circadian rhythm (Pittsburgh Sleep Quality Index, Epworth Sleepiness Scale, and Morningness-Eveningness Questionnaire), 2 nights of polysomnography, salivary evening melatonin profiles, and qualitative assessment of 2 weeks of actigraphy and sleep logs. Six patients were assessed retrospectively up to 4 years after pinealectomy. Before pinealectomy, all but 1 patient showed an evening melatonin rise typical for indifferent chronotypes. After pinealectomy, evening saliva melatonin was markedly diminished, mostly below the detection limit of the assay (0.09 pg/mL). No systematic change in subjective sleep quality or standard measures of polysomnography was found. Mean pre- and postoperative sleep efficiency was 94% and 95%, and mean sleep-onset latency was 21 and 17 min, respectively. Sleep-wake rhythm during normal daily life did not change. Retrospective patients had a reduced sleep efficiency (90%) and more stage changes, although this was not significantly different from prospective patients. In conclusion, melatonin does seem to have a modulatory, not a regulatory, effect on standard measures of sleep. Study output is limited by small sample size and because only evening melatonin profiles were assessed.

Sleep disturbance after pinealectomy in patients with pineocytoma WHO°I.

BACKGROUND: Because the pineal gland produces melatonin, it is suggested to be involved in the regulation of sleep and circadian rhythm, though there is scant proof of this. Tumors of the pineal gland are rare and various in terms of histological and biological malignancy. We evaluated the occurrence of subjective sleep disturbances in nine patients who underwent a pinealectomy due to pineocytoma WHO°I without additional therapy. METHODS: Patients with intracranial low-grade lesions and patients without a craniotomy who underwent a microscopic lumbar discectomy were matched to our study group by gender, age, and date of surgery. We used standardized sleep questionnaires on sleepiness during the daytime, sleep disturbances, and general pathologic sleep patterns. RESULTS: Patients who underwent a craniotomy either without a pinealectomy (7.2 ± 2.0 points) or with a pinealectomy experienced increased sleep disturbances (6.6 ± 1.3 points) compared to patients who had a lumbar discectomy (2.8 ± 0.4 points), according to the Pittsburgh Sleep Quality Index (PSQI) (p < 0.05). Moreover, sleep disturbances as measured by the insomnia severity index (ISI) were most pronounced in patients who underwent a craniotomy without a pinealectomy (10.4 ± 3.1 points) compared to patients who underwent a pinealectomy or discectomy (5.9 ± 1.9 and 3.3 ± 1.3 points). CONCLUSIONS: Pinealectomy itself did not cause specific sleep impairment, but craniotomy in general did. This interesting and clinically relevant finding needs further investigation.

Antidepressants for the treatment of insomnia : a suitable approach?

The popularity of antidepressants in the treatment of insomnia is not supported by a large amount of convincing data, but rather by opinions and beliefs of the prescribing physicians on the advantages of these agents compared with drugs acting on the benzodiazepine receptor or other drugs used for the treatment of insomnia. The existing data do not allow for clear-cut, evidence-based recommendations concerning the use of antidepressants in insomnia. Our conclusions result from a few short-term studies on single agents, clinical experience and inferences from knowledge on the effect of antidepressants in other indications. At present, prescribing antidepressants for short-term treatment of insomnia can be useful if there is some amount of concomitant depressive symptomology or a history of depression, raising the impression that the present insomnia may be a prodromal sign for a new depressive episode. In all other cases, benzodiazepine receptor agonists, especially the nonbenzodiazepines among them (the so-called 'z drugs') should be the drugs of choice. For long-term treatment, antidepressants are among the pharmacological options, in addition to other groups of psychotropics. Off-label use of antidepressants may be considered for chronic insomnia if there is a concomitant depressive symptomalogy (which is not so pronounced that an antidepressant treatment with adequate higher doses would be required) and if there is no specific indication for one of the other groups of psychotropics (e.g. dementia-related nocturnal agitation, in which case an antipsychotic would be preferred, or circadian problems, in which case melatonin or a melatonin agonist would be favoured). If antidepressants are used to treat insomnia, sedating ones should be preferred over activating agents such as serotonin reuptake inhibitors. In general, drugs lacking strong cholinergic activity should be preferred. Drugs blocking serotonin 5-HT2A or 5-HT2C receptors should be preferred over those whose sedative property is caused by histamine receptor blockade only. The dose should be as low as possible (e.g. as an initial dose: doxepin 25 mg, mirtazapine 15 mg, trazodone 50 mg, trimipramine 25 mg). Regarding the lack of substantial data allowing for evidence-based recommendations, we are facing a clear need for well designed, long-term, comparative studies to further define the role of antidepressants versus other agents in the management of insomnia.

Nefazodone in primary insomnia: an open pilot study.

The present study is the first to investigate the effect of the antidepressant nefazodone on sleep in patients with primary (psychophysiological) insomnia. Following baseline assessment of sleep (polysomnography and subjective sleep parameters), 32 patients received initially 100 mg nefazodone in a single dose at bedtime; according to efficacy and tolerability, the dose could be increased up to 400 mg. Polysomnography and assessment of subjective sleep parameters were repeated after 4 weeks' administration. 12 patients dropped out, 11 of them due to lack of efficiency or intolerable side effects. In 20 patients who completed, the authors observed a lengthened sleep onset latency, decreases in stage 1 and slow wave sleep, and increases in stages 2 and REM under nefazodone. Subjective measures of sleep mirrored a clearer improvement: there was a significant reduction of the PSQI total score and all subscores except sleep latency. We suppose that the dose range chosen was too high for this patient population, thus accounting for the high proportion of dropouts and the partly unfavorable effects on objective sleep parameters. For a definite evaluation of the possible role of nefazodone in the treatment of primary (psychophysiological) insomnia, double-blind, placebo-controlled, randomized studies with lower doses are needed.