Intramedullary nailing versus plate compound osteosynthesis in subtrochanteric and diaphyseal pathologic femoral fractures: a retrospective cohort study.

PURPOSE: Pathologic fractures of the extremities due to carcinoma metastases require individual and patient prognosis-related stabilization procedures. Quick remobilization of the patient to restore the quality of life is of high importance, especially in the case of subtrochanteric and diaphyseal femoral fractures. In our retrospective cohort study, we evaluated intraoperative blood loss, length of operation, complication rate, and regain of lower extremity function in plate compound osteosynthesis (PCO) versus intramedullary nailing (IM) for subtrochanteric and diaphyseal pathologic fractures of the femur. METHODS: Between January 2010 and July 2021, we retrospectively reviewed 49 patients who were treated at our institution for pathologic fractures of the subtrochanteric and diaphyseal femurs for group differences in terms of blood loss, length of operation, implant survival, and Musculoskeletal Tumor Society (MSTS) score. RESULTS: We included 49 stabilization procedures of the lower extremity due to pathologic fractures of the proximal or diaphyseal femur, with a mean follow-up of 17.7 months. IM (n = 29) had a significantly shorter operation time than PCO (n = 20) (112.4 ± 9.4 and 163.3 ± 15.96 min, respectively). We did not detect any significant differences in terms of blood loss, complication rate, implant survival, or MSTS score. CONCLUSION: Based on our data, pathologic subtrochanteric and diaphyseal fractures of the femur can be stabilized with IM, which has a shorter operation time than PCO, but the complication rate, implant survival, and blood loss remain unaffected.

Intramedullary Nailing Versus Compound Plate Osteosynthesis in Pathologic Diaphyseal Humerus Fractures: A Retrospective Cohort Study.

BACKGROUND AND OBJECTIVES: Pathologic fractures of the extremities due to carcinoma metastases require individual and patient prognosis-related stabilization procedures. Considering the anatomic features of the humerus, implant material stability is less critical than femoral fractures because of less weight-bearing stress. Therefore, operation length, blood loss, and quick recovery of function are of greater interest. In this retrospective cohort study, we evaluated and compared the outcomes of compound plate osteosynthesis and intramedullary (IM) nailing while managing diaphyseal pathologic fractures of the humerus. METHODS: We retrospectively reviewed patients treated at our institution for pathologic fractures of the diaphyseal humerus between 2010 and 2021 for group differences (plate osteosynthesis vs. IM nailing) in terms of blood loss, length of operation, implant survival, and upper extremity function. RESULTS: We reviewed 42 stabilization procedures due to pathologic diaphyseal humerus fractures, with a mean follow-up of 8.5±15.4  months. IM nailing (n=20) showed a significantly lower blood loss (266.7±23.7 mL) than plate osteosynthesis (n=22, 571.1±92.6 mL). We did not detect statistically significant differences in the complication rate, length of operation, or Musculoskeletal Tumor Society score. CONCLUSION: Our findings suggested that diaphyseal fractures of the humerus should be stabilized using an IM nail rather than plate osteosynthesis due to lower blood loss, while complication rate, implant survival, and length of operation remain indifferent.

Alternative in vitro assays to assess the potency of sensory irritants-Is one TRP channel enough?

One important function of the peripheral nervous system is the detection of noxious chemicals in the environment as well as the recognition of tissue damage throughout the body. Transient receptor potential (TRP) ion channels are able to sense a multitude of signaling factors involved in these processes. Via the sensory ganglia these sentinels convey information to the central nervous system, where perceptions of nociception or sensory irritation are generated. From the 28 members of the 6 subfamilies present in mammals, researchers in toxicology paid special attention to TRPA1 and TRPV1 channels. Various xenobiotics (e.g., acrolein, formaldehyde) can open these channels causing sensory irritations and defense mechanisms like sneezing, coughing and lacrimation. Heterologous expression of these two channels and the subsequent investigation of ion fluxes have been proposed as in vitro models for the assessment of sensory irritation. In a series of experiments using acetophenone, isophorone, and 2-ethylhexanol (2-EH) we investigated the effects of these irritants on heterologously expressed TRP channels in comparison to a primary cell culture of trigeminal ganglia neurons of mice. We confirmed acetophenone as a specific TRPA1 agonist that activates the receptor in concentrations >3mM, whereas isophorone specifically activates TRPV1 in concentrations >100µM. 2-EH can activate heterologously expressed TRPA1 concentration-dependently (1 mM-10mM). In Ca2+ imaging we observed 2-EH as an agonist of multiple channels (TRPA1, TRPV1, GPCRs) that activates the trigeminal neurons by application of µM 2-EH concentrations. The convergent results of our experiments further support the specificity of acetophenone and isophorone to activate only one of these investigated TRP channels and a more unspecific activation in the case of 2-EH. However, the results of the two different in vitro systems also showed that both TRPA1 and TRPV1 channel activation is important for the perception of irritants and only the combined and tiered testing might lead to precise estimates describing the potency of a xenobiotic to cause sensory irritation or pain.

The involvement of TRP channels in sensory irritation: a mechanistic approach toward a better understanding of the biological effects of local irritants.

Peripheral nerves innervating the mucosae of the nose, mouth, and throat protect the organism against chemical hazards. Upon their stimulation, characteristic perceptions (e.g., stinging and burning) and various reflexes are triggered (e.g., sneezing and cough). The potency of a chemical to cause sensory irritation can be estimated by a mouse bioassay assessing the concentration-dependent decrease in the respiratory rate (50 % decrease: RD50). The involvement of the N. trigeminus and its sensory neurons in the irritant-induced decrease in respiratory rates are not well understood to date. In calcium imaging experiments, we tested which of eight different irritants (RD50 5-730 ppm) could induce responses in primary mouse trigeminal ganglion neurons. The tested irritants acetophenone, 2-ethylhexanol, hexyl isocyanate, isophorone, and trimethylcyclohexanol stimulated responses in trigeminal neurons. Most of these responses depended on functional TRPA1 or TRPV1 channels. For crotyl alcohol, 3-methyl-1-butanol, and sodium metabisulfite, no activation could be observed. 2-ethylhexanol can activate both TRPA1 and TRPV1, and at low contractions (100 µM) G protein-coupled receptors (GPCRs) seem to be involved. GPCRs might also be involved in the mediation of the responses to trimethylcyclohexanol. By using neurobiological tools, we showed that sensory irritation in vivo could be based on the direct activation of TRP channels but also on yet unknown interactions with GPCRs present in trigeminal neurons. Our results showed that the potency suggested by the RD50 values was not reflected by direct nerve-compound interaction.

Direct action and modulating effect of (+)- and (-)-nicotine on ion channels expressed in trigeminal sensory neurons.

Nicotine sensory perception is generally thought to be mediated by nicotinic acetylcholine (nACh) receptors. However, recent data strongly support the idea that other receptors (e.g., transient receptor potential A1 channel, TRPA1) and other pathways contribute to the detection mechanisms underlying the olfactory and trigeminal cell response to nicotine flavor. This is in accordance with the reported ability of humans to discriminate between (+)- and (-)- nicotine enantiomers. To get a more detailed understanding of the molecular and cellular basis underlying the sensory perception of nicotine, we studied the activity of (+)- and (-)-nicotine on cultured murine trigeminal sensory neurons and on a range of heterologously expressed receptors. The human TRPA1 channel is activated by (-)-nicotine. In this work, we show that (+)-nicotine is also an activator of this channel. Pharmacological experiments using nicotinic acetylcholine receptors and transient receptor potential blockers revealed that trigeminal neurons express one or more unidentified receptors that are sensitive to (+)- and/or (-)-nicotine. Results also indicate that the presence of extracellular calcium ions is required to elicit trigeminal neuron responses to (+)- and (-)-nicotine. Results also show that both (+)-nicotine and (-)-nicotine can block 5-hydroxytryptamine type 3 (5-HT3) receptor-mediated responses in recombinant expression systems and in cultured trigeminal neurons expressing 5-HT3 receptors. Our investigations broaden the spectra of receptors that are targets for nicotine enantiomers and give new insights into the physiological role of nicotine.

Comprehensive RNA-Seq expression analysis of sensory ganglia with a focus on ion channels and GPCRs in Trigeminal ganglia.

The specific functions of sensory systems depend on the tissue-specific expression of genes that code for molecular sensor proteins that are necessary for stimulus detection and membrane signaling. Using the Next Generation Sequencing technique (RNA-Seq), we analyzed the complete transcriptome of the trigeminal ganglia (TG) and dorsal root ganglia (DRG) of adult mice. Focusing on genes with an expression level higher than 1 FPKM (fragments per kilobase of transcript per million mapped reads), we detected the expression of 12984 genes in the TG and 13195 in the DRG. To analyze the specific gene expression patterns of the peripheral neuronal tissues, we compared their gene expression profiles with that of the liver, brain, olfactory epithelium, and skeletal muscle. The transcriptome data of the TG and DRG were scanned for virtually all known G-protein-coupled receptors (GPCRs) as well as for ion channels. The expression profile was ranked with regard to the level and specificity for the TG. In total, we detected 106 non-olfactory GPCRs and 33 ion channels that had not been previously described as expressed in the TG. To validate the RNA-Seq data, in situ hybridization experiments were performed for several of the newly detected transcripts. To identify differences in expression profiles between the sensory ganglia, the RNA-Seq data of the TG and DRG were compared. Among the differentially expressed genes (> 1 FPKM), 65 and 117 were expressed at least 10-fold higher in the TG and DRG, respectively. Our transcriptome analysis allows a comprehensive overview of all ion channels and G protein-coupled receptors that are expressed in trigeminal ganglia and provides additional approaches for the investigation of trigeminal sensing as well as for the physiological and pathophysiological mechanisms of pain.

Trigeminal ganglion neurons of mice show intracellular chloride accumulation and chloride-dependent amplification of capsaicin-induced responses.

Intracellular Cl(-) concentrations ([Cl(-)](i)) of sensory neurons regulate signal transmission and signal amplification. In dorsal root ganglion (DRG) and olfactory sensory neurons (OSNs), Cl(-) is accumulated by the Na(+)-K(+)-2Cl(-) cotransporter 1 (NKCC1), resulting in a [Cl(-)](i) above electrochemical equilibrium and a depolarizing Cl(-) efflux upon Cl(-) channel opening. Here, we investigate the [Cl(-)](i) and function of Cl(-) in primary sensory neurons of trigeminal ganglia (TG) of wild type (WT) and NKCC1(-/-) mice using pharmacological and imaging approaches, patch-clamping, as well as behavioral testing. The [Cl(-)](i) of WT TG neurons indicated active NKCC1-dependent Cl(-) accumulation. Gamma-aminobutyric acid (GABA)(A) receptor activation induced a reduction of [Cl(-)](i) as well as Ca(2+) transients in a corresponding fraction of TG neurons. Ca(2+) transients were sensitive to inhibition of NKCC1 and voltage-gated Ca(2+) channels (VGCCs). Ca(2+) responses induced by capsaicin, a prototypical stimulus of transient receptor potential vanilloid subfamily member-1 (TRPV1) were diminished in NKCC1(-/-) TG neurons, but elevated under conditions of a lowered [Cl(-)](o) suggesting a Cl(-)-dependent amplification of capsaicin-induced responses. Using next generation sequencing (NGS), we found expression of different Ca(2+)-activated Cl(-) channels (CaCCs) in TGs of mice. Pharmacological inhibition of CaCCs reduced the amplitude of capsaicin-induced responses of TG neurons in Ca(2+) imaging and electrophysiological recordings. In a behavioral paradigm, NKCC1(-/-) mice showed less avoidance of the aversive stimulus capsaicin. In summary, our results strongly argue for a Ca(2+)-activated Cl(-)-dependent signal amplification mechanism in TG neurons that requires intracellular Cl(-) accumulation by NKCC1 and the activation of CaCCs.