Bioresorbable implants vs. Kirschner-wires in the treatment of severely displaced distal paediatric radius and forearm fractures - a retrospective multicentre study.

BACKGROUND: Distal radius fractures are very common in paediatric patients. Severely displaced fractures may require surgical intervention. The gold standard surgical method is percutaneous K-wire osteosynthesis followed by immobilisation. Metal implants can be removed with a second intervention; however, these extra procedures can cause further complications. Several studies confirm the benefits of bioabsorbable implants for paediatric patients. The aim of this retrospective study was to compare the complication rates of displaced distal metaphyseal radius (AO 23r-M/3.1) and forearm (AO 23-M/3.1) fractures in children operated on with K-wires versus a novel technique with bioresorbable implants. METHODS: We retrospectively reviewed 94 patients in three paediatric trauma centres who underwent operations due to severely displaced distal forearm or metaphyseal radial fractures between January 2019 and January 2020. The mean age was 8.23 (ranging from 5-12). 30 patients (bioresorbable group, BR-group) were treated with biodegradable PLGA implants (Bioretec®, ActivaPin®), 40 patients with one or two stainless steel Kirschner-wires (K-wires, Sanatmetal®) which were buried under the skin (KW I-group) and 24 children with K-wires left outside the skin. (KWII. Group). We examined the number of minor and major complications as well as the need for repeated interventions. Follow-up was at least one and half year. RESULTS: There was no significant difference between the complication rates at the two KW groups (p = 0.241; Cramer's V = 0.211), while the complication rate of the BR group was significantly lower. (p = 0.049; Cramer's V = 0.293 and p = 0.002; Cramer's V = 0.418 respectively). No later than half a year after the injury, no difference was observed between the functional outcomes of the patients in each group. One and a half years after the injury, no signs of growth disturbance were found in any of the children. No second surgical intervention was required in the BR group. CONCLUSIONS: Surgeries with bioresorbable intramedullary implants may have fewer complications than K- wire osteosynthesis in the treatment of severely displaced distal forearm fractures. The benefits are most pronounced in the first six weeks after surgery, reducing the number of outpatient visits and increasing the child's sense of comfort. As no second intervention is required, this can lead to significant cost savings. After half a year, there is no difference in the outcomes between the different surgical treatment strategies.

Heritable Differences in Catecholamine Signaling Modulate Susceptibility to Trauma and Response to Methylphenidate Treatment: Relevance for PTSD.

Alterations in cortical catecholamine signaling pathways can modulate acute and enduring responses to trauma. Heritable variation in catecholamine signaling is produced by a common functional polymorphism in the catechol-O-methyltransferase (COMT), with Val carriers exhibiting greater degradation of catecholamines than Met carriers. Furthermore, it has recently been suggested that drugs enhancing cortical catecholamine signaling may be a new therapeutic approach for posttraumatic stress disorder (PTSD) patients. We hypothesized that heritable differences in catecholamine signaling regulate the behavioral response to trauma, and that methylphenidate (MPD), a drug that preferentially blocks catecholamine reuptake in the prefrontal cortex (PFC), exerts COMT-dependent effects on trauma-induced behaviors. We first examined the contribution of the functional mutation COMTval158met to modulate enduring behavioral responses to predator stress in a unique "humanized" COMTval158met mouse line. Animals were exposed to a predator (cat) for 10 min and enduring avoidance behaviors were examined in the open field, light-dark box, and "trauma-reminder" tests 1-2 weeks later. Second, we examined the efficacy of chronic methylphenidate to reverse predator stress effects and if these effects were modulated by COMTval158met genotype. Mice were exposed to predator stress and began treatment with either saline or methylphenidate (3 mg/kg/day) 1 week after stress until the end of the testing [avoidance behaviors, working memory, and social preference (SP)]. In males, predator stress and COMTval158met had an additive effect on enduring anxiety-like behavior, with Val stressed mice showing the strongest avoidance behavior after stress compared to Met carriers. No effect of COMT genotype was observed in females. Therefore methylphenidate effects were investigated only in males. Chronic methylphenidate treatment reversed the stress-induced avoidance behavior and increased social investigation independently of genotype. Methylphenidate effects on working memory, however, were genotype-dependent, decreasing working memory in non-stressed Met carriers, and improving stress-induced working memory deficit in Val carriers. These results suggest that heritable variance in catecholamine signaling modulates the avoidance response to an acute trauma. This work supports recent human findings that methylphenidate might be a therapeutic alternative for PTSD patients and suggests that methylphenidate effects on anxiety (generalized avoidance, social withdrawal) vs. cognitive (working memory) symptoms may be modulated through COMT-independent and dependent mechanisms, respectively.

Structural and functional alterations in the prefrontal cortex after post-weaning social isolation: relationship with species-typical and deviant aggression.

Although the inhibitory control of aggression by the prefrontal cortex (PFC) is the cornerstone of current theories of aggression control, a number of human and laboratory studies showed that the execution of aggression increases PFC activity; moreover, enhanced activation was observed in aggression-related psychopathologies and laboratory models of abnormal aggression. Here, we investigated these apparently contradictory findings in the post-weaning social isolation paradigm (PWSI), an established laboratory model of abnormal aggression. When studied in the resident-intruder test as adults, rats submitted to PWSI showed increased attack counts, increased share of bites directed towards vulnerable body parts of opponents (head, throat, and belly) and reduced social signaling of attacks. These deviations from species-typical behavioral characteristics were associated with a specific reduction in the thickness of the right medial PFC (mPFC), a bilateral decrease in dendritic and glial density, and reduced vascularization on the right-hand side of the mPFC. Thus, the early stressor interfered with mPFC development. Despite these structural deficits, aggressive encounters enhanced the activation of the mPFC in PWSI rats as compared to controls. A voxel-like functional analysis revealed that overactivation was restricted to a circumscribed sub-region, which contributed to the activation of hypothalamic centers involved in the initiation of biting attacks as shown by structural equation modeling. These findings demonstrate that structural alterations and functional hyperactivity can coexist in the mPFC of rats exposed to early stressors, and suggest that the role of the mPFC in aggression control is more complex than suggested by the inhibitory control theory.

Neural mechanisms of predatory aggression in rats-implications for abnormal intraspecific aggression.

Our recent studies showed that brain areas that are activated in a model of escalated aggression overlap with those that promote predatory aggression in cats. This finding raised the interesting possibility that the brain mechanisms that control certain types of abnormal aggression include those involved in predation. However, the mechanisms of predatory aggression are poorly known in rats, a species that is in many respects different from cats. To get more insights into such mechanisms, here we studied the brain activation patterns associated with spontaneous muricide in rats. Subjects not exposed to mice, and those which did not show muricide were used as controls. We found that muricide increased the activation of the central and basolateral amygdala, and lateral hypothalamus as compared to both controls; in addition, a ventral shift in periaqueductal gray activation was observed. Interestingly, these are the brain regions from where predatory aggression can be elicited, or enhanced by electrical stimulation in cats. The analysis of more than 10 other brain regions showed that brain areas that inhibited (or were neutral to) cat predatory aggression were not affected by muricide. Brain activation patterns partly overlapped with those seen earlier in the cockroach hunting model of rat predatory aggression, and were highly similar with those observed in the glucocorticoid dysfunction model of escalated aggression. These findings show that the brain mechanisms underlying predation are evolutionarily conservative, and indirectly support our earlier assumption regarding the involvement of predation-related brain mechanisms in certain forms of escalated social aggression in rats.

The neural background of hyper-emotional aggression induced by post-weaning social isolation.

Post-weaning social isolation in rats is believed to model symptoms of early social neglect-induced externalizing problems including aggression-related problems. We showed earlier that rats reared in social isolation were hyper-aroused during aggressive contacts, delivered substantially more attacks that were poorly signaled and were preferentially aimed at vulnerable body parts of opponents (head, throat and belly). Here we studied the neural background of this type of aggression by assessing the expression of the activation marker c-Fos in 22 brain areas of male Wistar rats submitted to resident-intruder conflicts. Post-weaning social isolation readily produced the behavioral alterations noticed earlier. Social isolation significantly increased the activation of brain areas that are known to directly or indirectly control inter-male aggression. Particularly, the medial and lateral orbitofrontal cortices, anterior cingulate cortex, bed nucleus of the stria terminalis, medial and basolateral amygdala, hypothalamic attack area, hypothalamic paraventricular nucleus and locus coeruleus showed increased activations. This contrasts our earlier findings obtained in rats with experimentally induced hypoarousal, where abnormal attack patterns were associated with over-activated central amygdala, lateral hypothalamus, and ventrolateral periaqueductal gray that are believed to control predatory attacks. We have observed no similar activation patterns in rats socially isolated from weaning. In summary, these findings suggest that despite some phenotypic similarities, the neuronal background of hypo and hyperarousal-associated abnormal forms of aggression are markedly different. While the neuronal activation patterns induced by normal rivalry and hypoarousal-driven aggression are qualitative different, hyperarousal-associated aggression appears to be an exaggerated form of rivalry aggression.

Temporal changes in c-Fos activation patterns induced by conditioned fear.

Mechanisms underlying shock-induced conditioned fear - a paradigm frequently used to model posttraumatic stress disorder, PTSD - are usually studied shortly after shocks. Some of the brain regions relevant to conditioned fear were activated in all the c-Fos studies published so far, but the overlap between the activated regions was small across studies. We hypothesized that discrepant findings were due to dynamic neural changes that followed shocks, and a more consistent picture would emerge if consequences were studied after a longer interval. Therefore, we exposed rats to a single session of footshocks and studied their behavioral and neural responses one and 28 days later. The neuronal activation marker c-Fos was studied in 24 brain regions relevant for conditioned fear, e.g. in subdivisions of the prefrontal cortex, hippocampus, amygdala, hypothalamic defensive system, brainstem monoaminergic nuclei and periaqueductal gray. The intensity of conditioned fear (as shown by the duration of contextual freezing) was similar at the two time-points, but the associated neuronal changes were qualitatively different. Surprisingly, however, Multiple Regression Analyses suggested that conditioned fear-induced changes in neuronal activation patterns predicted the duration of freezing with high accuracy at both time points. We suggest that exposure to electric shocks is followed by a period of plasticity where the mechanisms that sustain conditioned fear undergo qualitative changes. Neuronal changes observed 28 days but not 1 day after shocks were consistent with those observed in human studies performed in PTSD patients.

A comparison of activation patterns of cells in selected prefrontal cortical and amygdala areas of rats which are more or less anxious in response to predator exposure or submersion stress.

This study had two purposes. First: to compare predator and water submersion stress cFos activation in medial prefrontal cortices (mPFC) and the medial amygdala (MeA). Second: to identify markers of vulnerability to stressors within these areas. Rats were either predator or submersion stressed and tested 1.75 h later for anxiety. Immediately thereafter, rats were sacrificed and cFos expression was examined. Predator and submersion stress equally increased anxiety-like behavior in the elevated plus maze (EPM) and hole board. To examine vulnerability, rats which were less anxious (LA) and more (highly) anxious (MA) in the EPM were selected from among handled control and stressed animals. LA stressed rats were considered stress non-responsive while MA stressed rats were considered stress responsive. Predator stress, but not submersion stress, activated MeA cFos. CFos expression of mPFC cells was elevated in LA rats and reduced in MA rats in predator stressed animals only, correlating negatively with anxiety. These findings are consistent with data implicating greater mPFC excitability in protection against the effects on affect of traumatic stress. The findings also suggest that this conclusion is stressor specific, applying to predator stress but not submersion stress. Both stressors have been suggested to model hyperarousal and comorbid anxiety aspects of PTSD in humans. Hence the use of these paradigms to identify brain bases of vulnerability and resilience to traumatic stress in PTSD has translation potential. On the other hand, our evidence of stressor specificity of vulnerability/resilience markers raises a caution. The data suggest that preclinical markers of vulnerability/resilience in a given stress paradigm are at best suggestive, and translational value must ultimately be confirmed in humans.

Activation patterns of cells in selected brain stem nuclei of more and less stress responsive rats in two animal models of PTSD - predator exposure and submersion stress.

This study had two purposes. First: compare predator and water submersion stress cFos activation patterns in dorsal raphe (DR), locus coeruleus (LC) and periaqueductal gray (PAG). Second: identify markers of vulnerability to stressors within these areas. Rats were either predator or submersion stressed and tested 1.75 h later for anxiety-like behavior. Immediately thereafter, rats were sacrificed and cFos expression examined. In DR, serotonergic cells expressing or not expressing cFos were also counted. Predator and submersion stress increased anxiety-like behavior (in the elevated plus maze- EPM) equally over controls. Moreover, stressed rats spent equally less time in the center of the hole board than handled controls, another indication of increased anxiety-like behavior. To examine vulnerability, rats which were less anxious (LA) and more (highly) anxious (MA) in the EPM were selected from among handled control and stressed animals. LA rats in the stressed groups were considered stress non-responsive and MA stressed rats were considered stress responsive. LA and MA rats did not differ in cFos expression in any brain area, though stressors did increase cFos cell counts in all areas over controls. Intriguingly, the number of serotonergic DR neurons not activated by stress predicted degree of anxiety response to submersion stress only. LA submersion stressed rats had more serotonergic cells than all other groups, and MA submersion stressed rats had fewer serotonergic cells than all other groups, which did not differ. Moreover, these cell counts correlated with EPM anxiety. We conclude that a surplus of such cells protects against anxiogenic effects of submersion, while a paucity of such cells enhances vulnerability to submersion stress. Other data suggest serotonergic cells may exert their effects via inhibition of dorsolateral PAG cells during submersion stress. Findings are discussed with respect to serotonergic transmission in vulnerability to predator stress and relevance of findings for post traumatic stress disorder (PTSD). This article is part of a Special Issue entitled 'Post-Traumatic Stress Disorder'.

Brain mechanisms involved in predatory aggression are activated in a laboratory model of violent intra-specific aggression.

Callous-unemotional violence associated with antisocial personality disorder is often called 'predatory' because it involves restricted intention signaling and low emotional/physiological arousal, including decreased glucocorticoid production. This epithet may be a mere metaphor, but may also cover a structural similarity at the level of the hypothalamus where the control of affective and predatory aggression diverges. We investigated this hypothesis in a laboratory model where glucocorticoid production is chronically limited by adrenalectomy with glucocorticoid replacement (ADXr). This procedure was proposed to model important aspects of antisocial violence. Sham and ADXr rats were submitted to resident/intruder conflicts, and the resulting neuronal activation patterns were investigated by c-Fos immunocytochemistry. In line with earlier findings, the share of attacks aimed at vulnerable targets (head, throat and belly) was dramatically increased by ADXr, while intention signaling by offensive threats was restricted. Aggressive encounters activated the mediobasal hypothalamus, a region involved in intra-specific aggression, but sham and ADXr rats did not differ in this respect. In contrast, the activation of the lateral hypothalamus that is tightly involved in predatory aggression was markedly larger in ADXr rats; moreover, c-Fos counts correlated positively with the share of vulnerable attacks and negatively with social signaling. Glucocorticoid deficiency increased c-Fos activation in the central amygdala, a region also involved in predatory aggression. In addition, activation patterns in the periaqueductal gray - involved in autonomic control - also resembled those seen in predatory aggression. These findings suggest that antisocial and predatory aggression are not only similar but are controlled by overlapping neural mechanisms.

Lasting changes in social behavior and amygdala function following traumatic experience induced by a single series of foot-shocks.

Neuronal plasticity within the amygdala mediates many behavioral effects of traumatic experience, and this brain region also controls various aspects of social behavior. However, the specific involvement of the amygdala in trauma-induced social deficits has never been systematically investigated. We exposed rats to a single series of electric foot-shocks--a frequently used model of trauma--and studied their behavior in the social avoidance and psychosocial stimulation tests (non-contact versions of the social interaction test) at different time intervals. Social interaction-induced neuronal activation patterns were studied in the prefrontal cortex (orbitofrontal and medial), amygdala (central, medial, and basolateral), dorsal raphe and locus coeruleus. Shock exposure markedly inhibited social behavior in both tests. The effect lasted at least 4 weeks, and amplified over time. As shown by c-Fos immunocytochemistry, social interactions activated all the investigated brain areas. Traumatic experience exacerbated this activation in the central and basolateral amygdala, but not in other regions. The tight correlation between the social deficit and amygdala activation patterns suggest that the two phenomena were associated. A real-time PCR study showed that CRF mRNA expression in the amygdala was temporarily reduced 14, but not 1 and 28 days after shock exposure. In contrast, amygdalar NK1 receptor mRNA expression increased throughout. Thus, the trauma-induced social deficits appear to be associated with, and possibly caused by, plastic changes in fear-related amygdala subdivisions.

The effect of neurokinin1 receptor blockade on territorial aggression and in a model of violent aggression.

BACKGROUND: Neurokinin1 (NK1) receptor blockers were recently proposed for the treatment of anxiety and depression. Disparate data suggest that NK1 receptors are also involved in the control of aggressiveness, but their role is poorly known. METHODS: We evaluated the aggression-induced activation of NK1 neurons by double-labeling brain sections for NK1 receptors and c-Fos in two laboratory models of aggression. We also studied the effects of the NK1 antagonist L-703,606 in these models. RESULTS: Aggressive encounters activated a large number of NK1 receptor-expressing neurons in areas relevant for aggression control. The activation was aggression-specific, because the effects of psychosocial encounters (that allowed sensory but not physical contacts) were markedly weaker. In the medial amygdala, the activation of neurons expressing NK1 receptors showed a marked positive correlation with the occurrence of violent attacks. In resident/intruder conflicts, NK1 blockade lowered the number of hard bites, without affecting milder forms of attack. In the model of violent aggression, attacks on vulnerable body parts of opponents (the main indicators of violence in this model) were decreased to the levels seen in control subjects. Autonomic deficits seen in the model of violent aggression were also ameliorated. The effects of the compound were not secondary to changes in locomotion or in the behavior of intruders. CONCLUSIONS: Our data show that neurons expressing NK1 receptors are involved in the control of aggressiveness, especially in the expression of violent attacks. This suggests that NK1 antagonists-beyond anxiety and depression-might also be useful in the treatment of aggressiveness and violence.

The activation of prefrontal cortical neurons in aggression--a double labeling study.

Violence is associated with prefrontal deficits in humans, suggesting that this brain area inhibits aggressiveness. Its role, however, remains controversial, as certain subdivisions of the prefrontal cortex become activated by fights in rodents. Disparate human findings also show that this area is acutely activated by aggression under certain conditions. We explored prefrontal neuronal activation patterns in resident rats exposed to psychosocial (sensory contact with the intruder) and aggressive encounters. Both psychosocial and aggressive encounters increased c-Fos activation in the prelimbic (PrL), anterior cingular (Cg1), agranular insular (AI), ventral (VO) and lateral orbital (LO) cortices. The infralimbic (IL) and medial orbital (MO) cortices were activated significantly by aggressive encounters only. No other prefrontal regions were activated by psychosocial or aggressive encounters. The overwhelming majority of activated cells were pyramidal (glutamatergic) cells in the Cg1, IL, PrL, MO, and VO, whereas interneuron and pyramidal cell activation was similar in AI and LO. When rats showed violent aggression, the activation of GABAergic inhibitory cells decreased in these two, and two other areas (IL and MO). Notably, the latter two areas appeared to be specifically involved in aggressive behavior. The change occurred in a recently developed model of violent aggression. In this model, pyramidal cell activation in the above mentioned four areas (IL, MO, AI, and LO) predicted over 95% of variation in attack counts in general and violent attacks in particular. Based on these data, we present a tentative hypothesis on the involvement of the prefrontal cortex in the control of aggression.

The activation of raphe serotonergic neurons in normal and hypoarousal-driven aggression: a double labeling study in rats.

The serotonergic system is well known for its aggression lowering effects. It has been shown repeatedly, however, that the serotonergic system is activated during fights, and recent data suggested that it is necessary for the expression of aggressive behavior. We investigated the interaction between serotonergic activation and aggressive behavior by assessing the co-localization of the c-Fos signal (marker of neuronal activation) with tryptophan-hydroxylase activity (marker of serotonin secretion) in the raphe. Control rats were compared with rats exposed to visual and olfactory (but not physical) contacts with opponents (psychosocial stimulation) as well as with rats exposed to aggressive encounters. Fights were accompanied by the activation of the raphe; however, the effect was not aggression-specific, as a similar activation was induced by psychosocial contacts. The lack of behavioral specificity in activation suggests that it was related to social arousal rather than to the execution of fights. The activation of serotonergic raphe neurons showed a negative correlation with aggressive behavior, which is in line with the widespread view that serotonin neurotransmission downregulates aggressive behavior. The activation of serotonergic neurons did not show a correlation with measures of hypoarousal-driven abnormal aggression, which indicates that factors other than the raphe control this behavior. The latter finding may explain the low efficacy of serotonergic treatments in conduct and antisocial personality disorders, in which violence correlates with hypoarousal.