MVVM Command binding for contextemenu of TreeView Element

I need to bind a command (RelayCommand) of my ViewModel with the click event on an element of the conetxtmenu for a treeviewitem

ViewModel Command

private RelayCommand _myElementCommand;
public RelayCommand MyCommand
{
    get
    {
        return _myElementCommand?? (_myElementCommand= new RelayCommand(
           x =>
           {
               //LoadData();
               MessageBox.Show("Clicked!");
           }));
    }
}

VIEW

<TreeView x:Name="tvUBR" ItemsSource="{Binding UBRList, UpdateSourceTrigger=PropertyChanged}">
    <TreeView.ItemTemplate>
        <HierarchicalDataTemplate ItemsSource="{Binding Children}">
            <StackPanel Orientation="Horizontal">
                <TextBlock VerticalAlignment="Center" Text="{ Binding Description }">
                    <TextBlock.Style>
                        <Style TargetType="TextBlock">
                            <Setter Property="Foreground" Value="Black" />
                            <Style.Triggers>
                                <DataTrigger Binding="{Binding IsMatch}"
                                                Value="True">
                                    <Setter Property="Foreground" Value="Green" />
                                </DataTrigger>
                            </Style.Triggers>
                        </Style>
                    </TextBlock.Style>
                    <TextBlock.ContextMenu>
                        <ContextMenu>
                            <!--<MenuItem Header="Details" Command="{Binding DropedElementCommand, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=Window}}"/>-->
                            <MenuItem Header="Details">
                                <i:Interaction.Triggers>
                                <!-- EventName ??? -->
                                    <i:EventTrigger EventName="Click"> 
                                        <i:InvokeCommandAction Command="{Binding Path=PlacementTarget.Tag.DataContext.MyCommand, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=Window}}"/>
                                    </i:EventTrigger>
                                </i:Interaction.Triggers>
                            </MenuItem>
                        </ContextMenu>
                    </TextBlock.ContextMenu>
                </TextBlock>
            </StackPanel>
        </HierarchicalDataTemplate>
    </TreeView.ItemTemplate>
    <i:Interaction.Triggers>
        <i:EventTrigger EventName="SelectedItemChanged">
            <i:InvokeCommandAction Command="{Binding SelectedUBRElementCommand}" 
                                            CommandParameter="{Binding SelectedItem, ElementName=tvUBR}" />
        </i:EventTrigger>
    </i:Interaction.Triggers>
    <TreeView.ItemContainerStyle>
        <Style TargetType="{x:Type TreeViewItem}">
            <Setter Property="b:TreeViewItemBehavior.IsBroughtIntoViewWhenSelected" Value="True" />
            <Setter Property="IsExpanded" Value="{Binding IsExpanded, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}" />
            <Setter Property="IsSelected" Value="{Binding IsSelected, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}" />
        </Style>
    </TreeView.ItemContainerStyle>
</TreeView>

Any idea how to achieve this?

You could bind the Tag property of the TextBlock to the view model and then bind to the command using the PlacementTarget property of the ContextMenu:

<HierarchicalDataTemplate ItemsSource="{Binding Children}">
    <StackPanel Orientation="Horizontal">
        <TextBlock VerticalAlignment="Center" Text="{ Binding Description }">
            <TextBlock.Style>
                <Style TargetType="TextBlock">
                    <Setter Property="Tag" Value="{Binding DataContext, RelativeSource={RelativeSource AncestorType=TreeView}}" />
                    <Setter Property="Foreground" Value="Black" />
                    <Style.Triggers>
                        <DataTrigger Binding="{Binding IsMatch}" Value="True">
                            <Setter Property="Foreground" Value="Green" />
                        </DataTrigger>
                    </Style.Triggers>
                </Style>
            </TextBlock.Style>
            <TextBlock.ContextMenu>
                <ContextMenu>
                    <MenuItem Header="Details"
                              Command="{Binding PlacementTarget.Tag.MyCommand, RelativeSource={RelativeSource AncestorType=ContextMenu}}" />
                </ContextMenu>
            </TextBlock.ContextMenu>
        </TextBlock>
    </StackPanel>
</HierarchicalDataTemplate>