Why filtic function does not work for a specific use?

Hello users,

I designed a filter via bilinear transformation in order to obtein a high-pass filter of Butterworth. When I want to set initial conditions with filtic function, it does not give me what I expect. I have a signal with an offset, then I filter that with the designed filter. But the case is that the first values of the filtered signal are still remaining from the original offset.

[num_s, den_s] = butter(2, 1, 'high', 's');
        r = F_c*PIOD;
        F_a = 1/(2*pi);
        F_s = F_a/r;
[NUM_z, DEN_z] = bilinear(num_s, den_s, F_s, F_a);

newOffset = 0;% I set the parameter in that way because the filter removes all low-frecuency
% components of my signal.

iniConds = filtic(NUM_z, DEN_z, [newOffset newOffset])