I would bill as follows:
L1907 LT
L1907 RT
L1970 LT
L1970 RT
Your particular BCBS may require KX modifiers, in which case they would go on each line before the LT and RT modifiers. Also keep in mind that they may have a MUE of 1 for these codes, in which case you can't bill more than one on a particular DOS...but that is usually not the case with these codes. Some patients do require them for both ankles/feet at once.