It depends, I guess, on the exact site of blockade. I think if you're doing a proper ankle block (getting the 5 terminal branches), then you may be able to try to bill for all five, but what you'll actually be reimbursed is a different story. To bill (and collect) for fem and sciatic, though, you'd probably have to do fem and sciatic blocks proper.
When i do blocks for postop analgesia for ankle cases, I usually do a sciatic (either midthigh or at the popliteal fossa) and saphenous block (at the tibial plateau). The -59 modifier comes into play if you do them under Ultrasound and have documented the imaging. Hope this helps.