The palmar digital nerve block (also called a PD or heel block) would anesthetize at least the palmar third of the foot, including the navicular bone.
Historically, the PD block was considered to anesthetize the palmar/plantar 1/3 of the foot and sole. However, it has been shown that it desensitizes 70-80% of the foot in most horses.
All of the other nerve blocks can desensitize the navicular bone too, but would not be as specific as a palmar digital nerve block because they also desensitize a larger region.
The abaxial sesamoidean nerve block (ASNB, also called a pastern or foot block) would anesthetize the entire foot and much of the pastern. Sometimes an ASNB is needed to completely eliminate or diagnose navicular lameness, but it is less specific than the PD block.
A low four-point nerve block (also called low palmar or volar block) would desensitize the fetlock and areas distal to it.
The median and ulnar nerve block would anesthetize the carpus and areas distal to it.
Click here to see forelimb nerve block landmarks.
The tibial and peroneal nerve block would anesthetize the tarsus and areas distal to it.
Click here and scroll down to see pelvic limb nerve block landmarks.
