Nerve blocking particular leg structures is a method veterinarians can use to help locate, or confirm, the location of pain associated with lameness. Veterinarians will inject an analgesic to numb the nerves in the area suspected to be the source of pain. Many chronic hoof and leg ailments present as lameness without enough specific characteristics to determine the location of the pain. In this case your veterinarian may begin by numbing the lowest structure on the leg and work their way up the leg.
The numbing affect is seen about 5 minutes after injecting. The veterinarian will then perform a lameness evaluation. The horse will be asked to jog in a straight line away from them, and them towards them. The horse may also be asked to work on the lounge line while the doctor evaluates gate and transitions.
A horse is considered to have “blocked sound” when lameness is no longer exhibited.
Types of Nerve Blocks
Palmar Digital Nerve Block (Heel Block) – The block targets the back of the foot. It is injected over the palmar digital nerve just under the skin. It blocks the heel bulbs, frog, navicular bone, navicular bursa, the coffin joint, and the phalanx.
Abaxial Sesamoid Nerve Block – The block targets the palmar nerve: includes the medial and lateral palmer and the dorsal branch. The nerve runs along the back of the pastern. It blocks the deep digital flexor tendons in the foot, pastern joint and may numb portions of the fetlock joint.
Coffin Joint Block – The block targets the coffin joint. It is placed above the coronet band on the front of the hoof. This block will numb the coffin joint.
Navicular Bursa Block – This block targets the navicular bursa and is placed between the heel bulbs just above the coronet band. Radiographs are used to determine accurate placement.This block will numb the navicular bursa, supporting ligaments, the sole in the toe of the hoof and deep digital flexor tendon.
Once the location of pain is better identified your veterinarian will begin further diagnostics to determine the cause of the pain and develop a treatment plan.