The first MTP, also called the first metatarsophalangeal joint, is the big toe joint. A first MTP joint fusion is a surgical procedure to treat arthritis of the big toe. This condition can cause pain and swelling and lead to difficulty walking, running, and wearing shoes. Arthritis develops when the cartilage on each bone wears away and the two bones that make up the big toe joint rub against one another.
In a first MTP joint fusion, the bones are joined (fused) together permanently so they cannot rub against each other and cause pain.