Metatarsal synostosis Synostosis involving the 1st metatarsal First ray metatarsophalangeal synostosis 2010-11-18T06:24:21Z Congenital fusion of the firth metatarsal bone with the proximal phalanx of the hallux. HP:0100488 Fusion of the innermost big toe bone with the 1st long bone of foot UMLS:C4022043