The invention relates to an intramedullary implant (1) for immobilizing the articulation between two phalanges of the hand or foot, which implant (1) is composed of a one-piece elongate body of longitudinal axis (<；u>；L<；/u>；) comprising first and second end-anchoring parts (2 and 3) of generally planar form which are connected rigidly by an intermediate part (4) and which extend in planes (<；u>；P1<；/u>；) and (<；u>；P2<；/u>；) perpendicular or substantially perpendicular to each other. The first end-anchoring part (2) has the general shape of a U with a base (5) attached to said intermediate part (4), and with two arms (6<；u>；a<；/u>；, 6<；u>；b<；/u>；) extending parallel or substantially parallel to each other starting from said base (5)； and the second end-anchoring part (3) is in the form of a plate (10) attached to said intermediate part (4) by a base (11), which plate (10) is delimited by two faces (10<；u>；a<；/u>；, 10<；u>；b<；/u>；), parallel to each other and parallel to said plane (P2), by a free end (13), and by two lateral borders (10<；u>；c<；/u>；, 10<；u>；d<；/u>；), which lateral borders (10<；u>；c<；/u>；, 10<；u>；d<；/u>；) have a plurality of juxtaposed teeth (12).
