An allograft implant for fusing a sacroiliac joint, the allograft implant having a body with two opposing faces. A graft window is disposed between the two opposing faces, the graft window providing passage through the body between the two opposing faces. A portion of the body located between the graft window and each of the sides defines a wall such that the wall maintains a minimum thickness in a range of about 17% to about 20% of the width of the body.