An expanding implant (600) for insertion between first and second regions of hard tissue, the implant comprising: (a) a backbone (630) having a surface for contacting the first region of hard tissue, said backbone comprising a proximal portion (688a) and a distal portion (688b), said backbone assuming an initial length and being shortened towards a second length by relative movement of said proximal portion and said distal portion； (b) a first segment (640c) hingedly connected to a distal region of said distal portion (688b) of said backbone； (c) a second segment (640a) hingedly connected to a proximal region of said proximal portion (688a) of said backbone； and (d) an intermediate segment (640b) having a surface for contacting the second region of hard tissue, said intermediate segment being hingedly connected to said first segment and to said second segment such that shortening of said backbone from said initial length towards said second length causes an increase in a distance between said surfaces of said backbone and said intermediate segment, and wherein said intermediate segment and said backbone are each formed with openings (623) through said respective surfaces, said openings providing at least one unobstructed path between the first and second regions of hard tissue.
