A modular implant for the fixation or fusion of the SI-Joint, the modular implant having an elongate body that extends in a longitudinal direction between a distal end and a proximal end, said elongate body comprising: a distal module comprising a frame, the frame joined to a distal guide pin receptacle and to a plurality of transverse support struts arranged perpendicularly to the longitudinal direction and in a rectilinear configuration; a proximal module comprising a frame, the frame joined to a proximal guide pin receptacle and to a plurality of transverse support struts arranged perpendicularly to the longitudinal direction and in a rectilinear configuration; and at least one repeating internal module comprising: a plurality of apex struts that extend in the longitudinal direction and are joined together by oblique support struts arranged in an oblique configuration between the apex struts, a plurality of transverse support struts arranged perpendicularly to the longitudinally extending apex struts, the plurality of transverse support struts arranged in a rectilinear configuration at both a proximal end and a distal end of the repeating internal module, and an internal guide pin receptacle secured to the support struts and/or apex struts and arranged with respect to both the distal guide pin receptacle and the proximal guide pin receptacle to allow a cannula to extend along the length of the elongate body through the proximal, internal and distal guide pin receptacles, wherein the at least one internal repeating module is positioned between the distal module and the proximal module such that the transverse support struts of the distal module are adjacent and parallel to a first set of transverse support struts of the repeating internal module and the transverse support struts of the proximal module are adjacent and parallel to a second set of transverse support struts of a repeating internal module. a distal module comprising a frame, the frame joined to a distal guide pin receptacle and to a plurality of transverse support struts arranged perpendicularly to the longitudinal direction and in a rectilinear configuration; a proximal module comprising a frame, the frame joined to a proximal guide pin receptacle and to a plurality of transverse support struts arranged perpendicularly to the longitudinal direction and in a rectilinear configuration; and at least one repeating internal module comprising: a plurality of apex struts that extend in the longitudinal direction and are joined together by oblique support struts arranged in an oblique configuration between the apex struts, a plurality of transverse support struts arranged perpendicularly to the longitudinally extending apex struts, the plurality of transverse support struts arranged in a rectilinear configuration at both a proximal end and a distal end of the repeating internal module, and an internal guide pin receptacle secured to the support struts and/or apex struts and arranged with respect to both the distal guide pin receptacle and the proximal guide pin receptacle to allow a cannula to extend along the length of the elongate body through the proximal, internal and distal guide pin receptacles, a plurality of apex struts that extend in the longitudinal direction and are joined together by oblique support struts arranged in an oblique configuration between the apex struts, a plurality of transverse support struts arranged perpendicularly to the longitudinally extending apex struts, the plurality of transverse support struts arranged in a rectilinear configuration at both a proximal end and a distal end of the repeating internal module, and an internal guide pin receptacle secured to the support struts and/or apex struts and arranged with respect to both the distal guide pin receptacle and the proximal guide pin receptacle to allow a cannula to extend along the length of the elongate body through the proximal, internal and distal guide pin receptacles, wherein the at least one internal repeating module is positioned between the distal module and the proximal module such that the transverse support struts of the distal module are adjacent and parallel to a first set of transverse support struts of the repeating internal module and the transverse support struts of the proximal module are adjacent and parallel to a second set of transverse support struts of a repeating internal module.