An implant assembly for receipt into an end of a long bone having a longitudinal axis, wherein the implant assembly is configured to support a prosthesis positioned external to the long bone, the implant assembly comprising: a. a stem having a longitudinal axis and an outer surface, wherein the stem is configured to be received in a surgically prepared medullary canal of the long bone such that the longitudinal axis of the stem is substantially aligned with the longitudinal axis of the long bone; b. wherein the stem defines at least one transverse through-opening that extends through the stem from a first portion of the outer surface of a shaft of the stem to an opposed second portion of the outer surface of the shaft of the stem, wherein each transverse through-opening of the at least one transverse through-opening has a central axis (39a/b) that is substantially perpendicular to the longitudinal axis of the stem, wherein each transverse through-opening of the at least one through-opening is configured to receive a respective fastener that is secured to the long bone, and wherein each transverse through-opening of the at least one through-opening has a longitudinal dimension, measured relative to the longitudinal axis of the stem, that is sufficient to permit axial movement, relative to the longitudinal axis of the stem, of the stem relative to each fastener within the at least one transverse through-opening, thereby allowing the fastener to apply resistance to tensile load while allowing for dynamic compression of the long bone; and c. wherein the stem has an insertional first end portion and an opposed second end portion, wherein the second end portion of the stem defines a surface comprising a porous structureto promote bone ingrowth. a. a stem having a longitudinal axis and an outer surface, wherein the stem is configured to be received in a surgically prepared medullary canal of the long bone such that the longitudinal axis of the stem is substantially aligned with the longitudinal axis of the long bone; b. wherein the stem defines at least one transverse through-opening that extends through the stem from a first portion of the outer surface of a shaft of the stem to an opposed second portion of the outer surface of the shaft of the stem, wherein each transverse through-opening of the at least one transverse through-opening has a central axis (39a/b) that is substantially perpendicular to the longitudinal axis of the stem, wherein each transverse through-opening of the at least one through-opening is configured to receive a respective fastener that is secured to the long bone, and wherein each transverse through-opening of the at least one through-opening has a longitudinal dimension, measured relative to the longitudinal axis of the stem, that is sufficient to permit axial movement, relative to the longitudinal axis of the stem, of the stem relative to each fastener within the at least one transverse through-opening, thereby allowing the fastener to apply resistance to tensile load while allowing for dynamic compression of the long bone; and c. wherein the stem has an insertional first end portion and an opposed second end portion, wherein the second end portion of the stem defines a surface comprising a porous structureto promote bone ingrowth.