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. <EOS>