An interface device for engagement with an osseointegrated device implanted in an amputated limb comprising a cap portion 600 engageable with an osseointegrated device, wherein the cap portion 600 comprises a surrounding flange 680 which engages the skin 603 of the amputated limb at a distance spaced from the osseointegrated device. The dimensions of the surrounding flange 680 create homeostasis barrier with the patients skin 603. The cap portion 600 may connect to a stem portion 630. The cap portion 600 may have ports 620 for allowing cables or wires 690 to pass through, such that nerve cuffs or muscle activation sensing electrodes may be monitored and controlled. The ports 620 may also provide access for keyhole surgery, medicine administration or draining of fluids
