A transdermal intraosseous device for coupling a bone stump to an external prosthetic device includes a bone fixator, an external connector and a plurality of modular interface components. The bone fixator includes a proximal portion configured for anchoring into the bone stump of the patient and a distal portion including a base collar configured for subcutaneous implantation. The external connector has a distal portion for coupling to the external prosthetic device and a proximal portion for coupling to the distal portion of the bone fixator. Each interface component can be removably coupled to the base collar and has different size and shape to provide a surgeon-selected transition between the prosthetic device and the patient's skin.