A cylinder block has a cast cylinder liner. The femoral component is configured to be implanted into a distal end of a femur of a patient and includes a stem post having a proximal tapered bore, a distal passageway, and a threaded passageway connecting the proximal tapered bore and the distal passageway. These products can be returned to the source, stored, transported, sold, or otherwise reused. An output of the comparator drives a configuration memory. In one embodiment, the diffuser can define tubes that extend from the inside surface of the diffuser to the outside surface of the diffuser, to permit more equal drug flow through the tubes defined therein.