An analysis of a retrieved Prodigy femoral prosthesis

Radiographic and histologic data of an autopsy-retrieved femur containing a Prodigy stem (DePuy, Warsaw, IN) in situ for 26 months were analyzed. The Prodigy is a porous-coated Anatomic Medullary Locking stem modified with a smooth groove, the Redux Groove, on its medial central portion. This Redux Groove, designed to increase stem flexibility and decrease periprosthetic bone resorption, decreases the porous surface area available for bone ingrowth. In this case, however, the decreased porous area did not affect diaphyseal bone ingrowth. Additionally, although there is a concern that the groove will provide a pathway for debris migration, no evidence of debris was found in the tissue at the groove site. Although the Redux Groove's value in decreasing periprosthetic bone loss is still uncertain, this case demonstrated less proximal bone loss than was reported in similar dual-energy x-ray absorptiometry studies of autopsy cases containing Anatomic Medullary Locking stems without a groove. Analysis of more cases with longer in situ intervals is necessary to determine if the groove decreases resorptive bone remodeling and if the groove becomes a conduit for particulate debris migration. It is emphasized that results of this one case may not be representative of all Prodigy cases.