EFFECTS OF CORONALLY SLOTTED FEMORAL PROSTHESES ON CORTICAL BONE STRAIN

The photoelastic method was used to assess the effects on femoral cort ical strain of total hip arthroplasty cementless femoral prostheses co ntaining distal coronal slots. Eight cadaveric femurs were tested, alt hough three were eliminated secondary to fractures. Loaded and unloade d cortical strains were determined at 72 points on the implanted femor al cortex and compared with the values obtained in the intact femur. T hree different prostheses were sequentially implanted, in a random ord er, into each femur. The prostheses consisted of a standard solid stem , an identical stem with a coronal slot in its distal one fourth, and an identical stem with a coronal slot in its distal one half. The slot ted stems did not enhance axial load transfer to the proximal medial f emur but did result in increased proximal medial assembly strains and statistically significant (P < .05) decreased anterior and posterior a ssembly strains. The increased proximal medial assembly strains are hy pothesized to enhance proximal medial femoral loading, while the decre ased anterior and posterior assembly strains may minimize operative im plantation fractures.