Cancellous bone support for patellar resurfacing.

The purpose of this study was to determine the compressive resistance of the cancellous bone in nine fresh specimens of human patellae. Standardized radiographic assessment and subsequent osteotomies were performed on each specimen. Grid patterns based on patellar anatomy enabled topographic compression on a material test system (MTS) Model 835 Bionix Universal Testing Machine (MTS Corporation, Minneapolis, MN) using a 4-mm diameter indentor. It was demonstrated that sacrifice of the patellar subchondral bone removes with it the strong cancellous bone support and topographic strength patterns of the cancellous bone on the surface of a patellar osteotomy does not have a consistent pattern in relation to the intracondylar eminence. Consequently, placement of fixation pegs is not critical with respect to strength of bony support.