Cancellous and cortical morselized allograft in revision total hip replacement:: A biomechanical study of implant stability

To restore femoral intramedullary bone stock loss in revision surgery of failed total hip arthroplasties, impacted morselized cancellous allograft is recommended. This study investigated the mechanical properties of both impacted cortical (group A) and cancellous (group B) morselized bone graft for reconstruction of femoral bones. Ten matched pairs of fresh frozen human femora were prepared by over-reaming to create a smooth-walled cortical shell. Each pair had one cortical and one cancellous impacted morselized allograft and cement. Stem subsidence was evaluated by a cyclic axial load, which was applied by a servohydraulic test. The stem subsidence was measured for initial subsidence (subsidence at the first 1000 cycles), the total axial subsidence (subsidence at the end of cycles under load) and the final axial subsidence (subsidence after the unloading phase). Torque test was measured by torsional loads through the prosthetic femoral heads. Total axial subsidence was significantly higher in group B (mean: 1.32±0.32 mm) compared to group A (mean: 0.94±0.26 mm) (P<0.01). There was no significant difference between the two groups in terms of initial subsidence (P=0.09) and final axial subsidence. The mean maximum torque before failure was 39.5±22.2 N-m for the cortical morselized allograft and 32.5±18.1 N-m for cancellous. We concluded that impacted morselized cortical bone graft used for reconstruction of contained femoral bone loss in revision hip arthroplasy, may reduce the stem subsidence. Further animal experimentation for mechanical and histological evaluation of in vivo application is warranted.