A Biomechanical Evaluation of Press-Fit Stem Constructs for Tumor Endoprosthetic Reconstruction of the Distal Femur

This study was designed to assess the biomechanical parameters of the older Kotz Modular Femur Tibia Reconstruction (Stryker Inc, Mahwah, NJ) stem and the newer Restoration and the unfluted Global Modular Replacement System (Stryker Inc Mahwah, NJ) uncemented stems for use with tumor endoprostheses as well as to assess the optimal reaming technique for insertion of these stems. Fresh-frozen adult femora or composite distal femora were implanted with the uncemented stems. Separate experiments were performed to compare reaming technique and bone resection level. All constructs were mechanically tested for axial compression, lateral bending, and torsional stiffness and torque to failure. Results showed that the biomechanical performance of all the stems were similar with respect to each parameter. Cylindrical reaming was associated with a significantly higher torque to failure than flexible reaming in the diaphysis (P = .006). Newer uncemented stems provide adequate initial biomechanical stability for implantation in the distal femur.