Durability and strength of Steinmann pin augmentation in cemented tibial defects.

Abstract

It has been argued that Steinmann pin augmentation does not improve the biomechanics of polymethylmethacrylate reconstruction for massive defects of bone. The current authors investigated whether pin augmentation of polymethylmethacrylate in the reconstruction of noncontained defects of bone improved the biomechanical properties of the reconstruction as compared with polymethylmethacrylate alone when minimal or large bone porosity is present. Large noncontained defects were created in 10 pairs of human tibias. In Group 1, five left tibias had reconstruction with polymethylmethacrylate augmented with three, 5-mm diameter by 10-mm deep holes into lateral condyle cancellous bone. Right tibias had identical reconstruction with three, 3/16-inch threaded pins placed into the medullary canal. In Group 2, three, 10-mm diameter by 10-mm deep holes were created in both pairs. The left tibia had polymethylmethacrylate reconstruction and the right tibia had polymethylmethacrylate and pin augmentation. Specimens were subjected to 2000 compressive cycles then loaded to failure. In Group 1, cycles and load to failure were significantly lower in reconstructions without pins compared with reconstructions with pins. No significant difference was observed between reconstruction techniques in Group 2. In reconstructions without pins, large diameter holes had significantly better cyclical durability. Pins improved survival compared with no pins.