Biomechanical and histological evaluation of the Herbert screw.

The Herbert screw has been demonstrated to have widespread clinical applicability. A biomechanical and histological evaluation of the Herbert screw was conducted to better define its applications. When subjected to pull-out, toggle, and compression testing, in a cancellous bone calf model, it was demonstrated to be biomechanically inferior to the 4.0 mm ASIF cancellous screw. The use of two Herbert screws minimized but did not eliminate this difference. Articular cartilage healing in a rabbit model was consistently demonstrated if the Herbert screw was buried deep to the osteochondral junction. However, toluidine blue histochemical staining showed that the hyaline-like repair cartilage differed qualitatively from normal cartilage. Utilization of the Herbert screw should include an understanding of the limitations of its fixation potential and a recognition of the repair response after intraarticular applications.