Biomechanical properties of new mini compression screws.

Background: The aim of the current study was to compare the compression forces achieved by the new commercial mini compression screws in cortical and cancellous bone. Materials and Methods: The following screws were tested: AO partially threaded 4-mm cancellous screw, AO 3.5- and 2.7-mm cortical screws (Synthes - USA), self-tapping cannulated 3-mm VisAntares (FOS - France), 3- and 2.3-mm Omnitech (Biotech - France), 3-mm Barouk (DePuy - France), and 3-mm Bold screws (Newdeal - France). The compression forces of screws in bone were tested using a load cell between pieces of longitudinally-split sheep tibias as a cortical and cancellous bone model. Results: The AO 3.5-mm, 2.7-mm cortical anti 4.0-mm partially threaded cancellous headed screws provided significantly (p <= 0.05) better compression forces than all the tested headless screws, both in cortical and cancellous bone. A loss of compression was noted when the headless screws were totally countersunk. Conclusion: The cortical and cancellous screws with heads provided superior compression than headless screws. Clinical Relevance: Headed screws may be preferable to headless differential pitch screws in situations where compression is important ie, arthrodeses or fracture fixation. Care should be taken not to countersink the headless screws during insertion into cortical bone.