Fixation properties of a biodegradable “free-form” osteosynthesis plate with screws with cut-off screw heads: Biomechanical evaluation over 26 weeks

ObjectiveThe aim of this study was to compare the postoperative fixation properties of a biodegradable osteosynthesis “free-form” plate achieved with countersunk screws with those provided by screws with cut-off screw heads.Study designAcrylic pipes were fixed together to simulate fracture fixation for tensile testing. Additional plates were fixed to a polyurethane block with a single screw for plate-screw pullout testing. Specimens were incubated in phosphate buffer solution at 37°C, and testing was conducted at various time points during hydrolytic degradation of 26 weeks. In both tests the specimens were loaded at a speed of 5 mm/min until failure. The yield load, maximum load, and stiffness were recorded, and failure mode was visually determined.ResultsBoth countersunk screws and screws with cut-off screw heads provided similar plate fixation properties over degradation time.ConclusionAccording to these results, fixation of the biodegradable osteosynthesis free-form plate with screws with cut-off screw heads seems to be feasible.