Pullout strength of a biodegradable free form osteosynthesis plate.

The Inion(®) Free Form Plate is a newly designed biodegradable plate. After drilling through the plate and tapping, a biodegradable screw can be inserted, followed by removal of the screw head. As an alternative a countersink screw can be used. Aim of the study was to compare the mechanical properties of the 1.4 mm Free Form Plate with the 2.0 mm conventional shaped plate. Mechanical testing of the plate pullout strength was conducted for the Inion(®) Free Form Plate fixed with an Inion OTPS™ 2.0 × 20 mm Screw. In addition, the failure mode was reported. Overlapping confidence levels were found with regard to the yield load, first peak load and maximum load, when comparing the Free Form Plate and the conventional 4-hole plate. The Free Form Plate fixed with a screw with head and countersink showed the highest stability at maximum load. The results of the mechanical stability testing showed no significant differences between the tested plates. The main failure mode was a failure of the screw shaft. The results of the current investigation imply that the 1.4 mm Free Form Plate could be used as an alternative to the 2.0 mm conventional shaped plate.

Fixation properties of a biodegradable "free-form" osteosynthesis plate with screws with cut-off screw heads: biomechanical evaluation over 26 weeks.

OBJECTIVE: The 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 DESIGN: Acrylic 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 degrees 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. RESULTS: Both countersunk screws and screws with cut-off screw heads provided similar plate fixation properties over degradation time. CONCLUSION: According to these results, fixation of the biodegradable osteosynthesis free-form plate with screws with cut-off screw heads seems to be feasible.

Biomechanical in vitro evaluation of the effect of cyclic loading on the postoperative fixation stability and degradation of a biodegradable ankle plate.

The effect of cyclic loading on the postoperative fixation stability of a biodegradable ankle plate was tested biomechanically during 12 weeks of hydrolytic degradation. Fracture of the lateral malleolus was simulated, and the parameters of cyclic loading were chosen to represent the physiological conditions during the healing period. Additionally, the effect of cyclic loading on degradation was investigated by measuring the inherent viscosities. In Group I, the cyclic loading was conducted in four phases with gradual increases in estimated walking distance and speed during the healing period. In Group II, cyclic loading was conducted after 12 weeks. Group III was used as a control for inherent viscosity measurements. None of the specimens failed under cyclic loading. No significant differences were found between the loaded groups in any of the parameters measured. Additionally, no significant difference was found in inherent viscosities at 12 weeks. The initial fixation stability provided by the biodegradable ankle plate remains biomechanically unchanged over 12 weeks. Cyclic loading, applied either during or after 12 weeks of hydrolytic degradation, does not seem to have any clinically relevant effect on the fixation stability or the degradation properties.

Fixation properties of a biodegradable "free-form" osteosynthesis plate.

The Inion FreedomPlate, a "free-form" osteosynthesis plate, is a biodegradable plate with just pilot holes for drilling. The construction of the plate allows the surgeon a placement of screws in optimal position. The screw heads can either be countersunk into the plate or cut off. Furthermore, the plate can be cut and contoured to match the bone. The aim of this study was to determine the mechanical properties of the Inion FreedomPlate compared to a conventional biodegradable plate. Acrylic pipes were fixed together with plates and screws. Tensile and cantilever bending tests were performed to measure the fixation properties. In the tensile test, the samples were loaded with a constant speed of 5 mm/min until failure of fixation. The yield load, maximum failure load, and initial stiffness were recorded, and the failure mode was visually determined. In the cantilever bending test, the samples were loaded with a constant speed of 50 mm/min (with a moment arm of 45 mm) until failure of fixation. The yield bending moment and initial stiffness were recorded, and the failure mode was determined. The results of the study show that the new free-form plate provides at least as strong fixation as the tested conventional biodegradable plate. No clinically relevant difference was found between free-form plates fixed with into-the-plate countersunk screws and those fixed with screws without heads.