[Biomechanical study of four palmar locking plates and one non-locking palmar plate for distal radius fractures: stiffness and load to failure tests in a cadaver model].

Five different palmar fixation plate designs were compared in a distal radial osteotomy cadaver model with regard to their biomechanical properties. A metaphyseal osteotomy gap of 1 cm was performed and the osteosynthesis was plated according to the manufacturer's instructions. Axial load was applied to the construct by a pneumatic material testing machine. Five implant groups with eight cadavers each were tested concerning stiffness. None of the constructs developed deformity and movement of the fracture gap larger than 2 mm with a load of 100 N. Increasing the load to 250 N revealed significant differences in stiffness and failure load between the different plates. The mean stiffness under axial load (mean+/-standard deviation) was 356.4+/- 138.6 N/mm for the radius correction plate without lateral tongue, 299.7+/-86.3 N/mm for the radius correction plate with lateral tongue, 132.8+/-41.5 N/mm for the distal volar radius plate, 112.5+/-40.2 N/mm for the 3.5 mm titanium locking compression plate and 91.9+/-29.2 N/mm for the standard stainless steel 3.5 mm T-Plate. The non-angular stable implant (STP plate) had the lowest stiffness. Unexpectedly, there were differences over 100% concerning the stiffness between the at first glance nearly similar angular stable implants. Additionally, a review of the literature concerning biomechanical investigations of the distal radial fracture was performed.