A comparison of parallel and diverging screw angles in the stability of locked plate constructs

作者：Waehnert D^*; Windolf M; Brianza S; Rothstock S; Radtke R; Brighenti V; Schwieger K

来源：Journal of Bone and Joint Surgery-British Volume, 2011, 93B(9): 1259-1264.

DOI：10.1302/0301-620X.93B9.26721

We investigated the static and cyclical strength of parallel and angulated locking plate screws using rigid polyurethane foam (0.32 g/cm(3)) and bovine cancellous bone blocks. Custom-made stainless steel plates with two conically threaded screw holes with different angulations (parallel, 10 degrees and 2 degrees divergent) and 5 mm self-tapping locking screws underwent pull-out and cyclical pull and bending tests. The bovine cancellous blocks were only subjected to static pull-out testing. We also performed finite element analysis for the static pull-out test of the parallel and 20 degrees configurations. In both the foam model and the bovine cancellous bone we found the significantly highest pull-out force for the parallel constructs. In the finite element analysis there was a 47% more damage in the 20 degrees divergent constructs than in the parallel configuration. Under cyclical loading, the mean number of cycles to failure was significantly higher for the parallel group, followed by the 10 degrees and 20 degrees divergent configurations.
In our laboratory setting we clearly showed the biomechanical disadvantage of a diverging locking screw angle under static and cyclical loading.

• 出版日期2011-9