• Clemens Gwinner, Sven Märdian, Tobias Dröge, Martin Schulze, Michael J Raschke, and Richard Stange.
• Centre for Musculoskeletal Surgery, Charité - University Medicine Berlin, Augustenburger Platz 1, 13353, Berlin, Germany, clemens.gwinner@charite.de.
• Int Orthop. 2015 Sep 1; 39 (9): 1749-55.

PurposeThe incidence of periprosthetic fractures is inevitably increasing. Sufficient stabilisation and proper screw placement next to large-volume implants remains difficult. Modern locking plates allow polyaxial, thus bicortical, screw placement around a prosthetic stem. This study analysed the biomechanical properties of different screw configurations in a locking plate construct of a periprosthetic femoral fracture model.MethodsA total of 20 Sawbones were used to stabilise a Vancouver-B1 femoral fracture with a locking plate using either four monocortical screws or three bicortical screws for proximal fixation. These were loaded with an increasing axial compression until failure.ResultsBicortical screw purchase was significantly superior to monocortical regarding load to failure (1,510 N ± 284 N versus 2,350 N ± 212 N, p < 0.001) and maximal number of cycles (6803 ± 760 versus 4041 ± 923, p < 0.001). However, the mode of failure in the bicortical group was a severe comminuted fracture pattern as opposed to the monocortical group in which a pull-out of the screws without further damage to the bone was observed.ConclusionsBicortical screw placement enhances the primary stability in treating periprosthetic femoral fractures. Notably, the mode of failure may limit the salvage options in case of revision surgery.

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