• David J Hak, Ryan Fader, Todd Baldini, and Vivek B S Chadayammuri.
• Department of Orthopedic Surgery, Denver Health Medical Center / University of Colorado, Denver, CO, USA. David.hak@dhha.org.
• Int Orthop. 2017 Sep 1; 41 (9): 1735-1739.

PurposeCarbon-fibre reinforced polyetheretherketone (CFR-PEEK) plates have recently been introduced for proximal humerus fracture treatment. The purpose of this study was to compare the locking screw-plate interface stability in CFR-PEEK versus stainless steel (SS) proximal humerus plates.MethodsLocking screw mechanical stability was evaluated independently in proximal and shaft plate holes. Stiffness and load to failure were tested for three conditions: (1) on-axis locking screw insertion in CFR-PEEK versus SS plates, (2) on-axis locking screw insertion, removal, and reinsertion in CFR-PEEK plates, and (3) 10-degree off-axis locking screw insertion in CFR-PEEK plates. Cantilever bending at a rate of 1 mm/minute was produced by an Instron machine and load-displacement data recorded.ResultsShaft locking screw load to failure was significantly greater in CFR-PEEK plates compared to SS plates (746.4 ± 89.7 N versus 596.5 ± 32.6 N, p < 0.001). The stiffness and load to failure of shaft locking screws was significantly decreased when inserted 10 degrees off-axis compared to on-axis in CFR-PEEK plates (p < 0.001). Stiffness and load to failure did not vary significantly following screw reinsertion in CFR-PEEK plates.ConclusionThe mechanical stability of locking screws in CFR-PEEK plates is comparable or superior to locking screws in SS plates.

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