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Use of an Additional Nonlocking Screw in Olecranon Fracture Osteosynthesis Changes Failure Mechanism.

Hardware-related complications can occur when plate fixation is used to stabilize osteoporotic fractures involving the olecranon. The use of an additional nonlocking screw, placed retrograde into the proximal fracture segment, may improve stability under load. The purpose of this study was to conduct a biomechanical comparison of olecranon repair constructs with and without this additional retrograde screw. Nine matched pairs of elderly fresh-frozen cadaveric upper extremities were used. Two-part olecranon fractures were modeled, and fracture stabilization was performed. Olecranon plates were implanted either with the standard surgical technique (CTRL) or with an additional retrograde screw (EXPT). Dynamic extensions of increasingly loaded forearms were performed, and comparisons of sustained cycles, maximum load, and total work were made. Relative motion of bone segments was tracked, and modes of failure were assessed. Seventy-eight percent of specimens from the CTRL group failed due to relative fragment displacement exceeding 3 mm, while 78% of EXPT specimens failed due to instantaneous catastrophic failure. There were no significant differences in terms of number of survived cycles, maximum load, or work performed between the groups. The addition of a retrograde screw in this plating technique changes the failure mode from fracture displacement to catastrophic failure. The use of a 3.5-mm retrograde screw in the relatively small proximal ulnar fragment should be avoided, but screws with a smaller diameter may still have potential to improve fixation. Further biomechanical and clinical research is necessary to improve strategies for plate fixation of olecranon fractures in the elderly population. [Orthopedics. 2019; 42(1):e74-e80.].