Low-Profile Double Plating of Unstable Osteoporotic Olecranon Fractures: A Biomechanical Comparative Study.

Abstract: Background In the treatment of unstable olecranon fractures, anatomically preshaped locking plates exhibit superior biomechanical results compared to tension band wiring. However, posterior plating still is accompanied with high rates of plate removals because of soft tissue irritations and discomfort. Meanwhile, low-profile plates precontoured for collateral double plating are available, and enable a muscular soft tissue coverage combined with angular stable fixation. The goal of the present study was to biomechanically compare posterior plating to collateral double plating for osteosynthesis of unstable osteoporotic fractures. Methods A comminuted displaced Mayo type II B fracture was created in 8 osteoporotic pairs of fresh frozen human cadaver elbows. They were pairwise angular stable fixed by either collateral double plates (DP) or a posterior plate (PP). Biomechanical testing was conducted as a pulling force to the triceps tendon in 90° of elbow flexion. Cyclical changes between 10 and 300 N were applied at 4 Hz for 50,000 cycles. Afterwards, maximum load was raised by 0.02 N/cycle until construct failure, which was defined as displacement > 2 mm. Besides failure cycles and failure loads, modes of failure were also analyzed. Results Following DP, a median endurance of 65,370 cycles (range: 2 – 83,121 cycles) was recorded, which showed no significant difference to PP with 69,311 cycles (range: 150 – 81,938 cycles) respectively (P = .263). Failure load showed comparable results as well with 601 N (range: 300 – 949 N) following DP and 663 N (range: 300 – 933 N) following PP respectively (P = .237). All PP constructs and 3 out of 8 DP constructs failed by proximal fragment cut out, whereas 5 out of 8 DP constructs failed by a bony triceps avulsion. Conclusion Angular stable double plating showed comparable biomechanical stability compared to posterior plating of unstable osteoporotic olecranon fractures under high cycle loading conditions. Failure due to bony triceps avulsion following DP requires further clinical and biomechanical investigation e.g. on suture augmentation or different screw configurations.