• Johannes Christof Hopf, Tobias Eckhard Nowak, Dorothea Mehler, Charlotte Arand, Dominik Gruszka, and Pol Maria Rommens.
• Department of Orthopedics and Traumatology, University Medical Center, Langenbeckstraße 1, 55131, Mainz, Germany. joh.hopf@gmail.com.
• Eur J Trauma Emerg Surg. 2021 Jun 1; 47 (3): 795-802.

PurposeProximal ulna fractures are common injuries and frequently treated with angular stable plating. This surgical option shows good functional results. Relevant drawbacks such as large soft tissue exposure, compromised blood supply of fracture fragments and disturbing osteosynthetic material are described. The aim of this study was to compare a new locked proximal ulna nail with angular stable plating in a biomechanical testing setup for extraarticular proximal ulna fractures.MethodsTen pairs of sawbones with a Jupiter type IIB proximal ulna fracture (OTA 2U1A3.1) were tested after osteosynthesis with the mentioned implants in a servo-pneumatic testing machine. The testing setup simulates physiological joint motion (0°-90°) under cyclic loading (30-300 N). Primary stability and loosening of both constructs were quantified using micromotion video-analysis after 608 test cycles.ResultsThe micromotion analysis showed significantly higher primary stability of the locked nail (0.29 ± 0.13 mm) compared to the angular stable plate (0.97 ± 0.30 mm, p < 0.001). Both implants showed a low amount of loosening after completion of the test cycles. The construct with the locked nail (0.08 ± 0.06 mm) showed significantly lower dislocation of the fragments measured at the anterior cortex (plate 0.24 ± 0.13 mm, p < 0.001).ConclusionNailing of proximal ulna fractures shows significantly higher primary stability and lower loosening compared to angular stable plating in our testing setup.

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