25dkou293 10.3205/25dkou293 urn:nbn:de:0183-25dkou2937 Meeting Abstract Barcik Barcik Jan J

AO Research Institute Davos, Davos Platz, Schweiz

author Ernst Ernst Manuela M

AO Research Institute Davos, Davos Platz, Schweiz

author Buchholz Buchholz Tim T

AO Research Institute Davos, Davos Platz, Schweiz

author Constant Constant Caroline C

AO Research Institute Davos, Davos Platz, Schweiz

author Mys Mys Karen K

AO Research Institute Davos, Davos Platz, Schweiz

author Zeiter Zeiter Stephan S

AO Research Institute Davos, Davos Platz, Schweiz

author Gueorgiuev Gueorgiuev Boyko B

AO Research Institute Davos, Davos Platz, Schweiz

author Windolf Windolf Markus M

AO Research Institute Davos, Davos Platz, Schweiz

author German Medical Science GMS Publishing House

Düsseldorf

610 20251031 engl This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 License. Dieser Artikel ist ein Open-Access-Artikel und steht unter den Lizenzbedingungen der Creative Commons Attribution 4.0 License (Namensnennung). M0634 293 Deutsche Gesellschaft für Orthopädie und Unfallchirurgie Deutsche Gesellschaft für Orthopädie und Orthopädische Chirurgie Deutsche Gesellschaft für Unfallchirurgie Berufsverband für Orthopädie und Unfallchirurgie Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2025) Grundlagenforschung | Trauma & Inflammation 2 Berlin 20251028 20251031 AB43-4488 TextObjectives and questions: Bone healing is influenced by the mechanical conditions within the fracture gap. This study aimed to examine the formation of fracture repair tissue in response to low to medium interfragmentary strain magnitudes using a large animal model with a monotonically increasing interfragmentary strain.Material and methods: Two partial osteotomies were performed on the tibia of ten sheep, creating a mobile wedge-shaped bone fragment. The bone was then instrumented with an active fixator that tilted the bone fragment, thus creating a gradient of interfragmentary strain in the osteotomy ranging from 2.5% to 25%. The sheep were randomly assigned to two groups, receiving either immediate loading (starting on the first day post-surgery) or delayed loading (beginning on the 22nd day post-surgery). Following euthanasia five weeks post-surgery, the tibiae were scanned using high-resolution computed tomography (CT). CT scans were then sliced at different strain levels, and for each two-dimensional slice, we assessed the area and density of the fracture repair tissue within the osteotomy and the radial span of the periosteal tissue.Results: The largest area and highest density of repair tissue within the osteotomy were found under the lowest strain conditions, and significantly decreased as strain increased (p≤0.015). In contrast, the radial span of periosteal tissue increased with strain (p<0.001) and was significantly larger in the immediate loading group (p<0.01).Discussion and conclusions: This study highlights the role of low but clinically relevant interfragmentary strain in bone healing. As strain increases, the formation of calcified repair tissue systematically shifts from within the fracture gap to predominantly external callus. Regardless of the strain magnitude, the entire evaluated strain window appears to support fracture consolidation, provided that the strain stimulus is applied during the early healing phase. Fixation strategies designed to promote low-strain stimulation may offer a safe and effective approach to enhancing bone healing. 0 0 0 0