Does helical plating for proximal humeral shaft fractures benefit bone healing? - an in silico analysis in fracture healing.

Objectives: Helical plating is an established alternative to straight plating for humeral shaft fractures in order to prevent iatrogenic radial nerve damage. However, a previous biomechanical investigation indicated differences in fracture healing for helical plating due to a potential shift of interfragmentary movements compared to straight plating. Therefore, fracture healing simulations were performed to assess any differences in bone healing of helical vs. straight plating.

Methods: A systematic workflow for fracture healing analytics was created, covering essential steps of bone modelling, implant modelling, finite element modelling, fracture healing simulation and result analysis. Computational humerus models with an AO12C2 fracture and straight and helical osteosynthesis were created. An established fracture healing model was used to simulate callus formation over 112 days under physiological loading. The predicted tissue differentiation and interfragmentary movement (IFM) was tracked over the entire simulated healing course.

Results: Helical plating resulted in larger interfragmentary movements for compression and shear components, and in a greater proportion of near and far cortical movement. Vascularization and tissue formation were deferred, but cortical bridging was achieved.

Conclusions: Helical plating resulted in slightly deferred bone healing due to larger interfragmentary shear movements. Considering the advantage of helical plating in clinical context, a slightly deferred bone healing is justifiable.