Biomechanical analysis of push–pull principle versus traditional approach in locking plates for proximal humeral fracture treatment

Proximal humerus fractures are usually treated with locking plates, which could present recurrence, screw penetration, joint varization. The push–pull principle was introduced to prevent these risks and showed promising results; a dedicated design was then developed and this feasibility study aims to compare the biomechanical performances of such dedicated push–pull plate with the traditional locking plate using finite elements. The humerus geometry was obtained from Sawbone CT-scans; the geometries of a traditional locking plate and of the dedicated push–pull one were used. A fracture was added below the humeral head and the plates were virtually implanted. The wire pulling mechanism was simulated connecting the plate to the humeral head apex, considering two levels of tension. Three testing set-ups (axial, torsion and compression bending) were simulated. Stress distributions on bone, plate and screws were measured. Stress distribution on the distal humerus was similar for both plates. Stress distribution on the proximal humerus was more homogeneous for the push–pull model, showing less unloaded sections (up to 78