Objectives: To investigate the biomechanical competence of locked plating augmented with supplemental intramedullary graft in comparison to conventional locked plate fixation in proximal humerus fractures (PHF).
Methods: Complex four-part PHFs were set in 30 artificial humeri assigned to 3 study groups (n = 10 in each group). Group 1 was characterized by loss of medial support, group 2 by simulated severe cancellous bone damage due to osteoporosis, and group 3 by combination of the 2 features. After locked plating, each specimen underwent nondestructive quasi-static mechanical testing in 25 degrees lateral angulation under axial loading between 150 and 400 N in 50-N increments, accompanied by consecutive anteroposterior x-ray imaging. Subsequently, an additional 3D-printed intramedullary graft was inserted into each specimen and all tests were repeated.
Results: Grafting resulted in significantly higher axial stiffness compared with no graft in groups 1 and 3 (P < 0.01) but not in group 2 (P = 0.12). Nongrafted specimens represented significantly higher stiffness in group 2 compared with groups 1 and 3 (P < 0.01), whereas no significant differences were detected among the 3 groups in the grafted state (P > 0.99). Varus deformation decreased significantly in each group after graft insertion (P ≤ 0.04). Nongrafted specimens in group 2 showed significantly lower varus deformation compared with groups 1 and 3 (P ≤ 0.04). No significant differences were registered among the 3 groups after grafting (P ≥ 0.65).
Conclusions: From a biomechanical perspective, locked plating augmented with intramedullary graft has the potential to increase significantly the stability against varus collapse in unstable PHFs when compared with conventional locked plate fixation.