Abstract
In proximal humeral fracture except AO classification 11A1, fixations with a locking plate and nails are recommended. We performed mechanical tests to investigate whether retrograde intramedullary nailing has fixation stability comparable to those of anterograde intramedullary nailing and locking plate which achieve clinically favorable outcomes. In retrograde intramedullary nailing, a nail entry point is made in the diaphysis, for which reduction of stiffness of the humerus is of concern. Thus, we investigated the influence of a nail entry point made in the diaphysis on humeral strength. Retrograde intramedullary nailing had fixation stability against bending and a force loaded in the rotation direction comparable to those of anterograde intramedullary nail and locking plate. Displacement by the main external force loaded on the humerus, compressive load, was less than half in the bone fixed by retrograde intramedullary nailing compared with that in the bone fixed with a locking plate, showing favorable fixation stability. It was clarified that stiffness of the humerus against rotation and a load in the compression direction is not reduced by a nail entry point made by retrograde intramedullary nailing.
Highlights
Fracture collapses continuity of the bone and results in morbid deformation, loss of supporting function, and pain
The humeral stiffness calculated from the relationship between the load added and displacement in the bending test was 11.9 ± 1.18 and 16.4 ± 0.87 N/mm in the groups with and without a nail entry point, respectively, showing a significant difference between the two groups, and the stiffness was 25% lower in the presence of a nail entry point compared with that in the absence of a nail entry point (Figure 6(a))
The humeral stiffness calculated from the relationship between the load added and displacement was 243 ± 30.0 and 246 ± 22.7 N/mm in the groups with and without a nail entry point, respectively, showing no significant difference, and the stiffness was 1% reduced in the presence of a nail entry point compared with that in the absence of a nail entry point (Figure 6(c))
Summary
Fracture collapses continuity of the bone and results in morbid deformation, loss of supporting function, and pain. The bone function can be restored and pain is reduced by surgical stabilization of fracture. The final goal of internal fixation of fracture is to completely restore the bone function as quickly as possible. The incidence of AO classification 11A2.1 proximal humeral fracture is high in the elderly. According to a large-scale non-randomized observational study, reduction of the function and non-union were noted in elderly patients with conservatively treated AO classification 11A2.1 fracture [2], whereas patients treated with internal fixation returned to daily life. For internal fixation of almost all of proximal humeral fracture, fixations with a locking plate and nails are recommended [3]
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