Purpose
We performed a biomechanical analysis using the finite element method to assess the
effects of plate length and the number of screws on construct stiffness, stress distribution,
and fracture displacement in the fixation of type A2 distal humerus fractures.
Methods
A 3-dimensional humerus model was constructed using computed tomography of a healthy
man. After creating a 2-mm extra-articular fracture gap, orthogonal double-plate fixation
was performed with an incremental increase in plate length and the number of screws,
creating 17 fixation models. Four screws were placed in each plate’s distal segment,
and the number of screws was increased incrementally in the segment proximal to the
fracture, starting from 2 in the medial (M) and 2 in the lateral (L) plate (M2∗L2).
Results
The fifth screw proximal to the fracture in the lateral plate (L5) played an essential
role in increasing stiffness under bending, axial, and torsional forces surpassing
the intact bone, which may have been due to the bypassing of the stress riser area.
Minimum construct stiffness was created when 5 (M3∗L2) screws were inserted into the
proximal segment. For bending forces, the M4∗L2 construct was stronger than M3∗L3
(total 6 proximal screws), and M5∗L3 was stronger than M4∗L4 (total 8 proximal screws),
showing higher stiffness when the plates ended at different levels. The M4∗L2 construct
(6 screws) had stiffness comparable with M4∗L3, M4∗L4, and M5∗L4 during bending, showing
comparable stiffness with the least instrumentation density.
Conclusion
Our findings suggested M3∗L5 as the optimum and M3∗L2 as the minimum construct to
resist all bending, axial and torsional forces.
Clinical relevance
Applying the results may improve surgical techniques, decrease the rate of complications,
including fixation failure and nerve injury, and optimize the time of surgery. Moreover,
hardware removal is less cumbersome with fewer screws.
Key words
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Article info
Publication history
Published online: August 31, 2021
Accepted:
July 9,
2021
Received:
July 15,
2020
Footnotes
No benefits in any form have been received or will be received related directly or indirectly to the subject of this article.
Identification
Copyright
© 2022 by the American Society for Surgery of the Hand. All rights reserved.
