Biomechanical Stability of Single vs. Double Plating of Distal Humerus Fractures in Simulated Osteoporotic Bone

摘要

Background: Using low density foam (osteoporotic) bone models, we compared the stiffness and strength of locked plating between the standard double-plate orthogonal fixation of extra-articular distal humerus fractures and a single posterolateral plate or a single medial plate. The use of a single plate would confer several clinical advantages, and we hypothesized that there would be no significant difference between double plating and a single, posterolateral plate. This is believed to be an improvement over previous work that showed a difference when non-locking plates were tested. Methods: An extra-articular transverse fracture was created on eleven left foam humeri. Each specimen was tested in a random order under all three fixation conditions: double plating (90-90), a single posterolateral plate (PL), and a single medial plate (M). For each condition, stiffness was measured under simulated flexion, extension, and torsion loads. Strength was then tested by increasing the flexion load on each construct until failure occurred. Results: The double plated 90-90 configuration was significantly stiffer than both single plate constructs in flexion, extension and torsion (p<;0.01). The single PL plate was stiffer than the single M plate in extension and flexion (p<;0.01), but there was no significant difference between the two in torsion (p=0.73). Compared to the PL constructs, greater loads were required to cause failure in the 90-90 specimens (p<;0.01). Medial plated specimens twisted excessively during failure tests, but no frank failure occurred. Conclusions: 90-90 plating was biomechanically superior in fixing extra-articular, supracondylar fractures in osteoporotic bone models, likely due to increased symmetry eliminating bending of the plates. Failure strength is greater in the 90-90 constructs because they have more screws bearing the load in the proximal humerus. Future tests and analysis should focus on quantifying clinically relevant fixation as well as fracture site motion when the fractures are well reduced and compressed, in order to compare the possible clinical advantages of single-plating to the biomechanical superiority of double-plating.