• Paul C Siffri, Richard D Peindl, Edward R Coley, James Norton, Patrick M Connor, and James F Kellam.
• Department of Orthopaedic Surgery, Carolinas Medical Center, Charlotte, NC 28232, USA.
• J Orthop Trauma. 2006 Sep 1; 20 (8): 547-54.

ObjectiveTo compare the mechanical stability of a fixed-angle blade plate with that of a locking plate in a cadaveric proximal humerus fracture-fixation model subjected to cyclic loading. A secondary objective was to evaluate whether the use of synthetic humerus specimens would replicate significant differences found during cadaveric tests.DesignMechanical evaluation of constructs in bending and torsion.SettingBiomechanical laboratory in an academic medical center.MethodsSimulated humeral neck fractures (Orthopaedic Trauma Association (OTA) classification 11A3), in matched-pair cadaveric and synthetic specimens underwent fixation using either a 3.5-mm, 90-degree cannulated LC-Angled Blade Plate or a 3.5-mm LCP Proximal Humerus Locking Plate. Cadaveric specimen constructs were cyclically loaded in bending and torsion; synthetic specimens were tested in torsion.Main Outcome MeasureHumeral shaft-bending displacements and angular rotations for respective cyclic bending loads and axial torques were recorded and compared at repeated cyclic intervals to evaluate construct loosening.ResultsLocking-plate constructs exhibited significantly less loosening than blade-plate constructs for torsional loading in cadaveric specimens (P = 0.036). The two types of constructs performed similarly for torsional loading in synthetic specimens (P = 0.100). Under cyclic, closed-bending load conditions in which the plates served as tension members, both types of constructs performed similarly in cadaveric specimens (P = 0.079).ConclusionsFor simulated humeral neck fractures subjected to cyclic loading, locking-plate constructs demonstrated significantly greater torsional stability and similar bending stability to blade plates in a cadaveric specimen model. In contrast, these same constructs performed similarly with torsional loading when using synthetic humerus specimens. These results indicate potential advantages for locking-plate fixation. They also indicate that the synthetic specimens tested may not be appropriate for evaluating fixation stability in the humeral head, where cancellous bone fixation predominates.

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