Locked plate fixation and intramedullary nailing for proximal humerus fractures: a biomechanical evaluation.
BACKGROUND
Internal fixation of proximal humeral fractures is associated with a considerable secondary malalignment rate. Fixed-angle implants have been suggested to increase the stability of fixation.


METHODS
The biomechanical properties of four different implants were tested. These included an internal fixator with semi-elastic properties (reference), the Synthes T-plate, a locked plate with rigid properties and a spiral blade locked intramedullary nail (PHN). These implants were assessed in twenty-four osteotomized pairs of human cadaveric humeri. Specimens were subjected to two-hundred cycles of axial loading and torque followed by load to failure.


RESULTS
The PHN had greater axial stiffness than the reference and the T-plate. During torque, all implants were stiffer than the reference. During cyclic loading, there were no differences between the T-plate and the reference. Both the rigid internal fixator and the PHN had less irreversible deformation than the reference. Both implants resisted higher loads before failure.


CONCLUSIONS
This study showed that the proximal humeral nail and the rigid internal fixator are stronger than the semi-elastic locked plate and the Synthes T-plate for unstable subcapital proximal humeral fractures.
Department of Trauma Surgery, Johannes Gutenberg-University, Langenbeckstrasse 1, D-55101 Mainz, Germany. Hessmann@unfall.klinik.uni-mainz.de
Martin Henri
MH
Hessmann
Werner Sternstein Matthias
WS
Hansen
Frank
F
Krummenauer
Tamara Fischer
TF
Pol
Pol  Maria
P
Rommens
D001696:Biomechanical Phenomena; D001858:Bone Nails; D001860:Bone Plates; D004867:Equipment Design; D005594:Fracture Fixation, Intramedullary; D006801:Humans; D016268:Internal Fixators; D012784:Shoulder Fractures / Q000503:physiopathology / Q000601:surgery*