Angular stable intramedullary nail versus locking plate fixation of osteoporotic surgical neck proximal humerus fractures: A biomechanical comparison.

Abstract

Our study's purpose was to compare biomechanical performances of a proximal humerus locking plate (PHLP) with an antegrade intramedullary nail (IMN) in an osteoporotic two-part surgical neck proximal humerus fracture model. Simulated fractures were made through the surgical neck of synthetic osteoporotic humeri. One group had identical transverse fractures instrumented with a PHLP with seven screws (PHLP-7; <i>n</i> = 4), a PHLP with nine screws (PHLP-9; <i>n</i> = 2), or an IMN (<i>n</i> = 4). Each underwent pre-fatigue testing, an identical fatigue protocol, and post-fatigue testing. A second high oblique fracture line was tested identically with PHLP-9 (<i>n</i> = 4) and IMN (<i>n</i> = 4) constructs. Statistical analyses of transverse specimen pre-fatigue stiffness revealed that the PHLP-7 and PHLP-9 were stiffer in anteroposterior bending and torsion compared to the IMN. There was no difference between the three constructs in varus-valgus bending or compression. Post-fatigue stiffness comparisons revealed no difference between the three constructs. For the oblique fracture, pre-fatigue differences were found with the IMN stiffer in varus-valgus bending and the PHLP-9 stiffer in torsion. The biomechanical performance of an angular-stable proximal humeral nail design was comparable, especially following fatigue, to locked plate/screw constructs in a synthetic osteoporotic two-part surgical neck proximal humerus fracture model.