A Biomechanical Comparison of a Novel Expandable Photodynamic Intramedullary System to a Metal Plate and Screw System in Humerus and Femur Osteotomy Models

Abstract

The biomechanical performance of a locking compression plate system was compared 
to an intramedullary photodynamic bone stabilization system in a femur and humerus osteotomy model. The photodynamic bone stabilization system utilizes an angioplasty-like balloon that is introduced into the intramedullary canal of a fractured bone, filled with monomer 
that is then polymerized and hardened by visible blue light delivered through an optical fiber. 
This system has been in clinical use since 2010. Synthetic bones engineered to mimic the 
biomechanical properties of natural bone were cut to produce a 10 mm defect mid-shaft, and 
two groups of specimens were stabilized by either the compression plate or intramedullary 
photodynamic bone stabilization system. For each bone model, one locking compression plate 
system was used, and three different diameter intramedullary photodynamic bone stabilization implants were used. Experimental groups were tested for stiffness, peak load, yield load, 
peak displacement and yield displacement when a load was applied. Additional samples per 
experimental group were tested for long-term dynamic stability by cyclically loading until 
failure. It was found that in all biomechanical parameters measured, the 17 mm intramedullary 
photodynamic bone stabilization system exceeded the mechanical strength and durability of 
the locking compression plate system in the femur osteotomy model. It was found that in all 
biomechanical parameters measured, the 15 mm intramedullary photodynamic bone stabilization system performed equivalently or exceeded the mechanical strength and durability of the 
locking compression plate system. This testing combined with long-term clinical use, and in 
vivo data from a large animal model, suggest that femur fixation by an intramedullary photodynamic bone stabilization system will provide equivalent biomechanical properties to a locking 
compression plate once implanted.