Superiority of incremental trauma approach in experimental burst fracture studies

Objective. To compare the incremental and single trauma approaches in experimental spinal trauma production. Design. An in vitro study to produce experimental burst fractures in human spine specimens. Background. Experimental burst fractures have been produced by researchers for various purposes using two approaches: single and incremental traumas. Both the experimental trauma approaches use drop weight technique. There have been no studies to compare these two markedly different methods. Showing clear advantages of one approach over the other may significantly affect the design of future experimental trauma studies, not only of the spine. Methods. Using human spine specimens and drop weight technique, burst fractures of varying degrees of severity (defined by canal encroachment) were produced. Impact energies needed for the initial burst fracture and for the progression of the injury, i.e. increased canal encroachment, were studied using regression analyses. Results. Poor correlation was found between the impact energy and the canal encroachment of the initial burst fracture (R2=0.27). A much higher correlation was found when the initial burst fracture points (energy-encroachment) were initialized to zero values and only the progression of the injury was studied (R2=0.84, p < 0.001). The two regressions represent respectively single and incremental approaches. Conclusions. Incremental trauma approach was found to be superior to the single trauma approach, in producing a burst fracture with the desired canal encroachment in the human spine specimens, in spite of their inherent variability in size and strength of human vertebrae.