Stress Distribution and Construct Stability in an Experimental Cervical Open-Door Laminoplasty Model: —Three-dimensional Finite Element Analysis—@@@—有限要素解析法による検討—

Abstract

Background:Open-door cervical laminoplasty requires devices such as stay sutures(SS), laminar spacers(LS), and titanium mini-plates(TM)to keep the elevated lamina open. However, the significance and differences in the effects of each of these devices remain unclear. This study aimed at investigating the role of these devices, using a 3-dimensional finite element(FE)model. Methods:An FE bone model of the fifth cervical vertebra was constructed. Its lamina was elevated by guttering at the hinge site, simulating an open-door technique(G model). SS, LS, and TM were added to the G model, simulating laminoplasty with SS(SS model), LS(LS model), and TM (TM model), respectively. Compression loading force was applied to the elevated lamina in 2 directions of the horizontal plane, and the stress distribution response was analyzed. Results:The peak Mises stress which integrates the stresses in multiple directions into a unified vector was concentrated at the hinge region in the G and SS model. In the LS and TM model, the peak Mises stresses were observed in the connecting regions between the LS and the lateral mass, and the TM and the elevated lamina, respectively. The Mises stress in the hinge region was minimal in the LS model. Moreover, the bony peak Mises stress and the maximum deformation were minimal in the LS model. Conclusions:This stress distribution study clearly demonstrated that the placement of artificial implants such as LS and TM determined the stress concentration at the hinge region during laminoplasty with SS. The results of deformation studies showed that LS was best for stabilizing the elevated lamina. Based on this analysis, we suppose that the use of LS for stabilization of the hinge region might yield favorable results over other devices in open-door laminoplasty. (Received:September 27, 2012;accepted:March 6, 2013)