Abstract
Aims: The purpose of this study was to clarify how the mechanical characteristics of the lengthened bone changes with time by means of the analyses using the CT based finite element method. Methods: CT images were obtained from the bilateral tibiae of five patients who had undergone unilateral tibia. The average time interval from completion of lengthening to CT scanning was 30 months. There were two patients had CT examinations twice. The analyses were made using the Mechanical Finder®(Mitsubishi Space Software, Osaka, Japan). 3-D finite element models were made from axial CT images of the whole tibiae. The models were 3mm tetrahedron elements for a cancellous bone and 3 nodal-points shell elements with a thickness of 0.3 mm for a cortical bone. The uni-axial compressive load was applied on the tibial plateau, while the distal part of the tibia was fully restrained. The elastic moduli at the middle of the lengthened bones and the maximum principal strains were calculated using the elastic analysis. Results: The elastic moduli of the lengthened bones were significantly smaller than those of the contra-lateral bones, while the maximum principal strains of the lengthened bones tended to be larger. The ratios of the elastic modulus disparity between the lengthened bone and the paired contra-lateral bone to the elastic modulus of the contra-lateral bone decreased significantly with time. Likewise, the ratios of the maximum principal strains calculated as above decreased identically. Conclusions: The results indicated that the stiffness of the lengthened bone got closer to that of the contra-lateral with time, which means the lengthened bones were in the process of modeling during these follow up time intervals.
Theses abstracts were prepared by Professor Dr. Frantz Langlais. Correspondence should be addressed to him at EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.
