PSI - Issue 2_A

M. Karanika et al. / Procedia Structural Integrity 2 (2016) 1252–1259 1259 8 M. Karanika, D. Georgiou, S. Darmanis, Α . Papadogoulas, E.D. Pasiou, S.K. Kourkoulis / Structural Integrity Procedia 00 (2016) 000 – 000

ment of all the fractures of all specimens of a given class (minimum maximorum), and the maximum of the minimum relative displacement of all fractures of all specimens of a given class (maximum minimorum) etc. It was extremely encouraging to observe that all alternative criteria, based on a “homogenized” value of the relative displacement of the fractures’ lips, resulted to the same conclusion, concerning the efficiency of the fixation techniques used (Kour koulis et al., 2015; Georgiou and Karanika, 2016). To support this conclusion the maximum minimorum of the relative displacement of all fractures of all specimens of a given class is plotted in Fig.9b for all five classes. The similarity with Fig.9a, concerning the superiority of the fixation techniques of the IV and V classes is obvious. It is to be mentioned at this point that any conclusion drawn based on the results of an experimental protocol with five specimens per class is rather risky. Indeed the statistical analysis of the results is characterized by marginal sta tistical significance. In this direction and before definite conclusions are drawn the authors of this study believe that additional experiments should be implemented (with specimens of identical material properties). In spite of the above limitation the conclusions drawn and the quantitative data presented here could be valuable in the direction of validating and calibrating numerical models which could be used for detailed parametric analysis of the (quite a few) factors influencing the overall mechanical response of the fixated pelvis after “ B2 T-type ” fracture. Recapitulating, and besides the difficulties in reaching a definite clinical suggestion, it can be definitely stated that the 3D-DIC technique was proven very effective for the study of fixation techniques of pelvic fractures. Its main advantage is that it allows the “construction” of any number of “virtual gauges” over the surface of the specimen tested, by considering two arbitrary points and following their spatial displacement (in three dimensions). In this way it is possible to determine the change of the distance along any fracture line or determine the strain field at any region of the specimen independently of its complex geometry. What is, also, important is that the choice of these “virtual gauges” may be realized either before the test or “post mortem”, i.e. a fter the test is completed or during the ela boration of results. In addition to the estimation of the “ normal opening” (or perhaps “closure”) of the fracture (i.e. the change of the distance of the fractured parts normally to the fracture plane) 3D-DIC offers the possibility to determine the relative sliding of the fractured parts within the fracture plane, which is not possible using traditional sensing techniques. This feature is very efficient when geometrically complex fracture lines (or fractures with more than one fracture lines) are studied (like the ones considered here), since in such cases it is quite possible that while one of the lines is “opening” normally to the fracture plane a second fracture exhibits a kind of shear displacement. Equally important is the fact that 3D-DIC permits isolation of the rigid body displacements and rigid body rotations of the specimen as a whole body, providing the pure relative displacements of the fractured parts. References Culemann, U., Holstein, J. H., Köhler , D., Tzioupis, C.C., Pizanis, A., Tosounidis, G., Burkhardt, M., Pohlemann, T., 2010. Different stabilisation techniques for typical acetabular fractures in the elderly - A biomechanical assessment. Injury, 41(4), 405-410. Georgiou, D., Karanika, M., 2016. Using Digital Image Correlation for the biomechanical assessment of pelvic fractures (in Greek), Diploma Thesis, Supervisor: Kourkoulis, S.K., National Technical University of Athens, School of Applied Mathematical and Physical Sciences, Department of Mechanics, Athens, Greece. Letournel, E., Judet, R., 1993. Fractures of the acetabulum, 2 nd ed. Springer-Verlag, Heidelberg, Germany. Kourkoulis, S.K., Darmanis, S., Papadogoulas, A., Georgiou, D., Karanika, M., Pasiou, E.D., 2015. A study of fixation techniques of pelvic fractures using DIC (in Greek). In Proceedings of the 8 th National Conference of the Hellenic Society for Non Destructive Testing, p. 74, May 8-9, Athens, Greece. Liu, H., Li, L., Wu, X., Xu, H., Zhang, R., 2015. Biomechanical research of different internal fixations using locking reconstruction plate for acetabular transverse fracture. Chinese Journal of Reparative and Reconstructive Surgery, 29(9), 1084-1087. Mehin, R., Jones, B., Broekhuyse, H., 2009. A biomechanical study of conventional acetabular internal fracture fixation versus locking plate fixation. Canadian Journal of Surgery, 52(3), 221. Wang, L., Wu, X., Qi, W., Wang, Y., He, Q., Xu, F., Liu, H., 2015. Biomechanical comparative study on four internal fixations for acetabular fractures in quadrilateral area. Chinese Journal of Reparative and Reconstructive Surgery, 29(10), 1235-1239. Zhang, Y., Tang, Y., Wang, P., Zhao, X., Xu, S., Zhang, C., 2013. Biomechanical comparison of different stabilization constructs for unstable posterior wall fractures of acetabulum. A Cadaveric Study. PloS one, 8(12), e82993.