W. Eger, P. Kluger, L. Claes, H.-J. Wilke


February 1999, Volume 8, Issue 1, pp 61 - 69 Original article Read Full Article 10.1007/s005860050128

First Online: 17 February 1999

The Kluger internal fixator, with its artificial fulcrum outside the operative site, had to be extended for multisegmental use. Three different prototypes, called Central Bar (CB), Double Bar I (DB I) and Double Bar II (DB II) were designed, which were fully compatible with the existing reduction system. To evaluate the ability of these newly developed systems to provide primary stability in a destabilized spine, their stiffness characteristics and stabilizing effects were investigated in multidirectional biomechanical stability tests and compared with those of the clinically well-known Cotrel-Dubousset (CD) system. The investigations were performed on a spine tester using freshly prepared calf spines. The model tested was that of an intact straight spine followed by a defined three-column lesion simulating the most destabilizing type of injury. Pure moments of up to 7.5 Nm were continuously applied to the top of each specimen in flexion/extension, left/right axial rotation, and left/right lateral bending. Segmental motion was measured using a three-dimensional goniometric linkage system. Range of motion and stiffness within the neutral zone were calculated from obtained load-displacement curves. The DB II attained 112.5% (P = 0.26) of the absolute stiffness of the CD system in flexion and enhanced its stability in extension by up to 144.3% (P = 0.004). In axial rotation of the completely destabilized spine, this system achieved 183.3% of the stiffness of the CD system (P


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