Ilizarov Technique for Simulataneous correction of Angular and Rotational Deformities : The Use of Inclined Hinges with Universal Joints

Lee, Duk Yong; Choi, In Ho; Chung, Chin Youb; Cho, Tae Joon

Abstract

llizarov technique is versatile enough to afford simultaneous or staged correction of complex deformities of the long bone. According to the conventional llizarov method, angulation, shortening, rotation and translation deformities are corrected sequentially in that order. Appropriate placement of the hinges enables simultaneous correction of angulation, shortening along with translation. However, when additional rotational correction is needed, major modification of the frame is mandatory and moreover, undesirable shearing force ensues on the newly formed regenerate bone. Inclined hinges composed of universal joints in llizarov frame has inherent potentiality to provide simultaneous correction of the angular and rotational deformities. The authors geometrically analyzed the inclined hinge technique. Table and graph were presented to determine the exact values of surgical parameters for a given deformity. When the hinge axis was displaced from the center of deformity maintaining its orientation and inclination, simultaneous correction of translation and/or shortening in addition to angulation and rotation occurred, which was confirmed by computer graphic simulation study; 1. An inclined hinge axis displaced along the longitudinal bisector line resulted in translation along the direction perpendicular to the hinge axis projected on the horizontal plane. 2. An inclined hinge axis displaced along the transverse bisector line resulted in translation along the direction of the hinge axis projected on the horizontal plane as well as lengthening or shortening. Therefore, judicious placement of inclined hinge axis enables, theoretically, simultaneous correction of angular, rotational, translational deformities along with shortening in particular cases. In practical application, the inclined hinge technique helps lessen the number of subsequent frame modifications or at least reduce the amount of residual deformities to be corrected by next step.