Definition, quantification, and correction of translation deformities using long leg, frontal plane radiography

The surgical realignment of mechanical axis deviation is necessary to preve nt early joint degeneration. Modern types of external fixation systems allo w alignment of the mechanical axis to exact degrees. Predominately, these a re corrections of angulation deformities. In some cases, the analysis of th e mechanical axis deviation does not show any angulation deformity, but rat her a parallel staggering of the mechanical axis lines of a bone. Such para llel staggering of the mechanical axis lines is defined as a translation de formity of the bone. In combined deformities with angulation and translatio n, the center of deformity can be established proximal or distal to the lim it of the bone. In translation deformities, the realignment of the mechanic al axis requires a parallel restaggering made by a translation-osteotomy or by a counterangulated double osteotomy. In complex deformities with angula tion and translation, the translation requires separate corrective planning . In frontal plane radiographs of the standing leg, the components of an an gulation and translation can be established graphically or by simple trigon ometric formulas. The analysis and surgical procedure to realign translatio n deformities or a combination of translation and angulation deformities us ing an unilateral fixator device are discussed.