THE RELATIONSHIP OF ANGULATION TO TRANSLATION IN FRACTURE DEFORMITIES

We measured both angulation and translation on anteroposterior and lateral roentgenograms of 100 fixed post-traumatic deformities (either malunions or stiff [hypertrophic] non-unions) of long bones. We used trigonometric formulae to calculate the true planes and actual magnitude of both the angulation and the transverse translation of each deformity. We found that the planes of angulation and translation for each osseous deformity were rotated 43 +/- 25 degrees (mean and standard deviation) with respect to each other; in fact, we found almost as many instances in which the planes of angulation and translation of the fragments were within 10 degrees of perpendicular to each other as we did instances in which the angulation and translation were within 10 degrees of being in the same plane. Only seven angular deformities and six translational deformities occurred along either the sagittal or the coronal plane; the remaining deformities were in planes that were oblique to the standard reference planes. CLINICAL RELEVANCE: Angulation and translation should be considered as separate deformities, each in its own plane, when correction of a malunion or a hypertrophic non-union is planned. The hinges and translation assemblies employed in gradual correction techniques that use external fixation should thus be oriented in different planes. When an acute closing or opening-wedge technique is used in combination with internal fixation, a surgeon may need to plan cuts in the bone that allow for correction of both angular and translational deformities in separate planes. Since so few deformities angulated along the standard reference planes, we propose elimination of the terms varus, valgus, recurvatum, and antecurvatum from the description of fracture deformities and substitution with terminology that describes the true direction of the apex of the deformity and the actual magnitude of the angle of the deformity.