Calculation and Correction of Secondary Translation Deformities and Secondary Length Deformities

Abstract

External fixation correction of angular deformities leads to secondary translation deformities when occurring around an axis located proximal or distal to the center of rotation of angulation (CORA); secondary length deformities result when correction occurs around an axis concave or convex to the CORA. With circular fixation, the hinge axis can be matched to the CORA. With monolateral fixation, the level of the hinge/angulator is not easily controlled. Axis of correction of angulation can be plotted graphically and secondary deformities calculated trigonometrically. Location of the hinge/angulator can be accurately planned and adjustments incorporated to compensate for expected secondary deformities.

Radiographic Measurement of the Proximal and Distal Mechanical Joint Angles in the Canine Tibia

“…Knowledge of the mechanical or anatomic axis and their relationship with adjoining joints is essential in angular limb deformity quantification using the Center of Rotation of Angulation methodology recently described and used in both humans and dogs. 8,19,20 Angles in this study were named in accordance with nomenclature developed in human literature and recently applied to the canine antebrachium. 8,21 The mechanical axis of a long bone, in any plane, is determined to be the straight line connecting points at the center of the proximal and distal joints of that long bone.…”

Thoracic Limb Alignment in Healthy Labrador Retrievers: Evaluation of Standing Versus Recumbent Frontal Plane Radiography

“…In people, diagnosis, planning, and surgical treatment of medial compartment syndrome is often performed using the center of rotation of angulation (CORA) method. This method uses joint reference lines, mechanical or anatomic axes of individual long bones, and the resulting limb alignment values to identify the location, plane, and magnitude of an angular limb deformity . The CORA method can be used with a variety of imaging modalities, but is most often applied to standing (weight‐bearing) radiographs .…”

“…The mechanical axis deviation (MAD), or deviation of the center of the knee from the weight‐bearing axis of the entire limb, the distal femoral joint reference angle (mLDFA), and proximal tibial joint reference angle (MPTA) are examples of CORA‐generated limb alignment values . These patient‐specific limb alignment values are used to make surgical treatment recommendations and to plan surgical corrections …”

Limb Angular Deformity Correction Using Dyna-ATC: Surgical Technique, Calculation Method, and Clinical Outcome

“…The ACA, CORA, and secondary displacement are not new concepts when the ACA is not on the CORA. 17 , 18 , 20 Many previous studies adequately described the reasons of why the secondary displacement develops and how to avoid creating the secondary deformities. They also provided the methods to calculate the rate of angular correction.…”