Abstract
Purpose of the study
We conducted a study to assess the accuracy of Spatial CAD software in computing the mounting and deformity parameters.
Methods and end results
We mounted a two-ring construct on a sawbone tibia and accurately measured the mounting parameters of this frame. Then we obtained three sets of x-rays – orthogonal without magnification marker, orthogonal with magnification marker placed at the level of the bone and non orthogonal views – and put these images through software and obtained mounting and deformity parameters.
Results were independently assessed and we found that the Spatial CAD™ software was accurate within 1 mm and 1 degree when orthogonal images with marker sphere placed at the bone level were used. Non-orthogonal images, with marker sphere, yielded accurate axial frame offset but other mounting parameters were at least 6 mm more than the actual measurements. Understandably angular measurements were different. In the third set of films we used frame hardware – Rancho Cube width (12 mm) as a calibrator. Since the cube was not in the same plane as the bone all measurements were way off actual measurements.
Conclusion
Spatial CAD™ software yields parameters within 1 mm of actual parameters when orthogonal images with a sphere marker placed at the level of bone are used for measurements. Non-orthogonal images yielded parameters that are +6 mm of actual parameters
