Radiographic Spatial Analysis Facilitates Deformity Correction

An innovative software application uses radiopaque markers to automate correction of limb deformities when using a spatial frame external fixator.

The AMDT Holdings (Collierville, TN, USA) SixFix system, indicated for use with the Smith & Nephew (London, United Kingdom) Taylor Spatial Frame, consists of deformity analysis and correction software and complementary instrumentation that are designed to reduce the time and effort involved in the manual input and analysis of deformity measurement values. These values, mostly derived from patient radiographs, are required in order to build a prescription plan consisting of daily adjustments to the spatial frame fixator over a period of weeks or months.

With the SixFix system, the surgeon attaches six proprietary radiopaque fiducial markers to the rings of a spatial frame external fixator, and inputs spatial frame characteristics--ring diameter, strut length, and axial rotation--into the SixFix software. The six radiopaque markers provide full descriptive positional data to the software that enable it to create a precise three-dimensional (3-D) replica of the frame and the deformity, regardless of how the radiographic images were taken, using sophisticated algorithms that correct radiographic imperfections, such as variable magnification and perspective distortion.

The data is then used to graphically map the deformity with line segments that define the axes of the bone fragments. The SixFix software also offers options to specify waypoints, customized treatment milestones that the surgeon uses to set the order and duration of each correction. AMDT Holdings is also in the development process of a proprietary hexapod fixation device that will enhance SixFix capabilities, according to Patrick Mullaney, President and CEO of AMDT Holdings.

“Of all the advantages offered by the SixFix software, time-savings is one benefit that I will realize right away. The current devices require a great deal of time and manual effort during my clinic hours to measure and record the data necessary to describe the frame and the deformity as represented by their radiographs,” said Stephen Frania, DPM, of Foot & Ankle Specialists of Ohio (Mentor, OH, USA). “I bring these patients in weekly to evaluate the progress of their correction. The time I save and the improved accuracy when using the SixFix software is significant over these repeat visits.”

Spatial frame fixators usually consist of two rings connected by six adjustable connectors called struts. This type of construct can also be referred to as a hexapod. Fixation elements connect the rings to bone fragments; small, simultaneous changes in the lengths of multiple struts alter the alignment of the bone fragments in relation to one another. A prescription consisting of daily adjustments is used to realign or correct the misalignments, resulting is a corrected deformity and a healed fracture.

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AMDT Holdings
Smith & Nephew