OTA 2006 Posters

Scientific Poster #69 Basic Science

Imaging Techniques for Talar Neck Malunion:
A Comparison of Radiographs, Computed Tomography, and Radiostereometric Analysis
Gladys Chan, MD; David Sanders, MD, MSc, FRCSC (a-Synthes Canada, a-Lawson Health Research Institute); XunHua Yuan, PhD (n);
Kevin Willits, MD, MSc, FRCSC (n); Richard Jenkinson, MD (n);
Victoria Hospital, London Health Sciences Centre, London, Ontario, Canada

Purpose: Outcome following talar neck fracture relies on the ability to achieve and maintain an anatomic reduction. Malunion, however, is difficult to detect and measure using plain radiographs. The purpose of this study was to compare the accuracy of radiostereometric analysis (RSA), computed tomography (CT), and plain radiographs (X-ray) in an in vitro model of talar neck malunion.

Methods: Eight cadaveric tali were osteotomized across the talar neck. RSA beads were inserted into the fragments. The fracture fragments were reduced anatomically and stabilized with two cortical screws. X-rays (anteroposterior, lateral, and Canale views) and orthogonal RSA radiographs were obtained. The fragments were then displaced into varus and supination, and restabilized to simulate a talar neck malunion. Displacement and rotation were measured directly. X-rays and RSA were repeated, and CT scans were performed including 2-mm axial and reconstructed views. RSA measurements were interpreted by a blinded experienced RSA analyst. Two blinded orthopaedic surgeons assessed displacement and rotation with plain films and CT. Displacement and rotation using each imaging technique were compared to the directly measured values using ANOVA.

Results: CT was more accurate than RSA or X-rays (P <0.05) in measuring displacement. The difference between imaging and measured values was 5.9 mm ± 2.0 mm for RSA, 5.0 mm ± 3.0 mm for X-ray, and 2.4 mm ± 4.8 mm for CT (P < 0.05). The accuracy of rotational measurement did not differ between the three imaging techniques (P >0.10).

Conclusion/Significance: CT scan was the most accurate measurement technique to assess talar neck malunion. RSA imaging was less accurate, in part due to insufficient bead spacing. Measurement of malunion after talar neck fractures is inaccurate using plain radiographs. CT imaging offers improved accuracy and may be beneficial for malunion assessment and preoperative planning.

If noted, the author indicates something of value received. The codes are identified as a-research or institutional support; b-miscellaneous funding; c-royalties; d-stock options; e-consultant or employee; n-no conflicts disclosed, and *disclosure not available at time of printing.
· The FDA has not cleared this drug and/or medical device for the use described in this presentation (i.e., the drug or medical device is being discussed for an "off label" use). · · FDA information not available at time of printing.