ACCURACY OF IMAGING TECHNIQUES FOR TALAR NECK MALUNION

Abstract

Purpose: Achieving accurate imaging in talus neck fracture management is important. Patient outcome relies on the ability to achieve and maintain anatomic reduction. The ability to visualize the reduction postoperatively using plain radiographs or computed tomography (CT) is limited. The purpose of this study is to assess the ability of radiostereometric analysis (RSA) to detect changes in talus fracture fragment alignment using an in-vitro model. This will be compared to the use of plain radiographs and CT.

Methods: Eight cadaveric human lower extremities were used as talus fracture models. Each talus was removed from the specimen and an osteotomy was created. RSA beads were inserted into the fragments. Anatomical reduction was achieved with two 3.5 mm cortical screws. A set of plain radiographs and RSA films was obtained. The fragments were displaced in a combined varus and supination direction. The degree of displacement was measured with a Vernier caliper and the rotation measured with a protractor. The imaging sequence was repeated in addition to obtaining CT scans with three dimension reconstruction. The RSA measurements were interpreted in a blinded fashion by an experienced researcher. Two independent blinded observers measured the displacement and rotation with plain films and CT. The results from each radiographic measurements were compared using ANOVA method to the experimental values.

Results: The average difference between the RSA measurements and the experimental measurements was 5.9mm while the difference between CT scan measurements and experimental values was 2.4mm (p=0.003). The average difference in rotation was not statistically significant between the three groups.

Conclusions: CT scan provides the most accurate assessment of talar neck malunion. Unfortunately, RSA is not a viable imaging technique for assessing talar neck displacement.

Funding : Other Education Grant

Funding Parties : Lawson Health Research Institute