Three-dimensional morphological characteristics measurement of ankle joint based on computed tomography image post-processing

As precise positioning of ankle radiography is not possible, quantitative measurement of all syndesmotic parameters on repeated ankle X-ray films may be of little value. The purpose of this study was to provide a set of scientific and objective evaluation criteria for assessing the quality of ankle fracture reduction accurately and reliably by an intelligent combining three-dimensional （3-D） computed tomography （CT） measurement model. Methods From June 2008 to March 2011, all the thin-slice CT images of 100 cases （50 males and 50 females） with normal ankle joint scanned by 16-slice spiral CT were collected. Two-dimensional （2-D） and 3-D images of ankle joints were generated by using multiple planar reconstruction （MPR） and surface shaded display （SSD） respectively. The relevant parameters about bone structures and their relationship were measured and analyzed based on 3-D topological narrow division technique and 3-D measurement techniques combining essential elements of point, line and surface. Results In this study, the mean distance from lateral malleolus tip to talocrural articular surface, the tip of medial malleolus anterior colliculus to talocrural articular surface and lateral malleolus tip to the tip of medial malleolus anterior colliculus were （22.83±1.12） mm, （12.84±1.09） mm, and （61.18±2.03） mm respectively in male group, and （20.16±1.00） mm, （10.30±1.05） mm and （53.00±1.40） mm respectively in female group. The above three parameters were correlated with gender, height and weight （P 〈0.05）. However, the mean perpendicular distance from lateral malleolus tip to the plane through the tip of medial malleolus anterior colliculus, the talocrural angle, later clear space, medial clear space, and the superior clear space were （9.93±0.29） mm, （10.01±0.38）°, （1.94±0.16） mm, （2.78±0.19） mm, and （3.14±0.15） mm respectively in 100 cases, were not significance correlated with gender, height and weight （P 〉0.05）. Conclusions This study could provide a certain amount of relevant data for the standard of injured ankle anatomical reduction and the second surgery planning after malunion. The methods of measurement are reliable, reproducible, and easy to apply in practice.