Abstract
Flatfoot (pes planus) is one of the most important physical examination items for military new recruits in Taiwan. Currently, the diagnosis of flatfoot is mainly based on radiographic examination of the calcaneal-fifth metatarsal (CA–MT5) angle, also known as the arch angle. However, manual measurement of the arch angle is time-consuming and often inconsistent between different examiners. In this study, seventy male military new recruits were studied. Lateral radiographic images of their right and left feet were obtained, and mutual information (MI) registration was used to automatically calculate the arch angle. Images of two critical bones, the calcaneus and the fifth metatarsal bone, were isolated from the lateral radiographs to form reference images, and were then compared with template images to calculate the arch angle. The result of this computer-calculated arch angle was compared with manual measurement results from two radiologists, which showed that our automatic arch angle measurement method had a high consistency. In addition, this method had a high accuracy of 97% and 96% as compared with the measurements of radiologists A and B, respectively. The findings indicated that our MI registration measurement method cannot only accurately measure the CA–MT5 angle, but also saves time and reduces human error. This method can increase the consistency of arch angle measurement and has potential clinical application for the diagnosis of flatfoot.
Highlights
The foot is an anatomically complex structure, consisting of 57 joints, 32 muscles and tendons, and 108 ligaments
The CA–MT5 angle of subject 31 was 162.0° as calculated by the mutual information (MI) registration algorithm; the manual measurements from radiologists A and B were both 162.6°
We have developed a method that uses lateral radiographic images and employs computerassisted MI registration to accurately calculate the CA-MT5 angle
Summary
The foot is an anatomically complex structure, consisting of 57 joints, 32 muscles and tendons, and 108 ligaments. These elements are responsible for controlling the movement of the foot. Due to the abnormal foot structure, patients with flatfoot often have problems regarding the even distribution of their body weight on the foot during movement, which may result in overloading of the bones or muscles. Due to a large number of individuals needing to be diagnosed every year, lateral x-ray imaging requires a large amount of manpower, and is often unreliable as a result of human error [11]
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