Natural Value of Böhler's Angle in Normal Chinese Population

To determine the value of Böhler's angle (BA) in a group of Chinese people, analyze possible factors that influence it, and compare BA with that in previous literature.

A total of 143 cases, aged from 4 to 79 years, were enrolled in the study, including 64 males and 79 females (79 left feet and 64 right feet). Radiographs were independently measured by six observers. Age, sex, body side, subtalar joint congruity (STJC), and X-beam obliquity (TT) were recorded. The database was assessed based on intraobserver agreement, data distribution, the randomness of case selection, and the ratio equality of binomial variables. Then, the normal value of BA was established, as well as the correlation between BA and other parameters.

In the present study, the interobserver reliability of BA, STJC, and TT was excellent. The BA data revealed a normal distribution, and the randomness of case selection was verified for age, sex, and body side. The ratio of sex and body side was equal. Homogeneity of variance was observed when comparing the value of BA between different groups. The value of BA was 31.6° ± 5.19° (range, 20.08°-47.19°), which was not related to age, sex, body side, and minor X-ray beam obliquity. BA application was not suitable for individuals younger than 10 years. The mean value of BA in this study was not identical with those in previous reports. This demonstrated that BA varies for different races.

For Chinese people, 30° to 33° is recommended as the target value of BA for calcaneal fracture reduction, except in children under 10 years of age.