A correlation study of Clarke angle and Chippaux-Smirak index with flatfoot deformity

BAO Bei-xi; ZHANG Jian-zhong

doi:10.3969/j.issn.2095-252X.2017.06.008

Abstract：Objective To investigate the relationship of Clarke angle and Chippaux-Smirak ( C-S ) index with the medial longitudinal arch and to explore the feasibility in the diagnose of flatfoot deformity by using the Clarke angle and C-S index. Methods A total of 162 subjects ( 308 feet ) were enrolled, whose weight-bearing anteroposterior and lateral X-ray films and Harris mat footprints of both feet were collected. On the weight-bearing lateral X-ray films, the talo-first metatarsal angle, calcaneal pitch angle, talus tilt angle and talocalcaneal angle were measured. On the Harris mat footprints, the Clarke angle and C-S index were measured. According to the talo-first metatarsal angle, the subjects were divided into 4 groups: normal arch group, mild flatfoot group, moderate flatfoot group and severe flatfoot group. The difference and correlation analyses were conducted between the medial longitudinal arch measurement results and the corresponding Clarke angle and C-S index. Results The Clarke angles were ( 42.79 ± 6.93 ) °, ( 31.73 ± 8.44 ) °, ( 21.07 ± 12.6 ) ° and ( 5.50 ± 1.19 ) ° in normal arch group, mild flatfoot group, moderate flatfoot group and severe flatfoot group respectively, and the differences among them were statistically significant ( F = 63.90, P = 0.000 ). The C-S indexes were 0.37 ± 0.05, 0.41 ± 0.05, 0.46 ± 0.11 and 0.69 ± 0.20 in normal arch group, mild flatfoot group, moderate flatfoot group and severe flatfoot group respectively, and the differences among them were statistically significant ( F = 39.70, P = 0.000 ). There was a negative correlation between the talo-first metatarsal angle and the Clarke angle, and the correlation coefficients were -0.646 for the left foot and -0.752 for the right foot. The talo-first metatarsal angle and the C-S index were positively correlated, and the correlation coefficients were 0.514 for the left foot and 0.575 for the right foot. There was a significant correlation between the medial longitudinal arch and the Clarke angle and C-S index. Conclusions The Clarke angle and C-S index are reliable indicators to measure and evaluate the medial longitudinal arch. The footprint measurement results can be helpful in the early diagnosis and grading of flatfeet, and further guide the secondary prevention of flatfeet.