Plain radiographic evaluation of mid-tarsal mal-alignment in clubfoot

In order to identify which plain radiographic measurements are best suited to estimate mid-tarsal mal-alignment in clubfoot in children under three years of age, anteroposterior radiographs of 100 clubfeet were analyzed. The talo-first metatarsal (TMT) angle was measured, and the calcaneo-cuboid relationship was graded according to the method of Thometz and Simons. The calcaneo-cuboid relationship was also expressed as a ratio of the displacement of the cuboid to the radius of the cuboid. The intra-observer and inter-observer reproducibility of all the measurements were good. The mean TMT angle for Grade I Thometz and Simons mal-alignment was 41.35 degrees and 52.66 degrees for Grade II mal-alignment (P < 0.05). However, there was virtually no correlation between the cuboid displacement ratio and the TMT angle (r = 0.15). The results suggest that the TMT angle does not accurately reflect the degree of mid-tarsal mal-alignment in clubfoot, because it is a measure of both metatarsus varus and talo-navicular subluxation. The calcaneo-cuboid alignment indices measure the true subluxation at the mid-tarsal joint.