Alterated talar and navicular bone morphology is associated with pes planus deformity: a CT-scan study

We compared bone and articular morphology of the talus and navicular in clinically diagnosed flatfeet and evaluated their potential contribution to talo-navicular joint instability. We used CT images to develop 3D models of talus and navicular bones of 10 clinically diagnosed flatfeet and 15 non-flatfeet. We quantified their global bone dimensions, inclination and dimensions of the articular surfaces and their curvatures. Additionally, ratios of six talar and navicular dimensions were calculated. The values for these parameters were then compared between both groups. In flatfeet, the talar head faced more proximal and its width was larger compared to non-flatfeet. Also the navicular cup faced more proximal and its depth was significantly increased. Furthermore, we observed a more protruding talar head compared to the navicular cup in the control group with the articular surface depth being relatively larger for the navicular cups when compared to the talus in flatfeet. The ratio of the talar and navicular articular surface height was decreased in flatfeet, suggesting increased height of navicular cups relative to the articulating talar heads. Our results show that flatfoot deformity is associated with morphological changes of talar and navicular articular surfaces that can favor medial arch collapse and forefoot abduction.