Material and Methods: The study is made on 10 cadaver first metatarsals. The metatarsals are fixed to a device. The metatarsal inclination and pronation of the metatarsal can be changed by this device. 15-30-45 degrees inclination and 0-10-20 degrees pronation are applied to the metatarsals. After applying radio opaque putty to the medial and lateral articular edges; metatarsal dorsal diaphysial ridge, the x-ray and digital images are taken at different degrees of inclination and pronation. The measurement of PASA is done by graphic software on computer. The statistical analysis is performed by paired sample T-test. Results: We found that changing the inclination has no effect on PASA (p>
0.1). The pronation of first metatarsal has found to have a positive effect on PASA (p<
0.005). As the degree of pronation increases, the degree of PASA is found to be increased also. No difference was found between the measurements of x-ray and digital photography images. Discussion: Inclination of the first metatarsal can change depending on the height of the medial longitudinal arch. By this experimental study we tried to simulate the pes cavus and pes planus deformity on the radiologic measurement of the hallux by modifying the inclination and pronation of the first metatarsal. According to the current study, inclination has no effect on measurement of PASA. Pronation of the first metatarsal accompanies some hallux deformities. As pronation influences the measurement of PASA, the current data suggests that the measurement of PASA is not suitable for making clinical and surgical decisions.
