The effect of pronation and inclination on the measurement of the hallucal distal metatarsal articular set angle

Objective: In this study, we tried to evaluate the effect of pronation and the inclination of the first metatarsal on the measurement of distal metatarsal articular angle (DMAA) in 10 cadaver first metatarsals. Methods: Ten cadaver first metatarsals were fixed to a device. This device can change the inclination and pronation angles of the metatarsal. 15-30-45 degrees of inclination and 0-10-20 degrees of pronation were applied to the metatarsals. After applying radio-opaque putty to the medial and lateral articular edges and metatarsal dorsal diaphyseal ridge, the X-ray and digital images were taken at different degrees of inclination and pronation. A graphics software did the measurement of DMAA. The statistical analysis was done by paired sample t-test. Results: The inclination had no effect on DMAA (p>0.1). The pronation of the first metatarsal was found to have a positive effect on DMAA (p<0.005). As the degree of pronation increased, the degree of DMAA was found to also increase. We found no difference between the measurements of the X-ray and the digital images. Conclusion: According to the current data, the measurement of DMAA is not suitable for making clinical and surgical decisions. The inclination of the first metatarsal can change, depending on the height of the medial longitudinal arch. By doing this study, we are trying to simulate the pes cavus and pes planus deformity on the radiologic measurement of pronation of the hallux. According to our results, inclination has no effect on the measurement of DMAA. However, the measurement of DMAA is expected to be dependent on the rotational deformity of the hallux.