Position of the first ray and motion of the first metatarsophalangeal joint.

The authors present a quantitative analysis of the effect that first ray position has on motion of the first metatarsophalangeal joint. A goniometer was constructed to measure the degrees of first metatarsophalangeal joint dorsiflexion with the first ray in three positions: weightbearing resting position, dorsiflexed 4 mm from the weightbearing resting position, and dorsiflexed 8 mm from the weightbearing resting position. First metatarsophalangeal joint dorsiflexion decreased 19% as the first ray was moved from the weightbearing resting position to 4 mm dorsiflexed, 19.3% as the first ray was moved from 4 mm dorsiflexed to 8 mm dorsiflexed, and 34.7% as the first ray was moved from the weightbearing resting position to 8 mm dorsiflexed. The biomechanical significance of decreased first metatarsophalangeal joint dorsiflexion that results from first ray dorsiflexion is discussed, and proposed bases for the pathomechanics of hallux abducto valgus and hallux rigidus deformities are presented.