ANATOMIC DETERMINANTS OF FIRST METATARSOPHALANGEAL FLEXION MOMENTS INHALLUX-VALGUS

A laboratory cadaver model was used to assess the effects of the major anatomic components of hallux valgus deformity on first metatarsophal angeal flexion moments, The individual components of the flexor halluc is longus' effective tendon moment arm were evaluated as a function of imposed hallux valgus, of hallux pronation, and of combined hallux va lgus and pronation, To simulate the effects of distal first metatarsal surgery, the components' changes after metatarsal head lateral transl ation or supination were assessed, Significant changes in effective te ndon moment arm occurred with increases in the hallux valgus angle, wi th changes in the hallux pronation angle, and with combined increases in the hallux valgus angle and hallux pronation angles, The changes in volved primarily were a redirection of the moment vector's projection within the superior and inferior plane or medial and lateral plane, ra ther than an appreciable alteration of the magnitude of the resultant, By contrast, neither translational nor rotational displacements of th e metatarsal head influenced any of the individual components of the e ffective tendon moment arm.