Complete Agenesis of Both Metatarsophalangeal Sesamoids with Contralateral Agenesis of Fibular Sesamoid Associated with Hallux Valgus

Abstract

he metatarsophalangeal joint of the great toe differs from that of the lesser toes because it has a sesamoid mechanism and a set of intrinsic muscles that stabilize the joint and provide motor strength to the first ray.1 The hallucal sesamoids are a consistent entity in humans, originating in the tendons of flexor hallucis brevis. They appear within the seventh or eighth week of embryonic development as islands of undifferentiated connective tissue. By the twelfth week, chondrification begins, but it is not until 8 to 10 years of life through multiple ossification centers that they ossify. 2 Often these centers of ossification do not coalesce and remain partite in a significant portion of the population. The function of the hallucal sesamoids is to absorb weight-bearing forces and enhance the load-bearing capacity of the first ray. They power plantar flexion of the first ray by increasing the moment of the flexor hallucis brevis and function to elevate the first metatarsal head, which dissipates the forces on the metatarsal head.