Gross anatomy of the interphalangeal joint of the great toe: implications for excision of plantar capsular accessory ossicles.

Bony or cartilaginous ossicles occur at the plantar aspect of the interphalangeal joint of the great toe. The variation in pattern, prevalence, and anatomic relationships of these structures is not clearly established in the literature, especially in a Caucasian population. Without this knowledge, pathology at this joint may be underestimated and surgical approaches may be poorly planned particularly as radiographs underestimate the incidence of ossicles at this joint. The aims of this study were to determine the incidence and pattern of ossicles at this joint and to establish their anatomic relationships to aid planning the approach for their excision. The interphalangeal joint of the left hallux was dissected in 40 British Caucasian cadavers and the pattern of nodules and their anatomic relationships were established. In 27.5% of subjects, there was no identifiable ossicle and, in these specimens, the tendon of flexor hallucis longus was adherent to the joint capsule. In the remaining specimens (72.5%), a bursa separated the tendon of flexor hallucis longus from the plantar joint capsule and nodules were found embedded within the joint capsule. More than half (52.5%) of the specimens had a single nodule located centrally within the plantar capsule and the remaining 20% had two nodules lying within the capsule. This study shows that a large proportion of the population have either one or two bony or cartilaginous ossicles at this joint. It has also shown that, when present, these structures do not lie within the tendon of flexor hallucis longus and may be most safely excised from a medial approach.