Are sesamoids and proximal phalanx of metatarsus primus varus deformity of hallux valgus feet displaced? A radiological study.

Background: The hallux valgus deformity is made up of misaligned first metatarsal, hallux, and sesamoids. Their angular deformities are well-studied, but not their positional displacements. A few available reports claimed the proximal end of the proximal phalanx and sesamoids were not shifted medially along with the first metatarsal head. However, the general observation is otherwise. This study revisits the issue.

Methods: A radiological study of 189 feet with and without the hallux valgus deformity was carried out to analyze the first metatarsal, hallux, and sesamoid positional changes in relation to the second metatarsal and among themselves. A total of 194 X-ray images with all relevant measurements that formed the raw database for this study were submitted for online viewing and reference.

Results: There was a statistically significant change in the first metatarsal, hallux, and sesamoid positions of feet with hallux valgus deformity compared to normal feet. All have migrated medially but to different degrees. It was contrary to the past findings of no change in sesamoid and hallux positions.

Conclusions: We agree with past findings that the metatarsus primus varus deformity is directly related to the failed medial metatarsosesamoid ligament. We also believe in the failure of the deep 1-2 transverse metatarsal ligament responsible for the sesamoid migration.