Purpose: The morphology and mechanical function of the metatarsosesamoid joint plays an important role in metatarsal head stability. The position of the sesamoids during the development of hallux valgus was evaluated by Inges, Haines and Tourne who distinguished three stages. Cartilage lesions in the context of hallux valgus have not been analysed with precision. The purpose of our work was to identify metatarsosesamoid lesions on anatomic specimens in patients who had undergone hallux valgus surgery.

Material and methods: We dissected 12 metatarsosesa-moid joints (4 right, 13 left) from laboratory specimens and evaluated the degenerative lesions. For each specimen, we noted the metatarsophalangial angle and the AADM. We also examined 17 metatarsal specimens to determine the persistence or absence of the median crest as a sign of wear. Using the same protocol, we examined the joints surfaces and determined degenerative lesions during 20 SCARF procedures for hallus valgus.

Results: For the twelve laboratory specimens, we observed: for the plantar joint surface of M1, the joint surfaces were perfectly intact in 2 specimens, the sagittal crest was worn away in 4, degenerative lesions appeared on the medial surface in 4, and on the lateral surface in 2. For the sesamoids, the degenerative lesions involved both sesamoids in 1 specimen, the lateral sesamoid in 2, the medial sesamoid in 4, and none in 3. Lesions of the metatarsophalangial joint were diffuse in 1 case, localised in 5 and absent in 6. For the 17 metatarsals, for an AADM between 4 and 12, no lesion was found in 6 cases, degenerative lesions involving both sesamoids in 1, the lateral sesamoid in 1 and the medial sesamoid in 2. For an AADM greater than 12, the metatarso-sesamoid joints surfaces were intact in 1 case, the sagittal crest was worn off in 4, and degenerative lesions involved the medial surface in 4 and the lateral surface in 1.

Conclusion: This anatomy study demonstrated the precise topography of degenerative lesions of the metata-sosesamoid joint. This data base should be useful for evaluating functional outcome as a function of the meta-tarsosesamoid lesions in the treatment of hallux valgus.