Comparative analysis of flexor hallucis longus tendon course in hallux valgus and normal foot anatomy

The flexor hallucis longus tendon has been implicated in the progression of hallux valgus, but its detailed course in this deformity remains insufficiently understood.

To determine whether the flexor hallucis longus maintains its position between the sesamoids in hallux valgus and to clarify changes in its relationship to the first metatarsal.

Retrospective comparative study; Level III evidence.

Using three-dimensional computed tomography, the flexor hallucis longus course was evaluated in 37 feet with hallux valgus and 39 normal feet. The flexor hallucis longus position relative to the sesamoids and its mediolateral distance from the first metatarsal axis were measured at the metatarsal head, midshaft, and proximal metatarsal levels. Intergroup comparisons and correlations with the hallux valgus angle and intermetatarsal angle were analyzed.

The flexor hallucis longus consistently remained between the sesamoids in both groups, with no significant intergroup differences in sesamoid-related measurements. However, the flexor hallucis longus was significantly more laterally displaced relative to the first metatarsal at all measured levels in the hallux valgus group. This displacement showed strong positive correlations with hallux valgus angle and intermetatarsal angle, particularly at distal levels.

In hallux valgus, the flexor hallucis longus maintains its intersesamoid position but shifts laterally relative to the first metatarsal. These findings may have important implications for surgical correction and prevention of recurrence.