Does Hallux Valgus Exhibit a Deformity Inherent to the First Metatarsal Bone?

First Metatarsal Rotation in Hallux Valgus Deformity

“…Specifically, this study demonstrated that patients with HV have significantly greater pronation of the M1 head with an M1 intrinsic bony twist as seen with other long bones (eg, femoral anteversion, tibial external torsion) than those without HV. This phenomenon has been further confirmed by Kitashiro et al and Cruz et al 16,48 Also using WBCT-derived CAD models, Campbell et al again demonstrated a significant difference in M1 pronation between HV and controls; however, his method considered the rotational status of the second metatarsal as the reference. 9…”

“…40,63,71 Summarizing the outcomes of these contributions, HV is considered to be a complex pathologic process, varying in presentation and severity, with several potential etiological factors. M1 pronation is associated with 3 conditions that have been implicated in the pathogenesis of hallux valgus, namely, decreased arch angles, 29 hypermobility, 25,34,35,46,47 and torsional changes 16,48,62 of the first ray.…”

“…In this CT-based study of 27 women with HV compared to 12 controls without HV, on average, the M1 head was 13 degrees more pronated in the HV group, suggesting that in some patients with HV the M1 may be intrinsically twisted. 16,48…”

“…4,26 Then, either from genetic programming or perhaps stress on a rotated M1 head in the growing child, an intrinsic torsional deformity can develop as is commonly found in the growing tibia or femur (see label B in Figure 1). 16,48,62 Any M1 rotation will naturally lead to unbalancing of metatarsophalangeal joint reaction forces and stress on the medial metatarsophalangeal ligaments. As these stretch, the M1 head slides medially, accentuating the unbalancing of the joint reaction forces.…”

“…30,57,67 Three studies used weightbearing computed tomography (WBCT), 11,45,70 and 3 used computer-aided design (CAD) models extracted from WBCT imaging to measure the M1 rotation. 9,16,62 Illustrations and methodology of the described measurement techniques are reported in Figure 2.…”