Quantitative Assessment of the Obliquity of the First Metatarsal-Medial Cuneiform Articulation

The so-called obliquity of the first metatarsal-medial cuneiform articulation has been described as an atavistic trait of human foot morphology, and it is commonly proposed as a relative risk factor for development of the hallux abductovalgus (HAV) deformity. The objectives of this investigation were to 1) provide descriptive normative radiographic data on a series of first metatarsal-medial cuneiform articulations and 2) correlate these findings to other common radiographic parameters used to define the HAV deformity. We measured radiographic parameters including the first intermetatarsal angle, hallux abductus angle, tibial sesamoid position, Engel's angle, and 2 measures of obliquity in the transverse and sagittal planes on a consecutive series of 136 weightbearing foot radiographic projections from subjects without a history of foot/ankle surgery or fracture/dislocation. Measurements were considered as continuous variables, graphically depicted against each other on frequency scatter plots, and analyzed by means of Pearson correlation coefficients. Only 1 bivariate comparison demonstrated a weak negative correlation (Engel's angle versus Obliquity_1 [Pearson –0.259; p = .002]). The results of this investigation did not demonstrate a statistically significant or clinically substantial relationship between the obliquity of the first metatarsal-cuneiform joint and common radiograph parameters of the HAV deformity. Although not specifically studied here, these results might potentially indicate function, as opposed to structure, in the developmental pathogenesis of the HAV deformity.