The role of the first metarsocuneiform joint in juvenile hallux valgus.

Juvenile hallux valgus (JHV) is a relatively common condition in the female adolescent. The etiology of the condition has been attributed to various deformities in the forefoot, ranging from the first metatarsophalangeal joint, the morphology of the distal metatarsal, and the intermetatarsal angle (IMA). There have been very few studies evaluating the first metarsocuneiform (MTC) joint, and the results available vary. The purpose of this study is to more critically evaluate the MTC joint with novel angular measurements as a contributor to JHV. A cohort of 46 feet from 29 patients (average age 14.2 years) with hallux valgus as defined as IMA of greater than 10 degrees were evaluated. The hallux valgus angle, IMA, base of first metatarsal to articular surface of medial cuneiform angle, first metatarsal to cuneiform (1MCA), second metatarsal to cuneiform (2MCA), intrinsic medial cuneiform obliquity angle (COA), distal metatarsal articular angle, and ratio of first cuneiform to second cuneiform length were measured. The same was done for an age-matched control group of 36 normal feet from 25 patients (average age 13.2 years). The two groups were statistically compared. There were several statistically significant differences between the study and control groups. Naturally, the hallux valgus angle and IMA were statistically greater by definition. In addition, the distal metatarsal articular angle and 1MCA were significantly larger in the study group. The magnitude of the 2MCA was found to positively correlate with the magnitude of the IMA. The COA angle was not found to be statistically different. In conclusion, the role of the MTC joint in JHV has been evaluated earlier with varying results. The objective of this study is to critically evaluate the MTC joint with novel angular measurements to delineate its contribution to JHV. One such novel measurement is the 1MCA. The statistically significant increase in 1MCA suggests that a property intrinsic to the articulation between the medial cuneiform and the first metatarsal may be involved in JHV. Another angle, the 2MCA was found to positively correlated with increased IMA, further implicating the MTC joint as a contributor to increased IMA and thus, JHV. Third, the COA was used to define the intrinsic obliquity of the medial cuneiform articular angle. This angle was not found to be statistically different between the study and control groups, suggesting that the morphology of the cuneiform is not involved in JHV.