Correlation between first tarsometatarsal joint mobility and hallux valgus severity

Purpose: The mobility of the first tarsometatarsal (TMT1) is said to be correlated to the severity of hallux valgus determined using both clinical and radiographic criteria. The sagittal mobility of the TMT1 joint can be evaluated objectively using a new ultrasound test, which quantifies it in the form of a unitless value (ratio of two measurements). The objective of this study was to describe the relationship between TMT1 mobility on an ultrasound test and hallux valgus severity. Hypothesis TMT1 joint mobility increases with hallux valgus severity.

Patients and methods: Forty-nine feet were included that were being treated for isolated hallux valgus and had no evidence of TMT1 hypermobility based on the dorsal drawer test. For each foot, the presence and intensity of load transfer (LT), the intermetatarsal angle (IMA), and the hallux valgus angle (HVA) were determined. Lastly, TMT1 mobility was evaluated with the ultrasound test.

Results: Clinically, no LT was present in 20 feet; it was present only under M2 in 20 feet and reached at least M3 in the other nine feet. The mean IMA on radiographs was 14.6° and the mean HVA was 34.5°. The value of the ultrasound test was significantly different between the three groups of clinical hallux valgus severity: 1.17 with no LT, 1.31 with isolated M2 LT, and 1.72 when LT was at least at M3. Furthermore, this value was correlated with the IMA but not the HVA.

Discussion: This study revealed a relationship between increased TMT1 mobility and hallux valgus severity based on clinical (LT) and radiographic (IMA) criteria. Thus, our working hypothesis is confirmed. However, there was no correlation between TMT1 mobility and HVA suggesting that this angle is less relevant for determining the severity of the condition. This is consistent with the classical pathophysiological concept of metatarsus primus varus where the hallux valgus originates in a metatarsus varus in the tarsometatarsal area.

Conclusion: The severity of hallux valgus is correlated with increased mobility of the TMT1 joint, which appears to have a causal role in this condition.