Analysis of Serial Radiographs of the Foot to Determine Normative Values for the Growth of the First Metatarsal to Guide Hemiepiphysiodesis for Immature Hallux Valgus

BACKGROUND:Hallux valgus deformity in the immature patient can be difficult to manage, as osteotomy can result in recurrence with additional growth. Lateral hemiepiphysiodesis of the first metatarsal offers a promising alternative, by permitting gradual correction of the intermetatarsal angle with growth. An important limitation of this approach is the lack of normative tables of first metatarsal growth to guide timing of intervention. METHODS:First metatarsal lengths were measured from anteroposterior foot radiographs of children. For females, 95 patients totaling 894 radiographs were used ranging from 6 months to 18 years of age. For males, 122 patients totaling 1018 radiographs were measured ranging from 8 months to 19.5 years of age. All patients with image series including a closed proximal metatarsal physis were sorted into an older group, with multipliers generated by setting last image to a multiplier of 1. Patients with serial imaging not inclusive of a closed physis were classified as a younger group, with multipliers based off of the multiplier at age 7 from the older group. First metatarsal multiplier values were then compared with published multiplier values for the overall foot. RESULTS:For both females and males, the multipliers followed a logarithmic curve versus age, with R values of 0.921 and 0.888, respectively. Comparison of the first metatarsal multiplier values with previously studied multiplier values of the entire foot showed high correlation with ICC=0.955 for females and ICC=0.969 for males. CONCLUSIONS:The pattern of growth of the first metatarsal follows a logarithmic regression curve. These normative tables allow for clinical prediction of first metatarsal remaining growth based on age and sex, and in turn guide timing of hemiepiphysiodesis for the surgical correction of hallux valgus deformity. CLINICAL RELEVANCE:The normative tables generated in this study can be used for the calculation of hemiepiphysiodesis and the timing of intervention. Future clinical correlation studies will be important.