Background: Originally introduced by Morton, the concept of
hypertrophy of the medial cortex and the entire shaft of the second metatarsal
as an objective sign of increased mobility of the first ray has not been
subjected to much scrutiny. The goal of the current study was to assess the
clinical relevance and reliability of radiographic measures of hypertrophy of
the second metatarsal in relation to mobility of the first ray, pes planus,
and tightness of the gastrocnemiussoleus in both control subjects and patients
with diagnosed disorders of the forefoot.
Methods: Four study groups of forty-three subjects each were
evaluated. The cohort included an asymptomatic control group as well as three
groups made up of patients with symptoms and a diagnosis of hallux valgus,
hallux rigidus, or interdigital neuroma. Mobility of the first ray (as
measured with a device and method described by Klaue et al.), arch height, and
ankle dorsiflexion were measured on physical examination. Plain weight-bearing
radiographs and previously established equations were used to determine
hypertrophy and the length of the second metatarsal, and the hallux valgus and
first-second intermetatarsal angles were measured on plain radiographs as
Results: There was no significant difference between the control and
symptomatic groups with regard to the values for hypertrophy of the second
metatarsal. The patients with hallux valgus deformity had significantly
greater mobility of the first ray (p < 0.001) compared with the controls.
No correlation was found between values for hypertrophy of the second
metatarsal and mobility of the first ray, the length of the first metatarsal,
pes planus, or restricted ankle dorsiflexion. No correlation was found between
mobility of the first ray and either pes planus or restricted ankle
dorsiflexion. A weak correlation (r = 0.4) was noted between increased
mobility of the first ray and the hallux valgus angle.
Conclusions: Our findings do not support Morton's concept that
medial cortical hypertrophy and increased shaft width of the second metatarsal
are associated with increased mobility of the first ray or relative shortness
of the first metatarsal. In addition, hypertrophy of the second metatarsal was
not associated with either pes planus or restricted ankle dorsiflexion. We
found the practice of using hypertrophy of the second metatarsal as an
indicator of mobility of the first ray to be unreliable, and thus we consider
it to be an inappropriate indication for arthrodesis of the first
metatarsocuneiform joint in the treatment of hallux valgus deformity.
Level of Evidence: Diagnostic study, Level IV-1
(case-control study). See Instructions to Authors for a complete description
of levels of evidence.