Introduction: Isolated avulsion fracture at the plantar lateral base of
the first metatarsal (M1) is very rare.
Case report: A 35 year old overweight woman sustained an eversion
strain of her right foot. Despite pain along M1 she was able to continue
walking for three days before presenting to her family doctor. Swelling
on the plantar aspect of the foot was noticed, there was also pain at
eversion of the foot and extension of the ankle. Plain X-ray showed no
abnormalities. A MRI showed minimal bone bruise at the basis of M1
and a partial rupture of the peroneus longus tendon at its insertion.
The patient was allowed to walk with partial weight bearing with a soft
ankle brace. After 6 months she presented at our hospital because of
persistent pain. There was still a painful insertion of the peroneus
longus but active plantarflexion of M1 was possible. Plain X-rays were
poorly contributive except for a discrete flattening of the longitunal
arch. CT-scan showed a non displaced fracture at the M1-basis. A
protocol with partial weight-bearing in a short-leg cast and partial
weight-bearing orthosis each for 6 weeks was unsuccessfully
attempted. Therefore, an excision of the non healed bone fragment
at the basis of M1 and a first tarsometatarsal joint arthrodesis were
performed. Postoperatively the patient wore a partial weight-bearing
short leg cast for 6 weeks followed by a weight-bearing short leg cast
for 6 weeks with favourable outcome.
Discussion: Initial internal fixation has been reported to lead to good
results [1, 2]. In our case the conservative treatment failed and leaded
to non union. At that time we considered as too risky (overweight) to
excise the fragment and reattach the peroneus longus tendon.
Therefore, we excised the fragment and fused the first tarsometatarsal
joint. This procedure allowed, at least partially, to compensate for the
function of the peroneus longus tendon.
1 Murakami T, et al. Avulsion fracture of the peroneus longus at the
first metatarsal insertion: a case report. Br J Sports Med. 2004.
2 Kwak HY, and Bae SW. Isolated avulsion fracture at the plantar
lateral base of the first metatarsal: a case report. Foot Ankle Int 2000.