Plantarflexed first ray

Plantarflexed first ray

This is assumed to be the classical ‘pes cavus’ foot.

Definition:
A deformity in which the first metatarsal is below the level of the lessor metatarsals when the STJ is in its defined neutral position and the midtarsal joint is in its assumed ‘locked’ position.

Aetiology:
Congenital or acquired
Acquired:
• Peroneus longus spasm, hyperactivity or contracture
• Triggering of hallux due to weakness of intrinsics  plantarflexes first ray
• Weakness or absence of the anterior tibial muscle – peroneus longus over powers
• Weakness of gastrocnemius and/or soleus – peroneus longus assists in heel lift  plantarflexes first ray
• Uncompensated rearfoot varus
• Neuromuscular
• Idiopathic

Prevalence:
Unknown

Clinical features:
Plantar plane of forefoot is everted relative to calcaneal bisection; first ray is plantarflexed below level of lessor metatarsals; high arch non-weightbearing – on weightbearing arch will flatten if adequate range of motion in midtarsal joint; appearance of ‘anterior metatarsal arch’; symptoms will be similar to what is described for forefoot valgus.

Congenital – there will be an equal range of motion above and below the abnormally plantarflexed position
Acquired - there will be an unequal range of motion above and below the level of the lessor metatarsal heads, but the first metatarsal head is held below the others

 
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