Congenital Vertical Talus Workup

Updated: Jan 25, 2019
  • Author: Jeffrey D Thomson, MD; Chief Editor: Murali Poduval, MBBS, MS, DNB  more...
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Workup

Imaging Studies

Radiography

Weightbearing anteroposterior (AP) and lateral views of the foot are the first radiographs that must be obtained. A lateral radiograph with the foot in maximum plantarflexion is mandatory to confirm congenital vertical talus (CVT).

Because the navicular may not be ossified, the alignment of the first metatarsal to the talus must be evaluated. In a vertical talus, the metatarsal does not line up with the talus. Lines drawn through the long axis of the first metatarsal and the talus converge on the plantar aspect of the foot. Hamanishi described two radiographic angles: the talar axis–first metatarsal base angle (TAMBA) and the calcaneal axis–first metatarsal base angle (CAMBA). [23] The changing point from a flexible oblique talus to rigid CVT is a TAMBA of approximately 60° and a CAMBA of 20°.

Magnetic resonance imaging

Magnetic resonance imaging (MRI) of the spine may be indicated if an occult spinal dysraphism, such as lipomeningocele, is suspected. [24] Posterior and lateral lumbar spine radiographs also may be useful to exclude occult spinal dysraphism.

Thometz et al evaluated nine patients with CVT using MRI to evaluate the three-dimensional morphologic changes and pathoanatomy. They concluded that there is significant pathology at the level of the subtalar joint. [25]

Ultrasonography

Ultrasonography has been reported to be helpful in distinguishing between CVT (irreducible talonavicular dorsal dislocation) and oblique talus (reducible talonavicular dorsal dislocation).

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Histologic Findings

In 2011, Merrill et al published a report evaluating the skeletal muscle abnormalities in CVT. [7] Of note is that their subjects did not constitute a homogenous group: Six of the 11 patients had idiopathic vertical talus, whereas the remaining five had a variety of associated findings. The authors took biopsy samples from the abductor hallucis muscle and found that all patients with CVT had abnormalities. These abnormalities included abnormal variation in muscle fiber size, type I muscle fiber smallness, and abnormal fiber type predominance.

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