Review Question - QID 2208

Figure A is a photograph of a dorsal bunion. This occurs due to the unopposed action of the tibialis anterior with weakness of the peroneus longus, which is innervated by the superficial peroneal nerve.

A dorsal bunion develops due to a normal tibialis anterior muscle overpowering a weak peroneus longus. This results in an elevation of the first ray and supination of the forefoot. This is seen in patients with a history of clubfoot. In these patients, the gastrocnemius-soleus complex is usually weak due to prior release and is therefore compensated for by plantar flexion of the hallux metatarsophalangeal joint (MPJ) using the flexor hallucis brevis (FHB). Over time a functional contracture of the FHB develops. When ambulating, the plantarflexed hallux and proximal phalanx exert a dorsally directed force at the MPJ forcing the first ray into more elevation.

McKay reviewed 17 feet with dorsal bunions. He reports that these are most often seen in children after operations for post-poliomyelitic paralysis or clubfoot. He treated these patients with a transfer of the tendons of the FHB and the abductor and adductor hallucis to the neck of the first metatarsal. In 17 treated feet, he observed failure in a patient with arthrogryposis.

Burger et al. performed a review in the evaluation and surgical management of the overcorrected clubfoot deformity in the adult patient. They report that correction of a dorsal bunion in the setting of an overcorrected clubfoot fails if the underlying muscular imbalance is not correct. They report that for an isolated dorsal bunion a transfer of the tibialis anterior to the middle cuneiform is sufficient to restore balance. They conclude that removing the deforming force while maintaining adequate dorsiflexion power, the muscle imbalance is corrected.

Figure A is a photograph of a dorsal bunion.

Incorrect Answers:
Answers 1, 2, 3, & 5: The peroneus longus is innervated by the superficial peroneal nerve.