The Treatment of Pes Cavus: (Section of Orthopædics)

(A) REVIEW OF EARLIER METHODS: Manipulations; fasciotomy; Phelps' operation; Steindler's operation; anterior arch-plates.(B) Reasons for their relative failure.-(1) Correction of the deformity is imperfect, and (2) as they deal with the existing deformity only, and not with its cause, the result is not permanent; relapse occurs.(C) Evolution of the modern operation.-Two facts in connexion with the ordinary "idiopathic" type of pes cavus are constant, and therefore noteworthy, viz.: (a) the deformity is entirely a fore-foot deformity, consisting of dropping-down of the fore-foot, and (b) paralysis of the lumbrical or of the interosseous muscles is never found at operation.This suggests that a cause for the fore-foot drop should be sought. Pes cavus never occurs in flail foot, but may develop in mild cases of paralysis of the anterior tibial (extensor) group of muscles; this suggests that in less marked cases of paresis of these muscles, pes cavus may result; in fact, this has been observed.Finally, a case in which the legs were known to have been normal, and one was damaged, anteriorly (thereby weakening the long extensor action) resulted in the development of typical unilateral pes cavus.The part played by the interossei and lumbrical muscles is purely passive, and results from the dropping-down of the metatarsal heads beyond their line of action. This can be demonstrated on any case in which contracture of the soft parts of the toes has not occurred; pushing-up the anterior arch brings down the toes, and vice versa.The problem, then, seems to consist of finding a means to strengthen the relatively weak long extensors, and of giving them a stronger and more direct lifting action upon the metatarsal heads.(D) The modern operation.-This consists of two distinct parts: (a) the correction of existing deformity, and (b) the adoption of measures to prevent recurrence of the deformity. (a) Mere non-selective elongation of the structures of the sole is inadequate; those on the inner side must be lengthened and flattened more than those on the outer side; therefore, the joint-capsules, fasciae, tendon-sheaths, etc., are divided as freely as possible, by open operation, on the inner side of the foot. Steindler's section of all structures attached to the os calcis then allows the whole foot to elongate; this is followed by vigorous manipulation, and this completes stage (a).(b) The extensor tendons are then transplanted into holes bored through the necks of the metatarsal bones (Murk Jansen's operation, modified), and are sutured, the foot being held over-corrected meanwhile.If the toes are contracted, and the above method does not correct the deformity, arthrodesis of the proximal interphalangeal joints is performed; the fifth toe may perhaps be amputated.(E) After-treatment and results.-Other Points: The results seen to be permanent. At what age should this operation be performed? Treatment, at earlier ages, The type and degree of disability caused by pes cavus. Relief of advanced cases.