The treatment of paralytic convex pes valgus.

Descriptions in the literature of the treatment of congenital convex pes valgus have been mainly concerned with patients who have not shown any overt paralytic lesion (Lloyd-Roberts and Spence 1958, Herndon and Heyman 1963, Eyre-Brook 1967, Harrold 1967). Convex pes valgus, or vertical talus deformity of the foot, quite often occurs in association with malformation of the central nervous system. It is said to account for 10 percent of foot deformities in surviving children with myelomeningocele (Sharrard and Grosfield 1968) and occurs in association with other congenital disorders of the neuraxis such as diastematomyelia and lipoma of the cauda equina. The external appearance and clinical features of the foot in the paralytic and non-paralytic types of congenital convex pes valgus are essentially the same, and the description of Lloyd-Roberts and Spence (1958) has been used as the basis for inclusion of a foot in the present series. The sole of the foot is convex, the lowest point of the convexity being the prominent head of the talus. The hindfoot is plantarfiexed, or occasionally in the neutral position, compared with the slightly dorsiflexed position of the normal calcaneus. The talus is abnormally vertical and there is valgus deformity of the subtalar joint. The forefoot is dorsiflexed, abducted and everted at the midtarsal joint with displacement of the navicular bone on to the neck of the talus. The foot deformity is usually rigid and cannot be corrected to the neutral position. The talo-navicular displacement cannot be reduced. Figures 1 and 2 show the external features and Figures 3 and 4 the radiological appearance in a typical case. Herndon and Heyman (1963), Eyre-Brook (1967) and Harrold (1967) have reported satisfactory results from operative treatment of vertical talus deformity. None of Herndon’s cases was associated with spina bifida; of Eyre-Brook’s four cases, two had spinal dysraphism and one was thought to have arthrogryposis. Harrold’s cases appear to have been unassociated with spinal abnormalities. In the paralytic type of convex pes valgus imbalance can usually be demonstrated in the strength of muscles acting on the foot, and Drennan and Sharrard ( 197 1 ) suggested that convex pes valgus is caused by a neuromuscular imbalance between a weak tibialis posterior and strong evertors of the foot. If this is true, then good results might be predicted from an operation which aims to correct this imbalance by tendon transfer. Poor results might be expected from operations which achieve correction of the deformity by dividing soft tissues or removing bone, but which fail to restore a satisfactory balance of muscle action. This paper reviews the results of a series of patients treated by various operative procedures.