Miller [1Miller Knee, leg and foot[Edited by Miller].   Cerebral palsy New York: Springer (2005). 667-802

Cliquez ici pour aller à la section Références] describes the natural history of planovalgus in cerebral palsy (CP) as the common foot deformity in CP children. He emphasizes that the causes are an early muscle imbalance by overactivity of peroneal muscles and the primary pathology begins when the talus head is uncovered medially, associated with a talus equinus in X-rays and a subluxated talus head causing a midfoot planus. In hemiplegic children(<6years), a premature overactivity EMG of Peroneus Longus (PL) during swing phase(SW) is described with a dynamic equinus and hindfoot valgus at initial contact by Boulay [2Boulay Dynamic equinus with hindfoot valgus in children with hemiplegia Gait Posture 2012 ;  36 (1) : 108-112 [cross-ref]

Cliquez ici pour aller à la section Références]. It suggests that PL could be a therapeutic target by botulinum toxin (BoNT-A) injections. This hypothesis is tested in a retrospective study. The clinical and radiological efficiency is assessed.

Sixteen hemiplegic (3.25years±1.5), GMFCS 1 or 2, with a planovalgus foot deformity during the stance phase and, during SW, a dynamic equinus with hindfoot valgus and a premature overactivity of PL were treated by a BoNT-A injection (Dysport^®,Ipsen) into PL. Radiological foot parameters measured forefoot pronation, midfoot planus, valgus and equinus of hindfoot. These parameters are validated in the healthy and hemiplegic children. A paired t-test compared for each angle the pre and post-toxin measurement.

The parameters described between pre-toxin vs normal data: calcaneal-pitch (8°vs 17°P<0.001), talocalcanealangle (55°vs 49°P<0.05),lateral talo-first metatarsal angle (29°vs 13°P<0.001) and metatarsal-stacking angle (2°vs 8°P<0.001). There was a non-significative difference, between pre vs post-toxin, for the calcaneal-pitch angle (7°vs 9°) and the anteroposterior ankle angle(14°vs 15°P<0.05). There was a significative difference, between pre vs post-toxin, for the talocalcaneal angle (55°vs 46°P<0.001), the lateral talo-first metatarsal angle (29°vs 18°P<0.01) and the metatarsal stacking angle (2°vs 7°P<0.001).

Before injections, the radios showed a hindfoot valgus, a dorsalflexed calcaneus with midfoot planus and a forefoot pronation. After injections, midfoot planus is reduced by the decrease of talus subluxation and there was not forefoot pronation. Injections into PL seemed to have a therapeutic actions on fore and midfoot that improved clinically the hindfoot valgus but without action on the dorsalflexed of calcaneus depending on the gastrocsoleus complex. PL could be an early therapeutic target for BoNT-A in planovalgus.