Planovalgus foot deformity in cerebral palsy corrected by botulinum toxin injection in the peroneus longus: Clinical and radiological evaluations in young children

Background: In children with cerebral palsy (CP), overactivity of the peroneus longus (PL) muscle is a major contributor to pes planovalgus. This retrospective study assessed whether abobotulinumtoxinA injections into a PL showing premature activity on electromyography (EMG) clinically improved foot morphology in children with CP.

Methods: Study participants were <6 years old, had a diagnosis of CP, good functional abilities (Gross Motor Function Classification System level 1 or 2), equinovalgus (initial contact with the hallux or head of the first metatarsal) and overactive PL on EMG. The fore-, mid- and hindfoot were evaluated clinically and radiologically before and after injection of abobotulinumtoxinA (6-7 U/kg) into the PL. Radiological data were compared with reference values for children without pes planovalgus.

Results: In total, 16 children (8 males; 10 hemiplegia, 6 diplegia; mean age: 3.2±1.5 years) received treatment. Mean pre-and post-treatment angles in clinical assessment of dorsiflexion of the talocrural articulation did not differ with both knees flexed (24.4±7.5 vs. 22.2±8.0 degrees; P=0.19) or extended (17.2±8.0 vs. 16.6±6.8 degrees; P=0.36). Radiographic data pre-treatment versus reference data revealed forefoot pronation (metatarsal stacking angle 2.1±8.3 vs. 8.0±2.9 degrees; P=0.002), midfoot planus (lateral talo-first metatarsal 28.5±15.0 vs. 13.0±7.5 degrees; P<0.001; talocalcaneal angle 54.6±8.6 vs. 49.0±6.9 degrees; P=0.004) and significantly decreased calcaneus dorsiflexion, without hindfoot equinus (calcaneal pitch angle 7.9±6.0 vs. 17.0±6.0 degrees; P<0.001). After treatment, the metatarsal stacking angle did not differ from reference values (P=0.15). As compared with before treatment, treatment improved mean angles for metatarsal stacking (2.1±8.3 vs. 7.1±3.9 degrees, respectively, P=0.002), lateral talo-first metatarsal and talocalcaneal (both P<0.001), with no change in the hindfoot.

Conclusion: PL may be an early target for abobotulinumtoxinA treatment in pes planovalgus associated with premature PL activity in children with CP.