Injection frequency of botulinum toxin A for spastic equinus: a randomized clinical trial

Abstract

Aim: We compared two botulinum toxin A (BoNT-A) injection frequency regimens, 12-monthly versus 4-monthly, for spastic equinus in a randomized clinical trial. The primary outcome measure was passive ankle dorsiflexion.

Method: Forty-two ambulant children with spastic equinus, secondary to cerebral palsy (23 males and 19 females; mean age 3y 6mo, SD 13mo; GMFCS levels I [n=20], II [n=19], III [n=3]) were randomized to receive either 12-monthly or 4-monthly BoNT-A injections to the calf, over a 26-month period. Twenty-one children had spastic hemiplegia, 21 children had spastic diplegia. A fixed 6U/kg dose of Botox was injected into the gastrocnemius muscle of both limbs in children with diplegia and the gastrocsoleus of the affected limb in children with hemiplegia, under mask anaesthesia.

Results: Forty-two children entered the trial with 21 participants randomized to each group. There were three withdrawals and two children received serial casting midway through the trial. There was no significant difference in passive dorsiflexion between 12-monthly and 4-monthly regimens (p=0.41). There were also no significant between group differences on secondary outcome measures. There were no serious adverse events - the rate was 1.2 adverse events per child per year in the 12-monthly group and 2.2 adverse events per child per year in the 4-monthly group. Subgroup analysis revealed a significant difference in passive dorsiflexion between children with hemiplegia and diplegia (p=0.01).

Interpretation: There was no significant difference between 12-monthly and 4-monthly injection regimens on passive dorsiflexion or secondary outcome measures. BoNT-A injections for spastic equinus may be recommended on a 12-monthly basis.