The influence of age at single-event multilevel surgery on outcome in children with cerebral palsy who walk with flexed knee gait.

Aim: Information on the timing and long-term outcome of single-event multilevel surgery in children with bilateral spastic cerebral palsy (CP) walking with flexed knee gait is limited. Based on our clinical experience, we hypothesized that older children with bilateral spastic CP would benefit more from single-event multilevel surgery than younger children. Moreover, any improvement in older children could be maintained with fewer additional surgery events.

Method: We performed a retrospective analysis of the long-term outcomes of single-event multilevel surgery. Thirty-two children (17 males, 15 females) who had received single-event multilevel surgery between 1995 and 2000 with a mean age at the time of surgery of 10 years 6 months (range 5y 8mo-15y 6mo; SD 3y 1mo) and in Gross Motor Function Classification System level II (n=12) or III (n=20) were included in the study. The inclusion criteria required that all children were ambulatory with spastic bilateral CP, had a flexed knee gait, had a full set of data for single-event multilevel surgery preoperatively and at 1 year and 10 years postoperatively, had not had previous surgery on their lower limbs, had not had any treatment with botulinum toxin A before gait assessment, and had not received intrathecal baclofen medication. The follow-up time lasted for over 10 years until the participants reached adulthood (mean age at the last follow-up 21 years 4 months, SD 3y 4mo). Data were collected on six separate occasions: preoperatively, at 1 year, at 2 to 3 years, at 5 years, at 7 to 8 years, and at 10 or more years postoperatively. The primary outcome was the Gait Deviation Index, and the secondary outcomes were the number and type of initial and additional surgeries. A linear mixed model and Spearman's rank correlation coefficient were used to prove the hypothesis.

Results: The older the child was at the time of the surgery, the better the long-term result ((Age,Time) =0.15; p=0.03). We did not find any correlation between age at the time of surgery and the number of bony or soft-tissue procedures performed initially as well as during the 10 years of follow-up.

Interpretation: Children with CP who require single-event multilevel surgery at an older age fare better in the long term than those who are younger at the time of surgery. The pubertal growth spurt is discussed as a contributing factor to gait deterioration.