Some dorsiflexion gains are surprising
By Emily Delzell
A recent study validates the long-held clinical belief that, in appropriately selected children with cerebral palsy (CP), ankle dorsiflexion during swing phase improves after ankle plantar flexor surgery and that postsurgical rehabilitation should include a focus on dorsiflexor function.
The study, published in December in The Journal of Bone and Joint Surgery, was a retrospective cohort series of 53 children (mean age, 8 years, 11 months; range, 5.5 years-16 years 5 months; 24 girls) with hemiplegic CP (62%) or diplegic CP (38%). The children underwent gait analysis before and after surgical lengthening of the gastrocnemius-soleus group; investigators also analyzed data from physical examinations and dynamic electromyography in swing phase.
“We determined the majority of children had some pre-existing ankle dorsiflexor function, which improved postoperatively. For those children, the mechanism of improvement was correction of a restricting contracture of the plantar flexors,” said Jon R. Davids, MD, a pediatric orthopedic surgeon at Shriners Hospitals for Children in Sacramento, CA.
Davids and colleagues also reported a less-expected finding.
“A few children who appeared to have no preoperative dorsiflexor function had good function after surgery,” he said. “We can’t explain why the contracture release helped them. In some way we don’t understand, the neurological profile between agonist and antagonist was improved by surgery on one of those muscles.”
Basing decisions on the level of muscle contractures, surgeons performed either a gastrocnemius-soleus recession or a tendo Achilles lengthening as either a single-event, single-level surgery (15%) or as part of a single-event, multilevel surgery (85%). The mean time between the initial and postoperative follow-up study was two years, three months (94% of children were seen one to three years after surgery).
The change in Gross Motor Function Classification System classification level between the initial and follow-up studies was statistically significant for the entire cohort. Statistically significant improvements were also noted in ankle dorsiflexion passive range of motion, ankle dorsiflexor selective control, ankle dorsiflexor strength, and peak and mean ankle dorsiflexion in swing phase.
Before surgery 79% of the children had active ankle dorsiflexor function in swing phase; postoperatively 96% had function, and 10 extremities improved from absent to present dorsiflexor function.
Although postoperative ankle dorsiflexor strength improved significantly, pre- and postoperative muscle weakness in both dorsiflexor and plantar flexor muscles was common. Dorsiflexor strength was more than partially diminished in 61% of extremities preoperatively and 44% postoperatively; plantar flexor strength was at least moderately diminished in 83% extremities preoperatively and in 84% postoperatively.
“We knew the agonist and antagonist muscles were weak before surgery and that surgery would further weaken muscles we lengthened,” Davids said. “The opposing muscles improved in strength, but remained relatively weak. Surgeons should be cautious with surgical lengthening to weak muscles, selecting only patients with fixed muscle contractures that don’t respond to nonoperative interventions. Additionally, there should be a focus on rehabilitation and on strengthening all these muscles.”
Davids also emphasized the importance of gait analysis for preoperative assessment, surgical decision-making, and outcomes assessment.
“Quantitative gait analysis and a detailed clinical examination including range of motion, strength, and selective motor control are important to select the most appropriate candidates for orthopedic surgery,” agreed Eileen Fowler PhD, PT, director of research and education at the UCLA/Orthopaedic Hospital Center for Cerebral Palsy in Los Angeles, CA.
She and Davids both noted, however, that gait analysis is underutilized.
“Analysis of movement in children with cerebral palsy is complex, as each child has a unique motor profile,” Fowler said. “Collecting motion data currently requires sophisticated and costly equipment. Laboratory space and clinician time are additional constraints.”
Source: Davids JR, Rogozinski BM, Hardin JW, Davis RB. Ankle dorsiflexor function after plantar flexor surgery in children with cerebral palsy. J Bone Joint Surg Am 2011;93(23):e1381-1387.