Devices correct residual drop-foot
By Emily Delzell
Compared with walking barefoot, ankle foot orthoses (AFOs) improved gait parameters in children with spastic unilateral cerebral palsy a year after they had undergone lower limb surgery to improve their ambulation, according to research from Norway.
Children with spastic unilateral cerebral palsy often have gait deviations that are most frequently caused by ankle equinus, and sometimes by proximal joint involvement. Those with fixed deformities may undergo surgery to help normalize gait, and AFOs are commonly prescribed during the postoperative rehabilitation period to provide mechanical support and prevent recurrence of deformities.
The current study found that the main impacts of continuing postoperative AFO beyond the initial rehabilitation period were correction of residual drop-foot and improved prepositioning for initial contact at the foot, ankle, and knee, reported lead author Ingrid Skaaret, CPO, MSc, a prosthetist-
orthotist in the Department of Child Neurology at Rikshospitalet at Oslo University Hospital, and colleagues the University of Oslo.
“While triceps surae lengthening improves dynamic ankle range of movement, swing-phase drop-foot frequently persists in these children, possibly due to inadequate activation of the dorsiflexors,” she said. “Practitioners and patients should be prepared that gait problems may not be completely resolved after lower limb surgery and the first rehabilitation period.”
Skaaret and her colleagues used 3D gait analysis to measure changes in Gait Profile Scores (GPS) and kinematic, kinetic, and temporal spatial variables in 33 children (17 girls) with a mean age of 9.2 years. They evaluated preoperative gait while children walked barefoot at a self-selected speed on a 12-m walkway and gait about one year after surgery on the same walkway while participants walked barefoot and with AFOs and shoes.
A child neurologist, a certified prosthetist-orthotist (Skaaret), a physical therapist, and an orthopedic surgeon categor- ized the participant’s pre and postoperative gait patterns into four types: Type 1, a pattern with dynamic ankle equinus or drop foot in swing; Type 2, true equinus gait with the knee in extension or recurvatum during stance; Type 3, true equinus gait with a flexed knee during stance; and Type 4, stronger proximal involvement, usually with frontal and transverse plane deviations.
Investigators based decisions about surgery and postoperative follow-up, including the type of orthosis prescribed, on each participant’s preoperative gait pattern and a physical examination, as well validated treatment algorithms.
In children with Type 1 or 2 gait patterns, who underwent triceps surae lengthening for equinus, Skaaret and colleagues prescribed hinged AFOs (HAFOs) to allow ankle dorsiflexion, restrict plantar flexion, and lift the foot during swing. Children with Type 3 or 4 gait patterns underwent hamstrings lengthening, rectus femoris transfer, or both. The ground reaction AFOs (GRAFOs) prescribed for these children restricted dorsiflexion and plantar flexion and applied an external knee extension moment during stance. Preoperatively, the Type 2 gait was most common (22 children, while after surgery most participants (21) walked with a Type 1 gait.
Practitioners immobilized ankles with splints for five weeks after surgery, then fitted shoes and AFOs, which patient and their families were told to use all day for a year.
Surgery significantly improved GPS, kinematics, and kinetics in the barefoot condition compared with preoperative measures. Postoperatively, walking in AFOs versus barefoot reduced ankle plantar flexion by an average of 5.1° and knee flexion by 4.7° at initial contact, enhanced ankle moments during loading response, and inhibited the generation of push-off power. Wearing the devices also raised gait velocity and step length significantly, while lowering cadence.
Children had significant improvements in their nonaffected limbs after surgery, including increased ankle dorsiflexion and knee stance. Postop AFO use increased plantar flexion moment and reduced knee flexion at initial contact, stance ankle maximum dorsiflexion, and power generation versus barefoot.
The Journal of Children’s Orthopaedics published results in April.
The lower push-off propulsion the investigators noted with AFOs did not negatively affect gait velocity, and gait with the AFOs was described by Skaaret and her colleagues as more energy efficient since the children were taking longer steps at a lower cadence compared with barefoot.
“The additional knee extension with AFOs versus barefoot seen in participants postoperatively could be explained by less activation of knee flexors secondary to improved ankle prepositioning in the orthoses. Another explanation is that the distally added weight of shoes and orthoses may increase knee angular momentum,” she said.
The study confirms the functional efficacy of postoperative AFO use in children with spastic unilateral cerebral palsy, particularly for improving swing phase clearance and prepositioning of the foot for initial contact, the Norwegian group reported. Previous research has found that children with spastic unilateral cerebral palsy had a 38% risk of recurrent equinus deformity five to ten years after isolated calf muscle lengthening
Longer-term study is needed to show whether the AFOs can reduce the risk of postsurgical recurrence, Skaaret said.
Skaaret I, Steen H, Huse AB, Holm I. Comparison of gait with and without ankle-foot orthoses after lower limb surgery in children with unilateral cerebral palsy. J Child Orthop. 2019;13(2):180-189.
Borton DC, Walker K, Pirpiris M, et al. Isolated calf lengthening in cerebral palsy. Outcome analysis of risk factors. J Bone Joint Surg. 2001;83-B:364-370.