NEW ORLEANS — The mechanical design of an ankle foot orthosis could influence gait in ambulatory clubfoot patients, according to research presented at the American Academy of Orthotists and Prosthetists Annual Meeting and Scientific Symposium.
Robert Lin, CPO, FAAOP, conducted a study to examine the ankle and knee kinetics and kinematics of a patient using a standard hinged ankle foot orthosis (AFO) vs. an offset, oblique axis articulating AFO.
The single subject cohort was a 6-year-old male with a 3-D, idiopathic, congenital deformity. The clinical presentation included a combination of metatarsus adductus, forefoot supination, calcaneal varus and planterflextion.
Researchers performed gait testing post-clubfoot and randomly assigned which orthotic design was applied first. An independent ambulator was used for both designs and adequate time was given for the patient to adjust to each. Gait analysis was conducted using VICON software.
“We looked at things like peak dorsiflexion stance, time of peak dorsiflexion, range of motion and mean progression angles of the knee,” Lin said. “We also looked at peak knee flexion, external angles, knee rotation, ankle planterflexion moments and peak ankle power.”
Findings showed a higher generation of ankle power with the offset, oblique AFO design. The external foot progression angle, knee and hip rotation also more closely approximated normal values with the offset, oblique AFO. The saggital plane ankle range of motion did not increase in either design.
A strategic offset ankle joint could promote normal ankle and knee kinetics and kinematics that compensate for residual clubfoot gait tendencies, according to the findings. It can also have further clinical benefit, Lin said.
“We saw results that were quite impressive. But since its inception, the design has become more of a functional AFO to mitigate internal rotation problems,” he said. “We have used it irrespective of the cause of the internal rotation…so it is not limited just to the clubfoot diagnosis. It is much more widely applicable.” – by Shawn M. Carter
Lin R. Paper F30. Presented at: American Academy of Orthotists and Prosthetists Annual Meeting and Scientific Symposium; Feb. 18-21, 2015; New Orleans.
Disclosure: Lin reports no relevant financial disclosures.