Since AFO stiffness is a key characteristic that determines how much support or restraint an AFO can provide, a study published in June in the Disability and Rehabilitation Journal attempted to quantify AFO prescriptions for a group of patients as well as to evaluate the impact the AFOs would have on the push-off phase. The researchers suggest that quantification of AFO stiffness may provide understanding of why certain orthotic interventions are successful or unsuccessful and may lead to better AFO prescriptions.
Six patients were included in the study; three were prescribed an AFO for ankle support and three were prescribed an AFO for ankle and knee support. A traditional polypropylene AFO (AFOPP) and a novel carbon-selective laser sintered polyamide AFO (AFOPA) were produced for each patient. AFO ankle stiffness was measured in a dedicated test rig. Gait analysis was performed under shod and orthotic conditions.
Study results showed that patient mass normalized AFOPP stiffness for ankle support ranged from 0.042 to 0.069 Nm·deg−1·kg−1, while for ankle and knee support it ranged from 0.081 to 0.127 Nm·deg−1·kg−1. On the group level, the ankle range of motion and mean ankle velocity in the push-off phase significantly decreased in both orthotic conditions, while peak ankle push-off power decreased nonsignificantly, the study found. On the group level, the study found that no significant improvements in walking speed were observed. However, after patient differentiation into good and bad responders, the study found that in good responders peak ankle push-off power tended to be preserved and walking speed tended to increase.