Comparison of Three Pediatric Prosthetic Feet During Functional Activities

Unilateral below-knee amputees, doing well with an energy-storing prosthetic foot, expressed interest in doing more and received a multiaxial dynamic foot, with follow-up subjective reports of significant improvements in high-performance activities. The purpose of this study was to determine if the authors could objectively measure improved function in high-performance activities in active children and adolescents wearing multiaxial dynamic prosthetic feet, compared with an energy-storing foot. Sixteen children and adolescents with unilateral below knee amputations (11 Syme, 5 transtibial) tested three prosthetic feet. An energy-storing foot represented by the Seattle Lightfoot® (Seattle Limb Systems, Poulsbo, WA) and two multiaxial dynamic prosthetic feet represented by the College Park TruStep® (College Park Industries, Fraser, MI) and Otto Bock Luxon Max® (Otto Bock Health Care, Minneapolis, MN) were tested in this study. (Three of the 16 subjects were fit with a College Park TruPer® foot, instead of a College Park TruStep® foot, secondary to foot size limitations. The two feet are collectively referred to as the College Park TruStep® foot throughout this study.) Subjects completed six functional tests: cutting drill, sprinting, vertical jump, standing long jump, oxygen cost while on a treadmill, and computerized gait analysis. Fitting by a certified prosthetist and testing of the three prosthetic feet were done in varied order for each subject within 1 week. The study was double blinded so that neither the subjects nor experimenters had knowledge of the prosthetic foot identity during data collection. Results indicated no significant differences among the three prosthetic feet for cutting drill time, sprinting time, vertical jump height, long jump distance, or oxygen cost on the treadmill (mL O2/kg/meter). Computerized gait analysis showed no significant differences among the three feet for velocity, cadence, stride length, or prosthetic side step length. The College Park TruStep® had significantly greater dorsiflexion and plantarflexion motion and greater peak power generation in late stance during walking. Subjectively, five subjects preferred the Seattle Lightfoot®, six preferred the College Park TruStep® foot, and five preferred the Otto Bock Luxon Max® foot. The three feet tested in this study were comparable according to objective assessment during high-performance functional activities. The authors cannot explain the discrepancy between the subjective enthusiasm expressed in clinic with one of the multiaxial dynamic feet, and the lack of significant differences among the three prosthetic feet on objective testing. Individual subjective preference might be the determining factor in pediatric foot selection.