Improved weight-bearing symmetry for transfemoral amputees during standing up and sitting down with a powered knee-ankle prosthesis

Publication date: Available online 11 December 2015
Source:Archives of Physical Medicine and Rehabilitation
Author(s): Ann M. Simon, Nicholas P. Fey, Kimberly A. Ingraham, Suzanne B. Finucane, Elizabeth G. Halsne, Levi J. Hargrove
ObjectiveTo test a new user-modulated control strategy that enables improved control of a powered knee-ankle prosthesis during sit-to-stand and stand-to-sit movements.DesignWithin-subject comparison study.SettingGait laboratory.ParticipantsSeven (4 male, 3 female) unilateral transfemoral amputees capable of community ambulation.InterventionsSubjects performed ten repetitions of sit-to-stand and stand-to-sit with a powered knee-ankle prosthesis and with their prescribed passive prosthesis in a randomized order. With the powered prosthesis, knee and ankle power generation were controlled as a function of weight transferred onto the prosthesis.Main Outcome MeasuresVertical ground reaction force limb asymmetry and durations of movement were compared statistically (Wilcoxon Signed Rank test, α=0.05).ResultsFor sit-to-stand, peak vertical ground reaction forces were significantly less asymmetric using the powered prosthesis (19.3% [11.8%], mean [standard deviation]) compared to using the prescribed prosthesis (57.9% [13.5%]) (p=0.018), where positive asymmetry values represented greater force through the intact limb. For stand-to-sit, peak vertical ground reaction forces were also significantly less asymmetric using the powered prosthesis (28.06% [11.6%]) compared to using the prescribed prosthesis (48.2% [16.0%]) (p = 0.028). Duration of movement was not significantly different between devices (sit-to-stand: p=0.18; stand-to-sit: p=0.063).ConclusionsAllowing transfemoral amputees more control over the timing and rate of knee and ankle power generation enabled standing and sitting with their weight distributed more equally between limbs. Increased weight-bearing on the prosthetic limb may make such activities of daily living easier for transfemoral amputees.



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