Use of Passive, Adaptive, and Active Prosthetic Knees in Persons With Unilateral, Transfemoral Amputation

An interrupted time-series trial with pre/post baseline assessments, randomized crossover of interventions, and within-phase repeated measures is used to evaluate and compare the effectiveness of the Össur Power Knee II and the Össur Rheo Knee in individuals with unilateral, transfemoral amputation. A rigorous and clinically-meaningful experimental protocol is applied to verify study participants receive appropriate training, experience, and assessment in each knee condition. A suite of standardized and ad-hoc physical performance tests, patient-reported questionnaires, and monitoring technologies were carefully selected to assess important, clinically-relevant participant outcomes. Comparative effectiveness of three prosthetic knee interventions are evaluated using direct measurement (i.e., timed tests), observed clinical ratings (i.e., subjective assessments of gait quality) and self-report instruments (i.e., health status surveys). Analyses will focus on identifying differences between control system technologies inherent to each type of prosthetic knee (i.e., passive [mechanical], adaptive [magnetorheological], and active [power]). Outcomes will be used to establish recommendations for which activities and patients knees are most appropriate or likely to produce a desired effect.

Inclusion criteria

• age 45 - 75
• body weight less than 275lbs
• unilateral amputation between the hip and knee
• amputation due to non-vascular causes
• no other major limb amputations
• amputation occurred at least 2 years prior
• stable limb volume (i.e., at least 6 months on an unmodified prosthetic socket)
• intact skin tissue without open wounds or sores for at least 2 months
• physiologically stable medical condition (i.e., non-degenerative)
• possession and regular (i.e., daily) use of a prosthesis with a prosthetic knee with non-microprocessor (i.e., mechanical or fluid) stance control
• Medicare functional classification level (MFCL or "K-level") 3

Exclusion criteria

• expect to receive or are expected to require a replacement prosthetic socket within 15 months
• complete reliance on an assistive device (i.e., cane or walker) for ambulation