Functional performance differences between the Genium and C-Leg prosthetic knees and intact knees.

INTRODUCTION Studies of functional performance incorporating activities of daily living (ADLs) in persons with transfemoral amputation (TFA) are limited. Seymour et al. evaluated the performance of persons with TFA using two different prosthetic knees on an obstacle course simulating a home environment during loaded and unloaded conditions [1]. Subjects walked over varying surfaces (e.g., rug) and around objects (e.g., trash can) commonly found within a home setting with hands free or while carrying a laundry basket. When subjects used a C-Leg (Ottobock; Duderstadt, Germany) microprocessor prosthetic knee (MPK), they completed the obstacle course more quickly and with fewer steps than when they used non-microprocessor knees (NMPKs). Similarly, Meier et al. designed a customized obstacle course involving many mobility skills including basic ambulation, stepping up, ramp ascent, turning, and walking across variably resistive surfaces [2]. C-Leg use tended to improve task completion time relative to a hydraulic swing-phase control polycentric knee. Task completion times were not so clearly improved relative to a single axis, fluid-controlled swing and stance knee system. Meier et al. found that use of the C-Leg decreased movement efficiency by 10 percent while completing the obstacle course in parallel with a mental loading task [2]. Course completion data regarding time and distance were very fractionalized. This likely increased group variance, clouding the ability to measure differences between conditions. Further, a curb step was used and referred to interchangeably as a "stair section" and "step section," which introduces some confusion and may not accurately reflect stair gait function. Nevertheless, Meier et al.'s data conflict with Seymour et al. and others, showing that C-Leg MPK usage increases walking speed during obstacle course performance, flat ground, and stairs [1-3]. Further, a recent systematic review's findings support improved gait efficiency with C-Leg MPK use in laboratory walking tests [4]. Given the uncertainty between obstacle course completion time relative to prosthetic-knee type, considering complex walking terrains were used in one study [2] and household floor surfaces in another [1], further assessment of household and functional tasks with MPK use is needed. Such assessments should more optimally test levels of activity and participation in accordance with the International Classification of Functioning, Disability and Health, as opposed to assessing at the body function and structure level. Singular task assessments (e.g., how fast a person walks over flat ground) test performance at the body function and structure level [5-6]. While individual task assessments provide insight into prosthetic optimization and success with specific singular tasks, assessment at higher activity levels and participation will provide greater insight into the integration of a prosthesis into a person's ADLs and their overall functional capabilities. Theeven et al. designed the Assessment of Daily Activities Performance in Transfemoral Amputees (ADAPT), a 17-item assessment scored by activity completion time and perceived difficulty [7]. The ADAPT's functional activities include simulated shopping, obstacle avoidance, stairs, and other community-based functional tasks. Theeven et al. report high test-retest reliability and sensitivity to change. Investigators evaluated performance on the ADAPT in persons with TFA who ambulated at fixed cadence [6]. Subjects used two MPKs (C-Leg, Compact [Ottobock]) compared with their prestudy NMPK systems. When analyzed by entire sample, no difference in functional performance was found between knee conditions despite reporting the instrument's sensitivity to change. The investigators attributed this to high within-group variability. When stratified into functional subgroups (e.g., low, intermediate, and high function), high and intermediate functioning persons with TFA completed sections of the ADAPT significantly faster with C-Leg and Compact knee prostheses versus NMPKs. …