Clinical Trial Evaluation:
The Microprocessor Control C-Leg Versus
Traditional Non-microprocessor Transfemoral Prosthesis

Since the inception of energy storing foot technology, the prosthetics industry has not seen as dramatic an improvement in component technology as the introduction of the C-leg. New knee technology such as the C-Leg has been validated in recent investigations throughout the industry. These studies have shown that with use of the C-Leg there is a significant improvement in gait, stamina and psycho-social well-being (Otto Bock, C-Leg Participant, 1997). However, this research has been limited in scope in that it has included neither patient pre and post-C-Leg activity levels nor patient well being in a real world environment.

PRS is currently conducting a research study on the comparison of the C-Leg to a traditional, non-microprocessor (NMP) prosthesis at the time just before, during and after a transition to a C-Leg. The purpose of this research is to provide a comprehensive “real world” view of the microprocessor technology currently available to users. In doing so, we surmise that funding agencies will be better educated in the quantitative and qualitative incentives for increasing access to these beneficial prosthetic technologies.

Currently, we are studying a population of 20 transfemoral (above the knee) amputees in a range of ages and functional levels over two years. In this study, PRS will evaluate each group to determine why people choose, continue to use and prefer one prosthesis over another as well as to document the functional differences between the two systems.

This study will not only highlight the functional capabilities of the C-Leg, it will also highlight the strength of individual choice and preference through all activity levels. As it is designed, the study outcomes will provide clinical data and performance documentation illustrating the C-Leg’s functionality in a real world setting.

Several activities have been determined in order to accomplish this:

• Conduct a clinical trial to emulate a real world situation where 20 patients transfer from a non-microprocessor (NMP) prosthesis to an Otto Bock 3C100, (C-Leg),
• Two unique participant groups; Geriatric (K-2) and Active (K-3-4) in order to capture the different functionality benefits of using the C-Leg system. For each group in this multiphase study, we will collect objective gait and validated preference & satisfaction data. In order to do this, several outcome measurement tools are being used,
• In order to provide quantitative and qualitative data, we will use existing scientifically validated measurement tools and tools developed specifically for this research.
• Quantitative Tools:
  • Amputee Mobility Predictor (AMP), Robert Gailey, PhD PT
• Divided Attention Task, “Walk & Talk”, PRS
• Stair Assessment Index (SAI), PRS
• Hill Assessment Index (HAI), PRS
• Obstacle Course, PRS
• Qualitative Tools:
• Prosthesis Evaluation Questionnaire (PEQ), PRS
• Addendum: Falls & Mental Energy, PRS
• Short Form 36 (SF 36), MOS

Stair Assessment Index (SAI)

The Stair Assessment Index (SAI) is a 14 level ordinal scale that assesses the functional ability of transfemoral amputees for stair ascent and descent. It is being used in the C-Leg study as a physical measurement tool to document different gait styles on the stairs. It was created to address the limitations of existing functional measures and is based on common ascent and descent patterns and assistive device usage. The SAI was developed because current measurement tools were not sensitive enough to determine differences in gait styles from one prosthetic device to another. Measurement tools, such as the Functional Independence Measure (FIM), assess disability on a continuum of dependence and limited independence while the SAI assesses gait patterns reflecting the quality of independence for stair ascent and descent. The SAI is not a validated tool as of yet, but early results show enough sensitivity exists to determine technique differences in one type of prosthetic knee to another in a functional evaluation, thus reflecting qualities of independence.

Hill Assessment Index (HAI)

The Hill Assessment Index (HAI) is a 12 level ordinal scale developed to address different characteristics of hill ascent and descent in preparation for the C-Leg clinical trial comparing different prosthetic knee units. The HAI assesses gait patterns on hills combined with assistive device usage reflecting the quality of independence. Quality of independence is important as multiple prosthetic knees allow the amputee different features of stability and mobility for different levels of function on uneven terrain. The HAI was developed out of a need to document the differences in function with different knee units. This expanded independence scale allows documentation of outcomes which are more comprehensive and accurate. The HAI is not a validated tool as of yet, but initial results in the C-Leg clinical trial show enough sensitivity exists to determine levels of independence and usage of one prosthetic device as compared to another.