The fit of the residual limb within a prosthetic socket is a primary concern for many
amputees. A poor fit can lead to skin irritation, tissue breakdown, and pain. Further,
amputees with diabetes or vascular dysfunction often have difficulty maintaining healthy
residual limb tissue; a condition that could be mitigated by the application of negative
pressure (i.e., vacuum suspension). The aim of this research is to characterize the
residual limb response to a vacuum suspension system and to measure prosthetic performance
in comparison to a typical suction suspension system.
The proposed research plan involves two sets of human subject experiments: (1) prospective,
randomized cross-over study to quantify performance of a vacuum suspension system as
compared to a total surface bearing suction socket in terms of pistoning, maintaining limb
volume, step counts, and subjective measures of fit and (2) measurement of transcutaneous
oxygen tension as a function of vacuum pressure.
A proper fitting prosthetic socket provides the amputee with a comfortable system allowing
them to pursue many of their desired vocational and recreational goals. Unfortunately, many
amputees live with an ill-fitting socket and can experience limb pistoning within the
socket, which in turn may result in skin irritation, tissue breakdown, discomfort, and a
reduction in activity. One of the key factors affecting fit is intraday residual limb
volume changes. For an amputee with dysvascular conditions, the implications of a poor
fitting socket are exacerbated by poor circulation, reduced healing potential and the
compressive forces exerted by their prosthesis.
Vacuum suspension systems may have the potential to alleviate these conditions for healthy
and dysvascular amputees. The purported benefits of vacuum suspension systems include, but
are not limited to: improved suspension (reduction in the amount of pistoning), maintenance
of limb volume throughout the day, and increased tissue oxygenation to the residual limb.
Our first objective is to characterize performance, as related to socket fit, of a vacuum
suspension system using objective and subjective measures. We will do this by conducting a
within-subject experiment to measure pistoning in three dimensions while walking, overall
and regional changes in limb volume before and after a thirty-minute treadmill walk,
mobility (step counts) and the perception of socket fit (questionnaire) as a function of
prosthetic prescription (vacuum suspension system vs. total surface bearing suction socket).
Our second objective is to determine the effect of pressures within a prosthetic socket on
residual limb transcutaneous oxygen tension (tcpO2) levels. We will conduct
laboratory-based, in situ testing to determine how the transcutaneous oxygen tension levels,
at six sites on the residual limb, respond to pressures simulating those within a vacuum
suspension system and a total surface bearing suction socket.
The proposed research will allow us to understand how suspension systems influence
prosthetic socket fit and residual limb tissue health and to formulate a knowledge base on
two suspension systems providing prosthetists and clinicians the objective data to make
better prescription decisions. In addition, the methods utilized in this study (e.g., a
residual limb limb volume scanner and assessing dynamic pistoning) can be used to study
current and novel suspension systems, liners, and prosthetic socket designs to provide a
standard for comparison.
- Over 18 and less than 70 years of age,
- Have a below knee amputation involving only one side,
- If the cause of amputation was for traumatic reasons and do not have diabetes or a
vascular condition, the amputation must have occurred at least six months ago and the
potential subject must have worn a prosthesis for at least four months,
- If the cause of amputation was for diabetes or vascular reasons, the potential
subject must have been fit with a prosthesis and have worn it for at least one year,
- Wear the prosthesis for at least 6 hours a day,
- Able to walk without a cane, crutches, or a walker,
- Are moderately active enough to walk at a steady pace for at least 30 minutes.
- Have pain in legs or any condition that interferes with walking.
- Have an ulcer on the residual limb,
- If potential subject had an amputation because of a tumor or an infection, no longer
have an active tumor or undergoing treatment for a tumor,
- Have fallen within the last 3 months.