The Use of a Pylon Mounted Transducer for Investigating the Gait of Transtibial Amputees
Creators: name: Brink, Justin Robert
Publisher: name: University of Nevada, Las Vegas
Year: 2012

description: Two areas of research interest in the design and use of lower limb prosthetic devices are how foot performance varies with design and how prosthesis alignment affects gait. The current study addressed both of these areas through the use of the JR3 triaxial transducer mounted at the base of the socket. The transducer is an innovative form of instrumentation that measures forces and moments at the end of the socket. Traditional measurement of gait uses a force plate buried in the floor of a gait laboratory. The study established that the transducer offers a viable means of instrumentation for amputee gait. It provides insight into performance differences between energy storing and release feet (ESAR) and SACH (solid ankle cushioned heel) feet with respect to gait kinematics and kinetics. The effects of variations in the anterior-posterior alignment of the foot in the sagittal plane also were examined. 
The prostheses of four unilateral transtibial amputee subjects were instrumented with the transducer by mounting it where the socket is attached to the pylon. The instrument setup was designed to wirelessly transmit data from the transducer to a laptop. This eliminated the need to have subjects tethered to stationary instruments and allowed for data collection of consecutive steps in a range of walking environments. For this study, subjects were instructed to walk on a level surface at a self-selected comfortable speed. Data were recorded to obtain 10 consecutive steps while using both the SACH and an ESAR foot. The walking trial was repeated for several of the feet at three differing alignments: neutral (initial alignment), a shift of the foot +5mm anterior from neutral, and a shift of the foot -5mm posterior from neutral. Effects from varying foot type as well as alignment were examined with respect to stride characteristics, maximum resultant forces and moments, and the maximum moment arm of the resultant force from the center of the transducer; this moment arm was termed the Effective Moment Arm (EMA). 
The different design characteristics of SACH versus ESAR feet led to hypotheses that stride characteristics as well as peak resultant forces, moments, and EMA's would vary between foot types. These hypotheses were examined using transducer data. T-test computations revealed statistically significant differences in all trials. The peak EMA was found to be larger during toe loading for the ESAR feet, and the time spent in stance and the overall gait cycle times were shorter when using the SACH foot. 
It also was hypothesized that variations in alignment would lead to statistically significant differences in stride characteristics, peak resultant forces, peak resultant moments, and EMA's. ANOVA analysis revealed statistically significant differences in the data for all trials. Using statistical analyses, it was found that neutral alignment led to shorter times spent in stance and shorter gait cycle time. With posterior shifts in alignment the moment in the sagittal plane increased during heel loading and, with anterior shifts in alignment, the moment in the sagittal plane increased during toe loading. 
The study established the feasibility of using a triaxial transducer to analyze some of the characteristics of the gait of transtibial amputees. The transducer appeared to be a useful alternative for investigations that typically use force plates in a gait laboratory. Patterns found in the data indicate statistically significant differences between the ways transtibial amputees respond to feet featuring ESAR design versus feet featuring SACH design. Patterns also indicate statistically significant differences when the sagittal plane alignment of the foot is varied in an anterior-posterior direction. Both sets of findings warrant further investigation.