Funded by:

Materials and Methods Cont.

Ultrasound Data Verification: US data accuracy was verified by using a cylindrical socket filled with US gel which eliminated forces acting on the bone from tissues. Vertical motion data from the UTM was compared to the US data. The two data sets were statistically compared resulting in a p-value of 0.67.

Materials and MethodsTesting Configuration: The chicken leg was prepared surgically with a through-knee amputation procedure and contact casted to make the prosthetic socket. Orthogonal US probe ports were created in the socket’s frontal and sagittal planes to allow for three-dimensional imaging of the femur. The prosthetic setup was secured to the base of the UTM, and the physiological model was fixed to the loading head.

Testing Procedure: The UTM load and crosshead position data were recorded while US video of femur movement was recorded simultaneously for each test. We modeled the three primary events of maximal weight acceptance (MWA) using the heel strike (HS), mid-stance (MS), and push-off (PO) FBD’s. The same test was run separately for both probe positions. The primary testing protocols used were position based, set to displace a maximum of 0.3 cm at a rate of approximately 12 cm/min, and force based set to match gait characteristics. We began recording test data after the physiological model was subjected to twenty loading cycles to account for hysteresis of the soft tissue. US video was analyzed and the displacement of the femur from its starting position was measured for each frame.

High Frequency Ultrasound Evaluation of Bone Motion in Prosthetic Sockets

Anil Oberoi1, Logan Didier1, Suraj Pathak1, Dr. D. Patrick O’Neal1, Dr. Anne Hollister2

Biomedical Engineering Department, Louisiana Tech University, Ruston, LA1

z-displacement y-displacement x-displacement

Displacement (cm)

MWA 0.368 0.116 0.048

MS 0.618 0.096 0.044

PO 0.282 0.082 0.072

p-value

MWA and MS 0.0009 0.0341 0.6483

MS and PO 0.0002 0.2962 0.0046

MWA and PO 0.0013 0.0175 0.024

Introduction• There are nearly 2 million people living with limb loss in the United States• Roughly 90% of the 185,000 new amputations performed annually are lower limb

amputees• Prosthetic sockets are made by molding the residual limb, making estimated

adjustments for bone and soft tissue, and then forming a cast from this mold • Current prosthetic socket fabrication methods rely on prosthetists’ subjective

adjustments which may result in a poor fit• Bone and soft tissue motion inside the socket can cause pain and limited stride;

design strategy to control bone movement should result in pain mitigation • Quantitative information about bone and soft tissue movement in the socket is

difficult to obtain in clinical practice• This preliminary study was designed to evaluate the efficacy of ultrasound

measurements of bone motion in relationship to prosthetic devices

Statistical Analysis: Our null hypothesis was that the ultrasound measurements for the maximum z-displacements of each gait phase are not significantly different, and our alternative hypothesis was that the ultrasound measurements for the maximum z-displacements of each gait phase are significantly different. Maximum displacements from phases were compared using two-tailed, paired, student’s T-tests. Because we compared three gait phases and used three T-tests to evaluate each coordinate’s displacement, a Bonferroni correction was applied, lowering the significance level to 0.0017.

ResultsThe statistical analysis yielded significant p-values (≤ 0.0017) for each comparison of maximum z-displacement. Thus the alternative hypothesis that the ultrasound measurements for the maximum z-displacements of each gait phase are significantly different is accepted, and our device is shown to be able to characterize the differences in the motion of the femur during different gait phases.

Discussion•Many prosthetic limb issues could be addressed by a system that can

characterize the tissue and bone displacement inside a prosthetic socket.• The ability to observe bone and tissue dynamics within the socket could allow

the effects of socket designs and prosthesis’ mechanical configurations to be determined• Use of a three dimensional ultrasound system would increase accuracy and

facilitate data acquisition by eliminating the need to run a test for each probe orientation• Further adaptations of the system could be made for diagnostics regarding

upper limb amputees and varying socket types•Mass manufacturing of a total system could make the already cost effective

method easily accessible to consumers

Soft Tissue

Socket

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0.60Displacement of ZY Direction US Data & UTM Data

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Department of Orthopedics, Louisiana State University Health Sciences Center, Shreveport, LA2

Source: http://www.orthopedic.lk