Changes in Internal Prosthetic
Moment with Walking Speed:
A Case Study.
Jason Wening MS, CPO
Mark Kaiser, CO, prosthetic
resident
1
As speed increases…
Gait asymmetry increases. (Isakov et al., 1996)
Peak GRF increases. (Nolan et al.,2003)
Ankle work in both limbs increases.
(Silverman et al., 2008)
Muscle EMG increases, especially at
initial contact. (Fey et al., 2010)
2
Quantifying Dynamic Alignment
Difficult to do with a gait lab. (Van Velzen et al.,
2006)
• Good walkers manage moments well?
• Resolution may not be sufficient?
Roll over shape may be useful. (Hansen )
Alignment is a
6 DoF problem.
3
A new clinical tool:
Compass and Smart
Pyramid
Pyramid with integrated
strain gauges.
Software computes
moments in the sagittal and
coronal planes.
4
Would a moment by any other
name torque the same?
-
+
5
Purpose of this study
Determine how the moment profile from
the Compass System changes with
walking speed for a single subject.
6
Subject
36 y.o. M, R Trans-tibial amputee
K4 level ambulator
Suction TSB socket with gel liner,
dynamic response foot
7
Methodology
Nine walks were collected at a range of
walking speeds in a 20 meter hallway.
Data collected in middle 10 meters.
Velocity computed from 10m walk time.
Moment collected using OI Compass
and Smart Pyramid at 100 Hz.
8
A Matter of Semantics?
-
GRF Posterior to Smart
Pyramid:
Recorded as a negative
moment about the smart
pyramid
in the sagittal Plane
+
40
30
20
Posterior Moment
10
0
- 10 0
0 .1
0 .2
0 .3
0 .4
0 .5
0 .6
0 .7
0 .8
0 .9
1
-20
-30
9
A Matter of Semantics?
-
GRF through Smart
Pyramid:
Recorded as zero
moment about the
smart pyramid
in the sagittal Plane
+
40
30
20
10
0
- 10 0
0 .1
0 .2
0 .3
0 .4
0 .5
0 .6
0 .7
0 .8
0 .9
1
-20
-30
10
A Matter of Semantics?
-
GRF Anterior to Smart
Pyramid:
Recorded as a positive
moment about the
smart pyramid
in the sagittal Plane
+
40
30
20
Anterior Moment
10
0
- 10 0
0 .1
0 .2
0 .3
0 .4
0 .5
0 .6
0 .7
0 .8
0 .9
1
-20
-30
11
Sagittal Moment vs. Time for Stance Phase
Anterior
60
Moment (Nm)
40
20
0
-20
0
0.2
0.4
0.6
0.8
1
-40
-60
Posterior
Time (s) * = compass approved
Velocity (m/s)
0.87
1.04*
1.3*
1.47*
1.6
1.7
1.73
1.86
1.94
12
Coronal Moment vs. Time for Stance Phase
Lateral
15
Moment (Nm)
10
5
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
-5
-10
-15
Medial
Time (s)
Velocity (m/s)
0.87
1.04
1.3
1.47
1.6
1.7
1.73
1.86
13
1.94
0.9
Conclusions
Walking speed changes the moment
profile as recorded by the Compass
System.
With increased speed peak heel and
keel moments increase.
With increased speed, relative timing of
transition across 0 axis did not change.
• Aprox. 33% of stance phase.
14
Discussion
 What is the true quantitative definition of
optimal alignment?
• Is it speed dependent?…..
• Is it device dependent?…..
• Is it patient dependent?…..
 An effort needs to be made to characterize
the Compass system and make that data
available to users.
15
Calling all Prosthetic
Residents
 What is the relationship between:
•
•
•
•
•
•
•
Foot type,
Socket design,
Socket fit,
Limb length,
Age, gender, 2nd condition, time since amputation,
Cause of amputation,
Use of assistive device…
 and internal moment.
16
Acknowledgements
Orthocare
Innovations
17
Peak Toe Mom ent vs. Speed
60
50
Peak Toe Moment (Nm)
40
30
20
10
0
0
0.5
1
1.5
2
2.5
Walking Speed (m /s)
Zero transition occurred at: 32.89% +/- 1% of stance phase
18