Prosthesis Design and Control
Introduction
Fall 2014
Stump, or residual limb
www.vitalitymedical.com
Earliest amputation recorded by Herodotus, Greek historian,
480 BC
Persian soldier Hegesistratus arrested by Spartans, facing torture
and execution, one foot in stocks, cut off foot to escape, later
obtained a prosthetic (wooden) foot
2
Disarticulation: Amputation between bone surfaces
Upper limb amputations: 7%
2%
33%
1%
54%
3%
www.cdha.nshealth.ca
3
Causes of amputation
• Accident – 23%
• Disease or infection – 74%
– Cancer – 2%
– Vascular (circulatory) – 54%
• Diabetes – 70%
– Tripled between 1980 and 2005
– Diabetic survival rate is improving
– 1/3 of adults diabetic by 2050
• Birth defect – 3%
• Paralysis – less than 1%
4
As of 2014:
• 2 million people with limb loss in the United States
• 185,000 amputations in the United States each year
• In 2009, hospital costs associated with amputation
totaled more than $8.3 billion
• African‐Americans are four times more likely to have
an amputation than white Americans
• Nearly half of those who have an amputation due to
vascular disease die within 5 years
• Diabetics who have a leg amputation have a 55% of a
second amputation within 3 years
www.amputee-coalition.org
5
Amputations by age
• Below 10 years old: 3%
• 11-20 years old: 7%
• 21-30 years old: 7%
• 31-40 years old: 7%
• 41-50 years old: 9%
• 51-60 years old: 18%
• 61-70 years old: 28%
• 71-80 years old: 17%
• Over 80 years old: 4%
A Primer on Limb Prosthetics, p. 9
6
Corset-style interface, pre-1960s
Patellar-tendon-bearing socket,
introduced in the 1960s
http://www.studyblue.com/notes/note/n/
rehab-prosthortho-pictures/deck/6884210
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Total elastic suspension belt Pelvic belt
Silesian bandage
http://www.orthoamhs.org.au/Virtual
http://oandplibrary.com
(Silesia is a region in Poland) europe.com/prosthetics/Liners Museum/Surgery/orthopedics/
Limb-prostheses
8
Socket
Socket interfaces
Liner / lock – low activity
Suction – medium activity
Vacuum – high activity
Knee
Shank
Ankle
Foot
www.ottobockus.com
Mechanical interfaces
between leg
components are
standard, which
provides a “plug and
play” prosthesis.
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Gait Cycle: 2 steps = 1 stride
Heel strike
Heel strike
12%
50%
www.jaaos.org/content/15/2/107/F1.large.jpg
10
Lower limb amputee activity levels
• Level 0
– Does not have the ability or potential to ambulate safely and a prosthesis does
not enhance their quality of life or mobility.
• Level 1
– The ability or potential to use a prosthesis for transfers or ambulation on level
surfaces at fixed pace. This prosthesis is typical for the household ambulator.
• Level 2
– The ability or potential for ambulation with the ability to traverse low-level
environmental barriers such as curbs, stairs, or uneven surfaces. This
prosthesis is typical for the limited community ambulator.
• Level 3
– The ability or potential for ambulation with variable pace, with the ability to
traverse most environmental barriers while participating in activities of daily
living that require prosthetic use beyond simple locomotion.
• Level 4
– The ability or potential for prosthetic ambulation that exceeds basic
ambulation skills, exhibiting high impact, stress, or energy levels. This
prosthesis is typical of the child or active adult functioning in the community.
www.health.alberta.ca/documents/AADL-Manual-P-Products.pdf
11
Prosthetic Feet
• More than 50 models available today
• Some design for special activities
• Feet with no hinged parts: Low activity level
Solid ankle cushioned heel (SACH)
www.willowwoodco.com/productsand-services/feet/low-activity/sach
Elastic keel: more flexible
www.heritage-medical.com/foot-prosthetics
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Flex foot
http://www.ossur.com/prostheticsolutions/products/feet/feet/flexfoot-assure
Oscar Pistorius, 2012 South African Olympic sprinter
http://www.dailymail.co.uk
http://www.telegraph.co.uk
13
Articulated Prosthetic Feet
http://www.amputee-coalition.org/militaryinstep/feet.html
iWalk product BiOM
Hugh Herr’s company
http://blog.amsvans.com
Google “Hugh Herr TED”
www.newscientist.com
www.businessinsider.com
14
Odyssey – motorized
1 KHz control
www.springactive.com
JackSpring – motorized
www.springactive.com
Thomas Sugar, Professor
Arizona State University
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Prosthetic Knees
• More than 100 models available
• Single axis or polyaxial
• Passive: no electronics
– Mechanical friction
• Constant
• Variable
– Hydraulic
– Pneumatic
medi OHP3/KHP3
www.medi.de/en/international/products/leg-prostheses
• Active: motor control
• Semi-active: computer control but no motors
• Ottobock, Ossur, Trulife, Freedom Innovations,
Endolite (Dayton, Ohio), …
16
Mauch SNS (swing and stance)
– Ossur
– Passive
– Hydraulic
– $5,000
Hans Adolph Mauch (1906-1984)
German engineer until the end of WW II
Jet engine and prosthesis development in Germany
Moved to USA in 1945
www.ossur.com
17
C-Leg
– Ottobock
– Semi-active
– Hydraulic
– Introduced in 1997
– First microprocessor leg
– $50,000 retail
Otto Bock, 1881-1960
German prosthetist
www.ottobockus.com
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Rheo Knee
• Ossur
• Semi-active
• Hydraulic
• Introduced in 2005
• $17,000
Magnetorheological fluid
has viscosity that depends
on the surrounding
magnetic field
www.stortz-koeln.de
19
Plie Knee
• Freedom Innovations
• Semi-active: 100 Hz
• Hydraulic
www.freedom-innovations.com
20
Vanderbilt Leg
(aka bionic leg, or
Goldfarb leg)
• Freedom Innovations
• Integrated knee and
ankle motors
• Currently in testing
• Controller gain
scheduling depending
on “walking phase”
Image: National Institute of Biomedical Imaging and Bioengineering
F. Sup et al., “Self-Contained Powered Knee and Ankle Prosthesis”
21
Power Knee
• Ossur
• First active
transfemoral
prosthesis
• Introduced in 2009
• $60,000
proklinik.com.tr
22
Increase in energy consumption
• Amputee with walker or crutches – 65%
• Below-knee unilateral amputee – 15%
• Below-knee bilateral amputee – 30%
• Above-knee unilateral amputee – 65%
– Three times normal hip power on amputated side
• Above-knee bilateral amputee – 200%
“Microprocessor Prosthetic Knees,” by D. Berry
“Self-contained power knee and ankle prosthesis,” by F. Sup et al.
23
Coordinate system
Z
Y, right to left
X
Thigh angle
(positive as shown)
Knee angle
(positive)
Direction of walking
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Able-Bodied Gait Data
Heel
Strike
Knee Angle
Degrees
80
60
40
Flexion
Extension
Toe
Off
Flexion
Extension
20
0
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69
Thigh Angle
40
Degrees
30
Stance Phase
Swing Phase
20
10
0
-10
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69
-20
-30
Vertical Position (mm)
Hip Position
900
850
800
750
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69
Time (Sample Number)
Gait_Data_Sub3.xls, Normal Walk (Cleveland Clinic)
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Able-Bodied Gait Data
Knee Power (W/kg)
2
1.5
1
Positive: Power Generated
by the Joint
0.5
0
-0.5
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69
-1
Negative: Power Absorbed
by the Joint
-1.5
-2
-2.5
Ankle Power (W/kg)
2.5
2
1.5
1
0.5
0
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69
-0.5
-1
Does not match published data well
-1.5
Gait_Data_Sub3.xls, Normal Walk (Cleveland Clinic) -113.8 kg subject
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Toe
Off
“Energy generation and absorption at the ankle and knee
during fast, natural, and slow cadences,” by D. Winter, 1983
Figure 3 and Table 1
Able-Bodied Gait Data
Power = Torque * (Angular Velocity)
Normal walking speed
104.4 steps/minute
(52.2 strides/minute)
Ankle work = –7.8 + 25.6 = 17.8 J
Knee work = –6.3 + 3.7 – 9.6 – 8.4 =
–20.6 J
The ankle requires energy
The knee absorbs energy
The net work done by the
knee/angle combination is negative
Discriminating age and disability effects in locomotion: neuromuscular
adaptations in musculoskeletal pathology, by Chris A. McGibbon and
David E. Krebs
27
Kinematic and kinetic
comparisons of
transfemoral amputee gait
using C-Leg® and Mauch
SNS® prosthetic knees, by
Ava D. Segal et al.
2
1
4
3
Prosthetic Limb
C-leg: solid line
Mauch leg: dashed line
Control group: dotted line
1.
2.
3.
4.
More hip power required for amputees
No stance knee flexion in prostheses
More negative knee power in prostheses
No ankle push-off with prostheses
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Kinematic and kinetic
comparisons of
transfemoral amputee gait
using C-Leg® and Mauch
SNS® prosthetic knees, by
Ava D. Segal et al.
1
2
Intact Limb
C-leg users: solid line
Mauch leg users: dashed line
Control group: dotted line
3
1. Limping (shorter steps) by amputees
2. More hip power in amputees
3. More ankle push-off by amputees
ancillary
health
issues
29
Prosthetics Research at CSU
• Fall 2009 – Davis and van den Bogert (CC) contact Simon
about hydraulic prosthesis control
• Spring 2010 – CC provides funding to CSU
• Summer 2010 – Davis leaves CC for Austen BioInnovation
• Fall 2010 – van den Bogert leaves CC for self-employment
• Fall 2011 –Richter begins design of hip robot
• Spring 2012 – Richter completes hip robot
• Fall 2012 – CC project concludes
• Fall 2012 – van den Bogert moves to CSU
• Summer 2013 – Wright Center funds CSU for 1 year
• Fall 2013 – NSF funds CSU for 4 years
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