The document discusses different types of prostheses used to replace missing limbs. It describes exoskeletal and endoskeletal prosthetic designs, and covers the basic components and classifications of prostheses. Myoelectric prostheses that use muscle signals and various types of feet - including SACH, Jaipur and dynamic response feet - are explained. The document provides details on prostheses for transtibial and transfemoral amputations, including PTB and quadrilateral socket designs and considerations for bilateral transfemoral amputees.

1. Dr. Sanjib Kumar Das, Fellow Doctoral
MPT (Musculoskeletal Disorders)
PhD (Ergonomics & Human Factors)

2. Prosthetics
• Prostheses are used to replace a missing limb and to
restore or provide function.
• They are manufactured by a prosthetist and fit on a
custom made basis on to the patient.
• Ideally, prosthesis must perform its function, be easy
to maintain, don and doff, be comfortable to wear,
and it should preferably be light weight, durable, and
cosmetic to look at.

3. Classification of Prosthesis
Prosthetic Construction Design
Exoskeletal Endoskeletal

4. Exoskeletal Prosthesis
• An exoskeletal prosthesis gains its structural
strength from the outer laminated shell, through
which the weight of the body is transmitted.
• This shell usually made of a resin socket, which is quite durable,
over a filler material of wood or foam, and the whole prosthesis
is shaped to provide a cosmetic appearance of the amputated
limb.
• The opposite surviving leg is taken for reference for shape
length and skin color.

5. Endoskeletal Prosthesis
• It gains its structural integrity from the inner
endoskeleton—a pylon made of metal or carbon
fibre, which is a light internal modular component
to provide weight bearing.
• The cosmetic appearance is provided by shaped
foam covers slipped over the modular components.
• Advantages of this design include the ease of
alignment of the components and their adjustments,
and the ability to interchange components by
removing the foam cover.
• The disadvantage of this design is that the foam
cover is not very durable and needs to be replaced
often.

6. Components of a Prosthesis
The basic components of prosthesis are:
• Socket made of plastic or resin
• Body of the prosthesis
• Harness/suspension system
• Control system (not relevant to lower limb prostheses)
• Terminal device: For the upper limb the terminal device is the hand
and for the leg it is the foot.

8. Terminal devices are classified as:
• Cosmetic hands
• Body-powered hooks and hands
– Voluntary opening (VO)
– Voluntary closing (VC)
• Externally powered hooks and
hands.
• Myoelectric
– Digital
– Bionic arm

10. Myoelectric Prosthesis
• A myoelectric prosthesis uses signals or
potentials from muscles through
electromyography, within a persons
stump.
• The signals are picked up by electrodes
on the surface of the skin which activates
a battery-driven motor that operates a
prosthetic component, like the finger.
• Control of the motor regulates the extent
or speed of the prosthesis, such as elbow
flexion or extension, or opening and
closing of the fingers of the terminal
device

11. Advantages
• Use of natural muscle stimuli.
• More accurate control with less energy expenditure.
• Eliminates the shoulder harness & decreased body movement to
control prosthesis.
• The myoelectric prosthesis provides more mobility, pinch force,
and cosmetic appearance than body powered prostheses.
Disadvantages
• They are very expensive
• In the event of a breakdown, it needs very skilled technical backup
to repair.
• Also they need servicing on a regular basis
• The energy source is from a battery, which would have to be
recharged regularly.
• Myoelectric components may get dysfunctional in water or around
magnetic or electronic fields.

14. BK prosthesis for transtibial amputations: PTB prosthesis
• The patellar tendon bearing (PTB)
socket is the standard transtibial
socket. It is a laminated plastic
socket.
• The body weight has to be taken on
the patellar tendon.
• A part of the weight is borne over the
condylar flares.
• Areas of relief from pressure include
the head of the fibula, the distal ends
of both the tibia and the fibula, and
the shin.

15. PTB prosthesis
• The proximal posterior wall of the socket
bulges posteriorly to allow for the muscle
bulk.
• The level of this wall must be low enough to
allow the client to sit with the knee flexed at
least 90° degrees, yet high enough to prevent
undue bulging of flesh over the brim.
• The proximal edge is rounded to prevent sharp
pressure on the back of the knee; grooves are
provided at the medial and lateral corners for
the hamstring tendons.
• The anterior wall reaches to patellar level and
has a shelf that corresponds to and shifts the
weight on the patellar tendon. The medial and
lateral walls reach approximately to the level
of the adductor tubercle.

16. AK prosthesis for trans femoral amputations
The Quadrilateral Socket
• It is named for its four walls that have a specific
function.
• Distally, the socket is contoured to provide total
contact for the residual limb.
The Posterior Wall
• Most of the weight is borne along the posterior
wall. The ischial tuberosity and some gluteal
muscles rest on top of the wall, which is thicker
medially than laterally.
• Internally, the wall is contoured for the hamstring
muscles, while externally, it is flat to prevent
rolling of the thigh in sitting.
• The height of the posterior wall is determined by
the position of the ischial tuberosity.

17. AK prosthesis for trans femoral amputations
The Anterior Wall
• It rises about 5 cms above the height of the posterior wall.
• It is convex laterally to allow space for the bulk of the rectus
femoris muscle.
The Lateral Wall:
• The lateral wall is as high as the anterior wall.
• Inside, the wall inclines medially to set the residual limb in about
10° of adduction. The lateral wall is contoured to distribute pressure
evenly over that side, and bear some of the weight.
The Medial Wall:
• Is vertical and prevents medial movement of the residual limb
within the socket, especially during stance.
• A relief channel is built into the corner of the medial and anterior
walls for the adductor longus tendon.
• The medial wall and the posterior wall are of the same height.
• Hitching on the pubic ramus, which causes a lot of irritation, is
avoided by lowering the medial wall.

18. Bilateral Transfemoral Amputations Stubbies
• Stubby prostheses or “stubbies” are generally
prescribed only for individuals with bilateral
transfemoral AK amputations who are
motivated to ambulate but who are not
candidates for fitting with full length prostheses.
• They are most effective for individuals with
short residual limbs.
• Stubby prostheses do not have any knee joints.
They have above knee sockets, as with AK
prosthesis and to prevent the wearer from
falling backward are provided with modified
rocker bottom feet.

19. Bilateral Transfemoral Amputations Stubbies
• They are shorter than the original limbs, to bring down the
center of gravity, and thereby increase stability.
• Stubbies allow easy balance and the patient walks with
lesser expenditure of energy.
• Ambulation causes exaggerated truncal rotation. Short
canes or crutches are usually needed for support.
• Sitting in a chair and climbing stairs are little difficult
because of shortness of prosthesis.
• Many people find stubbies cosmetically unacceptable
because of the extreme reduction in height.

21. Multiaxis Feet
• Single axis feet allow movement of the foot in one
axis, up and down.
• Multiaxis feet move up and down as well as side to
side to conform to uneven surfaces better than single-
axis feet.
• Multi axis feet have ankle motion, which absorbs the
stress of walking, reducing wear and tear on the
prosthesis.

22. Non dynamic Response Feet
Solid Ankle Cushion Heel
• The solid ankle cushion heel (SACH) foot is a non-
articulated device with a solid wood, a sponge rubber heel
wedge, and a moulded cosmetic forefoot with or without
individual toes. Mild hyperextension of the rubber toe
and forefoot is possible in late stance and push off.

23. Jaipur Foot
• The SACH foot has disadvantages that it has to be
used only with shoes since the shapes of the toes are
not discernible.
• In India, where barefoot walking is prevalent in
villages, together with the practice of not wearing
shoes inside the homes and temples, it was but natural
that there was a need for a cheap alternative to the
SACH foot which would also be cosmetic.
• It was developed at SMS Medical College, Jaipur by
Prof PK Sethi and team.
• It provides bare foot walking. The foot and ankle
assembly is made of rubber material.
Advantages
• Cosmetically well-accepted in the rural population who prefer barefoot ambulation.
• The elasticity of the rubber provides enough dorsiflexion to permit an amputee to
squat, transverse rotation of the foot on the leg to facilitate walking and cross- legged
sitting, and sufficient range of inversion - eversion to allow the foot to adapt itself
while walking on uneven surfaces.
• Exterior is made of a waterproof durable material, for work in fields
• Less expensive
• The raw material is locally available.

28. Dynamic Response Feet

29. Thank You
Dr. Sanjib Kumar Das, Fellow Doctoral
MPT (Musculoskeletal Disorders)
PhD (Ergonomics & Human Factors)
Mail: sanjib_bpt@yahoo.co.in
Contact No: +91 8879485847/ 8169951520 (India)