Lecture 1;TRANSTIBIA PROSTHETICS-1.ppt

Introduction to prosthetics
"The general indication for amputation has been
the same since antiquity; Partial or entire
removal of a limb irreparably damaged by
trauma or disease."John H. Bowker, MD
"Well-done amputation surgery is closely
related to successful prosthetic
rehabilitation." John H. Bowker, MD

CAD-CAM
• The late 60's and early 70's saw the active
introduction and advancement of CAD-CAM
(computer aided design, computer aided
manufacturing) for prosthetics and orthotics.
• These systems use laser digitization to transfer
an accurate numerical three dimensional model
of the extremity or residual limb to the (CAD)
computer which is rectified/modified with the
keyboard rather than plaster.

CAD-CAM
• The rectified image is
then transferred via
keystroke to the (CAM)
milling machine which
produces a rectified
positive model.
• The prosthetic socket or
orthosis is then produced
by conventional methods
or by computer aided
vacuum molding.

Principles and Construction Criteria of
the Prosthesis
• The prosthesis will be constructed using the
guidelines of alignment principles both statically
and dynamically in three dimensions to achieve
appropriate stability and as efficient and
comfortable gait as possible:
AP dimension (anterior - posterior; sagittal plane)
ML dimension (medial - lateral; coronal plane)
Transverse dimension (rotational axes between
the coronal and sagittal planes).

Biomechanics and Relationship of the
Residual Limb and Prosthetic Socket
The prosthetic socket has to meet certain basic
functions:
• It has to avoid any damage on anatomy structure
(bones, muscles, and tendon)
• It must be comfortable for the wearer and allow
bony and soft tissue pressure tolerance in specific
areas
• It must suspend the weight of the prosthesis
during swing phase and support body mass
loading during stance phase

Biomechanics and Relationship of the
Residual Limb and Prosthetic Socket
• It must allow for maximal weight bearing and
stability for static and dynamic force transmission
through the residual transected bone to the more
proximal skeletal system
• It must intimately contain the residual limb while
allowing joint range of motion consistent with
normal locomotion at the least energy
expenditure
• It must maintain body segment biomechanics
approximating the most normal and anatomically
aligned posture possible

Analysis of Stump Condition
• “The key to patient comfort is a balanced and controlled
socket environment that never allows a single force or
combination of forces to reach a level of distress and damage
tissue.
• A stump analysis is necessary if we want to choose optimal
socket technology for a patient. Condition of a stump is
influenced by many factors.
• The type of performed amputation, as well as individual
requirements of the patient must be taken into consideration.
• During assessment we need to ascertain stump condition and
also select proper socket technology.
• We have to make sure that our decision is based on the
overall “picture” of the patient.

Properties of a good stump
For every successful prosthetic management
the stump must have these fundamental
properties:
load-bearing
capable of moving around but
painless

Transtibial amputation
Indications
When process requiring ablation cannot be effectively
eliminated by lesser procedures
Severe foot infection, usually related to diabetes
mellitus
severe destruction of soft tissue and bone that
reconstruction or a more distal amputation is not
feasible
L.Mtalo, 2021

Contraindications
• Inadequate vascularity at amputation sites
between the knee and ankle
• Prolonged nonambulatory status
• Dependent rubor or gangrenous changes about
the upper portion of the tibia
L.Mtalo, 2021

TT amputation Goals;
 Obtain primary wound healing
 Avoid infection
 Create a well padded residual limb
 Cylindrical shaped residual limb
L.Mtalo, 2021

TT-Amputation levels
 A- Anatomical diagram
of Tibia and fibula
 B-TT short stump
 C- TT Medium stump
 D-TT long stump

TT Stump Categories
Typical TT stump categories

TT Surgical techniques
 Radiograph of a healed
bone bridge (tibia–
fibula synostosis)
several months
following a transtibial
amputation using the
Ertl approach.

Surgical technique
Nerves
All of the nerves, superficial and deep peroneal,
posterior tibial, saphenous, and sural nerves should be
identified, drawn down, resected, and allowed to retract
at least 3 to 5 cm away from areas of pressure, scar, and
pulsating vessels
L.Mtalo, 2021

Surgical technique
• Bones
 An anterior bevel should be placed on the tibia, to
remove the apex of bone, and to provide a broad,
smooth surface that should help to prevent distal
pain
L.Mtalo, 2021

Assessing Range of Motion and Muscle Length
• Having near-normal range of motion (ROM) in the
remaining joints of the residual limb is essential
for effective prosthetic use
• Persons with recent amputation are much at risk
for developing soft tissue contracture at the joint
proximal to amputation during the preprosthetic
period
L.Mtalo, 2021

Range of Motion (ROM)
When testing the range of motion of the lower
limb joints of the patient, the assessor will know
the mobility limitations or contractures of the
patient, which will have to be taken into account
when manufacturing the lower limb prosthesis or
orthosis
L.Mtalo, 2021

Range of Motion (ROM)
Range of motion is divided in Passive Range of
Motion (PROM) and Active Range of Motion
(APROM)
L.Mtalo, 2021

Principles of Range of Motion test
 The patient has to be comfortably installed in the
position in which the Assessor wants to test the joint
 Always only test one movement at the time
 At the end of the ROM, identify the quality of the end
of motion: soft or hard, provoking pain?
 At the end of the ROM, measure the exact angle of
motion with the goniometer and report the measure on
the assessment sheet
L.Mtalo, 2021

Causes of joint limitation
There are various causes of joint limitation
however we can group the causes into two;
 Reversible causes of ROM limitation
 Non-reversible causes of ROM limitation
L.Mtalo, 2021

Examples of reversible causes of ROM limitation
 Scars or burns that limit the elasticity of the skin
 Retraction of the joint capsule or ligaments
 Muscle shortening : shortening of the muscle performi
ng the antagonist (opposite) movement
Example: knee extension can be limited because the ha
mstrings (performing knee flexion) are too short
 Spasticity (hypertonicity of the antagonist muscle with
stretching resistance, due to a central nervous system d
isorder)
L.Mtalo, 2021

Examples of Non-reversible causes of ROM
limitation
 Calcification or fibrosis of peri-articular structures (ca
psule, ligaments, tendons)
 Destruction of intra-articular structures (articular spac
e)
 Old fixed articular dislocations
L.Mtalo, 2021

• The Thomas test can be used to
assess the tightness or
contracture of hip flexors for
patients with transtibial and
transfemoral residual limbs.
• The patient is positioned in
supine with both limbs flexed
toward the chest and the pelvis in
slight posterior tilt.
• While the opposite limb is
supported in place, the residual
limb is gently lowered toward the
support surface.
• Tightness or contracture of hip
flexors causes the pelvis to move
into an anterior tilt before the
limb is fully lowered

Assessing Joint Integrity and Mobility
 For individuals with transtibial residual limbs, the
alignment and ligamentous integrity of the knee
will be an important determinant of socket design,
suspension strategy, and eventually the dynamic
alignment of the prosthesis
L.Mtalo, 2021

Joint integrity and stability
The special tests used to assess knee function in
those with amputation are the same as those used
to assess joint integrity in individuals with
musculoskeletal dysfunction in intact limbs and
include;
 Valgus/Varus stress test
 Anterior/posterior drawers test
L.Mtalo, 2021

• The medial collateral ligame
nt is loose (Valgus stress test
), if the knee joint can be "op
ened" on the medial side (ins
ide of the leg) (Fig 1 ).

• The lateral collateral ligamen
t is loose (Varus stress test), i
f the knee joint can be "opene
d "on the lateral side (outside
of the leg) (Fig 2 ).

If you can feel movement, th
e patient has a loose or torn a
nterior cruciate ligament (ant
erior drawers test) (Fig 3 ).

If you can feel movement, t
he patient has a loose or tor
n posterior cruciate ligamen
t (Posterior drawers test) (Fi
g 4 ).

Muscle strength
The Oxford muscle scale is used internationally to grade
muscle strength in patients:
0 No movement
1 Slight movement possible
2 Complete range of movement without gravity
3 Complete range of movement against gravity
4 Complete range of movement against gravity with
some resistance
5 Complete range of movement with full resistance
L.Mtalo, 2021

 Knee extensors
 To check the muscle strengt
h of the knee extensors, hav
e the patient sit on a firm su
rface
 Ask the patient to extend hi
s knee while you push it in t
he opposite direction Fig 5
Muscle strength

 Knee flexors
To check the strength of the
knee flexor muscles, ask the
patient to bend his knee whi
le you push it in the opposit
e direction (Fig 6).
Muscle strength

 Hip flexors
To test the strength of the hi
p flexion muscles, have the
patient sit on a firm surface.
Ask the patient to lift up his th
igh from the seat while you
push in the opposite directio
n and assess his strength (Fi
g 7 ).
Muscle strength

 Hip extensors
 To test the strength of the hip ext
ensor muscles, have the patient li
e on his stomach
 Ask the patient to lift his leg a li
ttle and then extend it (moving t
he thigh away from the couch) w
hile you push in the opposite dir
ection and assess the muscle stre
ngth (Fig 8 ).
Muscle strength

 Hip abductors
 To test the strength of the hi
p abduction muscles, have t
he patient lie on his side.
 Ask the patient to lift up the
leg to be tested from the cou
ch, while you push in the op
posite direction and assess
muscle strength (Fig 9 ).
Muscle strength

 Hip adductors
 To test the strength of the hi
p adduction muscles, ask th
e patient to lie on his back
 Ask the patient to press bot
h legs together while you pu
sh in the opposite direction
and assess muscle strength (
Fig 10 ).
Muscle strength

Selection of Socket technology
Selection of the socket technology also
depends on factors that the patient can hardly
influence:
Reimbursement (cost)
Prosthetist´s knowledge and skills
Workshop equipment

At different phases of gait
circle the socket has
different functions:
 Impact movement results
from the heel striking the
ground.
 Pulling movement occurs
during the swing phase
 Rotational movement
occurs during stance
phase
Socket function at different gait cycle

Winning Combination
• Appropriate combination of the liner material
and suspension system regulates or even
reduces those movements.
• Both elements must be individually tailored
according to the needs of the user.
• The residual limb shape, mobility grade, as
well as social and medical background of the
user must be all taken into consideration
before finalizing a selection.

Relationship of the residual limb and
prosthetic socket
• Liner
A liner is important for the
residual limb protection and
for prosthesis adhesion.
It serves as a sort of “second
skin” between the residual
limb and the hard shell of
the socket.
Together with the suspension
system, it reduces friction
movements between the
skin and the prosthetic
socket

TF and TT Residual Limb
• The socket designs for
transtibial and transfemoral
amputations differ.
• The proportion of soft tissue
to bone affects the ability to
withstand pressure load.
• The transtibial residual limb
has two bones with little soft
tissue coverage (see Figure).
• The transfemoral residual limb
has only one bone which is
surrounded by powerful
muscles (soft tissue)

Endoskeleton and exoskeleton
construction
 There are two main different
constructions to build prosthesis.
 Shell construction (exoskeleton)
uses cosmetic cover to transfer
the whole load. That means the
cosmetic cover is a hard
structure.
 The modular construction
(endoskeleton) uses
aluminium/steel tube to transfer
the load. Therefore, the cosmetic
comes in a soft form
Therefore, the cosmetic comes in
a soft form. The modular
construction can be easily
adjusted by a Prosthetist

Knee Centre of rotation according to
Prof. Nietert
• At first sight, human knee might seem to be a kind of a hinge joint
with a fixed axis. However, the reality is quite different. Flexion and
extension of the knee is, actually, a combination of rotation and
sliding induced by anatomical structure.
• If a patient uses a TT prosthesis with a thigh corset, Prosthetist has
to position a mechanical knee centre of rotation in relation to the
anatomical centre of rotation
• If both centers are not congruent (not matching/are overlapping),
the anatomical structure will be damaged over time.
• Also pressure spots can cause a breakdown of the soft tissue/skin.
Location of the centre is particularly important in lower limb
prosthetics and Orthotics.

Compromised knee centre of rotation
• Based on anatomical structures, every patient has
their individual centre of rotation. As this centre
cannot be found individually on the patient, in a
scientific study of Prof. Nietert a so called
compromise centre of rotation has been defined.
• For this purpose, there is a given procedure to
reproduce the knee centre. It is based on
patient´s measurements which are used to
calculate the compromise centre of rotation.
knee-wide AP (Anterior Posterior)
Medial Tibia Plateau (MTP) to the ground

AP knee-wide measurement I
• Take the AP knee-wide
measurement
approximately in the
middle of patella. Divide
it according to the ratio
AP 60/40 (see picture
aside) and mark it.
• --------------
Picture 1: construction
AP direction

AP knee-wide measurement II
• Take the measurement and
calculate 14-17%
(approximately 2cm). If the
patient is a child, take 14%.
For adults 17%. The next
step is to palpate the medial
tibia plateau (grey dot line
in picture 2) and take 14-
17% of AP measurement in
the proximal direction and
mark it.
• ---------------
proximal direction

AP knee-wide measurement III
• This is a compromise
knee centre of rotation.
In the picture 3 you see
the summary of all the
necessary steps.
• ------------------
of knee centre of
rotation

TT Socket Types
• The objective of socket technology is to adapt
the prosthesis as accurately as possible to the
residual limb, also in accordance with the
needs and physiological prerequisites of the
user
• In principle we have two different concepts to
adapt the prosthesis to the stump. We classify
“specific weight bearing” PTB and “total
surface weight bearing” TSB sockets

Specific weight bearing socket (PTB)
• The specific weight bearing
socket is defined by partial
load bearing and load relief
for the residual limb. An
approximate triangular
shape is achieved.
Rotational movements are
controlled with this socket
shape. The idea is to make
use of anatomical structures
to hold the socket in place.
That means we have
different spots with
different pressure on the
stump.

Total surface Bearing socket (TSB)
• With a total surface
weight bearing socket,
pressure is distributed
evenly over the residual
limb.
• The socket shape is
based on the residual
limb cross-section,
which means it usually
tends to be round

Transtibial Residual Limb Skeletal and Soft
Tissue Anatomy
• The following areas indicates bony areas or
protuberances that are, or may be, typically
sensitive and intolerant to pressure.
Depending upon surgical technique, degree of
sensitivity and prominence, these areas are
typically relieved by adding plaster build-ups
of various thickness to the positive plaster
model

Lecture 1;TRANSTIBIA PROSTHETICS-1.ppt

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