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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_921_Библиотеки_им_академика_М_И_Перельмана
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Section 2: Upper Limb
Figure 8
prosthesis from the Civil War era. (Courtesy of
Figure 7
arm, 16th century, Weimar, Germany. (Copyright Peter Finer, myArmoury.com.)
Figure 9
mission from Se lpho W, inventor: Construction of a rticial hands. US Patent 18021. August 18, 1855.)
Photograph of Götz’s articial
Patent drawing for a c able-controll ed prosthesis led in 1857. (Reproduced w ith per-
functional upper limb prosthetic devices. As early as the 16th century and
continuing through the US Civil War,
hook-like shapes were often fashioned
as useful prosthetic implements for stabilizing, pulling, and carrying objects4
(Figures 7 and 8). Patent filings in
the 19th century document the use of
body-powered control through a harness, such as William Selpho’s 1857
patent for a body-powered prosthetic
5,6
arm
(Figure 9).
Cowan’s Auctions, Cincinnati, OH.)
and Dorrance designs demonstrate the
use of a harness to both suspend and
activate a cable that is pulled to open a
terminal device.
Building on these original concepts,
methods of efficiently transmitting force
through a harnessing system have been
developed and refined. To better understand these concepts, it is useful to
review force transmission and goals of
efficiently harnessing a body-powered
system.
Photograph of a transradial
The primary body-powered system
still currently in use can be attributed
to David W. Dorrance’s 1912 patent of
the split hook.7 The original hook design
(Figur e 10) was refined into multiple
models and shapes and is currently sold
by the Hosmer Corporation (formerly
Hosmer Dorrance).8 Both the Selpho
Basic Concepts of Force
Transmission
The goal when setting up body-powered
prostheses is to create a transmission
of force in the most efficient manner
possible. To achieve this, the following
criteria must exist: (1) The prosthesis
must be securely suspended or anchored
to the individual’s body. (2) There must
be a harness and cabling system designed to transmit body movements to
efficiently activate a terminal device. (3)
There must be an available power source
in the form of movement generated by
an intact body segment that can activate
a body-powered component. (4) The
body movement must be able to travel
a sufficient distance to complete the action with adequate force to achieve the
desired outcome.
Figure-of-8 Harness System
The figure-of-8 harness system has several key component parts (Figure 11).
Axilla Loop
The foundation of the figure-of-8 harness is the axilla loop, which is also
known as the anchor because this portion of the harness acts to both suspend
the prosthesis and provide a stable anchor for the user to generate power to
activate the terminal device. The axilla
loop is located through the contralateral
deltopectoral groove.
Suspension
The portion of the harness that is
responsible for immediate vertical
suspension is called the anterior suspensor strap. It starts at the anchor,
which is located at the contralateral
shoulder, and ascends superiorly and
laterally until it reaches the ipsilateral
deltopectoral groove. The strap descends and is attached to the inverted
Y strap, which connects the harness to
the proximal aspect of the triceps cuff.
Control Strap
The control strap travels from the proximal axilla strap across the inferior aspect
of the ipsilateral scapula. This portion of
the harness connects to the cabling system that ultimately activates the terminal device. The orientation of the strap
is an approximate 45° angle that travels
over the distal portion of the ipsilateral
Atlas of Amputations and Limb Deciencies, Fourth Edition © 2016 American Academy of Orthopaedic Surgeons
162
scapula. This strap is referred to as the
control attachment strap.
Harness Center Point
There are two common methods for creating the center point of the harness–a
static sewn point and a stainless steel
ring juncture (Figure 12). The ring style
is designed to offer more range and flexibility of movement. The optimum location of the center juncture point is at
midline and distal to the C7 vertebra.
Juncture Between the Harness
and the Cable System
Attached to the end of the control attachment strap is the proximal end of a
cable. The cable travels through a metal housing that acts to create a smooth
and continuous fulcrum. To ensure
the housing maintains its shape, it is
anchored at two reaction points in the
system. The reaction points consist of a
proximal cross bar and an attachment
tab emanating from the triceps cuff and
a distal baseplate and retainer on the
forearm of the prosthesis (Figure 13).
This continuous cable approach is
termed a Bowden housing cable system.
A key feature of the Bowden cable
system is that it has a fixed length of
cable housing. This ensures that the captured force and excursion at the harness
are efficiently transferred to the terminal
device. The two reaction points ensure
that the housing maintains the same
curvature as the prosthesis is being
activated, functioning as a smooth and
continuous fulcrum for the cable as it
travels through it. With an appropriate
amount of curvature, there is an optimal
distribution of the friction caused by the
cable traveling through the housing.
9
Chapter 12: Harnessing and Controls for Upper Limb Body-Powered Prostheses
Figure 10
tesy of Fillauer, Chattanooga, TN and Dorrence DW, inventor: Split hook. US Patent 1042413. 1912.)
US patent drawing from David W. Dorrance’s 1912 patent of the split hook. (Cour-
Power Generation
The body movements available to activate a body-powered component are
dependent on the level of amputation.
As a general rule, the more distal the
amputation, the more options remain
available for body activation. At the
Figure 11
view.
Component parts of a standard gure-of-8 harness. A, Anterior view. B, Posterior
© 2016 American Academy of Orthopaedic Surgeons Atlas of Amputations and Limb Deciencies, Fourth Edition
163
Section 2: Upper Limb
Figure 12
point can be sewn together (A) or connected by a ring (B). (Reproduced from Pursley RJ: Harness
patterns for upper-extremity prostheses, in Orthopaedic Appliances Atlas. Chicago, IL, American
Academy of Orthopaedic Surgeons, 1960, pp 125-160.)
Figure 14
that glenohumeral exion is a primary control
motion for body-powered prostheses. (Reproduced with permission from Below and Above
Elbow Harness and Control System. Evanston,
IL, Northwestern University Prosthetic-Orthotic Center, 1966.)
transradial level, the two key movements in body-powered activation are
glenohumeral flexion of the ipsilateral
shoulder and biscapular abduction. In
the former, as the upper arm translates
forward, the cable is pulled and the
terminal device opens. Relaxing this
movement allows the rubber bands on
the voluntary-opening terminal device
to close. This movement generates excellent force and is a key prime mover
in body-powered activation (Figure 14).
Illustrations s howing two variations f or creating the harness center p oint. The cross
Illustration demonstrating
Figure 15
lateral scapular abduction, which represents
an additional control motion for body-powered
prostheses. (Adapted with permission from
Below and Above Elbow Harness and Control
System. Evanston, IL, Northwestern University
Prosthetic-Orthotic Center, 1966.)
Illustration demonstrating bi-
very useful when operating close to the
body and when the user desires to open
the terminal device while keeping it in a
stationary position (Figure 15).
The movements of glenohumeral
flexion and biscapular abduction can
be used discreetly or simultaneous in
combination. The activation movement
chosen depends largely on the location
in space at which the user would like to
activate the terminal device.
With biscapular abduction, the user
moves both scapulae in opposing directions. This widens the back and thereby
creates tension on the cable that opens
the terminal device. This movement is
The Relationship Between
Force and Excursion
The power the body must generate to
activate a terminal device is referred to
Figure 13
attachme nt tab emanating from the tri ceps cu
(top illustration) and base plate and retainer on
the forearm of the prosthesis (bottom illustration). (Reproduced with permission from Below
and Above Elbow Harness and Control System.
Evanston, IL, N orthwestern Universit y Prosthetic-Orthotic Center, 1966.)
Illustration of the cross bar and
as the force needed for activation. The
distance the intact segment of the body
must travel is known as the excursion
needed for activation. These concepts
are illustrated in the two previously
described examples of body activation.
Glenohumeral flexion produces both
substantial force and excursion. The
ipsilateral shoulder muscles generate
excellent force and can travel a substantial distance. In contrast, biscapular abduction generates good force but
more limited excursion because there is
a smaller distance the two scapulae can
travel when generating the movement.
10
The force-to-excursion quotient is
less of an issue with more distal amputation levels because of the multiple
sources of power and excursion available relative to more proximal levels of
amputation when sources of power and
excursion are more limited.
Complete Transradial
System Activation
Figures 16 through 19 demonstrate the
elements involved in the activation of a
complete transradial prosthetic system
in an individual with a bilateral transradial amputation. Action starts from
a figure-of-8 harness that anchors the
Atlas of Amputations and Limb Deciencies, Fourth Edition © 2016 American Academy of Orthopaedic Surgeons
164
Chapter 12: Harnessing and Controls for Upper Limb Body-Powered Prostheses
Figure 16
an individual with bilateral transradial prostheses. (Courtesy of David B. Rotter, CPO, Scheck
and Siress, Chicago, IL.)
Figure 19
activation of a terminal device using biscapular abduction, which allows the hook to stay
close to the body. (Courtesy of David B. Rotter,
CPO, Scheck and Siress, Chicago, IL.)
Posterior photo graphic view of
Photograph demonstrating
system (Figure 16). Beginning at a state
of rest (Figure 17), ipsilateral glenohumeral flexion produces the force and
excursion to open the hook (Figure 18).
Alternatively, biscapular abduction can
be used to activate the terminal device
when positioned closer to the body
(Figure 19).
In a resting position and in a fully
activated position, the cable housing
maintains a gentle curvature. An efficient system maintains this curvature
throughout all motions. If the cable
housing is too tight, unnecessary friction is created; this causes discomfort
for the user and reduces efficiency. If the
Figure 18
Figure 17
transradial prosthesis in the resting state. Ipsilateral gleno humeral exion pro duces the force
and excursion needed to open the hook. The
arrows point to the t wo reaction points, one on
the triceps cu and one on the socket. (Courtesy of David B. Rotter, CPO, Scheck and Siress,
Chicago, IL.)
Figure 20
for a transradial prosthesis. (Adapted from Pursley RJ: Harness patterns for upper-extremity prostheses, in Orthopaedic Appliances Atlas. Chicago, IL, American Academy of Orthopaedic Surgeons,
1960, pp 105-128.)
Photograph of a patient with a
Illustrations showing the anterior (A) and posterior (B) views of a shoulder harness
housing has too much curvature, more
force is needed to activate the system
and efficiency is lost. Regardless of the
level of amputation or the complexity of
the prosthetic system, these basic rules
of cabling apply. To further promote efficiency, modern cabling systems can
be set up using a Teflon (DuPont) lining
inside the housing and efficient, tightly woven steel or spectra cable. These
combinations act to minimize unwanted friction and improve the overall
efficiency of the system.
which the terminal device has been opened
as a result of glenohumeral exion. (Courtesy of David B. Rotter, CPO, Scheck and Siress,
Chicago, IL.)
pressure in different locations other
than the contralateral deltopectoral
groove and the axilla. This design
was constructed for individuals who
do heavy lifting with their prostheses. Prolonged heavy loading can
make wearing a traditional figure-of-8
harness very uncomfortable because
there is constant stress pulling into
the contralateral axilla. The shoulder
saddle design shifts the weight to the
ipsilateral shoulder and the contralateral chest wall. When constructing
Photograph of a prosthesis in
this type of harness, the goal is to
Alternative Harnessing Options
Shoulder Saddle Harness
The purpose of a shoulder saddle
harness configuration is to distribute
ensure that there is adequate surface
area on the saddle and chest strap to
distribute the pressure where it can
be comfortably tolerated (Figure 20).
© 2016 American Academy of Orthopaedic Surgeons Atlas of Amputations and Limb Deciencies, Fourth Edition
165
Section 2: Upper Limb
Figure 21
ing a transradial Michigan roller harness. (Courtesy of Jack E. Uellendahl, CPO, Hanger Clinic,
Phoenix, AZ.)
Figure 23
of a patient wearing a gure-of-9 harness used
with a self-suspending transradial prosthesis.
(Courtesy of Jack E. Uellendahl, CPO, Hanger
Clinic, Phoenix, AZ.)
Photograph of a patient wear-
Posterior photographic view
Michigan Roller Harness
A variation on the shoulder saddle
design is the Michigan roller harness,
which uses cable and housing instead of
static straps to attach to the triceps cuff.
The purpose of this harness design is to
allow a greater degree of unrestricted
movement about the ipsilateral shoulder
(Figure 21).
Harness With Distal Strap
A harness design with a distal strap is
intended to position the center of pressure on the contralateral chest wall, well
distal to the axilla. This heavy-duty harness distributes most of the weight over
the saddle portion of the harness. The
additional straps ensure the counterforce point on the contralateral chest
wall stays distal to the axilla (Figure 22).
Figure 22
der saddle harness that uses a distal circumferential strap to position the chest strap well distal of
the contralateral axilla. (Courtesy of Jack E. Uellendahl, CPO, Hanger Clinic, Phoenix, AZ.)
Figure 24
the use of elbow exion as a prosthetic control motion. (Courtesy of Bob Radocy, MS, TRS, Boulder,
CO.)
Figure-of-9 Harness
A figure-of-9 harness is used when the
socket is designed to be self-suspending.
Self-suspension can be accomplished
through a variety of socket designs,
including an anatomic supracondylar
suspension or pin suspension using a
roll-on liner. Because the harness is not
needed to suspend the socket, the anterior suspensor strap is eliminated, giving the harness the look of the number
nine (Figure 23).
When using a figure-of-9 harness,
the primary body-powered activation
movements remain glenohumeral flexion and biscapular abduction. Based
on his personal experience using voluntary-closing devices, prosthetic designer Bob Radocy identified alternative
methods of terminal device activation,
including elbow flexion (Figure 24).
To take advantage of these alternative
movements, the reaction point is placed
Posterolateral (A) and anterior (B) photographic views of a variation on the shoul-
A and B, Photographs of a gure-of-9 socket and harnessing variation that allows
on the posterolateral aspect of the socket, close to the juncture where elbow
flexion and extension take place. This
allows a fine pinch movement that can
be used to regulate the pressure exerted
on an object with a voluntary-closing
terminal device.
Another use of the figure-of-9 concept is the Anchor device (Single-Handed Solutions, distributed by TRS), which
was developed by Debra Latour, a registered occupational therapist. Latour,
who herself has a congenital transradial
limb deficiency and has been a lifelong
prosthesis user, devised the Anchor
to relieve the need for a harness loop
around the contralateral axilla while still
maintaining body-powered activation.
Using medical grade adhesive, a plastic
tab is adhered to the ipsilateral aspect of
the user’s back, medial to the scapula. A
tab on the plastic connects to the harness
that activates the prosthesis (Figure 25).
Atlas of Amputations and Limb Deciencies, Fourth Edition © 2016 American Academy of Orthopaedic Surgeons
166
Transhumeral Applications
Mechanism of Control
A harness designed for the patient with
a transhumeral amputation must control
both elbow and terminal device function. Unlike the transradial user who
has the remaining degrees of freedom
of both the anatomic shoulder and elbow, the transhumeral prosthesis user
has only anatomic shoulder function
remaining.
Traditionally, an individual with a
transhumeral prosthesis is required to
operate the device in sequence. The user
must first position the forearm in a desired location using the function of the
prosthetic elbow. Once the forearm is
positioned, the user can then activate
the terminal device. The following three
discrete actions must take place to accomplish the full sequence: (1) the user
must position the elbow in space, (2)
the user must lock the elbow, and (3)
the user can then activate the terminal
device.
Chapter 12: Harnessing and Controls for Upper Limb Body-Powered Prostheses
Figure 25
lateral Scapular Cutaneous Anchor System (the Anchor), a body-powered cabling technique that
eliminates the need for a harness by the temporary adherence of an anchor point near the ipsilateral scapula. (Courtesy of David B. Rotter, CPO, Scheck and Siress, Chicago, IL.)
Posterior (A) and lateral (B) photographic views of an individual wearing the Ipsi-
Sequence of Actions
The primary control motions for the
user of a transhumeral prosthesis are
glenohumeral flexion and biscapular
abduction. These movements are used
to perform both elbow flexion and terminal device activation, which can be
accomplished using a single cable that
is responsible for the two actions. This is
achieved by splitting the cable housing
system to create a fairlead cable system
(Figure 26, A). The cable housing is
split just above and below the prosthetic elbow joint. As glenohumeral flexion
is applied, the distance between the
two split housings becomes smaller,
causing the prosthetic elbow to flex
(Figure 26, B).
When the elbow is prepositioned, the
second action (elbow locking) must take
place. In traditional positive locking elbow joints, an elbow lock cable works
in a reciprocal fashion when pulled. Cycling between locking and unlocking
allows the same body motion to achieve
Figure 26
(arrow) in elongated position (elbow extended). B, Cable (arrow) in shortened position (elbow
exed). (Reproduced with permission from Below and Above Elbow Harness and Control System.
Evanston, IL, Northwestern University Prosthetic-Orthotic Center, 1966.)
both functions. Body-powered motions
commonly used to activate elbow locking include scapular depression, glenohumeral extension, and glenohumeral
abduction.
The anterior suspensor of the transhumeral harness is designed to both
assist in the suspension of the prosthesis and act as the reaction point for the
elbow lock. This is accomplished by attaching the elbow lock cable to the anterior suspensor strap and fashioning the
strap from a combination of rigid and
Illustrations of a split-housing cable used in a transhumeral application. A, Cable
elastic strapping materials (Fig ure 27).
When the user applies the motions of
glenohumeral abduction, glenohumeral
extension, and scapular depression, the
elbow lock cable anchored in the elbow
unit becomes elongated, causing it to
cycle. Relaxing that motion allows the
elastic component of the anterior suspensor to rebound and return the cable
to the original position. Using this sequence of motions, the user can alternate the elbow from unlocked to locked
and repeat as needed (Figure 28).
© 2016 American Academy of Orthopaedic Surgeons Atlas of Amputations and Limb Deciencies, Fourth Edition
167
Section 2: Upper Limb
After the elbow is locked, the same
cable that flexed the elbow into position is used to activate the terminal
device. The user must use additional
glenohumeral flexion and biscapular
Figure 27
pensor strap (arrow) fabricated from rigid and
elastic materials, allowing the elbow lock to
cycle. (Reproduced from Pursley RJ: Harness
patterns for upper-extremity prostheses, in
Orthopaedic Appliances Atlas. Chicago, IL American Academy of Orthopaedic Surgeons, 1960,
pp 105-128.)
Illustration of an anterior sus-
abduction to activate the terminal device (Figure 29). Compared with transradial applications, nearly double the
amount of excursion is required to complete the sequence of actions. Residual
limb length strongly affects the ability to
successfully complete these sequences.
Longer residual limbs generally allow
the user enough force and excursion to
successfully complete the sequence at
the end range of flexion. Patients with
less likely to complete the end range action because of insufficient available excursion. A well-fitting, intimate socket is
especially important for these patients to
ensure that the limited excursion available is captured.
The force-to-excursion quotient in
transhumeral harnessing can be influenced by how the cable system is attached. The elbow flexion attachment
tab on the forearm portion of the transhumeral prosthesis affects this ratio.
There is an inverse relationship of force
to excursion, depending on how close
or how far the elbow axis is to the elbow
flexion attachment tab (Figure 30). As
the tab is mounted more distally and
anteriorly to the elbow joint, less force
is required to flex the elbow, but greater
excursion is needed. Mounting the tab
closer to the joint reduces the required
excursion, but it increases the amount
of force needed to flex the elbow. An average placement and good starting point
of the elbow flexion attachment tab is a
distance of 30 mm (1.25 inches) distal
and 20 mm (0.79 inches) anterior to the
elbow joint center.
Shorter residual limb lengths have
both reduced available excursion and
surface area on the residual limb to absorb the application of actuation forces. In such instances, excursion can be
reduced by placing the elbow flexion
attachment tab closer to the elbow axis
of rotation if an elbow flexion assist or
Automatic Forearm Balance (Ottobock)
is used to offset the increases in the required elbow flexion forces.
Rotational Considerations
The amount of force and excursion captured by the prosthesis is influenced by
the intimacy of socket and harness fit.
The anterior suspensor strap and additional lateral suspensor straps function
to ensure this intimacy of fit in transhumeral applications while helping to
Figure 28
glenohumeral extension and abduction (B), and positioning the elbow in the desired exion angle (C). (Courtesy of David B. Rotter, CPO, Scheck and
Siress, Chicago, IL.)
Atlas of Amputations and Limb Deciencies, Fourth Edition © 2016 American Academy of Orthopaedic Surgeons
168
Photographs of a p atient obtaining the desire d elbow exion angle thro ugh control cable excursio n (A), unlocking the elbow through
Chapter 12: Harnessing and Controls for Upper Limb Body-Powered Prostheses
Figure 29
having obtain ed an advanced amount of elb ow
exion angle through control cable excursion,
must generate additional control cable excursion to open the hook. (Courtesy of David B.
Rotter, CPO, Scheck and Siress, Chicago, IL.)
Figure 31
suspensor strap (left) and an additional lateral
suspensor strap (right). These straps provide an
intimate t and help co ntrol the tendency o f the
prosthetic socket to externally rotate (arrows).
(Reproduced with permission from Below and
Above Elbow Harness and Control System. Evanston, IL, Northwestern University ProstheticOrthotic Center, 1966.)
Photograph of a patient who,
Illustration of the anterior
control the rotation of the socket on the
user’s residual limb (Fig u re 31). When
activating the control attachment strap,
the socket will want to externally rotate.
This can be controlled with a socket that
contours proximally around the stable
structure of the shoulder girdle. As
pressure is applied through the cable
system, the posterior aspect of the scapula resists a tendency for the socket to
externally rotate. A well-fitting harness
Figure 30
elbow joint and the resultant force and excursion requirements. A, As the tab is mounted further
from the elbow joint, less force is required but greater cable excursion is needed. B, As the tab
is mounted closer to the elbow joint, the system requires greater force but less cable excursion.
Figure 32
of the control attachment strap. A, A double harness ring. B, The Biomechanically Aligned Harness
Anchor. (Courtesy of David B. Rotter, CPO, Scheck and Siress, Chicago, IL.)
ensures that the socket is snuggly held
to the user’s anatomy.
Illustrations demonstrating the eect of the elbow tab placement relative to the
Photographs of p atients wearing two dier ent approaches to lower the line of p ull
anchor has the added benefit of encouraging lower placement of the superior
center point, which can be helpful for
Capturing Maximum
Power and Excursion
Two common approaches are used to
lower the line of pull of the control attachment strap. The purpose of these
strategies is to span more surface area
of the back and capture more power and
excursion. Traditionally, a double ring
modification can be used to lower the
line of pull of the control attachment
strap to take advantage of a more optimal position of the strap on the user’s
back (Figure 32, A). More recently, the
Biomechanically Aligned Harness Anchor (TRS) was developed to lower the
line of pull for the control attachment
strap to take advantage of a better line of
force transmission11 (Figure 32, B). This
patients whose anatomic shape encourages the standard steel ring to encroach
proximally on the C7 vertebra and cause
discomfort.
In a more elaborate approach, a
figure-of-8 harness can be modified
with a horizontal strap that crosses the
back. The inferior cross-back strap is
designed to harness more surface area
of the back for the control attachment
strap. This has the effects of stabilizing
the anchor for the control attachment
strap and lowering the line of pull to
take advantage of the broad aspect of
the back to generate power.
Transhumeral prosthesis users who
are unable to obtain adequate excursion to achieve full terminal device
© 2016 American Academy of Orthopaedic Surgeons Atlas of Amputations and Limb Deciencies, Fourth Edition
169
Section 2: Upper Limb
anchor points do not allow the user
to engage as effectively in force transmission as has been described previously. Glenohumeral flexion, ipsilateral
scapular abduction, and the addition
of chest expansion are used. Because
the cross-back strap sits in a more inferior position than in previously described examples, the user can expand
his or her rib cage to help engage the
anchor strap to complement biscapular
abduction and glenohumeral flexion
(Figure 34).
In an alternative application, the
transhumeral shoulder saddle can increase excursion and power by including a Z-strap modification. Similar to
the cross-back strap, the Z-strap modification takes advantage of the broad
aspect of the user’s back, allowing the
user to generate more power and excursion (Figure 35).
Figure 33
tially tted with a gure-of-8 harness (B). The addition of a cross-back strap (C) ensured a better, more consistent line of pull and allowed full opening of the terminal device at full elbow
extension (D). (Courtesy of David B. Rotter, CPO, Scheck and Siress, Chicago, IL.)
activation in full elbow flexion may
benefit from the addition of an inferior cross-back strap modification to
the harness. Taking advantage of a
better line of pull can maximize both
power and excursion output. The inferior cross-back strap limits unwanted
migration of the control attachment
strap and keeps it firmly anchored in
the broad powerful area of the user’s
back. The modification may allow individuals with shorter residual limbs
to fully open the terminal device at full
elbow flexion (Figure 33).
Photographs of a patient with a short transhumeral amputation (A) who was ini-
Shoulder Saddle
Similar to its use in a transradial application, the shoulder saddle in transhumeral harnessing is used to achieve
the goal of dispersing the pressure
of suspension from the contralateral
deltopectoral groove to the ipsilateral
shoulder and contralateral chest wall.
This application is appropriate for
patients who use their prostheses for
heavy lifting. Although this configuration has good load-bearing properties,
it is less efficient for transmitting force
and excursion. The placement of the
Michigan Roller Harness
The Michigan roller harness is also
used in transhumeral applications.
Cable housing runs across the shoulder saddle and houses the cable that
suspends the prosthesis. Similar to a
transradial application, the purpose
of this harness is to create unimpeded smooth movement as the user engages in forward flexion and return
extension.
Alternative Harnessing Strategies
Alternative harnessing variations and
strategies have been used to achieve the
goals of capturing effective force and excursion while maintaining comfort for
the user who cannot tolerate pressure in
the contralateral axilla. Similar to transradial applications, these techniques
lower the anchor point of the harness
below the contralateral axilla using a
distal circumferential strap.
Y Split
By using a Y split in the harness, the
anterior branch travels superiorly to act
as the suspensor, whereas the inferior
Atlas of Amputations and Limb Deciencies, Fourth Edition © 2016 American Academy of Orthopaedic Surgeons
170
Chapter 12: Harnessing and Controls for Upper Limb Body-Powered Prostheses
Figure 34
of a shoulder saddle harness. (Reproduced from Pursley RJ: Harness patterns for upper-extremity
prostheses, in Orthopaedic Appliances Atlas. Chicago, IL American Academy of Orthopaedic Surgeons 1960, pp 105-128.)
Illustrations of anterior (A) and posterior (B) views of a transhumeral application
branch travels laterally and connects
anteriorly to form the anterior crosschest strap. The cross-chest strap travels inferior to the user’s xiphoid. This
approach is appreciated by female users
who desire a cosmetic harnessing option that does not have a strap crossing
proximal to the breast that can be seen
when wearing low-cut clothing. The
control attachment strap is anchored
at the fork of the Y split (Figure 36).
In a variation, the Y split on the user’s
back captures suspension and control
because the inferior Y split acts as the
control attachment strap.
Figure 36
used to position the contralateral chest strap well distal to the contralateral axilla. This approach is
appreciated by females because the strap runs distal to, rather than across, breast tissue. (Cour tesy
of David B. Rotter, CPO, Scheck and Siress, Chicago, IL.)
Posterior (A) and ante rior (B) photographic vi ews of an alternative harness s trat egy
Triple Control Harness
The Triple Control Harness (Ottobock)
isolates three movements to perform
three different functions. The anterior
suspensor is responsible for elbow locking and unlocking, the center strap is
responsible for terminal device open-
Bilateral Application
Similar to harnessing at the transradial
level, an axilla loop component is not
needed for a bilateral harness. Rather,
the two prostheses anchor each other
(Figure 37).
ing and closing, and the inferior strap
is responsible for elbow activation. By
isolating the discreet movements of
glenohumeral flexion for elbow activation and biscapular abduction for terminal device activation, both functions
can be used simultaneously.
Shoulder Disarticulation
Applications
Harnessing for a body-powered pros-
thesis at the shoulder disarticulation
level is challenging because the sourc-
es available for generation of force and
Figure 35
the use of the Z-strap modication to mimic
the benecial eects of a cross-back strap in a
transhumeral, shoulder saddle harness design.
(Courtesy of Jack E. Uellendahl, CPO, Hanger
Clinic, Phoenix, AZ.)
Photograph demonstrating
excursion are limited. With the absence
of the humerus, the powerful and effective movement of glenohumeral flexion
is no longer present. The movements
available for elbow and terminal device
activation are limited to biscapular abduction and chest expansion.
Elbow lock function must also be
approached with a different strategy
because glenohumeral abduction and
glenohumeral extension are not possible. Scapular elevation is used to activate elbow locking. This movement is
© 2016 American Academy of Orthopaedic Surgeons Atlas of Amputations and Limb Deciencies, Fourth Edition
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