ucla upper extremity amputations manual - sholder prosthesis

7/25/2019 UCLA Upper Extremity Amputations Manual - Sholder Prosthesis

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Shoulder Prosthesis

I Introduction

Levels of Amputation

1 In the axilla level amputation,the head of the humerus is re-maining but there is insufficientlength of the stump to control aprosthetic humeral section.

2 In the shoulder disarticulation,the head of the humerus isabsent and the scapula andclavicle are present. The patient

normally has shoulder girdlemotion remaining on the amputatedside to control the prosthesis.

3

In the interscapulothoracicamputation> part or all of thescapula and clavicle are absentand the patient lacks shouldergirdle motion on the amputatedside to control the prosthesis.


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Discussion

Short Humerus (axillary level)

When the humeral head and neck are present, the use of a mechanical shoulder joint

is considered only for those patients with very limited motion of the shoulder.The information gained by making the excursion tests (side C) on the prostheticinformation sheet are helpful1 in making the Rx plan.

The addition of an externally powered elbow can greatly enhance the performanceat this level. In some cases this method may even be the prescription of choicefor the shoulder disartiuclation.

Disarticulation

Limited range of motion in the shoulder girdle indicates the need for a mechanicalshoulder joint which enables the wearer to passively preposition the humeralsection for various activities. The condition also indicates that there is in-sufficient excursion of the cable to operate the prosthesis. Considerationshould be given to assistive accessories such as excursion amplifiers or anelectrically powered elbow unit.

Interscapulothoracic

Loss of the shoulder girdle indicates that the wearer cannot act?vely operate theprosthesis from the involved side. Excursion motion comes totally from thesound side. This means a total invo?vZment of the sound shoulder and arm to

--operat-e the prosthesis Amputees do not accept this concept of function andtherefore, the prosthesis becomes little more than a passive holding vise or isworn for cosmetic reasons only.

Use of external powered units should be utilized for theinterscapularthoracic

patient.


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Fabrication techniques for the shoulder type prosthesis differ mainly with thetype of shoulder joint that is to be used.

Abduction Joint

The abduction joint consists of two separate single pivot hinges. The joints aremounted on the socket so that a part of the shoulder or head of the humerus isbetween the joints. This joint makes a more cosmetic appearing socket*Separate friction adjustme?nts are made with an Allen type wrench. The joints aremounted on the socket at a 30 degree angle to the sagittal plane.The humeral section is then moved into flexion and abduction in a manner similarto the normal arm when performing a hand to mouth operation.


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Flexion (Bulkhead) Joint

A medium size joint is used for the disarticulated humerus. (A superior frictionarrangement to the previous joint). I t is , however, less cosmetic in thefini shed prosthes is. It also should be mounted at an angle to permit flexion andabduction of the humeral section.

Flexion/Abduction(Wniversal) J o i n t

This joint allows motion in all planes. Somewhat uncosmetic, it .requiresadouble lamination to form a cap or covering.


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Flexion/Abduction Joint

Attached to the socket by three metal strap in effect permits motion in all planesexcept extension. It can be used over the humeral head with little effect oncosmesis. A good joint for light duty as the friction adjustments do not worksmoothly when turned up tightly.

Flexion (Bulkhead) Joint

An ear l y model shoulder joint used mainly with interscapulothoracic type socket.


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Since the step-by-step procedure for making the three different types of pros-theses are similar, all three will be discussed together below. The main areas

in which the three types differ will be emphasized.

1r.

Shoulder Prosthesis

A complete prosthesis (The ones shownare for bilateral shoulder disarticu-lations) generally weighs about 3pounds. The average weight of thewhole arm of the human body, includingthe hand is about 4.9 percent of bodyweight.

Information and Measurements (taken at the initial visit of the patient)

List of materials: 1 goniometer1 straight edge ruler1 3X3 piece of tracing paper

1 A sample information form is shown on page Complete the applicable

portions of the form with particular attention to the following:

The names of the clinic and the physician should always be noted. The physician

should be consulted when medical problems arise and the clinic may have to beconsulted when problems occur with financing, therapy, training, etc.


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Under Yondition of Stump examine the stump to determine if any scars, neuromasor any other areas exist that are sensitive and need relief in the socket. Notethe condition of the remaining bones and the existence of any bony prominenceswhich will have to be relieved in the socket. Check the muscles to determine ifthey are adequate to control a prosthesis, and measure the stump ranges of motion

(any remaining shoulder girdle motion) so that the socket can be made to allow foras much residual function as possible.

Under Rx (Prescription) for Prosthesis note the type of socket, components andmaterials that will be used for the prosthesis. Also note which components ormaterials have to be ordered from the manufacturer or supplier.

1. To determine the amount of buildup(if any) and shaping necessary tomatch the sound side, make a tracingof the amputated and sound sides.Using a plumb line, e tablish avertical line bisecting the body.

2 To match the length of the prostheticarm, measure the length of the soundarm from the acromion to the lateralepicondyle and from the lateralepicondyle to the thumb tip.


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The Wrap Cast

List of Materials: cot tos c i

sheelaYatbut

ind

Pla

ss

etstes

keel

st

elt i

n stockinette 6 inches to 8 inches wide)ors

(to drape the patient)ic webbingclamps

t of waterible penciler bandage (about 6 inches wide)

ng agent for cast

1 Determine the design of the socket for the patient to see how far the cast

will extend.

Make the wrap cast according to the type of socket to be fabricated. Avoid asocket design which will tend to immobilize shoulder girdle movements necessaryfor pr os thet ic contro l. Suf fi ci ent skirt ng posterior over the scapula andinferior to the axilla, on the rib cage a distance of 2 or 3 inches willstabilize the prosthesis for the axilla level amputation.

Disarticulation rules out the possibility of effectively capturing therotatory motion of the shoulder. The need for stability has also increased,therefore, the area to be covered by the socket can be increased for stabilityatid comfort for the wearer. In addition to the area described above, extendthe wrap one half the distance to the nipple on the anterior and cover three

or four ribs below the axilla.Loss of the shoulder girdle as in the interscapulorthoracic rules out thepossibility of any active socket motion.

Therefore, the body socket for males should cover an area equal to the involvedside rib cage. For a female, the anterior part of the socket is cut out forthe breast. A shoulder flap for the opposite side is made to stabilize thesocket on the body. When making the wrap, a separate slab of plaster can beformed over the opposite shoulder connectedto the socket across the back.

2 Cut a length of 6 inch to 8 inchwide cotton stockinette longenough to cover the cast area. S l i tthe stockinette to open it, wetit so the plaster will adhere andplace it on the patient as shownwith elastic or webbing and clamps.


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3 An alternate method of taking acast is to pull the whole piece ofstockinttte over the body withouts l i t t i n g i t .

Outline the boney areas closest to the skin surface. Relief in the socket isusually needed for the acromion and spine of the scapula. The clavicle is alsoa sensitive area.

4 Using 6 inch wide plaster bandage,wrap the stump by lapping the

bandage back and forth to makethree or four layers for strength.Be sure to cover all the areas of theexpected trim lines, which may besketched on the stockinette ifdesired.


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5

6

Smooth the plaster and mold itwell to the body, especially wherethere are indentations and bonyprominences.

Af ter the plaster hardens,carefully

remove the cast to avoid distortingi t .

7 Inspect the inside of the cast to see that there are no wrinkles or unwanted

bulges or indentations and that the cast covers the necessary area.

If the cast appears satisfactory, put a parting agent on the inside for makingthe model.


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3 . Smooth the whole model, beingcareful not to lose theidentification marks. Make theplaster buildups as follows

about 1/4 inch over the clavicleand about 1/4 inch over acromion(if present) including theacromioclavicular joint.Blend the buildups into themodel and smooth.

4

Put a parting agent on the model for ease in removing the wax check socket later.


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3

Immerse the model in cool water to harden the wax. Before the wax completelyhardens, form it over the model with your hands to remove bridging of contours.

4

Cut the wax check socket to theapproximate desired trim and pullit off the model. Smooth theedges and powder the inside beforeapplying to the patient. Savethe model in case another wax checksocket has to be made.

5

Place the wax check socket on thepatient. Small windows can becut in the socket for checkingthe f i t .

6 Check to see that the reliefs

for bony prominences andsensitive areas are adequate.

Apply forces to the socket indifferent directions. Heat andform where necessary for relief.Make sure the distal edge ofskirting does not dig into therib cage. Flare the edge asneeded.


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7 . Check the trim lines on the

socket as follows:The proximal brim should allowfor purchase of the socket on thestump but should also provideclearance for the neck duringshoulder elevation or scapularabduction.

8 . The posterior trim should allowenough skirting of the socket toprovide rotational stability.For the three levels of amputationthe trim usually is

for the axilla level, midscapula;for the shoulder disarticulation,trim at the vertebral border ofthe scapula;

the interscapulothoracic, justlateral to the spinal column.

The anterior trim line should

allow enough material to providerotational stability and shouldhave a flared edge for comfort.For an interscapulothoracicamputee, it should extend almostto the centerline of the body.

Avoid the nipple area whereverpossibe.


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The top of the shoulder supportsthe socket and vertical loads andthe side of the body provides a

reaction point for forces on theforearm and terminal device. Thelateral trim therefore, mustextend distal enough for comfortabledistribution of forces.

9

Check the trim lines for function and comfort by having the amputee adduct/abductand depress/elevate his shoulder girdle. Trim the edges to allow as much range

of motion and comfort as possible without sacrificing stability of the socketon the stump.

10. To align the mechanical shoulder joint on the socket later, three reference

lines must be established on the wax check socket.

11. The superior proximal reference lintrepresents the coronal plane of thebody (projected for

interscapulothol

acic

amputee). This establishes the

frontal plane. A temporary harnessto support the socket is desirable.


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12 .

13 .

14 .

The anterior reference line isestablished by a plumb line onthe anterior portion of the socketwith the shoulders level.

The lateral reference line is atthe center line of the side ofthe body when the amputee isstanding erect.

After the fi tt ing of the wax check sockto make sure that they are smooth and rsocket with plaster bandage so that it

mold.

et is completed, examine the edgesounded.

Carefully reinforce thewill not be distorted when making the


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Making the Mold

List of Materials: plastermandrelawl

knifesandpaper or screenBBs

parting agent for mold

1 Make a hollow mold as described inthe Materials section. Insert themandrel for handling the mold.

2 When the plaster sets, remove

the plaster bandage reinforcementand carefully mark two pointson the mold through the waxcheck socket on each referencel ine. Remove the wax check socketby slitting it and pulling itoff the mold.


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3 . Smooth the mold. The trim lineshould form a rounded, smooth

edge on the plastic socket. PutBB? or round head screws in themold, so the reference lines canbe transferred to the plasticsocket.

4 Apply a parting agent on the mold for the plastic lamination.

The Plastic Socket

List of Materials: dacron felt

1

nylon stockinette (6 inches or 8 inches wide)scissorsstringPVA

polye ster resin, catalyst, promoter, and color pigmentsander

Apply one layer of dacron felt

and two layers of nylon stock-inette on the mold. This canbe accomplished by either makinga dacron felt bag and pulling itand the stockinette over the mold,or by using sheets of the dacronand stockinette and tacking themto the mandrel side of the mold.


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2 . Make a PVA bag, wet it, and pullit tightly over the mold in sucha way that vacuum can be used.Eliminate all wrinkles in thePVA bag and. then tie it at the

bottom. I f po ss ib le , lo ca teboth the top and bottom of thebag on the mandrel side of themold to eliminate wrinkles andexcess resin on the socket. Theuse of vacuum is recommended tomake a light but strong socket.Before laminating, test thevacuum sys tern and the PVA forleaks and proper function. See

page

3

Mix polyester resin with itspromoter, catalyst and colorpigment. Pour this mixture intothe top of the PVA bag and workit into the stockinette. Tie thethe top of the bag to remove excess

resin.

4 After the resin has set, loca tethe reference lines and scribe themon the socket. Now roughen thewhole socket for adhesion of foambuildup and final plastic lamina-tion.


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Installing the Shoulder Joint and Making the Humeral Sect i on

List of Materials: cardboard or polyethylene sheetmasking tapepolyurethane resin

shoulder jointelbow unit turntableplumb bobstraight edge rulertracing taken during measurementsdrill (to make holes in straps)polyester resin, catalyst, promoter and color pigmentnylon stockinettePVA

sander

The procedures for installing any of the five kinds of shoulder joints on thethree types of prostheses are similar. The main differences occur in the align-ment of the shoulder joints. The alignment of each type of shoulder joint isshown below.

Transfer the alignment lines to the outside of the socket. Use the indentationsmade from the BBS or round head screws on the inside of the socket for this.

The Abduction Joint

1. The abduction joint is internallyrotated. The angle is usuallyabout

30

degrees. In this position

when the joint is abducted, italso flexes the

humeral

sect ion.Mount the joints on a spacer forthe interscapulothoracic. TheY V type alignment jig is usedwhen the shoulder girdle is pres-ent . Set the j ig so that the

joints will be close to the socket.


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2 . Al ign the socket so the anterior

reference line is vertical. Theaxis must pass through the projectedlocationof the head of the humerus.In the illustration, the socket isfor a right shoulder.

3

Af ter the socket is lined up sothe lateral reference line isvert i ca l , position the joint soit is horizontal. Place the

joints to follow the contour ofthe shoulder.

Flexion/Abduction (Universal) Joint

4 Since this joint has both flexion

and abduction motion, it isaligned so the flexion axis isperpendicular with the proximalreference line and the abductionaxis is parallel to the line asshown in the illustration.


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5 Line up the socket so the anteriorreference line is vertical and

position the joint. The top edgeshould be even with the shoulderline and, with the tracing as aguide, the lateral edge shouldmake the amputated side the samewidth as the sound side.

6 Line up the socket so the lateralreference line is vertical andposition the joint so it iscentered on the line.

Flexion (Bulkhead and Ring) Joints

7. The flexion joint axis is externally

rotated 30 degrees from thesagittal plane or as much as iscosmetically acceptable. When thejoint is flexed, it also abductsthe humeral section in relationto the body and puts the arm in agood functional position.


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8. Position the socket so the anteriorreference line is vertical and the

joint face parallel to the line.The top edge should be even withthe top of the shoulder andlaterally at the projected locationof head of the humerus.

9. Center the joint axis on thelateral reference line.

Flexion/Abduction Joint

10. This joint is installed in a similarmanner as the universal jointexcept that it is positioned atthe height of .the head of thehumerus. The lateral edge also

makes the amputated side thesame width as the sound side.


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The step-by-step procedures for installing the flexion/abduction joint andmaking a humeral section for a shoulder disarticulation prosthesis are as follows:

1

The flexion/abduction joint isideally suited to the shoulderdisarticulation or humeral headremaining; when used for the inter-

scapulothoracic, a build-up tocosmetic contour of normal side ismade before aligning and placingo f jo int .

2 First, make a cardboard or polyethylene form for a foam build-up on the

socket so the amputated side will match the sound side. Refer to the tracingand make the build-up larger than the sound side so it can be shaped down to

match. Now pour the polyurethane resin into the form.

3 After the resin has set , remove the cardboard or polyethylene form. Shapethe foam so the amputated side matches the sound side in width and there isan undercut as shown for the humeral section.

4 After the foam is shaped, align theshoulder joint as previouslydescribed. Drill holes in thestraps so the resin will graband hold the joint more securely.Bend the straps to the shaped foam.


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5

6

Remove the joint and coat the foamwith polyester resin to seal the air

spaces to prevent air bubblesin the final lamination. When theresin sets, roughen the surface sothe final lamination will adhere.

Remove the joint from the strapsand place them into position andhold them in place with screws.

7 Remove the straps and put two layers of nylon stockinette over the socketand build-up, tying or tacking it on the mandrel side of the mold.


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8. Reposition the straps holding themin place with screws through theattachment holes into the holes in

the foam. F il l dacron felt in anyspaces between the straps and thestockinette. A wood block canbe used as a fairing for cosmeticallyinsetting the joint.

9. Apply two more layers of nylonstockinette over the socket S Othe straps will be imbedded inplast i c .

CL Make a PVA bag, mix the resin and laminate as indicated previously.

When the resin has hardened but isstill hot, trim the plastic away

from the attachment holes so thejoint can be insta lled on thestraps.


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12 . When the resin has set, attach thejoint to the straps and prepareto make the humeral section.

13 Make a humeral section form byshaping cardboard or polyethylenein a cylinder with the elbowunit turntable taped to one endof the form.

14

Make the form long enough so the length from the acromion to the elbow unitturntable matches the distance on the sound side from the acromion to thelateral epicondyle minus the distance from the elbow unit joint center to theturntable.

15

Pour polyurethane resin into the form. The humeral strap will be positionedon the foam after it sets.


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19. .

20 .

21 .

Coat the whole humeral section with polyester resin to seal the air spaces.Roughen the surface after the resin sets so the plastic lamination willadhere.

Make a mandrel for holding thehumeral section when laminatingputting a dowel or rod throughthe hole in the turntable intothe foam.

Pull two layers of 2 inch or 3 inchwide nylon stockinette by tying thestockinette at the groove in theturntable, doubling it back andtying it at the top.

22 Make a PVA bag, mix the resin andlaminate the humeral section. Toeliminate the need for vacuum,pull the PVA bag tightly over thecylindrical shape. Tie the PVAbag at the top to remove excessresin.


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23 . After the resin sets and is stillhot, trim the plastic from the

part of the humeral strap thatfits into the joint .

24 With a cast cutter, cut thesocket to the approximate trimlines and remove it from themold. Trim the socket to thelines previously established.The edges should be rounded andthe inside should be very smooth.

25

Make any necessary additionaltrims to the humeral section

and assemble the humeral sectionto the socket.


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Harnessing:

Harnessing the shoulder prosthesis is the most difficult of all the amputationlevels . t requires all the prosthetic skills the prosthetist can apply in orderto obtain acceptable results for the patient. Compared to the below elbowharnessing where a simple figure of eight provides ample unilateral excursion and

mobility, the wearer of the shoulder type prosthesis has difficulty managing eventhe fundamental control functions. Elbow flexion and terminal device opening

are provided by the harness and control system, but prepositioning the arm fromthe mechanical shoulder joint is purely passive and accomplished by the sound arm.

Scapular Abduction: (shoulder protraction)

Amputations which require the shoulder type prosthesis do not have suff icientunilateral shoulder motion to provide the necessary excursion of the cable toonerate the nrosthetic elbow and terminal device. The amount of excursionnecessary to operate the prosthesis is approximately 5

1/2

inches. Unilateralscapular abduction can only produce an excursion of approximately 3 inches which

is inadequate to operate the elbow unit and terminal device. Therefore, aharness which is designed to utilize only unilateral scapular motions such asthe chest strap harness should not be applied to the shoulder prosthesis as thesole control source for dual control of the elbow unit and terminal device.

Biscapular shoulder motion is essential to produce the needed excursion tooperate the prosthetic units. It must be pointed out, however, that harnessingwhich involves the sound arm and shoulder in an active way is not generally wellreceived by the wearer.

Shoulder Elevation:*

Shoulder elevation as a source for prosthetic control operation has t wo maj ordisadvantages. First, the reaction point, which is attached to either a waistor peroneal strap, thereby links the shoulder to the trunk or pelvis. This thenrequires trunk motion for prosthetic control operations and is most efficientonly when standing. Secondly, the very act of shoulder elevation moves theterminal device away from the object of grasp instead of toward it.

Shoulder elevation is used for elbow lock operations in females and those caseswithout adequate chest expansion because of the small amount of excursion requiredand the sequence in which it occurs. In the presence of adequate chest expansion(males) for elbow lock operations, chest expansion can be used.

Biscapular Abduction:

The harness of choice for axillary level and shoulder disarticulation amputationsis designed to utilize biscapular abduction. The application of an axillary loopto the harness provides the biscapular control. It also increases the excursionneeded to the necessary amount to operate the dual control system. A separate,simple chest strap with elastic maintains the prostheticsocket on the body andcan provide elbow lock control at the same time.


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diagonal shears

adjustable hanger

two 1/2 inch wide buckles

two anchors for elbow lock cable housing

1/2 inch hanger Yates clamps

polyethylene tubing for axilla

drill and tap for elbowflexion

attachment screw

teflon l iner

List of Materials for Harnessing Shoulder Prosthesis

elbow unit, forearm and terminal device

drill (to make about a 1 inch diameter hole in plastic)

9 6

inch wrench (for elbow turntable nut)

adjustable elbowflexion

attachment

elbow spring assist

cable

large cable housing

swivel terminal

swaging tool or soldering kit

two retainers

wood burning tool

1 inch hanger

swaging tool or soldering iron


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Preparing th.e Arm for the Patient

1

2

Drill a 1 inch hole in themedial side of the humeral sectionand clear the foam at the turn-table nut for installation andfriction adjustment later.

Assemble the elbow unit, forearm :terminal device to the humeralsection. Attach the adjustableelbow flexion attachment at thelateral elbow joint and, ifdesired, the elbow spring assistdevice to the medial side of

the elbow joint.

snd


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3. Cut the following:a length of cable to reach from the terminal device through the elbowflexion attachment to the shoulder joint and medially approximately 3

inches past the edge of the socket.

a length of large cable housing to reach from the wrist to the elbow jointcenter.

a length of large cable housing to reach from the lateral elbow jointcenter to the shoulder joint and medially about 1 inch past the edge ofthe socket.

4 Swage or solder a triple swivelterminal to the cable and connectto the terminal device. Attachand cut the lower cable housing asshown.

t

should not interferewith the terminal device openingand should extend about 1/2inch proximal to the elbowflexion attachment loop. The

loop should now be rivetedto securely hold the housing.


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5

6.

Pronate the terminal device andextend the elbow for maximumcable excursion. Run the cablepast the shoulder joint center so

the cable will not inhibit shoulderjoint motion. The cable shouldfollow a smooth curve at theshoulder joint.

Place a base plate on the humeralsection so that the control cablewill pass anterior to the elbowjoint axis approximately 1 inchwhen the elbow is extended.Moving the base plate attachmentpoint on the humeral section to a

lateral position increases thedistance away from the elbowaxis. Moving it toward theposterior decreases the distance.

Temporarily position the baseplaste on the socket at mid scapulaor so that there will be a smoothtransition from the shoulder jointto the contr ol st rap. Plan toreposition if necessary duringthe harnessing.

Put two retainers on the upper

cable housing and position theretainers and housing. Thehousing should follow a smooth line.The upper and lower cable housingshould not meet when the elbow isful ly f lexed. The housing shouldextend to the edge of the socket.


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7 Put the ad jus tab le hanger on the

cab l e so t ha t i t w i l l no t p inchthe sk in aga ins t t he socke t .Have the hook pronated and elbow

ex tended a t t h i s t ime .

8 . T he w ai st ba nd t yp e el bo w lo ck

control wil l be shown here. Runthe elbow lock cable and housing

up by the shoulder jo in t center(so cable excurs ion wi l l no tchange with shoulder joint motion)and down on the socket, as shown.The cable is ready to be connected

to a wais t band la ter . Put smal lanchors on the elbow lock cablehous ing to hold i t in p lace and

swage or solder a2

inch hangerto t h e c a b l e .


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2. Excur si on Ampl i f i er s

If the amput ee has f orce but not enough excur si on f or cont r ol mot i on an excurs i on

ampl i f i er can be used. Thi s decr eases t he r equi r ed ody excur si on ( but at t he

same t i me i ncr eases t he r equi r ed body f or ce) .

Two t ypes of excur si on ampl i f i er s arehcwnbelow.

The pul l ey ampl i f i er reduces the required body excursion in h lf nd doubles the

required body force. ) The mechanical advantage of the lever amplif ier i s t h a t

i t can be var ied by p lacement of the cont ro l s t rap cable on the lever .

ucla upper extremity amputations manual - sholder prosthesis

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