|On Stump Socket Lamination (GTZ - GATE, 1986, 43 pages)|
Wieland Kaphingst / Sepp Heim
A Publication of the Deutsches Zentrum für Entwicklungstechnologien - GATE , a Division of the Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ) GmbH - 1986
All rights reserved
© Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ) GmbH, Eschborn 1986.
The Tanzania Training Centre for Orthopaedic Technologists (TATCOT) at the Kilimanjaro Christian Medical Centre (K.C.M.C.) in Moshi, Tanzania offered an advanced professional seminar in August 1980. One of the participants, an American Mennonite missionary nurse, Miss Mary Harnish, working at the Shirati Hospital, Lake Victoria, presented some of the prostheses and orthoses manufactured by herself and her assistants in the most simply equipped rural workshop at their hospital. No professional would have thought that these devices would give proper service to their users.
Fortunately Mr. S. Heim, orthopaedic-engineer and project manager of TATCOT, which is assisted by the German Agency for Technical Cooperation (GTZ), and I, an orthopaedic surgeon specialized in orthopaedic technology, had been invited to visit Shirati Hospital after the seminar. We were greatly surprised at the simplicity of manufacture, especially of a PTB below-knee prosthesis with cuff suspension which was exclusively hand-made due to a lack of machinery commonly available.
We followed the prosthetic manufacture step by step, with the amputee sitting and his thigh resting on a small stool. Prominent bony and pressure sensitive areas of the below-knee stump were padded with some cotton material, then two handknitted woolen stockings were pulled on to the stump and the knee. Afterwards the entire assembly was covered with a thin sheet of plastic foil, followed by four layers of stockinette. Resin was prepared and brushed on the stockinette. After setting the socket was taken off and cut along trimlines to PTB shape. A hand-carved, roughly preshaped lower shank-foot-"component" made from a locally grown, extremely light wood was cut to proper length and glued to the provisional socket by a mixture of resin and sawdust. After another check of length and fit the entire prosthesis was painted with resin again, reinforced all over (including the rockerlike foot) by fibre glass patches this process being repeated two or three times. Finally, a cotton stockinette was pulled over the prosthesis and painted with a brown coloured resin. A sole of lyre-rubber was attached to the rocker foot, a piece of inner tube was prepared for supracondylar suspension and a sheet of plastazote was glued on the interior of the socket, and the prosthesis was then ready for use.
On the occasion of our first visit we met two or three patients who had just been or were just being fitted; one of them, a completely blind bilateral below-knee leprosy amputee convinced us that this kind of simple manufacture could be more helpful than we ever would have thought possible. However, evaluation after long term use under the severe conditions due to climate and in a farming environment had not been made yet. Additional difficulties in the patients returning to the workshop for review restricted repairs even if necessary.
For these reasons we had the distinct interest to follow-up those patients who had been fitted in Shirati throughout the last 10 years and more recently at Sikonge Hospital. The GTZ became interested in our proposals; with additional financial assistance from the
German Leprosy Relief Association (DAHW) Mr. J. Fischer, certified prosthetist and orthotist from Denmark, and I returned to Tanzania in November/December 1982 for evaluation of a total of 47 amputees.
Some 38 of them had a below-knee amputation due to leprosy and were most likely to develop serious stump problems. They were living in rural areas, mainly as subsistence farmers; only a few of them were occupied in small trade, some others were unemployed due to their severe disability. Prosthetic treatment of these patients showed on average unexpectedly good results with an overall positive effect on daily life and general rehabilitation.
Despite this satisfying outcome there were some prostheses that were no longer usable due to improper fit of the socket, causing pressure sores and ulcerations of the stump. The plastazote soft liner, which was compressed and non functional after a short period of use, turned out to be by far the weakest link in this kind of prosthesis, and no other part had been repaired or replaced so often. However these leprosy patients used their appliances regardless of pressure sores because the decrease or total loss of sensitivity and the protheses were absolutely necessary for ambulation as most of them could not walk with crutches alone.
Besides other minor criticisms from a professional technical point of view, the principles as well as the long term results indicated that this simply manufactured prosthesis had proved valuable under the local conditions. Its method of manufacture, however, had to be improved prior to its introduction to other developing countries with similar local conditions.
The necessity for less problematic sockets, especially for a long-lasting soft liner that would help prevent pressure sores and ulcerations, were the reasons for initiating a research programme. The results are laid down in this manual as the first part of a complete guide for the manufacture of this type of prosthesis. It describes how to fabricate an improved socket and soft liner according to proper professional prosthetics and biomechanical principles. The handling of plastics for this purpose, avoiding the use of heavy and sophisticated machinery, is well explained and incorporates modern materials such as fibre glass, resin and PE foam. The first trials are promising and future follow-up of a reasonable number of patients fitted with the new-socket should be an important step forward to further progress.
I should like to thank Mr. J. Fischer for his fine cooperation during our basic evaluation as well as Mr. S. Heim and Mr. W. Kaphingst, who developed the techniques drafted in this manual, for their excellent work. I hope and wish it will become an additional "brick" for building up professional orthopaedic technology in developing countries.
Priv. Doz. Dr. med. Georg Neff
One of the basic materials used for manufacture of nearly all orthopaedic appliances is plaster-of-Paris (p.o.p.).
When an exact cast of parts of the body is needed, plaster-of-Paris powder or bandage is used to make a negative model. P.o.p. is then used for positive models which can be modified according to basic anatomical and biomechanical criteria which frequently determines the function and success of the orthopaedic device.
P.o.p. powder, though, is not available in many developing countries. Its import and transport costs greatly exceed the value of raw material. Additionally no one would be able to guarantee its condition for use after a sea journey of perhaps thousands of kilometres and into developing countries with climates of all types with heavy rainfalls and high humidity.
Somehow, therefore, the prosthetist must cope with this problem and accomplish his objectives even without p.o.p. if need be.
There is a possible solution, demonstrated by Mary Harnish, Shirati Leprosy Control Centre (S.L.C.C.), Shirati, Lake Victoria, Tanzania which achieves the manufacture of prostheses, by means of resin sockets laminated "directly" on to stumps without using p.o.p.
The original technique may appear strange to the expert and, indeed, has caused considerable problems during development of the technique as well as with obtaining the required functional result.
The "Tanzania Training Centre for Orthopaedic Technologists" (TATCOT) and an expert group were confronted for the first time in 1980 and 1982 respectively with this technology and they have managed to improve the fabrication technique as well as the functional result.
This manual describes the improved "Direct Socket Lamination Technique" (D.S.L.T.) which has been applied successfully in many cases. It should be pointed out that this procedure of using appropriate technology is not easier but rather more difficult to apply than the usual manufacturing method. It was not developed as a "primitive solution" for non-experts, not in order to push aside the traditional method whenever this could be applied but rather as solution when no p.o.p. is available.
This manual will hopefully supply solutions to specific professional problems in developing countries and the authors would be grateful, at any time, for further inquiries, criticism and hints.
We would like to thank Mr. Norman Jacobs for revising the draft manual and also the numerous colleagues whose suggestions proved very useful for the work.
Figures 1-3 explain the manufacture of special tools. They are an essential help in order to simplify the manufacturing technique for D.S.L.T. prostheses and should be available before work starts.
The chamfering blade is a special tool for chamfering the glue edges of the PE foam (PE-lite, Tepefoam etc.). It will simplify the working procedure of chamfering, providing neat processing of glue edge of the soft liner.
If a sanding drum (or, perhaps a grinding stone) is available or if chamfering manually with a sharp knife is familiar to you you will not need this tool. For persons with less practice, it will be an essential help.
The best cutting results are obtained by using a slightly tilted blade (e.g. put a match underneath in order to alter the cutting angle).
At first, practice with some waste pieces is suggested.
Application of the tool is explained in more detail in Fig. 7.
The blade should be covered by a blade cover when not in use in order to avoid injuries.
Later on in the process, the moulding tool is needed in order to functionally shape the tendon bar and the contours of the patella.
The socket tends to form cavities at this point which are unfavourable for a good fit. With this moulding tool, these disadvantages will be avoided.
It is prepared from sheet metal of 2 mm thickness corresponding to the example shown, bent to a U, and strengthened along the edges (e.g. by means of a plastic tube or a glued-on PE-lite reinforcement). This reinforcement also eliminates sharpness of the edge.
For every patient, the shape of the tool must be adjusted afresh. If necessary, some remaking or rebending is carried out in order to achieve an individually perfect fitting form. Application of the tool is shown on Fig. 43.
Later on in the process the glueing aid is needed in order to glue the edge of the PE-lite cone to the soft liner in a relatively simple and neat way. It is a trapezoidal wooden bar with rounded upper edge. The measurements are standard and for most soft liners they should be suitable.
During the manufacturing procedure, the glueing aid, at its broader end, is fastened onto a bench-vice. If you have sufficient experience in free-handed manual glueing of soft liners you will not need to prepare such a tool but for those with less practice it is an essential help. Application of this tool is shown in more detail in Figures 10 and 11.
In Figures 4-25, the manual manufacturing technique of the soft liner socket for D.S.L.T. PTB prosthesis is shown. Before you start with any particular manufacturing step, you should read through all of this part of the manufacture, and all materials and tools required (see part 4) must be prepared.
For preparation in cutting the material for the soft liner you
need the following
a circumference of widest knee joint part,
b circumference right above distal stump end,
c length from above (supracondylar) the knee joint up to end of stump.
PE foam material (PE-lite, Tepefoam etc., not Plastazote!) of 7 mm thickness is cut into a trapezoidal and symmetrical shape. The upper edge corresponds to circumference measurement "a" taken before.
The cut must be 100 mm (4 inches) longer than the length measurement "c" taken before. The width "b", however, is situated at a distance of "c" from the upper edge. This procedure makes the lower edge of the cut smaller than circumference "b" which is important for a proper fit of the liner.
Both oblique edges of the cut material must be chamfered. One edge is chamfered from the upper side and the other from the lower side.
If a sanding drum (or a grinding stone) is available, a thin wooden slat, used as a support, is put under the edge which should be ground to an equal width, without wrinkles or lacerations. The grinding width is about 15 mm (0.6 inches).
Please note: One edge to be ground from above. The other edge to be ground from below. Neat work is essential.
Please read text of Figures 1 and 6.
The wooden support for the cut must have the same thickness (20 mm, 0.8 inches) as the small wooden block on which the blade is fastened, otherwise the cut will not be correct.
Put the PE-lite along the edge of the support and now, simply push the blade along the edge. Tilting the blade (put underneath) can be advantageous for the cut. Practice with a piece of waste first.
Please note: Cut one edge from above. Cut the other edge from below. Neat work is essential. Cover the blade after use.
This working procedure using a shoemaker's knife is an alternative
for the procedures shown in Figures 6 or 7. The criteria are the same, and the
result must be the same.
This procedure is possible but needs expertise.
In case of difficulties, please proceed according to Figures 6 or 7.
Both chamfered edges are painted with a thin and equal layer of a flexible glue (Pattex or a similar type of glue). Before glueing together, be aware of the time needed for drying, which is given in the manufacturer's instructions.
Both glued edges to be painted with a thin and equal layer of glue.Avoid dirt and forming of bubbles.
Only a suitable glue to be used.Be aware of the time necessary for drying.
Fasten the glueing aid in a bench vice.Hammer in two thin nails in a way that:
a) the distance between them will be nearly the length of the glued edge,
b) their heads remain about 10 mm (0.4 inches) from the aid.
Remove the nail heads:
One glued edge should be laid along the aid with some slight stretching, and pressed through nails. Now, the piece is secured against slipping off. The second glued edge should be picked up, placed around, arranged, and pressed on, the mid part first. Rub towards the bottom accurately and without wrinkles. Rub towards top, accurately and without wrinkles.
Please note: The glued edges must be neatly arranged when one is put on top of the other. Working without wrinkles is necessary.
Glued edges of this kind maintain their stability due to the force of application during glueing. Forceful but careful hammering will stabilize the glued edges.
Please note: Avoid any damage of material.
This illustrates the finished cone to be used to make the soft liner.
The strength of the liner (material strength) is consistently the same, even within the glued edges. The edges should be perfectly glued ail over with no wrinkles, lacerations or other imperfections.
In the event the cone for the soft liner socket should show any manufacturing mistakes, the procedure must be repeated right from the beginning.
It is less costly and better to correct possible mistakes now, rather than to continue work with faulty results and be forced, later on, to start again.
The below knee (BK) stump has bony (little weight bearing capacity) and muscular (sufficient weight bearing capacity) parts. The bony parts are relieved in the socket whereas the muscular parts are mostly loaded. In order to relieve bony prominces therefore, reliefs within the socket are provided.
The soft tissue of different amputees vary from stump to stump. This diagram shows the areas which are generally relieved:
1. Medial (inner) edge of the femoral condyle: It can be palpated in thin patients and with flexed knees. Normally, it does not cause any difficulties since, when loading the prosthesis, in a standing position, it does not protrude. In some patients, though, it would be better to relieve this edge, the decision to do so will be dependent on the individual amputee.
2. Tuberosity at the medial (inner) head of the tibia. Mostly, the medial tuberosity is less pronounced than the lateral (outer). Therefore, it is not significant to relieve it for every patient but must be decided for each individual amputee.
3. Lateral (outer) tuberosity at the head of the tibia. This can be felt distinctly in almost all patients and therefore, it has (almost) always to be relieved.
4. The anterior (forward) protuberance of the tibial head which is also the beginning of the patellar tendon. Unlike the patellar tendon which can and should be loaded, this is a bony prominence which has to be relieved.
5. The cross-section of the tibia is triangular shaped. One of the edges protrudes anteriorly (forward). This edge, but only this edge and not the surface of the tibia, should be relieved. This edge is known as the tibial crest.
6. Bony (and muscular) end of the stump. Depending on the surgical techniques, the covering of soft tissues, the scars and possible nerve endings, the stump end is not well suited for weight bearing purposes, at best it can only be partly loaded. This can be determined by palpation and questioning of the patient. The decision of the amount of relief required will be dependent on the individual stump.
7. The head of the fibula protrudes distinctly in every patient. It must always be relieved.
8. For the end fibula, the same criteria are valid as mentioned under point 6.
The parts to be relieved are to be determined individually in every patient.
Important hints will be supplied by questioning and palpating the patient.
The relief pads shown correspond in their form and contour to the bony protuberances shown in Fig. 13. For preparation of the socket, they are applied on to the stump and later on, after completion of the socket, taken off. Thus, well defined free spaces for relief of the bony protuberances, are prepared.
Relief pads can be:
- Cuts from fast setting p.o.p. bandage (p.o.p. bandage is frequently available in developing countries) which is self-adhesive.
- A: Chamfered PE-lite pads, to be fixed with adhesive tape.
- A: Chamfered felt pads, to be fixed with glueing tape.
- A: Wax-like substances such as plasticine (or tissues soaked in bees wax) - self-adhesive.
- A: Clay or Loam - self-adhesive.
The pads must have their main thickness (about 3 mm) centrally, their thickness tapering off towards the edges. Their surfaces are slightly larger than the bony protuberances. In p.o.p. bandages, this can be accomplished by 4 somewhat larger basic layers and 4 identically shaped but smaller covering layers. The wet p.o.p. pad is fingermoulded and well stroked out towards the edges. With the other suggestions, this will be achieved by chamfering and grinding.
The procedures indicated by an "A" are alternatives in case p.o.p. bandages are not available. The procedure using p.o.p. cuts is the best solution. Thickness of relief pads is 3 mm centrally, tapering towards their edges. They should follow the contours of bony protuberances and their surface should be only slightly larger.
Due to possible pumping movements of the stump, they must be somewhat larger towards distal end. They must be well fixed. During subsequent procedures, their position must not change.
The best embedding and working position is a knee flexion angle of 30 to 40 degrees.
Two layers of cotton stockinette are put on to: a) act as protection from heat, b) secure the position of the relief pads.
The stockinette is pulled up to nearly half the length of the thigh, without wrinkles, well compressed, and fixed with glued tape.
The smooth textured side must be to the outside.
The stockinette must be free of wrinkles and well compressed.
There is an alternative for the stockinette. The stump can be wrapped with an elastic bandage or gauze bandage. Here, the edges must be secured with adhesive tape to avoid the bandage slipping during the subsequent working procedure.
All alternative procedures mentioned here are the second best solution only. Whenever stockinette is available, it should be used.
The stump covered by the stockinette must be well covered with talcum powder which serves as a sliding agent for ease of pulling on the soft liner.
In case an air circulating oven, a good baking oven or any other electrical source of heat is available, it can and should be used due to the possibility of regulating working temperature. For PE foam materials, a working temperature of 130 °C (270 °F) should be used. If these devices or an electrical supply are not available, a charcoal fire may be used for heating the thermoplastic material.
The cone used for the soft liner is placed on a broomstick or other similar stick, held above the glowing fire at a distance of about 300-400 mm (12 to 16 inches) and must be turned continually in order to heat it equally. Once it is soft, flexible and mouldable, the proper working temperature will have been reached. If its surface has become somewhat sticky, wait for the proper working temperature before continuing work.
Control of temperature is important for success of your work. The working temperature is achieved, once the cone
- becomes soft (easily to be compressed with your fingers),
- becomes flexible (could be=bent from side to side),
- becomes mouldable (possibility to widen the edge).
The material must be equally heated alI over. Sticky surface indicates over-heating.
Brown or wrinkled, hardened spots are burnt ones.
Do not continue working with burnt or partly burnt material as the padding effect and resilience will then be lost.
You are advised to learn this working technique with a test piece first.
Fig. 19: Additional talcum powder for sliding
Fig. 20: First applications of liner cone
The inside of the heated cone must be well powdered with talcum in order to assist it with sliding over the stump.
Pull the heated cone over the stump. -The position of glued edge should be posterior. This process should be carried out quickly but with great care. After the first heating, the cone can only maximally be pulled up to below the patella and therefore, it will have to be heated a second (and third) time in order to achieve its final position. On repeating it will lose some of its moulded form which, however, will be regained with the subsequent applications.
Do not continue work with possibly burnt material.
Do not work with overheated (sticky) material.
Do not continue working with cooled material as it cannot be moulded.
Do not pull the material if it is not sliding over the stump easily as its edges could be torn off.
Talcum powder must be applied before each application (of the cone).
Fig. 21: Final position after 2 to 3 healings
Fig. 22: Cutting of lower cone end
The final position of the cone must have a sufficient height such that, later on in the procedure, the brim forming will be achieved easily (Fig. 46 and 47). Please bear in mind that the inner liner will be 5 - 8 mm longer than the hard outer socket.
The applied height is sufficient once the inner and outer brim reach about the height of the upper patella edge. However, it would be much better if it can be pulled up to the supracondylar area. There it will form folds and bulge but this is of no significance since these parts will be cut off later on.
The distal end of the cone must enclose the stump well and must contact it all over, without any free space.
For postmoulding of the distal socket end:
- re-heat distal third of cone,
- pull the cone up and let the patient hold it,
- free spaces and wrinkles must be pushed off downwards,
- forming wrinkles below the stump is of no significance, as they will be cut off later on.
Do not twist the heated cone as this will form folds and wrinkles.
Do not overstretch the heated cone as this will result in differing liner thickness which would be weak spots in material.
Pull the proximal end of the cone as far up as possible. The distal closure must not have any free spaces.
The area of what is to be the final soft liner must be kept free of wrinkles. Position of the glued edge is always posterior. For other precautional measures see the description of Figure 20.
Draw a circular trim line at the distal end of cone, as far distal on the stump as possible, above the level of the folds. The distal cap, including all folds, is cut off. This cut edge must be even and smooth.
Pull cone off, distal end to be cut neatly (no peaks) in a circular way. Very sharp knife to be used.
The newly existing distal end should be chamfered. Use a sanding drum (perhaps grinding stone), or handrasp and sandpaper.
Please note: Distal brim to be chamfered evenly and smoothly. At any case, avoid laceration. Cone to be pulled on again.
Cut a square piece of PE foam, sufficiently large for closure of the distal opening, about 150 x 150 mm (6 x 6 inches). Heat it, hold it at the corners and, with slight stretching, pull it over the distal stump end. During this procedure it would be helpful to make use of an assistant. Attention must be taken that the distal end of the cone is not damaged. After pulling over, the piece should be well moulded with both hands and kept in position until cooled down. Then, it should be cut in such way that the chamfering on the cone is well overlapped. Mark the subsequent glue edge and the position.
The edges are painted with glue and the end fixed in its correct position.
Even and wrinklefree glueing of the end of the cone is necessary.
The soft liner is taken off again and now, the glued edge is chamfered from the outside. No wrinkles, lacerations or holes are to be seen at the neat closure of the distal end.
Frequently, a second layer of PE foam will be required in order to sufficiently pad the stump end. Check the material thickness of the distal closure.
Checking the Results
The completed soft liner is an essential part for a good
functional interface of the stump with the prosthesis to be manufactured. All
possible manufacturing faults affect either directly the interface with the
stump, or else the life expectancy of the soft liner.
Thus, the liner must be examined carefully both on and off the stump.
Examination on stump:
- Is the glued edge situated posteriorly?
- Is the fit faultless?
- Is the liner sufficiently adjacent to the stump all over?
- Does it present no free spaces?
- Are the relief pads in the prescribed position?
- Is the proximal end sufficiently high?
- Is the distal end sufficiently padded?
Examination when taken off the stump
- No overhead or burnt parts?
- Do the glue edges adhere without wrinkles?
- No lacerations, wrinkles or holes?
- No weak spots along thickness of liner?
The soft liner should only be used if all points mentioned above are acceptable.
It is easier and less costly to manufacture a new soft liner right now than to ignore the faults which will lead to a faulty result.
In many cases, the patient needs two soft liners in order that they may be exchanged. In this case, the second should be manufactured now and, after completion and the measurements, compared with the first. Later manufacture will always bring different presuppositions (e.g. different relief pads for bony structures, etc.) and thus, a second liner which is manufactured later on will not fit with the prosthesis as well as one manufactured now.
Figures 26-57 show the manual manufacture of the hard outer socket for the D.S.L.T. PTB prosthesis. Before continuing with the particular manufacturing steps, you should acquire a comprehensive view, and all tools and materials required (see part 4) should be well prepared.
In spite of careful mixing of resin, hardener and accelerator it develops warmth during its setting process. With faulty mixing it can become hot. The stump of the patient is protected from this warmth by two layers of stockinette and by the soft liner. Care should be taken that the thigh must also be protected against this warmth although this should not be necessary since the resin should not reach this height. However, it is better to take a lot of care in order to absolutely ensure that the patient is not burned. The following steps must be taken:
- wrap the proximal liner with a gauze bandage or elastic
- with the rest of the bandage, the distal third of the thigh is bandaged with overlapping,
- the bandage must be secured with adhesive tape.
The PVA sleeve, moistened in a wet towel, and the soft liner are powdered with talcum which serves to aid the PVA to slide on to the stump.
The PVA sleeve is put on. It will be pulled proximally as far as possible, displacement of the heat protection bandage is to be avoided at any rate. The sleeve must well compress the soft liner all over and be free of wrinkles. If the sleeve is too dry, it is not elastic and difficult to be pulled on, whereas a sleeve which is too moist will be torn.
Wear no jewellery (rings), and the edges of fingernails must be well trimmed and smooth. Be careful that the sleeve is moistened correctly.
The sleeve should be pulled up as high as possible.
Avoid displacement of heat protection bandage.
Avoid damage to the sleeve.
A damaged sleeve must be replaced by a new one.
Once the PVA sleeve is completely pulled up and fixed at the proximal end, the wrinkles at distal end can be mostly eliminated by pulling out downwards, ensuring that the soft liner is well compressed all over. The sleeve must be tied tightly with a double thread at the distal end making sure that the PVA film is not damaged. Cut off the excess PVA film at the end of the sleeve.
Now, the sleeve entirely encloses the soft liner, compressing it and with no wrinkles other than several small ones at the distal end. Wrinkles in the area of the thigh are of no significance.
Sleeve to be pulled up without wrinkles compressing all the soft liner.
At stump end, sleeve is to be tied and cut off.
Damage of sleeve must be avoided. A possibly damaged sleeve is to be replaced by new one. Avoid displacement of heat protection bandage.
An alternative for the PVA sleeve is given by any PE film (e.g. film of plastic shopping bags). However, PVC film must not be used as polyester resin does not harden when in contact with PVC.
PE film is not as elastic as PVA film and is difficult to make into a conical bag form. Thus, it is applied by wrapping it into the stump, or by laying it on the stump and turning over in one piece, care being taken to ensure that it is as wrinkle-free as possible. However, this procedure is not possible without wrinkles. The edges must overlap and are to be fixed with adhesive tape in order to reliably avoid penetration of the resin into the soft liner. Do not apply PVC glue tape (see above).
All alternative procedures mentioned above are second best solutions. Whenever PVA sleeve is available, this should be used, and not PE film.
Do not apply PVC film and PVC adhesive tape.
Wrinkles within the soft liner caused by film wrinkles must be smoothed off later on and could possibly lead to inaccuracies of the fit.
For lamination, a total of 6 layers (3 double layers) of stockinette will be pulled on. Nylon stockinette is more stable but where not obtainable, it could be replaced by cotton stockinette. Stockinette pieces of double length are pulled above the knee, the distal end is either tied or turned around once, then turned over and pulled up above the knee. Both upper ends of the final double layer are cut at their anterior and proximal part (on the thigh) for about 20 - 30 mm (0.8 to 1.1 inches) and knotted firmly with each other. Thus, the stockinette is pulled up in a wrinkle-free and compressing manner.
If glass mat or fibre glass is available, this can be used for reinforcing the lamination. For each of the two last layers, take one piece of glass mat, the size of palm of a hand and push them medially and laterally underneath the layers. This is especially indicated in heavy or active patients although it is not absolutely necessary. Use of an entire glass mat is contraindicated as:
- processing of the brim will be much more difficult,
- thermoplastic re-moulding will be more difficult,
- during the pouring procedure you cannot judge whether the resin has completely soaked the stockinette layers under the glass mat reinforcement.
Six layers of stockinette to be put on.
Stockinette must compress without wrinkles.
Stockinette must be fixed so that no displacement occurs.
Final appearance of completed laminated stump.
There is an alternative to the application of stockinette: The use of medical cotton gauze bandages. These bandages are wrapped,with good tension and must overlap each other. There should be at least six layers in order to achieve the required liner thickness.
The bandage ends must be well secured.
The alternative procedure mentioned above is always a second best solution. Whenever stockinette is available, this should be used, and not the gauze bandage.
The outer PVA sleeve, well moistened in a wet towel, is pulled up.
Be careful that the sleeve is moistened correctly. Avoid damage to PVA sleeve.
A possibly damaged sleeve is to be replaced by a new one.
Sleeve must be pulled up well compressing the stockinette. Do not cut the distal sleeve end.
Fig. 36: Outer PVA sleeve in final position
Fig. 37: Preparation of compression pads
As described already (Fig. 13) some weight bearing surfaces of the stump must be in good contact with the liner, in particular the muscular parts must be compressed in order to take up weight. Due to the relief pad applied on the crest of the tibia, the soft liner as well as the stockinette tend to gap medially and laterally to the crest and thus are not in contact as required.
This can only become corrected from the outside by the following means: medial and lateral compression pads made from PE foam are prepared and, after moulding and compressing, applied there.
Size and form of compression pads to be determined individually. Parts to be chamfered towards the edges in order to avoid impression of edges.
The lateral compression pad extends around behind the stump for about 30 mm.
Application of pads is described under Figure 43.
During its setting reaction, resin develops warmth or even heat. The heat is dangerous to the patient. Therefore, by application of less amounts of hardener and accelerator than usual the heat development is reduced so that it only becomes warm. A desired side effect of using less amounts of hardener and accelerators is prolongation of setting time and, thus, simplification of the entire pouring procedure.
Due to the fact that resins from different manufacturers will require different percentages of hardener and accelerator, absolute details cannot be given here; But the following is always valid:
A maximum of 2/3 of the normal hardener amount is to be applied.
A maximum of 2/3 of the normal accelerator amount is to be applied.
Never use a resin on a patient if the relation of mixture and type of reaction are not exactly known. Never use unknown resins.
Danger of burning exists.
Acrylic resins need no accelerator. Some polyester resins have been pre-accelarated already and need no accelerator. Acrylic resins are more suitable, but polyester resins are quite applicable.
Before applying the resin, the stump outlines are palpated once again. For a good result the following areas should be noted: - bony contour of patella, - bony distal edge of patella,
- the tendon of patella (see drawing),
- bony contour of tibial head,
- bony contour of tibial crest,
- medial bony surface of tibia,
- bony small head of fibula,
- muscular surface, lateral to tibial crest,
- compressibility of calf muscle,
- popliteal flexor tendons,
- concave curvature of popliteal area.
Test application of moulding tool. It has two moulding sides, one of which should fit. But this must be, checked and, if necessary the tool re-adjusted.
All items mentioned above will be considered later on during socket manufacture in order to achieve a good functional result.
Turn over PVA sleeve brim so that it cannot be torn, fill with resin mixture. The sleeve is kept in the illustrated position until the air enclosures (larger air bubbles) have escaped.
Is the relation resin: hardener correct?
Do not throw away the mixture cup for resin, it will still be needed.
After the air bubbles have escaped, the resin will be pressed slowly into the stockinette material, evenly soaked from distal toward proximal part. Unsoaked 'isles', must be avoided. For the present, the resin is not to be distributed higher than a level under the base.
Resin is only to be pressed up to under the knee.
Adhesive tapes are available in order to close quickly any possible holes in the PVA sleeve. This procedure can be carried out slowly as hardening will still take about one hour.
The sleeve is tied below the resin reserve (without any trapped air) in such a way that the knot can be reopened without damaging the PVA film (do not use a thin thread but a thicker string or shoe lace). The sleeve end is to be turned over and tightly tied (thin tread) in order to avoid unnecessary dripping. Now, with a shoe lace, the resin is slowly and carefully distributed up to the resin boundaries presented on the sketch. Powdering of . the sleeve with talcum will ease this work. Do not exceed the resin boundaries given, otherwise you cannot pull off the socket later on.
- Under the film, due to trapped air, parts with uneven resin distribution are seen. It helps to make several small holes by means of a needle into the part concerned. Massage the trapped air out of these holes, until only resin appears. Wipe this part neatly and close it with adhesive tape.
- Under the film surplus resin can be seen. The surplus resin should be massaged into the resin reserve at the stump end by means of the shoelace.
Open the shoelace at stump end again and let the resin surplus run back into the PVA film hose. After ensuring that the resin is evenly distributed with no puts bearing too little or too much resin the sleeve will be finally tied as close as possible to the stump end.
When pricking the film, splashing danger exists as the resin is under pressure.
Eye protection to be worn.
Be careful of the proximal resin boundaries. Eliminate trapped air.
Clean work is necessary - resin may cause skin damage.
Spilled resin must be cleaned immediately.
Check again the PVA film with regard to tightness. Any leakages have to be closed by adhesive tape. The distal sleeve end should be cut off below the knot. Film end must be wiped clean. The remains of the resin in the cut-off sleeve are poured back into the mixing cup.
Wait until the resin begins to set.
Due to the higher resin concentration, this will occur first with the remains in the mixing cup. Watch the cup and as soon as it gets warm, the next procedure will start.
Start fixing the compression pads in their intended position by wrapping them with an elastic bandage. Avoid any stringy (bandage) wrinkles. The bandage must not be wrapped higher than required. Fix the bandage securely by means of adhesive tape.
With one hand:
Apply the moulding tool. Its concave edge applies pressure on the patellar tendon and outlines the contour appearance of the patella area. However, it must not press onto the bony structures. Faults in application of the moulding tool will result in high pressure points in the prosthesis.
With the other hand:
The other hand is located on the posterior side of the stump. Intermittently, it presses carefully on the calf, flattening it, and the finger tips mould the proximal, posterior socket brim at the popliteal region and the flexor tendons area. Do not apply pressure onto the flexor tendons.
The functional moulding, with intermittent pressive hand positions, is kept up until the resin is so hard that its shape will not change anymore.
Alternatively, instead of application of a PVA outer sleeve, the resin could also be applied by brush onto the stockinette layers.
The alternative procedure mentioned above is always the second best solution only. Whenever PVA sleeve is available, it should be applied.
After application of the alternative procedure in Figure 44, the resin is massaged by means of a metal spatula into the material in order to ensure its thorough distribution through it. Simultaneously, the resin surplus is pressed out again. The surplus resin should be collected in the mixing cup which must be held underneath.
If a PVA outer sleeve is not available, the functional moulding procedures presented in Figure 43 will be difficult or made impossible. The functional moulding corrections must then be performed later, which is much more difficult, and imprecise in its result.
This diagram shows the position of the cut edge of the socket brim from both an anterior and a lateral view. The patella is covered between 1/3 to 1/2 of its height. Laterally, the socket brim rises about 20-30 mm (according to size of patient) above the mid patella at a position of about 2/3 of the lateral leg width. Then, slightly slanting, it runs relatively steeply down, posteriorly. The measurements given are approximate only. The brim slope is specific to each patient, and differs individually.
1. shows the undulating form of the posterior socket brim. Its
mid-height corresponds to about the height of the midpatellar tendon support bar
on the anterior side.
2. shows relief of the lateral flexor tendon.
3. shows relief of the medial flexor tendon.
Here, the soft liner is wrapped around the posterior brim in order to act as protection from pressure and also when the leg=is flexed (sitting position). The medial flexor tendon must have more relief than the lateral one. Forming the posterior brim requires skill and careful check of the result with the cooperation of the patient.
4. shows a concave impression in the distal popliteal area. This acts as a counter support (popliteal pad) in order to firmly secure the position of the patellar tendon opposite patella support bar. Above this impression, though, the socket brim is bulged outwards.
The soft liner must be 5-8 mm higher than the brim of the hard socket.
The socket brim shape, as indicated in Figures 46 and 47, are cut with strong scissors.
Exact contours are formed by a handrasp. Here, rasping for medial flexor tendon is shown. Subsequent smoothing is done with sandpaper.
Be careful when forming the brim.
It is easy to remove material, but once removed it can not be patched on again.
The soft liner is 5-8 mm higher than the hard socket brim.
For fitting and for subsequent processing, the socket is inserted into a block of light wood, inserting it to a depth of about 40 mm (1.5 inches). It is glued with a mixture of resin and sawdust.
The wood fibres run in vertical direction. This time, the resin should be prepared with normal hardener amount. Position and arrangement of socket can be seen in Figures 51-53.
Alignment of the socket depends on the individual stump position. For adducted stumps, alignment is adducted, for abducted stumps, it is abducted, and for stumps in neutral position, sockets will be aligned in neutral position. Deviation from anatomical and biomechanical considerations will cause pressure sores by the socket.
Frequently, with the normal anatomical shape, medium length stumps appear to be in an adduction of about 5°, whereas extremely short stumps appear to be, or are really in a position of abduction. Compare with the form of your own lower leg, at different heights below your knee joint.
Fig. 53: The result - lateral view
The lateral view shows a flexed position (forward tilt) of the socket, of about 5°; this slightly flexed position is essential in order to achieve a good force distribution and force acceptance by the patellar tendon. A more flexed position is possible, but an extended or hyperextended position is contraindicated.
Looking from above into the socket, a cross-section of a triangle with almost equally long sides is to be seen. One side forms the anterior, medial tibial edge, the next stands for the anterior lateral muscle surface, and the third side for the flattened calf.
This functional shaping prevents rotations of the prosthesis around the stump and simultaneously corresponds to the anatomical biomechanical requirement of the BK stump.
It is not possible to functionally modify the D.S.L.T. socket to such a degree as would have been the case with a positive p.o.p. model. Alteration in shape or volume, though, may be carried out to a possibly required extent, without real difficulties.
With a cone-shaped metal nozzle turned upside down and put on a charcoal fire (e.g. a petrol funnel), certain parts of the socket may be point heated in order to re-mould these parts thermoplastically.
Fig. 56: Point heating by means of lighter
Minor shape alterations, e.g. Iimited pressure points, can be heated with a normal gas lighter.
Fig. 57: Manual moulding alteration
Thermoplastic corrections are performed manually. A moist cloth protects against burning the fingers and, simultaneously, cools down the desired result more quickly.
Example on picture:
Increasing the position of the posterior, distal popliteal pad (with more pressure into the socket) and, simultaneously, greater bulging outwards of the posterior proximal socket brim.
Part 1 - Tools
General instruments for measuring and drawing. General woodwork tools. General tools for metal work.
Part 1 - Materials
Wood, metal sheet (2 mm thick), plastic tube or PE foam.
Part 2 - Tools
Measurement and writing instruments: pencil, measuring tape, folding meter, ruler. Cutting tools: sharp knife, scissors, chamfering blade (Fig 1). Machines and alternatives: router machine with sanding drum, or handrasp and sandpaper rough and fine. air circulating or electric oven or charcoal fire. Other items: workbench with bench-vice, support for cutting (wooden board, about 1 m x 1 m x 20 mm (39 x 39 x 1.2 inches), glueing aid (Fig. 3), hammer, tongs, glue-brush/spatula, glue container, talcum in container.
Part 2 - Materials
PE foam, about 7 mm thick (PE-lite, Tepefoam, Polyfoam, Campolite, Multifoarn, but not Plastozote), Pattex or other glue, cotton stockinette, width 80 - 120 mm (3-4.6 inches), fast setting p.o.p. bandage, water, adhesive tape on linen base, small nails.
Part 3 - Tools
Same as for Part 2, in addition: towel, strong leather scissors, I needle, mixing containers for resin, spatula for stirring, protective eyeglasses, round rasp, halfround rasp, either router machine with rasp cutter or curved chisel and hammer.
Part 3 - Materials
Either acrylic resin and hardener orpolyester resin and hardener (and accelerator if necessary).
2-3 premanufactured PVA film sleeves for BK prostheses,
2 elastic bandages or strong gauze bandages, adhesive tape on PE base (take care with PVC tapes!),
Nylon/cotton stockinette 80 x 120 mm (3-4.6 inches) width,
PE foam, thickness about 5 mm, shoemaker thread, 2 shoelaces about 30 mm (about 12 inches) long.
Block made of light wood, 120 x 120 x 120 mm (4.8 x 4.8 x 4.8 inches).
Sources of Supply
for countries with purchasing possibility in Germany:
- Fa. Otto Bock
Orthop. Industrie KG
(this firm has international establishments)
- Fa. Schein
Orthopadie Service KG
- Fa. W.J. Teufel
7000 Stuttgart 1 - FRG
for countries with purchasing possibility in USA:
P.O. Box 1678
2710 Amnicola Highway
- Hosmer Dorrance Corporation
P.O. Box 37
Campbell California - USA
- United States Manufacturing Co.
180 North San Gabriel Blvd.
P.O. Box 5030 .
Passadena California 91108USA
for countries with purchasing possibility in the UK:
- Otto Bock (UK) Ltd., 32 Parsonage Road, Inglefield Green, Egham, Surrey.UK
- J.E. Hanger & Co. Ltd., Roehampton Lane, Roehampton, London SW15 5PL UK