WO1996009077A1

WO1996009077A1 - Method for fitting prostheses directly on users and a prosthesis according to the method

Info

Publication number: WO1996009077A1
Application number: PCT/NO1995/000159
Authority: WO
Inventors: Dag JØRSTAD; Egil Jensen; Jon Andersen
Original assignee: Joerstad Dag; Egil Jensen; Jon Andersen
Priority date: 1994-09-19
Filing date: 1995-09-11
Publication date: 1996-03-28
Also published as: FI971128A; AU3579895A; NO943480D0; NO180103B; NO943480L; EP0783329A1; FI971128A0; NO180103C

Abstract

The direct fitting of prostheses, prostheses consisting of an outer weight-bearing shell and an inner core in a light foam material, and a casting substance for use in the method and the prosthesis are described.

Description

Method for fitting prostheses directly on users and a prosthesis according to the method.

The present application relates to a method for fitting prostheses directly on users, a prosthesis consisting of an outer weight-bearing shell and an inner core in a light foam material, and a casting substance to be used therein.

Fitting a prosthesis is presently a complicated and demanding process involving measuring, plaster casting modulation of a positive plaster model and, finally, casting of a prosthesis casing or sleeve in thermoset plastic or thermoplastic. Not until this has been done can the prosthesis be tried out on the user. During the fitting, the prosthesis is adjusted while the user walks, enabling attainment of optimal pressure load and striding pattern. When the prosthesis has attained an acceptable function, it must be finished completely and given its cosmetic design. The user must come to the workshop a minimum of three times, the first time to take measurements, then to try out the apparatus, and finally to fit and adapt the finished prosthesis. The current method for fitting a leg prosthesis has several disadvantages. It requires considerable work and is separated into production phases involving a visit by the user at three stages in the course of the production time. This generally means that there will be a period of a minimum of three weeks from the time when measurements are taken until the finished prosthesis is delivered. During these weeks, much time is spent on the production of the prosthesis — time that could have been used to work directly with other patients. The problem becomes greater the more persons there are who need prosthesis fitting (e.g. , in war- torn areas). The major work effort invested in each prosthesis also results in increased production costs. The longer the period needed for the fitting process, the longer the user must wait before the rehabilitation phase with the prosthesis can begin. This is valuable time for a person who is mentally and physically debilitated after a serious trauma. In addition, each day that the rehabilitation phase is delayed means increased financial costs.

FR 2,095,097 describes standard thigh prosthesis casings in various sizes that are characterized in that they provide sufficient space between the actual casing and the stump to allow the injection of plastic material to create a good fit on casting of the stump. The prosthesis casing has an opening with a closing mechanism into which the foam is poured. This patent thus describes and explains a principle for filling up an excess volume in a prefabricated casing for thigh amputees. It does not take into consideration how the transferral of force is to take place in practice.

In order for a thigh stump to be able to assume a natural, unforced position in the casing, without adjusting the angle of the casing, the casing must basically have a very large volume (particularly in the front section). This makes the casing very heavy after it has been filled up with foam and, moreover, less acceptable cosmetically.

On the other hand, the present invention describes the fitting of a prosthesis comprising the filling out of an excessive volume and the transferral of forces from the prosthesis to the body by the use of relief pads and pressure pads. This makes It possible to take individual differences into consideration with the direct fitting of prostheses to leg amputees. Various amputation levels require the use of quite different principles and methods for the transferral of forces from the prosthesis to the body part. It is important to elucidate the differences between a thigh amputation and a leg amputation.

A thigh amputation is, due to considerable soft tissue mass, very poorly suited for receiving the vertical load represented by the body weight and the velocity of the stride. For this reason, all known classic principles for transfer of vertical forces from body to thigh prosthesis are based on the premise that this transferral of forces shall occur not via the upper part of the thigh as described in FR 2,095,097, but via the lower part of the pelvis (the seating center). The thigh amputation thus receives little or no vertical force. For stabilization of the prosthesis, on the other hand, it is at times subjected to considerable horizontal forces. It is very important how these forces are distributed. In FR 2,095,097 these forces will distribute themselves uniformly over the whole amputation stump during the hardening process. This Is in conflict with the fact that the amputation stump consists of the area which definitely tolerates less load/pressure than others.

A leg amputation involves a composition of soft tissue, solid tissue (bone) and shape that make it possible to transfer all forces from a prosthesis to the body through the amputation stump. It is of some significance, however, where on the stump these forces are transferred. The requirements for proper fit and the correct distribution of load/pressure and relief areas are quite high and necessitate individual consideration from case to case.

The present invention thus relates to a method for fitting prostheses directly on users, characterized by the use of prefabricated prosthesis casings filled with a casting substance and formed directly on the user while employing relief pads and pressure pads to attain the optimal fitting of the prosthesis. The optimal fitting takes place with the transferral of forces from prosthesis to body through use of the aforementioned relief and pressure pads. The leg shell and the foot are selected after measurements have been taken of the user's stump and healthy bone, foam is removed from the inner core of the shell so that the user's stump may be placed sufficiently far down Into the leg shell. Self-adhesive relief pads are fastened to areas exposed to pressure, and a relief pad is placed at the bottom of an insulating sheath which is pulled onto the stump. The method is further characterized in that a two-component casting substance is filled into the cavity of the leg shell , the stump with an outer insulating sheath is placed in the prosthesis and pressed down to a desired position, the user then assumes an optimal position which is maintained until the entire hardening process is finished, the stump is withdrawn from the prosthesis, the insulating sheath and relief pads are removed and, finally, the casing edges are trimmed and polished. The user then draws onto the stump 1-10 stump stockings, preferably from 1-3 stump stockings, pressure pads are placed under the outermost stump stocking in the desired position, and the stump is placed into the prosthesis; then a knee strap is fastened to the leg shell and the user tries walking with the prosthesis. The method is further characterized in that the alignment of the prosthesis is finely adjusted by moving the foot portion, which is spot-glued, relative to the leg shell, and when optimal alignment has been attained the foot part is glued permanently; then on attainment of optimal pressure distribution in the prosthesis casing, the pressure pads are securely glued permanently into the inner walls of the prosthesis casing to provide pressure where it is tolerated best.

The present invention further relates to a prosthesis consisting of an outer weight-bearing shell and an inner core in a light foam material, characterized in that it is fitted by filling up the leg shell with a casting substance, whereupon the user places the stump down into the leg shell, and that optimal fitting is then attained by the use of relief pads and pressure pads.

Also described is a casting substance for use in the above method and prosthesis characterized in that it consists of a plastic material, preferably a cold-hardening polyurethane based elastomer with a setting time of 60-80 min. , preferably 10-20 min. There may also be used other thermoset plastic systems or silicon-like substances capable of hardening at body temperature. The requirements for fixation time, moderate exothermic reaction, attachment to the leg shell, mechanical strength and costs are critical.

The invention will be described in more detail in the following, with reference to the accompanying figures, where:

Figure 1 shows the right leg with a knee strap, leg shell and o foot part.

Figure 2 shows the amputation stump with relief pads.

Figure 3 shows the amputation stump with relief pads and 5 sheath.

Figure 4 shows the prosthesis casing with pressure pads and foam.

o The present invention thus describes a fitting process based on a direct technique, i.e., it renders superfluous the use of negative and positive plaster models. The fitting technique may be used for all types of prostheses. With the aid of prefabricated components, a special jig in which the 5 user stands to attain the correct position during the process, and a unique casting substance, the prosthesis may be fitted directly onto the user in the course of about 1 hour. Based on average measurements taken of about 70 users, leg shells in a plurality of sizes are prefabricated from a suitable o plastic material (Fig. 1). These consist of an outer weight- bearing shell 1 and an internal core 2 in a light, rigid foam material. Core 2 is removable from the ankle level and upwards. Upper part 3 of core 2 is fitted to each individual user by removing sufficient amounts of foam to provide space 5 for the amputation stump 4 in the upper part 5 of the leg shell. To the lower part of the leg shell is glued a foot 6 of wear-resistant rubber/polyurethane. This Is selected from an assortment of a number of different foot sizes for the right and left foot.

Leg shell 1 and foot 6 are selected according to measurements taken of the user's stump 4 and healthy bone. Foam is removed from the inner core 2 so that the user's stump 4 may be placed sufficiently far down into leg shell 1. Leg shell 1 now has an interior cavity 7 corresponding to the volume of leg stump 4 plus adequate clearance on all sides. The height of leg shell 1 is adapted to the user's healthy bone.

During the fitting, the amputation stump 4 is examined. Self- adhesive relief pads 8 are fastened to those areas that are exposed to pressure (Fig. 2). A relief pad is placed at the bottom of an insulating sheath 9 which is then drawn onto the amputation stump 4 (Fig. 3). Insulating sheath 9 is impregnated with a gliding agent on the stump side. A casting substance 11 is thoroughly mixed either in a suitable container or directly in the cavity of the leg shell. When the casting substance 11 is within leg shell 1, the user places amputation stump 4 into the prosthesis and presses slowly downward to the desired position. An outer insulating sheath 9 is drawn up over the user's knee to prevent spillage of casting substance 11. The user is then instructed to assume an optimal position and this is held until the hardening process is completely finished. The amputation stump 4 is then withdrawn from the prosthesis, and the edges are trimmed and polished. Relief pads 8 and insulating sheath 9 are then removed. From 1 to 3 stump stockings 12 are drawn onto the amputation stump 4, and suitable pressure pads 10 are placed under the outer stump stocking 12 in the desired position (Fig. 4). The user then places stump 4 with stump stockings 12 and pads 10 into position in the prosthesis. While weight or pressure is applied, a knee strap Is positioned and fastened to the leg shell (Fig. 1). This anchors the prosthesis to the user's stump 4 with a strap and buckle around the thigh just above the knee cap. The user can now try walking with the prosthesis, while at the present point in time the foot part is merely spot-glued. If fine adjustment of the alignment of the prosthesis is desired, the foot part 6 may be moved/displaced relative to leg shell 1 before it is again spot-glued, as foot part 6 is somewhat oversized. When optimal alignment has been attained, foot part 6 is glued permanently and excess material is removed. When optimal pressure distribution in the prosthesis casing has been achieved, the pressure pads 10 are securely glued permanently into the inner walls of the prosthesis casing to provide pressure on the correct areas of the stump. The prosthesis is now finished and may be walked on.

An alternative to the above fitting technique is the replacement of the stump stockings made of cotton with stump stockings of rubber/polyurethane. The pressure pads are sized and glued securely to the outer surface of the stump stocking in a suitable position. This stump stocking with pressure pads mounted thereon Is used as a part of the prosthesis. A thin stump stocking, for example of nylon, is drawn onto the outside of the stump stocking of rubber/polyurethane before the stump is placed into the prosthesis.

The advantage of the present method of fitting prostheses is that it is now unnecessary to go the route of making a plaster casting of the user's stump. This also obviates the need for forming a positive model of the user's stump, and for casting of individual casings. Therefore, the user does not have to wait after measurements are taken until final fitting is done. There are also considerable savings in time, for it is possible to complete a fitting, including adjustments, in about 1 hour. The need for tools and materials is also minimal. Standardization results in a dramatic reduction in production expenses. The fitting technique further reduces the variations in the quality of fit that are dependent on the skill of the professional who does the work.

Claims

P a t e n t C l a i m s

1. A method for fitting prostheses directly on users, c h a r a c t e r i z e d i n that there are used prefabricated prosthesis casings which are filled with casting substance (11) and which are formed directly on the user while employing relief pads (8) and pressure pads (10) to attain optimal fitting of the prosthesis.

2.

A method according to claim 1 , c h a r a c t e r i z e d i n that the optimal fitting takes place with the transferral of forces from the prosthesis to the body by using the above mentioned relief pads (8) and pressure pads (10).

3. A method according to claim 1 , c h a r a c t e r i z e d i n that the leg shell (1) and foot (6) are selected after measurements have been taken of the user's stump (4) and healthy bone, and foam is removed from the inner core of the shell allowing the user's stump (4) to be placed sufficiently far down in the leg shell (1).

4.

A method according to claim 1 , c h a r a c t e r i z e d i n that self-adhesive relief pads (8) are fastened to areas exposed to pressure, and a relief pad (8) is placed at the bottom of an insulating sheath (9) that is drawn onto the stump (4).

5. A method according to claim 1 , c h a r a c t e r i z e d i n that a two-component casting substance (11) is filled into the cavity of the leg shell (1), the stump (4) with an outer insulating sheath (9) is placed into the prosthesis and pressed down to a desired position, the user then assumes an optimal position which is maintained until the entire hardening process is finished, the stump (4) is withdrawn from the prosthesis, the insulating sheath (9) and relief pads (8) are removed, and finally the edges of the casing are trimmed and polished.

6. A method according to claim 5, c h a r a c t e r i z e d i n that the user then draws onto the stump (4) 1-10 stump stockings (12), preferably 1-3 stump stockings (12), that pressure pads (10) are placed under the outermost stocking (12) in the desired position, and the stump (4) is placed into the prosthesis, that a knee strap is then fastened to the leg shell (1), and the user tries walking with the prosthesis.

7. A method according to claim 6, c h a r a c t e r i z e d i n that the alignment of the prosthesis is finely adjusted by moving/displacing the foot part (6), which is spot-glued, relative to the leg shell (1), and when optimal alignment has been attained, the foot part (6) is permanently glued; then on attainment of optimal pressure distribution in the prosthesis casing, the pressure pads (10) are securely glued permanently into the inner walls of the prosthesis casing to provide pressure where it is tolerated best.

8.

A prosthesis consisting of an outer weight-bearing shell and an inner core in a light foam material, c h a r a c t e r i z e d i n that it is fitted by filling up the leg shell (1) with a casting substance (11), whereupon the user places the stump (4) down into the leg shell (1), and that an optimal fit is then attained through the use of relief pads (8) and pressure pads (10).

9.

A casting substance for use in the method and the prosthesis according to claims 1-8, c h a r a c t e r i z e d i n that it consists of a plastic material, preferably a cold-hardening polyurethane based elastomer with a setting time of 60-180 min. , preferably 10-20 min.