Method for molding an amputation stump and impression aid for such a method

Description

[0001] The invention relates to a method for molding an amputation stump, wherein the amputation stump is inserted into a liner of an impression aid, wherein the liner has a longitudinal direction and a perimeter. The invention also relates to an impression aid for such a method.

[0002] In lower extremity prosthetics, the prosthetic socket plays a crucial role as the interface to the body. Accordingly, molding the amputation stump, also known as the prosthetic stump, is a crucial process for the subsequent fit of the prosthesis.

[0003] Despite advances in non-contact impression methods (scanning), today's practice is dominated by the use of plaster to create a negative cast of the stump. In addition to its low cost, this method has the advantage that experienced orthotists can influence the future socket shape by specifically shaping the stump during the plaster casting process. This is particularly true if the socket is to have specific stress zones. This advantage is lost if the socket is to bear the entire surface of the stump or if less experienced technicians are taking the impression. Therefore, there has been increasing interest in methods that exert even pressure on the stump during the impression process.These include the inflated bladder molding method promoted by Össur, which is taught in EP 0 954 258, the sand molding method developed by Northwestern University in Chicago (Prosthetics and Orthotics International, March 2009; 33(1): 1-9), and the flexible membrane molding method developed by the University of Strathclyde, which uses a water tank to create a flexible membrane molded into a flexible membrane (https: / / givenlimb.org / improved-casting-method-for-leg-prosthetics / ). The latter two methods have the additional advantage that the residual limb can be loaded during the molding process, which promotes a load-adapted socket shape and can give the user an impression of the wear behavior during the molding process.

[0004] WO 2008 / 092617 A1 discloses an impression aid comprising a plurality of molded parts arranged so that they can be moved and rotated. This is intended to allow the shape of the stump to be recorded. However, it is disadvantageous that this cannot be done while the stump is under load, and the shape cannot be captured by optical methods. The applicant used the "anatomical SIT-Cast" system, in which the shape of the stump was recorded using an impression aid featuring a ring into which the stump is inserted. The stump is first covered with a plaster compound and a rubber sleeve. Experience shows that this results in suboptimal loading of the stump.

[0005] A particular disadvantage of the latter two methods is that, due to their design, they are not very portable and therefore offer little benefit in everyday clinical practice. With all three methods, it is not possible to manually influence the impression result. A combination with optical scanning methods, which are increasingly used in modern prosthetics, is also not possible.

[0006] WO 2016 / 135320 A1 discloses a device for creating a plaster cast of a limb stump. It comprises a pressure vessel into which a stump, preferably covered with plaster, is inserted. The fluid is then intended to exert uniform pressure on the stump. However, the disadvantage is that subsequent deformation of the plaster or the stump is not possible, and the stump cannot be optically recorded and measured.

[0007] US Pat. No. 7,410,350 B2 shows a device in which a plaster-encased amputation stump is inserted into a container, so that expander elements arranged in the container exert pressure on the amputation stump. This is intended to eliminate the disadvantages of a solution in which a plaster-encased stump, after an initial curing phase in which the stump is not fully cured, is held in a ring and subjected to weight by the patient.

[0008] US 1 335 475 A and US 5,432,703, as well as GB 2 188 846 A, disclose methods and devices used for producing a plaster cast of an amputation stump or for producing a solid object, such as a prosthetic socket. EP 0 765 646 A1 describes a prosthetic liner made of silicone. WO 2014 / 032815 A1 also describes a prosthetic liner designed to prevent a portion of the amputation stump from protruding from the frame socket window when the liner is worn for extended periods in a frame socket.

[0009] The present invention is therefore based on the object of creating a method for molding an amputation stump and an impression aid for prosthetic stumps, which exert a uniform pressure on the stump during the molding process, can preferably be loaded by the user during the molding process, are easy to handle and transport and allow direct access to the surface for the purpose of reshaping during the molding process, or for optically scanning the surface topography instead of physically taking a mold.

[0010] The invention solves the stated problem by a method for molding an amputation stump, wherein in the method the amputation stump is introduced into a liner of an impression aid, wherein the liner has a longitudinal direction and a circumference, wherein the method is characterized in that the liner has an expansion coupling such that an extension of the liner along the longitudinal direction inevitably results in a reduction of the circumference.

[0011] A conventional liner or an elastic membrane known from the prior art is generally made of an elastic material. If the amputation stump is enclosed in such a material and is subjected to stress, for example, from above toward its distal end, this leads to an elastic deformation of the liner or membrane, which primarily consists of an extension along the longitudinal axis. This means that the liner or membrane is stretched along its longitudinal axis. This is possible with an elastic material without radial forces occurring. In contrast, the liner according to the molding method of the present invention provides that an extension of the liner along its longitudinal direction inevitably results in a reduction in its circumference.Consequently, if the amputation stump is loaded in the liner, the liner is lengthened longitudinally and its circumference is reduced, resulting in a radial force acting on the stump. The special design of the liner thus ensures a uniform and full-surface loading of the amputation stump in the radial direction.

[0012] Preferably, the patient applies a load to the amputation stump after it has been inserted into the liner. This load causes the liner to lengthen, which, due to the liner's special design, reduces its circumference and thus exerts a radially inward force on the stump. This ensures excellent loading of the stump during the impression process.

[0013] Before being inserted into the liner, the amputation stump is preferably covered with an impression material, such as plaster, and preferably with a separating layer, in particular a separating film. The impression-taking process then occurs when the user places the stump, covered with the impression material and, if applicable, the separating film, into the liner and exerts tension on the distal end of the liner by applying a load, thereby lengthening the liner. The insertion or placement of the stump or amputation stump into the liner can also be referred to as insertion.

[0014] Due to the tensile force exerted on the liner end and the coupling of the liner's expansions, the liner now completely encloses the amputation stump and exerts a circumferential pressure on the stump that is advantageously proportional to the longitudinal load of the liner.

[0015] Alternatively, or in addition, the amputation stump can be optically measured after insertion into the liner. This involves the patient applying the load to the amputation stump. This load, as already described, exerts tension on the distal end of the liner, thus creating circumferential pressure on the amputation stump.

[0016] Preferably, after the amputation stump has been inserted into the liner, the amputation stump and / or the impression material are deformed in order to achieve the advantageous effects already described.

[0017] The invention further achieves the stated object by means of an impression aid for a method described herein. This is achieved via the liner described herein with the expansion coupling described, which is held in a height-adjustable holding device. The liner advantageously comprises or consists of a braided tube or a net of preferably intersecting fibers. When the liner is unloaded, the fibers advantageously run at an angle of 45° to the longitudinal direction of the liner. This is referred to as a diagonal fiber orientation. An exact angle of 45° is not necessary as long as the desired coupling between the longitudinal expansion and the reduction in circumference is achieved. The force exerted on the amputation stump, which is caused by an extension of the liner along its longitudinal direction, can be adjusted via the angle between the fiber orientation and the longitudinal direction of the liner.The flatter the fibers are, i.e. the closer the described angle is to a right angle, the greater the force that occurs in the radial direction when loaded along the longitudinal direction.

[0018] Advantageously, the liner is held in a fastening ring. In a preferred embodiment, the liner is held in a ring-shaped manner at its proximal end.

[0019] To allow the amputation stump to be oriented as freely as possible, the holding device, especially the proximal fixation ring, can be positioned so that a uniform longitudinal force is applied across the entire circumference of the liner. Various solutions are conceivable for this: The fixation ring can be mounted on a gimbal. The fixation ring can have a spherical support mounted in a correspondingly shaped ring. The fixation ring can be mounted on at least two angled links or leaf springs, which, due to their multi-joint kinematics, allow the fixation ring to pivot. The fixation ring can allow the liner to be tightened during the fitting process so that the liner can align itself according to the orientation of the residual limb and, due to the fixation at the proximal edge, follows the orientation of the residual limb.

[0020] According to the invention, the holding device is height-adjustable. This allows for particularly easy adjustment to accommodate patients of different heights and amputation stumps of different lengths.

[0021] For this purpose, a variable clamping device is advantageously provided for the proximal edge of the liner. In this preferred, particularly simple solution, the liner can be folded around a loose ring at the proximal end and then guided distally within the fastening ring. By pulling on the liner edge distally, the liner can be brought into contact with the residual limb while the user is standing on one leg. The double deflection of the liner secures it in the fastening ring and allows the user to bear loads.

[0022] Preferably, the liner is deflected around a ring and guided back onto itself, with the ring and liner resting on a holding device. This particularly simple method of attaching the liner enables a structurally simple and thus cost-effective molding aid. The holding device is advantageously attached to a support device, for example, a column, and is advantageously pivotally mounted. This allows the holding device to be advantageously pivoted about the longitudinal direction of the support device.

[0023] In a preferred embodiment, the holding device is arranged in a foldable manner on the support device. This allows it to be brought into a use position, in which the patient can step into a liner arranged in the holding device and insert their amputation stump into the liner, and into a transport position, in which the holding device is, for example, folded onto the support device in order to reduce the required installation space. Advantageously, the holding device engages in locking elements, preferably notches, of the support device, or clamps or wedges itself into the support device, particularly in one of these positions, advantageously in a folded-down position corresponding to the use position. This achieves sufficient stability and virtually eliminates incorrect operation.

[0024] The support device, in particular the fastening ring, should be attached in such a way that an orthotist has good access. At the same time, the support device is advantageously height-adjustable and replaceable. In this way, for example, different sizes of fastening ring can be used. To enable easy transport, it is helpful if the entire impression aid is foldable, so that it can be easily stored in a workshop, for example, and transported in everyday clinical use. In a preferred embodiment of the invention, the holding device, in particular the fastening ring, is therefore foldably attached to a vertical column. For this purpose, for example, a hinge and a lockable clamp around the column can be provided. In a preferred solution, the holding device generates the forces for locking it itself by loading the fastening ring.For this purpose, the fastening ring can, for example, engage in notches in the column when folded down. With an appropriate design, it is also possible to lock it using frictional forces alone, which enables continuous height adjustment. The column of the impression aid can also be designed so that it can be removed from its attachment, for example on a base plate, for storage and transport. A detachable connection, for example a plug-in connection, can be provided for this purpose. In a further preferred embodiment, the column is connected to the base plate via a hinge. It can be pivoted into the desired position. The working position of the column preferably forms the stop for such a pivoting movement, so that the column assumes a stable, preferably vertical position during the impression process. For storage or transport, it can, for example, be pivoted against the base plate.

[0025] The liner, which is made in particular from a liner material, preferably has a plurality of fibers arranged in the liner material. These fibers are preferably made of an inelastic material. The liner can have several, preferably two, fiber layers comprising a plurality of fibers that advantageously run parallel to each other in a fiber layer, at least over a certain area. As long as the fibers of the different fiber layers cross each other, the desired effect of coupling the strains can also be achieved in this way.

[0026] Additionally or alternatively, the fibers can also form a spiral matrix. The liner has first fibers that form a spiral matrix in a first circumferential direction and second fibers that form a spiral matrix in a second circumferential direction opposite to the first circumferential direction. In this case, "spiral" means that the respective fiber extends, preferably in several turns, around the circumference of the amputation stump and thus of the liner when the liner is in contact with the amputation stump.

[0027] Advantageously, the fibers arranged in the liner material intersect at a right angle. This is especially true if there is no amputation stump in the liner. This angle can be shifted by inserting a stump and, in particular, by applying weight.

[0028] Of course, the liner can also consist of several sub-liners, each with only one fiber layer with a single fiber direction. As an alternative to intersecting fibers, hexagonal meshes of inelastic fibers can also be embedded in the liner material. Of course, other meshes that exhibit the desired properties are also possible. This means that an extension of the mesh in one direction inevitably results in a shortening of the mesh in the other direction.

[0029] Embodiments of the present invention are explained in more detail below with reference to the accompanying drawings. They show: Figures 1 a and b - schematic representations of a liner and an amputation stump before and after insertion; Figures 2 a and b - schematic drawings of the mode of action of securing the liner; Figure 3 - the schematic representation of an impression aid with inserted amputation stump; Figure 4 - the schematic representation of an impression aid in the transport position; Figures 5 to 8 - various stages in a method for taking an impression according to an embodiment of the present invention and Figures 9 and 10 - two illustrations in different stages of a method according to a further embodiment of the present invention.

[0030] Fig. 1shows a schematic of the function of the coupling of longitudinal and transverse expansion in the liner (2) while the prosthetic stump is accommodated. This is attached to the attachment ring (3) and consists - as indicated by the surface texture - of a net or braid with diagonal fiber orientation. Longitudinal deformation of the liner results in an increased orientation of the fibers in the longitudinal direction, which simultaneously reduces the circumference of the liner. The deformation of the liner comes to a halt when the stump (1) is completely enclosed. When the stump is loaded, a uniform pressure is exerted on the stump. The liner consists of a braided tube made of yarn or monofilaments or a mesh in the form of a tube with a diagonal course of the threads or with a hexagonal structure. Braided tubes made of polyamide or polypropylene monofilaments are particularly advantageous because they are very flexible and yet form a closed surface.The size should be selected so that the stump is completely enclosed when the braided tube threads intersect at approximately 90°, or the hexagonal mesh is undistorted. Distally, the tube can be tied together or glued or welded to a flexible end cap (9). In any case, it is advisable to create a smooth surface inside distally by gluing in an elastic disc or by encapsulating the distal end with elastomer. Proximally, the liner is connected to the fixation ring (3).

[0031] Fig. 2 shows an advantageous fastening of the liner to the fastening ring (3) in a sectional view. The fastening ring (3) can be designed in a stepped manner to provide centering for the ring (4). The liner (2) is wrapped around the ring (4) and guided back onto itself within the fastening ring (3). Due to the multiple deflections, when the liner is loaded - as in Fig. 2BAs shown, this results in the ring (4) being pressed firmly against the fastening ring (3), resulting in high frictional forces that hold the liner securely in the fastening ring as long as it is under load. The advantage of this arrangement is that the liner can be oriented within the ring according to the position of the lower leg. Ideally, the liner is adjusted by pulling on the folded end on the stump to tighten it, and then the user applies a load.

[0032] Fig. 3shows a possible design of the entire impression aid. The liner (2) holds the stump (1). Its proximal end is held in the fastening ring (3). This is attached to the column (5) by means of a clamp (7). The axis (10) allows the fastening ring (3) to be folded up onto the column. When folded down, the shape creates a stop that holds the fastening ring in a horizontal position. At the same time, when the fastening ring is loaded from above, strong forces act on the column, preventing the clamp from slipping along the column. In this way, the height of the fastening ring (3) is continuously adjustable without having to release a lock. The column (5) is attached to the base plate (6) by means of a hinge. The position of its pivot point creates a stop when the column is in a vertical position, which is stabilized by loading the fastening ring (3) from above.The impression aid can therefore be used without the risk of the column swiveling backwards.

[0033] Fig. 4 shows the impression aid Fig. 3 In the folded state. The column (5) is pivoted onto the underside of the base plate (6). The fastening ring (3) is folded against the column (5). As can be seen, the impression aid is very compact in this state and can be easily transported and stored. Assembly requires only a few simple steps.

[0034] Fig. 5 shows how the amputation stump 1, which in the illustrated embodiment is covered with a modeling layer of plaster 11 and a release film, is inserted into the liner 2. In this case, a distal edge 12 of the liner 2 is folded over. The individual fibers, by which the coupling between longitudinal expansion and circumferential reduction is achieved in the liner 2 shown, are shown in the Figures 5 to 10 not shown.

[0035] This is in Fig. 6 The patient 13 is standing on his healthy leg and the stump 1 with the liner 2 is inserted into the fastening ring 3 and is held there. The patient 13 can now place weight on the amputation stump 1 and thus ensures that the liner 2 is moved longitudinally, in Fig. 6 i.e., from top to bottom. The coupling of longitudinal and transverse expansion inevitably leads to a reduction in circumference, thus resulting in a force acting on amputation stump 1 that is directed radially inward.

[0036] In Fig. 7 the situation is Fig. 6, whereby another person, for example, an orthopedic technician 14, can now shape the amputation stump 1 in the liner 2 while the amputation stump 1 is held in the fastening ring 3. This allows the layer of plaster 11 located within the liner 2 to be modeled and, if necessary, shaped or reshaped. In this way, the individual characteristics of the amputation stump 1 can be taken into account.

[0037] Fig. 8 shows the final phase in which the patient 13 stands on his or her healthy leg and applies pressure to the amputation stump 1 within the fixation ring 3. This applies the previously described force through the liner 2 to the amputation stump and the plaster molding material 11 located within the liner until the material has cured sufficiently to remove the liner from the fixation ring 3.

[0038] Fig. 9shows the situation in a method according to a further embodiment of the present invention. The patient 13 is standing on his healthy leg again and the amputation stump 1 is inserted into the liner 2. Unlike the Figures 5 to 8 However, no plaster cast 11 is arranged within the liner between the liner 2 and the amputation stump 1. The liner is again held in the fixing ring 3, but now has markings 15 that allow optical measurement.

[0039] This will be Fig. 10 The amputation stump 1 of patient 13 is located in the liner 2, which Fig. 9shown configuration. By means of a laser measuring device 16, as is known in principle from the prior art, the geometric shape of the liner 2, in which the amputation stump 1 is located, is now measured three-dimensionally. The data thus determined can be used to manufacture the prosthetic socket. The fastening ring 3 is arranged on the column 5 and is preferably height-adjustable, i.e., in particular, displaceable along the longitudinal direction of the column. In a particularly preferred embodiment, the fastening ring 3 is also pivotable against the column 5 in order to move the impression aid into the Fig. 5 to be able to bring it into the transport position shown. For this purpose, it is advantageous if the base plate 6 can also be pivoted relative to the column 5. List of reference symbols:

[0040] 1Stump 2Liner 3Fixation ring 4Ring 5Column 6Base plate 7Clamp 8Hinge 9End cap 10Axis 11Plaster 12Distal edge 13Patient 14Prosthetist 15Marking 16Laser measuring device

Claims

1. A method for making a mold of an amputation stump, in which method the amputation stump is inserted into a liner (2) of a molding aid, said liner (2) having a longitudinal direction and a circumference, characterized in that the liner (2) has an expansion coupling, such that a lengthening of the liner (2) along the longitudinal direction necessarily results in a reduction of the circumference.

2. The method as claimed in claim 1, characterized in that the amputation stump, after insertion into the liner (2), is loaded by the patient (13).

3. The method as claimed in claim 1 or 2, characterized in that the amputation stump, prior to insertion into the liner (2), is equipped with a molding material.

4. The method as claimed in claim 1, 2 or 3, characterized in that the amputation stump is measured optically after insertion into the liner (2).

5. The method as claimed in one of the preceding claims, characterized in that, after insertion of the amputation stump into the liner, the amputation stump and / or the molding material is shaped.

6. A molding aid for a method as claimed in one of the preceding claims, comprising a liner (2), that has an expansion coupling, such that a lengthening of the liner (2) along the longitudinal direction necessarily results in a reduction of the circumference, characterized in that the liner (2) is held in a retaining device, which is adjustable in height.

7. The molding aid as claimed in claim 6, characterized in that the liner (2) has or is made of a braided tube or a net of fibers.

8. The molding aid as claimed in claim 7, characterized in that the fibers, in an unloaded state, enclose an angle of 45° with the longitudinal direction of the liner (2).

9. The molding aid as claimed in one of claims 6 to 8, characterized in that the liner (2) is deflected around a ring (4) and guided back onto itself, wherein the ring (4) with the liner (2) comes to bear on the retaining device.

10. The molding aid as claimed in one of claims 6 to 9, characterized in that the retaining device is exchangeable or expandable.

11. The molding aid as claimed in one of claims 6 to 10, characterized in that the retaining device is secured on a support device.

12. The molding aid as claimed in claim 11, characterized in that the retaining device is secured foldably on said support device.

13. The molding aid as claimed in claim 12, characterized in that the retaining device in one position engages in latching elements of the support device, or is clamped or wedged onto the support device.