GB2248780A - Apparatus and method for use in the manufacture of a lower limb prosthesis - Google Patents

Abstract

Apparatus for locating anatomical reference positions on an amputee requiring a lower limb prosthesis, the reference positions being used in the manufacture of a stump socket for the prosthesis, includes a support structure having a baseplate (10), footplate (12), and first and second upright support posts (14 and 16). Attached to the first support post (14) by an upper support slider (26) is a pelvic lock (20) which is adjustable in height and has iliac crest supports (22, 28) for gripping the pelvis during anatomical reference locating steps and, if necessary, during stump casting. The iliac crest supports (22, 28) are spaced apart by an adjustable distance. A lower support slider (44) coupled to the upper support slider (26) on the first upright post (14), carries adjustable scarpa's triangle and medial soft tissue pads (60, 72) on articulated arms (56, 58). The articulated arms (56, 58) may be withdrawn from their operative position by pivoting on the lower slider (44). Lateral location elements (94) forming part of a lateral support assembly (78) are mounted on a telescopic second upright support post (16). The scarpa's triangle and medial soft tissue pads (60, 72), and the pads (102) in the lateral support assembly (78), may all be adjusted and locked to the required positions on the amputee's stump and then withdrawn to allow access to the stump. They are then returned to their set positions to aid in forming the cast. <IMAGE>

Description

APPARATUS AND METHOD FOR USE IN THE MANUFACTURE OF A LOWER LIMB PROSTHESIS This invention relates to apparatus for locating and/or recording anatomical reference positions for the manufacture of a socket for a lower limb prosthesis and to a method of using such apparatus.

The most commonly used technique for making an aboveknee socket for a lower limb prosthesis involves the preparation of a negative cast of the amputee's stump using plaster of Paris, from which a positive impression is moulded. The positive impression is then used as a mould to fabricate a socket (stump interface) which is commonly a thermoplastics socket.

There is a trend towards a vacuum-formed thermoplastics socket which has a more anatomical shape, unlike the traditional rectangular shape of the quadrilateral socket.

The new socket also incorporates a positive skeletal lock insofar as the medial/proximal wall of the socket is shaped around the pubic/ischial ramus and the lateral wall maintains the femur in adduction. This locking system promotes greater control of the pelvis during walking.

Such a socket has been referred to as an "I.C." socket (ischial contained) or "CATCAM" (Contoured Adducted Trochanteric Controlled Alignment Method) socket or a socket employing "Ischio-Ramus Containment" or "IRC".

The manufacture of an IC socket requires the prosthetist to apply pressure to the stump during formation of the cast referred to above in order that the socket is of the correct shape to apply sufficient forces on the stump so as to obtain the desired relative orientation of the pelvis and femur when walking. This manipulation of the stump and the simultaneous forming of the cast is a particularly skilled process and, due to the care that must be taken, can involve the amputee in standing on his or her sound leg for a considerable period, resulting in the patient being unable to maintain the position necessary to obtain a cast of the optimum shape.

The present invention aims to alleviate this problem by means of apparatus for locating anatomical reference positions used in the manufacture of a stump socket for the prosthesis, wherein the apparatus comprises a support structure, and mounted on the support structure, (a) a plurality of location elements which are adjustable in position to engage the amputee at the anatomical reference positions, (b) means for preserving adjusted positions of the location elements, and (c) an adjustable pelvic lock.

The location elements may be locked at respective settings to record their locations and are preferably so mounted as to be retractable from the said locations with the settings maintained whereby the elements can, if necessary, be returned to those locations without repetition of the adjustments.

The pelvic lock preferably comprises a pair of pelvic supports for engaging the iliac crests on both sides of the amputee. In order to suit a variety of amputees, these components are adjustable in height and the spacing between them is also adjustable. Once adjusted they can be fixed in position so that the pelvis is substantially prevented from moving in the anterior-posterior direction, laterally, or rotationally with respect to the support structure.

The support structure is preferably an upright support member in the form of a post attached to a horizontal base upon which the amputee stands. One of the pelvic supports may be mounted on the post so as to be adjustable in height only, while the other may be fixed on one or more transversely extending members mounted for transverse sliding movement with respect to the post.

The location elements may comprise one or more lateral supports situated on the opposite side of the apparatus from the post for engaging the prosthetic side of the amputee above and below the greater trochanter, a medial element shaped for location and, if necessary support of, preferably, the medial musculature and soft tissue, and an anterior element, preferably for location in the scarpa's triangle. In the preferred embodiment of the invention the lateral support or supports are mounted on a second upright member, in the form of a post pivotally attached to the support structure base so that this second post, together with the lateral support or supports, may be swung outwardly away from the patient once required settings have been established.At the top of the second post a laterally adjustable bar or tube which extends in the medial direction and supports at its medial end a pair of slotted plates for mounting, preferably, a plurality of lateral supports. The slotted plates extend upwardly and downwardly respectively from the adjustable bar or tube, the slots providing for adjustment of the position of the lateral supports which, typically, take the form of a plurality of self-locking probes. By arranging for the height of the adjustable bar or tube to be variable, its end may be set so as to be in registry with the greater trochanter and the probes mounted in the upper and lower plates may be arranged to bear on the amputee directly above the greater trochanter and at selected levels on the lateral side of the femoral shaft.

The slotted plates are preferably each pivotable about one or both of a anterior-posterior axis and a medial-lateral axis for setting to a required ilio-femoral angle and to required limb flexion or pelvic tilt angles respectively.

The medial and anterior locating elements may be pads mounted on articulated arms which are, in turn, mounted on the first-mentioned post, each arm being attached at one of its ends to a mechanism adjacent the post to allow swivelling of the arm away from the amputee whilst preserving location settings.

The invention also includes a method of defining anatomical references using the above described apparatus, comprising the steps of locating the amputee in a standing position adjacent the support structure, bringing the pelvic lock into engagement with the amputee's iliac crests to restrict movement of the pelvis, moving the locating elements into engagement with predetermined parts of the amputee's body and setting their positions to locate and/or record the relative locations of the said parts. For preparing a cast of the stump, firstly the location elements are moved away from their positions on the amputee's body, with the settings preserved, to allow access to the stump, secondly casting material is applied to the stump, and thirdly the location elements moved back to the set locations.In this way, the casting material is shaped and supported by the location elements and held in a required anatomical position. This leaves the prosthetist's hands free to shape the cast in the region of the ischium and ramus and to effect minor tissue positioning, for example.

When the material has set, the location elements and the pelvic lock are removed, and the cast is removed.

The invention will now be described by way of example with reference to the drawings in which: Figure 1 is a perspective view of apparatus in accordance with the invention with a pelvic lock and location elements in their operative positions; Figure 2 is a partly sectioned plan view of the pelvic lock; Figure 3 is a partly sectioned plan view of two location elements and their supporting members; and Figure 4 is a front elevation of components for securing the pelvic lock and location elements to an upright post of the apparatus.

Referring to the drawings, apparatus which may be used for recording anatomical references for the manufacture of a socket for a lower limb prosthesis, and in particular as an aid in producing a cast of the amputee's stump, comprises a support structure having a baseplate 10, a raised footplate 12, a first upright post 14 fixed to one side of each of the baseplate and the footplate, and a second upright post 16 pivotably mounted on one side of the base plate 10 and locked in a vertical position by a pedal operated catch 18. The catch 18 allows the second upright post 16 to be swung outwardly from its operative upright position when required.

Referring to Figure 1, in use of the apparatus the amputee stands on the footplate 12 with his or her sound leg adjacent the first post 14. Thus, if the sound leg is the right leg, the amputee would face towards the left and towards the viewer when viewed in the same direction as the viewing direction of Figure 1. Conversely, if the sound leg is the left leg, the amputee faces to the right and away from the viewer. The pelvis is held in position by a pelvic lock 20 having te following components which are shown in Figures 1 and 2. Firstly, a first pelvic support in the form of a cupped thermoplastics plate 22 oriented so that its concave surface faces downwardly and medially of the amputee is mounted by means of an intermediate spacer 24 on an upper support slider 26 mounted for vertical sliding movement on the first upright support post 14.A second pelvic support in the form of a second, identical thermoplastics plate 28 facing the first plate 22 is mounted in a fixed position on a pelvic lock support frame 30 attached to the upper support slider 26. As will be seen from Figure 1, the frame 30 includes a U-shaped bar 32 with first and second parallel arms 32A, 32B each slidably supported in a respective horizontal support member 34, 36 so that the plate 28 is supported by members passing both to the anterior and to the posterior of the amputee, and is adjustable towards or away from the plate 22. Once the correct spacing of the pelvic supports 22, 28 for a particular amputee is found, the arms 32A, 32B may be clamped in the supporting members 34, 36 by means of screw clamps having operating knobs 38, 40.

As already mentioned, the upper support slider 26 is slidable vertically on the first post 14. It can also be clamped on the post 14 by means of a screw clamp 42, best seen in Figure 4. Rotation is prevented by key 14A engaging a keyway in slider 26 (see Figure 2). A similar, lower support slider 44 with a keyway engaging key 14A (see Figure 3) is also slidably mounted on the post 14, beneath the upper support slider, and is connected to the latter by a vertical screw 46 having a hand wheel 48 (see Figure 4).

The screw 46 is housed in a bearing in the lower support slider 44 and is threaded in the upper support slider 26 so that operation of the screw has the effect of raising or lowering the lower support slider 44 with respect to the upper support slider 26. It will be understood that when the upper slider 26 is raised or lowered according to the height of the amputee's iliac crests, the lower slider moves up and down in the same way. To aid such movement, the assembly of the upper and lower sliders 26, 44 is connected to a counterweight (not shown) located inside the post 14, which is tubular, by means of a cable 50 passing around a pulley 52 mounted on the top of the post 14. The cable is attached to the top surface of the upper slider 26.A guard 54 attached to the inwardly facing surface of the upper slider 26 extends downwardly to cover the lower slider 44 in order to protect the amputee from the slider mechanism.

With reference to Figures 1 and 3, the lower support slider 44 supports two articulated arms 56, 58, one to the anterior and one to the posterior of the amputee. For the purposes of the present description and drawings, it is assumed that the apparatus is configured for an amputee whose amputated limb is the left limb, so that articulated arm 56 is an anterior arm and articulated arm 58 is a posterior arm.

Each articulated arm comprises a tubular first arm portion 56A or 58A which mounts a respective adjustable second arm portion 56B or 58B. Carried on one end of the adjustable arm portion 56B of the anterior articulated arm 56 is a scarpa's triangle location element 60, mounted by means of a ball joint 62. The adjustable second arm portion 56B is coupled to the first arm portion 56A by means of a housing 64 which is rotatably and slidably adjustable on the first arm portion 56A. In addition, the adjustable arm portion 56B is rotatable and slidable longitudinally in the housing 64. Rotatable knobs 64A, 64B on the housing 64 are provided to lock the relative position of the arm portions 56A, 56B once they have been set.The complete assembly of the articulated arm 56 and scarpa's triangle location element 60 is pivotable from the operative position shown in Figures 1 and 3 about a vertical axis defined by a pin (not shown) in the lower slider 44 to an inoperative position in which it is withdrawn from the amputee. A spring loaded plunger 66 in the lower slider locks the assembly in the operative position.

he posterior articulated arm 58 is similarly constructed, having a housing 68 which is identical to the housing 64, for connecting the first and second arm portions 58, 58B, and further having a respective plunger 70 for locking the articulated arm 58 in its operative position.

In this case, however, the second arm portion 58B mounts a medial/posterior location element 72, also mounted by a ball joint 73. The adjustable arm portion 58B is kinked so that its distal end can be adjusted to be more nearly perpendicular to the normal orientation of the medial/posterior location element 72. Knobs 68A and 68B are provided on the housing 68 to lock adjustments.

The range of adjustments provided by the housings 64, 68 allows each adjustable arm portion 56B, 58B to be moved transversely along the tubular first arm portion 56A, or 58A, to be tilted up or down about the first arm portion 56A, 58A, or to be extended or retracted in the housing 64, 68, so that the scarpa's triangle location element 60 can be manoeuvred to bear against the amputated thigh in the region of the scarpa's triangle. Likewise, the medial/posterior location element 72 can be adjusted to bear against the medial soft tissue immediately below the ischium.

The scarpa's triangle location element 60 is a thermoplastics rounded kite-shaped plate mounted generally perpendicularly on the end of the adjustable arm portion 56B, while the medial/posterior soft tissue element 72 is a concave generally oval element mounted on the kinked end portion of the arm portion 58B.

Up to this point in the particular description, we have described components which are attached to the first support post 14. Attention is now directed to those attached to the second support post 16 located on the amputated side of the amputee.

Referring to Figure 1, at the upper end of the second support post 16 there is a clamp housing 74 for a laterally extending circular section tube 76, the position of which in the housing 74 may be locked by means of a clamp having a clamp handle 74A. l:vunted on the medial end of the tube 76 is a lateral support assembly 78 having upper and lower pivotable plates 80, 82 each adjustably pivotable about a horizontal and anterior-posterior axis on a bush 84 mounted on the tube 76.

The degree to which the slotted plates can be pivoted with respect to the bush is limited in each case by a respective bolt 86 (only one is visible in Figure 1) housed in the bush 84 and projecting on the medial side of the bush to engage stop surfaces (not shown) on the respective plates 80, 82. Location of the bolts serves as a means of adjusting the angular position of each slotted plate with respect to the vertical, radial studs 90, 92 secured in the bush 84 defining the pivot axis. The tube 76 is, itself, rotatable in the clamp housing 74 of the post 16.

Both the upper and lower plates 80, 82 are slotted to receive lateral location supports 94 on the amputee's amputated side. Each lateral support extends generally in the lateral-medial direction and comprises a serrated central rod 96 slidable within a sleeve 98 received in the respective slotted plate 80, 82. Each rod 96 is provided with a small ball joint 100 mounting a respective curved thermoplastics pad 102.

One of the lateral supports is housed in an arcuate slot of the upper plate 80, while three others are housed in the lower slotted plate 82. Each sleeve 98 is held in its respective slot by means of a respective constant friction device 98A threaded on the end of the sleeve, allowing the sleeve to be moved and set at the required position. Each rod 96 is self-locking in its respective sleeve 98 by means of a releasable spring-loaded ratchet device (not shown) in the sleeve which engages the serrations of the rod. When the ratchet device is engaged, the pad 102 can be pushed towards the amputee, but is prevented from moving away.

Release of the ratchet device allows movement of the pad 102 away from the amputee.

It will be noted that the whole lateral support assembly 78 may be raised or lowered by virtue of the second support post 16 being telescopic, the height being set by locking clamp 104. An ilio-femoral angle is set by adjustment of the bolts 86, while the required degree of hip extension/flexion is set by adjusting the position of the uppermost location element 94 in the arcuate slot of the upper plate 80 and by rotating the tube 76 in the clamp housing 74.

In order to be able to record the positions of the location elements 60, 72, and 94, graduations in the form of linear and angular scales (not shown) may be marked on the connecting structures, for instance on the arm portions 56A, 56B, 58A, 58B, on the rods 96, the tube 76, and if necessary on the posts 14, and 16.

A technique for casting an impression of the amputee's stump using the above apparatus will now be described as series of numbered steps.

1. Prepare Patient: a) explain procedure to patient; b) lubricating cream; c) cling film; d) prosthetic casting pants.

2. Measure Patient: a) greater trochanter height or iliac crest height; b) mark anatomical references (e.g. adductor tendon, femur end, etc).

3. Pre-Adjust Frame: a) set up apparatus for right or left sided amputee; b) set height of greater trochanter reference (tube 76) on second support post 16 using clamp 104; c) select initial position of medial soft tissue and scarpa's triangle plates 72, 60.

4. Aid Patient onto Frame: a) pelvic supports 28 and U-shaped bar 32 removed; b) scarpa's triangle and medial soft tissue pads 60, 72, disengaged using plungers 66, 70.

5. Locate Sound Side: a) pelvic support 22 onto iliac crest; b) position foot on footplate 12.

6. Locate Prosthetic Side: a) locate pelvis: i) fit pelvic support 28 and U-shaped bar 32; ii) locate pelvic support 28 on iliac crest; b) locate lateral support assembly 78: i) locate distal border of greater trochanter with uppermost location element 102 of location elements which are fitted to lower slotted plate 82; ii) set ilio-femoral angle and desired flexion/extension using bolts 86 and clamp 74 for tube 76; iii) contour lateral aspect pads (rods 96) as necessary.

7. Locate Medial Soft Tissue Support Plate 72: a) adjust to locate to medial soft tissue.

8. Locate Scarpa ' s Pad 60: a) locate into scarpa's triangle.

9. Lock all Adjustments: a)- step off to allow for plaster thickness (3-5mm approx.) and lock adjustments; b) check anatomical references (see step 2b above); c) record settings using graduated scales.

10. Remove Pre-Set Location Elements: a) lateral support assembly 94; b) scarpa's triangle element 60; c) medial soft tissue plate 72.

11. Apply Plaster Bandage: a) pelvic wrap b) stump wrap; c) medial slab.

12. Relocate Location Elements: a) medial soft tissue element 72; b) lateral support assembly 94; c) scarpa's triangle pad 60.

13. Hand Moulding: a) as required for each individual cast; b) hand mould ischium/ramus.

14. Remove Supports: a) medial soft tissue element 72; b) scarpa's triangle element 60; c) lateral support assembly 94.

15. Remove Cast: a) remove elastic suspension; b) cut anterior/medial aspect; c) gently pull downwards.

16. Aid Patient from Frame.

It will be noted that step 9 in the above procedure includes recording the settings of the location elements.

In practice, this may be done at different times, and in the case of preparing a cast of the stump, may, in some cases, be omitted altogether.

The apparatus may also be used simply to measure the relative positions of the anatomical references as the basis for alternative socket production methods. In particular, it is possible to include devices for generating digital data representing the positions of the anatomical references using digitisers associated with the mechanical linkages supporting the location elements, for dse in the ultimate production of a socket using numerically controlled machinery.

Claims (19)

1. Apparatus for locating anatomical reference positions on an amputee requiring a lower limb prosthesis, the reference positions being used in the manufacture of a stump socket for the prosthesis, wherein the apparatus comprises a support structure, and mounted on the support structure, (a) a plurality of location elements which are adjustable in position to engage the amputee at the anatomical reference positions, (b) means for preserving adjusted positions of the location elements, and (c) an adjustable pelvic lock.

2. Apparatus according to claim 1, wherein the pelvic lock comprises a pair of pelvic supports arranged in a spaced apart opposing relationship for engaging the iliac crests of the amputee.

3. Apparatus according to claim 2, wherein the spacing between the pelvic supports is adjustable.

4. Apparatus according to any preceding claim, wherein the support structure comprises a base and an upright support member attached to the base, and wherein the pelvic lock and at least some of the location elements are slidably mounted on the support member for height adjustment.

5. Apparatus according to claim 4, wherein the pelvic- lock and the location elements mounted on the support member are connected together so as to be slidable together on the support member.

6. Apparatus according to claim 5, wherein the spacing between the pelvic lock and the location elements mounted on the support member is adjustable.

7. Apparatus according to claim 2 or claim 3, wherein the support structure comprises a base and an upright support member mounted on the base, and wherein one of the pelvic supports is mounted on a support slider slidably mounted on the upright member, and the other pelvic support is mounted on a transversely extending member carried by the support slider, the arrangement of the transverse member being such that the said other pelvic support is slidable transversely with respect to the said one pelvic support.

8. Apparatus according to claim 7, wherein the transversely extending member comprises a pelvic lock support frame having an anterior arm and a posterior arm to the anterior and posterior respectively of the upright support member, the said other pelvic support being connected to the upright support member through both arms.

9. Apparatus according to any of claims 1 to 3, wherein the support structure comprises a base, a first upright support member mounted on the base, an upper support slider mounted for sliding adjustment on the upright support member and carrying the pelvic lock, and a lower support slider mounted for sliding adjustment on the upright support member, the lower support slider carrying (i) a transversely extending anterior articulated arm having at one end a scarpa's triangle location element, and (ii) a transversely extending posterior articulated arm carrying a medial/posterior location element.

10. Apparatus according to claim 9, wherein the support structure comprises a second upright support member mounted on an opposite side of the base from the first upright support member, and wherein the location elements include a plurality of lateral location elements carried by the second upright member.

11. Apparatus according to claim 9 or claim 10, wherein the articulated arms are pivotable with respect to the lower support slider about a generally upright axis between respective operative and inoperative positions, the lower support slider including means for locking the articulated arms in their operative positions.

12. Apparatus according to claim 10, including means for individually locking the lateral location elements in adjusted positions.

13. Apparatus according to claim 10 or claim 12, wherein the second support member is pivotable with respect to the base between an operative and an inoperative position, the apparatus further including locking means for locking the second support member in the operative position.

14. Apparatus according to any of claims 7 to 13, including a counterweight arranged to exert an upward pulling force on the support slider carrying the pelvic lock.

15. Apparatus according to claim 14, wherein the first upright support member is a vertical tube, and the counterweight is suspended inside the tube.

16. A method of defining anatomical references on an amputee requiring a lower limb prosthesis using apparatus according to any preceding claim, comprising locating the amputee in a standing position adjacent the support structure, bringing the pelvic lock into engagement with the amputee's pelvis to restrict movement thereof, moving the locating elements into engagement with predetermined parts of the amputee's body and setting their positions to locate and/or record the relative locations of the said parts.

17. A method according to claim 16 for preparing a cast of the stump of the amputee, in which the location elements are moved away from their positions on the amputee's body to allow access to the stump, casting material is applied to the stump and, with the pelvic lock applied, the location elements are moved back to their set positions to bear against the casting material before it has hardened, and, when the casting material has hardened, the location elements are again moved away from the amputee's body to allow removal of the cast, and the pelvic lock is removed from the iliac crests.

18. Apparatus for locating anatomical reference positions on an amputee requiring a lower limb prosthesis, the apparatus being constructed and arranged substantially as herein described and shown in the drawings.

19. A method of using apparatus according to claim 1, the method being substantially as herein described.