AU771107B2 - Splint for mobilising lower limb - Google Patents

Abstract

The invention concerns the medical field, in particular a splint characterised in that the footrest is mounted on the tibial cradle via at least a slide (11) with interposed elastic return means (34) constantly tending to return the footrest into a least extended position relative to the tibial cradle. The invention is useful for the passive mobilisation of a lower limb.

Description

SPLINT FOR MOVING A LOWER LIMB The present invention concerns the medical field and relates to the equipment used for functional orthopaedic or re-education treatments of the lower limbs.

To attain the aims mcntioncd above, the equipment proposed is generally constituted in the form of a splint comprising a base supporting an articulated structure composed of a segment or crural cradle connected by a joint to a tibial cradle or segment equipped most frequently, like the crural cradle, with a receiving and support hammock of the corresponding portion of the lower limb to be moved.

These splints, which are -articulated as opposed to fixed splints only allowing a lower limb to be rendered immobile in a specific posture, are intended for permitting at least moving on bending/extending for two of the joints of a lower limb, namely the coxofemoral joint and the knee.

To this effect, it is generally provided to mount the extremity of the tibial cradle on a carriage able to move along a longitudinal axis of the base. By means of this arrangement, it becomes possible to control the alternative sliding of the carriage, either directly via the physical action of the lower limb or indirectly by means of an autonomous motor.

This motor is generally qualified with a passive mobilisation splint given the fact that it is used to provoke bending and extending of the lower limb without the -muscular systems of said limb being able to effect this movcenent.

Thesc passive mobilisation splints are widely used in re-education methods and are generally regarded as generally satisfactory.

However, the putting into practice of this equipment does not provide optimum bending/extending functionality in certain applications or uses.

In fact, depending on the type of equipment and/or uses in practice, it has been frequently observed that the hinge pin of the crural segment on the base is not situated to exactly coincide with the anatomic axis of the coxofernoral joint and often there is- a plane shift with respect to that of the support of the base and also an shift within the samne plane.

This lack of coincidence has one particular consequence, which is that thc effective length of the crural segment between its articulation on the base and the hinge pin with the tibial segment appears longer than the length of thc bony segmcnt of the limb to be rehabilitated and more particularly longer than the length of the femur between the eoxofeinoral axis and the knee.

This fact has thc result that, from a bending situation of for example about 900 and in which the joint of the knee and the joint between the crural and tibial segments are approximately in coincidence, any movement on extending is expressed by a shift between the arcs of a circle paths described by these joint points.

Thus, there is no support between the foot and the foot-rest, and re-education conditions which owing to this are no longer optimum and bring about problems and constraints not favourable to obtaining the sought-after result.

Therefore, the problem is thus to be able to offer a solution for resolving this difficulty by providing a device overcoming this drawback to easily moving a lower limb without bringing about fatigue negatively counterbalancing the re-education results obtained by using this splint.

The object of the invention is to put forward a constructive solution to resolving said problem.

The means of the invention have been particularly designed so as to satisfy, apart from the problem mentioned above, a further requirement frequently demanded of staff responsible for placing these splints, namely the need to be able to adjust the length of the tibial segment according to the length of the corresponding bony segment of the limb to be re-cducated.

The object of the invention by using the means for adjusting the preceding problem opens a possibility for automatically adjusting this length.

The object of the invention has also been designed so as to take account of a finding frequently encountered in the field of re-education when the functional re-education treatment subsequent to a major traumnatism leaves the lower limb in a passive working level not introducing any voluntary muscular stress mainly concerning the thigh muscles.

In this case and if the re-education treatment has to be made for a relatively long period, one frequently observes a significant loss of the muscular possibilities of the quadriceps group, it then being necessary to carry out re-education by other means so as to restore the patient with a voluntary contraction reflex and the prior muscular power.

Thus, the object of the invention is to select technical means which if appropriate can be used to bring a first type of response to this loss without it nevertheless constituting a substitute for the effective and efficacious functional re-education means of the quadricep muscles.

A supplementary object of the invention is thus of providing technical means to offering several re-education functionalities to be used independently or simultaneously.

So as to attain the objectives mentioned above, the splint for moving a lower limb is of the type including a base bearing an articulated structure composed of a crural cradle or segment joined to one extremity of the base and a tibial segment or cradle linked to the crural cradle by a hinge pin orthogonal to the direction of a rail defined by the base for guiding the tibial cradle, a motor device inserted between the base and the articulated structure so as to move the tibial segment relative to the rail along an alternative rectilinear movement and a foot-rest adapted at the end of the tibial cradle or segment opposite the crural cradle, said splint being characterised in that according to the invention said foot-rest is mounted on the tibial cradle by means of at least one slide with the insertion of an elastic recall device continuously tending to bring the foot-rest back into a least extended position relative to the tibial cradle.

Various other characteristics are given in the following description with reference to the accompanying drawings given by way of examples of embodiments and modes for implementing the invention.

Figure 1 is a diagrammatic perspective view of a splint for moving lower limbs.

Figure 2 is an explanatory diagram showing the basic problem the invention seeks to resolve.

Figure 3 is a partial front cutaway view on larger scale of details of the embodiment of the splint according to figure 1.

Figure 4 is a partial front cutaway view on larger scale illustrating an embodiment variant.

Figure 5 is a partial pulled up front cutaway view showing again on larger scale another embodiment of the means of the invention.

Figure 1 shows a splint for passively moving a lower limb, either a left or right limb given the fact that the splint shown is of a symmetrical construction.

The splint includes a base 1 intended to rest on a suitable type of support plane 2 advantageously constituted by the padding of bed linn.

The base I comprises a proximal portion 3 with which it supports an articulated structure 4 composed of a crural cradle or segment 5 connected by a joint 6 to the proximal portion 3. The crural segment 5 is composed of two members or similar elements 7 possibly interconnected by a brace and indeed be equipped with a flexible element for supporting the thigh of a lower limb for example, such as a hammock 8 made of a suitable material.

The structure 4 is also composed of a tibia] segment 9 which is articulated in the extension of the crural segment 5 by means of journals or pivots 10 whi ch collectively define a pivoting axis x-x' orthogonal to the general direction of the base 1.

The tibia[ segment 9 is constituted by two members or similar elements I11 possibly .connected by a transversal brace 12 and able also to be equipped with a flexible suppo rt padding, such as a hammock 13.

The end portion of the tibial segment 9 opposite the pivots 10 bears a foot-rest 14 constituted by a support 15, possibly able to be adjusted along an axis y-y' approximately parallel to the axis The support 15 bears a bearing plate 16 able to be adjusted in the two directions of the arrow fl by means of all suitable known means of the technique for introducing for example a pivot or a tightening knob. The bearing plate 16 bears a sole 17, possibly adjustable in the two directions of the arrow U2 and preferably embodied in the shape of an pen shell so as to allow its placing and the support of the foot of the lower limb to be re-educated.

Finally, the structure 4 is raised to the level of the tibial segment 9 by a carriage 18 controlled by a guiding channel 19 materialised by the base 1 along a rectilinear direction orthogonal to the axis x-x'.

The structure 4 is associated with motorisation means, such as those denoted by the general reference 20, for acting on the structure so as to control the carriage 18 to move alternately in a rectilinear direction on thc channel 19 so as to move the structure 4- from a complete extension in a bending movement and vice versa as known by cxperts in this particular field. The rmotorisation means 20, which can be c ontrollcd from a remote contToI box 21, can be adapted on one of the pivots 10 or even be placed in relation with the carriage 18 by then introducing an appropriate transmission.

The choice of these miotorisation means is not covered by thc invention and are accessible to experts in this field.

A mobilisation splint of the type mentioned above generally or at least frequcntly introduces when said splint is placed a situation of the type shown on figure 2 in which via to sliding, an oversight or impossibility concerning placing, the joint 6 between the crural segment and the base 1 does not coincide with the coxofemoral joint 22 of the limb 23 to be re-educatcd.

This situation also shows the presence of a crural segment 4 length differing from the length of the articular femoral segment of the limb 23 so that two types of shifts can occur between the axes 6 and 22, namely a shift N with respect to the plane of the base and a shift n inside a plane perpendicular to this plane.

This absence of coincidence is automatically expressed during an extending/bending movement via paths ti and t2 which differ for the axis x-x' and for the knee 24 with which this axis x-x' shall normally corresponid.

The gap between the paths t I and Q2 may vary, but in all cases is expressed by nonoptimum functional conditions.

Figure 2 clearly shows that the shift of the paths ti and Q2 results that in an extended position tbe path of the knee t2 is situated behind the path ti with respect to the distal extremity of the base and that accordingly the foot-rest 17 progressively moves forwards with respect to the foot which is no longer placed in support or, if applicable, supported.

The object of the invention is to offer means to compensate this progressive difference during the path so as to re-establish on the entire path a support between the foot and the foot-rest 17 irrespective of the difference between the paths ti and tC.

To this end and as shown on figure 3, at least one rod 30 and preferably two are mounted on the support 15 bearing the bearing plate 16 and the foot-rest 17, said rods bein placed so as to be able to slide telescopically inside at least one and preferably two members I I which in this respect are at least partly tubular. Each rod 30 is provided with an extreme collar 31 and slides in a tubular stopper 32 closing the distal extremity of the member I I so as to constitute a sliding bearing for the rod 30. The member I1I delimits a dummy bore which along with the rod 30 defines an annular gap 33 for receiving an elastic recall element 34 constituting a device continuously tending to act on the rod 30 so as to stress it in the direction of the arrow B3 so as to give it a position of least extension relative to ithe member 11. This least extended position is for example, but not exclusively, determined by the bringing into support the collar 31 on the bottom of the bore of the member 11. The elastic elements 34 arc advantageously constituted by hclical springs 1 0 placed under compression stress.

The stopper 32 can appear in the form of a smooth bearing or indeed a ball bush and is adapted onto the extremity of the member 11I so as to be advantageously movable for facilitating the mounting of the rod 30 and that of the spring 34.

It can be seen on figure 2 that adapting the splint to the limb 23 to be moved is made in an initial pre-adjustment bending position of for example at 900 in which there may be pseudo coincidence between the axis x-x' and the axis 24 of the knee. In this position, the effective length between the axis x-x' and the axis y-y' is adjusted for example by means of the position of thc support 15 on the rods 30 so that it is less than the length of the tibial segment 25 of the lower limb 23 and thus that in this position the foot-rest 17 is stressed to partially extend against the opposing action of the spring(s) 34 which are subjected to a stress greater than the one they undergo in thc least extended position as referred to earlier.

During the extension movement stressing the articulated structure in the direction of the arrow K4 the shift between the paths ti and that of t2 shows that t2 followed by the knee 24 tends to take up the delay with respect to that of tI followed by the axis x-x'.

Normnally in this situation, this results in a removal of the foot with respect to the foot-rest 17 so that the third initially sought-after support point is thinned down or even eliminated.

However, according to the invention the delay taken up by the path t2 provokes a backward movement of the foot followed faithfuly by the foot-rest 17 stressed when retracting during least extension by the spring(s) 34 whose original prestressing has been accentuated by the adjustment carried out as mentioned previously.

Figure 4 shows that it can be advantageous to have the stopper 32 in the form of a smooth bearingc or ball bearing, for example, able to be adjusted by means of threading/tapping, in the direction of the arrow f5 with respect to the member 11.

When desirable, this adjustment makes it possible to modify the recall force of the spring 34 and consider for example using the means of the invention so as to offer a possibility of active moving to be deliberately undertakcen by the patient so as to provoke the backward movement of the foot-rest 17 against the antagonistic action of the spring(s) 34 so as to stress the muscular function of the quadriceps.

This possibility is more readily available when it is possible to adjust the nominal length of the tibial segment 9 by means of the fixing and mounting means of the support on the rods 30, for example with the aid of tightening buttons Figure 4 shows that in certain cases, it may be advantageous to provi de a possibility of adjusting the least extended abutment position other than bringing the support of the collar 31 on the bottom of the bore of the member 11.

.IThis adjustment possibility shown on figure 4 can be made by a nut 36 formed for example of two half-collars assembled together by an elastically ductile hoop 37 stressing the half-collars to occupy a tightening state on the rod 30 in an axial immobilisation position in which each half-collar is engaged by a rib 38 in notches 39 of a set axially shown by the rod An embodiment variant of this device is shown on figure 5 in which the tubular proximal portion of the member I1I has one or several sets of holes 40 for engaging a pin 41 on which the collar 3 1 takes support.

Apart from the two functions able to be taken up by the means described above, it ought to be mentioned that the possibility of telescopic sliding with elastic recall given to the foot-rest 17 offers an automatic adjustment possibility to the length of the tibial segment of the limb 23 to be re-educated without it being necessary to have the buttons carry out any specific adjustment when in default this nominal length adjustment is selected below the length of said segment.

Figure 1 shows a simplified embodiment variant of the means of the invention.

According to this variant, each rod 30-member 11 unit is associated with an elastic recall device constituted by a spring 34 which is inserted under prior stretching stress between an anchorage ring 42 borne by the rod 30, indeed the support 15, and a bar 43 having holes borne by the member 11 close to the bearing journal The elements 34 can be all suitable types of springs and in particular clastic cables of the type of those commercially known under the name SANDOW. One variant can also consist of replacing the helical springs of figure 3 with elastic cables housed inside the rods which are then tubular and so that one of the extremities is integral with said rod and the other linked to the tube 11.

These simple means taking up less space can be adapted as desired by the user and offer the same functional characteristics as those described previously.

INDUSTRIAL APPLICATION: The invention can be preferably applied for splints for re-educating the knee.

Claims (11)

1. Splint for moving a lower limb and of the type including a base bearing an articulated structure composed of a crural cradle or segment joined to one extremity of the base, and a tibial segment or cradle linked to the crural cradle by a hinge pin orthogonal to the direction of a rail defined by the base for guiding the tibial cradle, a motorisation device inserted between the base and the articulated structure so as to move the tibial segment relative to the rail according to an alternative rectilinear movement and a foot-rest adapted at the end of the tibial cradle or segment opposite the crural cradle, characterised in that said foot-rest is mounted on the tibial cradle by means of at lease one slide with the insertion of an elastic return device continuously tending to bring the foot-rest back into a least extension position relative to the tibial cradle.

2. Splint according to claim 1, characterised in that the elastic return device is mounted on externally.

3. Splint according to claim 1, characterised in that the elastic return device is included in the slide.

4. Splint according to any one of claims 1 to 3, characterised in that the elastic return device is associated with an element for adjusting its return force.

5. Splint according to any one of claims 1 to 4, characterised in that the elastic return device is completed by a member for adjusting the least extension abutment position of the foot-rest. ooooo

6. Splint according to any one of claims 3 to characterised in that the elastic return device is constituted by a helical spring fitted concentrically on a H-\Pcabral\Keep\speci\63450.99.doc 15/01/04 10 rod mounted telescopically in a member at least at the tubular portion of the tibial cradle, said spring being mounted under stress between a collar of the rod and a tubular plug adapted in such a way on the member so as to form a sliding bearing for the rod.

7. Splint according to claim 6, characterised in that the bearing plug can have its axial position adjusted with respect to the member so as to constitute the means for adjusting the force of the spring.

8. Splint according to claim 5, characterised in that the element for adjusting the abutment position is constituted by an adjustable abutment fitted between the rod and the member.

9. Splint according to claim 8, characterised in that the adjustable abutment is constituted by a pin traversing one of a series of holes made in the member so as to constitute a support for the collar of the rod.

Splint according to claim 8, characterised in that the adjustable abutment is constituted by an elastic opening nut able to be fitted on, a series of notches or 25 similar elements.

11. A splint substantially as hereinbefore described with reference to the accompanying drawings. Dated this 15th day of January 2004 S* SMITH NEPHEW KINETEC By their Patent Attorneys GRIFFITH HACK 35 Fellows Institute of Patent and Trade Mark Attorneys of Australia *ooo \\melbfiles\home$\Pcabral\Keep\speci\63450.99.doc 15/01/04