GB2258155A - External axial splint with damping means - Google Patents

Description

223;i 33 EXTERNAL AXIAL SPLINT This invention relates to an external axial

splint.

It is known that external splints can be used for the repair of fractures. In this respect Italian Patent No. 1,110,581, granted on the 23rd December 1985, is known and describes an external splint having high stability with the feature that it comprises a central body consisting of two members which are telescopically and selectively coupled together and associated with two screw clamps and which can be connected to a removable compress or- extender and means for securing the said two members and clamps in position.

This splint has been found to have a disadvantage: with it the application of force is of the "all or nothing" type, i.e. it is not possible to control the amount of force applied.

By the application of force is meant a mechanical stimulus applied to the fracture callus or the newly formed callus which assists optimal reforming of the bony callus.

In the case of known splints, the surgeon applies the force by releasing the telescopic movement of the splint for a period of time at his discretion. If the force is applied too early the surgeon runs the risk of applying undesired compression to the point of fracture with consequent misalignment and/or shortening of the stumps of the fractured bone, or with consequently undesired shortening of the limb which had previously been subjected to elongation.

An object of the invention is to at least minimise disadvantage mentioned by providing an external axial splint which is capable of varying the position and therefore the space between the ends of the fracture in a controlled way during a predetermined interval.

A further object is to provide an external axial splint which can be used to apply compression or extension or a mixed condition in a controlled way, even at a very early stage, without having to wait for the bony callus to become sufficiently solid, this early application of force obviously aiding optimum formation of the bony callus when the callus is compressed between very specific limits. Faster repair is achieved by subjecting the fractured bone to axial low intensity high frequency stimuli at an early stage.

Another object is to provide an external axial splint which is structurally simple, takes up a minimum amount of space, is light and is easy to use.

According to the present invention there is provided an external axial splint comprising a central rod-shaped body incorporating a first and a second rigid member which can be slidably coupled together in an axial direction in the vicinity of a terminal portion thereof, a bone screw clamp which can be secured to the other terminal portion of each rigid member, a removable compress or-ex tender which can be coupled externally to said rigid members and means for securing said two rigid members and said clamps in position, and is characterised in that it includes at least one elastically deformable member attached to one of the two rigid members of the central body and in contact with the other of said two rigid members to provide a damping effect between them.

The principal advantage offered by the arrangement proposed, which derives from many controlled applications in the laboratoryv lies in the fact that with the splint according to the invention it is possible to ensure, before the splint is applied, that the relative displacements of the two telescopic members comprising the body of the splint itself will not exceed for example a fraction of a millimetre, thus eliminating from the outset the risk of excessive compression of. a not yet sufficiently solid bony callus. Thus force may be applied early, very soon after formation of the bony callus has begun, thus encouraging rapid mending in comparison with similar cases where the force is applied a few weeks later after awaiting solidification of the bony callus.

A second advantage is provided by the fact that the structure of the central body, in particular in the embodiment having plate-like members, called "slides", hinged by connecting rods to one of comprising the central body jamming as one member of the upon the other as the force is also means of two pairs of the two rigid members of the splint prevents said central body slides applied, by the use of a structure of the said central body which is based on a hinged quadrilateral.

The present invention will be further illustrated, by way of example, with reference to the accompanying drawings, in which:

Fig. 1 is a lateral view of a splint according to the invention having partly interrupted splints applied to an interrupted long bone, partly as seen and partly in cross-section.

Figs. 2 and 3 show the functioning of a splint diagrammatically: in Fig. 2 with the reference member supported by the elastically deformable member and in Fig. 3 with the reference member positioned in such a way as to interact with the compressible member; Fig. 4 is a cross-section taken along the plane indicated by IV-IV in Fig. 2.

Fig. 5 is a lateral view in partial crosssection of a second embodiment of the invention; Fig. 6 is a view from below of an open annular spacer in which the elastically compressible members have been omitted for the purposes of illustration.

Fig. 7 is a view from below of the spacer of Fig. 6 in the closed position.

Figs 8 and 9 are two lateral views of the spacer of Fig. 6; Fig. 10 is a perspective. view of half -ring with a guide bar for the annular spacer of Fig. 6; Figs. 11 and 12 are two views in lateral elevation of a bone screw clamp according to the invention in position for use as a splint; Fig. 13 and 14 are two views in lateral elevation of the clamp of Figs. 11 and 12, in position for use as an assembly jig.

Figs. 15 is a lateral view in partial crosssection of a preferred embodiment of a central member according to the invention; and Fig. 16 illustrates the lower rigid member of the central body in the foregoing figure with the reference member supported by the elastically deformable member.

Bearing in mind that the figures are to variable scales and that the individual reference numerals correspond to identical or equivalent partsy Fig. 1 shows an external axial splint 1 comprising a central body 2 comprising a first member 3 and a second member 4 of substantially Lshape arranged with the larger limbs parallel and facing each other.

A first screw clamp 9 and a second screw clamp 10 are associated with the first and the second member at the end through ball joints 7 and 8.

Holes 21 and 22 for the temporary connection of a compressor-extender, which is not illustrated in the drawing. are also provided at the ends of the first and the second member.

As illustrated in Figs, 15 and 16, a reference member 11, also called a slide, is associated with a first member 3 and hinged as a hinged quadrilateral: at the ends slide 11 is in fact transversely hinged by means of first pins 12a and 12b to a pair of brackets 13 and 13' which are in turn idly hinged at their other end by means of second pins 14a and 14b transversely to the underlying first member 3.

The brackets are shaped in such a way as to allow slide 11 to move in two directions axial to the splint, but they are not allowed movement in the direction of the smaller limb of second member 4 beyond the condition in which this is perpendicular with respect to the larger limb of first member 3.

Means for securing in relative position comprising a first dowel 16 and a second dowel 17 are associated with the first and the second member. The first dowel is rotatably associated with a counterthreaded seat made in the larger limb of first member 3 in an axis perpendicular to that of the splint, the shank of the first dowel abutting against overlying reference member 11. The said first dowel 16 thus selectively secures reference member 11 with respect to first rigid member 3. The shank of second dowel 17 is rotatably associated with a counterthreaded seat 17' made in reference member 11 in a direction perpendicular to the larger limb of second member 4, this shank also being capable of being positioned in an eyelet 18 provided longitudinally to the larger limb of second member 4. Said second dowel 17 instead selectively immobilises reference member 11 with respect to second rigid member 4. By thus acting on the said first and second dowels it is possible to:

a) immobilise sliding of first rigid member 3 with respect to second rigid member 4, anchoring both said rigid members 3 and 4 to reference member 11, b) removably immobilise reference member 11 to first rigid member 3 by means of dowel 16 while allowing relative displacement between the said first and second rigid members. Between the smaller limb of first member 3 and the opposing end of slide 11 there is elastically compressible member 19 consisting of a block of silicone-based material which can be forced between them. This elastically compressible member acts as an opposing spring, i.e. when the splint is not subjected to the load due for example to the patient's body weight it moves reference member 11 backwards with respect to the smaller limb of rigid member 3. The functioning of the said elastically compressible member is diagrammatically illustrated in Figs 2 and 3 which exaggerate the relative movements of the various parts forming the central body of the splint according to the invention. In Fig. 2 this is in the resting position, while in Fig. 3 it is compressed by reference member 11.

The elastically compressible member 19, together with said dowell6, is capable of determining with continuity the interval within which it is desired that the axial displacement of said reference member with respect to first member 3 should be contained. Use of the splint in fact provides that once second dowel 17 has been locked to slide 11 second member 4 is positioned in such a way that the slide is only supported or is lightly or wholly compressed against the opposing silicone-based block. This method of operation makes it possible to achieve a situation of compression or extension or a mixed situation as a result of the elastic compressibility of said block 19.

In particular, a compression situation arises when slide 11, which initially bears against the elastically compressible member and is fixed in that position to first member 3 by means of dial 16 and second member 4 by means of dial 17, is released following slackening of said dial 17. In such a situation if the patient walks or in any way uses the fractured limb the weight of the patient's body, or the load applied to the limb, brings first and second members 3 and 4 closer together tending to reduce the length of the central body of the splint and therefore the distance between the ends of the fractured bone, thus generating compression in the forming bony callus.

An extension situation, which occurs cyclically for example while the patient is walking, arises when slide 11 is initially fixed to the said first and second members 3 and 4 with the elastically compressible member completely compressed. When subsequently dowel 17 is slackened the compressible member extends elastically returning to its normal resting dimensions, separating the ends of the fractured bone by a predetermined amount depending on the dimensions and deformability characteristics of the said compressible member. When the patient then places a load on the fractured bone, e.g. in the course of walking, the ends of the bone are brought together so as to fully recompress the said member, thus cancelling out the extension effect.

Finally, a mixed compression and extension situation can be achieved by initially compressing the said elastically compressible member only partially. In this case when dowel 17 is relaxed, if the fractured bone is not subjected to a load, elastic return of the said member separates the ends of the bone placing the bony callus under tension, while if the patient subjects the fractured bone to a load its ends are brought together by a predetermined amount and the said bony callus is thus subjected to compression.

This therefore provides a certain amount of play which allows the two stumps of fractured bone to vary the relative distance corresponding to the fracture, continuously and within a predetermined range, thus aiding reformation of the bony callus and thus optimum knitting of the fracture.

With reference to Figs. 5 to 10 an alternative embodiment of the invention compressing an external axial splint is illustrated which comprises the central body 2' consisting of a first member 3' and a second member 4' each having respectively a first limb 5 and a second limb 6 which are telescopically coupled together.

A first pin-bearing clamp 9 and a second pinbearing clamp 10 are associated with the ends of the first and the second members by means of ball joints 7 and 8.

Holes 21 and 22 for the temporary connection of a compress or/ex tender, which are not illustrated in the drawing, are also present at the ends of the first and second members. The splint compresses locking means between the first and the second member compressing a channel 23 made longitudinally to first limb 5 against which there abuts a screw 24 associated with second limb 6.

Annular spacer 25 is removably and selectively positioned coaxiallY with first limb 5 of a first member 3'.

The latter spacer comprises a first half ring 26 and a second half ring 27 which has a fork 28 and a first appendage 29 at one end respectively, both drilled along an axis perpendicular to upper surfaces 30a and 30b and lower surfaces 31a and 31b thereof, this fork and the first appendage being rotatably associatable by means of a hinge pin 32.

The other ends of the first and second half rings have recesses 33 and 34 which are complementary to each other to give an interlocking coupling and threaded holes, seats for a counterthreaded dowel 35 along the same radial axis.

In order to prevent rotation of ring 25, it is arranged that once dowel 35 has been screwed in its terminal portion abuts against channel 23 in first limb 5; this also makes it possible to define the desired position of the annular spacer with respect to the first and the second limbs.

A cavity, indicated by the numeral 36a and 36b respectively, which has an arcuate shape in plan and extends in the direction of lower surfaces 31a and 31b of the said half rings, in a frustoconical conformation such as to define an end. indicated by the numerals 37a and 37b respectively, of surface area greater than the excess surface area of the said cavity is also made perpendicular to upper surfaces 30a and 30b in each of half rings 26 and 27.

Two pairs of re-entrants' 38a, 38b and 39a, 39b are provided on the perimetral edge of the latter two in positions which are diametrically opposite to each other and equidistant from the ends thereof.

An elastically compressible member can be positioned between each of the recesses 36a and 36b. In the embodiments illustrated in Figs. 8 and 9 these A members are two in number and are indicated by the numeral 40 and 41. Each of these advantageously consists of a cylindrical silicone cord which can be forced into the cavities and projects above the plane of lower surfaces 31a and 31b.

Finally, annular spacer 25 has an external diameter which is preferably slightly greater than that of second member 6: a bar 42 which projects axially to immobilising ring 25 in the direction of second limb 6 beneath is made integral with the lateral surface of first half ring 26.

An eyelet 33 is located longitudinally to bar 42 and a screw 44 which projects radially to second limb 6 can be positioned therein when immobilising ring 25 is closed.

Use of the annular spacer thus means that the latter will be coaxially locked against first limb 5 by screwing in dowel 35 until it abuts against channel 23 in first limb 5.

Securing may be achieved by the angular spacer merely supported against or slightly or wholly compressed against the underlying end of second limb 6; this method of operation makes it possible to achieve a compression or extension situation or a mixed situation as a result of the elastic compressibility of silicone cords 40 and 41 in a manner similar to that illustrated previously.

Figs 11 and 12 illustrate an alternative embodiment of a bone screw clamp which can be coupled to one end of each rigid member by means of a bayonet joint. Said clamp 9 comprises two jaws 45 and 46 which are secured together by means of pin 47 and eye 48 so as to be both hinged to open and close, and be adjustably spaced apart from each other by means of two locking screws, not illustrated, which can be screwed into threaded holes 49.

This allows clamp Vto perform a double role: Its first and main role is that of a bone screw clamp to be used in combination with either an axial splint of the type of that known in the cited patent or with a splint according to this invention; the second is to act as a guide screw clamp for use with an instrument or jig so as to guide positioning of the bone screws which are subsequently secured using the same clamp in accordance with the function previously illustrated. This makes it possible to have both the assembly jig and the axial splint in a single device with an obvious economic saving and a considerable reduction in the equipment necessary for the external splinting of fractured bones.

It is clear that in other embodiments of the invention the said tightening screws may be more than two in number, or only one.

Although not illustrated in the drawings, it is clear that the elastically deformable member, in addition to consisting of a block of elastic material, may consist of a prestressed or unprestressed string applied to the connecting rods of the slide. Also, the connecting rods of the said slide may be replaced by elastically deformable rod-like members encased within the rigid member on which the slide is mounted and encased or hinged to the said slide, the deformability of which members makes it possible for the slit to make the movements allowed by a hinged quadrilateral.

The splint obtained may be used for fractures of both the upper and lower limbs, its various components having dimensions appropriately corresponding to the various requirements. The materials used may also vary depending upon specific applications.

Claims (14)

1. An external axial splint comprising: a central rod-shaped body including a first and a second rigid member which are slidably coupled together in an axial direction in the vicinity of a terminal portion thereof, a bone screw clamp which can be secured to the other terminal portion of each rigid member, a removable compressor-extender which can be coupled externally to said rigid members, together with means for securing said two rigid members and said clamps in position, and characterised in that said splint includes at least one elastically deformable member attached to one of the two said rigid members of the central body and in contact with the other of said two rigid members to provide a damping action between them.

2. A splint as claimed in claim 1, characterised in that said splint includes a hinged reference member in the form of an articulated parallelogram at a overlappable end of one of the said rigid members in order to carry out limited relative displacements with respect thereto in order to allow force to be applied to the bony callus and characterised in that the said reference member is movably located between the said first and said second rigid members and in that securing means are provided to act on the said reference member to secure it removably to the rigid member to which it is hinged while allowing relative displacement between the first and the second rigid member.

3. A splint as claimed in claim 2, characterised in that between said reference member and the member to which it is hinged there is provided at least one - is - elastically deformable member which is capable of taking up the displacements of said reference member.

A splint as claimed in claim 2 or 3, characterised in that the or each elastically deformable member comprises at least one block of elastically compressible material which can be housed on the said rigid hinged member which is designed to provide continuous control of the substantially axial relative movement between said rigid members.

5. A splint as claimed in claim 2, 3 or 4 characterised in that the or each elastically deformable member consists of a silicone-based material.

6. A splint as claimed in any preceding claim, characterised in that t.ie or each elastically deformable member comprises at least one spring.

7. A splint as claimed in any one of claims 2 to 61 characterised in that said reference member compresses a plate-like member which is hinged by means of at least one pair of connected rods.

8. A splint as claimed in any one of claims 2 to 7, characterised in that said retaining means comprise a bolt which can be screwed into the member to which said reference member is hinged and butted against said reference member.

9. A splint as claimed in claim 1, characterised in that the said rigid members can be coupled telescopically together and characterised in that it comprises a spacer member which can be fixed to a telescopic member and butted against the other which acts as a support for the or deformable member.

each elastically

10. A splint as claimed in claim 9, characterised in that said spacer member is annular and canbe threaded onto the telescopic member of smaller diameter and has at least one seat for the or each elastically deformable member.

11. A splint as claimed in claim 101 characterised in that said annular spacer comprises a first half ring and a second half ring of which one end is articulated on a hinge pin, complementary recesses between them for mutual interlocking coupling at the other end and a threaded radial hole corresponding to said recesses to take a dowel for fixing one half ring to the other and the annular spacer to the telescopic member.

12. A splint as claimed in claim 10 or 11, characterised in that the said annular spacer comprises a projecting bar which projects axially and has a longitudinal eye within which a screw can be positioned for adjustable attachment of said spacer to the other telescopic members.

13. A splint as claimed in any one of claims 1 to 11, characterised in that said bone screw clamp which can be coupled to one end of each rigid member comprises two jaws linked together by means of a pin and eye so as to be mutually articulated so as to open and close and can be adjusted for distance between each other by means of at least one locking screw.

4 Z

14. An external axial splint with controlled movement substantially as hereinbefore described with reference to the accompanying drawings.