WO1995010240A1

WO1995010240A1 - A device for the mutual positioning of bone sections

Info

Publication number: WO1995010240A1
Application number: PCT/NL1994/000249
Authority: WO
Inventors: Gerrit Johannes Termaten
Original assignee: Spangenberg, Theo
Priority date: 1993-10-08
Filing date: 1994-10-10
Publication date: 1995-04-20
Also published as: NL9301738A

Abstract

A device adapted for mutually positioning bone sections, comprising a support bar to be applied laterally along the bone sections to be mutually positioned, at least two pin-holding blocks which are slidably and lockably mounted thereon, said blocks carrying pivotally adjustable clamping supports that have a number of seats for bone pins and cooperate with a clamping means to be fixed thereon so as to lock the pins within the respective seats. According to the invention the bone pin holding blocks have, at each of two opposite sides, a projecting portion for the attachment of a clamping support, whereby the two clamping supports may be fixed in such relative positions that the respective seat planes for the bone pins enclose an acute angle. This enables the bone pins - that projects on both sides from a bone pin holding block - to be placed in a V-configuration and thus to obtain a rigid structure.

Description

Short title: A device for the mutual positioning of bone sections.

The invention relates to a device adapted for mutually positioning bone sections, comprising a support bar to be applied laterally along the bone sections to be mutually positioned, at least two pin- holding blocks which are slidably and lockably mounted thereon, said blocks carrying pivotally adjustable clamping supports that have a number of seats for bone pins and cooperate with a clamping means to be fixed thereon so as to lock the pins within the respective seats.

Such devices, in professional circles called "external fixators", are used as an aid during the process of healing of bone fractures and cure already known in various embodiments.

As an example of a well-known device of the type defined herein-above, reference is made to European patent application 0374093 (A1), and more particularly to the embodiment according to fig. 6-8 therein.

With this well-known device the clamping supports are provided on one side of the bone pin holding blocks only.

At each bone pin holding block all of the bone pins held by the respective clamping support are positioned in one line one after the other and in a plane that is spaced from the axis of the support bar.

With such a constructicn loading of the healing bone will result in oppositely directed shearing forces on the outer bone pins of each group of bone pins carried by a clamping support. Intermediate bone pins, if any, such as the central bone pin in case of a usual group of three bone pins, are merely functioning as a pivot for the highest loaded outer pins.

With this well-known device the whole assembly including the bone pins, the support bar and the holding blocks with the clamping supports thereon is far from rigid, so that the bone positioning effect of it is limited, whereas the capability of the bone to be loaded during the healing process is limited as well.

Furthermore this well-known device has the disadvantage that its adjustability is limited, whereas on the other hand the number of parts is relatively large and the construction is rather complex. Far with the well-known device the part that extends from the holding block is constituted by a cylindrical projection around which a split annular part is rotatably and fixably mounted. This annular part carries an arcuate support means the axis of which intersects that of the cylindrical projection at right angles. The clamping support far the bone ins has a concave-cylindrical supporting surface corres ponding to the arcuate support means.

The clamping means by means of which the bone pins are fixed onto the clamping support are tightened by means of a central clamping srew that extends through a slot in the arcuate support means and also serves to clamp the clamping means onto the support means. Consequently upon locking of the bone pins on the clamping supports the clamping support and bone pin assembly may be adjusted in only one direction yet, viz. in the sense of an angular movement about the cylindrical projection.

The use of two such devices, at opposite sides of the fractured bone, could result in a more rigid structure, but is not always possible without much discomfort for the patient; moreover such use would be costly, while the positioning and the fixing of the clamping supports would provide a still larger problem.

GB-A-538600 discloses a structure, in which two aligned bone pin holding blocks are supported by two support bars extending on either sides of the holding blocks. With this structure the individual pin holding blocks are supported more reliably. Moreover the connections to the support bars are constituted by ball joints due to which a simpler construction is obtained and the support bars may be applied rather easily.

The use of more than one support bar, however, has the drawback, that the access to the fractured bone to be healed, e.g. for the purpose of taking an X-ray, is limited by such use, while the torsional strength is unsatisfactory.

DE-A-27 18 515 discloses a structure having a single support bar with holding blocks mounted thereon in a slidable and lockable manner, said holding blocks having on one side a spherical projection that engages a correspondingly shaped seat provided on a multiple pin bone holding block.

Furthermore FR-A-2.536.984 discloses a structure with which a holding block is slidably and lockably mounted on a single support bar and is adapted, at two opposite sides, to receive and hold an auxiliary part that extends transversely relative to the support bar, a support being slidably mounted on said auxiliary part and carrying a bone pin clamp. With this one might have the holding block support two bone pins which are mutually positioned in "V"-fashion.

Due to the relatively large number of parts this well-known device is not only structurally complex but also very laborous and awkward in use, as the connection between the bone pins and th4e support bar requires a relatively large number of individual adjustments to be made. Moreover this device does not allow placing more that one bone pin (e.g. positioned lengthwise of the support bar and in one row one behind the other) in a bone pin clamp.

It is an object of the invention to provide such an improvement that with a single device (i.e. to be applied along one side of the fractured bone) a rigid bridging structure along the fractured bone may be obtained, which is capable of withstanding relatively high loads that might be applied on the bone during healing.

According to the invention this aim is achieved in that the bone pin holding blocks have, at each of two opposite sides, a projecting portion of a spherical shape for the attachment of a clamping support, the latter having a correspondingly semi-spherical seat for said projection and is adapted to be locked on said projection by means of a clamping strap that also has a semi-spherical seat, thereby allowing the two clamping supports to be fixed in such relative positions that the respective seat planes for the bone pins enclose an acute angle.

In this way the bone pins held on both sides of the supporting bar by the respective clamping supports and extending with their free ends into the respective bone portion, will become positioned in V-fashion. This leads to a rigid, space frame-like connection between bone and fixator, in which all of the bone pins are subjected substantially equally loads and may have a correspondingly reduced diameter. Due to the universally adjustable character of the connection between the holding blocks and the support bar the whole assembly may be applied by a few simple exercises.

At first the pins, which are positioned on one side of the support bar and have already been intnaduced into the bone sections to be positioned relative to one another, may be fixed within the respective clamping supports, after which the clamping supports so positioned relative to the respective bone sections, are still permitted to pivot relative to the respective holding blocks so as to determine and then secure the optimal position of the supporting bar.

The invention will be hereinafter further explained, by way of example, with reference to the accompanying drawings.

Fig. 1 is a perspective view of a device according to this invention which is applied along a bone with a fracture to be healed; fig. 2 is a side view of the device of fig. 1 and fig. 3 is a cross-sectional view along the line III-III of fig. 2.

In fig. 1 a (human) bone is indicated at 1. The bone portions 1a and 1b on both sides of a fracture 2 must be kept in position one to another during the healing process by means of the device of this invention. This device comprises a support and guide bar 3 made of a material that is preferably impermeable to X-rays or similar radiation. A number (two in the example shown) of bone pin helding blocks 4 is slidably mounted on said support bar and may be fixed thereon by means of clamping screws 4a. A polygonal cross-sectional shape of the supporting bar 3 and of the corresponding bar receiving bores in the holding blocks 4 prevents the holding blocks 4 from rotation relative to the supporting bar 3.

A projection 5 is provided on each of two opposite longitudinal sides of the bone pin holding blocks 4, said projection consisting of a connecting neck portion 5a and a spherically shaped end portion 5b that is flattened at its free end.

In the example shown in the drawing the projections extending in opposite directions from each block 4 have coinciding axes, whereas block and projections are formed in one piece.

A bone pin clamping support 6 is mounted for universal pivotal adjustment on the spherical end portion 5b of each projection 5. For this purpose each bone pin clamping support 6 is provided with a semi-spherical seat for the spherical-shaped end portion of the respective projection 5 on which it may be fixedly clamped - by means of clamping screws 8 - with a clamp 7 that is provided with a concave-spherical clamping surface.

Furthermore each of the clamping supports 6 cooperates with an outer clamping plate 9.

The opposite, substantially flat surfaces 6a and 9a of the clamping supports 6 and clamping plates 9 cooperate to fixedly clamp the bane pins (which are indicated at A and B in the drawing) therebetween. In the example shown the surfaces 9a of the clamping plates 9 are provided with (four) mutually parallel V-shaped seats 10 for the bone pins A and B respectively.

In fig. 2 and 3, showing the clamping supports 6 in a central position (i.e. in a mid position within the total angular adjustability range) relative to the respective projections 5, the surfaces 6a, functioning as bearing surface far the bone pins A and B respec tively, are positioned at an angle with respect to the axis of the respective projections 5, in such a way, that the surfaces 6a of the clamping supports 6 on either side of a block 4 converge in a direction turned away from the clamping screws 8, thereby enclosing an angle (vide fig. 3).

The use of the device described hereinabove will new be further explained by reference to the example shown in fig. 1.

At first, the pins A shown in the background in fig. 1, are introduced into the bone sections 1a and 1b respectively in a manner known per se, e.g. with the aid of a drilling template. The upper two pins A need not to be positioned in one plane with the lower two pins A. A clamping support 6 is then placed on each of the upper and lower pairs of pins A and fixedly clamped onto said pins by the respective clamping plate 9 and by means of screws 11.

Thereafter - while keeping the bone sections 1a and 1b in the desired mutual position - the supporting bar 3, with the two bone pin holding blocks 4 carried loosely slidably thereon, is applied in such a way that the respective two projections 5 are received with their spherical end portions 5b into the semi-spherical seats of the respective clamping supports 6. The clamping supports 6 are then fixed relative to the respective holding blocks 4 by means of the clamps 7 and the clamping screws 8.

After this the bone pins B shown in the foreground in fig. 1, are introduced, in planes which enclose an angle (e.g. the angle in fig. 3) with those of the bone pins A positioned in the background.

The clamping supports in the foreground may thereby fixed an the respective ball ends 5b in a position corresponding with the desired bone pin direction so as to serve as a support for a drilling template

(not further shown in the drawing).

In this way, as is clearly shown in fig. 1, an assembly of two x two bone pins is applied in the upper bone section 1a as well as in the lower bone section 1b, wherein the bone pins A and B in each assembly are crossing each other within the bone under an angle (α).

The pairs of pins A and B are positioned slightly offset relative to one another in the longitudinal direction of the bone. Each bone pin holding block forms with the associated clamping supports and the four pins clampingly held thereby a space frame-like rigid structure, the two structures being interconnected by the support bar 3 which is rigid in itself. The support bar 3 is thereby positioned at a relati vely small distance from the bone to be healed.

Finally fig. 2 shows a tensioning device 20, which is applied onto the (upper) end portion of the support bar 3. This tensioning device comprises an interiorly threaded tensioning sleeve 21 having a turning handle 24, said sleeve being screwed onto a correspondingly exteriorly threaded inner sleeve 23, the latter being adapted to be fixed in the desired longitudinal position onto the support 3 by means of a clamping collar and -screw 22.

A circumferential groove 21a is provided at the end of the tensioning sleeve 21 that is turned away from the clamping collar 22. This groove is engaged by a cam portion (not shown in the drawing) that extends through a certain arc length radially inwardly from a block 25, that may be attached to the (upper) end face of the upper holding block 4 by means of a clamping screw 25a (vide also fig. 3). A turning movement of the tensioning sleeve 21, which causes the cam portion to slide within the circumferential groove of the block 25, permits the upper bone pin holding block 4 (which is not fixedly clamped onto the bar 3) to be moved towards the lower holding block 4 (which is fixedly clamped onto the bar 3) and thereby place the fracture under (a gradually increased) compression. In the opposite sense, an increase of the spacing between the blocks 4 enables to put a bone under tension.

Claims

1. A device adapted for mutually positioning bone sections, comprising a support bar to be applied laterally along the bone sections to be mutually positioned, at least two pin-holding blocks which are slidably and lockably mounted thereon, said blocks carrying pivotally adjustable clamping supports that have a number of seats for bone pins and cooperate with a clamping means to be fixed thereon so as to lock the pins within the respective seats, characterized in that the bone pin holding blocks have, at each of two opposite sides, a projecting portion of a spherical shape for the attachment of a clamping support, the latter having a correspondingly semi-spherical seat for said projection and is adapted to be locked on said projection by means of a clamping strap that also has a semi-spherical seat, thereby allowing the two clamping supports to be fixed in such relative positions that the respective seat planes for the bone pins enclose an acute angle.

2. A device according to claim 1, characterized in that the pin supporting surfaces of the clamping supports - in a central position of the latter on the respective projections - enclose an angle

3. A device according to claims 1-2, characterized in that the receiving bore for the support bar is excentrically positioned in said holding block.

4. A device according to claim 3, characterized in that a mounting bare for fastening a longitudinally extending spherical projection is provided in at least one end face of the holding block.